update single include file to v3.12.2

.bazelignore

@@ -1 +0,0 @@
-test

.bazeliskrc

@@ -1 +0,0 @@
-USE_BAZEL_VERSION=6.x

.bazelrc

@@ -1,16 +0,0 @@
-common --enable_bzlmod
-build --enable_platform_specific_config
-build --incompatible_enable_cc_toolchain_resolution
-build --enable_runfiles
-build --incompatible_strict_action_env
-
-# required for googletest
-build:linux --cxxopt=-std=c++17
-build:macos --cxxopt=-std=c++17
-
-common:ci --announce_rc
-common:ci --verbose_failures
-common:ci --keep_going
-test:ci --test_output=errors
-
-try-import %workspace%/user.bazelrc

.clang-format

@@ -2,11 +2,10 @@ BasedOnStyle: llvm
 ---
 AccessModifierOffset: -4
 AlignEscapedNewlines: DontAlign
-AllowShortBlocksOnASingleLine: Always
+AllowShortBlocksOnASingleLine: Empty
 AllowShortEnumsOnASingleLine: true
 AllowShortFunctionsOnASingleLine: Empty
 AllowShortIfStatementsOnASingleLine: WithoutElse
-AllowShortLambdasOnASingleLine: All
 AllowShortLoopsOnASingleLine: true
 AlwaysBreakTemplateDeclarations: Yes
 BreakBeforeBinaryOperators: NonAssignment
@@ -24,7 +23,6 @@ IncludeCategories:
     Priority: 4
   - Regex: '.*'
     Priority: 5
-IncludeIsMainRegex: "^$"
 IndentPPDirectives: AfterHash
 IndentWidth: 4
 KeepEmptyLinesAtTheStartOfBlocks: false

.clang-tidy

@@ -1,56 +0,0 @@
-Checks: >
-    bugprone-*,
-    clang-analyzer-*,
-    -clang-analyzer-optin.core.EnumCastOutOfRange,
-    concurrency-*,
-    cppcoreguidelines-*,
-    -cppcoreguidelines-owning-memory,
-    -cppcoreguidelines-pro-bounds-constant-array-index,
-    -cppcoreguidelines-pro-type-const-cast,
-    -cppcoreguidelines-pro-type-member-init,
-    -cppcoreguidelines-pro-type-reinterpret-cast,
-    -cppcoreguidelines-pro-type-union-access,
-    misc-*,
-    -misc-include-cleaner,
-    -misc-no-recursion,
-    modernize-*,
-    -modernize-use-trailing-return-type,
-    performance-*,
-    portability-*,
-    readability-*,
-    -readability-function-cognitive-complexity,
-    -readability-named-parameter,
-    -readability-uppercase-literal-suffix,
-CheckOptions:
-    - key: cppcoreguidelines-avoid-magic-numbers.IgnoreAllFloatingPointValues
-      value: true
-    - key: cppcoreguidelines-avoid-magic-numbers.IgnorePowersOf2IntegerValues
-      value: true
-    - key: cppcoreguidelines-rvalue-reference-param-not-moved.AllowPartialMove
-      value: true
-    - key: cppcoreguidelines-rvalue-reference-param-not-moved.IgnoreUnnamedParams
-      value: true
-    - key: cppcoreguidelines-special-member-functions.AllowMissingMoveFunctions
-      value: true
-    - key: cppcoreguidelines-special-member-functions.AllowMissingMoveFunctionsWhenCopyIsDeleted
-      value: true
-    - key: cppcoreguidelines-special-member-functions.AllowSoleDefaultDtor
-      value: true
-    - key: misc-non-private-member-variables-in-classes.IgnoreClassesWithAllMemberVariablesBeingPublic
-      value: true
-    - key: misc-non-private-member-variables-in-classes.IgnorePublicMemberVariables
-      value: true
-    - key: modernize-avoid-c-arrays.AllowStringArrays
-      value: true
-    - key: performance-enum-size.EnumIgnoreList
-      value: meta_traits
-    - key: readability-function-cognitive-complexity.IgnoreMacros
-      value: true
-    - key: readability-identifier-length.MinimumParameterNameLength
-      value: 2
-    - key: readability-identifier-length.MinimumVariableNameLength
-      value: 2
-    - key: readability-magic-numbers.IgnoreAllFloatingPointValues
-      value: true
-    - key: readability-magic-numbers.IgnorePowersOf2IntegerValues
-      value: true

.github/workflows/analyzer.yml

@@ -1,32 +1,33 @@
-name: tools
+name: analyzer
 
 on:
   push:
     branches:
-      - tools
+      - master
+      - wip
 
 jobs:
 
   iwyu:
-    timeout-minutes: 60
+    timeout-minutes: 30
 
     env:
-      IWYU: "0.23"
-      LLVM: "19"
+      IWYU: 0.19
+      LLVM: 15
 
     runs-on: ubuntu-latest
     continue-on-error: true
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v3
     - name: Install llvm/clang
       # see: https://apt.llvm.org/
       run: |
         wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
-        sudo add-apt-repository "deb http://apt.llvm.org/noble/ llvm-toolchain-noble-$LLVM main"
+        sudo add-apt-repository "deb http://apt.llvm.org/focal/ llvm-toolchain-focal-$LLVM main"
         sudo apt update
         sudo apt remove -y "llvm*"
-        sudo apt remove -y "libclang*"
+        sudo apt remove -y "libclang-dev*"
         sudo apt remove -y "clang*"
         sudo apt install -y llvm-$LLVM-dev
         sudo apt install -y libclang-$LLVM-dev
@@ -55,30 +56,6 @@ jobs:
               -DENTT_BUILD_EXAMPLE=ON \
               -DENTT_BUILD_LIB=ON \
               -DENTT_BUILD_SNAPSHOT=ON \
-              -DENTT_BUILD_TOOLS=ON \
               -DCMAKE_CXX_INCLUDE_WHAT_YOU_USE="include-what-you-use;-Xiwyu;--mapping_file=${GITHUB_WORKSPACE}/entt.imp;-Xiwyu;--no_fwd_decls;-Xiwyu;--verbose=1" \
               ..
         make -j4
-
-  clang-tidy:
-    timeout-minutes: 60
-
-    runs-on: ubuntu-latest
-    continue-on-error: true
-
-    steps:
-    - uses: actions/checkout@v4
-    - name: Compile tests
-      working-directory: build
-      env:
-        CXX: clang++
-      run: |
-        cmake -DENTT_BUILD_TESTING=ON \
-              -DENTT_BUILD_BENCHMARK=ON \
-              -DENTT_BUILD_EXAMPLE=ON \
-              -DENTT_BUILD_LIB=ON \
-              -DENTT_BUILD_SNAPSHOT=ON \
-              -DENTT_BUILD_TOOLS=ON \
-              -DENTT_USE_CLANG_TIDY=ON \
-              ..
-        make -j4

.github/workflows/bazel-release-archive.yml

@@ -1,23 +0,0 @@
-name: Bazel Release
-
-on:
-  release:
-    types: [published]
-
-jobs:
-  # A release archive is required for bzlmod
-  # See: https://blog.bazel.build/2023/02/15/github-archive-checksum.html
-  bazel-release-archive:
-    runs-on: ubuntu-latest
-    continue-on-error: true
-    permissions:
-      contents: write
-    steps:
-      - uses: actions/setup-go@v5
-      - run: go install github.com/bazelbuild/buildtools/buildozer@latest
-      - uses: actions/checkout@v4
-      - run: ./scripts/sync_bzlmod_version.sh
-      - run: git archive $GITHUB_REF -o "entt-${GITHUB_REF:10}.tar.gz"
-      - run: gh release upload ${GITHUB_REF:10} "entt-${GITHUB_REF:10}.tar.gz"
-        env:
-          GH_TOKEN: ${{ github.token }}

.github/workflows/bazel.yml

@@ -1,23 +0,0 @@
-name: bazel
-
-on: [push, pull_request]
-
-jobs:
-
-  test:
-    strategy:
-      matrix:
-        os:
-          - ubuntu-latest
-          - windows-latest
-          - macos-latest
-
-    runs-on: ${{ matrix.os }}
-    continue-on-error: true
-
-    steps:
-    - uses: actions/checkout@v4
-    - run: bazelisk test --config=ci ...
-      working-directory: test
-      env:
-        USE_BAZEL_VERSION: 6.x

.github/workflows/build.yml

@@ -5,21 +5,57 @@ on: [push, pull_request]
 jobs:
 
   linux:
+    timeout-minutes: 15
+
     strategy:
       matrix:
+        os: [ubuntu-latest, ubuntu-20.04]
         compiler:
+          - { pkg: g++, exe: 'g++', version: 7 }
+          - { pkg: g++, exe: 'g++', version: 8 }
+          - { pkg: g++, exe: 'g++', version: 9 }
+          - { pkg: g++, exe: 'g++', version: 10 }
+          - { pkg: g++, exe: 'g++', version: 11 }
           - { pkg: g++, exe: 'g++', version: 12 }
-          - { pkg: g++, exe: 'g++', version: 13 }
-          - { pkg: g++, exe: 'g++', version: 14 }
-          - { pkg: clang, exe: 'clang++', version: 16 }
-          - { pkg: clang, exe: 'clang++', version: 17 }
-          - { pkg: clang, exe: 'clang++', version: 18 }
+          - { pkg: clang, exe: 'clang++', version: 8 }
+          - { pkg: clang, exe: 'clang++', version: 9 }
+          - { pkg: clang, exe: 'clang++', version: 10 }
+          - { pkg: clang, exe: 'clang++', version: 11 }
+          - { pkg: clang, exe: 'clang++', version: 12 }
+          - { pkg: clang, exe: 'clang++', version: 13 }
+          - { pkg: clang, exe: 'clang++', version: 14 }
+        exclude:
+          - os: ubuntu-latest
+            compiler: { pkg: g++, exe: 'g++', version: 7 }
+          - os: ubuntu-latest
+            compiler: { pkg: g++, exe: 'g++', version: 8 }
+          - os: ubuntu-latest
+            compiler: { pkg: g++, exe: 'g++', version: 9 }
+          - os: ubuntu-latest
+            compiler: { pkg: clang, exe: 'clang++', version: 8 }
+          - os: ubuntu-latest
+            compiler: { pkg: clang, exe: 'clang++', version: 9 }
+          - os: ubuntu-latest
+            compiler: { pkg: clang, exe: 'clang++', version: 10 }
+          - os: ubuntu-latest
+            compiler: { pkg: clang, exe: 'clang++', version: 11 }
+          - os: ubuntu-20.04
+            compiler: { pkg: g++, exe: 'g++', version: 10 }
+          - os: ubuntu-20.04
+            compiler: { pkg: g++, exe: 'g++', version: 11 }
+          - os: ubuntu-20.04
+            compiler: { pkg: g++, exe: 'g++', version: 12 }
+          - os: ubuntu-20.04
+            compiler: { pkg: clang, exe: 'clang++', version: 12 }
+          - os: ubuntu-20.04
+            compiler: { pkg: clang, exe: 'clang++', version: 13 }
+          - os: ubuntu-20.04
+            compiler: { pkg: clang, exe: 'clang++', version: 14 }
 
-    timeout-minutes: 15
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v3
     - name: Install compiler
       run: |
         sudo apt update
@@ -35,23 +71,26 @@ jobs:
       working-directory: build
       env:
         CTEST_OUTPUT_ON_FAILURE: 1
-      run: ctest -C Debug -j4
+      run: ctest --timeout 30 -C Debug -j4
 
   windows:
+    timeout-minutes: 15
+
     strategy:
       matrix:
-        toolset: [default, v142, clang-cl]
+        toolset: [default, v141, v142, clang-cl]
         include:
+          - toolset: v141
+            toolset_option: -T"v141"
           - toolset: v142
             toolset_option: -T"v142"
           - toolset: clang-cl
             toolset_option: -T"ClangCl"
 
-    timeout-minutes: 15
     runs-on: windows-latest
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v3
     - name: Compile tests
       working-directory: build
       run: |
@@ -61,14 +100,14 @@ jobs:
       working-directory: build
       env:
         CTEST_OUTPUT_ON_FAILURE: 1
-      run: ctest -C Debug -j4
+      run: ctest --timeout 30 -C Debug -j4
 
   macos:
     timeout-minutes: 15
     runs-on: macOS-latest
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v3
     - name: Compile tests
       working-directory: build
       run: |
@@ -78,20 +117,21 @@ jobs:
       working-directory: build
       env:
         CTEST_OUTPUT_ON_FAILURE: 1
-      run: ctest -C Debug -j4
+      run: ctest --timeout 30 -C Debug -j4
 
   extra:
+    timeout-minutes: 15
+
     strategy:
       matrix:
         os: [windows-latest, macOS-latest, ubuntu-latest]
         id_type: ["std::uint32_t", "std::uint64_t"]
         cxx_std: [cxx_std_17, cxx_std_20]
 
-    timeout-minutes: 15
     runs-on: ${{ matrix.os }}
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v3
     - name: Compile tests
       working-directory: build
       run: |
@@ -101,4 +141,4 @@ jobs:
       working-directory: build
       env:
         CTEST_OUTPUT_ON_FAILURE: 1
-      run: ctest -C Debug -j4
+      run: ctest --timeout 30 -C Debug -j4

.github/workflows/coverage.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v3
     - name: Compile tests
       working-directory: build
       env:
@@ -22,12 +22,12 @@ jobs:
       working-directory: build
       env:
         CTEST_OUTPUT_ON_FAILURE: 1
-      run: ctest -C Debug -j4
+      run: ctest --timeout 30 -C Debug -j4
     - name: Collect data
       working-directory: build
       run: |
         sudo apt install lcov
-        lcov -c -d . -o coverage.info --ignore-errors gcov,gcov,mismatch,mismatch
+        lcov -c -d . -o coverage.info
         lcov -l coverage.info
     - name: Upload coverage to Codecov
       uses: codecov/codecov-action@v3

.github/workflows/sanitizer.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v3
     - name: Compile tests
       working-directory: build
       env:
@@ -28,4 +28,4 @@ jobs:
       working-directory: build
       env:
         CTEST_OUTPUT_ON_FAILURE: 1
-      run: ctest -C Debug -j4
+      run: ctest --timeout 30 -C Debug -j4

.gitignore

@@ -11,6 +11,3 @@ cpp.hint
 
 # Bazel
 /bazel-*
-/test/bazel-*
-/user.bazelrc
-*.bazel.lock

BUILD.bazel

@@ -1,6 +1,14 @@
-package(default_visibility = ["//visibility:public"])
+_msvc_copts = ["/std:c++17"]	
+_gcc_copts = ["-std=c++17"]
 
-alias(
+cc_library(
     name = "entt",
-    actual = "//src:entt",
+    visibility = ["//visibility:public"],
+    strip_include_prefix = "src",
+    hdrs = glob(["src/**/*.h", "src/**/*.hpp"]),
+    copts = select({
+      "@bazel_tools//src/conditions:windows": _msvc_copts,
+      "@bazel_tools//src/conditions:windows_msvc": _msvc_copts,
+      "//conditions:default": _gcc_copts,
+    }),
 )

CMakeLists.txt

@@ -1,15 +1,21 @@
+#
 # EnTT
+#
 
 cmake_minimum_required(VERSION 3.15.7)
 
+#
 # Read project version
+#
 
 set(ENTT_VERSION_REGEX "#define ENTT_VERSION_.*[ \t]+(.+)")
 file(STRINGS "${CMAKE_CURRENT_SOURCE_DIR}/src/entt/config/version.h" ENTT_VERSION REGEX ${ENTT_VERSION_REGEX})
 list(TRANSFORM ENTT_VERSION REPLACE ${ENTT_VERSION_REGEX} "\\1")
 string(JOIN "." ENTT_VERSION ${ENTT_VERSION})
 
+#
 # Project configuration
+#
 
 project(
     EnTT
@@ -25,18 +31,21 @@ endif()
 
 message(VERBOSE "*")
 message(VERBOSE "* ${PROJECT_NAME} v${PROJECT_VERSION} (${CMAKE_BUILD_TYPE})")
-message(VERBOSE "* Copyright (c) 2017-2025 Michele Caini <michele.caini@gmail.com>")
+message(VERBOSE "* Copyright (c) 2017-2023 Michele Caini <michele.caini@gmail.com>")
 message(VERBOSE "*")
 
+#
 # CMake stuff
+#
 
 list(INSERT CMAKE_MODULE_PATH 0 ${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules)
 
+#
 # Compiler stuff
+#
 
 option(ENTT_USE_LIBCPP "Use libc++ by adding -stdlib=libc++ flag if available." OFF)
 option(ENTT_USE_SANITIZER "Enable sanitizers by adding -fsanitize=address -fno-omit-frame-pointer -fsanitize=undefined flags if available." OFF)
-option(ENTT_USE_CLANG_TIDY "Enable static analysis with clang-tidy" OFF)
 
 if(ENTT_USE_LIBCPP)
     if(NOT WIN32)
@@ -56,7 +65,7 @@ if(ENTT_USE_LIBCPP)
     endif()
 
     if(NOT ENTT_HAS_LIBCPP)
-        message(VERBOSE "The option ENTT_USE_LIBCPP is set but libc++ is not available.")
+        message(VERBOSE "The option ENTT_USE_LIBCPP is set but libc++ is not available. The flag will not be added to the target.")
     endif()
 endif()
 
@@ -67,48 +76,13 @@ if(ENTT_USE_SANITIZER)
     endif()
 
     if(NOT ENTT_HAS_SANITIZER)
-        message(VERBOSE "The option ENTT_USE_SANITIZER is set but sanitizer support is not available.")
-    endif()
-endif()
-
-if(ENTT_USE_CLANG_TIDY)
-    find_program(ENTT_CLANG_TIDY_EXECUTABLE "clang-tidy")
-
-    if(NOT ENTT_CLANG_TIDY_EXECUTABLE)
-        message(VERBOSE "The option ENTT_USE_CLANG_TIDY is set but clang-tidy executable is not available.")
+        message(VERBOSE "The option ENTT_USE_SANITIZER is set but sanitizer support is not available. The flags will not be added to the target.")
     endif()
 endif()
 
+#
 # Add EnTT target
-
-include(GNUInstallDirs)
-
-add_library(EnTT INTERFACE)
-add_library(EnTT::EnTT ALIAS EnTT)
-
-target_include_directories(
-    EnTT
-    INTERFACE
-        $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src>
-        $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
-)
-
-target_compile_features(EnTT INTERFACE cxx_std_17)
-
-if(ENTT_HAS_LIBCPP)
-    target_compile_options(EnTT BEFORE INTERFACE -stdlib=libc++)
-endif()
-
-if(ENTT_HAS_SANITIZER)
-    target_compile_options(EnTT INTERFACE $<$<CONFIG:Debug>:-fsanitize=address -fno-omit-frame-pointer -fsanitize=undefined>)
-    target_link_libraries(EnTT INTERFACE $<$<CONFIG:Debug>:-fsanitize=address -fno-omit-frame-pointer -fsanitize=undefined>)
-endif()
-
-if(ENTT_CLANG_TIDY_EXECUTABLE)
-    set(CMAKE_CXX_CLANG_TIDY "${ENTT_CLANG_TIDY_EXECUTABLE};--config-file=${EnTT_SOURCE_DIR}/.clang-tidy;--header-filter=${EnTT_SOURCE_DIR}/src/entt/.*")
-endif()
-
-# Add EnTT goodies
+#
 
 option(ENTT_INCLUDE_HEADERS "Add all EnTT headers to the EnTT target." OFF)
 option(ENTT_INCLUDE_NATVIS "Add EnTT natvis files to the EnTT target." OFF)
@@ -124,6 +98,20 @@ if(ENTT_INCLUDE_NATVIS)
     endif()
 endif()
 
+include(GNUInstallDirs)
+
+add_library(EnTT INTERFACE)
+add_library(EnTT::EnTT ALIAS EnTT)
+
+target_include_directories(
+    EnTT
+    INTERFACE
+        $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src>
+        $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
+)
+
+target_compile_features(EnTT INTERFACE cxx_std_17)
+
 if(ENTT_INCLUDE_HEADERS)
     target_sources(
         EnTT
@@ -133,12 +121,10 @@ if(ENTT_INCLUDE_HEADERS)
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/config/version.h>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/container/dense_map.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/container/dense_set.hpp>
-            $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/container/table.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/container/fwd.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/core/algorithm.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/core/any.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/core/attribute.h>
-            $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/core/bit.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/core/compressed_pair.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/core/enum.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/core/family.hpp>
@@ -148,7 +134,6 @@ if(ENTT_INCLUDE_HEADERS)
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/core/iterator.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/core/memory.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/core/monostate.hpp>
-            $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/core/ranges.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/core/tuple.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/core/type_info.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/core/type_traits.hpp>
@@ -160,8 +145,8 @@ if(ENTT_INCLUDE_HEADERS)
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/entity/handle.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/entity/mixin.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/entity/helper.hpp>
+            $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/entity/observer.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/entity/organizer.hpp>
-            $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/entity/ranges.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/entity/registry.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/entity/runtime_view.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/entity/snapshot.hpp>
@@ -187,6 +172,7 @@ if(ENTT_INCLUDE_HEADERS)
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/meta/template.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/meta/type_traits.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/meta/utility.hpp>
+            $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/platform/android-ndk-r17.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/poly/fwd.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/poly/poly.hpp>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src/entt/process/fwd.hpp>
@@ -217,6 +203,7 @@ if(ENTT_HAS_NATVIS)
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/natvis/entt/graph.natvis>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/natvis/entt/locator.natvis>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/natvis/entt/meta.natvis>
+            $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/natvis/entt/platform.natvis>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/natvis/entt/poly.natvis>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/natvis/entt/process.natvis>
             $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/natvis/entt/resource.natvis>
@@ -224,90 +211,92 @@ if(ENTT_HAS_NATVIS)
     )
 endif()
 
-# Install EnTT and all related files
-
-option(ENTT_INSTALL "Install EnTT and all related files." OFF)
-
-if(ENTT_INSTALL)
-    # Install pkg-config file
-
-    include(JoinPaths)
-
-    set(EnTT_PKGCONFIG ${CMAKE_CURRENT_BINARY_DIR}/entt.pc)
-
-    join_paths(EnTT_PKGCONFIG_INCLUDEDIR "\${prefix}" "${CMAKE_INSTALL_INCLUDEDIR}")
-
-    configure_file(
-        ${EnTT_SOURCE_DIR}/cmake/in/entt.pc.in
-        ${EnTT_PKGCONFIG}
-        @ONLY
-    )
-
-    install(
-        FILES ${EnTT_PKGCONFIG}
-        DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig
-    )
-
-    # Install EnTT
-
-    include(CMakePackageConfigHelpers)
-
-    install(
-        TARGETS EnTT
-        EXPORT EnTTTargets
-        ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
-    )
-
-    write_basic_package_version_file(
-        EnTTConfigVersion.cmake
-        VERSION ${PROJECT_VERSION}
-        COMPATIBILITY AnyNewerVersion
-    )
-
-    configure_package_config_file(
-        ${EnTT_SOURCE_DIR}/cmake/in/EnTTConfig.cmake.in
-        EnTTConfig.cmake
-        INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/EnTT/cmake
-    )
-
-    export(
-        EXPORT EnTTTargets
-        FILE ${CMAKE_CURRENT_BINARY_DIR}/EnTTTargets.cmake
-        NAMESPACE EnTT::
-    )
-
-    install(
-        EXPORT EnTTTargets
-        FILE EnTTTargets.cmake
-        DESTINATION ${CMAKE_INSTALL_LIBDIR}/EnTT/cmake
-        NAMESPACE EnTT::
-    )
-
-    install(
-        FILES
-            ${PROJECT_BINARY_DIR}/EnTTConfig.cmake
-            ${PROJECT_BINARY_DIR}/EnTTConfigVersion.cmake
-        DESTINATION ${CMAKE_INSTALL_LIBDIR}/EnTT/cmake
-    )
-
-    install(
-        DIRECTORY src/
-        DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
-        FILES_MATCHING
-        PATTERN "*.h"
-        PATTERN "*.hpp"
-    )
-
-    export(PACKAGE EnTT)
+if(ENTT_HAS_SANITIZER)
+    target_compile_options(EnTT INTERFACE $<$<CONFIG:Debug>:-fsanitize=address -fno-omit-frame-pointer -fsanitize=undefined>)
+    target_link_libraries(EnTT INTERFACE $<$<CONFIG:Debug>:-fsanitize=address -fno-omit-frame-pointer -fsanitize=undefined>)
 endif()
 
+if(ENTT_HAS_LIBCPP)
+    target_compile_options(EnTT BEFORE INTERFACE -stdlib=libc++)
+endif()
+
+#
+# Install pkg-config file
+#
+
+include(JoinPaths)
+
+set(EnTT_PKGCONFIG ${CMAKE_CURRENT_BINARY_DIR}/entt.pc)
+
+join_paths(EnTT_PKGCONFIG_INCLUDEDIR "\${prefix}" "${CMAKE_INSTALL_INCLUDEDIR}")
+
+configure_file(
+    ${EnTT_SOURCE_DIR}/cmake/in/entt.pc.in
+    ${EnTT_PKGCONFIG}
+    @ONLY
+)
+
+install(
+    FILES ${EnTT_PKGCONFIG}
+    DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig
+)
+
+#
+# Install EnTT
+#
+
+include(CMakePackageConfigHelpers)
+
+install(
+    TARGETS EnTT
+    EXPORT EnTTTargets
+    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
+)
+
+write_basic_package_version_file(
+    EnTTConfigVersion.cmake
+    VERSION ${PROJECT_VERSION}
+    COMPATIBILITY AnyNewerVersion
+)
+
+configure_package_config_file(
+    ${EnTT_SOURCE_DIR}/cmake/in/EnTTConfig.cmake.in
+    EnTTConfig.cmake
+    INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/EnTT/cmake
+)
+
+export(
+    EXPORT EnTTTargets
+    FILE ${CMAKE_CURRENT_BINARY_DIR}/EnTTTargets.cmake
+    NAMESPACE EnTT::
+)
+
+install(
+    EXPORT EnTTTargets
+    FILE EnTTTargets.cmake
+    DESTINATION ${CMAKE_INSTALL_LIBDIR}/EnTT/cmake
+    NAMESPACE EnTT::
+)
+
+install(
+    FILES
+        ${PROJECT_BINARY_DIR}/EnTTConfig.cmake
+        ${PROJECT_BINARY_DIR}/EnTTConfigVersion.cmake
+    DESTINATION ${CMAKE_INSTALL_LIBDIR}/EnTT/cmake
+)
+
+install(DIRECTORY src/ DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+
+export(PACKAGE EnTT)
+
+#
 # Tests
+#
 
 option(ENTT_BUILD_TESTING "Enable building tests." OFF)
 
 if(ENTT_BUILD_TESTING)
     option(ENTT_FIND_GTEST_PACKAGE "Enable finding gtest package." OFF)
-
     option(ENTT_BUILD_BENCHMARK "Build benchmark." OFF)
     option(ENTT_BUILD_EXAMPLE "Build examples." OFF)
     option(ENTT_BUILD_LIB "Build lib tests." OFF)
@@ -321,10 +310,16 @@ if(ENTT_BUILD_TESTING)
     add_subdirectory(test)
 endif()
 
+#
 # Documentation
+#
 
 option(ENTT_BUILD_DOCS "Enable building with documentation." OFF)
 
 if(ENTT_BUILD_DOCS)
-    add_subdirectory(docs)
+    find_package(Doxygen 1.8)
+
+    if(DOXYGEN_FOUND)
+        add_subdirectory(docs)
+    endif()
 endif()

LICENSE

@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2017-2025 Michele Caini, author of EnTT
+Copyright (c) 2017-2023 Michele Caini, author of EnTT
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

MODULE.bazel

@@ -1,4 +0,0 @@
-module(name = "entt")
-
-bazel_dep(name = "rules_cc", version = "0.0.8")
-bazel_dep(name = "bazel_skylib", version = "1.4.2")

README.md

@@ -1,13 +1,16 @@
 ![EnTT: Gaming meets modern C++](https://user-images.githubusercontent.com/1812216/103550016-90752280-4ea8-11eb-8667-12ed2219e137.png)
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 [![Build Status](https://github.com/skypjack/entt/workflows/build/badge.svg)](https://github.com/skypjack/entt/actions)
 [![Coverage](https://codecov.io/gh/skypjack/entt/branch/master/graph/badge.svg)](https://codecov.io/gh/skypjack/entt)
 [![Try online](https://img.shields.io/badge/try-online-brightgreen)](https://godbolt.org/z/zxW73f)
-[![Documentation](https://img.shields.io/badge/docs-doxygen-blue)](https://skypjack.github.io/entt/)
 [![Vcpkg port](https://img.shields.io/vcpkg/v/entt)](https://vcpkg.link/ports/entt)
-[![Conan Center](https://img.shields.io/conan/v/entt)](https://conan.io/center/recipes/entt)
+[![Documentation](https://img.shields.io/badge/docs-doxygen-blue)](https://skypjack.github.io/entt/)
 [![Gitter chat](https://badges.gitter.im/skypjack/entt.png)](https://gitter.im/skypjack/entt)
 [![Discord channel](https://img.shields.io/discord/707607951396962417?logo=discord)](https://discord.gg/5BjPWBd)
+[![Donate](https://img.shields.io/badge/donate-paypal-blue.svg)](https://www.paypal.me/skypjack)
 
 > `EnTT` has been a dream so far, we haven't found a single bug to date and it's
 > super easy to work with
@@ -21,7 +24,7 @@ in [**Minecraft**](https://minecraft.net/en-us/attribution/) by Mojang, the
 [**ArcGIS Runtime SDKs**](https://developers.arcgis.com/arcgis-runtime/) by Esri
 and the amazing [**Ragdoll**](https://ragdolldynamics.com/).<br/>
 If you don't see your project in the list, please open an issue, submit a PR or
-add the [\#entt](https://github.com/topics/entt) tag to your _topics_! :+1:
+add the [#entt](https://github.com/topics/entt) tag to your _topics_! :+1:
 
 ---
 
@@ -36,8 +39,7 @@ Don't forget to check the
 there.
 
 Do you want to support `EnTT`? Consider becoming a
-[**sponsor**](https://github.com/users/skypjack/sponsorship) or making a
-donation via [**PayPal**](https://www.paypal.me/skypjack).<br/>
+[**sponsor**](https://github.com/users/skypjack/sponsorship).
 Many thanks to [these people](https://skypjack.github.io/sponsorship/) and
 **special** thanks to:
 
@@ -49,7 +51,7 @@ Many thanks to [these people](https://skypjack.github.io/sponsorship/) and
 * [Introduction](#introduction)
   * [Code Example](#code-example)
   * [Motivation](#motivation)
-  * [Benchmark](#benchmark)
+  * [Performance](#performance)
 * [Integration](#integration)
   * [Requirements](#requirements)
   * [CMake](#cmake)
@@ -61,6 +63,9 @@ Many thanks to [these people](https://skypjack.github.io/sponsorship/) and
 * [EnTT in Action](#entt-in-action)
 * [Contributors](#contributors)
 * [License](#license)
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # Introduction
 
@@ -170,28 +175,37 @@ Nowadays, `EnTT` is finally what I was looking for: still faster than its
 _competitors_, lower memory usage in the average case, a really good API and an
 amazing set of features. And even more, of course.
 
-## Benchmark
+## Performance
 
-For what it's worth, you'll **never** see me trying to make other projects look
-bad or offer dubious comparisons just to make this library seem cooler.<br/>
-I leave this activity to others, if they enjoy it (and it seems that some people
-actually like it). I prefer to make better use of my time.
+The proposed entity-component system is incredibly fast to iterate entities and
+components, this is a fact. Some compilers make a lot of optimizations because
+of how `EnTT` works, some others aren't that good. In general, if we consider
+real world cases, `EnTT` is somewhere between a bit and much faster than many of
+the other solutions around, although I couldn't check them all for obvious
+reasons.
 
 If you are interested, you can compile the `benchmark` test in release mode (to
 enable compiler optimizations, otherwise it would make little sense) by setting
 the `ENTT_BUILD_BENCHMARK` option of `CMake` to `ON`, then evaluate yourself
 whether you're satisfied with the results or not.
 
-There are also a lot of projects out there that use `EnTT` as a basis for
+Honestly I got tired of updating the README file whenever there is an
+improvement.<br/>
+There are already a lot of projects out there that use `EnTT` as a basis for
 comparison (this should already tell you a lot). Many of these benchmarks are
 completely wrong, many others are simply incomplete, good at omitting some
 information and using the wrong function to compare a given feature. Certainly
 there are also good ones but they age quickly if nobody updates them, especially
-when the library they are dealing with is actively developed.<br/>
-Out of all of them, [this](https://github.com/abeimler/ecs_benchmark) seems like
-the most up-to-date project and also covers a certain number of libraries. I
-can't say exactly whether `EnTT` is used correctly or not. However, even if used
-poorly, it should still give the reader an idea of where it's going to operate.
+when the library they are dealing with is actively developed.
+
+The choice to use `EnTT` should be based on its carefully designed API, its
+set of features and the general performance, **not** because some single
+benchmark shows it to be the fastest tool available.
+
+In the future I'll likely try to get even better performance while still adding
+new features, mainly for fun.<br/>
+If you want to contribute and/or have suggestions, feel free to make a PR or
+open an issue to discuss your idea.
 
 # Integration
 
@@ -236,9 +250,9 @@ To use `EnTT` from a `CMake` project, just link an existing target to the
 The library offers everything you need for locating (as in `find_package`),
 embedding (as in `add_subdirectory`), fetching (as in `FetchContent`) or using
 it in many of the ways that you can think of and that involve `CMake`.<br/>
-Covering all possible cases would require a treatise and not a simple README
-file, but I'm confident that anyone reading this section also knows what it's
-about and can use `EnTT` from a `CMake` project without problems.
+Covering all possible cases would require a treaty and not a simple README file,
+but I'm confident that anyone reading this section also knows what it's about
+and can use `EnTT` from a `CMake` project without problems.
 
 ## Natvis support
 
@@ -313,18 +327,6 @@ If you spot errors or have suggestions, any contribution is welcome!
   [documentation](https://build2.org/build2-toolchain/doc/build2-toolchain-intro.xhtml#guide-repositories)
   for more details.
 
-* [`bzlmod`](https://bazel.build/external/overview#bzlmod), Bazel's external
-  dependency management system.<br/>
-  To use the [`entt`](https://registry.bazel.build/modules/entt) module in a
-  `bazel` project, add the following to your `MODULE.bazel` file:
-
-  ```starlark
-  bazel_dep(name = "entt", version = "3.12.2")
-  ```
-
-  EnTT will now be available as `@entt` (short for `@entt//:entt`) to be used
-  in your `cc_*` rule `deps`. 
-
 Consider this list a work in progress and help me to make it longer if you like.
 
 ## pkg-config
@@ -348,10 +350,16 @@ To navigate it with your favorite browser:
     $ cd build
     $ your_favorite_browser docs/html/index.html
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 The same version is also available [online](https://skypjack.github.io/entt/)
 for the latest release, that is the last stable tag.<br/>
 Moreover, there exists a [wiki](https://github.com/skypjack/entt/wiki) dedicated
 to the project where users can find all related documentation pages.
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # Tests
 
@@ -368,6 +376,9 @@ To build the most basic set of tests:
 
 Note that benchmarks are not part of this set.
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 # EnTT in Action
 
 `EnTT` is widely used in private and commercial applications. I cannot even
@@ -385,7 +396,7 @@ open an issue or a PR and I'll be glad to add them to the list.
 
 # Contributors
 
-Requests for features, PRs, suggestions and feedback are highly appreciated.
+Requests for features, PRs, suggestions ad feedback are highly appreciated.
 
 If you find you can help and want to contribute to the project with your
 experience or you do want to get part of the project for some other reason, feel
@@ -395,15 +406,18 @@ I can't promise that each and every contribution will be accepted, but I can
 assure that I'll do my best to take them all as soon as possible.
 
 If you decide to participate, please see the guidelines for
-[contributing](https://github.com/skypjack/entt/blob/master/CONTRIBUTING.md)
-before to create issues or pull requests.<br/>
+[contributing](CONTRIBUTING.md) before to create issues or pull
+requests.<br/>
 Take also a look at the
 [contributors list](https://github.com/skypjack/entt/blob/master/AUTHORS) to
 know who has participated so far.
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # License
 
-Code and documentation Copyright (c) 2017-2025 Michele Caini.<br/>
+Code and documentation Copyright (c) 2017-2023 Michele Caini.<br/>
 Colorful logo Copyright (c) 2018-2021 Richard Caseres.
 
 Code released under

TODO

@@ -4,34 +4,23 @@ EXAMPLES
 
 DOC:
 * custom storage/view
+* examples (and credits) from @alanjfs :)
 * update entity doc when the storage based model is in place
 * in-place O(1) release/destroy for non-orphaned entities, out-of-sync model
-* view: single vs multi type views are no longer a thing actually
-* bump entities, reserved bits on identifiers
 
-TODO:
-* review all NOLINT
+TODO (high prio):
+* check natvis files (periodically :)
+* resource cache: avoid using shared ptr with loader and the others
+* further optimize exclusion lists in multi type views (no existence check)
+* further improve the snapshot stuff, ie component functions
+* use fixture for storage tests to reduce loc number and duplication as much as possible
+* basic_view<...>::reach(...)
+* doc: bump entities
+
+WIP:
+* get rid of observers, storage based views made them pointless - document alternatives
+* exploit the tombstone mechanism to allow enabling/disabling entities (see bump, compact and clear for further details)
+* process scheduler: reviews, use free lists internally
+* deprecate non-owning groups in favor of owning views and view packs, introduce lazy owning views
 * bring nested groups back in place (see bd34e7f)
 * work stealing job system (see #100) + mt scheduler based on const awareness for types
-* view: reduce inst due to/improve perf with index-based approach in dispatch_get/pick_and_each/each (single type too, define storage ::at and ::at_as_tuple)
-* view: update natvis as needed after the last rework, merge pools/filter in the same array, drop check (?) and turn view into a position
-* view: type-only view_iterator (dyn get/excl sizes), type-only basic_common_view (dyn get/excl sizes with pointer to array from derived)
-* combine version-mask-vs-version-bits tricks with reserved bits to allow things like enabling/disabling
-* self contained entity traits to avoid explicit specializations (ie enum constants)
-* auto type info data from types if present
-* test: push sharing types further
-* storage entity: fast range-push from above
-* table: pop back to support swap and pop, single column access, empty type optimization
-* review cmake warning about FetchContent_Populate (need .28 and EXCLUDE_FROM_ALL for FetchContent)
-* suppress -Wself-move on CI with g++13
-* view specializations for multi, single and filtered elements
-* don't pass reactive storage by default to callback
-* runtime types support for meta for types that aren't backed by C++ types
-* built-in no-pagination storage - no_pagination page size as limits::max
-* any cdynamic to support const ownership construction
-* allow passing arguments to meta setter/getter (we can fallback on meta invoke probably)
-* FetchContent_Populate -> FetchContent_MakeAvailable warnings
-* doc: IMPLICIT_DIR_DOCS for dir docs or \dir
-* meta non-const allow_cast overloads: (const int &) to (int &) is not allowed, but (const int &) to (double &) is allowed (support only for convertibles)
-* improve non-const allow cast with in-place switch
-* meta fixed_size could return the size directly if present

WORKSPACE

@@ -0,0 +1 @@
+workspace(name = "com_github_skypjack_entt")

WORKSPACE.bazel

@@ -1 +0,0 @@
-# SEE MODULE.bazel

bazel/copts.bzl

@@ -1,13 +0,0 @@
-load("@bazel_skylib//lib:selects.bzl", "selects")
-
-COPTS = selects.with_or({
-    ("//conditions:default", "@rules_cc//cc/compiler:clang", "@rules_cc//cc/compiler:gcc", "@rules_cc//cc/compiler:mingw-gcc"): [
-        "-std=c++17",
-        "-w",
-    ],
-    ("@rules_cc//cc/compiler:msvc-cl", "@rules_cc//cc/compiler:clang-cl"): [
-        "/std:c++17",
-        "/permissive-",
-        "/w",
-    ],
-})

conan/test_package/test_package.cpp

@@ -15,7 +15,7 @@ void update(entt::registry &registry) {
     auto view = registry.view<position, velocity>();
 
     for(auto entity: view) {
-        // gets only the elements that are going to be used ...
+        // gets only the components that are going to be used ...
 
         auto &vel = view.get<velocity>(entity);
 
@@ -28,7 +28,7 @@ void update(entt::registry &registry) {
 
 void update(std::uint64_t dt, entt::registry &registry) {
     registry.view<position, velocity>().each([dt](auto &pos, auto &vel) {
-        // gets all the elements of the view at once ...
+        // gets all the components of the view at once ...
 
         pos.x += vel.dx * dt;
         pos.y += vel.dy * dt;

docs/CMakeLists.txt

@@ -1,59 +1,54 @@
+#
 # Doxygen configuration (documentation)
+#
 
-find_package(Doxygen 1.13)
+FetchContent_Declare(
+    doxygen-awesome-css
+    GIT_REPOSITORY https://github.com/jothepro/doxygen-awesome-css
+    GIT_TAG main
+    GIT_SHALLOW 1
+)
 
-if(DOXYGEN_FOUND)
-    include(FetchContent)
+FetchContent_GetProperties(doxygen-awesome-css)
 
-    FetchContent_Declare(
-        doxygen-awesome-css
-        GIT_REPOSITORY https://github.com/jothepro/doxygen-awesome-css
-        GIT_TAG main
-        GIT_SHALLOW 1
-    )
-
-    FetchContent_GetProperties(doxygen-awesome-css)
-
-    if(NOT doxygen-awesome-css_POPULATED)
-        FetchContent_Populate(doxygen-awesome-css)
-        set(doxygen-awesome-css_INCLUDE_DIR ${doxygen-awesome-css_SOURCE_DIR})
-    endif()
-
-    set(DOXY_SOURCE_DIRECTORY ${EnTT_SOURCE_DIR}/src)
-    set(DOXY_CSS_DIRECTORY ${doxygen-awesome-css_INCLUDE_DIR})
-    set(DOXY_DOCS_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
-    set(DOXY_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
-
-    configure_file(doxy.in doxy.cfg @ONLY)
-
-    add_custom_target(
-        docs ALL
-        COMMAND ${DOXYGEN_EXECUTABLE} ${CMAKE_CURRENT_BINARY_DIR}/doxy.cfg
-        WORKING_DIRECTORY ${EnTT_SOURCE_DIR}
-        VERBATIM
-        SOURCES
-            md/config.md
-            md/container.md
-            md/core.md
-            md/entity.md
-            md/faq.md
-            md/lib.md
-            md/links.md
-            md/locator.md
-            md/meta.md
-            md/poly.md
-            md/process.md
-            md/reference.md
-            md/resource.md
-            md/signal.md
-            md/unreal.md
-            doxy.in
-    )
-
-    if(ENTT_INSTALL)
-        install(
-            DIRECTORY ${DOXY_OUTPUT_DIRECTORY}/html
-            DESTINATION share/${PROJECT_NAME}-${PROJECT_VERSION}/
-        )
-    endif()
+if(NOT doxygen-awesome-css_POPULATED)
+    FetchContent_Populate(doxygen-awesome-css)
+    set(doxygen-awesome-css_INCLUDE_DIR ${doxygen-awesome-css_SOURCE_DIR})
 endif()
+
+set(DOXY_SOURCE_DIRECTORY ${EnTT_SOURCE_DIR}/src)
+set(DOXY_CSS_DIRECTORY ${doxygen-awesome-css_INCLUDE_DIR})
+set(DOXY_DOCS_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
+set(DOXY_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
+
+configure_file(doxy.in doxy.cfg @ONLY)
+
+add_custom_target(
+    docs ALL
+    COMMAND ${DOXYGEN_EXECUTABLE} ${CMAKE_CURRENT_BINARY_DIR}/doxy.cfg
+    WORKING_DIRECTORY ${EnTT_SOURCE_DIR}
+    VERBATIM
+    SOURCES
+        dox/extra.dox
+        md/config.md
+        md/container.md
+        md/core.md
+        md/entity.md
+        md/faq.md
+        md/lib.md
+        md/links.md
+        md/locator.md
+        md/meta.md
+        md/poly.md
+        md/process.md
+        md/reference.md
+        md/resource.md
+        md/signal.md
+        md/unreal.md
+        doxy.in
+)
+
+install(
+    DIRECTORY ${DOXY_OUTPUT_DIRECTORY}/html
+    DESTINATION share/${PROJECT_NAME}-${PROJECT_VERSION}/
+)

docs/dox/extra.dox

@@ -0,0 +1,5 @@
+/**
+ * @namespace entt
+ *
+ * @brief `EnTT` default namespace.
+ */

docs/md/config.md

@@ -1,5 +1,8 @@
 # Crash Course: configuration
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 # Table of Contents
 
 * [Introduction](#introduction)
@@ -14,6 +17,9 @@
     * [ENTT_DISABLE_ASSERT](#entt_disable_assert)
   * [ENTT_NO_ETO](#entt_no_eto)
   * [ENTT_STANDARD_CPP](#entt_standard_cpp)
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # Introduction
 
@@ -22,14 +28,14 @@ respects. These variables are just one of the many ways to customize how it
 works.<br/>
 In the vast majority of cases, users will have no interest in changing the
 default parameters. For all other cases, the list of possible configurations
-with which it is possible to adjust the behavior of the library at runtime can
-be found below.
+with which it's possible to adjust the behavior of the library at runtime can be
+found below.
 
 # Definitions
 
 All options are intended as parameters to the compiler (or user-defined macros
 within the compilation units, if preferred).<br/>
-Each parameter can result in internal library definitions. It is not recommended
+Each parameter can result in internal library definitions. It's not recommended
 to try to also modify these definitions, since there is no guarantee that they
 will remain stable over time unlike the options below.
 
@@ -42,10 +48,10 @@ also limited to this library only.
 
 ## ENTT_USE_ATOMIC
 
-In general, `EnTT` does not offer primitives to support multi-threading. Many of
+In general, `EnTT` doesn't offer primitives to support multi-threading. Many of
 the features can be split over multiple threads without any explicit control and
 the user is the one who knows if a synchronization point is required.<br/>
-However, some features are not easily accessible to users and are made
+However, some features aren't easily accessible to users and are made
 thread-safe by means of this definition.
 
 ## ENTT_ID_TYPE
@@ -57,25 +63,24 @@ default type if necessary.
 
 ## ENTT_SPARSE_PAGE
 
-It is known that the ECS module of `EnTT` is based on _sparse sets_. What is
-less known perhaps is that the sparse arrays are paged to reduce memory
-usage.<br/>
+It's known that the ECS module of `EnTT` is based on _sparse sets_. What is less
+known perhaps is that the sparse arrays are paged to reduce memory usage.<br/>
 Default size of pages (that is, the number of elements they contain) is 4096 but
-users can adjust it if appropriate. In all cases, the chosen value **must** be a
+users can adjust it if appropriate. In all case, the chosen value **must** be a
 power of 2.
 
 ## ENTT_PACKED_PAGE
 
 As it happens with sparse arrays, packed arrays are also paginated. However, in
-this case the aim is not to reduce memory usage but to have pointer stability
+this case the aim isn't to reduce memory usage but to have pointer stability
 upon component creation.<br/>
 Default size of pages (that is, the number of elements they contain) is 1024 but
-users can adjust it if appropriate. In all cases, the chosen value **must** be a
+users can adjust it if appropriate. In all case, the chosen value **must** be a
 power of 2.
 
 ## ENTT_ASSERT
 
-For performance reasons, `EnTT` does not use exceptions or any other control
+For performance reasons, `EnTT` doesn't use exceptions or any other control
 structures. In fact, it offers many features that result in undefined behavior
 if not used correctly.<br/>
 To get around this, the library relies on a lot of asserts for the purpose of
@@ -84,7 +89,7 @@ are allowed to overwrite its behavior by setting this variable.
 
 ### ENTT_ASSERT_CONSTEXPR
 
-Usually, an assert within a `constexpr` function is not a big deal. However, in
+Usually, an assert within a `constexpr` function isn't a big deal. However, in
 case of extreme customizations, it might be useful to differentiate.<br/>
 For this purpose, `EnTT` introduces an admittedly badly named variable to make
 the job easier in this regard. By default, this variable forwards its arguments
@@ -110,6 +115,6 @@ dedicated storage for them.
 `EnTT` mixes non-standard language features with others that are perfectly
 compliant to offer some of its functionalities.<br/>
 This definition prevents the library from using non-standard techniques, that
-is, functionalities that are not fully compliant with the standard C++.<br/>
+is, functionalities that aren't fully compliant with the standard C++.<br/>
 While there are no known portability issues at the time of this writing, this
 should make the library fully portable anyway if needed.

docs/md/container.md

@@ -1,30 +1,32 @@
 # Crash Course: containers
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 # Table of Contents
 
 * [Introduction](#introduction)
 * [Containers](#containers)
   * [Dense map](#dense-map)
   * [Dense set](#dense-set)
-* [Adaptors](#adaptors)
-  * [Table](#table)
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # Introduction
 
-The standard C++ library offers a wide range of containers and adaptors already.
-It is really difficult to do better (although it is very easy to do worse, as
-many examples available online demonstrate).<br/>
-`EnTT` does not try in any way to replace what is offered by the standard. Quite
+The standard C++ library offers a wide range of containers and it's really
+difficult to do better (although it's very easy to do worse, as many examples
+available online demonstrate).<br/>
+`EnTT` doesn't try in any way to replace what is offered by the standard. Quite
 the opposite, given the widespread use that is made of standard containers.<br/>
 However, the library also tries to fill a gap in features and functionalities by
-making available some containers and adaptors initially developed for internal
-use.
+making available some containers initially developed for internal use.
 
 This section of the library is likely to grow larger over time. However, for the
-moment it is quite small and mainly aimed at satisfying some internal
-needs.<br/>
-For all containers and adaptors made available, full test coverage and stability
-over time is guaranteed as usual.
+moment it's quite small and mainly aimed at satisfying some internal needs.<br/>
+For all containers made available, full test coverage and stability over time is
+guaranteed as usual.
 
 # Containers
 
@@ -61,25 +63,4 @@ implicit list within the packed array itself.
 
 The interface is in all respects similar to its counterpart in the standard
 library, that is, the `std::unordered_set` class.<br/>
-However, this type of set also supports reverse iteration and therefore offers
-all the functions necessary for the purpose (such as `rbegin` and `rend`).
-
-# Adaptors
-
-## Table
-
-The `basic_table` class is a container adaptor which manages multiple sequential
-containers together, treating them as different columns of the same table.<br/>
-The `table` alias allows users to provide only the types to handle, using
-`std::vector` as the default sequential container.
-
-Only a small set of functions is provided, although very close to what the API
-of the `std::vector` class offers.<br/>
-The internal implementation is purposely supported by a tuple of containers
-rather than a container of tuples. The purpose is to allow efficient access to
-single columns and not just access to the entire data set of the table.
-
-When a row is accessed, all data is returned in the form of a tuple containing
-(possibly const) references to the elements of the row itself.<br/>
-Similarly, when a table is iterated, tuples of references to table elements are
-returned for each row.
+Therefore, there is no need to go into the API description.

docs/md/core.md

@@ -1,22 +1,25 @@
 # Crash Course: core functionalities
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 # Table of Contents
 
 * [Introduction](#introduction)
 * [Any as in any type](#any-as-in-any-type)
   * [Small buffer optimization](#small-buffer-optimization)
   * [Alignment requirement](#alignment-requirement)
-* [Bit](#bit)
 * [Compressed pair](#compressed-pair)
 * [Enum as bitmask](#enum-as-bitmask)
 * [Hashed strings](#hashed-strings)
-  * [Wide characters](#wide-characters)
+  * [Wide characters](wide-characters)
   * [Conflicts](#conflicts)
 * [Iterators](#iterators)
   * [Input iterator pointer](#input-iterator-pointer)
   * [Iota iterator](#iota-iterator)
   * [Iterable adaptor](#iterable-adaptor)
 * [Memory](#memory)
+  * [Power of two and fast modulus](#power-of-two-and-fast-modulus)
   * [Allocator aware unique pointers](#allocator-aware-unique-pointers)
 * [Monostate](#monostate)
 * [Type support](#type-support)
@@ -36,12 +39,15 @@
   * [Compile-time generator](#compile-time-generator)
   * [Runtime generator](#runtime-generator)
 * [Utilities](#utilities)
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # Introduction
 
 `EnTT` comes with a bunch of core functionalities mostly used by the other parts
 of the library.<br/>
-Many of these tools are also useful in everyday work. Therefore, it is worth
+Many of these tools are also useful in everyday work. Therefore, it's worth
 describing them so as not to reinvent the wheel in case of need.
 
 # Any as in any type
@@ -49,7 +55,7 @@ describing them so as not to reinvent the wheel in case of need.
 `EnTT` offers its own `any` type. It may seem redundant considering that C++17
 introduced `std::any`, but it is not (hopefully).<br/>
 First of all, the _type_ returned by an `std::any` is a const reference to an
-`std::type_info`, an implementation defined class that is not something everyone
+`std::type_info`, an implementation defined class that's not something everyone
 wants to see in a software. Furthermore, there is no way to bind it to the type
 system of the library and therefore with its integrated RTTI support.
 
@@ -68,25 +74,22 @@ entt::any empty{};
 // a container for an int
 entt::any any{0};
 
-// in place type construction
-entt::any in_place_type{std::in_place_type<int>, 42};
-
-// take ownership of already existing, dynamically allocated objects
-entt::any in_place{std::in_place, std::make_unique<int>(42).release()};
+// in place construction
+entt::any in_place{std::in_place_type<int>, 42};
 ```
 
-Alternatively, the `make_any` function serves the same purpose. It requires to
-always be explicit about the type and does not support taking ownership:
+Alternatively, the `make_any` function serves the same purpose but requires to
+always be explicit about the type:
 
 ```cpp
 entt::any any = entt::make_any<int>(42);
 ```
 
-In all cases, the `any` class takes the burden of destroying the contained
+In both cases, the `any` class takes the burden of destroying the contained
 element when required, regardless of the storage strategy used for the specific
 object.<br/>
-Furthermore, an instance of `any` is not tied to an actual type. Therefore, the
-wrapper is reconfigured when it is assigned a new object of a type other than
+Furthermore, an instance of `any` isn't tied to an actual type. Therefore, the
+wrapper is reconfigured when it's assigned a new object of a type other than
 the one it contains.
 
 There is also a way to directly assign a value to the variable contained by an
@@ -118,8 +121,8 @@ The type is also used internally when comparing two `any` objects:
 if(any == empty) { /* ... */ }
 ```
 
-In this case, before proceeding with a comparison, it is verified that the
-_type_ of the two objects is actually the same.<br/>
+In this case, before proceeding with a comparison, it's verified that the _type_
+of the two objects is actually the same.<br/>
 Refer to the `EnTT` type system documentation for more details about how
 `type_info` works and the possible risks of a comparison.
 
@@ -138,9 +141,9 @@ any.emplace<const int &>(value);
 
 In other words, whenever `any` is explicitly told to construct an _alias_, it
 acts as a pointer to the original instance rather than making a copy of it or
-moving it internally. The contained object is never destroyed, and users must
+moving it internally. The contained object is never destroyed and users must
 ensure that its lifetime exceeds that of the container.<br/>
-Similarly, it is possible to create non-owning copies of `any` from an existing
+Similarly, it's possible to create non-owning copies of `any` from an existing
 object:
 
 ```cpp
@@ -148,12 +151,12 @@ object:
 entt::any ref = other.as_ref();
 ```
 
-In this case, it does not matter if the original container actually holds an
+In this case, it doesn't matter if the original container actually holds an
 object or is as a reference for unmanaged elements already. The new instance
-thus created does not create copies and only serves as a reference for the
+thus created doesn't create copies and only serves as a reference for the
 original item.
 
-It is worth mentioning that, while everything works transparently when it comes
+It's worth mentioning that, while everything works transparently when it comes
 to non-const references, there are some exceptions when it comes to const
 references.<br/>
 In particular, the `data` member function invoked on a non-const instance of
@@ -161,9 +164,9 @@ In particular, the `data` member function invoked on a non-const instance of
 
 To cast an instance of `any` to a type, the library offers a set of `any_cast`
 functions in all respects similar to their most famous counterparts.<br/>
-The only difference is that, in the case of `EnTT`, they will not raise
-exceptions but will only trigger an assert in debug mode, otherwise resulting in
-undefined behavior in case of misuse in release mode.
+The only difference is that, in the case of `EnTT`, they won't raise exceptions
+but will only trigger an assert in debug mode, otherwise resulting in undefined
+behavior in case of misuse in release mode.
 
 ## Small buffer optimization
 
@@ -188,8 +191,8 @@ and always dynamically allocates objects (except for aliasing cases).
 
 The alignment requirement is optional and by default the most stringent (the
 largest) for any object whose size is at most equal to the one provided.<br/>
-It is provided as an optional second parameter following the desired size for
-the internal storage:
+It's provided as an optional second parameter following the desired size for the
+internal storage:
 
 ```cpp
 using my_any = entt::basic_any<sizeof(double[4]), alignof(double[4])>;
@@ -199,22 +202,6 @@ The `basic_any` class template inspects the alignment requirements in each case,
 even when not provided and may decide not to use the small buffer optimization
 in order to meet them.
 
-# Bit
-
-Finding out the population count of an unsigned integral value (`popcount`),
-whether a number is a power of two or not (`has_single_bit`) as well as the next
-power of two given a random value (`next_power_of_two`) can be useful.<br/>
-For example, it helps to allocate memory in pages having a size suitable for the
-fast modulus:
-
-```cpp
-const std::size_t result = entt::fast_mod(value, modulus);
-```
-
-Where `modulus` is necessarily a power of two. Perhaps not everyone knows that
-this type of operation is far superior in terms of performance to the basic
-modulus and for this reason preferred in many areas.
-
 # Compressed pair
 
 Primarily designed for internal use and far from being feature complete, the
@@ -234,16 +221,16 @@ entt::compressed_pair pair{0, 3.};
 pair.first() = 42;
 ```
 
-There is not much to describe then. It is recommended to rely on documentation
-and intuition. At the end of the day, it is just a pair and nothing more.
+There isn't much to describe then. It's recommended to rely on documentation and
+intuition. At the end of the day, it's just a pair and nothing more.
 
 # Enum as bitmask
 
-Sometimes it is useful to be able to use enums as bitmasks. However, enum
-classes are not really suitable for the purpose. Main problem is that they do
-not convert implicitly to their underlying type.<br/>
+Sometimes it's useful to be able to use enums as bitmasks. However, enum classes
+aren't really suitable for the purpose. Main problem is that they don't convert
+implicitly to their underlying type.<br/>
 The choice is then between using old-fashioned enums (with all their problems
-that I do not want to discuss here) or writing _ugly_ code.
+that I don't want to discuss here) or writing _ugly_ code.
 
 Fortunately, there is also a third way: adding enough operators in the global
 scope to treat enum classes as bitmasks transparently.<br/>
@@ -276,7 +263,7 @@ struct entt::enum_as_bitmask<my_flag>
 ```
 
 This is handy when dealing with enum classes defined by third party libraries
-and over which the user has no control. However, it is also verbose and can be
+and over which the user has no control. However, it's also verbose and can be
 avoided by adding a specific value to the enum class itself:
 
 ```cpp
@@ -339,7 +326,7 @@ entt::hashed_string str{orig.c_str()};
 const auto hash = entt::hashed_string::value(orig.c_str());
 ```
 
-This possibility should not be exploited in tight loops, since the computation
+This possibility shouldn't be exploited in tight loops, since the computation
 takes place at runtime and no longer at compile-time. It could therefore affect
 performance to some degrees.
 
@@ -362,16 +349,16 @@ The hash type of `hashed_wstring` is the same as its counterpart.
 The hashed string class uses FNV-1a internally to hash strings. Because of the
 _pigeonhole principle_, conflicts are possible. This is a fact.<br/>
 There is no silver bullet to solve the problem of conflicts when dealing with
-hashing functions. In this case, the best solution is likely to give up. That is
+hashing functions. In this case, the best solution is likely to give up. That's
 all.<br/>
-After all, human-readable unique identifiers are not something strictly defined
+After all, human-readable unique identifiers aren't something strictly defined
 and over which users have not the control. Choosing a slightly different
 identifier is probably the best solution to make the conflict disappear in this
 case.
 
 # Iterators
 
-Writing and working with iterators is not always easy. More often than not it
+Writing and working with iterators isn't always easy. More often than not it
 also leads to duplicated code.<br/>
 `EnTT` tries to overcome this problem by offering some utilities designed to
 make this hard work easier.
@@ -379,12 +366,12 @@ make this hard work easier.
 ## Input iterator pointer
 
 When writing an input iterator that returns in-place constructed values if
-dereferenced, it is not always straightforward to figure out what `value_type`
-is and how to make it behave like a full-fledged pointer.<br/>
+dereferenced, it's not always straightforward to figure out what `value_type` is
+and how to make it behave like a full-fledged pointer.<br/>
 Conversely, it would be very useful to have an `operator->` available on the
 iterator itself that always works without too much complexity.
 
-The input iterator pointer is meant for this. It is a small class that wraps the
+The input iterator pointer is meant for this. It's a small class that wraps the
 in-place constructed value and adds some functions on top of it to make it
 suitable for use with input iterators: 
 
@@ -436,7 +423,7 @@ _iterable_ object with all the expected methods like `begin`, `end` and whatnot.
 
 The library uses this class extensively.<br/>
 Think for example of views, which can be iterated to access entities but also
-offer a method for obtaining an iterable object that returns tuples of entities
+offer a method of obtaining an iterable object that returns tuples of entities
 and components at once.<br/>
 Another example is the registry class which allows users to iterate its storage
 by returning an iterable object for the purpose.
@@ -452,13 +439,29 @@ everyday problems.
 The former are very specific and for niche problems. These are tools designed to
 unwrap fancy or plain pointers (`to_address`) or to help forget the meaning of
 acronyms like _POCCA_, _POCMA_ or _POCS_.<br/>
-I will not describe them here in detail. Instead, I recommend reading the inline
+I won't describe them here in detail. Instead, I recommend reading the inline
 documentation to those interested in the subject.
 
+## Power of two and fast modulus
+
+Finding out if a number is a power of two (`is_power_of_two`) or what the next
+power of two is given a random value (`next_power_of_two`) is very useful at
+times.<br/>
+For example, it helps to allocate memory in pages having a size suitable for the
+fast modulus:
+
+```cpp
+const std::size_t result = entt::fast_mod(value, modulus);
+```
+
+Where `modulus` is necessarily a power of two. Perhaps not everyone knows that
+this type of operation is far superior in terms of performance to the basic
+modulus and for this reason preferred in many areas.
+
 ## Allocator aware unique pointers
 
 A nasty thing in C++ (at least up to C++20) is the fact that shared pointers
-support allocators while unique pointers do not.<br/>
+support allocators while unique pointers don't.<br/>
 There is a proposal at the moment that also shows (among the other things) how
 this can be implemented without any compiler support.
 
@@ -509,9 +512,9 @@ library or that will never be.
 
 Runtime type identification support (or RTTI) is one of the most frequently
 disabled features in the C++ world, especially in the gaming sector. Regardless
-of the reasons for this, it is often a shame not to be able to rely on opaque
+of the reasons for this, it's often a shame not to be able to rely on opaque
 type information at runtime.<br/>
-The library tries to fill this gap by offering a built-in system that does not
+The library tries to fill this gap by offering a built-in system that doesn't
 serve as a replacement but comes very close to being one and offers similar
 information to that provided by its counterpart.
 
@@ -523,7 +526,7 @@ Basically, the whole system relies on a handful of classes. In particular:
   auto index = entt::type_index<a_type>::value();
   ```
 
-  The returned value is not guaranteed to be stable across different runs.<br/>
+  The returned value isn't guaranteed to be stable across different runs.<br/>
   However, it can be very useful as index in associative and unordered
   associative containers or for positional accesses in a vector or an array.
   
@@ -551,8 +554,8 @@ Basically, the whole system relies on a handful of classes. In particular:
   ```
 
   In general, the `value` function exposed by `type_hash` is also `constexpr`
-  but this is not guaranteed for all compilers and platforms (although it is
-  valid with the most well-known and popular ones).
+  but this isn't guaranteed for all compilers and platforms (although it's valid
+  with the most well-known and popular ones).
 
   This function **can** use non-standard features of the language for its own
   purposes. This makes it possible to provide compile-time identifiers that
@@ -574,7 +577,7 @@ Basically, the whole system relies on a handful of classes. In particular:
 
   This value is extracted from some information generally made available by the
   compiler in use. Therefore, it may differ depending on the compiler and may be
-  empty in the event that this information is not available.<br/>
+  empty in the event that this information isn't available.<br/>
   For example, given the following class:
 
   ```cpp
@@ -586,7 +589,7 @@ Basically, the whole system relies on a handful of classes. In particular:
   Most of the time the name is also retrieved at compile-time and is therefore
   always returned through an `std::string_view`. Users can easily access it and
   modify it as needed, for example by removing the word `struct` to normalize
-  the result. `EnTT` does not do this for obvious reasons, since it would be
+  the result. `EnTT` doesn't do this for obvious reasons, since it would be
   creating a new string at runtime otherwise.
 
   This function **can** use non-standard features of the language for its own
@@ -602,8 +605,8 @@ similar to that made available by the standard library.
 
 ### Type info
 
-The `type_info` class is not a drop-in replacement for `std::type_info` but can
-provide similar information which are not implementation defined and do not
+The `type_info` class isn't a drop-in replacement for `std::type_info` but can
+provide similar information which are not implementation defined and don't
 require to enable RTTI.<br/>
 Therefore, they can sometimes be even more reliable than those obtained
 otherwise.
@@ -676,7 +679,7 @@ described above.
 Since the default non-standard, compile-time implementation of `type_hash` makes
 use of hashed strings, it may happen that two types are assigned the same hash
 value.<br/>
-In fact, although this is quite rare, it is not entirely excluded.
+In fact, although this is quite rare, it's not entirely excluded.
 
 Another case where two types are assigned the same identifier is when classes
 from different contexts (for example two or more libraries loaded at runtime)
@@ -685,9 +688,8 @@ value for the two types.<br/>
 Fortunately, there are several easy ways to deal with this:
 
 * The most trivial one is to define the `ENTT_STANDARD_CPP` macro. Runtime
-  identifiers do not suffer from the same problem in fact. However, this
-  solution does not work well with a plugin system, where the libraries are not
-  linked.
+  identifiers don't suffer from the same problem in fact. However, this solution
+  doesn't work well with a plugin system, where the libraries aren't linked.
 
 * Another possibility is to specialize the `type_name` class for one of the
   conflicting types, in order to assign it a custom identifier. This is probably
@@ -696,8 +698,8 @@ Fortunately, there are several easy ways to deal with this:
 * A fully customized identifier generation policy (based for example on enum
   classes or preprocessing steps) may represent yet another option.
 
-These are just some examples of possible approaches to the problem, but there
-are many others. As already mentioned above, since users have full control over
+These are just some examples of possible approaches to the problem but there are
+many others. As already mentioned above, since users have full control over
 their types, this problem is in any case easy to solve and should not worry too
 much.<br/>
 In all likelihood, it will never happen to run into a conflict anyway.
@@ -713,10 +715,10 @@ offered by this module.
 ### Size of
 
 The standard operator `sizeof` complains if users provide it with functions or
-incomplete types. On the other hand, it is guaranteed that its result is always
+incomplete types. On the other hand, it's guaranteed that its result is always
 non-zero, even if applied to an empty class type.<br/>
 This small class combines the two and offers an alternative to `sizeof` that
-works under all circumstances, returning zero if the type is not supported:
+works under all circumstances, returning zero if the type isn't supported:
 
 ```cpp
 const auto size = entt::size_of_v<void>;
@@ -751,7 +753,7 @@ using type = entt::constness_as_t<dst_type, const src_type>;
 ```
 
 The trait is subject to the rules of the language. For example, _transferring_
-constness between references will not give the desired effect.
+constness between references won't give the desired effect.
 
 ### Member class type
 
@@ -771,7 +773,7 @@ A utility to quickly find the n-th argument of a function, member function or
 data member (for blind operations on opaque types):
 
 ```cpp
-using type = entt::nth_argument_t<1u, decltype(&clazz::member)>;
+using type = entt::nth_argument_t<1u, &clazz::member>;
 ```
 
 Disambiguation of overloaded functions is the responsibility of the user, should
@@ -809,7 +811,7 @@ where types would be required otherwise. As an example:
 registry.emplace<entt::tag<"enemy"_hs>>(entity);
 ```
 
-However, this is not the only permitted use. Literally any value convertible to
+However, this isn't the only permitted use. Literally any value convertible to
 `id_type` is a good candidate, such as the named constants of an unscoped enum.
 
 ### Type list and value list
@@ -831,7 +833,7 @@ type list:
 * `type_list_diff[_t]` to remove types from type lists.
 * `type_list_transform[_t]` to _transform_ a range and create another type list.
 
-I am also pretty sure that more and more utilities will be added over time as
+I'm also pretty sure that more and more utilities will be added over time as
 needs become apparent.<br/>
 Many of these functionalities also exist in their version dedicated to value
 lists. We therefore have `value_list_element[_v]` as well as
@@ -839,11 +841,11 @@ lists. We therefore have `value_list_element[_v]` as well as
 
 # Unique sequential identifiers
 
-Sometimes it is useful to be able to give unique, sequential numeric identifiers
+Sometimes it's useful to be able to give unique, sequential numeric identifiers
 to types either at compile-time or runtime.<br/>
-There are plenty of different solutions for this out there, and I could have
-used one of them. However, I decided to spend my time to define a couple of
-tools that fully embrace what modern C++ has to offer.
+There are plenty of different solutions for this out there and I could have used
+one of them. However, I decided to spend my time to define a couple of tools
+that fully embraces what the modern C++ has to offer.
 
 ## Compile-time generator
 
@@ -873,13 +875,12 @@ contains a numeric identifier for the given type. It can be used in any context
 where constant expressions are required.
 
 As long as the list remains unchanged, identifiers are also guaranteed to be
-stable across different runs. If used in a production environment where a type
-needs to be removed, a placeholder can help to leave the other identifiers the
-same:
+stable across different runs. In case they have been used in a production
+environment and a type has to be removed, one can just use a placeholder to
+leave the other identifiers unchanged:
 
 ```cpp
-template<typename>
-struct ignore_type {};
+template<typename> struct ignore_type {};
 
 using id = entt::ident<
     a_type_still_valid,
@@ -888,7 +889,7 @@ using id = entt::ident<
 >;
 ```
 
-Perhaps a bit ugly to see in a codebase, but it gets the job done at least.
+Perhaps a bit ugly to see in a codebase but it gets the job done at least.
 
 ## Runtime generator
 
@@ -910,17 +911,17 @@ numeric identifier for the given type.<br/>
 The generator is customizable, so as to get different _sequences_ for different
 purposes if needed.
 
-Identifiers are not guaranteed to be stable across different runs. Indeed it
+Identifiers aren't guaranteed to be stable across different runs. Indeed it
 mostly depends on the flow of execution.
 
 # Utilities
 
-It is not possible to escape the temptation to add utilities of some kind to a
+It's not possible to escape the temptation to add utilities of some kind to a
 library. In fact, `EnTT` also provides a handful of tools to simplify the
 life of developers:
 
 * `entt::identity`: the identity function object that will be available with
-  C++20. It returns its argument unchanged and nothing more. It is useful as a
+  C++20. It returns its argument unchanged and nothing more. It's useful as a
   sort of _do nothing_ function in template programming.
 
 * `entt::overload`: a tool to disambiguate different overloads from their
@@ -966,8 +967,7 @@ life of developers:
   callable object that supports multiple types at once.
 
 * `entt::y_combinator`: this is a C++ implementation of **the** _y-combinator_.
-  If it is not clear what it is, there is probably no need for this
-  utility.<br/>
+  If it's not clear what it is, there is probably no need for this utility.<br/>
   Below is a small example to show its use:
 
   ```cpp
@@ -978,9 +978,9 @@ life of developers:
   const auto result = gauss(3u);
   ```
 
-  Maybe convoluted at first glance but certainly effective. Unfortunately,
-  the language does not make it possible to do much better.
+  Maybe convoluted at a first glance but certainly effective. Unfortunately,
+  the language doesn't make it possible to do much better.
 
 This is a rundown of the (actually few) utilities made available by `EnTT`. The
-list will probably grow over time, but the size of each will remain rather
-small, as has been the case so far.
+list will probably grow over time but the size of each will remain rather small,
+as has been the case so far.

docs/md/faq.md

@@ -1,5 +1,8 @@
 # Frequently Asked Questions
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 # Table of Contents
 
 * [Introduction](#introduction)
@@ -7,17 +10,20 @@
   * [Why is my debug build on Windows so slow?](#why-is-my-debug-build-on-windows-so-slow)
   * [How can I represent hierarchies with my components?](#how-can-i-represent-hierarchies-with-my-components)
   * [Custom entity identifiers: yay or nay?](#custom-entity-identifiers-yay-or-nay)
-  * [Warning C4003: the min, the max and the macro](#warning-c4003-the-min-the-max-and-the-macro)
+  * [Warning C4307: integral constant overflow](#warning-C4307-integral-constant-overflow)
+  * [Warning C4003: the min, the max and the macro](#warning-C4003-the-min-the-max-and-the-macro)
   * [The standard and the non-copyable types](#the-standard-and-the-non-copyable-types)
   * [Which functions trigger which signals](#which-functions-trigger-which-signals)
-  * [Duplicate storage for the same component](#duplicate-storage-for-the-same-component)
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # Introduction
 
-This is a constantly updated section where I am trying to put the answers to the
+This is a constantly updated section where I'm trying to put the answers to the
 most frequently asked questions.<br/>
-If you do not find your answer here, there are two cases: nobody has done it
-yet, or this section needs updating. In both cases, you can
+If you don't find your answer here, there are two cases: nobody has done it yet
+or this section needs updating. In both cases, you can
 [open a new issue](https://github.com/skypjack/entt/issues/new) or enter either
 the [gitter channel](https://gitter.im/skypjack/entt) or the
 [discord server](https://discord.gg/5BjPWBd) to ask for help.<br/>
@@ -29,12 +35,12 @@ part of the documentation.
 ## Why is my debug build on Windows so slow?
 
 `EnTT` is an experimental project that I also use to keep me up-to-date with the
-latest revision of the language and the standard library. For this reason, it is
-likely that some classes you are working with are using standard containers
-under the hood.<br/>
-Unfortunately, it is known that the standard containers are not particularly
+latest revision of the language and the standard library. For this reason, it's
+likely that some classes you're working with are using standard containers under
+the hood.<br/>
+Unfortunately, it's known that the standard containers aren't particularly
 performing in debugging (the reasons for this go beyond this document) and are
-even less so on Windows, apparently. Fortunately, this can also be mitigated a
+even less so on Windows apparently. Fortunately this can also be mitigated a
 lot, achieving good results in many cases.
 
 First of all, there are two things to do in a Windows project:
@@ -53,7 +59,7 @@ macro to disable internal debug checks in `EnTT`:
 #define ENTT_ASSERT(...) ((void)0)
 ```
 
-These asserts are introduced to help the users, but they require access to the
+These asserts are introduced to help the users but they require to access to the
 underlying containers and therefore risk ruining the performance in some cases.
 
 With these changes, debug performance should increase enough in most cases. If
@@ -64,15 +70,15 @@ preferably `O1`.
 
 This is one of the first questions that anyone makes when starting to work with
 the entity-component-system architectural pattern.<br/>
-There are several approaches to the problem, and the best one depends mainly on
-the real problem one is facing. In all cases, how to do it does not strictly
+There are several approaches to the problem and the best one depends mainly on
+the real problem one is facing. In all cases, how to do it doesn't strictly
 depend on the library in use, but the latter certainly allows or not different
 techniques depending on how the data are laid out.
 
 I tried to describe some of the approaches that fit well with the model of
 `EnTT`. [This](https://skypjack.github.io/2019-06-25-ecs-baf-part-4/) is the
 first post of a series that tries to _explore_ the problem. More will probably
-come in the future.<br/>
+come in future.<br/>
 In addition, `EnTT` also offers the possibility to create stable storage types
 and therefore have pointer stability for one, all or some components. This is by
 far the most convenient solution when it comes to creating hierarchies and
@@ -83,7 +89,7 @@ what concerns the `component_traits` class for further details.
 
 Custom entity identifiers are definitely a good idea in two cases at least:
 
-* If `std::uint32_t` is not large enough for your purposes, since this is the
+* If `std::uint32_t` isn't large enough for your purposes, since this is the
   underlying type of `entt::entity`.
 
 * If you want to avoid conflicts when using multiple registries.
@@ -98,14 +104,40 @@ enum class entity: std::uint32_t {};
 
 There is no limit to the number of identifiers that can be defined.
 
+## Warning C4307: integral constant overflow
+
+According to [this](https://github.com/skypjack/entt/issues/121) issue, using a
+hashed string under VS (toolset v141) could generate a warning.<br/>
+First of all, I want to reassure you: it's expected and harmless. However, it
+can be annoying.
+
+To suppress it and if you don't want to suppress all the other warnings as well,
+here is a workaround in the form of a macro:
+
+```cpp
+#if defined(_MSC_VER)
+#define HS(str) __pragma(warning(suppress:4307)) entt::hashed_string{str}
+#else
+#define HS(str) entt::hashed_string{str}
+#endif
+```
+
+With an example of use included:
+
+```cpp
+constexpr auto identifier = HS("my/resource/identifier");
+```
+
+Thanks to [huwpascoe](https://github.com/huwpascoe) for the courtesy.
+
 ## Warning C4003: the min, the max and the macro
 
 On Windows, a header file defines two macros `min` and `max` which may result in
 conflicts with their counterparts in the standard library and therefore in
 errors during compilation.
 
-It is a pretty big problem. However, fortunately it is not a problem of `EnTT`
-and there is a fairly simple solution to it.<br/>
+It's a pretty big problem but fortunately it's not a problem of `EnTT` and there
+is a fairly simple solution to it.<br/>
 It consists in defining the `NOMINMAX` macro before including any other header
 so as to get rid of the extra definitions:
 
@@ -119,9 +151,9 @@ more details.
 ## The standard and the non-copyable types
 
 `EnTT` uses internally the trait `std::is_copy_constructible_v` to check if a
-component is actually copyable. However, this trait does not really check
-whether a type is actually copyable. Instead, it just checks that a suitable
-copy constructor and copy operator exist.<br/>
+component is actually copyable. However, this trait doesn't really check whether
+a type is actually copyable. Instead, it just checks that a suitable copy
+constructor and copy operator exist.<br/>
 This can lead to surprising results due to some idiosyncrasies of the standard.
 
 For example, `std::vector` defines a copy constructor that is conditionally
@@ -163,7 +195,7 @@ to mitigate the problem makes it manageable.
 
 Storage classes offer three _signals_ that are emitted following specific
 operations. Maybe not everyone knows what these operations are, though.<br/>
-If this is not clear, below you can find a _vademecum_ for this purpose:
+If this isn't clear, below you can find a _vademecum_ for this purpose:
 
 * `on_created` is invoked when a component is first added (neither modified nor 
   replaced) to an entity.
@@ -174,35 +206,10 @@ If this is not clear, below you can find a _vademecum_ for this purpose:
   from an entity.
 
 Among the most controversial functions can be found `emplace_or_replace` and
-`destroy`. However, following the above rules, it is quite simple to know what 
+`destroy`. However, following the above rules, it's quite simple to know what 
 will happen.<br/>
 In the first case, `on_created` is invoked if the entity has not the component,
 otherwise the latter is replaced and therefore `on_update` is triggered. As for
 the second case, components are removed from their entities and thus freed when
 they are recycled. It means that `on_destroyed` is triggered for every component 
 owned by the entity that is destroyed.
-
-## Duplicate storage for the same component
-
-It is rare, but you can see double sometimes, especially when it comes to
-storage. This can be caused by a conflict in the hash assigned to the various
-component types (one of a kind) or by bugs in your compiler
-([more common](https://github.com/skypjack/entt/issues/1063) apparently).<br/>
-Regardless of the cause, `EnTT` offers a customization point that also serves as
-a solution in this case:
-
-```cpp
-template<>
-struct entt::type_hash<Type> final {
-    [[nodiscard]] static constexpr id_type value() noexcept {
-        return hashed_string::value("Type");
-    }
-
-    [[nodiscard]] constexpr operator id_type() const noexcept {
-        return value();
-    }
-};
-```
-
-Specializing `type_hash` directly bypasses the default implementation offered by
-`EnTT`, thus avoiding any possible conflicts or compiler bugs.

docs/md/graph.md

@@ -1,5 +1,8 @@
 # Crash Course: graph
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 # Table of Contents
 
 * [Introduction](#introduction)
@@ -11,24 +14,26 @@
   * [Fake resources and order of execution](#fake-resources-and-order-of-execution)
   * [Sync points](#sync-points)
   * [Execution graph](#execution-graph)
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # Introduction
 
-`EnTT` does not aim to offer everything one needs to work with graphs.
-Therefore, anyone looking for this in the _graph_ submodule will be
-disappointed.<br/>
+`EnTT` doesn't aim to offer everything one needs to work with graphs. Therefore,
+anyone looking for this in the _graph_ submodule will be disappointed.<br/>
 Quite the opposite is true though. This submodule is minimal and contains only
 the data structures and algorithms strictly necessary for the development of
 some tools such as the _flow builder_.
 
 # Data structures
 
-As anticipated in the introduction, the aim is not to offer all possible data
+As anticipated in the introduction, the aim isn't to offer all possible data
 structures suitable for representing and working with graphs. Many will likely
-be added or refined over time. However, I want to discourage anyone expecting
+be added or refined over time. However I want to discourage anyone expecting
 tight scheduling on the subject.<br/>
 The data structures presented in this section are mainly useful for the
-development and support of some tools that are also part of the same submodule.
+development and support of some tools which are also part of the same submodule.
 
 ## Adjacency matrix
 
@@ -109,11 +114,11 @@ Both the functions expect the vertex to visit (that is, to return the in- or
 out-edges for) as an argument.<br/>
 Finally, the adjacency matrix is an allocator-aware container and offers most of
 the functionalities one would expect from this type of containers, such as
-`clear` or `get_allocator` and so on.
+`clear` or 'get_allocator` and so on.
 
 ## Graphviz dot language
 
-As it is one of the most popular formats, the library offers minimal support for
+As it's one of the most popular formats, the library offers minimal support for
 converting a graph to a Graphviz dot snippet.<br/>
 The simplest way is to pass both an output stream and a graph to the `dot`
 function:
@@ -123,7 +128,7 @@ std::ostringstream output{};
 entt::dot(output, adjacency_matrix);
 ```
 
-It is also possible to provide a callback to which the vertices are passed and
+It's also possible to provide a callback to which the vertices are passed and
 which can be used to add (`dot`) properties to the output as needed:
 
 ```cpp
@@ -140,7 +145,7 @@ externally managed data to the graph being converted.
 # Flow builder
 
 A flow builder is used to create execution graphs from tasks and resources.<br/>
-The implementation is as generic as possible and does not bind to any other part
+The implementation is as generic as possible and doesn't bind to any other part
 of the library.
 
 This class is designed as a sort of _state machine_ to which a specific task is
@@ -166,7 +171,7 @@ particular data structure. On the other hand, it requires the user to keep track
 of the association between identifiers and operations or actual data.
 
 Once a flow builder is created (which requires no constructor arguments), the
-first thing to do is to bind a task. This tells the builder _who_ intends to
+first thing to do is to bind a task. This tells to the builder _who_ intends to
 consume the resources that are specified immediately after:
 
 ```cpp
@@ -176,15 +181,15 @@ builder.bind("task_1"_hs);
 
 The example uses the `EnTT` hashed string to generate an identifier for the
 task.<br/>
-Indeed, the use of `id_type` as an identifier type is not by accident. In fact,
-it matches well with the internal hashed string class. Moreover, it is also the
+Indeed, the use of `id_type` as an identifier type isn't by accident. In fact,
+it matches well with the internal hashed string class. Moreover, it's also the
 same type returned by the hash function of the internal RTTI system, in case the
 user wants to rely on that.<br/>
 However, being an integral value, it leaves the user full freedom to rely on his
 own tools if necessary.
 
-Once a task is associated with the flow builder, it has also assigned read-only
-or read-write resources as appropriate:
+Once a task is associated with the flow builder, it's also assigned read-only or
+read-write resources as appropriate:
 
 ```cpp
 builder
@@ -195,7 +200,7 @@ builder
         .rw("resource_2"_hs)
 ```
 
-As mentioned, many functions return the builder itself, and it is therefore easy
+As mentioned, many functions return the builder itself and it's therefore easy
 to concatenate the different calls.<br/>
 Also in the case of resources, they are identified by numeric values of type
 `id_type`. As above, the choice is not entirely random. This goes well with the
@@ -209,13 +214,13 @@ pair of iterators, so that one can pass a range of resources in one go.
 The `flow` class is resource based rather than task based. This means that graph
 generation is driven by resources and not by the order of _appearance_ of tasks
 during flow definition.<br/>
-Although this concept is particularly important, it is almost irrelevant for the
+Although this concept is particularly important, it's almost irrelevant for the
 vast majority of cases. However, it becomes relevant when _rebinding_ resources
 or tasks.
 
 In fact, nothing prevents rebinding elements to a flow.<br/>
 However, the behavior changes slightly from case to case and has some nuances
-that it is worth knowing about.
+that it's worth knowing about.
 
 Directly rebinding a resource without the task being replaced trivially results
 in the task's access mode for that resource being updated:
@@ -226,7 +231,7 @@ builder.bind("task"_hs).rw("resource"_hs).ro("resource"_hs)
 
 In this case, the resource is accessed in read-only mode, regardless of the
 first call to `rw`.<br/>
-Behind the scenes, the call does not actually _replace_ the previous one but is
+Behind the scenes, the call doesn't actually _replace_ the previous one but is
 queued after it instead, overwriting it when generating the graph. Thus, a large
 number of resource rebindings may even impact processing times (very difficult
 to observe but theoretically possible).
@@ -247,12 +252,12 @@ builder
 ```
 
 What happens here is that the resource first _sees_ a read-only access request
-from the first task, then a read-only request from the second task and finally
-a read-write request from the first task.<br/>
+from the first task, then a read-write request from the second task and finally
+a new read-only request from the first task.<br/>
 Although this definition would probably be counted as an error, the resulting
-graph may be unexpected. In fact, this consists of a single edge outgoing from
+graph may be unexpected. This in fact consists of a single edge outgoing from
 the second task and directed to the first task.<br/>
-To intuitively understand what happens, it is enough to think of the fact that a
+To intuitively understand what happens, it's enough to think of the fact that a
 task never has an edge pointing to itself.
 
 While not obvious, this approach has its pros and cons like any other solution.
@@ -273,22 +278,22 @@ As expected, this definition leads to the creation of two edges that define a
 loop between the two tasks.
 
 As a general rule, rebinding resources and tasks is highly discouraged because
-it could lead to subtle bugs if users do not know what they are doing.<br/>
+it could lead to subtle bugs if users don't know what they're doing.<br/>
 However, once the mechanisms of resource-based graph generation are understood,
-it can offer to the expert user flexibility and a range of possibilities
+it can offer to the expert user a flexibility and a range of possibilities
 otherwise inaccessible.
 
 ## Fake resources and order of execution
 
-The flow builder does not offer the ability to specify when a task should run
+The flow builder doesn't offer the ability to specify when a task should execute
 before or after another task.<br/>
 In fact, the order of _registration_ on the resources also determines the order
 in which the tasks are processed during the generation of the execution graph.
 
 However, there is a way to _force_ the execution order of two processes.<br/>
 Briefly, since accessing a resource in opposite modes requires sequential rather
-than parallel scheduling, it is possible to make use of fake resources to rule
-on the execution order:
+than parallel scheduling, it's possible to make use of fake resources to rule on
+the execution order:
 
 ```cpp
 builder
@@ -306,7 +311,7 @@ builder
 This snippet forces the execution of `task_1` **before** `task_2` and `task_3`.
 This is due to the fact that the former sets a read-write requirement on a fake
 resource that the other tasks also want to access in read-only mode.<br/>
-Similarly, it is possible to force a task to run **after** a certain group:
+Similarly, it's possible to force a task to run **after** a certain group:
 
 ```cpp
 builder
@@ -323,22 +328,22 @@ builder
 
 In this case, since there are a number of processes that want to read a specific
 resource, they will do so in parallel by forcing `task_3` to run after all the
-other tasks.
+others tasks.
 
 ## Sync points
 
-Sometimes it is useful to assign the role of _sync point_ to a node.<br/>
+Sometimes it's useful to assign the role of _sync point_ to a node.<br/>
 Whether it accesses new resources or is simply a watershed, the procedure for
-assigning this role to a vertex is always the same. First it is tied to the flow
+assigning this role to a vertex is always the same. First it's tied to the flow
 builder, then the `sync` function is invoked:
 
 ```cpp
 builder.bind("sync_point"_hs).sync();
 ```
 
-The choice to assign an _identity_ to this type of node lies in the fact that,
+The choice to assign an _identity_ to this type of nodes lies in the fact that,
 more often than not, they also perform operations on resources.<br/>
-If this is not the case, it will still be possible to create no-op vertices to
+If this isn't the case, it will still be possible to create no-op vertices to
 which empty tasks are assigned.
 
 ## Execution graph
@@ -362,6 +367,6 @@ for(auto &&vertex: graph) {
 }
 ```
 
-Then it is possible to instantiate an execution graph by means of other
-functions such as `out_edges` to retrieve the children of a given task or
-`edges` to get the identifiers.
+Then it's possible to instantiate an execution graph by means of other functions
+such as `out_edges` to retrieve the children of a given task or `edges` to get
+the identifiers.

docs/md/lib.md

@@ -1,11 +1,17 @@
 # Push EnTT across boundaries
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 # Table of Contents
 
 * [Working across boundaries](#working-across-boundaries)
   * [Smooth until proven otherwise](#smooth-until-proven-otherwise)
   * [Meta context](#meta-context)
   * [Memory management](#memory-management)
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # Working across boundaries
 
@@ -20,10 +26,10 @@ Fortunately, nowadays `EnTT` works smoothly across boundaries.
 Many classes in `EnTT` make extensive use of type erasure for their purposes.
 This raises the need to identify objects whose type has been erased.<br/>
 The `type_hash` class template is how identifiers are generated and thus made
-available to the rest of the library. In general, this class arouses little
+available to the rest of the library. In general, this class doesn't arouse much
 interest. The only exception is when a conflict between identifiers occurs
-(definitely uncommon though) or when the default solution proposed by `EnTT` is
-not suitable for the user's purposes.<br/>
+(definitely uncommon though) or when the default solution proposed by `EnTT`
+isn't suitable for the user's purposes.<br/>
 The section dedicated to `type_info` contains all the details to get around the
 issue in a concise and elegant way. Please refer to the specific documentation.
 
@@ -31,20 +37,20 @@ When working with linked libraries, compile definitions `ENTT_API_EXPORT` and
 `ENTT_API_IMPORT` are to import or export symbols, so as to make everything work
 nicely across boundaries.<br/>
 On the other hand, everything should run smoothly when working with plugins or
-shared libraries that do not export any symbols.
+shared libraries that don't export any symbols.
 
 For those who need more details, the test suite contains many examples covering
 the most common cases (see the `lib` directory for all details).<br/>
-It goes without saying that it is impossible to cover **all** possible cases.
+It goes without saying that it's impossible to cover **all** possible cases.
 However, what is offered should hopefully serve as a basis for all of them.
 
 ## Meta context
 
 The runtime reflection system deserves a special mention when it comes to using
 it across boundaries.<br/>
-Since it is linked already to a static context to which the elements are
-attached and different contexts do not relate to each other, they must be
-_shared_ to allow the use of meta types across boundaries.
+Since it's linked already to a static context to which the elements are attached
+and different contexts don't relate to each other, they must be _shared_ to
+allow the use of meta types across boundaries.
 
 Fortunately, sharing a context is also trivial to do. First of all, the local
 one is acquired in the main space:
@@ -53,16 +59,16 @@ one is acquired in the main space:
 auto handle = entt::locator<entt::meta_ctx>::handle();
 ```
 
-Then, it is passed to the receiving space that sets it as its default context,
+Then, it's passed to the receiving space that sets it as its default context,
 thus discarding or storing aside the local one:
 
 ```cpp
 entt::locator<entt::meta_ctx>::reset(handle);
 ```
 
-From now on, both spaces refer to the same context and to it are all new meta
-types attached, no matter where they are created.<br/>
-Note that _replacing_ the main context does not also propagate changes across
+From now on, both spaces refer to the same context and on it are attached all
+new meta types, no matter where they are created.<br/>
+Note that _replacing_ the main context doesn't also propagate changes across
 boundaries. In other words, replacing a context results in the decoupling of the
 two sides and therefore a divergence in the contents.
 
@@ -81,10 +87,9 @@ is unknown to the former, a dedicated pool is created within the registry on
 first use.<br/>
 As one can guess, this pool is instantiated on a different side of the boundary
 from the `registry`. Therefore, the instance is now managing memory from
-different spaces, and this can quickly lead to crashes if not properly
-addressed.
+different spaces and this can quickly lead to crashes if not properly addressed.
 
-To overcome the risk, it is recommended to use well-defined interfaces that make
+To overcome the risk, it's recommended to use well-defined interfaces that make
 fundamental types pass through the boundaries, isolating the instances of the
 `EnTT` classes from time to time and as appropriate.<br/>
 Refer to the test suite for some examples, read the documentation available

docs/md/links.md

@@ -1,5 +1,8 @@
 # EnTT in Action
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 # Table of Contents
 
 * [Introduction](#introduction)
@@ -8,22 +11,25 @@
   * [Engines and the like](#engines-and-the-like)
   * [Articles, videos and blog posts](#articles-videos-and-blog-posts)
   * [Any Other Business](#any-other-business)
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # Introduction
 
 `EnTT` is widely used in private and commercial applications. I cannot even
 mention most of them because of some signatures I put on some documents time
 ago. Fortunately, there are also people who took the time to implement open
-source projects based on `EnTT` and did not hold back when it came to
-documenting them.
+source projects based on `EnTT` and didn't hold back when it came to documenting
+them.
 
 Below an incomplete list of games, applications and articles that can be used as
 a reference.<br/>
 Where I put the word _apparently_ means that the use of `EnTT` is documented but
-the authors did not make explicit announcements or contacted me directly.
+the authors didn't make explicit announcements or contacted me directly.
 
 If you know of other resources out there that are about `EnTT`, feel free to
-open an issue or a PR. I will be glad to add them to this page.<br/>
+open an issue or a PR and I'll be glad to add them to this page.<br/>
 I hope the following lists can grow much more in the future.
 
 # EnTT in Action
@@ -33,9 +39,6 @@ I hope the following lists can grow much more in the future.
   * [Minecraft](https://minecraft.net/en-us/attribution/) by
     [Mojang](https://mojang.com/): of course, **that** Minecraft, see the
     open source attributions page for more details.
-  * [Minecraft Legends](https://www.minecraft.net/it-it/about-legends) by
-    [Mojang](https://mojang.com/): an action strategy game where users have to
-    fight to defend the Overworld.
   * [Minecraft Earth](https://www.minecraft.net/en-us/about-earth) by
     [Mojang](https://mojang.com/): an augmented reality game for mobile, that
     lets users bring Minecraft into the real world.
@@ -48,11 +51,11 @@ I hope the following lists can grow much more in the future.
   * [Apparently](https://www.youtube.com/watch?v=P8xvOA3ikrQ&t=1105s)
     [Call of Duty: Vanguard](https://www.callofduty.com/vanguard) by
     [Sledgehammer Games](https://www.sledgehammergames.com/): I can neither
-    confirm nor deny, but there is a license I know in the credits.
+    confirm nor deny but there is a license I know in the credits.
   * Apparently [D&D Dark Alliance](https://darkalliance.wizards.com) by
     [Wizards of the Coast](https://company.wizards.com): your party, their
     funeral.
-  * [TiltedEvolution](https://github.com/tiltedphoques/TiltedEvolution) by
+  * [TiltedOnline](https://github.com/tiltedphoques/TiltedOnline) by
     [Tilted Phoques](https://github.com/tiltedphoques): Skyrim and Fallout 4 mod
     to play online.
   * [Antkeeper](https://github.com/antkeeper/antkeeper-source): an ant colony
@@ -97,20 +100,20 @@ I hope the following lists can grow much more in the future.
     by Quake.
   * [Destroid](https://github.com/tyrannicaltoucan/destroid): _one-bazillionth_
     arcade game about shooting dirty rocks in space, inspired by Asteroids.
-  * [Wanderer](https://github.com/albin-johansson/wanderer): a 2D
-    exploration-based indie game.
-  * [Spelunky® Classic remake](https://github.com/dbeef/spelunky-psp): a truly
+  * [Wanderer](https://github.com/albin-johansson/wanderer): a 2D exploration
+    based indie game.
+  * [Spelunky® Classic remake](https://github.com/dbeef/spelunky-psp): a truly
     multiplatform experience with a rewrite from scratch.
   * [CubbyTower](https://github.com/utilForever/CubbyTower): a simple tower
     defense game using C++ with Entity Component System (ECS).
   * [Runeterra](https://github.com/utilForever/Runeterra): Legends of Runeterra
     simulator using C++ with some reinforcement learning.
   * [Black Sun](https://store.steampowered.com/app/1670930/Black_Sun/): fly your
-    spaceship through a large 2D open world.
-  * [PokeMaster](https://github.com/utilForever/PokeMaster): Pokémon Battle
+    space ship through a large 2D open world.
+  * [PokeMaster](https://github.com/utilForever/PokeMaster): Pokemon Battle
     simulator using C++ with some reinforcement learning.
   * [HomeHearth](https://youtu.be/GrEWl8npL9Y): choose your hero, protect the
-    town, before it is too late.
+    town, before it's too late.
   * [City Builder Game](https://github.com/PhiGei2000/CityBuilderGame): a simple
     city-building game using C++ and OpenGL.
   * [BattleSub](https://github.com/bfeldpw/battlesub): two player 2D submarine
@@ -121,32 +124,9 @@ I hope the following lists can grow much more in the future.
     multi-player arcade shooter game prototype.
   * [Confetti Party](https://github.com/hexerei/entt-confetti): C++ sample
     application as a starting point using `EnTT` and `SDL2`.
-  * [Hellbound](https://buas.itch.io/hellbound): a top-down action rogue-like
-    where to fight colossal demons in procedurally generated levels of hell.
-  * [Saurian Sorcery](https://github.com/cajallen/spellbook): a tower defense
-    game where to assemble a tribe of lizards to defend against robot invaders.
-  * [robotfindskitten](https://github.com/autogalkin/robotfindskitten): a clone
-    of `robotfindskitten` inside `Notepad.exe`, powered by `EnTT`.
-  * [Orion](https://github.com/alekskoloch/Orion): Outer-space Research and
-    Interstellar Observation Network (a space shooter game).
-  * [EnTT Boids](https://github.com/DanielEliasib/entt_boids): a simple boids
-    implementation using `EnTT` and `Raylib`.
-  * [PalmRide: After Flight](https://store.steampowered.com/app/2812540/PalmRide_After_Flight/):
-    an on-rails shooter with retro outrun aesthetics.
-  * [Exhibition of Speed](https://store.steampowered.com/app/2947450/Exhibition_of_Speed/):
-    build your own car and go racing.
-  * [Lichgate](https://buas.itch.io/lichgate): top-down action rogue-like where
-    users unlock abilities to fight horde of enemies in an endless world.
-  * [Letalka](https://github.com/dviglo2d/dviglo2d/tree/main/games/letalka):
-    small demo game with ships and bullets flying everywhere on the screen.
-  * [Lichgate](https://buas.itch.io/lichgate): step into the robes of a powerful
-    mage determined to halt the relentless hordes of undead.
 
 ## Engines and the like:
 
-  * [Hazel Engine](https://github.com/TheCherno/Hazel): a work in progress
-    engine created by [The Cherno](https://github.com/TheCherno/Hazel) during
-    one of his most famous video series.
   * [Aether Engine](https://hadean.com/spatial-simulation/)
     [v1.1+](https://docs.hadean.com/v1.1/Licenses/) by
     [Hadean](https://hadean.com/): a library designed for spatially partitioning
@@ -192,7 +172,7 @@ I hope the following lists can grow much more in the future.
     framework in C++17 for backend development.
   * [Unity/EnTT](https://github.com/TongTungGiang/unity-entt): tech demo of a
     native simulation layer using `EnTT` and `Unity` as a rendering engine.
-  * [OverEngine](https://github.com/OverShifted/OverEngine): an overengineered
+  * [OverEngine](https://github.com/OverShifted/OverEngine): an over-engineered
     game engine.
   * [Electro](https://github.com/Electro-Technologies/Electro): high performance
     3D game engine with a high emphasis on rendering.
@@ -201,13 +181,13 @@ I hope the following lists can grow much more in the future.
   * [Becketron](https://github.com/Doctor-Foxling/Becketron): a game engine
     written mostly in C++.
   * [Spatial Engine](https://github.com/luizgabriel/Spatial.Engine): a
-    cross-platform engine created on top of Google's filament rendering engine.
+    cross-platform engine created on top of google's filament rendering engine.
   * [Kaguya](https://github.com/KaiH0717/Kaguya): D3D12 Rendering Engine.
   * [OpenAWE](https://github.com/OpenAWE-Project/OpenAWE): open implementation
     of the Alan Wake Engine.
   * [Nazara Engine](https://github.com/DigitalPulseSoftware/NazaraEngine): fast,
     cross-platform, object-oriented API to help in daily developer life.
-  * [Billy Engine](https://github.com/billy4479/BillyEngine): some kind of 2D
+  * [Billy Engine](https://github.com/billy4479/BillyEngine): some kind of a 2D
     engine based on `SDL2` and `EnTT`.
   * [Ducktape](https://github.com/DucktapeEngine/Ducktape): an open source C++
     2D & 3D game engine that focuses on being fast and powerful.
@@ -220,27 +200,7 @@ I hope the following lists can grow much more in the future.
     open-source engine for building 2D & 3D real-time rendering and interactive
     contents.
   * [Kengine](https://github.com/phisko/kengine): the _Koala engine_ is a game
-    engine entirely implemented as an entity-component-system.
-  * [Scion2D](https://github.com/dwjclark11/Scion2D): 2D game engine with
-    [YouTube series](https://www.youtube.com/playlist?list=PL3HUvSWOJR7XRDwVVQqqWO-zyyscb8L-v)
-    included.
-  * [EnTT Editor](https://github.com/TheDimin/EnttEditor): an editor for `EnTT`
-    libary that combines its built-in reflection system with `ImGui`.
-  * [Era Game Engine](https://github.com/EldarMuradov/EraGameEngine): a modern
-    ECS-based game engine.
-  * [Core SDK of Trollworks engine](https://github.com/trollworks/sdk-core): 2D
-    game engine based on procrastination.
-  * [Rocky](https://github.com/pelicanmapping/rocky): 3D geospatial application
-    engine.
-  * [Donner](https://github.com/jwmcglynn/donner): a modern C++20 SVG2 rendering
-    API with CSS3.
-  * [Coral Engine](https://github.com/GuusKemperman/CoralEngine): open-source
-    student engine with the tools to make games in C++ and Visual scripting.
-  * [Star Engine](https://github.com/HODAKdev/StarEngine): an Advanced C++
-    DirectX 11 game engine.
-  * [Darmok](https://github.com/miguelibero/darmok): another C++ game engine.
-  * [Magique](https://github.com/gk646/magique): 2D game engine for programmers
-    (or those yet to be).
+    engine entirely implemented as an entity-component-ystem.
 
 ## Articles, videos and blog posts:
 
@@ -267,22 +227,11 @@ I hope the following lists can grow much more in the future.
     - ... And so on.
       [Check out](https://www.youtube.com/channel/UCQ-W1KE9EYfdxhL6S4twUNw) the
       _Game Engine Series_ by The Cherno for more videos.
-  * [Game Engine series](https://www.youtube.com/@JADE-iteGames/videos) by
-    [dwjclark11](https://github.com/dwjclark11) (not just `EnTT` but a lot of
-    it):
-    - [Getting into ECS](https://youtu.be/k9CbonLopJU?si=za3Tisyc96_92DWM)
-    - [Creating ECS Wrapper Classes](https://youtu.be/yetyuMJRdbo?si=PJTkmap4Ysqbzb_M)
-    - [Runtime Reflection using EnTT meta](https://youtu.be/GrXV5A07GTY?si=fKdWTj9AOhnhtiXq)
-    - [Adding entt::meta and Sol2 bindings](https://youtu.be/IM55JgxOqFA?si=rsbb4AG_NVh4IUmD)
-      (with [part two](https://youtu.be/-PTt-b1tzRw?si=zPJ4vEluyheMcNgO) too)
-    - ... And so on.
-      [Check it out](https://www.youtube.com/playlist?list=PL3HUvSWOJR7XRDwVVQqqWO-zyyscb8L-v)
-      for more videos.
   * [Warmonger Dynasty devlog series](https://david-delassus.medium.com/list/warmonger-dynasty-devlogs-f64b71f556de)
     by [linkdd](https://github.com/linkdd): an interesting walkthrough of
     developing a game (also) with EnTT.
   * [Use EnTT When You Need An ECS](https://www.codingwiththomas.com/blog/use-entt-when-you-need-an-ecs)
-    by [Thomas](https://www.codingwiththomas.com/): I could not have said it
+    by [Thomas](https://www.codingwiththomas.com/): I couldn't have said it
     better.
   * [Space Battle: Huge edition](http://victor.madtriangles.com/code%20experiment/2018/06/11/post-ecs-battle-huge.html):
     huge space battle built entirely from scratch.
@@ -314,7 +263,7 @@ I hope the following lists can grow much more in the future.
 
   * [ArcGIS Runtime SDKs](https://developers.arcgis.com/arcgis-runtime/) by
     [Esri](https://www.esri.com/): they use `EnTT` for the internal ECS and the
-    cross-platform C++ rendering engine. The SDKs are used by a lot of
+    cross platform C++ rendering engine. The SDKs are utilized by a lot of
     enterprise custom apps, as well as by Esri for its own public applications
     such as
     [Explorer](https://play.google.com/store/apps/details?id=com.esri.explorer),
@@ -330,7 +279,7 @@ I hope the following lists can grow much more in the future.
   * [Project Lagrange](https://github.com/adobe/lagrange): a robust geometry
     processing library by [Adobe](https://github.com/adobe).
   * [AtomicDEX](https://github.com/KomodoPlatform/atomicDEX-Desktop): a secure
-    wallet and noncustodial decentralized exchange rolled into one application.
+    wallet and non-custodial decentralized exchange rolled into one application.
   * [Apparently](https://www.linkedin.com/in/skypjack/)
     [NIO](https://www.nio.io/): there was a collaboration to make some changes
     to `EnTT`, at the time used for internal projects.

docs/md/locator.md

@@ -1,14 +1,20 @@
 # Crash Course: service locator
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 # Table of Contents
 
 * [Introduction](#introduction)
 * [Service locator](#service-locator)
   * [Opaque handles](#opaque-handles)
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # Introduction
 
-Usually, service locators are tightly bound to the services they expose. It is
+Usually, service locators are tightly bound to the services they expose and it's
 hard to define a general purpose solution.<br/>
 This tiny class tries to fill the gap and gets rid of the burden of defining a
 different specific locator for each application.
@@ -27,7 +33,7 @@ entt::locator<interface>::allocate_emplace<service>(allocator, argument);
 
 The difference is that the latter expects an allocator as the first argument and
 uses it to allocate the service itself.<br/>
-Once a service is set up, it is retrieved using the `value` function:
+Once a service is set up, it's retrieved using the `value` function:
 
 ```cpp
 interface &service = entt::locator<interface>::value();
@@ -45,17 +51,17 @@ if(entt::locator<interface>::has_value()) {
 interface &service = entt::locator<interface>::value_or<fallback_impl>(argument);
 ```
 
-All arguments are used only if necessary, that is, if a service does not already
+All arguments are used only if necessary, that is, if a service doesn't already
 exist and therefore the fallback service is constructed and returned. In all
 other cases, they are discarded.<br/>
 Finally, to reset a service, use the `reset` function.
 
 ## Opaque handles
 
-Sometimes it is useful to _transfer_ a copy of a service to another locator. For
-example, when working across boundaries it is common to _share_ a service with a
+Sometimes it's useful to _transfer_ a copy of a service to another locator. For
+example, when working across boundaries it's common to _share_ a service with a
 dynamically loaded module.<br/>
-Options are not much in this case. Among these is the possibility of _exporting_
+Options aren't much in this case. Among these is the possibility of _exporting_
 services and assigning them to a different locator.
 
 This is what the `handle` and `reset` functions are meant for.<br/>
@@ -69,14 +75,14 @@ auto handle = entt::locator<interface>::handle();
 entt::locator<interface>::reset(handle);
 ```
 
-It is worth noting that it is possible to get handles for uninitialized services
+It's worth noting that it's possible to get handles for uninitialized services
 and use them with other locators. Of course, all a user will get is to have an
 uninitialized service elsewhere as well.
 
 Note that exporting a service allows users to _share_ the object currently set
-in a locator. Replacing it will not replace the element, even where a service
-has been configured with a handle to the previous item.<br/>
+in a locator. Replacing it won't replace the element even where a service has
+been configured with a handle to the previous item.<br/>
 In other words, if an audio service is replaced with a null object to silence an
-application and the original service was shared, this operation will not
-propagate to the other locators. Therefore, a module that shares the ownership
-of the original audio service is still able to emit sounds.
+application and the original service was shared, this operation won't propagate
+to the other locators. Therefore, a module that share the ownership of the
+original audio service is still able to emit sounds.

docs/md/meta.md

@@ -1,5 +1,8 @@
 # Crash Course: runtime reflection system
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 # Table of Contents
 
 * [Introduction](#introduction)
@@ -15,47 +18,48 @@
   * [From void to any](#from-void-to-any)
   * [Policies: the more, the less](#policies-the-more-the-less)
   * [Named constants and enums](#named-constants-and-enums)
-  * [User defined data](#user-defined-data)
-    * [Traits](#traits)
-    * [Custom data](#custom-data)
+  * [Properties and meta objects](#properties-and-meta-objects)
   * [Unregister types](#unregister-types)
   * [Meta context](#meta-context)
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # Introduction
 
 Reflection (or rather, its lack) is a trending topic in the C++ world and a tool
 that can unlock a lot of interesting features in the specific case of `EnTT`. I
 looked for a third-party library that met my needs on the subject, but I always
-came across some details that I did not like: macros, being intrusive, too many
+came across some details that I didn't like: macros, being intrusive, too many
 allocations, and so on.<br/>
 I finally decided to write a built-in, non-intrusive and macro-free runtime
-reflection system for `EnTT`. Maybe I did not do better than others or maybe
-yes, time will tell me, but at least I can model this tool around the library to
+reflection system for `EnTT`. Maybe I didn't do better than others or maybe yes,
+time will tell me, but at least I can model this tool around the library to
 which it belongs and not the opposite.
 
 # Names and identifiers
 
-The meta system does not force users to rely on the tools provided by the
-library when it comes to working with names and identifiers. It does this by
-offering an API that works with opaque identifiers that may or may not be
-generated by means of a hashed string.<br/>
+The meta system doesn't force users to rely on the tools provided by the library
+when it comes to working with names and identifiers. It does this by offering an
+API that works with opaque identifiers that may or may not be generated by means
+of a hashed string.<br/>
 This means that users can assign any type of identifier to the meta objects, as
-long as they are numeric. It does not matter if they are generated at runtime,
-at compile-time or with custom functions.
+long as they're numeric. It doesn't matter if they're generated at runtime, at
+compile-time or with custom functions.
 
 That being said, the examples in the following sections are all based on the
 `hashed_string` class as provided by this library. Therefore, where an
-identifier is required, it is likely that a user defined literal is used as
+identifier is required, it's likely that a user defined literal is used as
 follows:
 
 ```cpp
-entt::meta_factory<my_type>{}.type("reflected_type"_hs);
+auto factory = entt::meta<my_type>().type("reflected_type"_hs);
 ```
 
-For what it is worth, this is completely equivalent to:
+For what it's worth, this is completely equivalent to:
 
 ```cpp
-entt::meta_factory<my_type>{}.type(42u);
+auto factory = entt::meta<my_type>().type(42u);
 ```
 
 Obviously, human-readable identifiers are more convenient to use and highly
@@ -65,10 +69,10 @@ recommended.
 
 Reflection always starts from actual C++ types. Users cannot reflect _imaginary_
 types.<br/>
-The `meta_factory` class is where it all starts:
+The `meta` function is where it all starts:
 
 ```cpp
-entt::meta_factory<my_type> factory{};
+auto factory = entt::meta<my_type>();
 ```
 
 The returned value is a _factory object_ to use to continue building the meta
@@ -76,29 +80,29 @@ type.
 
 By default, a meta type is associated with the identifier returned by the
 runtime type identification system built-in in `EnTT`.<br/>
-However, it is also possible to assign custom identifiers to meta types:
+However, it's also possible to assign custom identifiers to meta types:
 
 ```cpp
-entt::meta_factory<my_type>{}.type("reflected_type"_hs);
+auto factory = entt::meta<my_type>().type("reflected_type"_hs);
 ```
 
 Identifiers are used to _retrieve_ meta types at runtime by _name_ other than by
 type.<br/>
 However, users can be interested in adding features to a reflected type so that
-the reflection system can use it correctly under the hood, while they do not
-want to also make the type _searchable_. In this case, it is sufficient not to
-invoke `type`.
+the reflection system can use it correctly under the hood, while they don't want
+to also make the type _searchable_. In this case, it's sufficient not to invoke
+`type`.
 
-A factory is such that all its member functions return the factory itself. It is
+A factory is such that all its member functions return the factory itself. It's
 generally used to create the following:
 
-* _Constructors_. A constructor is assigned to a reflected type by specifying
+* _Constructors_. A constructors is assigned to a reflected type by specifying
   its _list of arguments_. Free functions are also accepted if the return type
   is the expected one. From a client perspective, nothing changes between a free
   function or an actual constructor:
 
   ```cpp
-  entt::meta_factory<my_type>{}.ctor<int, char>().ctor<&factory>();
+  entt::meta<my_type>().ctor<int, char>().ctor<&factory>();
   ```
 
   Meta default constructors are implicitly generated, if possible.
@@ -106,7 +110,7 @@ generally used to create the following:
 * _Destructors_. Both free functions and member functions are valid destructors:
 
   ```cpp
-  entt::meta_factory<my_type>{}.dtor<&destroy>();
+  entt::meta<my_type>().dtor<&destroy>();
   ```
 
   The purpose is to offer the possibility to free up resources that require
@@ -120,7 +124,7 @@ generally used to create the following:
   type appear as if they were part of the type itself:
 
   ```cpp
-  entt::meta_factory<my_type>{}
+  entt::meta<my_type>()
       .data<&my_type::static_variable>("static"_hs)
       .data<&my_type::data_member>("member"_hs)
       .data<&global_variable>("global"_hs);
@@ -133,7 +137,13 @@ generally used to create the following:
   convenient to create read-only properties from a non-const data member:
 
   ```cpp
-  entt::meta_factory<my_type>{}.data<nullptr, &my_type::data_member>("member"_hs);
+  entt::meta<my_type>().data<nullptr, &my_type::data_member>("member"_hs);
+  ```
+
+  Multiple setters are also supported by means of a `value_list` object:
+
+  ```cpp
+  entt::meta<my_type>().data<entt::value_list<&from_int, &from_string>, &my_type::data_member>("member"_hs);
   ```
 
 * _Member functions_. Meta member functions are actual member functions of the
@@ -142,7 +152,7 @@ generally used to create the following:
   were part of the type itself:
 
   ```cpp
-  entt::meta_factory<my_type>{}
+  entt::meta<my_type>()
       .func<&my_type::static_function>("static"_hs)
       .func<&my_type::member_function>("member"_hs)
       .func<&free_function>("free"_hs);
@@ -157,7 +167,7 @@ generally used to create the following:
   derived from it:
 
   ```cpp
-  entt::meta_factory<derived_type>{}.base<base_type>();
+  entt::meta<derived_type>().base<base_type>();
   ```
 
   The reflection system tracks the relationship and allows for implicit casts at
@@ -168,7 +178,7 @@ generally used to create the following:
   that are implicitly performed by the reflection system when required:
 
   ```cpp
-  entt::meta_factory<double>{}.conv<int>();
+  entt::meta<double>().conv<int>();
   ```
 
 This is everything users need to create meta types. Refer to the inline
@@ -185,12 +195,11 @@ The API is very similar to that of the `any` type. The class `meta_any` _wraps_
 many of the feature to infer a meta node, before forwarding some or all of the
 arguments to the underlying storage.<br/>
 Among the few relevant differences, `meta_any` adds support for containers and
-pointer-like types, while `any` does not.<br/>
+pointer-like types, while `any` doesn't.<br/>
 Similar to `any`, this class is also used to create _aliases_ for unmanaged
 objects either with `forward_as_meta` or using the `std::in_place_type<T &>`
 disambiguation tag, as well as from an existing object by means of the `as_ref`
-member function. Additionally, it can take ownership of pointers passed as
-arguments along with `std::in_place`.<br/>
+member function.<br/>
 Unlike `any` instead, `meta_any` treats an empty instance and one initialized
 with `void` differently:
 
@@ -200,7 +209,7 @@ entt::meta_any other{std::in_place_type<void>};
 ```
 
 While `any` considers both as empty, `meta_any` treats objects initialized with
-`void` as if they were _valid_ ones. This allows differentiating between failed
+`void` as if they were _valid_ ones. This allows to differentiate between failed
 function calls and function calls that are successful but return nothing.
 
 Finally, the member functions `try_cast`, `cast` and `allow_cast` are used to
@@ -211,7 +220,7 @@ There is in fact no `any_cast` equivalent for `meta_any`.
 
 ## Enjoy the runtime
 
-Once the web of reflected types is constructed, it is a matter of using it at
+Once the web of reflected types is constructed, it's a matter of using it at
 runtime where required.<br/>
 There are a few options to search for a reflected type:
 
@@ -237,9 +246,9 @@ for(auto &&[id, type]: entt::resolve()) {
 ```
 
 In all cases, the returned value is an instance of `meta_type` (possibly with
-its id). These objects offer an API to know their _runtime identifiers_, to
-iterate all the meta objects associated with them and even to build instances of
-the underlying type.<br/>
+its id). This kind of objects offer an API to know their _runtime identifiers_,
+to iterate all the meta objects associated with them and even to build instances
+of the underlying type.<br/>
 Meta data members and functions are accessed by name:
 
 * Meta data members:
@@ -251,7 +260,7 @@ Meta data members and functions are accessed by name:
   The returned type is `meta_data` and may be invalid if there is no meta data
   object associated with the given identifier.<br/>
   A meta data object offers an API to query the underlying type (for example, to
-  know if it is a const or a static one), to get the meta type of the variable
+  know if it's a const or a static one), to get the meta type of the variable
   and to set or get the contained value.
 
 * Meta function members:
@@ -263,7 +272,7 @@ Meta data members and functions are accessed by name:
   The returned type is `meta_func` and may be invalid if there is no meta
   function object associated with the given identifier.<br/>
   A meta function object offers an API to query the underlying type (for
-  example, to know if it is a const or a static function), to know the number of
+  example, to know if it's a const or a static function), to know the number of
   arguments, the meta return type and the meta types of the parameters. In
   addition, a meta function object is used to invoke the underlying function and
   then get the return value in the form of a `meta_any` object.
@@ -277,9 +286,9 @@ if(auto func = entt::resolve<my_type>().func("member"_hs); func) {
 }
 ```
 
-Furthermore, all of them (and a few more, like meta basis) are returned by a
-bunch of overloads that provide the caller with iterable ranges of top-level
-elements. As an example:
+Furthermore, all them (and a few more, like meta basis) are returned by a bunch
+of overloads that provide the caller with iterable ranges of top-level elements.
+As an example:
 
 ```cpp
 for(auto &&[id, type]: entt::resolve<my_type>().base()) {
@@ -287,7 +296,7 @@ for(auto &&[id, type]: entt::resolve<my_type>().base()) {
 }
 ```
 
-Meta types are also used to `construct` actual instances of the underlying
+Meta type are also used to `construct` actual instances of the underlying
 type.<br/>
 In particular, the `construct` member function accepts a variable number of
 arguments and searches for a match. It then returns a `meta_any` object that may
@@ -297,9 +306,9 @@ or not.
 There is no object that wraps the destructor of a meta type nor a `destroy`
 member function in its API. Destructors are invoked implicitly by `meta_any`
 behind the scenes and users have not to deal with them explicitly. Furthermore,
-they have no name, cannot be searched and would not have member functions to
-expose anyway.<br/>
-Similarly, conversion functions are not directly accessible. They are used
+they've no name, cannot be searched and wouldn't have member functions to expose
+anyway.<br/>
+Similarly, conversion functions aren't directly accessible. They're used
 internally by `meta_any` and the meta objects when needed.
 
 Meta types and meta objects in general contain much more than what was said.
@@ -308,7 +317,7 @@ Refer to the inline documentation for further details.
 ## Container support
 
 The runtime reflection system also supports containers of all types.<br/>
-Moreover, _containers_ does not necessarily mean those offered by the C++
+Moreover, _containers_ doesn't necessarily mean those offered by the C++
 standard library. In fact, user defined data structures can also work with the
 meta system in many cases.
 
@@ -325,7 +334,7 @@ particular:
 * `std::map`, `std::set` and their unordered counterparts are supported as
   _associative containers_.
 
-It is important to include the header file `container.hpp` to make these
+It's important to include the header file `container.hpp` to make these
 specializations available to the compiler when needed.<br/>
 The same file also contains many examples for the users that are interested in
 making their own containers available to the meta system.
@@ -351,12 +360,12 @@ if(any.type().is_sequence_container()) {
 
 The method to use to get a proxy object for associative containers is
 `as_associative_container` instead.<br/>
-It is not necessary to perform a double check actually. Instead, it is enough to
+It's not necessary to perform a double check actually. Instead, it's enough to
 query the meta type or verify that the proxy object is valid. In fact, proxies
 are contextually convertible to bool to check for validity. For example, invalid
-proxies are returned when the wrapped object is not a container.<br/>
-In all cases, users are not expected to _reflect_ containers explicitly. It is
-sufficient to assign a container for which a specialization of the _traits_
+proxies are returned when the wrapped object isn't a container.<br/>
+In all cases, users aren't expected to _reflect_ containers explicitly. It's
+sufficient to assign a container for which a specialization of the traits
 classes exists to a `meta_any` object to be able to get its proxy object.
 
 The interface of the `meta_sequence_container` proxy object is the same for all
@@ -368,17 +377,13 @@ to case. In particular:
 * The `size` member function returns the number of elements in the container as
   an unsigned integer value.
 
-* The `resize` member function allows resizing the wrapped container and returns
-  true in case of success.<br/>
-  For example, it is not possible to resize fixed size containers.
+* The `resize` member function allows to resize the wrapped container and
+  returns true in case of success.<br/>
+  For example, it's not possible to resize fixed size containers.
 
-* The `clear` member function allows clearing the wrapped container and returns
+* The `clear` member function allows to clear the wrapped container and returns
   true in case of success.<br/>
-  For example, it is not possible to clear fixed size containers.
-
-* The `reserve` member function allows increasing the capacity of the wrapped
-  container and returns true in case of success.<br/>
-  For example, it is not possible to increase capacity of fixed size containers.
+  For example, it's not possible to clear fixed size containers.
 
 * The `begin` and `end` member functions return opaque iterators that is used to
   iterate the container directly:
@@ -392,8 +397,8 @@ to case. In particular:
   In all cases, given an underlying container of type `C`, the returned element
   contains an object of type `C::value_type` which therefore depends on the
   actual container.<br/>
-  All meta iterators are input iterators and do not offer an indirection
-  operator on purpose.
+  All meta iterators are input iterators and don't offer an indirection operator
+  on purpose.
 
 * The `insert` member function is used to add elements to the container. It
   accepts a meta iterator and the element to insert:
@@ -407,7 +412,7 @@ to case. In particular:
   This function returns a meta iterator pointing to the inserted element and a
   boolean value to indicate whether the operation was successful or not. A call
   to `insert` may silently fail in case of fixed size containers or whether the
-  arguments are not at least convertible to the required types.<br/>
+  arguments aren't at least convertible to the required types.<br/>
   Since meta iterators are contextually convertible to bool, users can rely on
   them to know if the operation failed on the actual container or upstream, for
   example due to an argument conversion problem.
@@ -464,13 +469,9 @@ differences in behavior in the case of key-only containers. In particular:
 * The `size` member function returns the number of elements in the container as
   an unsigned integer value.
 
-* The `clear` member function allows clearing the wrapped container and returns
+* The `clear` member function allows to clear the wrapped container and returns
   true in case of success.
 
-* The `reserve` member function allows increasing the capacity of the wrapped
-  container and returns true in case of success.<br/>
-  For example, it is not possible to increase capacity of standard maps.
-
 * The `begin` and `end` member functions return opaque iterators that are used
   to iterate the container directly:
 
@@ -482,10 +483,10 @@ differences in behavior in the case of key-only containers. In particular:
 
   In all cases, given an underlying container of type `C`, the returned element
   is a key-value pair where the key has type `C::key_type` and the value has
-  type `C::mapped_type`. Since key-only containers do not have a mapped type,
+  type `C::mapped_type`. Since key-only containers don't have a mapped type,
   their _value_ is nothing more than an invalid `meta_any` object.<br/>
-  All meta iterators are input iterators and do not offer an indirection
-  operator on purpose.
+  All meta iterators are input iterators and don't offer an indirection operator
+  on purpose.
 
   While the accessed key is usually constant in the associative containers and
   is therefore returned by copy, the value (if any) is wrapped by an instance of
@@ -493,7 +494,7 @@ differences in behavior in the case of key-only containers. In particular:
   modifies the element inside the container.
 
 * The `insert` member function is used to add elements to a container. It gets
-  two arguments, the key and the value to insert:
+  two arguments, respectively the key and the value to insert:
 
   ```cpp
   auto last = view.end();
@@ -502,7 +503,7 @@ differences in behavior in the case of key-only containers. In particular:
   ```
 
   This function returns a boolean value to indicate whether the operation was
-  successful or not. A call to `insert` may fail when the arguments are not at
+  successful or not. A call to `insert` may fail when the arguments aren't at
   least convertible to the required types.
 
 * The `erase` member function is used to remove elements from a container. It
@@ -513,8 +514,8 @@ differences in behavior in the case of key-only containers. In particular:
   ```
 
   This function returns a boolean value to indicate whether the operation was
-  successful or not. A call to `erase` may fail when the argument is not at
-  least convertible to the required type.
+  successful or not. A call to `erase` may fail when the argument isn't at least
+  convertible to the required type.
 
 * The `operator[]` is used to access elements in a container. It gets a single
   argument, the key of the element to return:
@@ -531,7 +532,7 @@ Container support is minimal but likely sufficient to satisfy all needs.
 
 ## Pointer-like types
 
-As with containers, it is also possible to _tell_ to the meta system which types
+As with containers, it's also possible to _tell_ to the meta system which types
 are _pointers_. This makes it possible to dereference instances of `meta_any`,
 thus obtaining light _references_ to pointed objects that are also correctly
 associated with their meta types.<br/>
@@ -541,21 +542,13 @@ some common classes. In particular:
 
 * All types of raw pointers.
 * `std::unique_ptr` and `std::shared_ptr`.
-* All classes that _export_ a type member called `is_meta_pointer_like`:
-  ```cpp
-  struct smart_pointer {
-      using is_meta_pointer_like = void;
-      // ...
-  };
-  ```
-  The actual type is irrelevant and will not be used in any way.
 
-It is important to include the header file `pointer.hpp` to make these
+It's important to include the header file `pointer.hpp` to make these
 specializations available to the compiler when needed.<br/>
 The same file also contains many examples for the users that are interested in
 making their own pointer-like types available to the meta system.
 
-When a type is recognized as a pointer-like one by the meta system, it is
+When a type is recognized as a pointer-like one by the meta system, it's
 possible to dereference the instances of `meta_any` that contain these objects.
 The following is a deliberately verbose example to show how to use this feature:
 
@@ -572,18 +565,18 @@ if(any.type().is_pointer_like()) {
 }
 ```
 
-It is not necessary to perform a double check. Instead, it is enough to query
-the meta type or verify that the returned object is valid. For example, invalid
-instances are returned when the wrapped object is not a pointer-like type.<br/>
+It's not necessary to perform a double check. Instead, it's enough to query the
+meta type or verify that the returned object is valid. For example, invalid
+instances are returned when the wrapped object isn't a pointer-like type.<br/>
 Dereferencing a pointer-like object returns an instance of `meta_any` which
 _refers_ to the pointed object. Modifying it means modifying the pointed object
 directly (unless the returned element is const).
 
 In general, _dereferencing_ a pointer-like type boils down to a `*ptr`. However,
-`EnTT` also supports classes that do not offer an `operator*`. In particular:
+`EnTT` also supports classes that don't offer an `operator*`. In particular:
 
-* It is possible to exploit a solution based on ADL lookup by implementing a
-  function (also a template one) named `dereference_meta_pointer_like`:
+* It's possible to exploit a solution based on ADL lookup by offering a function
+  (also a template one) named `dereference_meta_pointer_like`:
 
   ```cpp
   template<typename Type>
@@ -592,7 +585,7 @@ In general, _dereferencing_ a pointer-like type boils down to a `*ptr`. However,
   }
   ```
 
-* When not in control of the type's namespace, it is possible to inject into the
+* When not in control of the type's namespace, it's possible to inject into the
   `entt` namespace a specialization of the `adl_meta_pointer_like` class
   template to bypass the adl lookup as a whole:
 
@@ -611,12 +604,12 @@ of the pointed type, no user intervention is required.
 ## Template information
 
 Meta types also provide a minimal set of information about the _nature_ of the
-original type in case it is a class template.<br/>
-By default, this works out of the box and requires no user action. However, it
-is important to include the header file `template.hpp` to make this information
+original type in case it's a class template.<br/>
+By default, this works out of the box and requires no user action. However, it's
+important to include the header file `template.hpp` to make this information
 available to the compiler when needed.
 
-Meta template information is easily found:
+Meta template information are easily found:
 
 ```cpp
 // this method returns true if the type is recognized as a class template specialization
@@ -632,7 +625,7 @@ if(auto type = entt::resolve<std::shared_ptr<my_type>>(); type.is_template_speci
 }
 ```
 
-Typically, when template information for a type is required, what the library
+Typically, when template information for a type are required, what the library
 provides is sufficient. However, there are some cases where a user may want more
 details or a different set of information.<br/>
 Consider the case of a class template that is meant to wrap function types:
@@ -659,8 +652,8 @@ struct entt::meta_template_traits<function_type<Ret(Args...)>> {
 };
 ```
 
-The reflection system does not verify the accuracy of the information nor infer
-a correspondence between real types and meta types.<br/>
+The reflection system doesn't verify the accuracy of the information nor infer a
+correspondence between real types and meta types.<br/>
 Therefore, the specialization is used as is and the information it contains is
 associated with the appropriate type when required.
 
@@ -672,7 +665,7 @@ If this were to be translated into explicit registrations with the reflection
 system, it would result in a long series of instructions such as the following:
 
 ```cpp
-entt::meta_factory<int>{}
+entt::meta<int>()
     .conv<bool>()
     .conv<char>()
     // ...
@@ -686,7 +679,7 @@ underlying types and offers what it takes to do the same for scoped enums. It
 would result in the following if it were to be done explicitly:
 
 ```cpp
-entt::meta_factory<my_enum>{}
+entt::meta<my_enum>()
     .conv<std::underlying_type_t<my_enum>>();
 ```
 
@@ -711,8 +704,8 @@ int value = any.cast<int>();
 
 This makes working with arithmetic types and scoped or unscoped enums as easy as
 it is in C++.<br/>
-It is still possible to set up conversion functions manually, and these are
-always preferred over the automatic ones.
+It's still possible to set up conversion functions manually and these are always
+preferred over the automatic ones.
 
 ## Implicitly generated default constructor
 
@@ -725,13 +718,13 @@ them.
 For default constructible types only, default constructors are automatically
 defined and associated with their meta types, whether they are explicitly or
 implicitly generated.<br/>
-Therefore, this is all needed to construct an integer from its meta type:
+Therefore, this is all is needed to construct an integer from its meta type:
 
 ```cpp
 entt::resolve<int>().construct();
 ```
 
-Where the meta type is, for example, the one returned from a meta container,
+Where the meta type is for example the one returned from a meta container,
 useful for building keys without knowing or having to register the actual types.
 
 In all cases, when users register default constructors, they are preferred both
@@ -749,7 +742,7 @@ designed to convert an opaque pointer into a `meta_any`:
 entt::meta_any any = entt::resolve(id).from_void(element);
 ```
 
-Unfortunately, it is not possible to do a check on the actual type. Therefore,
+Unfortunately, it's not possible to do a check on the actual type. Therefore,
 this call can be considered as a _static cast_ with all its _problems_.<br/>
 On the other hand, the ability to construct a `meta_any` from an opaque pointer
 opens the door to some pretty interesting uses that are worth exploring.
@@ -762,14 +755,14 @@ Their purpose is to require slightly different behavior than the default in some
 specific cases. For example, when reading a given data member, its value is
 returned wrapped in a `meta_any` object which, by default, makes a copy of it.
 For large objects or if the caller wants to access the original instance, this
-behavior is not desirable. Policies are there to offer a solution to this and
+behavior isn't desirable. Policies are there to offer a solution to this and
 other problems.
 
 There are a few alternatives available at the moment:
 
 * The _as-is_ policy, associated with the type `entt::as_is_t`.<br/>
   This is the default policy. In general, it should never be used explicitly,
-  since it is implicitly selected if no other policy is specified.<br/>
+  since it's implicitly selected if no other policy is specified.<br/>
   In this case, the return values of the functions as well as the properties
   exposed as data members are always returned by copy in a dedicated wrapper and
   therefore associated with their original meta types.
@@ -779,13 +772,13 @@ There are a few alternatives available at the moment:
   thus making it appear as if its type were `void`:
 
   ```cpp
-  entt::meta_factory<my_type>{}.func<&my_type::member_function, entt::as_void_t>("member"_hs);
+  entt::meta<my_type>().func<&my_type::member_function, entt::as_void_t>("member"_hs);
   ```
 
   If the use with functions is obvious, perhaps less so is use with constructors
   and data members. In the first case, the returned wrapper is always empty even
   though the constructor is still invoked. In the second case, the property
-  is not accessible for reading instead.
+  isn't accessible for reading instead.
 
 * The _as-ref_ and _as-cref_ policies, associated with the types
   `entt::as_ref_t` and `entt::as_cref_t`.<br/>
@@ -795,7 +788,7 @@ There are a few alternatives available at the moment:
   the wrapper itself:
 
   ```cpp
-  entt::meta_factory<my_type>{}.data<&my_type::data_member, entt::as_ref_t>("member"_hs);
+  entt::meta<my_type>().data<&my_type::data_member, entt::as_ref_t>("member"_hs);
   ```
 
   These policies work with constructors (for example, when objects are taken
@@ -805,7 +798,7 @@ There are a few alternatives available at the moment:
   `as_ref_t` _adapts_ to the constness of the passed object and to that of the
   return type if any.
 
-Some uses are rather trivial, but it is useful to note that there are some less
+Some uses are rather trivial, but it's useful to note that there are some less
 obvious corner cases that can in turn be solved with the use of policies.
 
 ## Named constants and enums
@@ -822,15 +815,15 @@ between enums and classes in C++ directly in the space of the reflected types.
 Exposing constant values or elements from an enum is quite simple:
 
 ```cpp
-entt::meta_factory<my_enum>{}
+entt::meta<my_enum>()
     .data<my_enum::a_value>("a_value"_hs)
     .data<my_enum::another_value>("another_value"_hs);
 
-entt::meta_factory<int>{}.data<2048>("max_int"_hs);
+entt::meta<int>().data<2048>("max_int"_hs);
 ```
 
-Accessing them is trivial as well. It is a matter of doing the following, as
-with any other data member of a meta type:
+Accessing them is trivial as well. It's a matter of doing the following, as with
+any other data member of a meta type:
 
 ```cpp
 auto value = entt::resolve<my_enum>().data("a_value"_hs).get({}).cast<my_enum>();
@@ -840,97 +833,54 @@ auto max = entt::resolve<int>().data("max_int"_hs).get({}).cast<int>();
 All this happens behind the scenes without any allocation because of the small
 object optimization performed by the `meta_any` class.
 
-## User defined data
+## Properties and meta objects
 
 Sometimes (for example, when it comes to creating an editor) it might be useful
-to attach _traits_ or arbitrary _custom data_ to the meta objects created.
-
-The main difference between them is that:
-
-* Traits are simple user-defined flags with much higher access performance. The
-  library reserves up to 16 bits for traits, that is 16 flags for a bitmask or
-  2^16 values otherwise.
-
-* Custom data are stored in a generic quick access area reserved for the user
-  and which the library will never use under any circumstances.
-
-In all cases, this support is currently available only for meta types, meta data
-and meta functions.
-
-### Traits
-
-User-defined traits are set via a meta factory:
+to attach properties to the meta objects created. Fortunately, this is possible
+for most of them:
 
 ```cpp
-entt::meta_factory<my_type>{}.traits(my_traits::required | my_traits::hidden);
+entt::meta<my_type>().type("reflected_type"_hs).prop("tooltip"_hs, "message");
 ```
 
-In the example above, `EnTT` bitmask enum support is used, but any integral
-value is fine, as long as it does not exceed 16 bits.<br/>
-It is not possible to assign traits at different times. Therefore, multiple
-calls to the `traits` function overwrite previous values. However, traits can be
-read from meta objects and used to update existing data with a factory,
-effectively extending them as needed.<br/>
-Likewise, users can also set traits on meta objects later if needed, as long as
-the factory is reset to the meta object of interest:
+Properties are always in the key/value form. The key is a numeric identifier,
+mostly similar to the identifier used to register meta objects. There are no
+restrictions on the type of the value instead, as long as it's movable.<br/>
+Key only properties are also supported out of the box:
 
 ```cpp
-entt::meta_factory<my_type>{}
-    .data<&my_type::data_member, entt::as_ref_t>("member"_hs)
-    .traits(my_traits::internal);
+entt::meta<my_type>().type("reflected_type"_hs).prop(my_enum::key_only);
 ```
 
-Once created, all meta objects offer a member function named `traits` to get the
-currently set value:
+To attach multiple properties to a meta object, just invoke `prop` more than
+once.<br/>
+It's also possible to call `prop` at different times, as long as the factory is
+reset to the meta object of interest.
+
+The meta objects for which properties are supported are currently meta types,
+meta data and meta functions.<br/>
+These types also offer a couple of member functions named `prop` to iterate all
+properties at once or to search a specific property by key:
 
 ```cpp
-auto value = entt::resolve<my_type>().traits<my_traits>();
+// iterate all properties of a meta type
+for(auto &&[id, prop]: entt::resolve<my_type>().prop()) {
+    // ...
+}
+
+// search for a given property by name
+auto prop = entt::resolve<my_type>().prop("tooltip"_hs);
 ```
 
-Note that the type is erased upon registration and must therefore be repeated
-when traits are _extracted_, so as to allow the library to _reconstruct_ them
-correctly.
-
-### Custom data
-
-Custom arbitrary data are set via a meta factory:
-
-```cpp
-entt::meta_factory<my_type>{}.custom<type_data>("name");
-```
-
-The way to do this is by specifying the data type to the `custom` function and
-passing the necessary arguments to construct it correctly.<br/>
-It is not possible to assign custom data at different times. Therefore, multiple
-calls to the `custom` function overwrite previous values. However, this value
-can be read from meta objects and used to update existing data with a factory,
-effectively updating them as needed.<br/>
-Likewise, users can also set custom data on meta objects later if needed, as
-long as the factory is reset to the meta object of interest:
-
-```cpp
-entt::meta_factory<my_type>{}
-    .func<&my_type::member_function>("member"_hs)
-    .custom<function_data>("tooltip");
-```
-
-Once created, all meta objects offer a member function named `custom` to get the
-currently set value as a reference or as a pointer to an element:
-
-```cpp
-const type_data &value = entt::resolve<my_type>().custom();
-```
-
-Note that the returned object performs an extra check in debug before converting
-to the requested type, so as to avoid subtle bugs.<br/>
-Only in the case of conversion to a pointer is this check safe and such that a
-null pointer is returned to inform the user of the failed attempt.
+Meta properties are objects having a fairly poor interface, all in all. They
+only provide the `value` member function to retrieve the contained value in the
+form of a `meta_any` object.
 
 ## Unregister types
 
 A type registered with the reflection system can also be _unregistered_. This
 means unregistering all its data members, member functions, conversion functions
-and so on. However, base classes are not unregistered as well, since they do not
+and so on. However, base classes aren't unregistered as well, since they don't
 necessarily depend on it.<br/>
 Roughly speaking, unregistering a type means disconnecting all associated meta
 objects from it and making its identifier no longer available:
@@ -939,14 +889,14 @@ objects from it and making its identifier no longer available:
 entt::meta_reset<my_type>();
 ```
 
-It is also possible to reset types by their unique identifiers:
+It's also possible to reset types by their unique identifiers:
 
 ```cpp
 entt::meta_reset("my_type"_hs);
 ```
 
 Finally, there exists a non-template overload of the `meta_reset` function that
-does not accept arguments and resets all meta types at once:
+doesn't accept arguments and resets all meta types at once:
 
 ```cpp
 entt::meta_reset();
@@ -963,7 +913,7 @@ _context_. This is obtained via a service locator as:
 auto &&context = entt::locator<entt::meta_context>::value_or();
 ```
 
-By itself, a context is an opaque object that the user can do little with.
+By itself, a context is an opaque object that the user cannot do much with.
 However, users can replace an existing context with another at any time:
 
 ```cpp
@@ -973,20 +923,20 @@ std::swap(context, other);
 ```
 
 This is useful for testing purposes or to define multiple context objects with
-different meta types to use as appropriate.
+different meta type to use as appropriate.
 
-If _replacing_ the default context is not enough, `EnTT` also offers the ability
+If _replacing_ the default context isn't enough, `EnTT` also offers the ability
 to use multiple and externally managed contexts with the runtime reflection
 system.<br/>
 For example, to create new meta types within a context other than the default
-one, simply pass it as an argument to the `meta_factory` constructor:
+one, simply pass it as an argument to the `meta` call:
 
 ```cpp
 entt::meta_ctx context{};
-entt::meta_factory<my_type>{context}.type("reflected_type"_hs);
+auto factory = entt::meta<my_type>(context).type("reflected_type"_hs);
 ```
 
-By doing so, the new meta type is not available in the default context but is
+By doing so, the new meta type isn't available in the default context but is
 usable by passing around the new context when needed, such as when creating a
 new `meta_any` object:
 
@@ -995,17 +945,17 @@ entt::meta_any any{context, std::in_place_type<my_type>};
 ```
 
 Similarly, to search for meta types in a context other than the default one,
-it is necessary to pass it to the `resolve` function:
+it's necessary to pass it to the `resolve` function:
 
 ```cpp
 entt::meta_type type = entt::resolve(context, "reflected_type"_hs)
 ```
 
-More generally, when using externally managed contexts, it is always required to
+More generally, when using externally managed contexts, it's always required to
 provide the system with the context to use, at least at the _entry point_.<br/>
-For example, once the `meta_type` instant is obtained, it is no longer necessary
+For example, once the `meta_type` instant is obtained, it's no longer necessary
 to pass the context around as the meta type takes the information with it and
 eventually propagates it to all its parts.<br/>
-On the other hand, it is necessary to instruct the library on where meta types
+On the other hand, it's necessary to instruct the library on where meta types
 are to be fetched when `meta_any`s and `meta_handle`s are constructed, a factory
 created or a meta type resolved.

docs/md/poly.md

@@ -1,5 +1,8 @@
 # Crash Course: poly
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 # Table of Contents
 
 * [Introduction](#introduction)
@@ -11,6 +14,9 @@
 * [Inheritance](#inheritance)
 * [Static polymorphism in the wild](#static-polymorphism-in-the-wild)
 * [Storage size and alignment requirement](#storage-size-and-alignment-requirement)
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # Introduction
 
@@ -45,12 +51,12 @@ The ones that I like more are:
   object wrapper.
 
 The former is admittedly an experimental library, with many interesting ideas.
-I have some doubts about the usefulness of some features in real world projects,
+I've some doubts about the usefulness of some feature in real world projects,
 but perhaps my lack of experience comes into play here. In my opinion, its only
-flaw is the API that I find slightly more cumbersome than other solutions.<br/>
-The latter was undoubtedly a source of inspiration for this module. Although I
+flaw is the API which I find slightly more cumbersome than other solutions.<br/>
+The latter was undoubtedly a source of inspiration for this module, although I
 opted for different choices in the implementation of both the final API and some
-features.
+feature.
 
 Either way, the authors are gurus of the C++ community, people I only have to
 learn from.
@@ -63,7 +69,7 @@ types will have to adhere to.<br/>
 For this purpose, the library offers a single class that supports both deduced
 and fully defined interfaces. Although having interfaces deduced automatically
 is convenient and allows users to write less code in most cases, it has some
-limitations. It is therefore useful to be able to get around the deduction by
+limitations and it's therefore useful to be able to get around the deduction by
 providing a custom definition for the static virtual table.
 
 Once the interface is defined, a generic implementation is needed to fulfill the
@@ -86,7 +92,7 @@ struct Drawable: entt::type_list<> {
 };
 ```
 
-It is recognizable by the fact that it inherits from an empty type list.<br/>
+It's recognizable by the fact that it inherits from an empty type list.<br/>
 Functions can also be const, accept any number of parameters and return a type
 other than `void`:
 
@@ -104,7 +110,7 @@ struct Drawable: entt::type_list<> {
 In this case, all parameters are passed to `invoke` after the reference to
 `this` and the return value is whatever the internal call returns.<br/>
 As for `invoke`, this is a name that is injected into the _concept_ through
-`Base`, from which one must necessarily inherit. Since it is also a dependent
+`Base`, from which one must necessarily inherit. Since it's also a dependent
 name, the `this-> template` form is unfortunately necessary due to the rules of
 the language. However, there also exists an alternative that goes through an
 external call:
@@ -171,9 +177,9 @@ If the concept exposes a member function called `draw` with function type
 * Or through a lambda that makes use of existing member functions from the
   interface itself.
 
-In other words, it is not possible to make use of functions not belonging to the
-interface, even if they are part of the types that fulfill the concept.<br/>
-Similarly, it is not possible to deduce a function in the static virtual table
+In other words, it's not possible to make use of functions not belonging to the
+interface, even if they're part of the types that fulfill the concept.<br/>
+Similarly, it's not possible to deduce a function in the static virtual table
 with a function type different from that of the associated member function in
 the interface itself.
 
@@ -182,7 +188,7 @@ allows maximum flexibility when providing the implementation for a concept.
 
 ## Fulfill a concept
 
-The `impl` alias template of a concept is used to define how it is fulfilled:
+The `impl` alias template of a concept is used to define how it's fulfilled:
 
 ```cpp
 struct Drawable: entt::type_list<> {
@@ -193,7 +199,7 @@ struct Drawable: entt::type_list<> {
 };
 ```
 
-In this case, it is stated that the `draw` method of a generic type is enough to
+In this case, it's stated that the `draw` method of a generic type is enough to
 satisfy the requirements of the `Drawable` concept.<br/>
 Both member functions and free functions are supported to fulfill concepts:
 
@@ -211,9 +217,9 @@ struct Drawable: entt::type_list<void()> {
 
 Likewise, as long as the parameter types and return type support conversions to
 and from those of the function type referenced in the static virtual table, the
-actual implementation may differ in its function type since it is erased
+actual implementation may differ in its function type since it's erased
 internally.<br/>
-Moreover, the `self` parameter is not strictly required by the system and can be
+Moreover, the `self` parameter isn't strictly required by the system and can be
 left out for free functions if not required.
 
 Refer to the inline documentation for more details.
@@ -221,7 +227,7 @@ Refer to the inline documentation for more details.
 # Inheritance
 
 _Concept inheritance_ is straightforward due to how poly looks like in `EnTT`.
-Therefore, it is quite easy to build hierarchies of concepts if necessary.<br/>
+Therefore, it's quite easy to build hierarchies of concepts if necessary.<br/>
 The only constraint is that all concepts in a hierarchy must belong to the same
 _family_, that is, they must be either all deduced or all defined.
 
@@ -230,8 +236,8 @@ For a deduced concept, inheritance is achieved in a few steps:
 ```cpp
 struct DrawableAndErasable: entt::type_list<> {
     template<typename Base>
-    struct type: typename Drawable::type<Base> {
-        static constexpr auto base = Drawable::impl<Drawable::type<entt::poly_inspector>>::size;
+    struct type: typename Drawable::template type<Base> {
+        static constexpr auto base = std::tuple_size_v<typename entt::poly_vtable<Drawable>::type>;
         void erase() { entt::poly_call<base + 0>(*this); }
     };
 
@@ -253,21 +259,22 @@ in appending the new functions to the previous list.
 
 As for a defined concept instead, the list of types is _extended_ in a similar
 way to what is shown for the implementation of the above concept.<br/>
-To do this, it is useful to declare a function that allows to convert a
-_concept_ into its underlying `type_list` object:
+To do this, it's useful to declare a function that allows to convert a _concept_
+into its underlying `type_list` object:
 
 ```cpp
 template<typename... Type>
 entt::type_list<Type...> as_type_list(const entt::type_list<Type...> &);
 ```
 
-The definition is not strictly required, since the function is only used through
+The definition isn't strictly required, since the function is only used through
 a `decltype` as it follows:
 
 ```cpp
 struct DrawableAndErasable: entt::type_list_cat_t<
     decltype(as_type_list(std::declval<Drawable>())),
-    entt::type_list<void()>> {
+    entt::type_list<void()>
+> {
     // ...
 };
 ```
@@ -278,7 +285,7 @@ Everything else is the same as already shown instead.
 
 # Static polymorphism in the wild
 
-Once the _concept_ and implementation are defined, it is possible to use the
+Once the _concept_ and implementation are defined, it's possible to use the
 `poly` class template to _wrap_ instances that meet the requirements:
 
 ```cpp
@@ -312,16 +319,15 @@ circle shape;
 drawable instance{std::in_place_type<circle &>, shape};
 ```
 
-Similarly, it is possible to create non-owning copies of `poly` from an existing
+Similarly, it's possible to create non-owning copies of `poly` from an existing
 object:
 
 ```cpp
 drawable other = instance.as_ref();
 ```
 
-In both cases, although the interface of the `poly` object does not change, it
-does not construct any element or take care of destroying the referenced
-objects.
+In both cases, although the interface of the `poly` object doesn't change, it
+doesn't construct any element or take care of destroying the referenced objects.
 
 Note also how the underlying concept is accessed via a call to `operator->` and
 not directly as `instance.draw()`.<br/>
@@ -343,9 +349,9 @@ entt::basic_poly<Drawable, sizeof(double[4]), alignof(double[4])>
 
 The default size is `sizeof(double[2])`, which seems like a good compromise
 between a buffer that is too large and one unable to hold anything larger than
-an integer. The alignment requirement is optional, and by default such that it
-is the most stringent (the largest) for any object whose size is at most equal
-to the one provided.<br/>
-It is worth noting that providing a size of 0 (which is an accepted value in all
+an integer. The alignment requirement is optional and by default such that it's
+the most stringent (the largest) for any object whose size is at most equal to
+the one provided.<br/>
+It's worth noting that providing a size of 0 (which is an accepted value in all
 respects) will force the system to dynamically allocate the contained objects in
 all cases.

docs/md/process.md

@@ -1,11 +1,17 @@
 # Crash Course: cooperative scheduler
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 # Table of Contents
 
 * [Introduction](#introduction)
 * [The process](#the-process)
   * [Adaptor](#adaptor)
 * [The scheduler](#the-scheduler)
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # Introduction
 
@@ -22,22 +28,22 @@ CRTP idiom. Moreover, derived classes specify what the intended type for elapsed
 times is.
 
 A process should expose publicly the following member functions whether needed
-(note that it is not required to define a function unless the derived class
-wants to _override_ the default behavior):
+(note that it isn't required to define a function unless the derived class wants
+to _override_ the default behavior):
 
 * `void update(Delta, void *);`
 
   This is invoked once per tick until a process is explicitly aborted or ends
-  either with or without errors. Technically speaking, this member function is 
-  not strictly required. However, each process should at least define it to work
-  _properly_. The `void *` parameter is an opaque pointer to user data (if any)
-  forwarded directly to the process during an update.
+  either with or without errors. Even though it's not mandatory to declare this
+  member function, as a rule of thumb each process should at least define it to
+  work _properly_. The `void *` parameter is an opaque pointer to user data (if
+  any) forwarded directly to the process during an update.
 
 * `void init();`
 
   This is invoked when the process joins the running queue of a scheduler. It
-  happens usually when the process is attached to the scheduler if it is a top
-  level one, or when it replaces its parent if it is a _continuation_.
+  happens usually as soon as the process is attached to the scheduler if it's a
+  top level one, otherwise when it replaces its parent if it's a _continuation_.
 
 * `void succeeded();`
 
@@ -87,8 +93,8 @@ private:
 
 ## Adaptor
 
-Lambdas and functors cannot be used directly with a scheduler because they are
-not properly defined processes with managed life cycles.<br/>
+Lambdas and functors can't be used directly with a scheduler because they aren't
+properly defined processes with managed life cycles.<br/>
 This class helps in filling the gap and turning lambdas and functors into
 full-featured processes usable by a scheduler.
 
@@ -109,22 +115,22 @@ Parameters have the following meaning:
 
 Both `succeed` and `fail` accept no parameters at all.
 
-Note that usually users should not worry about creating adaptors at all. A
-scheduler creates them internally, each and every time a lambda or a functor is
+Note that usually users shouldn't worry about creating adaptors at all. A
+scheduler creates them internally each and every time a lambda or a functor is
 used as a process.
 
 # The scheduler
 
-A cooperative scheduler runs different processes and helps manage their life
+A cooperative scheduler runs different processes and helps managing their life
 cycles.
 
-Each process is invoked once per tick. If it terminates, it is removed
-automatically from the scheduler, and it is never invoked again. Otherwise,
-it is a good candidate to run one more time the next tick.<br/>
+Each process is invoked once per tick. If it terminates, it's removed
+automatically from the scheduler and it's never invoked again. Otherwise, it's
+a good candidate to run one more time the next tick.<br/>
 A process can also have a _child_. In this case, the parent process is replaced
 with its child when it terminates and only if it returns with success. In case
-of errors, both the parent process and its child are discarded. This way, it is
-easy to create a chain of processes to run sequentially.
+of errors, both the parent process and its child are discarded. This way, it's
+easy to create chain of processes to run sequentially.
 
 Using a scheduler is straightforward. To create it, users must provide only the
 type for the elapsed times and no arguments at all:
@@ -154,9 +160,9 @@ entt::scheduler::size_type size = scheduler.size();
 scheduler.clear();
 ```
 
-To attach a process to a scheduler, there are mainly two ways:
+To attach a process to a scheduler there are mainly two ways:
 
-* If the process inherits from the `process` class template, it is enough to
+* If the process inherits from the `process` class template, it's enough to
   indicate its type and submit all the parameters required to construct it to
   the `attach` member function:
 
@@ -164,15 +170,15 @@ To attach a process to a scheduler, there are mainly two ways:
   scheduler.attach<my_process>(1000u);
   ```
 
-* Otherwise, in case of a lambda or a functor, it is enough to provide an
+* Otherwise, in case of a lambda or a functor, it's enough to provide an
   instance of the class to the `attach` member function:
 
   ```cpp
   scheduler.attach([](auto...){ /* ... */ });
   ```
 
-In both cases, the scheduler is returned and its `then` member function can be
-used to create chains of processes to run sequentially.<br/>
+In both cases, the return value is an opaque object that offers a `then` member
+function used to create chains of processes to run sequentially.<br/>
 As a minimal example of use:
 
 ```cpp

docs/md/reference.md

@@ -1,9 +1,15 @@
 # Similar projects
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 # Table of Contents
 
 * [Introduction](#introduction)
 * [Similar projects](#similar-projects)
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # Introduction
 
@@ -14,14 +20,13 @@ Others developed different architectures from scratch and therefore offer
 alternative solutions with their pros and cons.
 
 If you know of other similar projects out there, feel free to open an issue or a
-PR, and I will be glad to add them to this page.<br/>
+PR and I'll be glad to add them to this page.<br/>
 I hope the following lists can grow much more in the future.
 
 # Similar projects
 
-Below an incomplete list of similar projects that I have come across so
-far.<br/>
-If some terms or designs are not clear, I recommend referring to the
+Below an incomplete list of similar projects that I've come across so far.<br/>
+If some terms or designs aren't clear, I recommend referring to the
 [_ECS Back and Forth_](https://skypjack.github.io/tags/#ecs) series for all the
 details.
 
@@ -35,12 +40,12 @@ details.
   * [lent](https://github.com/nem0/lent): the Donald Trump of the ECS libraries.
 
 * C++:
-  * [decs](https://github.com/vblanco20-1/decs): a chunk-based archetype ECS.
+  * [decs](https://github.com/vblanco20-1/decs): a chunk based archetype ECS.
   * [ecst](https://github.com/SuperV1234/ecst): a multithreaded compile-time
     ECS that uses sparse sets to keep track of entities in systems.
   * [EntityX](https://github.com/alecthomas/entityx): a bitset based ECS that
     uses a single large matrix of components indexed with entities.
-  * [Gaia-ECS](https://github.com/richardbiely/gaia-ecs): a chunk-based
+  * [Gaia-ECS](https://github.com/richardbiely/gaia-ecs): a chunk based
     archetype ECS.
   * [Polypropylene](https://github.com/pmbittner/Polypropylene): a hybrid
     solution between an ECS and dynamic mixins.
@@ -50,16 +55,10 @@ details.
     inspired archetype ECS with optional multithreading. 
   * [Entitas](https://github.com/sschmid/Entitas-CSharp): the ECS framework for
     C# and Unity, where _reactive systems_ were invented.
-  * [Fennecs](https://github.com/outfox/fennecs): the little archetype ECS that
-    loves you back.
-  * [Friflo ECS](https://github.com/friflo/Friflo.Engine.ECS): an archetype ECS
-    with focus on performance and minimal GC allocations.
   * [LeoECS](https://github.com/Leopotam/ecs): simple lightweight C# Entity
     Component System framework.
-  * [Massive ECS](https://github.com/nilpunch/massive): sparse set based ECS
-    featuring rollbacks.
   * [Svelto.ECS](https://github.com/sebas77/Svelto.ECS): a very interesting
-    platform-agnostic and table-based ECS framework.
+    platform agnostic and table based ECS framework.
 
 * Go:
   * [gecs](https://github.com/tutumagi/gecs): a sparse sets based ECS inspired 
@@ -68,7 +67,7 @@ details.
 * Javascript:
   * [\@javelin/ecs](https://github.com/3mcd/javelin/tree/master/packages/ecs):
     an archetype ECS in TypeScript.
-  * [ecsy](https://github.com/MozillaReality/ecsy): I have not had the time to
+  * [ecsy](https://github.com/MozillaReality/ecsy): I haven't had the time to
     investigate the underlying design of `ecsy` but it looks cool anyway.
 
 * Perl:
@@ -80,6 +79,7 @@ details.
     entity registry for ECS designs inspired by `EnTT`.
 
 * Rust:
+  * [Legion](https://github.com/TomGillen/legion): a chunk based archetype ECS.
   * [Shipyard](https://github.com/leudz/shipyard): it borrows some ideas from
     `EnTT` and offers a sparse sets based ECS with grouping functionalities.
   * [Sparsey](https://github.com/LechintanTudor/sparsey): sparse set based ECS

docs/md/resource.md

@@ -1,12 +1,18 @@
 # Crash Course: resource management
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 # Table of Contents
 
 * [Introduction](#introduction)
 * [The resource, the loader and the cache](#the-resource-the-loader-and-the-cache)
   * [Resource handle](#resource-handle)
-  * [Loaders](#loaders)
-  * [The cache class](#the-cache-class)
+  * [Loaders](#loader)
+  * [The cache class](#the-cache)
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # Introduction
 
@@ -17,7 +23,7 @@ requirements of the piece of software in which they are used.<br/>
 Examples are loading everything on start, loading on request, predictive
 loading, and so on.
 
-`EnTT` does not pretend to offer a _one-fits-all_ solution for the different
+`EnTT` doesn't pretend to offer a _one-fits-all_ solution for the different
 cases.<br/>
 Instead, the library comes with a minimal, general purpose resource cache that
 might be useful in many cases.
@@ -31,8 +37,7 @@ The _resource_ is an image, an audio, a video or any other type:
 struct my_resource { const int value; };
 ```
 
-The _loader_ is a callable type, the aim of which is to load a specific
-resource:
+The _loader_ is a callable type the aim of which is to load a specific resource:
 
 ```cpp
 struct my_loader final {
@@ -69,9 +74,9 @@ discarded when a player leaves it.
 
 ## Resource handle
 
-Resources are not returned directly to the caller. Instead, they are wrapped in
-a _resource handle_, an instance of the `entt::resource` class template.<br/>
-For those who know the _flyweight design pattern_ already, that is exactly what
+Resources aren't returned directly to the caller. Instead, they are wrapped in a
+_resource handle_, an instance of the `entt::resource` class template.<br/>
+For those who know the _flyweight design pattern_ already, that's exactly what
 it is. To all others, this is the time to brush up on some notions instead.
 
 A shared pointer could have been used as a resource handle. In fact, the default
@@ -85,22 +90,22 @@ more or all resource types could help over time.
 ## Loaders
 
 A loader is responsible for _loading_ resources (quite obviously).<br/>
-By default, it is just a callable object that forwards its arguments to the
+By default, it's just a callable object that forwards its arguments to the
 resource itself. That is, a _passthrough type_. All the work is demanded to the
 constructor(s) of the resource itself.<br/>
 Loaders also are fully customizable as expected.
 
 A custom loader is a class with at least one function call operator and a member
 type named `result_type`.<br/>
-The loader is not required to return a resource handle. As long as `return_type`
-is suitable for constructing a handle, that is fine.
+The loader isn't required to return a resource handle. As long as `return_type`
+is suitable for constructing a handle, that's fine.
 
 When using the default handle, it expects a resource type which is convertible
 to or suitable for constructing an `std::shared_ptr<Type>` (where `Type` is the
 actual resource type).<br/>
 In other terms, the loader should return shared pointers to the given resource
-type. However, this is not mandatory. Users can easily get around this
-constraint by specializing both the handle and the loader.
+type. However, this isn't mandatory. Users can easily get around this constraint
+by specializing both the handle and the loader.
 
 A cache forwards all its arguments to the loader if required. This means that
 loaders can also support tag dispatching to offer different loading policies:
@@ -140,7 +145,7 @@ entt::resource_cache<my_resource, my_loader> cache{};
 Under the hood, a cache is nothing more than a map where the key value has type
 `entt::id_type` while the mapped value is whatever type its loader returns.<br/>
 For this reason, it offers most of the functionalities a user would expect from
-a map, such as `empty` or `size` and so on. Similarly, it is an iterable type
+a map, such as `empty` or `size` and so on. Similarly, it's an iterable type
 that also supports indexing by resource id:
 
 ```cpp
@@ -159,9 +164,9 @@ functions (such as `contains` or `erase`).
 Set aside the part of the API that this class _shares_ with a map, it also adds
 something on top of it in order to address the most common requirements of a
 resource cache.<br/>
-In particular, it does not have an `emplace` member function which is replaced
-by `load` and `force_load` instead (where the former loads a new resource only
-if not present while the second triggers a forced loading in any case):
+In particular, it doesn't have an `emplace` member function which is replaced by
+`load` and `force_load` instead (where the former loads a new resource only if
+not present while the second triggers a forced loading in any case):
 
 ```cpp
 auto ret = cache.load("resource/id"_hs);
@@ -177,10 +182,10 @@ Note that the hashed string is used for convenience in the example above.<br/>
 Resource identifiers are nothing more than integral values. Therefore, plain
 numbers as well as non-class enum value are accepted.
 
-It is worth mentioning that the iterators of a cache as well as its indexing
+It's worth mentioning that the iterators of a cache as well as its indexing
 operators return resource handles rather than instances of the mapped type.<br/>
-Since the cache has no control over the loader and a resource is not required to
+Since the cache has no control over the loader and a resource isn't required to
 also be convertible to bool, these handles can be invalid. This usually means an
-error in the user logic, but it may also be an _expected_ event.<br/>
-It is therefore recommended to verify handles validity with a check in debug
-(for example, when loading) or an appropriate logic in retail.
+error in the user logic but it may also be an _expected_ event.<br/>
+It's therefore recommended to verify handles validity with a check in debug (for
+example, when loading) or an appropriate logic in retail.

docs/md/signal.md

@@ -1,5 +1,8 @@
 # Crash Course: events, signals and everything in between
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 # Table of Contents
 
 * [Introduction](#introduction)
@@ -11,6 +14,9 @@
 * [Event dispatcher](#event-dispatcher)
   * [Named queues](#named-queues)
 * [Event emitter](#event-emitter)
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 # Introduction
 
@@ -19,14 +25,14 @@ in general.<br/>
 They help to decouple the various parts of a system while allowing them to
 communicate with each other somehow.
 
-The so-called _modern C++_ comes with a tool that can be useful in this regard,
+The so called _modern C++_ comes with a tool that can be useful in this regard,
 the `std::function`. As an example, it can be used to create delegates.<br/>
-However, there is no guarantee that an `std::function` does not perform
+However, there is no guarantee that an `std::function` doesn't perform
 allocations under the hood and this could be problematic sometimes. Furthermore,
 it solves a problem but may not adapt well to other requirements that may arise
 from time to time.
 
-In case that the flexibility and power of an `std::function` is not required or
+In case that the flexibility and power of an `std::function` isn't required or
 if the price to pay for them is too high, `EnTT` offers a complete set of
 lightweight classes to solve the same and many other problems.
 
@@ -35,8 +41,8 @@ lightweight classes to solve the same and many other problems.
 A delegate can be used as a general purpose invoker with no memory overhead for
 free functions, lambdas and members provided along with an instance on which to
 invoke them.<br/>
-It does not claim to be a drop-in replacement for an `std::function`, so do not
-expect to use it whenever an `std::function` fits well. That said, it is most
+It doesn't claim to be a drop-in replacement for an `std::function`, so don't
+expect to use it whenever an `std::function` fits well. That said, it's most
 likely even a better fit than an `std::function` in a lot of cases, so expect to
 use it quite a lot anyway.
 
@@ -75,8 +81,8 @@ function type of the delegate is such that the parameter list is empty and the
 value of the data member is at least convertible to the return type.
 
 Free functions having type equivalent to `void(T &, args...)` are accepted as
-well. The first argument `T &` is considered a payload, and the function will
-receive it back every time it is invoked. In other terms, this works just fine
+well. The first argument `T &` is considered a payload and the function will
+receive it back every time it's invoked. In other terms, this works just fine
 with the above definition:
 
 ```cpp
@@ -106,8 +112,8 @@ is used as a building block of a signal-slot system.<br/>
 In fact, this filtering works both ways. The class tries to pass its first
 _count_ arguments **first**, then the last _count_. Watch out for conversion
 rules if in doubt when connecting a listener!<br/>
-Arbitrary functions that pull random arguments from the delegate list are not
-supported instead. Other features were preferred, such as support for functions
+Arbitrary functions that pull random arguments from the delegate list aren't
+supported instead. Other feature were preferred, such as support for functions
 with compatible argument lists although not equal to those of the delegate.
 
 To create and initialize a delegate at once, there are a few specialized
@@ -118,7 +124,7 @@ means of the `entt::connect_arg` variable template:
 entt::delegate<int(int)> func{entt::connect_arg<&f>};
 ```
 
-Aside `connect`, a `disconnect` counterpart is not provided. Instead, there
+Aside `connect`, a `disconnect` counterpart isn't provided. Instead, there
 exists a `reset` member function to use to clear a delegate.<br/>
 To know if a delegate is empty, it can be used explicitly in every conditional
 statement:
@@ -136,14 +142,14 @@ already shown in the examples above:
 auto ret = delegate(42);
 ```
 
-In all cases, listeners do not have to strictly follow the signature of the
+In all cases, listeners don't have to strictly follow the signature of the
 delegate. As long as a listener can be invoked with the given arguments to yield
 a result that is convertible to the given result type, everything works just
 fine.
 
 As a side note, members of classes may or may not be associated with instances.
 If they are not, the first argument of the function type must be that of the
-class on which the members operate, and an instance of this class must obviously
+class on which the members operate and an instance of this class must obviously
 be passed when invoking the delegate:
 
 ```cpp
@@ -154,8 +160,8 @@ my_struct instance;
 delegate(instance, 42);
 ```
 
-In this case, it is not possible to _deduce_ the function type since the first
-argument does not necessarily have to be a reference (for example, it can be a
+In this case, it's not possible to _deduce_ the function type since the first
+argument doesn't necessarily have to be a reference (for example, it can be a
 pointer, as well as a const reference).<br/>
 Therefore, the function type must be declared explicitly for unbound members.
 
@@ -164,13 +170,13 @@ Therefore, the function type must be declared explicitly for unbound members.
 The `delegate` class is meant to be used primarily with template arguments.
 However, as a consequence of its design, it also offers minimal support for
 runtime arguments.<br/>
-When used like this, some features are not supported though. In particular:
+When used like this, some features aren't supported though. In particular:
 
-* Curried functions are not accepted.
-* Functions with an argument list that differs from that of the delegate are not
+* Curried functions aren't accepted.
+* Functions with an argument list that differs from that of the delegate aren't
   supported.
 * Return type and types of arguments **must** coincide with those of the
-  delegate and _being at least convertible_ is not enough anymore.
+  delegate and _being at least convertible_ isn't enough anymore.
 
 Moreover, for a given function type `Ret(Args...)`, the signature of the
 functions connected at runtime must necessarily be `Ret(const void *, Args...)`.
@@ -200,12 +206,12 @@ explained.
 
 ## Lambda support
 
-In general, the `delegate` class does not fully support lambda functions in all
-their nuances. The reason is pretty simple: a `delegate` is not a drop-in
+In general, the `delegate` class doesn't fully support lambda functions in all
+their nuances. The reason is pretty simple: a `delegate` isn't a drop-in
 replacement for an `std::function`. Instead, it tries to overcome the problems
 with the latter.<br/>
 That being said, non-capturing lambda functions are supported, even though some
-features are not available in this case.
+features aren't available in this case.
 
 This is a logical consequence of the support for connecting functions at
 runtime. Therefore, lambda functions undergo the same rules and
@@ -228,7 +234,7 @@ delegate.connect([](const void *ptr, int value) {
 }, &instance);
 ```
 
-As above, the first parameter (`const void *`) is not part of the function type
+As above, the first parameter (`const void *`) isn't part of the function type
 of the delegate and is used to dispatch arbitrary user data back and forth. In
 other terms, the function type of the delegate above is `int(int)`.
 
@@ -252,12 +258,12 @@ particular delegate through its descriptive _traits_ instead.
 
 # Signals
 
-Signal handlers work with references to classes, function pointers, and pointers
-to members. Listeners can be any kind of objects, and users are in charge of
+Signal handlers work with references to classes, function pointers and pointers
+to members. Listeners can be any kind of objects and users are in charge of
 connecting and disconnecting them from a signal to avoid crashes due to
-different lifetimes. On the other side, performance should not be affected that
+different lifetimes. On the other side, performance shouldn't be affected that
 much by the presence of such a signal handler.<br/>
-Signals make use of delegates internally, and therefore they undergo the same
+Signals make use of delegates internally and therefore they undergo the same
 rules and offer similar functionalities. It may be a good idea to consult the
 documentation of the `delegate` class for further information.
 
@@ -271,7 +277,7 @@ The API of a signal handler is straightforward. If a collector is supplied to
 the signal when something is published, all the values returned by its listeners
 are literally _collected_ and used later by the caller. Otherwise, the class
 works just like a plain signal that emits events from time to time.<br/>
-To create instances of signal handlers it is sufficient to provide the type of
+To create instances of signal handlers it's sufficient to provide the type of
 function to which they refer:
 
 ```cpp
@@ -315,7 +321,7 @@ sink.disconnect(&instance);
 sink.disconnect();
 ```
 
-As shown above, listeners do not have to strictly follow the signature of the
+As shown above, listeners don't have to strictly follow the signature of the
 signal. As long as a listener can be invoked with the given arguments to yield a
 result that is convertible to the given return type, everything works just
 fine.<br/>
@@ -357,7 +363,7 @@ assert(vec[1] == 1);
 A collector must expose a function operator that accepts as an argument a type
 to which the return type of the listeners can be converted. Moreover, it can
 optionally return a boolean value that is true to stop collecting data, false
-otherwise. This way one can avoid calling all the listeners in case it is not
+otherwise. This way one can avoid calling all the listeners in case it isn't
 necessary.<br/>
 Functors can also be used in place of a lambda. Since the collector is copied
 when invoking the `collect` member function, `std::ref` is the way to go in this
@@ -383,7 +389,7 @@ signal.collect(std::ref(collector));
 
 The event dispatcher class allows users to trigger immediate events or to queue
 and publish them all together later.<br/>
-This class lazily instantiates its queues. Therefore, it is not necessary to
+This class lazily instantiates its queues. Therefore, it's not necessary to
 _announce_ the event types in advance:
 
 ```cpp
@@ -430,7 +436,7 @@ dispatcher.trigger(an_event{42});
 dispatcher.trigger<another_event>();
 ```
 
-Listeners are invoked immediately, order of execution is not guaranteed. This
+Listeners are invoked immediately, order of execution isn't guaranteed. This
 method can be used to push around urgent messages like an _is terminating_
 notification on a mobile app.
 
@@ -459,7 +465,7 @@ once per tick to their systems.
 
 All queues within a dispatcher are associated by default with an event type and
 then retrieved from it.<br/>
-However, it is possible to create queues with different _names_ (and therefore
+However, it's possible to create queues with different _names_ (and therefore
 also multiple queues for a single type). In fact, more or less all functions
 also take an additional parameter. As an example:
 
@@ -476,8 +482,8 @@ parameter for it but rather a different function:
 dispatcher.enqueue_hint<an_event>("custom"_hs, 42);
 ```
 
-This is mainly due to the template argument deduction rules, and there is no
-real (elegant) way to avoid it.
+This is mainly due to the template argument deduction rules and unfortunately
+there is no real (elegant) way to avoid it.
 
 # Event emitter
 
@@ -495,7 +501,7 @@ struct my_emitter: emitter<my_emitter> {
 }
 ```
 
-Handlers for the different events are created internally on the fly. It is not
+Handlers for the different events are created internally on the fly. It's not
 required to specify in advance the full list of accepted events.<br/>
 Moreover, whenever an event is published, an emitter also passes a reference
 to itself to its listeners.
@@ -555,5 +561,5 @@ if(emitter.contains<my_event>()) {
 ```
 
 This class introduces a _nice-to-have_ model based on events and listeners.<br/>
-More in general, it is a handy tool when the derived classes _wrap_ asynchronous
-operations, but it is not limited to such uses.
+More in general, it's a handy tool when the derived classes _wrap_ asynchronous
+operations but it's not limited to such uses.

docs/md/unreal.md

@@ -1,15 +1,19 @@
 # EnTT and Unreal Engine
 
+<!--
+@cond TURN_OFF_DOXYGEN
+-->
 # Table of Contents
 
 * [Enable Cpp17](#enable-cpp17)
 * [EnTT as a third party module](#entt-as-a-third-party-module)
 * [Include EnTT](#include-entt)
+<!--
+@endcond TURN_OFF_DOXYGEN
+-->
 
 ## Enable Cpp17
 
-> Skip this part if you are working with UE5, Since UE5 uses cpp17 by default.
-
 As of writing (Unreal Engine v4.25), the default C++ standard of Unreal Engine
 is C++14.<br/>
 On the other hand, note that `EnTT` requires C++17 to compile. To enable it, in
@@ -24,7 +28,7 @@ CppStandard = CppStandardVersion.Cpp17;
 
 Replace `<PCH filename>.h` with the name of the already existing PCH header
 file, if any.<br/>
-In case the project does not already contain a file of this type, it is possible
+In case the project doesn't already contain a file of this type, it's possible
 to create one with the following content:
 
 ```cpp
@@ -37,8 +41,8 @@ this point, C++17 support should be in place.<br/>
 Try to compile the project to ensure it works as expected before following
 further steps.
 
-Note that updating a *project* to C++17 does not necessarily mean that the IDE
-in use will also start to recognize its syntax.<br/>
+Note that updating a *project* to C++17 doesn't necessarily mean that the IDE in
+use will also start to recognize its syntax.<br/>
 If the plan is to use C++17 in the project too, check the specific instructions
 for the IDE in use.
 
@@ -62,8 +66,8 @@ Source
       \---entt (GitHub repository content inside)
 ```
 
-To make this happen, create the folder `ThirdParty` under `Source` if it does
-not exist already. Then, add an `EnTT` folder under `ThirdParty`.<br/>
+To make this happen, create the folder `ThirdParty` under `Source` if it doesn't
+exist already. Then, add an `EnTT` folder under `ThirdParty`.<br/>
 Within the latter, create a new file `EnTT.Build.cs` with the following content:
 
 ```cs

entt.imp

@@ -1,52 +1,34 @@
 [
-  # gtest only
   { "include": [ "@<gtest/internal/.*>", "private", "<gtest/gtest.h>", "public" ] },
   { "include": [ "@<gtest/gtest-.*>", "private", "<gtest/gtest.h>", "public" ] },
-  # forward files
-  { "include": [ "@[\"<].*/container/fwd\\.hpp[\">]", "private", "<entt/container/dense_map.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/container/fwd\\.hpp[\">]", "private", "<entt/container/dense_set.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/container/fwd\\.hpp[\">]", "private", "<entt/container/table.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/core/fwd\\.hpp[\">]", "private", "<entt/core/any.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/core/fwd\\.hpp[\">]", "private", "<entt/core/compressed_pair.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/core/fwd\\.hpp[\">]", "private", "<entt/core/family.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/core/fwd\\.hpp[\">]", "private", "<entt/core/hashed_string.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/core/fwd\\.hpp[\">]", "private", "<entt/core/ident.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/core/fwd\\.hpp[\">]", "private", "<entt/core/monostate.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/core/fwd\\.hpp[\">]", "private", "<entt/core/type_info.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/core/fwd\\.hpp[\">]", "private", "<entt/core/type_traits.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/entity/fwd\\.hpp[\">]", "private", "<entt/entity/component.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/entity/fwd\\.hpp[\">]", "private", "<entt/entity/entity.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/entity/fwd\\.hpp[\">]", "private", "<entt/entity/group.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/entity/fwd\\.hpp[\">]", "private", "<entt/entity/handle.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/entity/fwd\\.hpp[\">]", "private", "<entt/entity/helper.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/entity/fwd\\.hpp[\">]", "private", "<entt/entity/mixin.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/entity/fwd\\.hpp[\">]", "private", "<entt/entity/organizer.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/entity/fwd\\.hpp[\">]", "private", "<entt/entity/ranges.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/entity/fwd\\.hpp[\">]", "private", "<entt/entity/registry.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/entity/fwd\\.hpp[\">]", "private", "<entt/entity/runtime_view.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/entity/fwd\\.hpp[\">]", "private", "<entt/entity/snapshot.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/entity/fwd\\.hpp[\">]", "private", "<entt/entity/sparse_set.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/entity/fwd\\.hpp[\">]", "private", "<entt/entity/storage.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/entity/fwd\\.hpp[\">]", "private", "<entt/entity/view.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/graph/fwd\\.hpp[\">]", "private", "<entt/graph/adjacency_matrix.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/graph/fwd\\.hpp[\">]", "private", "<entt/graph/dot.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/graph/fwd\\.hpp[\">]", "private", "<entt/graph/flow.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/meta/fwd\\.hpp[\">]", "private", "<entt/meta/meta.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/poly/fwd\\.hpp[\">]", "private", "<entt/poly/poly.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/process/fwd\\.hpp[\">]", "private", "<entt/process/process.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/process/fwd\\.hpp[\">]", "private", "<entt/process/scheduler.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/resource/fwd\\.hpp[\">]", "private", "<entt/resource/cache.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/resource/fwd\\.hpp[\">]", "private", "<entt/resource/loader.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/resource/fwd\\.hpp[\">]", "private", "<entt/resource/resource.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/signal/fwd\\.hpp[\">]", "private", "<entt/signal/delegate.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/signal/fwd\\.hpp[\">]", "private", "<entt/signal/dispatcher.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/signal/fwd\\.hpp[\">]", "private", "<entt/signal/emitter.hpp>", "public" ] },
-  { "include": [ "@[\"<].*/signal/fwd\\.hpp[\">]", "private", "<entt/signal/sigh.hpp>", "public" ] },
-  # symbols
-  { symbol: [ "std::allocator", private, "<entt/container/fwd.hpp>", public ] },
-  { symbol: [ "std::allocator", private, "<entt/entity/fwd.hpp>", public ] },
-  { symbol: [ "std::allocator", private, "<entt/graph/fwd.hpp>", public ] },
-  { symbol: [ "std::allocator", private, "<entt/process/fwd.hpp>", public ] },
-  { symbol: [ "std::allocator", private, "<entt/resource/fwd.hpp>", public ] },
-  { symbol: [ "std::allocator", private, "<entt/signal/fwd.hpp>", public ] }
+  { "include": [ "@[\"<].*/container/fwd.hpp[\">]", "private", "<entt/container/dense_map.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/container/fwd.hpp[\">]", "private", "<entt/container/dense_set.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/core/fwd.hpp[\">]", "private", "<entt/core/any.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/core/fwd.hpp[\">]", "private", "<entt/core/family.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/core/fwd.hpp[\">]", "private", "<entt/core/hashed_string.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/core/fwd.hpp[\">]", "private", "<entt/core/ident.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/core/fwd.hpp[\">]", "private", "<entt/core/monostate.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/core/fwd.hpp[\">]", "private", "<entt/core/type_info.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/core/fwd.hpp[\">]", "private", "<entt/core/type_traits.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/entity/fwd.hpp[\">]", "private", "<entt/entity/entity.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/entity/fwd.hpp[\">]", "private", "<entt/entity/group.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/entity/fwd.hpp[\">]", "private", "<entt/entity/handle.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/entity/fwd.hpp[\">]", "private", "<entt/entity/helper.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/entity/fwd.hpp[\">]", "private", "<entt/entity/observer.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/entity/fwd.hpp[\">]", "private", "<entt/entity/organizer.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/entity/fwd.hpp[\">]", "private", "<entt/entity/registry.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/entity/fwd.hpp[\">]", "private", "<entt/entity/runtime_view.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/entity/fwd.hpp[\">]", "private", "<entt/entity/snapshot.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/entity/fwd.hpp[\">]", "private", "<entt/entity/sparse_set.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/entity/fwd.hpp[\">]", "private", "<entt/entity/storage.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/entity/fwd.hpp[\">]", "private", "<entt/entity/view.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/meta/fwd.hpp[\">]", "private", "<entt/meta/meta.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/poly/fwd.hpp[\">]", "private", "<entt/poly/poly.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/resource/fwd.hpp[\">]", "private", "<entt/resource/cache.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/resource/fwd.hpp[\">]", "private", "<entt/resource/loader.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/resource/fwd.hpp[\">]", "private", "<entt/resource/resource.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/signal/fwd.hpp[\">]", "private", "<entt/signal/delegate.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/signal/fwd.hpp[\">]", "private", "<entt/signal/dispatcher.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/signal/fwd.hpp[\">]", "private", "<entt/signal/emitter.hpp>", "public" ] },
+  { "include": [ "@[\"<].*/signal/fwd.hpp[\">]", "private", "<entt/signal/sigh.hpp>", "public" ] }
 ]

natvis/entt/container.natvis

@@ -30,10 +30,4 @@
 			</IndexListItems>
 		</Expand>
 	</Type>
-	<Type Name="entt::basic_table&lt;*&gt;">
-		<DisplayString>{ payload }</DisplayString>
-		<Expand>
-			<ExpandedItem>payload</ExpandedItem>
-		</Expand>
-	</Type>
 </AutoVisualizer>

natvis/entt/core.natvis

@@ -8,7 +8,7 @@
 		<Intrinsic Name="first" Optional="true" Expression="*(first_base::base_type*)this"/>
 		<Intrinsic Name="second" Optional="true" Expression="((second_base*)this)->value"/>
 		<Intrinsic Name="second" Optional="true" Expression="*(second_base::base_type*)this"/>
-		<DisplayString>({ first() }, { second() })</DisplayString>
+		<DisplayString >({ first() }, { second() })</DisplayString>
 		<Expand>
 			<Item Name="[first]">first()</Item>
 			<Item Name="[second]">second()</Item>

natvis/entt/entity.natvis

@@ -1,61 +1,47 @@
 <?xml version="1.0" encoding="utf-8"?>
 <AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
 	<Type Name="entt::basic_registry&lt;*&gt;">
+		<Intrinsic Name="to_entity" Expression="*((traits_type::entity_type *)&amp;entity) &amp; traits_type::entity_mask">
+			<Parameter Name="entity" Type="traits_type::value_type &amp;"/>
+		</Intrinsic>
 		<DisplayString>{{ pools={ pools.size() } }}</DisplayString>
 		<Expand>
 			<Item Name="[entities]">entities</Item>
 			<Synthetic Name="[pools]">
 				<DisplayString>{ pools.size() }</DisplayString>
 				<Expand>
-					<CustomListItems>
-						<Variable Name="pos" InitialValue="0" />
-						<Variable Name="last" InitialValue="pools.size()"/>
-						<Loop>
-							<Break Condition="pos == last"/>
-							<Item Name="[{ pools.packed.first_base::value[pos].element.first }]">
-								*pools.packed.first_base::value[pos].element.second,view(simple)
-							</Item>
-							<Exec>++pos</Exec>
-						</Loop>
-					</CustomListItems>
+					<IndexListItems ExcludeView="simple">
+						<Size>pools.size()</Size>
+						<ValueNode>*pools.packed.first_base::value[$i].element.second</ValueNode>
+					</IndexListItems>
+					<IndexListItems IncludeView="simple">
+						<Size>pools.size()</Size>
+						<ValueNode>*pools.packed.first_base::value[$i].element.second,view(simple)</ValueNode>
+					</IndexListItems>
 				</Expand>
 			</Synthetic>
-			<Item Name="[groups]">groups.size()</Item>
+			<Item Name="[groups]" ExcludeView="simple">groups.size()</Item>
 			<Synthetic Name="[vars]">
 				<DisplayString>{ vars.ctx.size() }</DisplayString>
 				<Expand>
-					<CustomListItems>
-						<Variable Name="pos" InitialValue="0" />
-						<Variable Name="last" InitialValue="vars.ctx.size()"/>
-						<Loop>
-							<Break Condition="pos == last"/>
-							<Item Name="[{ vars.ctx.packed.first_base::value[pos].element.first }]">
-								vars.ctx.packed.first_base::value[pos].element.second
-							</Item>
-							<Exec>++pos</Exec>
-						</Loop>
-					</CustomListItems>
+					<IndexListItems>
+						<Size>vars.ctx.size()</Size>
+						<ValueNode>vars.ctx.packed.first_base::value[$i].element.second</ValueNode>
+					</IndexListItems>
 				</Expand>
 			</Synthetic>
 		</Expand>
 	</Type>
 	<Type Name="entt::basic_sparse_set&lt;*&gt;">
-		<Intrinsic Name="is_valid_position" Expression="sparse[page] &amp;&amp; ((*((traits_type::entity_type *)&amp;sparse[page][offset]) &amp; traits_type::entity_mask) != traits_type::entity_mask)">
-			<Parameter Name="page" Type="traits_type::entity_type"/>
-			<Parameter Name="offset" Type="traits_type::entity_type"/>
-		</Intrinsic>
-		<Intrinsic Name="is_valid_entity" Expression="!traits_type::version_mask || (*((traits_type::entity_type *)&amp;entity) &lt; (traits_type::version_mask &lt;&lt; traits_type::length))">
-			<Parameter Name="entity" Type="const traits_type::value_type &amp;"/>
-		</Intrinsic>
 		<DisplayString>{{ size={ packed.size() }, type={ info->alias,na } }}</DisplayString>
 		<Expand>
 			<Item Name="[capacity]" ExcludeView="simple">packed.capacity()</Item>
-			<Item Name="[policy]" ExcludeView="simple">mode,en</Item>
-			<Item Name="[free_list]" ExcludeView="simple">head</Item>
+			<Item Name="[policy]">mode,en</Item>
 			<Synthetic Name="[sparse]">
 				<DisplayString>{ sparse.size() * traits_type::page_size }</DisplayString>
 				<Expand>
-					<CustomListItems>
+					<ExpandedItem IncludeView="simple">sparse,view(simple)</ExpandedItem>
+					<CustomListItems ExcludeView="simple">
 						<Variable Name="pos" InitialValue="0"/>
 						<Variable Name="page" InitialValue="0"/>
 						<Variable Name="offset" InitialValue="0"/>
@@ -64,7 +50,7 @@
 							<Break Condition="pos == last"/>
 							<Exec>page = pos / traits_type::page_size</Exec>
 							<Exec>offset = pos &amp; (traits_type::page_size - 1)</Exec>
-							<If Condition="is_valid_position(page, offset)">
+							<If Condition="sparse[page] &amp;&amp; (*((traits_type::entity_type *)&amp;sparse[page][offset]) &lt; ~traits_type::entity_mask)">
 								<Item Name="[{ pos }]">*((traits_type::entity_type *)&amp;sparse[page][offset]) &amp; traits_type::entity_mask</Item>
 							</If>
 							<Exec>++pos</Exec>
@@ -75,12 +61,13 @@
 			<Synthetic Name="[packed]">
 				<DisplayString>{ packed.size() }</DisplayString>
 				<Expand>
-					<CustomListItems>
+					<ExpandedItem IncludeView="simple">packed,view(simple)</ExpandedItem>
+					<CustomListItems ExcludeView="simple">
 						<Variable Name="pos" InitialValue="0"/>
 						<Variable Name="last" InitialValue="packed.size()"/>
 						<Loop>
 							<Break Condition="pos == last"/>
-							<If Condition="is_valid_entity(packed[pos])">
+							<If Condition="*((traits_type::entity_type *)&amp;packed[pos]) &lt; ~traits_type::entity_mask">
 								<Item Name="[{ pos }]">packed[pos]</Item>
 							</If>
 							<Exec>++pos</Exec>
@@ -91,22 +78,20 @@
 		</Expand>
 	</Type>
 	<Type Name="entt::basic_storage&lt;*&gt;">
-		<Intrinsic Name="is_valid_entity" Expression="!base_type::traits_type::version_mask || (*((base_type::traits_type::entity_type *)&amp;entity) &lt; (base_type::traits_type::version_mask &lt;&lt; base_type::traits_type::length))">
-			<Parameter Name="entity" Type="const base_type::traits_type::value_type &amp;"/>
-		</Intrinsic>
 		<DisplayString>{{ size={ base_type::packed.size() }, type={ base_type::info->alias,na } }}</DisplayString>
 		<Expand>
 			<Item Name="[capacity]" Optional="true" ExcludeView="simple">payload.capacity() * traits_type::page_size</Item>
 			<Item Name="[page size]" Optional="true" ExcludeView="simple">traits_type::page_size</Item>
-			<Item Name="[placeholder]" Optional="true" ExcludeView="simple">placeholder</Item>
+			<Item Name="[length]" Optional="true" ExcludeView="simple">length</Item>
 			<Item Name="[base]" ExcludeView="simple">(base_type*)this,nand</Item>
 			<Item Name="[base]" IncludeView="simple">(base_type*)this,view(simple)nand</Item>
+			<!-- having SFINAE-like techniques in natvis is priceless :) -->
 			<CustomListItems Condition="payload.size() != 0" Optional="true">
 				<Variable Name="pos" InitialValue="0" />
 				<Variable Name="last" InitialValue="base_type::packed.size()"/>
 				<Loop>
 					<Break Condition="pos == last"/>
-					<If Condition="is_valid_entity(base_type::packed[pos])">
+					<If Condition="*((base_type::traits_type::entity_type *)&amp;base_type::packed[pos]) &lt; ~base_type::traits_type::entity_mask">
 						<Item Name="[{ pos }:{ base_type::packed[pos] }]">payload[pos / traits_type::page_size][pos &amp; (traits_type::page_size - 1)]</Item>
 					</If>
 					<Exec>++pos</Exec>
@@ -114,26 +99,11 @@
 			</CustomListItems>
 		</Expand>
 	</Type>
-	<Type Name="entt::basic_common_view&lt;*,*,*&gt;">
-		<DisplayString Condition="index != $T2">{{ size_hint={ pools[index]->packed.size() } }}</DisplayString>
-		<DisplayString>{{ size_hint=0 }}</DisplayString>
+	<Type Name="entt::basic_view&lt;*&gt;">
+		<DisplayString>{{ size_hint={ view->packed.size() } }}</DisplayString>
 		<Expand>
 			<Item Name="[pools]">pools,na</Item>
 			<Item Name="[filter]">filter,na</Item>
-			<Item Name="[handle]" Condition="index != $T2">pools[index],na</Item>
-		</Expand>
-	</Type>
-	<Type Name="entt::basic_storage_view&lt;*&gt;">
-		<DisplayString Condition="leading != nullptr">{{ size={ leading->packed.size() } }}</DisplayString>
-		<DisplayString>{{ size=0 }}</DisplayString>
-		<Expand>
-			<Item Name="[handle]" Condition="leading != nullptr">leading,na</Item>
-		</Expand>
-	</Type>
-	<Type Name="entt::basic_view&lt;*&gt;">
-		<DisplayString>{ *(base_type*)this }</DisplayString>
-		<Expand>
-			<ExpandedItem>*(base_type*)this</ExpandedItem>
 		</Expand>
 	</Type>
 	<Type Name="entt::basic_runtime_view&lt;*&gt;">
@@ -144,34 +114,6 @@
 			<Item Name="[filter]">filter,na</Item>
 		</Expand>
 	</Type>
-	<Type Name="entt::basic_handle&lt;*&gt;">
-		<Intrinsic Name="pool_at" Expression="owner->pools.packed.first_base::value[index].element.second._Ptr">
-			<Parameter Name="index" Type="unsigned int"/>
-		</Intrinsic>
-		<DisplayString>{{ entity={ entt } }}</DisplayString>
-		<Expand>
-			<Item Name="[entity]">entt</Item>
-			<Item Name="[registry]" Condition="owner != nullptr">owner,na</Item>
-			<Synthetic Name="[components]" Condition="owner != nullptr">
-				<Expand>
-					<CustomListItems>
-						<Variable Name="entity_mask" InitialValue="traits_type::entity_mask"/>
-						<Variable Name="page" InitialValue="((*((traits_type::entity_type *)&amp;entt)) &amp; entity_mask) / traits_type::page_size"/>
-						<Variable Name="offset" InitialValue="(*((traits_type::entity_type *)&amp;entt)) &amp; (traits_type::page_size - 1u)"/>
-						<Variable Name="last" InitialValue="owner->pools.packed.first_base::value.size()"/>
-						<Variable Name="pos" InitialValue="0u"/>
-						<Loop>
-							<Break Condition="pos == last"/>
-							<If Condition="pool_at(pos)->sparse.size() &gt; page &amp;&amp; pool_at(pos)->sparse[page] != nullptr &amp;&amp; ((*((traits_type::entity_type *)&amp;pool_at(pos)->sparse[page][offset])) &amp; entity_mask) != entity_mask">
-								<Item Name="[{ pool_at(pos)->info->alias,na }:{ ((*((traits_type::entity_type *)&amp;pool_at(pos)->sparse[page][offset])) &amp; entity_mask) != entity_mask }]">pool_at(pos),view(simple)nanr</Item>
-							</If>
-							<Exec>++pos</Exec>
-						</Loop>
-					</CustomListItems>
-				</Expand>
-			</Synthetic>
-		</Expand>
-	</Type>
 	<Type Name="entt::null_t">
 		<DisplayString>&lt;null&gt;</DisplayString>
 	</Type>

natvis/entt/meta.natvis

@@ -1,87 +1,46 @@
 <?xml version="1.0" encoding="utf-8"?>
 <AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
 	<Type Name="entt::internal::meta_base_node">
-		<DisplayString Condition="resolve != nullptr">{{ type={ type } }}</DisplayString>
 		<DisplayString>{{}}</DisplayString>
-		<Expand>
-			<Item Name="[type]">type</Item>
-		</Expand>
 	</Type>
 	<Type Name="entt::internal::meta_conv_node">
-		<DisplayString Condition="conv != nullptr">{{ type={ type } }}</DisplayString>
 		<DisplayString>{{}}</DisplayString>
-		<Expand>
-			<Item Name="[type]">type</Item>
-		</Expand>
 	</Type>
 	<Type Name="entt::internal::meta_ctor_node">
-		<DisplayString Condition="invoke != nullptr">{{ id={ id } }}</DisplayString>
-		<DisplayString>{{}}</DisplayString>
-		<Expand>
-			<Item Name="[id]">id</Item>
-			<Item Name="[arity]">arity</Item>
-		</Expand>
-	</Type>
-	<Type Name="entt::internal::meta_custom_node">
-		<DisplayString Condition="value != nullptr">{{ type={ type } }}</DisplayString>
-		<DisplayString>{{}}</DisplayString>
-		<Expand>
-			<Item Name="[type]">type</Item>
-			<Item Name="[value]">value</Item>
-		</Expand>
+		<DisplayString>{{ arity={ arity } }}</DisplayString>
 	</Type>
 	<Type Name="entt::internal::meta_data_node">
-		<Intrinsic Name="has_trait" Expression="!!(traits &amp; property)">
+		<Intrinsic Name="has_property" Expression="!!(traits &amp; property)">
 			<Parameter Name="property" Type="int"/>
 		</Intrinsic>
-		<DisplayString Condition="get != nullptr">{{ id={ id } }}</DisplayString>
-		<DisplayString>{{}}</DisplayString>
+		<DisplayString>{{ arity={ arity } }}</DisplayString>
 		<Expand>
-			<Item Name="[id]">id</Item>
 			<Item Name="[arity]">arity</Item>
-			<Item Name="[is_const]">has_trait(entt::internal::meta_traits::is_const)</Item>
-			<Item Name="[is_static]">has_trait(entt::internal::meta_traits::is_static)</Item>
-			<Item Name="[custom]">custom</Item>
+			<Item Name="[is_const]">has_property(entt::internal::meta_traits::is_const)</Item>
+			<Item Name="[is_static]">has_property(entt::internal::meta_traits::is_static)</Item>
+			<Item Name="[prop]">prop</Item>
 		</Expand>
 	</Type>
-	<Type Name="entt::internal::meta_dtor_node">
-		<DisplayString>{{}}</DisplayString>
-		<Expand/>
-	</Type>	
 	<Type Name="entt::internal::meta_func_node"	>
-		<Intrinsic Name="has_trait" Expression="!!(traits &amp; property)">
+		<Intrinsic Name="has_property" Expression="!!(traits &amp; property)">
 			<Parameter Name="property" Type="int"/>
 		</Intrinsic>
-		<DisplayString Condition="invoke != nullptr">{{ id={ id } }}</DisplayString>
-		<DisplayString>{{}}</DisplayString>
+		<DisplayString>{{ arity={ arity } }}</DisplayString>
 		<Expand>
-			<Item Name="[id]">id</Item>
-			<Item Name="[arity]">arity</Item>
-			<Item Name="[is_const]">has_trait(entt::internal::meta_traits::is_const)</Item>
-			<Item Name="[is_static]">has_trait(entt::internal::meta_traits::is_static)</Item>
+			<Item Name="[is_const]">has_property(entt::internal::meta_traits::is_const)</Item>
+			<Item Name="[is_static]">has_property(entt::internal::meta_traits::is_static)</Item>
 			<Item Name="[next]" Condition="next != nullptr">*next</Item>
-			<Item Name="[custom]">custom</Item>
+			<Item Name="[prop]">prop</Item>
 		</Expand>
 	</Type>
+	<Type Name="entt::internal::meta_prop_node">
+		<DisplayString>{ value }</DisplayString>
+	</Type>
 	<Type Name="entt::internal::meta_template_node">
-		<DisplayString Condition="arity != 0u">{{ arity={ arity } }}</DisplayString>
-		<DisplayString>{{}}</DisplayString>
-		<Expand>
-			<Item Name="[arity]">arity</Item>
-		</Expand>
-	</Type>
-	<Type Name="entt::internal::meta_type_descriptor">
-		<DisplayString/>
-		<Expand>
-			<Item Name="[ctor]">ctor,view(simple)</Item>
-			<Item Name="[base]">base,view(simple)</Item>
-			<Item Name="[conv]">conv,view(simple)</Item>
-			<Item Name="[data]">data,view(simple)</Item>
-			<Item Name="[func]">func,view(simple)</Item>
-		</Expand>
+		<DisplayString>{{ arity={ arity } }}</DisplayString>
 	</Type>
 	<Type Name="entt::internal::meta_type_node">
-		<Intrinsic Name="has_trait" Expression="!!(traits &amp; property)">
+		<Intrinsic Name="has_property" Expression="!!(traits &amp; property)">
 			<Parameter Name="property" Type="int"/>
 		</Intrinsic>
 		<DisplayString Condition="info != nullptr">{{ type={ info->alias,na } }}</DisplayString>
@@ -89,22 +48,20 @@
 		<Expand>
 			<Item Name="[id]">id</Item>
 			<Item Name="[sizeof]">size_of</Item>
-			<Item Name="[is_arithmetic]">has_trait(entt::internal::meta_traits::is_arithmetic)</Item>
-			<Item Name="[is_integral]">has_trait(entt::internal::meta_traits::is_integral)</Item>
-			<Item Name="[is_signed]">has_trait(entt::internal::meta_traits::is_signed)</Item>
-			<Item Name="[is_array]">has_trait(entt::internal::meta_traits::is_array)</Item>
-			<Item Name="[is_enum]">has_trait(entt::internal::meta_traits::is_enum)</Item>
-			<Item Name="[is_class]">has_trait(entt::internal::meta_traits::is_class)</Item>
-			<Item Name="[is_pointer]">has_trait(entt::internal::meta_traits::is_pointer)</Item>
-			<Item Name="[is_pointer_like]">has_trait(entt::internal::meta_traits::is_pointer_like)</Item>
-			<Item Name="[is_sequence_container]">has_trait(entt::internal::meta_traits::is_sequence_container)</Item>
-			<Item Name="[is_associative_container]">has_trait(entt::internal::meta_traits::is_associative_container)</Item>
+			<Item Name="[is_arithmetic]">has_property(entt::internal::meta_traits::is_arithmetic)</Item>
+			<Item Name="[is_integral]">has_property(entt::internal::meta_traits::is_integral)</Item>
+			<Item Name="[is_signed]">has_property(entt::internal::meta_traits::is_signed)</Item>
+			<Item Name="[is_array]">has_property(entt::internal::meta_traits::is_array)</Item>
+			<Item Name="[is_enum]">has_property(entt::internal::meta_traits::is_enum)</Item>
+			<Item Name="[is_class]">has_property(entt::internal::meta_traits::is_class)</Item>
+			<Item Name="[is_meta_pointer_like]">has_property(entt::internal::meta_traits::is_meta_pointer_like)</Item>
+			<Item Name="[is_meta_sequence_container]">has_property(entt::internal::meta_traits::is_meta_sequence_container)</Item>
+			<Item Name="[is_meta_associative_container]">has_property(entt::internal::meta_traits::is_meta_associative_container)</Item>
 			<Item Name="[default_constructor]">default_constructor != nullptr</Item>
 			<Item Name="[conversion_helper]">conversion_helper != nullptr</Item>
 			<Item Name="[from_void]">from_void != nullptr</Item>
 			<Item Name="[template_info]">templ</Item>
-			<Item Name="[custom]">custom</Item>
-			<Item Name="[details]" Condition="!(details == nullptr)">*details</Item>
+			<Item Name="[details]" Condition="details != nullptr">*details</Item>
 		</Expand>
 	</Type>
 	<Type Name="entt::meta_any">
@@ -117,47 +74,40 @@
 	</Type>
 	<Type Name="entt::meta_handle">
 		<DisplayString>{ any }</DisplayString>
-		<Expand>
-			<ExpandedItem>any</ExpandedItem>
-		</Expand>
 	</Type>
 	<Type Name="entt::meta_associative_container">
-		<DisplayString Condition="data != nullptr">{{ const={ const_only } }}</DisplayString>
-		<DisplayString>{{}}</DisplayString>
+		<DisplayString>{ storage }</DisplayString>
 		<Expand>
 			<Item Name="[context]" Condition="ctx != nullptr">ctx->value</Item>
-			<Item Name="[const]">const_only</Item>
-			<Item Name="[data]">data</Item>
 		</Expand>
 	</Type>
 	<Type Name="entt::meta_sequence_container">
-		<DisplayString Condition="data != nullptr">{{ const={ const_only } }}</DisplayString>
-		<DisplayString>{{}}</DisplayString>
+		<DisplayString>{ storage }</DisplayString>
 		<Expand>
 			<Item Name="[context]" Condition="ctx != nullptr">ctx->value</Item>
-			<Item Name="[const]">const_only</Item>
-			<Item Name="[data]">data</Item>
-		</Expand>
-	</Type>
-	<Type Name="entt::meta_custom">
-		<DisplayString>{ node }</DisplayString>
-		<Expand>
-			<ExpandedItem>node</ExpandedItem>
 		</Expand>
 	</Type>
 	<Type Name="entt::meta_data">
-		<DisplayString Condition="node.get != nullptr">{ node }</DisplayString>
+		<DisplayString Condition="node != nullptr">{ *node }</DisplayString>
 		<DisplayString>{{}}</DisplayString>
 		<Expand>
-			<ExpandedItem Condition="node.get != nullptr">node</ExpandedItem>
+			<ExpandedItem Condition="node != nullptr">node</ExpandedItem>
 			<Item Name="[context]" Condition="ctx != nullptr">ctx->value</Item>
 		</Expand>
 	</Type>
 	<Type Name="entt::meta_func">
-		<DisplayString Condition="node.invoke != nullptr">{ node }</DisplayString>
+		<DisplayString Condition="node != nullptr">{ *node }</DisplayString>
 		<DisplayString>{{}}</DisplayString>
 		<Expand>
-			<ExpandedItem Condition="node.invoke != nullptr">node</ExpandedItem>
+			<ExpandedItem Condition="node != nullptr">node</ExpandedItem>
+			<Item Name="[context]" Condition="ctx != nullptr">ctx->value</Item>
+		</Expand>
+	</Type>
+	<Type Name="entt::meta_prop">
+		<DisplayString Condition="node != nullptr">{ *node }</DisplayString>
+		<DisplayString>{{}}</DisplayString>
+		<Expand>
+			<ExpandedItem Condition="node != nullptr">node</ExpandedItem>
 			<Item Name="[context]" Condition="ctx != nullptr">ctx->value</Item>
 		</Expand>
 	</Type>
@@ -168,21 +118,4 @@
 			<Item Name="[context]" Condition="ctx != nullptr">ctx->value</Item>
 		</Expand>
 	</Type>
-	<Type Name="entt::meta_ctx">
-		<Intrinsic Name="element_at" Expression="value.packed.first_base::value[pos].element">
-			<Parameter Name="pos" Type="int"/>
-		</Intrinsic>
-		<DisplayString>{ value }</DisplayString>
-		<Expand>
-			<CustomListItems>
-				<Variable Name="pos" InitialValue="0"/>
-				<Variable Name="last" InitialValue="value.size()"/>
-				<Loop>
-					<Break Condition="pos == last"/>
-					<Item Name="[{ element_at(pos).first }]">element_at(pos).second</Item>
-					<Exec>++pos</Exec>
-				</Loop>
-			</CustomListItems>
-		</Expand>
-	</Type>
 </AutoVisualizer>

natvis/entt/platform.natvis

@@ -0,0 +1,3 @@
+<?xml version="1.0" encoding="utf-8"?>
+<AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
+</AutoVisualizer>

natvis/entt/resource.natvis

@@ -7,20 +7,9 @@
 		</Expand>
 	</Type>
 	<Type Name="entt::resource_cache&lt;*&gt;">
-		<Intrinsic Name="size" Expression="pool.first_base::value.size()"/>
-		<DisplayString>{{ size={ size() } }}</DisplayString>
+		<DisplayString>{ pool.first_base::value }</DisplayString>
 		<Expand>
-			<CustomListItems>
-				<Variable Name="pos" InitialValue="0" />
-				<Variable Name="last" InitialValue="size()"/>
-				<Loop>
-					<Break Condition="pos == last"/>
-					<Item Name="[{ pool.first_base::value.packed.first_base::value[pos].element.first }]">
-						*pool.first_base::value.packed.first_base::value[pos].element.second
-					</Item>
-					<Exec>++pos</Exec>
-				</Loop>
-			</CustomListItems>
+			<ExpandedItem>pool.first_base::value</ExpandedItem>
 		</Expand>
 	</Type>
 </AutoVisualizer>

natvis/entt/signal.natvis

@@ -11,10 +11,15 @@
 		<Intrinsic Name="size" Expression="pools.first_base::value.size()"/>
 		<DisplayString>{{ size={ size() } }}</DisplayString>
 		<Expand>
-			<IndexListItems>
-				<Size>size()</Size>
-				<ValueNode>*pools.first_base::value.packed.first_base::value[$i].element.second</ValueNode>
-			</IndexListItems>
+			<Synthetic Name="[pools]">
+				<DisplayString>{ size() }</DisplayString>
+				<Expand>
+					<IndexListItems>
+						<Size>size()</Size>
+						<ValueNode>*pools.first_base::value.packed.first_base::value[$i].element.second</ValueNode>
+					</IndexListItems>
+				</Expand>
+			</Synthetic>
 		</Expand>
 	</Type>
 	<Type Name="entt::internal::dispatcher_handler&lt;*&gt;">
@@ -24,7 +29,7 @@
 		</Expand>
 	</Type>
 	<Type Name="entt::emitter&lt;*&gt;">
-		<DisplayString>{{ size={ handlers.first_base::value.size() } }}</DisplayString>
+		<DisplayString>{{ size={ handlers.first_base::value.packed.first_base::value.size() } }}</DisplayString>
 	</Type>
 	<Type Name="entt::connection">
 		<DisplayString>{{ bound={ signal != nullptr } }}</DisplayString>

scripts/sync_bzlmod_version.sh

@@ -1,28 +0,0 @@
-#!/usr/bin/env bash
-
-set -e
-
-SCRIPT_DIR=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" &>/dev/null && pwd)
-VERSION_HEADER=$(realpath "$SCRIPT_DIR/../src/entt/config/version.h" --relative-to=$(pwd))
-BAZEL_MODULE=$(realpath "$SCRIPT_DIR/../MODULE.bazel" --relative-to=$(pwd))
-
-if [[ -z "${VERSION_HEADER}" ]]; then
-	echo "Cannot find version header"
-	exit 1
-fi
-
-echo "Getting version from $VERSION_HEADER ..."
-
-ENTT_MAJOR_VERSION=$(sed -nr 's/#define ENTT_VERSION_MAJOR ([0-9]+)/\1/p' $VERSION_HEADER)
-ENTT_MINOR_VERSION=$(sed -nr 's/#define ENTT_VERSION_MINOR ([0-9]+)/\1/p' $VERSION_HEADER)
-ENTT_PATCH_VERSION=$(sed -nr 's/#define ENTT_VERSION_PATCH ([0-9]+)/\1/p' $VERSION_HEADER)
-
-VERSION="$ENTT_MAJOR_VERSION.$ENTT_MINOR_VERSION.$ENTT_PATCH_VERSION"
-
-echo "Found $VERSION"
-
-buildozer "set version $VERSION" //MODULE.bazel:%module
-
-# a commit is needed for 'git archive'
-git add $BAZEL_MODULE
-git commit -m "chore: update MODULE.bazel version to $VERSION"

src/BUILD.bazel

@@ -1,11 +0,0 @@
-load("@bazel_skylib//lib:selects.bzl", "selects")
-load("//bazel:copts.bzl", "COPTS")
-
-package(default_visibility = ["//:__subpackages__"])
-
-cc_library(
-    name = "entt",
-    includes = ["."],
-    hdrs = glob(["**/*.h", "**/*.hpp"]),
-    copts = COPTS,
-)

src/entt/config/config.h

@@ -3,8 +3,6 @@
 
 #include "version.h"
 
-// NOLINTBEGIN(cppcoreguidelines-macro-usage)
-
 #if defined(__cpp_exceptions) && !defined(ENTT_NOEXCEPTION)
 #    define ENTT_CONSTEXPR
 #    define ENTT_THROW throw
@@ -17,18 +15,6 @@
 #    define ENTT_CATCH if(false)
 #endif
 
-#if __has_include(<version>)
-#    include <version>
-#
-#    if defined(__cpp_consteval)
-#        define ENTT_CONSTEVAL consteval
-#    endif
-#endif
-
-#ifndef ENTT_CONSTEVAL
-#    define ENTT_CONSTEVAL constexpr
-#endif
-
 #ifdef ENTT_USE_ATOMIC
 #    include <atomic>
 #    define ENTT_MAYBE_ATOMIC(Type) std::atomic<Type>
@@ -39,8 +25,6 @@
 #ifndef ENTT_ID_TYPE
 #    include <cstdint>
 #    define ENTT_ID_TYPE std::uint32_t
-#else
-#    include <cstdint> // provides coverage for types in the std namespace
 #endif
 
 #ifndef ENTT_SPARSE_PAGE
@@ -56,7 +40,7 @@
 #    define ENTT_ASSERT(condition, msg) (void(0))
 #elif !defined ENTT_ASSERT
 #    include <cassert>
-#    define ENTT_ASSERT(condition, msg) assert(((condition) && (msg)))
+#    define ENTT_ASSERT(condition, msg) assert(condition)
 #endif
 
 #ifdef ENTT_DISABLE_ASSERT
@@ -74,12 +58,6 @@
 #    define ENTT_ETO_TYPE(Type) Type
 #endif
 
-#ifdef ENTT_NO_MIXIN
-#    define ENTT_STORAGE(Mixin, ...) __VA_ARGS__
-#else
-#    define ENTT_STORAGE(Mixin, ...) Mixin<__VA_ARGS__>
-#endif
-
 #ifdef ENTT_STANDARD_CPP
 #    define ENTT_NONSTD false
 #else
@@ -102,6 +80,4 @@
 #    pragma detect_mismatch("entt.nonstd", ENTT_XSTR(ENTT_NONSTD))
 #endif
 
-// NOLINTEND(cppcoreguidelines-macro-usage)
-
 #endif

src/entt/config/macro.h

@@ -1,11 +1,7 @@
 #ifndef ENTT_CONFIG_MACRO_H
 #define ENTT_CONFIG_MACRO_H
 
-// NOLINTBEGIN(cppcoreguidelines-macro-usage)
-
 #define ENTT_STR(arg) #arg
 #define ENTT_XSTR(arg) ENTT_STR(arg)
 
-// NOLINTEND(cppcoreguidelines-macro-usage)
-
 #endif

src/entt/config/version.h

@@ -3,16 +3,12 @@
 
 #include "macro.h"
 
-// NOLINTBEGIN(cppcoreguidelines-macro-*,modernize-macro-*)
-
 #define ENTT_VERSION_MAJOR 3
-#define ENTT_VERSION_MINOR 15
-#define ENTT_VERSION_PATCH 0
+#define ENTT_VERSION_MINOR 12
+#define ENTT_VERSION_PATCH 2
 
 #define ENTT_VERSION \
     ENTT_XSTR(ENTT_VERSION_MAJOR) \
     "." ENTT_XSTR(ENTT_VERSION_MINOR) "." ENTT_XSTR(ENTT_VERSION_PATCH)
 
-// NOLINTEND(cppcoreguidelines-macro-*,modernize-macro-*)
-
 #endif

src/entt/container/dense_map.hpp

@@ -12,7 +12,6 @@
 #include <utility>
 #include <vector>
 #include "../config/config.h"
-#include "../core/bit.hpp"
 #include "../core/compressed_pair.hpp"
 #include "../core/iterator.hpp"
 #include "../core/memory.hpp"
@@ -21,7 +20,11 @@
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 template<typename Key, typename Type>
@@ -66,7 +69,6 @@ public:
     using reference = value_type;
     using difference_type = std::ptrdiff_t;
     using iterator_category = std::input_iterator_tag;
-    using iterator_concept = std::random_access_iterator_tag;
 
     constexpr dense_map_iterator() noexcept
         : it{} {}
@@ -83,7 +85,7 @@ public:
     }
 
     constexpr dense_map_iterator operator++(int) noexcept {
-        const dense_map_iterator orig = *this;
+        dense_map_iterator orig = *this;
         return ++(*this), orig;
     }
 
@@ -92,7 +94,7 @@ public:
     }
 
     constexpr dense_map_iterator operator--(int) noexcept {
-        const dense_map_iterator orig = *this;
+        dense_map_iterator orig = *this;
         return operator--(), orig;
     }
 
@@ -123,7 +125,7 @@ public:
     }
 
     [[nodiscard]] constexpr reference operator*() const noexcept {
-        return operator[](0);
+        return {it->element.first, it->element.second};
     }
 
     template<typename Lhs, typename Rhs>
@@ -188,7 +190,6 @@ public:
     using reference = value_type;
     using difference_type = std::ptrdiff_t;
     using iterator_category = std::input_iterator_tag;
-    using iterator_concept = std::forward_iterator_tag;
 
     constexpr dense_map_local_iterator() noexcept
         : it{},
@@ -204,11 +205,11 @@ public:
           offset{other.offset} {}
 
     constexpr dense_map_local_iterator &operator++() noexcept {
-        return (offset = it[static_cast<typename It::difference_type>(offset)].next), *this;
+        return offset = it[offset].next, *this;
     }
 
     constexpr dense_map_local_iterator operator++(int) noexcept {
-        const dense_map_local_iterator orig = *this;
+        dense_map_local_iterator orig = *this;
         return ++(*this), orig;
     }
 
@@ -217,8 +218,7 @@ public:
     }
 
     [[nodiscard]] constexpr reference operator*() const noexcept {
-        const auto idx = static_cast<typename It::difference_type>(offset);
-        return {it[idx].element.first, it[idx].element.second};
+        return {it[offset].element.first, it[offset].element.second};
     }
 
     [[nodiscard]] constexpr std::size_t index() const noexcept {
@@ -241,7 +241,11 @@ template<typename Lhs, typename Rhs>
 }
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /**
  * @brief Associative container for key-value pairs with unique keys.
@@ -269,7 +273,6 @@ class dense_map {
 
     template<typename Other>
     [[nodiscard]] std::size_t key_to_bucket(const Other &key) const noexcept {
-        // NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-array-to-pointer-decay)
         return fast_mod(static_cast<size_type>(sparse.second()(key)), bucket_count());
     }
 
@@ -277,7 +280,7 @@ class dense_map {
     [[nodiscard]] auto constrained_find(const Other &key, std::size_t bucket) {
         for(auto it = begin(bucket), last = end(bucket); it != last; ++it) {
             if(packed.second()(it->first, key)) {
-                return begin() + static_cast<difference_type>(it.index());
+                return begin() + static_cast<typename iterator::difference_type>(it.index());
             }
         }
 
@@ -288,7 +291,7 @@ class dense_map {
     [[nodiscard]] auto constrained_find(const Other &key, std::size_t bucket) const {
         for(auto it = cbegin(bucket), last = cend(bucket); it != last; ++it) {
             if(packed.second()(it->first, key)) {
-                return cbegin() + static_cast<difference_type>(it.index());
+                return cbegin() + static_cast<typename iterator::difference_type>(it.index());
             }
         }
 
@@ -328,7 +331,7 @@ class dense_map {
 
     void move_and_pop(const std::size_t pos) {
         if(const auto last = size() - 1u; pos != last) {
-            size_type *curr = &sparse.first()[key_to_bucket(packed.first().back().element.first)];
+            size_type *curr = sparse.first().data() + key_to_bucket(packed.first().back().element.first);
             packed.first()[pos] = std::move(packed.first().back());
             for(; *curr != last; curr = &packed.first()[*curr].next) {}
             *curr = pos;
@@ -338,14 +341,12 @@ class dense_map {
     }
 
     void rehash_if_required() {
-        if(const auto bc = bucket_count(); size() > static_cast<size_type>(static_cast<float>(bc) * max_load_factor())) {
-            rehash(bc * 2u);
+        if(size() > (bucket_count() * max_load_factor())) {
+            rehash(bucket_count() * 2u);
         }
     }
 
 public:
-    /*! @brief Allocator type. */
-    using allocator_type = Allocator;
     /*! @brief Key type of the container. */
     using key_type = Key;
     /*! @brief Mapped type of the container. */
@@ -354,12 +355,12 @@ public:
     using value_type = std::pair<const Key, Type>;
     /*! @brief Unsigned integer type. */
     using size_type = std::size_t;
-    /*! @brief Signed integer type. */
-    using difference_type = std::ptrdiff_t;
     /*! @brief Type of function to use to hash the keys. */
     using hasher = Hash;
     /*! @brief Type of function to use to compare the keys for equality. */
     using key_equal = KeyEqual;
+    /*! @brief Allocator type. */
+    using allocator_type = Allocator;
     /*! @brief Input iterator type. */
     using iterator = internal::dense_map_iterator<typename packed_container_type::iterator>;
     /*! @brief Constant input iterator type. */
@@ -409,7 +410,8 @@ public:
      */
     explicit dense_map(const size_type cnt, const hasher &hash = hasher{}, const key_equal &equal = key_equal{}, const allocator_type &allocator = allocator_type{})
         : sparse{allocator, hash},
-          packed{allocator, equal} {
+          packed{allocator, equal},
+          threshold{default_threshold} {
         rehash(cnt);
     }
 
@@ -427,7 +429,7 @@ public:
           threshold{other.threshold} {}
 
     /*! @brief Default move constructor. */
-    dense_map(dense_map &&) noexcept = default;
+    dense_map(dense_map &&) noexcept(std::is_nothrow_move_constructible_v<compressed_pair<sparse_container_type, hasher>> &&std::is_nothrow_move_constructible_v<compressed_pair<packed_container_type, key_equal>>) = default;
 
     /**
      * @brief Allocator-extended move constructor.
@@ -439,9 +441,6 @@ public:
           packed{std::piecewise_construct, std::forward_as_tuple(std::move(other.packed.first()), allocator), std::forward_as_tuple(std::move(other.packed.second()))},
           threshold{other.threshold} {}
 
-    /*! @brief Default destructor. */
-    ~dense_map() = default;
-
     /**
      * @brief Default copy assignment operator.
      * @return This container.
@@ -452,18 +451,7 @@ public:
      * @brief Default move assignment operator.
      * @return This container.
      */
-    dense_map &operator=(dense_map &&) noexcept = default;
-
-    /**
-     * @brief Exchanges the contents with those of a given container.
-     * @param other Container to exchange the content with.
-     */
-    void swap(dense_map &other) noexcept {
-        using std::swap;
-        swap(sparse, other.sparse);
-        swap(packed, other.packed);
-        swap(threshold, other.threshold);
-    }
+    dense_map &operator=(dense_map &&) noexcept(std::is_nothrow_move_assignable_v<compressed_pair<sparse_container_type, hasher>> &&std::is_nothrow_move_assignable_v<compressed_pair<packed_container_type, key_equal>>) = default;
 
     /**
      * @brief Returns the associated allocator.
@@ -683,7 +671,7 @@ public:
         const auto dist = first - cbegin();
 
         for(auto from = last - cbegin(); from != dist; --from) {
-            erase(packed.first()[static_cast<size_type>(from) - 1u].element.first);
+            erase(packed.first()[from - 1u].element.first);
         }
 
         return (begin() + dist);
@@ -695,7 +683,7 @@ public:
      * @return Number of elements removed (either 0 or 1).
      */
     size_type erase(const key_type &key) {
-        for(size_type *curr = &sparse.first()[key_to_bucket(key)]; *curr != (std::numeric_limits<size_type>::max)(); curr = &packed.first()[*curr].next) {
+        for(size_type *curr = sparse.first().data() + key_to_bucket(key); *curr != (std::numeric_limits<size_type>::max)(); curr = &packed.first()[*curr].next) {
             if(packed.second()(packed.first()[*curr].element.first, key)) {
                 const auto index = *curr;
                 *curr = packed.first()[*curr].next;
@@ -707,6 +695,17 @@ public:
         return 0u;
     }
 
+    /**
+     * @brief Exchanges the contents with those of a given container.
+     * @param other Container to exchange the content with.
+     */
+    void swap(dense_map &other) {
+        using std::swap;
+        swap(sparse, other.sparse);
+        swap(packed, other.packed);
+        swap(threshold, other.threshold);
+    }
+
     /**
      * @brief Accesses a given element with bounds checking.
      * @param key A key of an element to find.
@@ -955,7 +954,7 @@ public:
      * @return The average number of elements per bucket.
      */
     [[nodiscard]] float load_factor() const {
-        return static_cast<float>(size()) / static_cast<float>(bucket_count());
+        return size() / static_cast<float>(bucket_count());
     }
 
     /**
@@ -983,14 +982,14 @@ public:
      */
     void rehash(const size_type cnt) {
         auto value = cnt > minimum_capacity ? cnt : minimum_capacity;
-        const auto cap = static_cast<size_type>(static_cast<float>(size()) / max_load_factor());
+        const auto cap = static_cast<size_type>(size() / max_load_factor());
         value = value > cap ? value : cap;
 
         if(const auto sz = next_power_of_two(value); sz != bucket_count()) {
             sparse.first().resize(sz);
 
             for(auto &&elem: sparse.first()) {
-                elem = (std::numeric_limits<size_type>::max)();
+                elem = std::numeric_limits<size_type>::max();
             }
 
             for(size_type pos{}, last = size(); pos < last; ++pos) {
@@ -1007,7 +1006,7 @@ public:
      */
     void reserve(const size_type cnt) {
         packed.first().reserve(cnt);
-        rehash(static_cast<size_type>(std::ceil(static_cast<float>(cnt) / max_load_factor())));
+        rehash(static_cast<size_type>(std::ceil(cnt / max_load_factor())));
     }
 
     /**
@@ -1029,12 +1028,16 @@ public:
 private:
     compressed_pair<sparse_container_type, hasher> sparse;
     compressed_pair<packed_container_type, key_equal> packed;
-    float threshold{default_threshold};
+    float threshold;
 };
 
 } // namespace entt
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace std {
 
 template<typename Key, typename Value, typename Allocator>
@@ -1042,6 +1045,10 @@ struct uses_allocator<entt::internal::dense_map_node<Key, Value>, Allocator>
     : std::true_type {};
 
 } // namespace std
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 #endif

src/entt/container/dense_set.hpp

@@ -12,14 +12,18 @@
 #include <utility>
 #include <vector>
 #include "../config/config.h"
-#include "../core/bit.hpp"
 #include "../core/compressed_pair.hpp"
+#include "../core/memory.hpp"
 #include "../core/type_traits.hpp"
 #include "fwd.hpp"
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 template<typename It>
@@ -49,7 +53,7 @@ public:
     }
 
     constexpr dense_set_iterator operator++(int) noexcept {
-        const dense_set_iterator orig = *this;
+        dense_set_iterator orig = *this;
         return ++(*this), orig;
     }
 
@@ -58,7 +62,7 @@ public:
     }
 
     constexpr dense_set_iterator operator--(int) noexcept {
-        const dense_set_iterator orig = *this;
+        dense_set_iterator orig = *this;
         return operator--(), orig;
     }
 
@@ -85,11 +89,11 @@ public:
     }
 
     [[nodiscard]] constexpr pointer operator->() const noexcept {
-        return std::addressof(operator[](0));
+        return std::addressof(it->second);
     }
 
     [[nodiscard]] constexpr reference operator*() const noexcept {
-        return operator[](0);
+        return *operator->();
     }
 
     template<typename Lhs, typename Rhs>
@@ -166,16 +170,16 @@ public:
           offset{other.offset} {}
 
     constexpr dense_set_local_iterator &operator++() noexcept {
-        return offset = it[static_cast<typename It::difference_type>(offset)].first, *this;
+        return offset = it[offset].first, *this;
     }
 
     constexpr dense_set_local_iterator operator++(int) noexcept {
-        const dense_set_local_iterator orig = *this;
+        dense_set_local_iterator orig = *this;
         return ++(*this), orig;
     }
 
     [[nodiscard]] constexpr pointer operator->() const noexcept {
-        return std::addressof(it[static_cast<typename It::difference_type>(offset)].second);
+        return std::addressof(it[offset].second);
     }
 
     [[nodiscard]] constexpr reference operator*() const noexcept {
@@ -202,7 +206,11 @@ template<typename Lhs, typename Rhs>
 }
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /**
  * @brief Associative container for unique objects of a given type.
@@ -236,7 +244,7 @@ class dense_set {
     [[nodiscard]] auto constrained_find(const Other &value, std::size_t bucket) {
         for(auto it = begin(bucket), last = end(bucket); it != last; ++it) {
             if(packed.second()(*it, value)) {
-                return begin() + static_cast<difference_type>(it.index());
+                return begin() + static_cast<typename iterator::difference_type>(it.index());
             }
         }
 
@@ -247,7 +255,7 @@ class dense_set {
     [[nodiscard]] auto constrained_find(const Other &value, std::size_t bucket) const {
         for(auto it = cbegin(bucket), last = cend(bucket); it != last; ++it) {
             if(packed.second()(*it, value)) {
-                return cbegin() + static_cast<difference_type>(it.index());
+                return cbegin() + static_cast<typename iterator::difference_type>(it.index());
             }
         }
 
@@ -271,7 +279,7 @@ class dense_set {
 
     void move_and_pop(const std::size_t pos) {
         if(const auto last = size() - 1u; pos != last) {
-            size_type *curr = &sparse.first()[value_to_bucket(packed.first().back().second)];
+            size_type *curr = sparse.first().data() + value_to_bucket(packed.first().back().second);
             packed.first()[pos] = std::move(packed.first().back());
             for(; *curr != last; curr = &packed.first()[*curr].first) {}
             *curr = pos;
@@ -281,34 +289,28 @@ class dense_set {
     }
 
     void rehash_if_required() {
-        if(const auto bc = bucket_count(); size() > static_cast<size_type>(static_cast<float>(bc) * max_load_factor())) {
-            rehash(bc * 2u);
+        if(size() > (bucket_count() * max_load_factor())) {
+            rehash(bucket_count() * 2u);
         }
     }
 
 public:
-    /*! @brief Allocator type. */
-    using allocator_type = Allocator;
     /*! @brief Key type of the container. */
     using key_type = Type;
     /*! @brief Value type of the container. */
     using value_type = Type;
     /*! @brief Unsigned integer type. */
     using size_type = std::size_t;
-    /*! @brief Signed integer type. */
-    using difference_type = std::ptrdiff_t;
     /*! @brief Type of function to use to hash the elements. */
     using hasher = Hash;
     /*! @brief Type of function to use to compare the elements for equality. */
     using key_equal = KeyEqual;
+    /*! @brief Allocator type. */
+    using allocator_type = Allocator;
     /*! @brief Random access iterator type. */
     using iterator = internal::dense_set_iterator<typename packed_container_type::iterator>;
     /*! @brief Constant random access iterator type. */
     using const_iterator = internal::dense_set_iterator<typename packed_container_type::const_iterator>;
-    /*! @brief Reverse iterator type. */
-    using reverse_iterator = std::reverse_iterator<iterator>;
-    /*! @brief Constant reverse iterator type. */
-    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
     /*! @brief Forward iterator type. */
     using local_iterator = internal::dense_set_local_iterator<typename packed_container_type::iterator>;
     /*! @brief Constant forward iterator type. */
@@ -354,7 +356,8 @@ public:
      */
     explicit dense_set(const size_type cnt, const hasher &hash = hasher{}, const key_equal &equal = key_equal{}, const allocator_type &allocator = allocator_type{})
         : sparse{allocator, hash},
-          packed{allocator, equal} {
+          packed{allocator, equal},
+          threshold{default_threshold} {
         rehash(cnt);
     }
 
@@ -372,7 +375,7 @@ public:
           threshold{other.threshold} {}
 
     /*! @brief Default move constructor. */
-    dense_set(dense_set &&) noexcept = default;
+    dense_set(dense_set &&) noexcept(std::is_nothrow_move_constructible_v<compressed_pair<sparse_container_type, hasher>> &&std::is_nothrow_move_constructible_v<compressed_pair<packed_container_type, key_equal>>) = default;
 
     /**
      * @brief Allocator-extended move constructor.
@@ -384,9 +387,6 @@ public:
           packed{std::piecewise_construct, std::forward_as_tuple(std::move(other.packed.first()), allocator), std::forward_as_tuple(std::move(other.packed.second()))},
           threshold{other.threshold} {}
 
-    /*! @brief Default destructor. */
-    ~dense_set() = default;
-
     /**
      * @brief Default copy assignment operator.
      * @return This container.
@@ -397,18 +397,7 @@ public:
      * @brief Default move assignment operator.
      * @return This container.
      */
-    dense_set &operator=(dense_set &&) noexcept = default;
-
-    /**
-     * @brief Exchanges the contents with those of a given container.
-     * @param other Container to exchange the content with.
-     */
-    void swap(dense_set &other) noexcept {
-        using std::swap;
-        swap(sparse, other.sparse);
-        swap(packed, other.packed);
-        swap(threshold, other.threshold);
-    }
+    dense_set &operator=(dense_set &&) noexcept(std::is_nothrow_move_assignable_v<compressed_pair<sparse_container_type, hasher>> &&std::is_nothrow_move_assignable_v<compressed_pair<packed_container_type, key_equal>>) = default;
 
     /**
      * @brief Returns the associated allocator.
@@ -458,46 +447,6 @@ public:
         return packed.first().end();
     }
 
-    /**
-     * @brief Returns a reverse iterator to the beginning.
-     *
-     * If the array is empty, the returned iterator will be equal to `rend()`.
-     *
-     * @return An iterator to the first instance of the reversed internal array.
-     */
-    [[nodiscard]] const_reverse_iterator crbegin() const noexcept {
-        return std::make_reverse_iterator(cend());
-    }
-
-    /*! @copydoc crbegin */
-    [[nodiscard]] const_reverse_iterator rbegin() const noexcept {
-        return crbegin();
-    }
-
-    /*! @copydoc rbegin */
-    [[nodiscard]] reverse_iterator rbegin() noexcept {
-        return std::make_reverse_iterator(end());
-    }
-
-    /**
-     * @brief Returns a reverse iterator to the end.
-     * @return An iterator to the element following the last instance of the
-     * reversed internal array.
-     */
-    [[nodiscard]] const_reverse_iterator crend() const noexcept {
-        return std::make_reverse_iterator(cbegin());
-    }
-
-    /*! @copydoc crend */
-    [[nodiscard]] const_reverse_iterator rend() const noexcept {
-        return crend();
-    }
-
-    /*! @copydoc rend */
-    [[nodiscard]] reverse_iterator rend() noexcept {
-        return std::make_reverse_iterator(begin());
-    }
-
     /**
      * @brief Checks whether a container is empty.
      * @return True if the container is empty, false otherwise.
@@ -612,7 +561,7 @@ public:
         const auto dist = first - cbegin();
 
         for(auto from = last - cbegin(); from != dist; --from) {
-            erase(packed.first()[static_cast<size_type>(from) - 1u].second);
+            erase(packed.first()[from - 1u].second);
         }
 
         return (begin() + dist);
@@ -624,7 +573,7 @@ public:
      * @return Number of elements removed (either 0 or 1).
      */
     size_type erase(const value_type &value) {
-        for(size_type *curr = &sparse.first()[value_to_bucket(value)]; *curr != (std::numeric_limits<size_type>::max)(); curr = &packed.first()[*curr].first) {
+        for(size_type *curr = sparse.first().data() + value_to_bucket(value); *curr != (std::numeric_limits<size_type>::max)(); curr = &packed.first()[*curr].first) {
             if(packed.second()(packed.first()[*curr].second, value)) {
                 const auto index = *curr;
                 *curr = packed.first()[*curr].first;
@@ -636,6 +585,17 @@ public:
         return 0u;
     }
 
+    /**
+     * @brief Exchanges the contents with those of a given container.
+     * @param other Container to exchange the content with.
+     */
+    void swap(dense_set &other) {
+        using std::swap;
+        swap(sparse, other.sparse);
+        swap(packed, other.packed);
+        swap(threshold, other.threshold);
+    }
+
     /**
      * @brief Returns the number of elements matching a value (either 1 or 0).
      * @param key Key value of an element to search for.
@@ -847,7 +807,7 @@ public:
      * @return The average number of elements per bucket.
      */
     [[nodiscard]] float load_factor() const {
-        return static_cast<float>(size()) / static_cast<float>(bucket_count());
+        return size() / static_cast<float>(bucket_count());
     }
 
     /**
@@ -875,14 +835,14 @@ public:
      */
     void rehash(const size_type cnt) {
         auto value = cnt > minimum_capacity ? cnt : minimum_capacity;
-        const auto cap = static_cast<size_type>(static_cast<float>(size()) / max_load_factor());
+        const auto cap = static_cast<size_type>(size() / max_load_factor());
         value = value > cap ? value : cap;
 
         if(const auto sz = next_power_of_two(value); sz != bucket_count()) {
             sparse.first().resize(sz);
 
             for(auto &&elem: sparse.first()) {
-                elem = (std::numeric_limits<size_type>::max)();
+                elem = std::numeric_limits<size_type>::max();
             }
 
             for(size_type pos{}, last = size(); pos < last; ++pos) {
@@ -899,7 +859,7 @@ public:
      */
     void reserve(const size_type cnt) {
         packed.first().reserve(cnt);
-        rehash(static_cast<size_type>(std::ceil(static_cast<float>(cnt) / max_load_factor())));
+        rehash(static_cast<size_type>(std::ceil(cnt / max_load_factor())));
     }
 
     /**
@@ -921,7 +881,7 @@ public:
 private:
     compressed_pair<sparse_container_type, hasher> sparse;
     compressed_pair<packed_container_type, key_equal> packed;
-    float threshold{default_threshold};
+    float threshold;
 };
 
 } // namespace entt

src/entt/container/fwd.hpp

@@ -3,8 +3,6 @@
 
 #include <functional>
 #include <memory>
-#include <utility>
-#include <vector>
 
 namespace entt {
 
@@ -12,27 +10,17 @@ template<
     typename Key,
     typename Type,
     typename = std::hash<Key>,
-    typename = std::equal_to<>,
+    typename = std::equal_to<Key>,
     typename = std::allocator<std::pair<const Key, Type>>>
 class dense_map;
 
 template<
     typename Type,
     typename = std::hash<Type>,
-    typename = std::equal_to<>,
+    typename = std::equal_to<Type>,
     typename = std::allocator<Type>>
 class dense_set;
 
-template<typename...>
-class basic_table;
-
-/**
- * @brief Alias declaration for the most common use case.
- * @tparam Type Element types.
- */
-template<typename... Type>
-using table = basic_table<std::vector<Type>...>;
-
 } // namespace entt
 
 #endif

src/entt/container/table.hpp

@@ -1,462 +0,0 @@
-#ifndef ENTT_CONTAINER_TABLE_HPP
-#define ENTT_CONTAINER_TABLE_HPP
-
-#include <cstddef>
-#include <iterator>
-#include <tuple>
-#include <type_traits>
-#include <utility>
-#include "../config/config.h"
-#include "../core/iterator.hpp"
-#include "fwd.hpp"
-
-namespace entt {
-
-/*! @cond TURN_OFF_DOXYGEN */
-namespace internal {
-
-template<typename... It>
-class table_iterator {
-    template<typename...>
-    friend class table_iterator;
-
-public:
-    using value_type = decltype(std::forward_as_tuple(*std::declval<It>()...));
-    using pointer = input_iterator_pointer<value_type>;
-    using reference = value_type;
-    using difference_type = std::ptrdiff_t;
-    using iterator_category = std::input_iterator_tag;
-    using iterator_concept = std::random_access_iterator_tag;
-
-    constexpr table_iterator() noexcept
-        : it{} {}
-
-    constexpr table_iterator(It... from) noexcept
-        : it{from...} {}
-
-    template<typename... Other, typename = std::enable_if_t<(std::is_constructible_v<It, Other> && ...)>>
-    constexpr table_iterator(const table_iterator<Other...> &other) noexcept
-        : table_iterator{std::get<Other>(other.it)...} {}
-
-    constexpr table_iterator &operator++() noexcept {
-        return (++std::get<It>(it), ...), *this;
-    }
-
-    constexpr table_iterator operator++(int) noexcept {
-        const table_iterator orig = *this;
-        return ++(*this), orig;
-    }
-
-    constexpr table_iterator &operator--() noexcept {
-        return (--std::get<It>(it), ...), *this;
-    }
-
-    constexpr table_iterator operator--(int) noexcept {
-        const table_iterator orig = *this;
-        return operator--(), orig;
-    }
-
-    constexpr table_iterator &operator+=(const difference_type value) noexcept {
-        return ((std::get<It>(it) += value), ...), *this;
-    }
-
-    constexpr table_iterator operator+(const difference_type value) const noexcept {
-        table_iterator copy = *this;
-        return (copy += value);
-    }
-
-    constexpr table_iterator &operator-=(const difference_type value) noexcept {
-        return (*this += -value);
-    }
-
-    constexpr table_iterator operator-(const difference_type value) const noexcept {
-        return (*this + -value);
-    }
-
-    [[nodiscard]] constexpr reference operator[](const difference_type value) const noexcept {
-        return std::forward_as_tuple(std::get<It>(it)[value]...);
-    }
-
-    [[nodiscard]] constexpr pointer operator->() const noexcept {
-        return {operator[](0)};
-    }
-
-    [[nodiscard]] constexpr reference operator*() const noexcept {
-        return operator[](0);
-    }
-
-    template<typename... Lhs, typename... Rhs>
-    friend constexpr std::ptrdiff_t operator-(const table_iterator<Lhs...> &, const table_iterator<Rhs...> &) noexcept;
-
-    template<typename... Lhs, typename... Rhs>
-    friend constexpr bool operator==(const table_iterator<Lhs...> &, const table_iterator<Rhs...> &) noexcept;
-
-    template<typename... Lhs, typename... Rhs>
-    friend constexpr bool operator<(const table_iterator<Lhs...> &, const table_iterator<Rhs...> &) noexcept;
-
-private:
-    std::tuple<It...> it;
-};
-
-template<typename... Lhs, typename... Rhs>
-[[nodiscard]] constexpr std::ptrdiff_t operator-(const table_iterator<Lhs...> &lhs, const table_iterator<Rhs...> &rhs) noexcept {
-    return std::get<0>(lhs.it) - std::get<0>(rhs.it);
-}
-
-template<typename... Lhs, typename... Rhs>
-[[nodiscard]] constexpr bool operator==(const table_iterator<Lhs...> &lhs, const table_iterator<Rhs...> &rhs) noexcept {
-    return std::get<0>(lhs.it) == std::get<0>(rhs.it);
-}
-
-template<typename... Lhs, typename... Rhs>
-[[nodiscard]] constexpr bool operator!=(const table_iterator<Lhs...> &lhs, const table_iterator<Rhs...> &rhs) noexcept {
-    return !(lhs == rhs);
-}
-
-template<typename... Lhs, typename... Rhs>
-[[nodiscard]] constexpr bool operator<(const table_iterator<Lhs...> &lhs, const table_iterator<Rhs...> &rhs) noexcept {
-    return std::get<0>(lhs.it) < std::get<0>(rhs.it);
-}
-
-template<typename... Lhs, typename... Rhs>
-[[nodiscard]] constexpr bool operator>(const table_iterator<Lhs...> &lhs, const table_iterator<Rhs...> &rhs) noexcept {
-    return rhs < lhs;
-}
-
-template<typename... Lhs, typename... Rhs>
-[[nodiscard]] constexpr bool operator<=(const table_iterator<Lhs...> &lhs, const table_iterator<Rhs...> &rhs) noexcept {
-    return !(lhs > rhs);
-}
-
-template<typename... Lhs, typename... Rhs>
-[[nodiscard]] constexpr bool operator>=(const table_iterator<Lhs...> &lhs, const table_iterator<Rhs...> &rhs) noexcept {
-    return !(lhs < rhs);
-}
-
-} // namespace internal
-/*! @endcond */
-
-/**
- * @brief Basic table implementation.
- *
- * Internal data structures arrange elements to maximize performance. There are
- * no guarantees that objects are returned in the insertion order when iterate
- * a table. Do not make assumption on the order in any case.
- *
- * @tparam Container Sequence container row types.
- */
-template<typename... Container>
-class basic_table {
-    using container_type = std::tuple<Container...>;
-
-public:
-    /*! @brief Unsigned integer type. */
-    using size_type = std::size_t;
-    /*! @brief Signed integer type. */
-    using difference_type = std::ptrdiff_t;
-    /*! @brief Input iterator type. */
-    using iterator = internal::table_iterator<typename Container::iterator...>;
-    /*! @brief Constant input iterator type. */
-    using const_iterator = internal::table_iterator<typename Container::const_iterator...>;
-    /*! @brief Reverse iterator type. */
-    using reverse_iterator = internal::table_iterator<typename Container::reverse_iterator...>;
-    /*! @brief Constant reverse iterator type. */
-    using const_reverse_iterator = internal::table_iterator<typename Container::const_reverse_iterator...>;
-
-    /*! @brief Default constructor. */
-    basic_table()
-        : payload{} {
-    }
-
-    /**
-     * @brief Copy constructs the underlying containers.
-     * @param container The containers to copy from.
-     */
-    explicit basic_table(const Container &...container) noexcept
-        : payload{container...} {
-        ENTT_ASSERT((((std::get<Container>(payload).size() * sizeof...(Container)) == (std::get<Container>(payload).size() + ...)) && ...), "Unexpected container size");
-    }
-
-    /**
-     * @brief Move constructs the underlying containers.
-     * @param container The containers to move from.
-     */
-    explicit basic_table(Container &&...container) noexcept
-        : payload{std::move(container)...} {
-        ENTT_ASSERT((((std::get<Container>(payload).size() * sizeof...(Container)) == (std::get<Container>(payload).size() + ...)) && ...), "Unexpected container size");
-    }
-
-    /*! @brief Default copy constructor, deleted on purpose. */
-    basic_table(const basic_table &) = delete;
-
-    /**
-     * @brief Move constructor.
-     * @param other The instance to move from.
-     */
-    basic_table(basic_table &&other) noexcept
-        : payload{std::move(other.payload)} {}
-
-    /**
-     * @brief Constructs the underlying containers using a given allocator.
-     * @tparam Allocator Type of allocator.
-     * @param allocator A valid allocator.
-     */
-    template<typename Allocator>
-    explicit basic_table(const Allocator &allocator)
-        : payload{Container{allocator}...} {}
-
-    /**
-     * @brief Copy constructs the underlying containers using a given allocator.
-     * @tparam Allocator Type of allocator.
-     * @param container The containers to copy from.
-     * @param allocator A valid allocator.
-     */
-    template<class Allocator>
-    basic_table(const Container &...container, const Allocator &allocator) noexcept
-        : payload{Container{container, allocator}...} {
-        ENTT_ASSERT((((std::get<Container>(payload).size() * sizeof...(Container)) == (std::get<Container>(payload).size() + ...)) && ...), "Unexpected container size");
-    }
-
-    /**
-     * @brief Move constructs the underlying containers using a given allocator.
-     * @tparam Allocator Type of allocator.
-     * @param container The containers to move from.
-     * @param allocator A valid allocator.
-     */
-    template<class Allocator>
-    basic_table(Container &&...container, const Allocator &allocator) noexcept
-        : payload{Container{std::move(container), allocator}...} {
-        ENTT_ASSERT((((std::get<Container>(payload).size() * sizeof...(Container)) == (std::get<Container>(payload).size() + ...)) && ...), "Unexpected container size");
-    }
-
-    /**
-     * @brief Allocator-extended move constructor.
-     * @tparam Allocator Type of allocator.
-     * @param other The instance to move from.
-     * @param allocator The allocator to use.
-     */
-    template<class Allocator>
-    basic_table(basic_table &&other, const Allocator &allocator)
-        : payload{Container{std::move(std::get<Container>(other.payload)), allocator}...} {}
-
-    /*! @brief Default destructor. */
-    ~basic_table() = default;
-
-    /**
-     * @brief Default copy assignment operator, deleted on purpose.
-     * @return This container.
-     */
-    basic_table &operator=(const basic_table &) = delete;
-
-    /**
-     * @brief Move assignment operator.
-     * @param other The instance to move from.
-     * @return This container.
-     */
-    basic_table &operator=(basic_table &&other) noexcept {
-        swap(other);
-        return *this;
-    }
-
-    /**
-     * @brief Exchanges the contents with those of a given table.
-     * @param other Table to exchange the content with.
-     */
-    void swap(basic_table &other) noexcept {
-        using std::swap;
-        swap(payload, other.payload);
-    }
-
-    /**
-     * @brief Increases the capacity of a table.
-     *
-     * If the new capacity is greater than the current capacity, new storage is
-     * allocated, otherwise the method does nothing.
-     *
-     * @param cap Desired capacity.
-     */
-    void reserve(const size_type cap) {
-        (std::get<Container>(payload).reserve(cap), ...);
-    }
-
-    /**
-     * @brief Returns the number of rows that a table has currently allocated
-     * space for.
-     * @return Capacity of the table.
-     */
-    [[nodiscard]] size_type capacity() const noexcept {
-        return std::get<0>(payload).capacity();
-    }
-
-    /*! @brief Requests the removal of unused capacity. */
-    void shrink_to_fit() {
-        (std::get<Container>(payload).shrink_to_fit(), ...);
-    }
-
-    /**
-     * @brief Returns the number of rows in a table.
-     * @return Number of rows.
-     */
-    [[nodiscard]] size_type size() const noexcept {
-        return std::get<0>(payload).size();
-    }
-
-    /**
-     * @brief Checks whether a table is empty.
-     * @return True if the table is empty, false otherwise.
-     */
-    [[nodiscard]] bool empty() const noexcept {
-        return std::get<0>(payload).empty();
-    }
-
-    /**
-     * @brief Returns an iterator to the beginning.
-     *
-     * If the table is empty, the returned iterator will be equal to `end()`.
-     *
-     * @return An iterator to the first row of the table.
-     */
-    [[nodiscard]] const_iterator cbegin() const noexcept {
-        return {std::get<Container>(payload).cbegin()...};
-    }
-
-    /*! @copydoc cbegin */
-    [[nodiscard]] const_iterator begin() const noexcept {
-        return cbegin();
-    }
-
-    /*! @copydoc begin */
-    [[nodiscard]] iterator begin() noexcept {
-        return {std::get<Container>(payload).begin()...};
-    }
-
-    /**
-     * @brief Returns an iterator to the end.
-     * @return An iterator to the element following the last row of the table.
-     */
-    [[nodiscard]] const_iterator cend() const noexcept {
-        return {std::get<Container>(payload).cend()...};
-    }
-
-    /*! @copydoc cend */
-    [[nodiscard]] const_iterator end() const noexcept {
-        return cend();
-    }
-
-    /*! @copydoc end */
-    [[nodiscard]] iterator end() noexcept {
-        return {std::get<Container>(payload).end()...};
-    }
-
-    /**
-     * @brief Returns a reverse iterator to the beginning.
-     *
-     * If the table is empty, the returned iterator will be equal to `rend()`.
-     *
-     * @return An iterator to the first row of the reversed table.
-     */
-    [[nodiscard]] const_reverse_iterator crbegin() const noexcept {
-        return {std::get<Container>(payload).crbegin()...};
-    }
-
-    /*! @copydoc crbegin */
-    [[nodiscard]] const_reverse_iterator rbegin() const noexcept {
-        return crbegin();
-    }
-
-    /*! @copydoc rbegin */
-    [[nodiscard]] reverse_iterator rbegin() noexcept {
-        return {std::get<Container>(payload).rbegin()...};
-    }
-
-    /**
-     * @brief Returns a reverse iterator to the end.
-     * @return An iterator to the element following the last row of the reversed
-     * table.
-     */
-    [[nodiscard]] const_reverse_iterator crend() const noexcept {
-        return {std::get<Container>(payload).crend()...};
-    }
-
-    /*! @copydoc crend */
-    [[nodiscard]] const_reverse_iterator rend() const noexcept {
-        return crend();
-    }
-
-    /*! @copydoc rend */
-    [[nodiscard]] reverse_iterator rend() noexcept {
-        return {std::get<Container>(payload).rend()...};
-    }
-
-    /**
-     * @brief Appends a row to the end of a table.
-     * @tparam Args Types of arguments to use to construct the row data.
-     * @param args Parameters to use to construct the row data.
-     * @return A reference to the newly created row data.
-     */
-    template<typename... Args>
-    std::tuple<typename Container::value_type &...> emplace(Args &&...args) {
-        if constexpr(sizeof...(Args) == 0u) {
-            return std::forward_as_tuple(std::get<Container>(payload).emplace_back()...);
-        } else {
-            return std::forward_as_tuple(std::get<Container>(payload).emplace_back(std::forward<Args>(args))...);
-        }
-    }
-
-    /**
-     * @brief Removes a row from a table.
-     * @param pos An iterator to the row to remove.
-     * @return An iterator following the removed row.
-     */
-    iterator erase(const_iterator pos) {
-        const auto diff = pos - begin();
-        return {std::get<Container>(payload).erase(std::get<Container>(payload).begin() + diff)...};
-    }
-
-    /**
-     * @brief Removes a row from a table.
-     * @param pos Index of the row to remove.
-     */
-    void erase(const size_type pos) {
-        ENTT_ASSERT(pos < size(), "Index out of bounds");
-        erase(begin() + static_cast<difference_type>(pos));
-    }
-
-    /**
-     * @brief Returns the row data at specified location.
-     * @param pos The row for which to return the data.
-     * @return The row data at specified location.
-     */
-    [[nodiscard]] std::tuple<const typename Container::value_type &...> operator[](const size_type pos) const {
-        ENTT_ASSERT(pos < size(), "Index out of bounds");
-        return std::forward_as_tuple(std::get<Container>(payload)[pos]...);
-    }
-
-    /*! @copydoc operator[] */
-    [[nodiscard]] std::tuple<typename Container::value_type &...> operator[](const size_type pos) {
-        ENTT_ASSERT(pos < size(), "Index out of bounds");
-        return std::forward_as_tuple(std::get<Container>(payload)[pos]...);
-    }
-
-    /*! @brief Clears a table. */
-    void clear() {
-        (std::get<Container>(payload).clear(), ...);
-    }
-
-private:
-    container_type payload;
-};
-
-} // namespace entt
-
-/*! @cond TURN_OFF_DOXYGEN */
-namespace std {
-
-template<typename... Container, typename Allocator>
-struct uses_allocator<entt::basic_table<Container...>, Allocator>
-    : std::bool_constant<(std::uses_allocator_v<Container, Allocator> && ...)> {};
-
-} // namespace std
-/*! @endcond */
-
-#endif

src/entt/core/algorithm.hpp

@@ -58,11 +58,9 @@ struct insertion_sort {
                 auto value = std::move(*it);
                 auto pre = it;
 
-                // NOLINTBEGIN(cppcoreguidelines-pro-bounds-pointer-arithmetic)
                 for(; pre > first && compare(value, *(pre - 1)); --pre) {
                     *pre = std::move(*(pre - 1));
                 }
-                // NOLINTEND(cppcoreguidelines-pro-bounds-pointer-arithmetic)
 
                 *pre = std::move(value);
             }
@@ -100,34 +98,29 @@ struct radix_sort {
             constexpr auto passes = N / Bit;
 
             using value_type = typename std::iterator_traits<It>::value_type;
-            using difference_type = typename std::iterator_traits<It>::difference_type;
-            std::vector<value_type> aux(static_cast<std::size_t>(std::distance(first, last)));
+            std::vector<value_type> aux(std::distance(first, last));
 
             auto part = [getter = std::move(getter)](auto from, auto to, auto out, auto start) {
                 constexpr auto mask = (1 << Bit) - 1;
                 constexpr auto buckets = 1 << Bit;
 
-                // NOLINTNEXTLINE(cppcoreguidelines-avoid-c-arrays, modernize-avoid-c-arrays, misc-const-correctness)
+                std::size_t index[buckets]{};
                 std::size_t count[buckets]{};
 
                 for(auto it = from; it != to; ++it) {
                     ++count[(getter(*it) >> start) & mask];
                 }
 
-                // NOLINTNEXTLINE(cppcoreguidelines-avoid-c-arrays, modernize-avoid-c-arrays)
-                std::size_t index[buckets]{};
-
                 for(std::size_t pos{}, end = buckets - 1u; pos < end; ++pos) {
                     index[pos + 1u] = index[pos] + count[pos];
                 }
 
                 for(auto it = from; it != to; ++it) {
-                    const auto pos = index[(getter(*it) >> start) & mask]++;
-                    out[static_cast<difference_type>(pos)] = std::move(*it);
+                    out[index[(getter(*it) >> start) & mask]++] = std::move(*it);
                 }
             };
 
-            for(std::size_t pass = 0; pass < (passes & ~1u); pass += 2) {
+            for(std::size_t pass = 0; pass < (passes & ~1); pass += 2) {
                 part(first, last, aux.begin(), pass * Bit);
                 part(aux.begin(), aux.end(), first, (pass + 1) * Bit);
             }

src/entt/core/any.hpp

@@ -13,21 +13,35 @@
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
-enum class any_request : std::uint8_t {
+enum class any_operation : std::uint8_t {
+    copy,
+    move,
     transfer,
     assign,
     destroy,
     compare,
-    copy,
-    move,
     get
 };
 
+enum class any_policy : std::uint8_t {
+    owner,
+    ref,
+    cref
+};
+
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /**
  * @brief A SBO friendly, type-safe container for single values of any type.
@@ -36,77 +50,71 @@ enum class any_request : std::uint8_t {
  */
 template<std::size_t Len, std::size_t Align>
 class basic_any {
-    using request = internal::any_request;
-    using vtable_type = const void *(const request, const basic_any &, const void *);
+    using operation = internal::any_operation;
+    using policy = internal::any_policy;
+    using vtable_type = const void *(const operation, const basic_any &, const void *);
 
     struct storage_type {
-        // NOLINTNEXTLINE(cppcoreguidelines-avoid-c-arrays, modernize-avoid-c-arrays)
-        alignas(Align) std::byte data[Len + static_cast<std::size_t>(Len == 0u)];
+        alignas(Align) std::byte data[Len + !Len];
     };
 
     template<typename Type>
-    // NOLINTNEXTLINE(bugprone-sizeof-expression)
-    static constexpr bool in_situ = (Len != 0u) && alignof(Type) <= Align && sizeof(Type) <= Len && std::is_nothrow_move_constructible_v<Type>;
+    static constexpr bool in_situ = Len && alignof(Type) <= Align && sizeof(Type) <= Len && std::is_nothrow_move_constructible_v<Type>;
 
     template<typename Type>
-    static const void *basic_vtable(const request req, const basic_any &value, const void *other) {
-        static_assert(!std::is_void_v<Type> && std::is_same_v<std::remove_cv_t<std::remove_reference_t<Type>>, Type>, "Invalid type");
-        const Type *elem = nullptr;
+    static const void *basic_vtable(const operation op, const basic_any &value, const void *other) {
+        static_assert(!std::is_same_v<Type, void> && std::is_same_v<std::remove_cv_t<std::remove_reference_t<Type>>, Type>, "Invalid type");
+        const Type *element = nullptr;
 
         if constexpr(in_situ<Type>) {
-            elem = (value.mode == any_policy::embedded) ? reinterpret_cast<const Type *>(&value.storage) : static_cast<const Type *>(value.instance);
+            element = value.owner() ? reinterpret_cast<const Type *>(&value.storage) : static_cast<const Type *>(value.instance);
         } else {
-            elem = static_cast<const Type *>(value.instance);
+            element = static_cast<const Type *>(value.instance);
         }
 
-        switch(req) {
-        case request::transfer:
-            if constexpr(std::is_move_assignable_v<Type>) {
-                // NOLINTNEXTLINE(bugprone-casting-through-void)
-                *const_cast<Type *>(elem) = std::move(*static_cast<Type *>(const_cast<void *>(other)));
-                return other;
-            }
-            [[fallthrough]];
-        case request::assign:
-            if constexpr(std::is_copy_assignable_v<Type>) {
-                *const_cast<Type *>(elem) = *static_cast<const Type *>(other);
-                return other;
-            }
-            break;
-        case request::destroy:
-            if constexpr(in_situ<Type>) {
-                (value.mode == any_policy::embedded) ? elem->~Type() : (delete elem);
-            } else if constexpr(std::is_array_v<Type>) {
-                delete[] elem;
-            } else {
-                delete elem;
-            }
-            break;
-        case request::compare:
-            if constexpr(!std::is_function_v<Type> && !std::is_array_v<Type> && is_equality_comparable_v<Type>) {
-                return (*elem == *static_cast<const Type *>(other)) ? other : nullptr;
-            } else {
-                return (elem == other) ? other : nullptr;
-            }
-        case request::copy:
+        switch(op) {
+        case operation::copy:
             if constexpr(std::is_copy_constructible_v<Type>) {
-                // NOLINTNEXTLINE(bugprone-casting-through-void)
-                static_cast<basic_any *>(const_cast<void *>(other))->initialize<Type>(*elem);
+                static_cast<basic_any *>(const_cast<void *>(other))->initialize<Type>(*element);
             }
             break;
-        case request::move:
-            ENTT_ASSERT(value.mode == any_policy::embedded, "Unexpected policy");
+        case operation::move:
             if constexpr(in_situ<Type>) {
-                // NOLINTNEXTLINE(bugprone-casting-through-void, bugprone-multi-level-implicit-pointer-conversion)
-                return ::new(&static_cast<basic_any *>(const_cast<void *>(other))->storage) Type{std::move(*const_cast<Type *>(elem))};
+                if(value.owner()) {
+                    return new(&static_cast<basic_any *>(const_cast<void *>(other))->storage) Type{std::move(*const_cast<Type *>(element))};
+                }
+            }
+
+            return (static_cast<basic_any *>(const_cast<void *>(other))->instance = std::exchange(const_cast<basic_any &>(value).instance, nullptr));
+        case operation::transfer:
+            if constexpr(std::is_move_assignable_v<Type>) {
+                *const_cast<Type *>(element) = std::move(*static_cast<Type *>(const_cast<void *>(other)));
+                return other;
             }
             [[fallthrough]];
-        case request::get:
-            ENTT_ASSERT(value.mode == any_policy::embedded, "Unexpected policy");
-            if constexpr(in_situ<Type>) {
-                // NOLINTNEXTLINE(bugprone-multi-level-implicit-pointer-conversion)
-                return elem;
+        case operation::assign:
+            if constexpr(std::is_copy_assignable_v<Type>) {
+                *const_cast<Type *>(element) = *static_cast<const Type *>(other);
+                return other;
             }
+            break;
+        case operation::destroy:
+            if constexpr(in_situ<Type>) {
+                element->~Type();
+            } else if constexpr(std::is_array_v<Type>) {
+                delete[] element;
+            } else {
+                delete element;
+            }
+            break;
+        case operation::compare:
+            if constexpr(!std::is_function_v<Type> && !std::is_array_v<Type> && is_equality_comparable_v<Type>) {
+                return *element == *static_cast<const Type *>(other) ? other : nullptr;
+            } else {
+                return (element == other) ? other : nullptr;
+            }
+        case operation::get:
+            return element;
         }
 
         return nullptr;
@@ -114,42 +122,32 @@ class basic_any {
 
     template<typename Type, typename... Args>
     void initialize([[maybe_unused]] Args &&...args) {
-        if constexpr(!std::is_void_v<Type>) {
-            using plain_type = std::remove_cv_t<std::remove_reference_t<Type>>;
+        info = &type_id<std::remove_cv_t<std::remove_reference_t<Type>>>();
 
-            info = &type_id<plain_type>();
-            vtable = basic_vtable<plain_type>;
+        if constexpr(!std::is_void_v<Type>) {
+            vtable = basic_vtable<std::remove_cv_t<std::remove_reference_t<Type>>>;
 
             if constexpr(std::is_lvalue_reference_v<Type>) {
                 static_assert((std::is_lvalue_reference_v<Args> && ...) && (sizeof...(Args) == 1u), "Invalid arguments");
-                mode = std::is_const_v<std::remove_reference_t<Type>> ? any_policy::cref : any_policy::ref;
-                // NOLINTNEXTLINE(bugprone-multi-level-implicit-pointer-conversion)
+                mode = std::is_const_v<std::remove_reference_t<Type>> ? policy::cref : policy::ref;
                 instance = (std::addressof(args), ...);
-            } else if constexpr(in_situ<plain_type>) {
-                mode = any_policy::embedded;
-
-                if constexpr(std::is_aggregate_v<plain_type> && (sizeof...(Args) != 0u || !std::is_default_constructible_v<plain_type>)) {
-                    ::new(&storage) plain_type{std::forward<Args>(args)...};
+            } else if constexpr(in_situ<std::remove_cv_t<std::remove_reference_t<Type>>>) {
+                if constexpr(std::is_aggregate_v<std::remove_cv_t<std::remove_reference_t<Type>>> && (sizeof...(Args) != 0u || !std::is_default_constructible_v<std::remove_cv_t<std::remove_reference_t<Type>>>)) {
+                    new(&storage) std::remove_cv_t<std::remove_reference_t<Type>>{std::forward<Args>(args)...};
                 } else {
-                    // NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-array-to-pointer-decay)
-                    ::new(&storage) plain_type(std::forward<Args>(args)...);
+                    new(&storage) std::remove_cv_t<std::remove_reference_t<Type>>(std::forward<Args>(args)...);
                 }
             } else {
-                mode = any_policy::dynamic;
-
-                if constexpr(std::is_aggregate_v<plain_type> && (sizeof...(Args) != 0u || !std::is_default_constructible_v<plain_type>)) {
-                    instance = new plain_type{std::forward<Args>(args)...};
-                } else if constexpr(std::is_array_v<plain_type>) {
-                    static_assert(sizeof...(Args) == 0u, "Invalid arguments");
-                    instance = new plain_type[std::extent_v<plain_type>]();
+                if constexpr(std::is_aggregate_v<std::remove_cv_t<std::remove_reference_t<Type>>> && (sizeof...(Args) != 0u || !std::is_default_constructible_v<std::remove_cv_t<std::remove_reference_t<Type>>>)) {
+                    instance = new std::remove_cv_t<std::remove_reference_t<Type>>{std::forward<Args>(args)...};
                 } else {
-                    instance = new plain_type(std::forward<Args>(args)...);
+                    instance = new std::remove_cv_t<std::remove_reference_t<Type>>(std::forward<Args>(args)...);
                 }
             }
         }
     }
 
-    basic_any(const basic_any &other, const any_policy pol) noexcept
+    basic_any(const basic_any &other, const policy pol) noexcept
         : instance{other.data()},
           info{other.info},
           vtable{other.vtable},
@@ -173,26 +171,13 @@ public:
      */
     template<typename Type, typename... Args>
     explicit basic_any(std::in_place_type_t<Type>, Args &&...args)
-        : instance{} {
+        : instance{},
+          info{},
+          vtable{},
+          mode{policy::owner} {
         initialize<Type>(std::forward<Args>(args)...);
     }
 
-    /**
-     * @brief Constructs a wrapper taking ownership of the passed object.
-     * @tparam Type Type of object to use to initialize the wrapper.
-     * @param value A pointer to an object to take ownership of.
-     */
-    template<typename Type>
-    explicit basic_any(std::in_place_t, Type *value)
-        : instance{} {
-        static_assert(!std::is_const_v<Type> && !std::is_void_v<Type>, "Non-const non-void pointer required");
-
-        if(value != nullptr) {
-            initialize<Type &>(*value);
-            mode = any_policy::dynamic;
-        }
-    }
-
     /**
      * @brief Constructs a wrapper from a given value.
      * @tparam Type Type of object to use to initialize the wrapper.
@@ -209,7 +194,7 @@ public:
     basic_any(const basic_any &other)
         : basic_any{} {
         if(other.vtable) {
-            other.vtable(request::copy, other, this);
+            other.vtable(operation::copy, other, this);
         }
     }
 
@@ -222,17 +207,15 @@ public:
           info{other.info},
           vtable{other.vtable},
           mode{other.mode} {
-        if(other.mode == any_policy::embedded) {
-            other.vtable(request::move, other, this);
-        } else if(other.mode != any_policy::empty) {
-            instance = std::exchange(other.instance, nullptr);
+        if(other.vtable) {
+            other.vtable(operation::move, other, this);
         }
     }
 
     /*! @brief Frees the internal storage, whatever it means. */
     ~basic_any() {
-        if(owner()) {
-            vtable(request::destroy, *this, nullptr);
+        if(vtable && owner()) {
+            vtable(operation::destroy, *this, nullptr);
         }
     }
 
@@ -242,12 +225,10 @@ public:
      * @return This any object.
      */
     basic_any &operator=(const basic_any &other) {
-        if(this != &other) {
-            reset();
+        reset();
 
-            if(other.vtable) {
-                other.vtable(request::copy, other, this);
-            }
+        if(other.vtable) {
+            other.vtable(operation::copy, other, this);
         }
 
         return *this;
@@ -255,26 +236,19 @@ public:
 
     /**
      * @brief Move assignment operator.
-     *
-     * @warning
-     * Self-moving puts objects in a safe but unspecified state.
-     *
      * @param other The instance to move from.
      * @return This any object.
      */
     basic_any &operator=(basic_any &&other) noexcept {
         reset();
 
-        if(other.mode == any_policy::embedded) {
-            other.vtable(request::move, other, this);
-        } else if(other.mode != any_policy::empty) {
-            instance = std::exchange(other.instance, nullptr);
+        if(other.vtable) {
+            other.vtable(operation::move, other, this);
+            info = other.info;
+            vtable = other.vtable;
+            mode = other.mode;
         }
 
-        info = other.info;
-        vtable = other.vtable;
-        mode = other.mode;
-
         return *this;
     }
 
@@ -284,8 +258,9 @@ public:
      * @param value An instance of an object to use to initialize the wrapper.
      * @return This any object.
      */
-    template<typename Type, typename = std::enable_if_t<!std::is_same_v<std::decay_t<Type>, basic_any>>>
-    basic_any &operator=(Type &&value) {
+    template<typename Type>
+    std::enable_if_t<!std::is_same_v<std::decay_t<Type>, basic_any>, basic_any &>
+    operator=(Type &&value) {
         emplace<std::decay_t<Type>>(std::forward<Type>(value));
         return *this;
     }
@@ -295,7 +270,7 @@ public:
      * @return The object type if any, `type_id<void>()` otherwise.
      */
     [[nodiscard]] const type_info &type() const noexcept {
-        return (info == nullptr) ? type_id<void>() : *info;
+        return *info;
     }
 
     /**
@@ -303,7 +278,7 @@ public:
      * @return An opaque pointer the contained instance, if any.
      */
     [[nodiscard]] const void *data() const noexcept {
-        return (mode == any_policy::embedded) ? vtable(request::get, *this, nullptr) : instance;
+        return vtable ? vtable(operation::get, *this, nullptr) : nullptr;
     }
 
     /**
@@ -312,7 +287,7 @@ public:
      * @return An opaque pointer the contained instance, if any.
      */
     [[nodiscard]] const void *data(const type_info &req) const noexcept {
-        return (type() == req) ? data() : nullptr;
+        return *info == req ? data() : nullptr;
     }
 
     /**
@@ -320,7 +295,7 @@ public:
      * @return An opaque pointer the contained instance, if any.
      */
     [[nodiscard]] void *data() noexcept {
-        return mode == any_policy::cref ? nullptr : const_cast<void *>(std::as_const(*this).data());
+        return mode == policy::cref ? nullptr : const_cast<void *>(std::as_const(*this).data());
     }
 
     /**
@@ -329,7 +304,7 @@ public:
      * @return An opaque pointer the contained instance, if any.
      */
     [[nodiscard]] void *data(const type_info &req) noexcept {
-        return mode == any_policy::cref ? nullptr : const_cast<void *>(std::as_const(*this).data(req));
+        return mode == policy::cref ? nullptr : const_cast<void *>(std::as_const(*this).data(req));
     }
 
     /**
@@ -350,22 +325,21 @@ public:
      * @return True in case of success, false otherwise.
      */
     bool assign(const basic_any &other) {
-        if(vtable && mode != any_policy::cref && *info == other.type()) {
-            return (vtable(request::assign, *this, other.data()) != nullptr);
+        if(vtable && mode != policy::cref && *info == *other.info) {
+            return (vtable(operation::assign, *this, other.data()) != nullptr);
         }
 
         return false;
     }
 
     /*! @copydoc assign */
-    // NOLINTNEXTLINE(cppcoreguidelines-rvalue-reference-param-not-moved)
     bool assign(basic_any &&other) {
-        if(vtable && mode != any_policy::cref && *info == other.type()) {
+        if(vtable && mode != policy::cref && *info == *other.info) {
             if(auto *val = other.data(); val) {
-                return (vtable(request::transfer, *this, val) != nullptr);
+                return (vtable(operation::transfer, *this, val) != nullptr);
+            } else {
+                return (vtable(operation::assign, *this, std::as_const(other).data()) != nullptr);
             }
-
-            return (vtable(request::assign, *this, std::as_const(other).data()) != nullptr);
         }
 
         return false;
@@ -373,14 +347,15 @@ public:
 
     /*! @brief Destroys contained object */
     void reset() {
-        if(owner()) {
-            vtable(request::destroy, *this, nullptr);
+        if(vtable && owner()) {
+            vtable(operation::destroy, *this, nullptr);
         }
 
-        instance = nullptr;
-        info = nullptr;
+        // unnecessary but it helps to detect nasty bugs
+        ENTT_ASSERT((instance = nullptr) == nullptr, "");
+        info = &type_id<void>();
         vtable = nullptr;
-        mode = any_policy::empty;
+        mode = policy::owner;
     }
 
     /**
@@ -397,8 +372,8 @@ public:
      * @return False if the two objects differ in their content, true otherwise.
      */
     [[nodiscard]] bool operator==(const basic_any &other) const noexcept {
-        if(vtable && *info == other.type()) {
-            return (vtable(request::compare, *this, other.data()) != nullptr);
+        if(vtable && *info == *other.info) {
+            return (vtable(operation::compare, *this, other.data()) != nullptr);
         }
 
         return (!vtable && !other.vtable);
@@ -418,12 +393,12 @@ public:
      * @return A wrapper that shares a reference to an unmanaged object.
      */
     [[nodiscard]] basic_any as_ref() noexcept {
-        return basic_any{*this, (mode == any_policy::cref ? any_policy::cref : any_policy::ref)};
+        return basic_any{*this, (mode == policy::cref ? policy::cref : policy::ref)};
     }
 
     /*! @copydoc as_ref */
     [[nodiscard]] basic_any as_ref() const noexcept {
-        return basic_any{*this, any_policy::cref};
+        return basic_any{*this, policy::cref};
     }
 
     /**
@@ -431,15 +406,7 @@ public:
      * @return True if the wrapper owns its object, false otherwise.
      */
     [[nodiscard]] bool owner() const noexcept {
-        return (mode == any_policy::dynamic || mode == any_policy::embedded);
-    }
-
-    /**
-     * @brief Returns the current mode of an any object.
-     * @return The current mode of the any object.
-     */
-    [[nodiscard]] any_policy policy() const noexcept {
-        return mode;
+        return (mode == policy::owner);
     }
 
 private:
@@ -447,9 +414,9 @@ private:
         const void *instance;
         storage_type storage;
     };
-    const type_info *info{};
-    vtable_type *vtable{};
-    any_policy mode{any_policy::empty};
+    const type_info *info;
+    vtable_type *vtable;
+    policy mode;
 };
 
 /**
@@ -461,7 +428,7 @@ private:
  * @return The element converted to the requested type.
  */
 template<typename Type, std::size_t Len, std::size_t Align>
-[[nodiscard]] std::remove_const_t<Type> any_cast(const basic_any<Len, Align> &data) noexcept {
+[[nodiscard]] Type any_cast(const basic_any<Len, Align> &data) noexcept {
     const auto *const instance = any_cast<std::remove_reference_t<Type>>(&data);
     ENTT_ASSERT(instance, "Invalid instance");
     return static_cast<Type>(*instance);
@@ -469,7 +436,7 @@ template<typename Type, std::size_t Len, std::size_t Align>
 
 /*! @copydoc any_cast */
 template<typename Type, std::size_t Len, std::size_t Align>
-[[nodiscard]] std::remove_const_t<Type> any_cast(basic_any<Len, Align> &data) noexcept {
+[[nodiscard]] Type any_cast(basic_any<Len, Align> &data) noexcept {
     // forces const on non-reference types to make them work also with wrappers for const references
     auto *const instance = any_cast<std::remove_reference_t<const Type>>(&data);
     ENTT_ASSERT(instance, "Invalid instance");
@@ -478,14 +445,13 @@ template<typename Type, std::size_t Len, std::size_t Align>
 
 /*! @copydoc any_cast */
 template<typename Type, std::size_t Len, std::size_t Align>
-// NOLINTNEXTLINE(cppcoreguidelines-rvalue-reference-param-not-moved)
-[[nodiscard]] std::remove_const_t<Type> any_cast(basic_any<Len, Align> &&data) noexcept {
+[[nodiscard]] Type any_cast(basic_any<Len, Align> &&data) noexcept {
     if constexpr(std::is_copy_constructible_v<std::remove_cv_t<std::remove_reference_t<Type>>>) {
         if(auto *const instance = any_cast<std::remove_reference_t<Type>>(&data); instance) {
             return static_cast<Type>(std::move(*instance));
+        } else {
+            return any_cast<Type>(data);
         }
-
-        return any_cast<Type>(data);
     } else {
         auto *const instance = any_cast<std::remove_reference_t<Type>>(&data);
         ENTT_ASSERT(instance, "Invalid instance");

src/entt/core/bit.hpp

@@ -1,70 +0,0 @@
-#ifndef ENTT_CORE_BIT_HPP
-#define ENTT_CORE_BIT_HPP
-
-#include <cstddef>
-#include <limits>
-#include <type_traits>
-#include "../config/config.h"
-
-namespace entt {
-
-/**
- * @brief Returns the number of set bits in a value (waiting for C++20 and
- * `std::popcount`).
- * @tparam Type Unsigned integer type.
- * @param value A value of unsigned integer type.
- * @return The number of set bits in the value.
- */
-template<typename Type>
-[[nodiscard]] constexpr std::enable_if_t<std::is_unsigned_v<Type>, int> popcount(const Type value) noexcept {
-    return value ? (int(value & 1) + popcount(static_cast<Type>(value >> 1))) : 0;
-}
-
-/**
- * @brief Checks whether a value is a power of two or not (waiting for C++20 and
- * `std::has_single_bit`).
- * @tparam Type Unsigned integer type.
- * @param value A value of unsigned integer type.
- * @return True if the value is a power of two, false otherwise.
- */
-template<typename Type>
-[[nodiscard]] constexpr std::enable_if_t<std::is_unsigned_v<Type>, bool> has_single_bit(const Type value) noexcept {
-    return value && ((value & (value - 1)) == 0);
-}
-
-/**
- * @brief Computes the smallest power of two greater than or equal to a value
- * (waiting for C++20 and `std::bit_ceil`).
- * @tparam Type Unsigned integer type.
- * @param value A value of unsigned integer type.
- * @return The smallest power of two greater than or equal to the given value.
- */
-template<typename Type>
-[[nodiscard]] constexpr std::enable_if_t<std::is_unsigned_v<Type>, Type> next_power_of_two(const Type value) noexcept {
-    // NOLINTNEXTLINE(bugprone-assert-side-effect)
-    ENTT_ASSERT_CONSTEXPR(value < (Type{1u} << (std::numeric_limits<Type>::digits - 1)), "Numeric limits exceeded");
-    Type curr = value - (value != 0u);
-
-    for(int next = 1; next < std::numeric_limits<Type>::digits; next = next * 2) {
-        curr |= (curr >> next);
-    }
-
-    return ++curr;
-}
-
-/**
- * @brief Fast module utility function (powers of two only).
- * @tparam Type Unsigned integer type.
- * @param value A value of unsigned integer type.
- * @param mod _Modulus_, it must be a power of two.
- * @return The common remainder.
- */
-template<typename Type>
-[[nodiscard]] constexpr std::enable_if_t<std::is_unsigned_v<Type>, Type> fast_mod(const Type value, const std::size_t mod) noexcept {
-    ENTT_ASSERT_CONSTEXPR(has_single_bit(mod), "Value must be a power of two");
-    return static_cast<Type>(value & (mod - 1u));
-}
-
-} // namespace entt
-
-#endif

src/entt/core/compressed_pair.hpp

@@ -5,12 +5,15 @@
 #include <tuple>
 #include <type_traits>
 #include <utility>
-#include "fwd.hpp"
 #include "type_traits.hpp"
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 template<typename Type, std::size_t, typename = void>
@@ -18,9 +21,9 @@ struct compressed_pair_element {
     using reference = Type &;
     using const_reference = const Type &;
 
-    template<typename Dummy = Type, typename = std::enable_if_t<std::is_default_constructible_v<Dummy>>>
-    // NOLINTNEXTLINE(modernize-use-equals-default)
-    constexpr compressed_pair_element() noexcept(std::is_nothrow_default_constructible_v<Type>) {}
+    template<bool Dummy = true, typename = std::enable_if_t<Dummy && std::is_default_constructible_v<Type>>>
+    constexpr compressed_pair_element() noexcept(std::is_nothrow_default_constructible_v<Type>)
+        : value{} {}
 
     template<typename Arg, typename = std::enable_if_t<!std::is_same_v<std::remove_cv_t<std::remove_reference_t<Arg>>, compressed_pair_element>>>
     constexpr compressed_pair_element(Arg &&arg) noexcept(std::is_nothrow_constructible_v<Type, Arg>)
@@ -39,7 +42,7 @@ struct compressed_pair_element {
     }
 
 private:
-    Type value{};
+    Type value;
 };
 
 template<typename Type, std::size_t Tag>
@@ -48,7 +51,7 @@ struct compressed_pair_element<Type, Tag, std::enable_if_t<is_ebco_eligible_v<Ty
     using const_reference = const Type &;
     using base_type = Type;
 
-    template<typename Dummy = Type, typename = std::enable_if_t<std::is_default_constructible_v<Dummy>>>
+    template<bool Dummy = true, typename = std::enable_if_t<Dummy && std::is_default_constructible_v<base_type>>>
     constexpr compressed_pair_element() noexcept(std::is_nothrow_default_constructible_v<base_type>)
         : base_type{} {}
 
@@ -70,7 +73,11 @@ struct compressed_pair_element<Type, Tag, std::enable_if_t<is_ebco_eligible_v<Ty
 };
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /**
  * @brief A compressed pair.
@@ -103,7 +110,7 @@ public:
      * @tparam Dummy Dummy template parameter used for internal purposes.
      */
     template<bool Dummy = true, typename = std::enable_if_t<Dummy && std::is_default_constructible_v<first_type> && std::is_default_constructible_v<second_type>>>
-    constexpr compressed_pair() noexcept(std::is_nothrow_default_constructible_v<first_base> && std::is_nothrow_default_constructible_v<second_base>)
+    constexpr compressed_pair() noexcept(std::is_nothrow_default_constructible_v<first_base> &&std::is_nothrow_default_constructible_v<second_base>)
         : first_base{},
           second_base{} {}
 
@@ -111,13 +118,13 @@ public:
      * @brief Copy constructor.
      * @param other The instance to copy from.
      */
-    constexpr compressed_pair(const compressed_pair &other) = default;
+    constexpr compressed_pair(const compressed_pair &other) noexcept(std::is_nothrow_copy_constructible_v<first_base> &&std::is_nothrow_copy_constructible_v<second_base>) = default;
 
     /**
      * @brief Move constructor.
      * @param other The instance to move from.
      */
-    constexpr compressed_pair(compressed_pair &&other) noexcept = default;
+    constexpr compressed_pair(compressed_pair &&other) noexcept(std::is_nothrow_move_constructible_v<first_base> &&std::is_nothrow_move_constructible_v<second_base>) = default;
 
     /**
      * @brief Constructs a pair from its values.
@@ -127,7 +134,7 @@ public:
      * @param other Value to use to initialize the second element.
      */
     template<typename Arg, typename Other>
-    constexpr compressed_pair(Arg &&arg, Other &&other) noexcept(std::is_nothrow_constructible_v<first_base, Arg> && std::is_nothrow_constructible_v<second_base, Other>)
+    constexpr compressed_pair(Arg &&arg, Other &&other) noexcept(std::is_nothrow_constructible_v<first_base, Arg> &&std::is_nothrow_constructible_v<second_base, Other>)
         : first_base{std::forward<Arg>(arg)},
           second_base{std::forward<Other>(other)} {}
 
@@ -139,26 +146,23 @@ public:
      * @param other Arguments to use to initialize the second element.
      */
     template<typename... Args, typename... Other>
-    constexpr compressed_pair(std::piecewise_construct_t, std::tuple<Args...> args, std::tuple<Other...> other) noexcept(std::is_nothrow_constructible_v<first_base, Args...> && std::is_nothrow_constructible_v<second_base, Other...>)
+    constexpr compressed_pair(std::piecewise_construct_t, std::tuple<Args...> args, std::tuple<Other...> other) noexcept(std::is_nothrow_constructible_v<first_base, Args...> &&std::is_nothrow_constructible_v<second_base, Other...>)
         : first_base{std::move(args), std::index_sequence_for<Args...>{}},
           second_base{std::move(other), std::index_sequence_for<Other...>{}} {}
 
-    /*! @brief Default destructor. */
-    ~compressed_pair() = default;
-
     /**
      * @brief Copy assignment operator.
      * @param other The instance to copy from.
      * @return This compressed pair object.
      */
-    constexpr compressed_pair &operator=(const compressed_pair &other) = default;
+    constexpr compressed_pair &operator=(const compressed_pair &other) noexcept(std::is_nothrow_copy_assignable_v<first_base> &&std::is_nothrow_copy_assignable_v<second_base>) = default;
 
     /**
      * @brief Move assignment operator.
      * @param other The instance to move from.
      * @return This compressed pair object.
      */
-    constexpr compressed_pair &operator=(compressed_pair &&other) noexcept = default;
+    constexpr compressed_pair &operator=(compressed_pair &&other) noexcept(std::is_nothrow_move_assignable_v<first_base> &&std::is_nothrow_move_assignable_v<second_base>) = default;
 
     /**
      * @brief Returns the first element that a pair stores.
@@ -190,7 +194,7 @@ public:
      * @brief Swaps two compressed pair objects.
      * @param other The compressed pair to swap with.
      */
-    constexpr void swap(compressed_pair &other) noexcept {
+    constexpr void swap(compressed_pair &other) noexcept(std::is_nothrow_swappable_v<first_type> &&std::is_nothrow_swappable_v<second_type>) {
         using std::swap;
         swap(first(), other.first());
         swap(second(), other.second());
@@ -203,7 +207,7 @@ public:
      * reference to the second element if `Index` is 1.
      */
     template<std::size_t Index>
-    [[nodiscard]] constexpr decltype(auto) get() noexcept {
+    constexpr decltype(auto) get() noexcept {
         if constexpr(Index == 0u) {
             return first();
         } else {
@@ -214,7 +218,7 @@ public:
 
     /*! @copydoc get */
     template<std::size_t Index>
-    [[nodiscard]] constexpr decltype(auto) get() const noexcept {
+    constexpr decltype(auto) get() const noexcept {
         if constexpr(Index == 0u) {
             return first();
         } else {
@@ -240,12 +244,14 @@ compressed_pair(Type &&, Other &&) -> compressed_pair<std::decay_t<Type>, std::d
  * @param rhs A valid compressed pair object.
  */
 template<typename First, typename Second>
-constexpr void swap(compressed_pair<First, Second> &lhs, compressed_pair<First, Second> &rhs) noexcept {
+inline constexpr void swap(compressed_pair<First, Second> &lhs, compressed_pair<First, Second> &rhs) {
     lhs.swap(rhs);
 }
 
 } // namespace entt
 
+// disable structured binding support for clang 6, it messes when specializing tuple_size
+#if !defined __clang_major__ || __clang_major__ > 6
 namespace std {
 
 /**
@@ -268,5 +274,6 @@ struct tuple_element<Index, entt::compressed_pair<First, Second>>: conditional<I
 };
 
 } // namespace std
+#endif
 
 #endif

src/entt/core/family.hpp

@@ -15,7 +15,6 @@ namespace entt {
  */
 template<typename...>
 class family {
-    // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
     inline static ENTT_MAYBE_ATOMIC(id_type) identifier{};
 
 public:

src/entt/core/fwd.hpp

@@ -2,26 +2,10 @@
 #define ENTT_CORE_FWD_HPP
 
 #include <cstddef>
-#include <cstdint>
 #include "../config/config.h"
 
 namespace entt {
 
-/*! @brief Possible modes of an any object. */
-enum class any_policy : std::uint8_t {
-    /*! @brief Default mode, the object does not own any elements. */
-    empty,
-    /*! @brief Owning mode, the object owns a dynamically allocated element. */
-    dynamic,
-    /*! @brief Owning mode, the object owns an embedded element. */
-    embedded,
-    /*! @brief Aliasing mode, the object _points_ to a non-const element. */
-    ref,
-    /*! @brief Const aliasing mode, the object _points_ to a const element. */
-    cref
-};
-
-// NOLINTNEXTLINE(cppcoreguidelines-avoid-c-arrays, modernize-avoid-c-arrays)
 template<std::size_t Len = sizeof(double[2]), std::size_t = alignof(double[2])>
 class basic_any;
 
@@ -31,21 +15,6 @@ using id_type = ENTT_ID_TYPE;
 /*! @brief Alias declaration for the most common use case. */
 using any = basic_any<>;
 
-template<typename, typename>
-class compressed_pair;
-
-template<typename>
-class basic_hashed_string;
-
-/*! @brief Aliases for common character types. */
-using hashed_string = basic_hashed_string<char>;
-
-/*! @brief Aliases for common character types. */
-using hashed_wstring = basic_hashed_string<wchar_t>;
-
-// NOLINTNEXTLINE(bugprone-forward-declaration-namespace)
-struct type_info;
-
 } // namespace entt
 
 #endif

src/entt/core/hashed_string.hpp

@@ -3,27 +3,32 @@
 
 #include <cstddef>
 #include <cstdint>
-#include <string_view>
 #include "fwd.hpp"
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
-template<typename = id_type>
-struct fnv_1a_params;
+template<typename>
+struct fnv1a_traits;
 
 template<>
-struct fnv_1a_params<std::uint32_t> {
-    static constexpr auto offset = 2166136261;
-    static constexpr auto prime = 16777619;
+struct fnv1a_traits<std::uint32_t> {
+    using type = std::uint32_t;
+    static constexpr std::uint32_t offset = 2166136261;
+    static constexpr std::uint32_t prime = 16777619;
 };
 
 template<>
-struct fnv_1a_params<std::uint64_t> {
-    static constexpr auto offset = 14695981039346656037ull;
-    static constexpr auto prime = 1099511628211ull;
+struct fnv1a_traits<std::uint64_t> {
+    using type = std::uint64_t;
+    static constexpr std::uint64_t offset = 14695981039346656037ull;
+    static constexpr std::uint64_t prime = 1099511628211ull;
 };
 
 template<typename Char>
@@ -38,7 +43,11 @@ struct basic_hashed_string {
 };
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /**
  * @brief Zero overhead unique identifier.
@@ -58,7 +67,7 @@ struct basic_hashed_string {
 template<typename Char>
 class basic_hashed_string: internal::basic_hashed_string<Char> {
     using base_type = internal::basic_hashed_string<Char>;
-    using params = internal::fnv_1a_params<>;
+    using traits_type = internal::fnv1a_traits<id_type>;
 
     struct const_wrapper {
         // non-explicit constructor on purpose
@@ -69,11 +78,22 @@ class basic_hashed_string: internal::basic_hashed_string<Char> {
     };
 
     // Fowler–Noll–Vo hash function v. 1a - the good
-    [[nodiscard]] static constexpr auto helper(const std::basic_string_view<Char> view) noexcept {
-        base_type base{view.data(), view.size(), params::offset};
+    [[nodiscard]] static constexpr auto helper(const Char *str) noexcept {
+        base_type base{str, 0u, traits_type::offset};
 
-        for(auto &&curr: view) {
-            base.hash = (base.hash ^ static_cast<id_type>(curr)) * params::prime;
+        for(; str[base.length]; ++base.length) {
+            base.hash = (base.hash ^ static_cast<traits_type::type>(str[base.length])) * traits_type::prime;
+        }
+
+        return base;
+    }
+
+    // Fowler–Noll–Vo hash function v. 1a - the good
+    [[nodiscard]] static constexpr auto helper(const Char *str, const std::size_t len) noexcept {
+        base_type base{str, len, traits_type::offset};
+
+        for(size_type pos{}; pos < len; ++pos) {
+            base.hash = (base.hash ^ static_cast<traits_type::type>(str[pos])) * traits_type::prime;
         }
 
         return base;
@@ -104,8 +124,7 @@ public:
      * @return The numeric representation of the string.
      */
     template<std::size_t N>
-    // NOLINTNEXTLINE(cppcoreguidelines-avoid-c-arrays, modernize-avoid-c-arrays)
-    [[nodiscard]] static ENTT_CONSTEVAL hash_type value(const value_type (&str)[N]) noexcept {
+    [[nodiscard]] static constexpr hash_type value(const value_type (&str)[N]) noexcept {
         return basic_hashed_string{str};
     }
 
@@ -120,7 +139,7 @@ public:
 
     /*! @brief Constructs an empty hashed string. */
     constexpr basic_hashed_string() noexcept
-        : basic_hashed_string{nullptr, 0u} {}
+        : base_type{} {}
 
     /**
      * @brief Constructs a hashed string from a string view.
@@ -128,7 +147,7 @@ public:
      * @param len Length of the string to hash.
      */
     constexpr basic_hashed_string(const value_type *str, const size_type len) noexcept
-        : base_type{helper({str, len})} {}
+        : base_type{helper(str, len)} {}
 
     /**
      * @brief Constructs a hashed string from an array of const characters.
@@ -136,9 +155,8 @@ public:
      * @param str Human-readable identifier.
      */
     template<std::size_t N>
-    // NOLINTNEXTLINE(cppcoreguidelines-avoid-c-arrays, modernize-avoid-c-arrays)
-    ENTT_CONSTEVAL basic_hashed_string(const value_type (&str)[N]) noexcept
-        : base_type{helper({static_cast<const value_type *>(str)})} {}
+    constexpr basic_hashed_string(const value_type (&str)[N]) noexcept
+        : base_type{helper(str)} {}
 
     /**
      * @brief Explicit constructor on purpose to avoid constructing a hashed
@@ -150,7 +168,7 @@ public:
      * @param wrapper Helps achieving the purpose by relying on overloading.
      */
     explicit constexpr basic_hashed_string(const_wrapper wrapper) noexcept
-        : base_type{helper({wrapper.repr})} {}
+        : base_type{helper(wrapper.repr)} {}
 
     /**
      * @brief Returns the size a hashed string.
@@ -197,7 +215,7 @@ public:
  * @param len Length of the string to hash.
  */
 template<typename Char>
-basic_hashed_string(const Char *str, std::size_t len) -> basic_hashed_string<Char>;
+basic_hashed_string(const Char *str, const std::size_t len) -> basic_hashed_string<Char>;
 
 /**
  * @brief Deduction guide.
@@ -206,7 +224,6 @@ basic_hashed_string(const Char *str, std::size_t len) -> basic_hashed_string<Cha
  * @param str Human-readable identifier.
  */
 template<typename Char, std::size_t N>
-// NOLINTNEXTLINE(cppcoreguidelines-avoid-c-arrays, modernize-avoid-c-arrays)
 basic_hashed_string(const Char (&str)[N]) -> basic_hashed_string<Char>;
 
 /**
@@ -284,6 +301,12 @@ template<typename Char>
     return !(lhs < rhs);
 }
 
+/*! @brief Aliases for common character types. */
+using hashed_string = basic_hashed_string<char>;
+
+/*! @brief Aliases for common character types. */
+using hashed_wstring = basic_hashed_string<wchar_t>;
+
 inline namespace literals {
 
 /**
@@ -291,7 +314,7 @@ inline namespace literals {
  * @param str The literal without its suffix.
  * @return A properly initialized hashed string.
  */
-[[nodiscard]] ENTT_CONSTEVAL hashed_string operator""_hs(const char *str, std::size_t) noexcept {
+[[nodiscard]] constexpr hashed_string operator"" _hs(const char *str, std::size_t) noexcept {
     return hashed_string{str};
 }
 
@@ -300,7 +323,7 @@ inline namespace literals {
  * @param str The literal without its suffix.
  * @return A properly initialized hashed wstring.
  */
-[[nodiscard]] ENTT_CONSTEVAL hashed_wstring operator""_hws(const wchar_t *str, std::size_t) noexcept {
+[[nodiscard]] constexpr hashed_wstring operator"" _hws(const wchar_t *str, std::size_t) noexcept {
     return hashed_wstring{str};
 }
 

src/entt/core/iterator.hpp

@@ -92,7 +92,7 @@ public:
      * @return This iota iterator.
      */
     constexpr iota_iterator operator++(int) noexcept {
-        const iota_iterator orig = *this;
+        iota_iterator orig = *this;
         return ++(*this), orig;
     }
 
@@ -147,7 +147,7 @@ struct iterable_adaptor final {
     using sentinel = Sentinel;
 
     /*! @brief Default constructor. */
-    constexpr iterable_adaptor() noexcept(std::is_nothrow_default_constructible_v<iterator> && std::is_nothrow_default_constructible_v<sentinel>)
+    constexpr iterable_adaptor() noexcept(std::is_nothrow_default_constructible_v<iterator> &&std::is_nothrow_default_constructible_v<sentinel>)
         : first{},
           last{} {}
 
@@ -156,7 +156,7 @@ struct iterable_adaptor final {
      * @param from Begin iterator.
      * @param to End iterator.
      */
-    constexpr iterable_adaptor(iterator from, sentinel to) noexcept(std::is_nothrow_move_constructible_v<iterator> && std::is_nothrow_move_constructible_v<sentinel>)
+    constexpr iterable_adaptor(iterator from, sentinel to) noexcept(std::is_nothrow_move_constructible_v<iterator> &&std::is_nothrow_move_constructible_v<sentinel>)
         : first{std::move(from)},
           last{std::move(to)} {}
 

src/entt/core/memory.hpp

@@ -2,6 +2,7 @@
 #define ENTT_CORE_MEMORY_HPP
 
 #include <cstddef>
+#include <limits>
 #include <memory>
 #include <tuple>
 #include <type_traits>
@@ -10,6 +11,42 @@
 
 namespace entt {
 
+/**
+ * @brief Checks whether a value is a power of two or not.
+ * @param value A value that may or may not be a power of two.
+ * @return True if the value is a power of two, false otherwise.
+ */
+[[nodiscard]] inline constexpr bool is_power_of_two(const std::size_t value) noexcept {
+    return value && ((value & (value - 1)) == 0);
+}
+
+/**
+ * @brief Computes the smallest power of two greater than or equal to a value.
+ * @param value The value to use.
+ * @return The smallest power of two greater than or equal to the given value.
+ */
+[[nodiscard]] inline constexpr std::size_t next_power_of_two(const std::size_t value) noexcept {
+    ENTT_ASSERT_CONSTEXPR(value < (std::size_t{1u} << (std::numeric_limits<std::size_t>::digits - 1)), "Numeric limits exceeded");
+    std::size_t curr = value - (value != 0u);
+
+    for(int next = 1; next < std::numeric_limits<std::size_t>::digits; next = next * 2) {
+        curr |= curr >> next;
+    }
+
+    return ++curr;
+}
+
+/**
+ * @brief Fast module utility function (powers of two only).
+ * @param value A value for which to calculate the modulus.
+ * @param mod _Modulus_, it must be a power of two.
+ * @return The common remainder.
+ */
+[[nodiscard]] inline constexpr std::size_t fast_mod(const std::size_t value, const std::size_t mod) noexcept {
+    ENTT_ASSERT_CONSTEXPR(is_power_of_two(mod), "Value must be a power of two");
+    return value & (mod - 1u);
+}
+
 /**
  * @brief Unwraps fancy pointers, does nothing otherwise (waiting for C++20).
  * @tparam Type Pointer type.
@@ -126,7 +163,11 @@ ENTT_CONSTEXPR auto allocate_unique(Allocator &allocator, Args &&...args) {
     return std::unique_ptr<Type, allocation_deleter<allocator_type>>{ptr, alloc};
 }
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 template<typename Type>
@@ -182,7 +223,11 @@ struct uses_allocator_construction<std::pair<Type, Other>> {
 };
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /**
  * @brief Uses-allocator construction utility (waiting for C++20).
@@ -236,7 +281,7 @@ constexpr Type make_obj_using_allocator(const Allocator &allocator, Args &&...ar
  */
 template<typename Type, typename Allocator, typename... Args>
 constexpr Type *uninitialized_construct_using_allocator(Type *value, const Allocator &allocator, Args &&...args) {
-    return std::apply([value](auto &&...curr) { return ::new(value) Type(std::forward<decltype(curr)>(curr)...); }, internal::uses_allocator_construction<Type>::args(allocator, std::forward<Args>(args)...));
+    return std::apply([value](auto &&...curr) { return new(value) Type(std::forward<decltype(curr)>(curr)...); }, internal::uses_allocator_construction<Type>::args(allocator, std::forward<Args>(args)...));
 }
 
 } // namespace entt

src/entt/core/monostate.hpp

@@ -23,12 +23,10 @@ struct monostate {
      * @brief Assigns a value of a specific type to a given key.
      * @tparam Type Type of the value to assign.
      * @param val User data to assign to the given key.
-     * @return This monostate object.
      */
     template<typename Type>
-    monostate &operator=(Type val) noexcept {
+    void operator=(Type val) const noexcept {
         value<Type> = val;
-        return *this;
     }
 
     /**
@@ -43,7 +41,6 @@ struct monostate {
 
 private:
     template<typename Type>
-    // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
     inline static ENTT_MAYBE_ATOMIC(Type) value{};
 };
 
@@ -52,8 +49,7 @@ private:
  * @tparam Value Value used to differentiate between different variables.
  */
 template<id_type Value>
-// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
-inline monostate<Value> monostate_v{};
+inline monostate<Value> monostate_v = {};
 
 } // namespace entt
 

src/entt/core/ranges.hpp

@@ -1,20 +0,0 @@
-#ifndef ENTT_CORE_RANGES_HPP
-#define ENTT_CORE_RANGES_HPP
-
-#if __has_include(<version>)
-#    include <version>
-#
-#    if defined(__cpp_lib_ranges)
-#        include <ranges>
-#        include "iterator.hpp"
-
-template<class... Args>
-inline constexpr bool std::ranges::enable_borrowed_range<entt::iterable_adaptor<Args...>>{true};
-
-template<class... Args>
-inline constexpr bool std::ranges::enable_view<entt::iterable_adaptor<Args...>>{true};
-
-#    endif
-#endif
-
-#endif

src/entt/core/tuple.hpp

@@ -7,20 +7,33 @@
 
 namespace entt {
 
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
+namespace internal {
+
+template<typename>
+struct is_tuple_impl: std::false_type {};
+
+template<typename... Args>
+struct is_tuple_impl<std::tuple<Args...>>: std::true_type {};
+
+} // namespace internal
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
+
 /**
  * @brief Provides the member constant `value` to true if a given type is a
  * tuple, false otherwise.
  * @tparam Type The type to test.
  */
 template<typename Type>
-struct is_tuple: std::false_type {};
-
-/**
- * @copybrief is_tuple
- * @tparam Args Tuple template arguments.
- */
-template<typename... Args>
-struct is_tuple<std::tuple<Args...>>: std::true_type {};
+struct is_tuple: internal::is_tuple_impl<std::remove_cv_t<Type>> {};
 
 /**
  * @brief Helper variable template.

src/entt/core/type_info.hpp

@@ -11,7 +11,11 @@
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 struct ENTT_API type_index final {
@@ -24,7 +28,7 @@ struct ENTT_API type_index final {
 template<typename Type>
 [[nodiscard]] constexpr auto stripped_type_name() noexcept {
 #if defined ENTT_PRETTY_FUNCTION
-    const std::string_view pretty_function{static_cast<const char *>(ENTT_PRETTY_FUNCTION)};
+    std::string_view pretty_function{ENTT_PRETTY_FUNCTION};
     auto first = pretty_function.find_first_not_of(' ', pretty_function.find_first_of(ENTT_PRETTY_FUNCTION_PREFIX) + 1);
     auto value = pretty_function.substr(first, pretty_function.find_last_of(ENTT_PRETTY_FUNCTION_SUFFIX) - first);
     return value;
@@ -34,26 +38,26 @@ template<typename Type>
 }
 
 template<typename Type, auto = stripped_type_name<Type>().find_first_of('.')>
-[[nodiscard]] constexpr std::string_view type_name(int) noexcept {
+[[nodiscard]] static constexpr std::string_view type_name(int) noexcept {
     constexpr auto value = stripped_type_name<Type>();
     return value;
 }
 
 template<typename Type>
-[[nodiscard]] std::string_view type_name(char) noexcept {
+[[nodiscard]] static std::string_view type_name(char) noexcept {
     static const auto value = stripped_type_name<Type>();
     return value;
 }
 
 template<typename Type, auto = stripped_type_name<Type>().find_first_of('.')>
-[[nodiscard]] constexpr id_type type_hash(int) noexcept {
+[[nodiscard]] static constexpr id_type type_hash(int) noexcept {
     constexpr auto stripped = stripped_type_name<Type>();
     constexpr auto value = hashed_string::value(stripped.data(), stripped.size());
     return value;
 }
 
 template<typename Type>
-[[nodiscard]] id_type type_hash(char) noexcept {
+[[nodiscard]] static id_type type_hash(char) noexcept {
     static const auto value = [](const auto stripped) {
         return hashed_string::value(stripped.data(), stripped.size());
     }(stripped_type_name<Type>());
@@ -61,7 +65,11 @@ template<typename Type>
 }
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /**
  * @brief Type sequential identifier.
@@ -136,12 +144,10 @@ struct type_info final {
      * @tparam Type Type for which to construct a type info object.
      */
     template<typename Type>
-    // NOLINTBEGIN(modernize-use-transparent-functors)
     constexpr type_info(std::in_place_type_t<Type>) noexcept
         : seq{type_index<std::remove_cv_t<std::remove_reference_t<Type>>>::value()},
           identifier{type_hash<std::remove_cv_t<std::remove_reference_t<Type>>>::value()},
           alias{type_name<std::remove_cv_t<std::remove_reference_t<Type>>>::value()} {}
-    // NOLINTEND(modernize-use-transparent-functors)
 
     /**
      * @brief Type index.
@@ -179,7 +185,7 @@ private:
  * @param rhs A type info object.
  * @return True if the two type info objects are identical, false otherwise.
  */
-[[nodiscard]] constexpr bool operator==(const type_info &lhs, const type_info &rhs) noexcept {
+[[nodiscard]] inline constexpr bool operator==(const type_info &lhs, const type_info &rhs) noexcept {
     return lhs.hash() == rhs.hash();
 }
 
@@ -189,7 +195,7 @@ private:
  * @param rhs A type info object.
  * @return True if the two type info objects differ, false otherwise.
  */
-[[nodiscard]] constexpr bool operator!=(const type_info &lhs, const type_info &rhs) noexcept {
+[[nodiscard]] inline constexpr bool operator!=(const type_info &lhs, const type_info &rhs) noexcept {
     return !(lhs == rhs);
 }
 
@@ -250,7 +256,7 @@ private:
 template<typename Type>
 [[nodiscard]] const type_info &type_id() noexcept {
     if constexpr(std::is_same_v<Type, std::remove_cv_t<std::remove_reference_t<Type>>>) {
-        static const type_info instance{std::in_place_type<Type>};
+        static type_info instance{std::in_place_type<Type>};
         return instance;
     } else {
         return type_id<std::remove_cv_t<std::remove_reference_t<Type>>>();
@@ -259,7 +265,6 @@ template<typename Type>
 
 /*! @copydoc type_id */
 template<typename Type>
-// NOLINTNEXTLINE(cppcoreguidelines-missing-std-forward)
 [[nodiscard]] const type_info &type_id(Type &&) noexcept {
     return type_id<std::remove_cv_t<std::remove_reference_t<Type>>>();
 }

src/entt/core/type_traits.hpp

@@ -17,7 +17,7 @@ namespace entt {
  */
 template<std::size_t N>
 struct choice_t
-    // unfortunately, doxygen cannot parse such a construct
+    // Unfortunately, doxygen cannot parse such a construct.
     : /*! @cond TURN_OFF_DOXYGEN */ choice_t<N - 1> /*! @endcond */
 {};
 
@@ -63,7 +63,6 @@ struct size_of: std::integral_constant<std::size_t, 0u> {};
 /*! @copydoc size_of */
 template<typename Type>
 struct size_of<Type, std::void_t<decltype(sizeof(Type))>>
-    // NOLINTNEXTLINE(bugprone-sizeof-expression)
     : std::integral_constant<std::size_t, sizeof(Type)> {};
 
 /**
@@ -251,40 +250,37 @@ struct type_list_cat<type_list<Type...>> {
 template<typename... List>
 using type_list_cat_t = typename type_list_cat<List...>::type;
 
-/*! @cond TURN_OFF_DOXYGEN */
-namespace internal {
-
-template<typename...>
+/*! @brief Primary template isn't defined on purpose. */
+template<typename>
 struct type_list_unique;
 
-template<typename First, typename... Other, typename... Type>
-struct type_list_unique<type_list<First, Other...>, Type...>
-    : std::conditional_t<(std::is_same_v<First, Type> || ...), type_list_unique<type_list<Other...>, Type...>, type_list_unique<type_list<Other...>, Type..., First>> {};
-
-template<typename... Type>
-struct type_list_unique<type_list<>, Type...> {
-    using type = type_list<Type...>;
-};
-
-} // namespace internal
-/*! @endcond */
-
 /**
  * @brief Removes duplicates types from a type list.
- * @tparam List Type list.
+ * @tparam Type One of the types provided by the given type list.
+ * @tparam Other The other types provided by the given type list.
  */
-template<typename List>
-struct type_list_unique {
+template<typename Type, typename... Other>
+struct type_list_unique<type_list<Type, Other...>> {
     /*! @brief A type list without duplicate types. */
-    using type = typename internal::type_list_unique<List>::type;
+    using type = std::conditional_t<
+        (std::is_same_v<Type, Other> || ...),
+        typename type_list_unique<type_list<Other...>>::type,
+        type_list_cat_t<type_list<Type>, typename type_list_unique<type_list<Other...>>::type>>;
+};
+
+/*! @brief Removes duplicates types from a type list. */
+template<>
+struct type_list_unique<type_list<>> {
+    /*! @brief A type list without duplicate types. */
+    using type = type_list<>;
 };
 
 /**
  * @brief Helper type.
- * @tparam List Type list.
+ * @tparam Type A type list.
  */
-template<typename List>
-using type_list_unique_t = typename type_list_unique<List>::type;
+template<typename Type>
+using type_list_unique_t = typename type_list_unique<Type>::type;
 
 /**
  * @brief Provides the member constant `value` to true if a type list contains a
@@ -346,7 +342,6 @@ struct type_list_transform;
 template<typename... Type, template<typename...> class Op>
 struct type_list_transform<type_list<Type...>, Op> {
     /*! @brief Resulting type list after applying the transform function. */
-    // NOLINTNEXTLINE(modernize-type-traits)
     using type = type_list<typename Op<Type>::type...>;
 };
 
@@ -576,7 +571,7 @@ inline constexpr bool value_list_contains_v = value_list_contains<List, Value>::
 
 /*! @brief Primary template isn't defined on purpose. */
 template<typename...>
-struct value_list_diff;
+class value_list_diff;
 
 /**
  * @brief Computes the difference between two value lists.
@@ -584,9 +579,12 @@ struct value_list_diff;
  * @tparam Other Values provided by the second value list.
  */
 template<auto... Value, auto... Other>
-struct value_list_diff<value_list<Value...>, value_list<Other...>> {
+class value_list_diff<value_list<Value...>, value_list<Other...>> {
+    using v141_toolset_workaround = value_list<Other...>;
+
+public:
     /*! @brief A value list that is the difference between the two value lists. */
-    using type = value_list_cat_t<std::conditional_t<value_list_contains_v<value_list<Other...>, Value>, value_list<>, value_list<Value>>...>;
+    using type = value_list_cat_t<std::conditional_t<value_list_contains_v<v141_toolset_workaround, Value>, value_list<>, value_list<Value>>...>;
 };
 
 /**
@@ -677,7 +675,11 @@ inline constexpr bool is_complete_v = is_complete<Type>::value;
 template<typename Type, typename = void>
 struct is_iterator: std::false_type {};
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 template<typename, typename = void>
@@ -687,11 +689,15 @@ template<typename Type>
 struct has_iterator_category<Type, std::void_t<typename std::iterator_traits<Type>::iterator_category>>: std::true_type {};
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /*! @copydoc is_iterator */
 template<typename Type>
-struct is_iterator<Type, std::enable_if_t<!std::is_void_v<std::remove_cv_t<std::remove_pointer_t<Type>>>>>
+struct is_iterator<Type, std::enable_if_t<!std::is_same_v<std::remove_cv_t<std::remove_pointer_t<Type>>, void>>>
     : internal::has_iterator_category<Type> {};
 
 /**
@@ -736,7 +742,19 @@ struct is_transparent<Type, std::void_t<typename Type::is_transparent>>: std::tr
 template<typename Type>
 inline constexpr bool is_transparent_v = is_transparent<Type>::value;
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @brief Provides the member constant `value` to true if a given type is
+ * equality comparable, false otherwise.
+ * @tparam Type The type to test.
+ */
+template<typename Type, typename = void>
+struct is_equality_comparable: std::false_type {};
+
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 template<typename, typename = void>
@@ -745,67 +763,51 @@ struct has_tuple_size_value: std::false_type {};
 template<typename Type>
 struct has_tuple_size_value<Type, std::void_t<decltype(std::tuple_size<const Type>::value)>>: std::true_type {};
 
-template<typename, typename = void>
-struct has_value_type: std::false_type {};
-
-template<typename Type>
-struct has_value_type<Type, std::void_t<typename Type::value_type>>: std::true_type {};
-
-template<typename>
-[[nodiscard]] constexpr bool dispatch_is_equality_comparable();
-
 template<typename Type, std::size_t... Index>
 [[nodiscard]] constexpr bool unpack_maybe_equality_comparable(std::index_sequence<Index...>) {
-    return (dispatch_is_equality_comparable<std::tuple_element_t<Index, Type>>() && ...);
+    return (is_equality_comparable<std::tuple_element_t<Index, Type>>::value && ...);
 }
 
 template<typename>
-[[nodiscard]] constexpr bool maybe_equality_comparable(char) {
-    return false;
-}
-
-template<typename Type>
-[[nodiscard]] constexpr auto maybe_equality_comparable(int) -> decltype(std::declval<Type>() == std::declval<Type>()) {
+[[nodiscard]] constexpr bool maybe_equality_comparable(choice_t<0>) {
     return true;
 }
 
 template<typename Type>
-[[nodiscard]] constexpr bool dispatch_is_equality_comparable() {
-    // NOLINTBEGIN(modernize-use-transparent-functors)
-    if constexpr(std::is_array_v<Type>) {
-        return false;
-    } else if constexpr(is_complete_v<std::tuple_size<std::remove_cv_t<Type>>>) {
-        if constexpr(has_tuple_size_value<Type>::value) {
-            return maybe_equality_comparable<Type>(0) && unpack_maybe_equality_comparable<Type>(std::make_index_sequence<std::tuple_size<Type>::value>{});
-        } else {
-            return maybe_equality_comparable<Type>(0);
-        }
-    } else if constexpr(has_value_type<Type>::value) {
-        if constexpr(is_iterator_v<Type> || std::is_same_v<typename Type::value_type, Type> || dispatch_is_equality_comparable<typename Type::value_type>()) {
-            return maybe_equality_comparable<Type>(0);
-        } else {
-            return false;
-        }
+[[nodiscard]] constexpr auto maybe_equality_comparable(choice_t<1>) -> decltype(std::declval<typename Type::value_type>(), bool{}) {
+    if constexpr(is_iterator_v<Type>) {
+        return true;
+    } else if constexpr(std::is_same_v<typename Type::value_type, Type>) {
+        return maybe_equality_comparable<Type>(choice<0>);
     } else {
-        return maybe_equality_comparable<Type>(0);
+        return is_equality_comparable<typename Type::value_type>::value;
+    }
+}
+
+template<typename Type>
+[[nodiscard]] constexpr std::enable_if_t<is_complete_v<std::tuple_size<std::remove_cv_t<Type>>>, bool> maybe_equality_comparable(choice_t<2>) {
+    if constexpr(has_tuple_size_value<Type>::value) {
+        return unpack_maybe_equality_comparable<Type>(std::make_index_sequence<std::tuple_size<Type>::value>{});
+    } else {
+        return maybe_equality_comparable<Type>(choice<1>);
     }
-    // NOLINTEND(modernize-use-transparent-functors)
 }
 
 } // namespace internal
-/*! @endcond */
 
 /**
- * @brief Provides the member constant `value` to true if a given type is
- * equality comparable, false otherwise.
- * @tparam Type The type to test.
+ * Internal details not to be documented.
+ * @endcond
  */
-template<typename Type>
-struct is_equality_comparable: std::bool_constant<internal::dispatch_is_equality_comparable<Type>()> {};
 
 /*! @copydoc is_equality_comparable */
 template<typename Type>
-struct is_equality_comparable<const Type>: is_equality_comparable<Type> {};
+struct is_equality_comparable<Type, std::void_t<decltype(std::declval<Type>() == std::declval<Type>())>>
+    : std::bool_constant<internal::maybe_equality_comparable<Type>(choice<2>)> {};
+
+/*! @copydoc is_equality_comparable */
+template<typename Type, auto N>
+struct is_equality_comparable<Type[N]>: std::false_type {};
 
 /**
  * @brief Helper variable template.
@@ -870,11 +872,11 @@ template<typename Member>
 using member_class_t = typename member_class<Member>::type;
 
 /**
- * @brief Extracts the n-th argument of a _callable_ type.
+ * @brief Extracts the n-th argument of a given function or member function.
  * @tparam Index The index of the argument to extract.
- * @tparam Candidate A valid _callable_ type.
+ * @tparam Candidate A valid function, member function or data member.
  */
-template<std::size_t Index, typename Candidate>
+template<std::size_t Index, auto Candidate>
 class nth_argument {
     template<typename Ret, typename... Args>
     static constexpr type_list<Args...> pick_up(Ret (*)(Args...));
@@ -888,20 +890,17 @@ class nth_argument {
     template<typename Type, typename Class>
     static constexpr type_list<Type> pick_up(Type Class ::*);
 
-    template<typename Type>
-    static constexpr decltype(pick_up(&Type::operator())) pick_up(Type &&);
-
 public:
-    /*! @brief N-th argument of the _callable_ type. */
-    using type = type_list_element_t<Index, decltype(pick_up(std::declval<Candidate>()))>;
+    /*! @brief N-th argument of the given function or member function. */
+    using type = type_list_element_t<Index, decltype(pick_up(Candidate))>;
 };
 
 /**
  * @brief Helper type.
  * @tparam Index The index of the argument to extract.
- * @tparam Candidate A valid function, member function or data member type.
+ * @tparam Candidate A valid function, member function or data member.
  */
-template<std::size_t Index, typename Candidate>
+template<std::size_t Index, auto Candidate>
 using nth_argument_t = typename nth_argument<Index, Candidate>::type;
 
 } // namespace entt

src/entt/entity/component.hpp

@@ -8,7 +8,11 @@
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 template<typename Type, typename = void>
@@ -28,25 +32,26 @@ template<>
 struct page_size<void>: std::integral_constant<std::size_t, 0u> {};
 
 template<typename Type>
-struct page_size<Type, std::void_t<decltype(Type::page_size)>>
+struct page_size<Type, std::enable_if_t<std::is_convertible_v<decltype(Type::page_size), std::size_t>>>
     : std::integral_constant<std::size_t, Type::page_size> {};
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /**
  * @brief Common way to access various properties of components.
- * @tparam Type Element type.
- * @tparam Entity A valid entity type.
+ * @tparam Type Type of component.
  */
-template<typename Type, typename Entity, typename>
+template<typename Type, typename = void>
 struct component_traits {
     static_assert(std::is_same_v<std::decay_t<Type>, Type>, "Unsupported type");
 
-    /*! @brief Element type. */
-    using element_type = Type;
-    /*! @brief Underlying entity identifier. */
-    using entity_type = Entity;
+    /*! @brief Component type. */
+    using type = Type;
 
     /*! @brief Pointer stability, default is `false`. */
     static constexpr bool in_place_delete = internal::in_place_delete<Type>::value;

src/entt/entity/entity.hpp

@@ -5,14 +5,23 @@
 #include <cstdint>
 #include <type_traits>
 #include "../config/config.h"
-#include "../core/bit.hpp"
 #include "fwd.hpp"
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
+// waiting for C++20 (and std::popcount)
+template<typename Type>
+static constexpr int popcount(Type value) noexcept {
+    return value ? (int(value & 1) + popcount(value >> 1)) : 0;
+}
+
 template<typename, typename = void>
 struct entt_traits;
 
@@ -51,7 +60,11 @@ struct entt_traits<std::uint64_t> {
 };
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /**
  * @brief Common basic entity traits implementation.
@@ -59,10 +72,10 @@ struct entt_traits<std::uint64_t> {
  */
 template<typename Traits>
 class basic_entt_traits {
-    static constexpr auto length = popcount(Traits::entity_mask);
+    static constexpr auto length = internal::popcount(Traits::entity_mask);
 
-    static_assert(Traits::entity_mask && ((Traits::entity_mask & (Traits::entity_mask + 1)) == 0), "Invalid entity mask");
-    static_assert((Traits::version_mask & (Traits::version_mask + 1)) == 0, "Invalid version mask");
+    static_assert(Traits::entity_mask && ((typename Traits::entity_type{1} << length) == (Traits::entity_mask + 1)), "Invalid entity mask");
+    static_assert((typename Traits::entity_type{1} << internal::popcount(Traits::version_mask)) == (Traits::version_mask + 1), "Invalid version mask");
 
 public:
     /*! @brief Value type. */
@@ -101,11 +114,7 @@ public:
      * @return The integral representation of the version part.
      */
     [[nodiscard]] static constexpr version_type to_version(const value_type value) noexcept {
-        if constexpr(Traits::version_mask == 0u) {
-            return version_type{};
-        } else {
-            return (static_cast<version_type>(to_integral(value) >> length) & version_mask);
-        }
+        return static_cast<version_type>(to_integral(value) >> length);
     }
 
     /**
@@ -115,7 +124,7 @@ public:
      */
     [[nodiscard]] static constexpr value_type next(const value_type value) noexcept {
         const auto vers = to_version(value) + 1;
-        return construct(to_integral(value), static_cast<version_type>(vers + (vers == version_mask)));
+        return construct(to_entity(value), static_cast<version_type>(vers + (vers == version_mask)));
     }
 
     /**
@@ -129,11 +138,7 @@ public:
      * @return A properly constructed identifier.
      */
     [[nodiscard]] static constexpr value_type construct(const entity_type entity, const version_type version) noexcept {
-        if constexpr(Traits::version_mask == 0u) {
-            return value_type{entity & entity_mask};
-        } else {
-            return value_type{(entity & entity_mask) | (static_cast<entity_type>(version & version_mask) << length)};
-        }
+        return value_type{(entity & entity_mask) | (static_cast<entity_type>(version) << length)};
     }
 
     /**
@@ -147,11 +152,8 @@ public:
      * @return A properly constructed identifier.
      */
     [[nodiscard]] static constexpr value_type combine(const entity_type lhs, const entity_type rhs) noexcept {
-        if constexpr(Traits::version_mask == 0u) {
-            return value_type{lhs & entity_mask};
-        } else {
-            return value_type{(lhs & entity_mask) | (rhs & (version_mask << length))};
-        }
+        constexpr auto mask = (version_mask << length);
+        return value_type{(lhs & entity_mask) | (rhs & mask)};
     }
 };
 
@@ -168,10 +170,8 @@ struct entt_traits: basic_entt_traits<internal::entt_traits<Type>> {
 };
 
 /**
- * @brief Converts an entity to its underlying type.
+ * @copydoc entt_traits<Entity>::to_integral
  * @tparam Entity The value type.
- * @param value The value to convert.
- * @return The integral representation of the given value.
  */
 template<typename Entity>
 [[nodiscard]] constexpr typename entt_traits<Entity>::entity_type to_integral(const Entity value) noexcept {
@@ -179,10 +179,8 @@ template<typename Entity>
 }
 
 /**
- * @brief Returns the entity part once converted to the underlying type.
+ * @copydoc entt_traits<Entity>::to_entity
  * @tparam Entity The value type.
- * @param value The value to convert.
- * @return The integral representation of the entity part.
  */
 template<typename Entity>
 [[nodiscard]] constexpr typename entt_traits<Entity>::entity_type to_entity(const Entity value) noexcept {
@@ -190,10 +188,8 @@ template<typename Entity>
 }
 
 /**
- * @brief Returns the version part once converted to the underlying type.
+ * @copydoc entt_traits<Entity>::to_version
  * @tparam Entity The value type.
- * @param value The value to convert.
- * @return The integral representation of the version part.
  */
 template<typename Entity>
 [[nodiscard]] constexpr typename entt_traits<Entity>::version_type to_version(const Entity value) noexcept {
@@ -259,25 +255,25 @@ struct null_t {
 /**
  * @brief Compares a null object and an identifier of any type.
  * @tparam Entity Type of identifier.
- * @param lhs Identifier with which to compare.
- * @param rhs A null object yet to be converted.
+ * @param entity Identifier with which to compare.
+ * @param other A null object yet to be converted.
  * @return False if the two elements differ, true otherwise.
  */
 template<typename Entity>
-[[nodiscard]] constexpr bool operator==(const Entity lhs, const null_t rhs) noexcept {
-    return rhs.operator==(lhs);
+[[nodiscard]] constexpr bool operator==(const Entity entity, const null_t other) noexcept {
+    return other.operator==(entity);
 }
 
 /**
  * @brief Compares a null object and an identifier of any type.
  * @tparam Entity Type of identifier.
- * @param lhs Identifier with which to compare.
- * @param rhs A null object yet to be converted.
+ * @param entity Identifier with which to compare.
+ * @param other A null object yet to be converted.
  * @return True if the two elements differ, false otherwise.
  */
 template<typename Entity>
-[[nodiscard]] constexpr bool operator!=(const Entity lhs, const null_t rhs) noexcept {
-    return !(rhs == lhs);
+[[nodiscard]] constexpr bool operator!=(const Entity entity, const null_t other) noexcept {
+    return !(other == entity);
 }
 
 /*! @brief Tombstone object for all identifiers.  */
@@ -321,12 +317,7 @@ struct tombstone_t {
     template<typename Entity>
     [[nodiscard]] constexpr bool operator==(const Entity entity) const noexcept {
         using traits_type = entt_traits<Entity>;
-
-        if constexpr(traits_type::version_mask == 0u) {
-            return false;
-        } else {
-            return (traits_type::to_version(entity) == traits_type::to_version(*this));
-        }
+        return traits_type::to_version(entity) == traits_type::to_version(*this);
     }
 
     /**
@@ -344,25 +335,25 @@ struct tombstone_t {
 /**
  * @brief Compares a tombstone object and an identifier of any type.
  * @tparam Entity Type of identifier.
- * @param lhs Identifier with which to compare.
- * @param rhs A tombstone object yet to be converted.
+ * @param entity Identifier with which to compare.
+ * @param other A tombstone object yet to be converted.
  * @return False if the two elements differ, true otherwise.
  */
 template<typename Entity>
-[[nodiscard]] constexpr bool operator==(const Entity lhs, const tombstone_t rhs) noexcept {
-    return rhs.operator==(lhs);
+[[nodiscard]] constexpr bool operator==(const Entity entity, const tombstone_t other) noexcept {
+    return other.operator==(entity);
 }
 
 /**
  * @brief Compares a tombstone object and an identifier of any type.
  * @tparam Entity Type of identifier.
- * @param lhs Identifier with which to compare.
- * @param rhs A tombstone object yet to be converted.
+ * @param entity Identifier with which to compare.
+ * @param other A tombstone object yet to be converted.
  * @return True if the two elements differ, false otherwise.
  */
 template<typename Entity>
-[[nodiscard]] constexpr bool operator!=(const Entity lhs, const tombstone_t rhs) noexcept {
-    return !(rhs == lhs);
+[[nodiscard]] constexpr bool operator!=(const Entity entity, const tombstone_t other) noexcept {
+    return !(other == entity);
 }
 
 /**

src/entt/entity/fwd.hpp

@@ -4,7 +4,6 @@
 #include <cstdint>
 #include <memory>
 #include <type_traits>
-#include "../config/config.h"
 #include "../core/fwd.hpp"
 #include "../core/type_traits.hpp"
 
@@ -18,27 +17,55 @@ enum class deletion_policy : std::uint8_t {
     /*! @brief Swap-and-pop deletion policy. */
     swap_and_pop = 0u,
     /*! @brief In-place deletion policy. */
-    in_place = 1u,
-    /*! @brief Swap-only deletion policy. */
-    swap_only = 2u,
-    /*! @brief Unspecified deletion policy. */
-    unspecified = swap_and_pop
+    in_place = 1u
 };
 
-template<typename Type, typename Entity = entity, typename = void>
-struct component_traits;
-
 template<typename Entity = entity, typename = std::allocator<Entity>>
 class basic_sparse_set;
 
 template<typename Type, typename = entity, typename = std::allocator<Type>, typename = void>
 class basic_storage;
 
-template<typename, typename>
-class basic_sigh_mixin;
+template<typename Type>
+class sigh_mixin;
 
-template<typename, typename>
-class basic_reactive_mixin;
+/**
+ * @brief Provides a common way to define storage types.
+ * @tparam Type Storage value type.
+ * @tparam Entity A valid entity type.
+ * @tparam Allocator Type of allocator used to manage memory and elements.
+ */
+template<typename Type, typename Entity = entity, typename Allocator = std::allocator<Type>, typename = void>
+struct storage_type {
+    /*! @brief Type-to-storage conversion result. */
+    using type = sigh_mixin<basic_storage<Type, Entity, Allocator>>;
+};
+
+/**
+ * @brief Helper type.
+ * @tparam Args Arguments to forward.
+ */
+template<typename... Args>
+using storage_type_t = typename storage_type<Args...>::type;
+
+/**
+ * Type-to-storage conversion utility that preserves constness.
+ * @tparam Type Storage value type, eventually const.
+ * @tparam Entity A valid entity type.
+ * @tparam Allocator Type of allocator used to manage memory and elements.
+ */
+template<typename Type, typename Entity = entity, typename Allocator = std::allocator<std::remove_const_t<Type>>>
+struct storage_for {
+    /*! @brief Type-to-storage conversion result. */
+    using type = constness_as_t<storage_type_t<std::remove_const_t<Type>, Entity, Allocator>, Type>;
+};
+
+/**
+ * @brief Helper type.
+ * @tparam Args Arguments to forward.
+ */
+template<typename... Args>
+using storage_for_t = typename storage_for<Args...>::type;
 
 template<typename Entity = entity, typename = std::allocator<Entity>>
 class basic_registry;
@@ -52,11 +79,14 @@ class basic_runtime_view;
 template<typename, typename, typename>
 class basic_group;
 
+template<typename, typename Mask = std::uint32_t, typename = std::allocator<Mask>>
+class basic_observer;
+
 template<typename>
 class basic_organizer;
 
 template<typename, typename...>
-class basic_handle;
+struct basic_handle;
 
 template<typename>
 class basic_snapshot;
@@ -67,71 +97,6 @@ class basic_snapshot_loader;
 template<typename>
 class basic_continuous_loader;
 
-/*! @brief Alias declaration for the most common use case. */
-using sparse_set = basic_sparse_set<>;
-
-/**
- * @brief Alias declaration for the most common use case.
- * @tparam Type Element type.
- */
-template<typename Type>
-using storage = basic_storage<Type>;
-
-/**
- * @brief Alias declaration for the most common use case.
- * @tparam Type Underlying storage type.
- */
-template<typename Type>
-using sigh_mixin = basic_sigh_mixin<Type, basic_registry<typename Type::entity_type, typename Type::base_type::allocator_type>>;
-
-/**
- * @brief Alias declaration for the most common use case.
- * @tparam Type Underlying storage type.
- */
-template<typename Type>
-using reactive_mixin = basic_reactive_mixin<Type, basic_registry<typename Type::entity_type, typename Type::base_type::allocator_type>>;
-
-/*! @brief Alias declaration for the most common use case. */
-using registry = basic_registry<>;
-
-/*! @brief Alias declaration for the most common use case. */
-using organizer = basic_organizer<registry>;
-
-/*! @brief Alias declaration for the most common use case. */
-using handle = basic_handle<registry>;
-
-/*! @brief Alias declaration for the most common use case. */
-using const_handle = basic_handle<const registry>;
-
-/**
- * @brief Alias declaration for the most common use case.
- * @tparam Args Other template parameters.
- */
-template<typename... Args>
-using handle_view = basic_handle<registry, Args...>;
-
-/**
- * @brief Alias declaration for the most common use case.
- * @tparam Args Other template parameters.
- */
-template<typename... Args>
-using const_handle_view = basic_handle<const registry, Args...>;
-
-/*! @brief Alias declaration for the most common use case. */
-using snapshot = basic_snapshot<registry>;
-
-/*! @brief Alias declaration for the most common use case. */
-using snapshot_loader = basic_snapshot_loader<registry>;
-
-/*! @brief Alias declaration for the most common use case. */
-using continuous_loader = basic_continuous_loader<registry>;
-
-/*! @brief Alias declaration for the most common use case. */
-using runtime_view = basic_runtime_view<sparse_set>;
-
-/*! @brief Alias declaration for the most common use case. */
-using const_runtime_view = basic_runtime_view<const sparse_set>;
-
 /**
  * @brief Alias for exclusion lists.
  * @tparam Type List of types.
@@ -139,7 +104,7 @@ using const_runtime_view = basic_runtime_view<const sparse_set>;
 template<typename... Type>
 struct exclude_t final: type_list<Type...> {
     /*! @brief Default constructor. */
-    explicit constexpr exclude_t() = default;
+    explicit constexpr exclude_t() {}
 };
 
 /**
@@ -150,34 +115,34 @@ template<typename... Type>
 inline constexpr exclude_t<Type...> exclude{};
 
 /**
- * @brief Alias for lists of observed elements.
+ * @brief Alias for lists of observed components.
  * @tparam Type List of types.
  */
 template<typename... Type>
 struct get_t final: type_list<Type...> {
     /*! @brief Default constructor. */
-    explicit constexpr get_t() = default;
+    explicit constexpr get_t() {}
 };
 
 /**
- * @brief Variable template for lists of observed elements.
+ * @brief Variable template for lists of observed components.
  * @tparam Type List of types.
  */
 template<typename... Type>
 inline constexpr get_t<Type...> get{};
 
 /**
- * @brief Alias for lists of owned elements.
+ * @brief Alias for lists of owned components.
  * @tparam Type List of types.
  */
 template<typename... Type>
 struct owned_t final: type_list<Type...> {
     /*! @brief Default constructor. */
-    explicit constexpr owned_t() = default;
+    explicit constexpr owned_t() {}
 };
 
 /**
- * @brief Variable template for lists of owned elements.
+ * @brief Variable template for lists of owned components.
  * @tparam Type List of types.
  */
 template<typename... Type>
@@ -216,57 +181,53 @@ struct type_list_transform<owned_t<Type...>, Op> {
     using type = owned_t<typename Op<Type>::type...>;
 };
 
+/*! @brief Alias declaration for the most common use case. */
+using sparse_set = basic_sparse_set<>;
+
 /**
- * @brief Provides a common way to define storage types.
- * @tparam Type Storage value type.
- * @tparam Entity A valid entity type.
- * @tparam Allocator Type of allocator used to manage memory and elements.
+ * @brief Alias declaration for the most common use case.
+ * @tparam Type Type of objects assigned to the entities.
  */
-template<typename Type, typename Entity = entity, typename Allocator = std::allocator<Type>, typename = void>
-struct storage_type {
-    /*! @brief Type-to-storage conversion result. */
-    using type = ENTT_STORAGE(sigh_mixin, basic_storage<Type, Entity, Allocator>);
-};
+template<typename Type>
+using storage = basic_storage<Type>;
 
-/*! @brief Empty value type for reactive storage types. */
-struct reactive final {};
+/*! @brief Alias declaration for the most common use case. */
+using registry = basic_registry<>;
+
+/*! @brief Alias declaration for the most common use case. */
+using observer = basic_observer<registry>;
+
+/*! @brief Alias declaration for the most common use case. */
+using organizer = basic_organizer<registry>;
+
+/*! @brief Alias declaration for the most common use case. */
+using handle = basic_handle<registry>;
+
+/*! @brief Alias declaration for the most common use case. */
+using const_handle = basic_handle<const registry>;
 
 /**
- * @ brief Partial specialization for reactive storage types.
- * @tparam Entity A valid entity type.
- * @tparam Allocator Type of allocator used to manage memory and elements.
- */
-template<typename Entity, typename Allocator>
-struct storage_type<reactive, Entity, Allocator> {
-    /*! @brief Type-to-storage conversion result. */
-    using type = ENTT_STORAGE(reactive_mixin, basic_storage<reactive, Entity, Allocator>);
-};
-
-/**
- * @brief Helper type.
- * @tparam Args Arguments to forward.
+ * @brief Alias declaration for the most common use case.
+ * @tparam Args Other template parameters.
  */
 template<typename... Args>
-using storage_type_t = typename storage_type<Args...>::type;
+using handle_view = basic_handle<registry, Args...>;
 
 /**
- * Type-to-storage conversion utility that preserves constness.
- * @tparam Type Storage value type, eventually const.
- * @tparam Entity A valid entity type.
- * @tparam Allocator Type of allocator used to manage memory and elements.
- */
-template<typename Type, typename Entity = entity, typename Allocator = std::allocator<std::remove_const_t<Type>>>
-struct storage_for {
-    /*! @brief Type-to-storage conversion result. */
-    using type = constness_as_t<storage_type_t<std::remove_const_t<Type>, Entity, Allocator>, Type>;
-};
-
-/**
- * @brief Helper type.
- * @tparam Args Arguments to forward.
+ * @brief Alias declaration for the most common use case.
+ * @tparam Args Other template parameters.
  */
 template<typename... Args>
-using storage_for_t = typename storage_for<Args...>::type;
+using const_handle_view = basic_handle<const registry, Args...>;
+
+/*! @brief Alias declaration for the most common use case. */
+using snapshot = basic_snapshot<registry>;
+
+/*! @brief Alias declaration for the most common use case. */
+using snapshot_loader = basic_snapshot_loader<registry>;
+
+/*! @brief Alias declaration for the most common use case. */
+using continuous_loader = basic_continuous_loader<registry>;
 
 /**
  * @brief Alias declaration for the most common use case.
@@ -276,13 +237,19 @@ using storage_for_t = typename storage_for<Args...>::type;
 template<typename Get, typename Exclude = exclude_t<>>
 using view = basic_view<type_list_transform_t<Get, storage_for>, type_list_transform_t<Exclude, storage_for>>;
 
+/*! @brief Alias declaration for the most common use case. */
+using runtime_view = basic_runtime_view<sparse_set>;
+
+/*! @brief Alias declaration for the most common use case. */
+using const_runtime_view = basic_runtime_view<const sparse_set>;
+
 /**
  * @brief Alias declaration for the most common use case.
  * @tparam Owned Types of storage _owned_ by the group.
  * @tparam Get Types of storage _observed_ by the group.
  * @tparam Exclude Types of storage used to filter the group.
  */
-template<typename Owned, typename Get = get_t<>, typename Exclude = exclude_t<>>
+template<typename Owned, typename Get, typename Exclude>
 using group = basic_group<type_list_transform_t<Owned, storage_for>, type_list_transform_t<Get, storage_for>, type_list_transform_t<Exclude, storage_for>>;
 
 } // namespace entt

src/entt/entity/group.hpp

@@ -1,24 +1,26 @@
 #ifndef ENTT_ENTITY_GROUP_HPP
 #define ENTT_ENTITY_GROUP_HPP
 
-#include <array>
-#include <cstddef>
-#include <iterator>
 #include <tuple>
 #include <type_traits>
 #include <utility>
 #include "../config/config.h"
-#include "../core/algorithm.hpp"
 #include "../core/fwd.hpp"
 #include "../core/iterator.hpp"
 #include "../core/type_info.hpp"
 #include "../core/type_traits.hpp"
 #include "entity.hpp"
 #include "fwd.hpp"
+#include "sparse_set.hpp"
+#include "storage.hpp"
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 template<typename, typename, typename>
@@ -27,8 +29,8 @@ class extended_group_iterator;
 template<typename It, typename... Owned, typename... Get>
 class extended_group_iterator<It, owned_t<Owned...>, get_t<Get...>> {
     template<typename Type>
-    [[nodiscard]] auto index_to_element([[maybe_unused]] Type &cpool) const {
-        if constexpr(std::is_void_v<typename Type::value_type>) {
+    auto index_to_element([[maybe_unused]] Type &cpool) const {
+        if constexpr(Type::traits_type::page_size == 0u) {
             return std::make_tuple();
         } else {
             return std::forward_as_tuple(cpool.rbegin()[it.index()]);
@@ -37,27 +39,26 @@ class extended_group_iterator<It, owned_t<Owned...>, get_t<Get...>> {
 
 public:
     using iterator_type = It;
+    using difference_type = std::ptrdiff_t;
     using value_type = decltype(std::tuple_cat(std::make_tuple(*std::declval<It>()), std::declval<Owned>().get_as_tuple({})..., std::declval<Get>().get_as_tuple({})...));
     using pointer = input_iterator_pointer<value_type>;
     using reference = value_type;
-    using difference_type = std::ptrdiff_t;
     using iterator_category = std::input_iterator_tag;
-    using iterator_concept = std::forward_iterator_tag;
 
     constexpr extended_group_iterator()
         : it{},
           pools{} {}
 
-    extended_group_iterator(iterator_type from, std::tuple<Owned *..., Get *...> cpools)
+    extended_group_iterator(It from, const std::tuple<Owned *..., Get *...> &cpools)
         : it{from},
-          pools{std::move(cpools)} {}
+          pools{cpools} {}
 
     extended_group_iterator &operator++() noexcept {
         return ++it, *this;
     }
 
     extended_group_iterator operator++(int) noexcept {
-        const extended_group_iterator orig = *this;
+        extended_group_iterator orig = *this;
         return ++(*this), orig;
     }
 
@@ -94,93 +95,100 @@ template<typename... Lhs, typename... Rhs>
 struct group_descriptor {
     using size_type = std::size_t;
     virtual ~group_descriptor() = default;
-    [[nodiscard]] virtual bool owned(const id_type) const noexcept {
-        return false;
+    virtual size_type owned(const id_type *, const size_type) const noexcept {
+        return 0u;
     }
 };
 
-template<typename Type, std::size_t Owned, std::size_t Get, std::size_t Exclude>
-class group_handler final: public group_descriptor {
-    using entity_type = typename Type::entity_type;
+template<typename, typename, typename>
+class group_handler;
+
+template<typename... Owned, typename... Get, typename... Exclude>
+class group_handler<owned_t<Owned...>, get_t<Get...>, exclude_t<Exclude...>> final: public group_descriptor {
+    // nasty workaround for an issue with the toolset v141 that doesn't accept a fold expression here
+    static_assert(!std::disjunction_v<std::bool_constant<Owned::traits_type::in_place_delete>...>, "Groups do not support in-place delete");
+    static_assert(!std::disjunction_v<std::is_const<Owned>..., std::is_const<Get>..., std::is_const<Exclude>...>, "Const storage type not allowed");
+
+    using base_type = std::common_type_t<typename Owned::base_type..., typename Get::base_type..., typename Exclude::base_type...>;
+    using entity_type = typename base_type::entity_type;
 
     void swap_elements(const std::size_t pos, const entity_type entt) {
-        for(size_type next{}; next < Owned; ++next) {
-            pools[next]->swap_elements((*pools[next])[pos], entt);
-        }
+        std::apply([pos, entt](auto *...cpool) { (cpool->swap_elements(cpool->data()[pos], entt), ...); }, pools);
     }
 
     void push_on_construct(const entity_type entt) {
-        if(std::apply([entt, pos = len](auto *cpool, auto *...other) { return cpool->contains(entt) && !(cpool->index(entt) < pos) && (other->contains(entt) && ...); }, pools)
+        if(std::apply([entt, len = len](auto *cpool, auto *...other) { return cpool->contains(entt) && !(cpool->index(entt) < len) && (other->contains(entt) && ...); }, pools)
            && std::apply([entt](auto *...cpool) { return (!cpool->contains(entt) && ...); }, filter)) {
             swap_elements(len++, entt);
         }
     }
 
     void push_on_destroy(const entity_type entt) {
-        if(std::apply([entt, pos = len](auto *cpool, auto *...other) { return cpool->contains(entt) && !(cpool->index(entt) < pos) && (other->contains(entt) && ...); }, pools)
+        if(std::apply([entt, len = len](auto *cpool, auto *...other) { return cpool->contains(entt) && !(cpool->index(entt) < len) && (other->contains(entt) && ...); }, pools)
            && std::apply([entt](auto *...cpool) { return (0u + ... + cpool->contains(entt)) == 1u; }, filter)) {
             swap_elements(len++, entt);
         }
     }
 
     void remove_if(const entity_type entt) {
-        if(pools[0u]->contains(entt) && (pools[0u]->index(entt) < len)) {
+        if(std::get<0>(pools)->contains(entt) && (std::get<0>(pools)->index(entt) < len)) {
             swap_elements(--len, entt);
         }
     }
 
-    void common_setup() {
+public:
+    using size_type = typename base_type::size_type;
+
+    group_handler(Owned &...opool, Get &...gpool, Exclude &...epool)
+        : pools{&opool..., &gpool...},
+          filter{&epool...},
+          len{} {
+        std::apply([this](auto *...cpool) { ((cpool->on_construct().template connect<&group_handler::push_on_construct>(*this), cpool->on_destroy().template connect<&group_handler::remove_if>(*this)), ...); }, pools);
+        std::apply([this](auto *...cpool) { ((cpool->on_construct().template connect<&group_handler::remove_if>(*this), cpool->on_destroy().template connect<&group_handler::push_on_destroy>(*this)), ...); }, filter);
+
         // we cannot iterate backwards because we want to leave behind valid entities in case of owned types
-        for(auto first = pools[0u]->rbegin(), last = first + static_cast<typename decltype(pools)::difference_type>(pools[0u]->size()); first != last; ++first) {
+        for(auto *first = std::get<0>(pools)->data(), *last = first + std::get<0>(pools)->size(); first != last; ++first) {
             push_on_construct(*first);
         }
     }
 
-public:
-    using common_type = Type;
-    using size_type = typename Type::size_type;
+    size_type owned(const id_type *elem, const size_type length) const noexcept final {
+        size_type cnt = 0u;
 
-    template<typename... OGType, typename... EType>
-    group_handler(std::tuple<OGType &...> ogpool, std::tuple<EType &...> epool)
-        : pools{std::apply([](auto &&...cpool) { return std::array<common_type *, (Owned + Get)>{&cpool...}; }, ogpool)},
-          filter{std::apply([](auto &&...cpool) { return std::array<common_type *, Exclude>{&cpool...}; }, epool)} {
-        std::apply([this](auto &...cpool) { ((cpool.on_construct().template connect<&group_handler::push_on_construct>(*this), cpool.on_destroy().template connect<&group_handler::remove_if>(*this)), ...); }, ogpool);
-        std::apply([this](auto &...cpool) { ((cpool.on_construct().template connect<&group_handler::remove_if>(*this), cpool.on_destroy().template connect<&group_handler::push_on_destroy>(*this)), ...); }, epool);
-        common_setup();
-    }
-
-    [[nodiscard]] bool owned(const id_type hash) const noexcept override {
-        for(size_type pos{}; pos < Owned; ++pos) {
-            if(pools[pos]->type().hash() == hash) {
-                return true;
-            }
+        for(auto pos = 0u; pos < length; ++pos) {
+            cnt += ((elem[pos] == entt::type_hash<typename Owned::value_type>::value()) || ...);
         }
 
-        return false;
+        return cnt;
     }
 
     [[nodiscard]] size_type length() const noexcept {
         return len;
     }
 
-    template<std::size_t Index>
-    [[nodiscard]] common_type *storage() const noexcept {
-        if constexpr(Index < (Owned + Get)) {
-            return pools[Index];
-        } else {
-            return filter[Index - (Owned + Get)];
-        }
+    template<typename Type>
+    Type pools_as() const noexcept {
+        return pools;
+    }
+
+    template<typename Type>
+    Type filter_as() const noexcept {
+        return filter;
     }
 
 private:
-    std::array<common_type *, (Owned + Get)> pools;
-    std::array<common_type *, Exclude> filter;
-    std::size_t len{};
+    std::tuple<Owned *..., Get *...> pools;
+    std::tuple<Exclude *...> filter;
+    std::size_t len;
 };
 
-template<typename Type, std::size_t Get, std::size_t Exclude>
-class group_handler<Type, 0u, Get, Exclude> final: public group_descriptor {
-    using entity_type = typename Type::entity_type;
+template<typename... Get, typename... Exclude>
+class group_handler<owned_t<>, get_t<Get...>, exclude_t<Exclude...>> final: public group_descriptor {
+    // nasty workaround for an issue with the toolset v141 that doesn't accept a fold expression here
+    static_assert(!std::disjunction_v<std::is_const<Get>..., std::is_const<Exclude>...>, "Const storage type not allowed");
+
+    using base_type = std::common_type_t<typename Get::base_type..., typename Exclude::base_type...>;
+    using entity_type = typename base_type::entity_type;
 
     void push_on_construct(const entity_type entt) {
         if(!elem.contains(entt)
@@ -202,50 +210,52 @@ class group_handler<Type, 0u, Get, Exclude> final: public group_descriptor {
         elem.remove(entt);
     }
 
-    void common_setup() {
-        for(const auto entity: *pools[0u]) {
+public:
+    using common_type = base_type;
+
+    template<typename Alloc>
+    group_handler(const Alloc &alloc, Get &...gpool, Exclude &...epool)
+        : pools{&gpool...},
+          filter{&epool...},
+          elem{alloc} {
+        std::apply([this](auto *...cpool) { ((cpool->on_construct().template connect<&group_handler::push_on_construct>(*this), cpool->on_destroy().template connect<&group_handler::remove_if>(*this)), ...); }, pools);
+        std::apply([this](auto *...cpool) { ((cpool->on_construct().template connect<&group_handler::remove_if>(*this), cpool->on_destroy().template connect<&group_handler::push_on_destroy>(*this)), ...); }, filter);
+
+        for(const auto entity: static_cast<base_type &>(*std::get<0>(pools))) {
             push_on_construct(entity);
         }
     }
 
-public:
-    using common_type = Type;
-
-    template<typename Allocator, typename... GType, typename... EType>
-    group_handler(const Allocator &allocator, std::tuple<GType &...> gpool, std::tuple<EType &...> epool)
-        : pools{std::apply([](auto &&...cpool) { return std::array<common_type *, Get>{&cpool...}; }, gpool)},
-          filter{std::apply([](auto &&...cpool) { return std::array<common_type *, Exclude>{&cpool...}; }, epool)},
-          elem{allocator} {
-        std::apply([this](auto &...cpool) { ((cpool.on_construct().template connect<&group_handler::push_on_construct>(*this), cpool.on_destroy().template connect<&group_handler::remove_if>(*this)), ...); }, gpool);
-        std::apply([this](auto &...cpool) { ((cpool.on_construct().template connect<&group_handler::remove_if>(*this), cpool.on_destroy().template connect<&group_handler::push_on_destroy>(*this)), ...); }, epool);
-        common_setup();
-    }
-
-    [[nodiscard]] common_type &handle() noexcept {
+    common_type &handle() noexcept {
         return elem;
     }
 
-    [[nodiscard]] const common_type &handle() const noexcept {
+    const common_type &handle() const noexcept {
         return elem;
     }
 
-    template<std::size_t Index>
-    [[nodiscard]] common_type *storage() const noexcept {
-        if constexpr(Index < Get) {
-            return pools[Index];
-        } else {
-            return filter[Index - Get];
-        }
+    template<typename Type>
+    Type pools_as() const noexcept {
+        return pools;
+    }
+
+    template<typename Type>
+    Type filter_as() const noexcept {
+        return filter;
     }
 
 private:
-    std::array<common_type *, Get> pools;
-    std::array<common_type *, Exclude> filter;
-    common_type elem;
+    std::tuple<Get *...> pools;
+    std::tuple<Exclude *...> filter;
+    base_type elem;
 };
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /**
  * @brief Group.
@@ -268,7 +278,7 @@ class basic_group;
  * Iterators aren't invalidated if:
  *
  * * New elements are added to the storage.
- * * The entity currently pointed is modified (for example, elements are added
+ * * The entity currently pointed is modified (for example, components are added
  *   or removed from it).
  * * The entity currently pointed is destroyed.
  *
@@ -284,12 +294,16 @@ class basic_group<owned_t<>, get_t<Get...>, exclude_t<Exclude...>> {
     using underlying_type = typename base_type::entity_type;
 
     template<typename Type>
-    static constexpr std::size_t index_of = type_list_index_v<std::remove_const_t<Type>, type_list<typename Get::element_type..., typename Exclude::element_type...>>;
+    static constexpr std::size_t index_of = type_list_index_v<std::remove_const_t<Type>, type_list<typename Get::value_type..., typename Exclude::value_type...>>;
 
-    template<std::size_t... Index>
-    [[nodiscard]] auto pools_for(std::index_sequence<Index...>) const noexcept {
+    auto pools() const noexcept {
         using return_type = std::tuple<Get *...>;
-        return descriptor ? return_type{static_cast<Get *>(descriptor->template storage<Index>())...} : return_type{};
+        return descriptor ? descriptor->template pools_as<return_type>() : return_type{};
+    }
+
+    auto filter() const noexcept {
+        using return_type = std::tuple<Exclude *...>;
+        return descriptor ? descriptor->template filter_as<return_type>() : return_type{};
     }
 
 public:
@@ -297,26 +311,16 @@ public:
     using entity_type = underlying_type;
     /*! @brief Unsigned integer type. */
     using size_type = std::size_t;
-    /*! @brief Signed integer type. */
-    using difference_type = std::ptrdiff_t;
     /*! @brief Common type among all storage types. */
     using common_type = base_type;
     /*! @brief Random access iterator type. */
     using iterator = typename common_type::iterator;
-    /*! @brief Reverse iterator type. */
+    /*! @brief Reversed iterator type. */
     using reverse_iterator = typename common_type::reverse_iterator;
     /*! @brief Iterable group type. */
     using iterable = iterable_adaptor<internal::extended_group_iterator<iterator, owned_t<>, get_t<Get...>>>;
     /*! @brief Group handler type. */
-    using handler = internal::group_handler<common_type, 0u, sizeof...(Get), sizeof...(Exclude)>;
-
-    /**
-     * @brief Group opaque identifier.
-     * @return Group opaque identifier.
-     */
-    static id_type group_id() noexcept {
-        return type_hash<basic_group<owned_t<>, get_t<std::remove_const_t<Get>...>, exclude_t<std::remove_const_t<Exclude>...>>>::value();
-    }
+    using handler = internal::group_handler<owned_t<>, get_t<std::remove_const_t<Get>...>, exclude_t<std::remove_const_t<Exclude>...>>;
 
     /*! @brief Default constructor to use to create empty, invalid groups. */
     basic_group() noexcept
@@ -338,9 +342,9 @@ public:
     }
 
     /**
-     * @brief Returns the storage for a given element type, if any.
-     * @tparam Type Type of element of which to return the storage.
-     * @return The storage for the given element type.
+     * @brief Returns the storage for a given component type, if any.
+     * @tparam Type Type of component of which to return the storage.
+     * @return The storage for the given component type.
      */
     template<typename Type>
     [[nodiscard]] auto *storage() const noexcept {
@@ -354,8 +358,13 @@ public:
      */
     template<std::size_t Index>
     [[nodiscard]] auto *storage() const noexcept {
-        using type = type_list_element_t<Index, type_list<Get..., Exclude...>>;
-        return *this ? static_cast<type *>(descriptor->template storage<Index>()) : nullptr;
+        constexpr auto offset = sizeof...(Get);
+
+        if constexpr(Index < offset) {
+            return std::get<Index>(pools());
+        } else {
+            return std::get<Index - offset>(filter());
+        }
     }
 
     /**
@@ -467,7 +476,7 @@ public:
      * @return The identifier that occupies the given position.
      */
     [[nodiscard]] entity_type operator[](const size_type pos) const {
-        return begin()[static_cast<difference_type>(pos)];
+        return begin()[pos];
     }
 
     /**
@@ -488,11 +497,16 @@ public:
     }
 
     /**
-     * @brief Returns the elements assigned to the given entity.
-     * @tparam Type Type of the element to get.
-     * @tparam Other Other types of elements to get.
+     * @brief Returns the components assigned to the given entity.
+     *
+     * @warning
+     * Attempting to use an entity that doesn't belong to the group results in
+     * undefined behavior.
+     *
+     * @tparam Type Type of the component to get.
+     * @tparam Other Other types of components to get.
      * @param entt A valid identifier.
-     * @return The elements assigned to the entity.
+     * @return The components assigned to the entity.
      */
     template<typename Type, typename... Other>
     [[nodiscard]] decltype(auto) get(const entity_type entt) const {
@@ -500,14 +514,19 @@ public:
     }
 
     /**
-     * @brief Returns the elements assigned to the given entity.
-     * @tparam Index Indexes of the elements to get.
+     * @brief Returns the components assigned to the given entity.
+     *
+     * @warning
+     * Attempting to use an entity that doesn't belong to the groups results in
+     * undefined behavior.
+     *
+     * @tparam Index Indexes of the components to get.
      * @param entt A valid identifier.
-     * @return The elements assigned to the entity.
+     * @return The components assigned to the entity.
      */
     template<std::size_t... Index>
     [[nodiscard]] decltype(auto) get(const entity_type entt) const {
-        const auto cpools = pools_for(std::index_sequence_for<Get...>{});
+        const auto cpools = pools();
 
         if constexpr(sizeof...(Index) == 0) {
             return std::apply([entt](auto *...curr) { return std::tuple_cat(curr->get_as_tuple(entt)...); }, cpools);
@@ -519,12 +538,12 @@ public:
     }
 
     /**
-     * @brief Iterates entities and elements and applies the given function
+     * @brief Iterates entities and components and applies the given function
      * object to them.
      *
      * The function object is invoked for each entity. It is provided with the
-     * entity itself and a set of references to non-empty elements. The
-     * _constness_ of the elements is as requested.<br/>
+     * entity itself and a set of references to non-empty components. The
+     * _constness_ of the components is as requested.<br/>
      * The signature of the function must be equivalent to one of the following
      * forms:
      *
@@ -555,8 +574,8 @@ public:
      * @brief Returns an iterable object to use to _visit_ a group.
      *
      * The iterable object returns tuples that contain the current entity and a
-     * set of references to its non-empty elements. The _constness_ of the
-     * elements is as requested.
+     * set of references to its non-empty components. The _constness_ of the
+     * components is as requested.
      *
      * @note
      * Empty types aren't explicitly instantiated and therefore they are never
@@ -565,7 +584,7 @@ public:
      * @return An iterable object to use to _visit_ the group.
      */
     [[nodiscard]] iterable each() const noexcept {
-        const auto cpools = pools_for(std::index_sequence_for<Get...>{});
+        const auto cpools = pools();
         return iterable{{begin(), cpools}, {end(), cpools}};
     }
 
@@ -593,8 +612,8 @@ public:
      * * An iterator past the last element of the range to sort.
      * * A comparison function to use to compare the elements.
      *
-     * @tparam Type Optional type of element to compare.
-     * @tparam Other Other optional types of elements to compare.
+     * @tparam Type Optional type of component to compare.
+     * @tparam Other Other optional types of components to compare.
      * @tparam Compare Type of comparison function object.
      * @tparam Sort Type of sort function object.
      * @tparam Args Types of arguments to forward to the sort function object.
@@ -612,7 +631,7 @@ public:
      *
      * @sa sort
      *
-     * @tparam Index Optional indexes of elements to compare.
+     * @tparam Index Optional indexes of components to compare.
      * @tparam Compare Type of comparison function object.
      * @tparam Sort Type of sort function object.
      * @tparam Args Types of arguments to forward to the sort function object.
@@ -627,7 +646,7 @@ public:
                 static_assert(std::is_invocable_v<Compare, const entity_type, const entity_type>, "Invalid comparison function");
                 descriptor->handle().sort(std::move(compare), std::move(algo), std::forward<Args>(args)...);
             } else {
-                auto comp = [&compare, cpools = pools_for(std::index_sequence_for<Get...>{})](const entity_type lhs, const entity_type rhs) {
+                auto comp = [&compare, cpools = pools()](const entity_type lhs, const entity_type rhs) {
                     if constexpr(sizeof...(Index) == 1) {
                         return compare((std::get<Index>(cpools)->get(lhs), ...), (std::get<Index>(cpools)->get(rhs), ...));
                     } else {
@@ -641,19 +660,16 @@ public:
     }
 
     /**
-     * @brief Sort entities according to their order in a range.
+     * @brief Sort the shared pool of entities according to a given storage.
      *
      * The shared pool of entities and thus its order is affected by the changes
      * to each and every pool that it tracks.
      *
-     * @tparam It Type of input iterator.
-     * @param first An iterator to the first element of the range of entities.
-     * @param last An iterator past the last element of the range of entities.
+     * @param other The storage to use to impose the order.
      */
-    template<typename It>
-    void sort_as(It first, It last) const {
+    void sort_as(const common_type &other) const {
         if(*this) {
-            descriptor->handle().sort_as(first, last);
+            descriptor->handle().sort_as(other);
         }
     }
 
@@ -669,7 +685,7 @@ private:
  *
  * * It's guaranteed that the entity list is tightly packed in memory for fast
  *   iterations.
- * * It's guaranteed that all elements in the owned storage are tightly packed
+ * * It's guaranteed that all components in the owned storage are tightly packed
  *   in memory for even faster iterations and to allow direct access.
  * * They stay true to the order of the owned storage and all instances have the
  *   same order in memory.
@@ -681,7 +697,7 @@ private:
  * Iterators aren't invalidated if:
  *
  * * New elements are added to the storage.
- * * The entity currently pointed is modified (for example, elements are added
+ * * The entity currently pointed is modified (for example, components are added
  *   or removed from it).
  * * The entity currently pointed is destroyed.
  *
@@ -694,18 +710,20 @@ private:
  */
 template<typename... Owned, typename... Get, typename... Exclude>
 class basic_group<owned_t<Owned...>, get_t<Get...>, exclude_t<Exclude...>> {
-    static_assert(((Owned::storage_policy != deletion_policy::in_place) && ...), "Groups do not support in-place delete");
-
     using base_type = std::common_type_t<typename Owned::base_type..., typename Get::base_type..., typename Exclude::base_type...>;
     using underlying_type = typename base_type::entity_type;
 
     template<typename Type>
-    static constexpr std::size_t index_of = type_list_index_v<std::remove_const_t<Type>, type_list<typename Owned::element_type..., typename Get::element_type..., typename Exclude::element_type...>>;
+    static constexpr std::size_t index_of = type_list_index_v<std::remove_const_t<Type>, type_list<typename Owned::value_type..., typename Get::value_type..., typename Exclude::value_type...>>;
 
-    template<std::size_t... Index, std::size_t... Other>
-    [[nodiscard]] auto pools_for(std::index_sequence<Index...>, std::index_sequence<Other...>) const noexcept {
+    auto pools() const noexcept {
         using return_type = std::tuple<Owned *..., Get *...>;
-        return descriptor ? return_type{static_cast<Owned *>(descriptor->template storage<Index>())..., static_cast<Get *>(descriptor->template storage<sizeof...(Owned) + Other>())...} : return_type{};
+        return descriptor ? descriptor->template pools_as<return_type>() : return_type{};
+    }
+
+    auto filter() const noexcept {
+        using return_type = std::tuple<Exclude *...>;
+        return descriptor ? descriptor->template filter_as<return_type>() : return_type{};
     }
 
 public:
@@ -713,26 +731,16 @@ public:
     using entity_type = underlying_type;
     /*! @brief Unsigned integer type. */
     using size_type = std::size_t;
-    /*! @brief Signed integer type. */
-    using difference_type = std::ptrdiff_t;
     /*! @brief Common type among all storage types. */
     using common_type = base_type;
     /*! @brief Random access iterator type. */
     using iterator = typename common_type::iterator;
-    /*! @brief Reverse iterator type. */
+    /*! @brief Reversed iterator type. */
     using reverse_iterator = typename common_type::reverse_iterator;
     /*! @brief Iterable group type. */
     using iterable = iterable_adaptor<internal::extended_group_iterator<iterator, owned_t<Owned...>, get_t<Get...>>>;
     /*! @brief Group handler type. */
-    using handler = internal::group_handler<common_type, sizeof...(Owned), sizeof...(Get), sizeof...(Exclude)>;
-
-    /**
-     * @brief Group opaque identifier.
-     * @return Group opaque identifier.
-     */
-    static id_type group_id() noexcept {
-        return type_hash<basic_group<owned_t<std::remove_const_t<Owned>...>, get_t<std::remove_const_t<Get>...>, exclude_t<std::remove_const_t<Exclude>...>>>::value();
-    }
+    using handler = internal::group_handler<owned_t<std::remove_const_t<Owned>...>, get_t<std::remove_const_t<Get>...>, exclude_t<std::remove_const_t<Exclude>...>>;
 
     /*! @brief Default constructor to use to create empty, invalid groups. */
     basic_group() noexcept
@@ -754,9 +762,9 @@ public:
     }
 
     /**
-     * @brief Returns the storage for a given element type, if any.
-     * @tparam Type Type of element of which to return the storage.
-     * @return The storage for the given element type.
+     * @brief Returns the storage for a given component type, if any.
+     * @tparam Type Type of component of which to return the storage.
+     * @return The storage for the given component type.
      */
     template<typename Type>
     [[nodiscard]] auto *storage() const noexcept {
@@ -770,8 +778,13 @@ public:
      */
     template<std::size_t Index>
     [[nodiscard]] auto *storage() const noexcept {
-        using type = type_list_element_t<Index, type_list<Owned..., Get..., Exclude...>>;
-        return *this ? static_cast<type *>(descriptor->template storage<Index>()) : nullptr;
+        constexpr auto offset = sizeof...(Owned) + sizeof...(Get);
+
+        if constexpr(Index < offset) {
+            return std::get<Index>(pools());
+        } else {
+            return std::get<Index - offset>(filter());
+        }
     }
 
     /**
@@ -798,7 +811,7 @@ public:
      * @return An iterator to the first entity of the group.
      */
     [[nodiscard]] iterator begin() const noexcept {
-        return *this ? (handle().end() - static_cast<difference_type>(descriptor->length())) : iterator{};
+        return *this ? (handle().end() - descriptor->length()) : iterator{};
     }
 
     /**
@@ -828,7 +841,7 @@ public:
      * reversed group.
      */
     [[nodiscard]] reverse_iterator rend() const noexcept {
-        return *this ? (handle().rbegin() + static_cast<difference_type>(descriptor->length())) : reverse_iterator{};
+        return *this ? (handle().rbegin() + descriptor->length()) : reverse_iterator{};
     }
 
     /**
@@ -868,7 +881,7 @@ public:
      * @return The identifier that occupies the given position.
      */
     [[nodiscard]] entity_type operator[](const size_type pos) const {
-        return begin()[static_cast<difference_type>(pos)];
+        return begin()[pos];
     }
 
     /**
@@ -889,11 +902,16 @@ public:
     }
 
     /**
-     * @brief Returns the elements assigned to the given entity.
-     * @tparam Type Type of the element to get.
-     * @tparam Other Other types of elements to get.
+     * @brief Returns the components assigned to the given entity.
+     *
+     * @warning
+     * Attempting to use an entity that doesn't belong to the group results in
+     * undefined behavior.
+     *
+     * @tparam Type Type of the component to get.
+     * @tparam Other Other types of components to get.
      * @param entt A valid identifier.
-     * @return The elements assigned to the entity.
+     * @return The components assigned to the entity.
      */
     template<typename Type, typename... Other>
     [[nodiscard]] decltype(auto) get(const entity_type entt) const {
@@ -901,14 +919,19 @@ public:
     }
 
     /**
-     * @brief Returns the elements assigned to the given entity.
-     * @tparam Index Indexes of the elements to get.
+     * @brief Returns the components assigned to the given entity.
+     *
+     * @warning
+     * Attempting to use an entity that doesn't belong to the groups results in
+     * undefined behavior.
+     *
+     * @tparam Index Indexes of the components to get.
      * @param entt A valid identifier.
-     * @return The elements assigned to the entity.
+     * @return The components assigned to the entity.
      */
     template<std::size_t... Index>
     [[nodiscard]] decltype(auto) get(const entity_type entt) const {
-        const auto cpools = pools_for(std::index_sequence_for<Owned...>{}, std::index_sequence_for<Get...>{});
+        const auto cpools = pools();
 
         if constexpr(sizeof...(Index) == 0) {
             return std::apply([entt](auto *...curr) { return std::tuple_cat(curr->get_as_tuple(entt)...); }, cpools);
@@ -920,12 +943,12 @@ public:
     }
 
     /**
-     * @brief Iterates entities and elements and applies the given function
+     * @brief Iterates entities and components and applies the given function
      * object to them.
      *
      * The function object is invoked for each entity. It is provided with the
-     * entity itself and a set of references to non-empty elements. The
-     * _constness_ of the elements is as requested.<br/>
+     * entity itself and a set of references to non-empty components. The
+     * _constness_ of the components is as requested.<br/>
      * The signature of the function must be equivalent to one of the following
      * forms:
      *
@@ -956,8 +979,8 @@ public:
      * @brief Returns an iterable object to use to _visit_ a group.
      *
      * The iterable object returns tuples that contain the current entity and a
-     * set of references to its non-empty elements. The _constness_ of the
-     * elements is as requested.
+     * set of references to its non-empty components. The _constness_ of the
+     * components is as requested.
      *
      * @note
      * Empty types aren't explicitly instantiated and therefore they are never
@@ -966,8 +989,8 @@ public:
      * @return An iterable object to use to _visit_ the group.
      */
     [[nodiscard]] iterable each() const noexcept {
-        const auto cpools = pools_for(std::index_sequence_for<Owned...>{}, std::index_sequence_for<Get...>{});
-        return iterable{{begin(), cpools}, {end(), cpools}};
+        const auto cpools = pools();
+        return {{begin(), cpools}, {end(), cpools}};
     }
 
     /**
@@ -995,8 +1018,8 @@ public:
      * * An iterator past the last element of the range to sort.
      * * A comparison function to use to compare the elements.
      *
-     * @tparam Type Optional type of element to compare.
-     * @tparam Other Other optional types of elements to compare.
+     * @tparam Type Optional type of component to compare.
+     * @tparam Other Other optional types of components to compare.
      * @tparam Compare Type of comparison function object.
      * @tparam Sort Type of sort function object.
      * @tparam Args Types of arguments to forward to the sort function object.
@@ -1014,7 +1037,7 @@ public:
      *
      * @sa sort
      *
-     * @tparam Index Optional indexes of elements to compare.
+     * @tparam Index Optional indexes of components to compare.
      * @tparam Compare Type of comparison function object.
      * @tparam Sort Type of sort function object.
      * @tparam Args Types of arguments to forward to the sort function object.
@@ -1024,7 +1047,7 @@ public:
      */
     template<std::size_t... Index, typename Compare, typename Sort = std_sort, typename... Args>
     void sort(Compare compare, Sort algo = Sort{}, Args &&...args) const {
-        const auto cpools = pools_for(std::index_sequence_for<Owned...>{}, std::index_sequence_for<Get...>{});
+        const auto cpools = pools();
 
         if constexpr(sizeof...(Index) == 0) {
             static_assert(std::is_invocable_v<Compare, const entity_type, const entity_type>, "Invalid comparison function");

src/entt/entity/handle.hpp

@@ -5,7 +5,6 @@
 #include <tuple>
 #include <type_traits>
 #include <utility>
-#include "../config/config.h"
 #include "../core/iterator.hpp"
 #include "../core/type_traits.hpp"
 #include "entity.hpp"
@@ -13,7 +12,11 @@
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 template<typename It>
@@ -30,7 +33,6 @@ public:
     using reference = value_type;
     using difference_type = std::ptrdiff_t;
     using iterator_category = std::input_iterator_tag;
-    using iterator_concept = std::forward_iterator_tag;
 
     constexpr handle_storage_iterator() noexcept
         : entt{null},
@@ -47,12 +49,12 @@ public:
     }
 
     constexpr handle_storage_iterator &operator++() noexcept {
-        for(++it; it != last && !it->second.contains(entt); ++it) {}
+        while(++it != last && !it->second.contains(entt)) {}
         return *this;
     }
 
     constexpr handle_storage_iterator operator++(int) noexcept {
-        const handle_storage_iterator orig = *this;
+        handle_storage_iterator orig = *this;
         return ++(*this), orig;
     }
 
@@ -84,7 +86,11 @@ template<typename ILhs, typename IRhs>
 }
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /**
  * @brief Non-owning handle to an entity.
@@ -95,29 +101,19 @@ template<typename ILhs, typename IRhs>
  * @tparam Scope Types to which to restrict the scope of a handle.
  */
 template<typename Registry, typename... Scope>
-class basic_handle {
-    using traits_type = entt_traits<typename Registry::entity_type>;
-
-    [[nodiscard]] auto &owner_or_assert() const noexcept {
-        ENTT_ASSERT(owner != nullptr, "Invalid pointer to registry");
-        return static_cast<Registry &>(*owner);
-    }
-
-public:
+struct basic_handle {
     /*! @brief Type of registry accepted by the handle. */
     using registry_type = Registry;
     /*! @brief Underlying entity identifier. */
-    using entity_type = typename traits_type::value_type;
+    using entity_type = typename registry_type::entity_type;
     /*! @brief Underlying version type. */
-    using version_type = typename traits_type::version_type;
+    using version_type = typename registry_type::version_type;
     /*! @brief Unsigned integer type. */
-    using size_type = std::size_t;
-    /*! @brief Iterable handle type. */
-    using iterable = iterable_adaptor<internal::handle_storage_iterator<typename decltype(std::declval<registry_type>().storage())::iterator>>;
+    using size_type = typename registry_type::size_type;
 
     /*! @brief Constructs an invalid handle. */
     basic_handle() noexcept
-        : owner{},
+        : reg{},
           entt{null} {}
 
     /**
@@ -126,7 +122,7 @@ public:
      * @param value A valid identifier.
      */
     basic_handle(registry_type &ref, entity_type value) noexcept
-        : owner{&ref},
+        : reg{&ref},
           entt{value} {}
 
     /**
@@ -139,23 +135,49 @@ public:
      *
      * @return An iterable object to use to _visit_ the handle.
      */
-    [[nodiscard]] iterable storage() const noexcept {
-        auto underlying = owner_or_assert().storage();
-        return iterable{{entt, underlying.begin(), underlying.end()}, {entt, underlying.end(), underlying.end()}};
-    }
-
-    /*! @copydoc valid */
-    [[nodiscard]] explicit operator bool() const noexcept {
-        return owner && owner->valid(entt);
+    [[nodiscard]] auto storage() const noexcept {
+        auto iterable = reg->storage();
+        using iterator_type = internal::handle_storage_iterator<typename decltype(iterable)::iterator>;
+        return iterable_adaptor{iterator_type{entt, iterable.begin(), iterable.end()}, iterator_type{entt, iterable.end(), iterable.end()}};
     }
 
     /**
-     * @brief Checks if a handle refers to a valid registry and entity.
-     * @return True if the handle refers to a valid registry and entity, false
-     * otherwise.
+     * @brief Constructs a const handle from a non-const one.
+     * @tparam Other A valid entity type.
+     * @tparam Args Scope of the handle to construct.
+     * @return A const handle referring to the same registry and the same
+     * entity.
+     */
+    template<typename Other, typename... Args>
+    operator basic_handle<Other, Args...>() const noexcept {
+        static_assert(std::is_same_v<Other, Registry> || std::is_same_v<std::remove_const_t<Other>, Registry>, "Invalid conversion between different handles");
+        static_assert((sizeof...(Scope) == 0 || ((sizeof...(Args) != 0 && sizeof...(Args) <= sizeof...(Scope)) && ... && (type_list_contains_v<type_list<Scope...>, Args>))), "Invalid conversion between different handles");
+
+        return reg ? basic_handle<Other, Args...>{*reg, entt} : basic_handle<Other, Args...>{};
+    }
+
+    /**
+     * @brief Converts a handle to its underlying entity.
+     * @return The contained identifier.
+     */
+    [[nodiscard]] operator entity_type() const noexcept {
+        return entity();
+    }
+
+    /**
+     * @brief Checks if a handle refers to non-null registry pointer and entity.
+     * @return True if the handle refers to non-null registry and entity, false otherwise.
+     */
+    [[nodiscard]] explicit operator bool() const noexcept {
+        return reg && reg->valid(entt);
+    }
+
+    /**
+     * @brief Checks if a handle refers to a valid entity or not.
+     * @return True if the handle refers to a valid entity, false otherwise.
      */
     [[nodiscard]] bool valid() const {
-        return static_cast<bool>(*this);
+        return reg->valid(entt);
     }
 
     /**
@@ -163,7 +185,7 @@ public:
      * @return A pointer to the underlying registry, if any.
      */
     [[nodiscard]] registry_type *registry() const noexcept {
-        return owner;
+        return reg;
     }
 
     /**
@@ -174,14 +196,9 @@ public:
         return entt;
     }
 
-    /*! @copydoc entity */
-    [[nodiscard]] operator entity_type() const noexcept {
-        return entity();
-    }
-
     /*! @brief Destroys the entity associated with a handle. */
     void destroy() {
-        owner_or_assert().destroy(std::exchange(entt, null));
+        reg->destroy(std::exchange(entt, null));
     }
 
     /**
@@ -189,164 +206,148 @@ public:
      * @param version A desired version upon destruction.
      */
     void destroy(const version_type version) {
-        owner_or_assert().destroy(std::exchange(entt, null), version);
+        reg->destroy(std::exchange(entt, null), version);
     }
 
     /**
-     * @brief Assigns the given element to a handle.
-     * @tparam Type Type of element to create.
-     * @tparam Args Types of arguments to use to construct the element.
-     * @param args Parameters to use to initialize the element.
-     * @return A reference to the newly created element.
+     * @brief Assigns the given component to a handle.
+     * @tparam Component Type of component to create.
+     * @tparam Args Types of arguments to use to construct the component.
+     * @param args Parameters to use to initialize the component.
+     * @return A reference to the newly created component.
      */
-    template<typename Type, typename... Args>
-    // NOLINTNEXTLINE(modernize-use-nodiscard)
+    template<typename Component, typename... Args>
     decltype(auto) emplace(Args &&...args) const {
-        static_assert(((sizeof...(Scope) == 0) || ... || std::is_same_v<Type, Scope>), "Invalid type");
-        return owner_or_assert().template emplace<Type>(entt, std::forward<Args>(args)...);
+        static_assert(((sizeof...(Scope) == 0) || ... || std::is_same_v<Component, Scope>), "Invalid type");
+        return reg->template emplace<Component>(entt, std::forward<Args>(args)...);
     }
 
     /**
-     * @brief Assigns or replaces the given element for a handle.
-     * @tparam Type Type of element to assign or replace.
-     * @tparam Args Types of arguments to use to construct the element.
-     * @param args Parameters to use to initialize the element.
-     * @return A reference to the newly created element.
+     * @brief Assigns or replaces the given component for a handle.
+     * @tparam Component Type of component to assign or replace.
+     * @tparam Args Types of arguments to use to construct the component.
+     * @param args Parameters to use to initialize the component.
+     * @return A reference to the newly created component.
      */
-    template<typename Type, typename... Args>
+    template<typename Component, typename... Args>
     decltype(auto) emplace_or_replace(Args &&...args) const {
-        static_assert(((sizeof...(Scope) == 0) || ... || std::is_same_v<Type, Scope>), "Invalid type");
-        return owner_or_assert().template emplace_or_replace<Type>(entt, std::forward<Args>(args)...);
+        static_assert(((sizeof...(Scope) == 0) || ... || std::is_same_v<Component, Scope>), "Invalid type");
+        return reg->template emplace_or_replace<Component>(entt, std::forward<Args>(args)...);
     }
 
     /**
-     * @brief Patches the given element for a handle.
-     * @tparam Type Type of element to patch.
+     * @brief Patches the given component for a handle.
+     * @tparam Component Type of component to patch.
      * @tparam Func Types of the function objects to invoke.
      * @param func Valid function objects.
-     * @return A reference to the patched element.
+     * @return A reference to the patched component.
      */
-    template<typename Type, typename... Func>
+    template<typename Component, typename... Func>
     decltype(auto) patch(Func &&...func) const {
-        static_assert(((sizeof...(Scope) == 0) || ... || std::is_same_v<Type, Scope>), "Invalid type");
-        return owner_or_assert().template patch<Type>(entt, std::forward<Func>(func)...);
+        static_assert(((sizeof...(Scope) == 0) || ... || std::is_same_v<Component, Scope>), "Invalid type");
+        return reg->template patch<Component>(entt, std::forward<Func>(func)...);
     }
 
     /**
-     * @brief Replaces the given element for a handle.
-     * @tparam Type Type of element to replace.
-     * @tparam Args Types of arguments to use to construct the element.
-     * @param args Parameters to use to initialize the element.
-     * @return A reference to the element being replaced.
+     * @brief Replaces the given component for a handle.
+     * @tparam Component Type of component to replace.
+     * @tparam Args Types of arguments to use to construct the component.
+     * @param args Parameters to use to initialize the component.
+     * @return A reference to the component being replaced.
      */
-    template<typename Type, typename... Args>
+    template<typename Component, typename... Args>
     decltype(auto) replace(Args &&...args) const {
-        static_assert(((sizeof...(Scope) == 0) || ... || std::is_same_v<Type, Scope>), "Invalid type");
-        return owner_or_assert().template replace<Type>(entt, std::forward<Args>(args)...);
+        static_assert(((sizeof...(Scope) == 0) || ... || std::is_same_v<Component, Scope>), "Invalid type");
+        return reg->template replace<Component>(entt, std::forward<Args>(args)...);
     }
 
     /**
-     * @brief Removes the given elements from a handle.
-     * @tparam Type Types of elements to remove.
-     * @return The number of elements actually removed.
+     * @brief Removes the given components from a handle.
+     * @tparam Component Types of components to remove.
+     * @return The number of components actually removed.
      */
-    template<typename... Type>
-    // NOLINTNEXTLINE(modernize-use-nodiscard)
+    template<typename... Component>
     size_type remove() const {
-        static_assert(sizeof...(Scope) == 0 || (type_list_contains_v<type_list<Scope...>, Type> && ...), "Invalid type");
-        return owner_or_assert().template remove<Type...>(entt);
+        static_assert(sizeof...(Scope) == 0 || (type_list_contains_v<type_list<Scope...>, Component> && ...), "Invalid type");
+        return reg->template remove<Component...>(entt);
     }
 
     /**
-     * @brief Erases the given elements from a handle.
-     * @tparam Type Types of elements to erase.
+     * @brief Erases the given components from a handle.
+     * @tparam Component Types of components to erase.
      */
-    template<typename... Type>
+    template<typename... Component>
     void erase() const {
-        static_assert(sizeof...(Scope) == 0 || (type_list_contains_v<type_list<Scope...>, Type> && ...), "Invalid type");
-        owner_or_assert().template erase<Type...>(entt);
+        static_assert(sizeof...(Scope) == 0 || (type_list_contains_v<type_list<Scope...>, Component> && ...), "Invalid type");
+        reg->template erase<Component...>(entt);
     }
 
     /**
-     * @brief Checks if a handle has all the given elements.
-     * @tparam Type Elements for which to perform the check.
-     * @return True if the handle has all the elements, false otherwise.
+     * @brief Checks if a handle has all the given components.
+     * @tparam Component Components for which to perform the check.
+     * @return True if the handle has all the components, false otherwise.
      */
-    template<typename... Type>
+    template<typename... Component>
     [[nodiscard]] decltype(auto) all_of() const {
-        return owner_or_assert().template all_of<Type...>(entt);
+        return reg->template all_of<Component...>(entt);
     }
 
     /**
-     * @brief Checks if a handle has at least one of the given elements.
-     * @tparam Type Elements for which to perform the check.
-     * @return True if the handle has at least one of the given elements,
+     * @brief Checks if a handle has at least one of the given components.
+     * @tparam Component Components for which to perform the check.
+     * @return True if the handle has at least one of the given components,
      * false otherwise.
      */
-    template<typename... Type>
+    template<typename... Component>
     [[nodiscard]] decltype(auto) any_of() const {
-        return owner_or_assert().template any_of<Type...>(entt);
+        return reg->template any_of<Component...>(entt);
     }
 
     /**
-     * @brief Returns references to the given elements for a handle.
-     * @tparam Type Types of elements to get.
-     * @return References to the elements owned by the handle.
+     * @brief Returns references to the given components for a handle.
+     * @tparam Component Types of components to get.
+     * @return References to the components owned by the handle.
      */
-    template<typename... Type>
+    template<typename... Component>
     [[nodiscard]] decltype(auto) get() const {
-        static_assert(sizeof...(Scope) == 0 || (type_list_contains_v<type_list<Scope...>, Type> && ...), "Invalid type");
-        return owner_or_assert().template get<Type...>(entt);
+        static_assert(sizeof...(Scope) == 0 || (type_list_contains_v<type_list<Scope...>, Component> && ...), "Invalid type");
+        return reg->template get<Component...>(entt);
     }
 
     /**
-     * @brief Returns a reference to the given element for a handle.
-     * @tparam Type Type of element to get.
-     * @tparam Args Types of arguments to use to construct the element.
-     * @param args Parameters to use to initialize the element.
-     * @return Reference to the element owned by the handle.
+     * @brief Returns a reference to the given component for a handle.
+     * @tparam Component Type of component to get.
+     * @tparam Args Types of arguments to use to construct the component.
+     * @param args Parameters to use to initialize the component.
+     * @return Reference to the component owned by the handle.
      */
-    template<typename Type, typename... Args>
+    template<typename Component, typename... Args>
     [[nodiscard]] decltype(auto) get_or_emplace(Args &&...args) const {
-        static_assert(((sizeof...(Scope) == 0) || ... || std::is_same_v<Type, Scope>), "Invalid type");
-        return owner_or_assert().template get_or_emplace<Type>(entt, std::forward<Args>(args)...);
+        static_assert(((sizeof...(Scope) == 0) || ... || std::is_same_v<Component, Scope>), "Invalid type");
+        return reg->template get_or_emplace<Component>(entt, std::forward<Args>(args)...);
     }
 
     /**
-     * @brief Returns pointers to the given elements for a handle.
-     * @tparam Type Types of elements to get.
-     * @return Pointers to the elements owned by the handle.
+     * @brief Returns pointers to the given components for a handle.
+     * @tparam Component Types of components to get.
+     * @return Pointers to the components owned by the handle.
      */
-    template<typename... Type>
+    template<typename... Component>
     [[nodiscard]] auto try_get() const {
-        static_assert(sizeof...(Scope) == 0 || (type_list_contains_v<type_list<Scope...>, Type> && ...), "Invalid type");
-        return owner_or_assert().template try_get<Type...>(entt);
+        static_assert(sizeof...(Scope) == 0 || (type_list_contains_v<type_list<Scope...>, Component> && ...), "Invalid type");
+        return reg->template try_get<Component...>(entt);
     }
 
     /**
-     * @brief Checks if a handle has elements assigned.
-     * @return True if the handle has no elements assigned, false otherwise.
+     * @brief Checks if a handle has components assigned.
+     * @return True if the handle has no components assigned, false otherwise.
      */
     [[nodiscard]] bool orphan() const {
-        return owner_or_assert().orphan(entt);
-    }
-
-    /**
-     * @brief Returns a const handle from a non-const one.
-     * @tparam Other A valid entity type.
-     * @tparam Args Scope of the handle to construct.
-     * @return A const handle referring to the same registry and the same
-     * entity.
-     */
-    template<typename Other, typename... Args>
-    operator basic_handle<Other, Args...>() const noexcept {
-        static_assert(std::is_same_v<Other, Registry> || std::is_same_v<std::remove_const_t<Other>, Registry>, "Invalid conversion between different handles");
-        static_assert((sizeof...(Scope) == 0 || ((sizeof...(Args) != 0 && sizeof...(Args) <= sizeof...(Scope)) && ... && (type_list_contains_v<type_list<Scope...>, Args>))), "Invalid conversion between different handles");
-        return owner ? basic_handle<Other, Args...>{*owner, entt} : basic_handle<Other, Args...>{};
+        return reg->orphan(entt);
     }
 
 private:
-    registry_type *owner;
+    registry_type *reg;
     entity_type entt;
 };
 
@@ -378,54 +379,6 @@ template<typename... Args, typename... Other>
     return !(lhs == rhs);
 }
 
-/**
- * @brief Compares a handle with the null object.
- * @tparam Args Scope of the handle.
- * @param lhs A valid handle.
- * @param rhs A null object yet to be converted.
- * @return False if the two elements differ, true otherwise.
- */
-template<typename... Args>
-[[nodiscard]] constexpr bool operator==(const basic_handle<Args...> &lhs, const null_t rhs) noexcept {
-    return (lhs.entity() == rhs);
-}
-
-/**
- * @brief Compares a handle with the null object.
- * @tparam Args Scope of the handle.
- * @param lhs A null object yet to be converted.
- * @param rhs A valid handle.
- * @return False if the two elements differ, true otherwise.
- */
-template<typename... Args>
-[[nodiscard]] constexpr bool operator==(const null_t lhs, const basic_handle<Args...> &rhs) noexcept {
-    return (rhs == lhs);
-}
-
-/**
- * @brief Compares a handle with the null object.
- * @tparam Args Scope of the handle.
- * @param lhs A valid handle.
- * @param rhs A null object yet to be converted.
- * @return True if the two elements differ, false otherwise.
- */
-template<typename... Args>
-[[nodiscard]] constexpr bool operator!=(const basic_handle<Args...> &lhs, const null_t rhs) noexcept {
-    return (lhs.entity() != rhs);
-}
-
-/**
- * @brief Compares a handle with the null object.
- * @tparam Args Scope of the handle.
- * @param lhs A null object yet to be converted.
- * @param rhs A valid handle.
- * @return True if the two elements differ, false otherwise.
- */
-template<typename... Args>
-[[nodiscard]] constexpr bool operator!=(const null_t lhs, const basic_handle<Args...> &rhs) noexcept {
-    return (rhs != lhs);
-}
-
 } // namespace entt
 
 #endif

src/entt/entity/helper.hpp

@@ -6,10 +6,9 @@
 #include <utility>
 #include "../core/fwd.hpp"
 #include "../core/type_traits.hpp"
-#include "component.hpp"
+#include "../signal/delegate.hpp"
 #include "fwd.hpp"
 #include "group.hpp"
-#include "storage.hpp"
 #include "view.hpp"
 
 namespace entt {
@@ -21,8 +20,8 @@ namespace entt {
 template<typename Registry>
 class as_view {
     template<typename... Get, typename... Exclude>
-    [[nodiscard]] auto dispatch(get_t<Get...>, exclude_t<Exclude...>) const {
-        return reg->template view<constness_as_t<typename Get::element_type, Get>...>(exclude_t<constness_as_t<typename Exclude::element_type, Exclude>...>{});
+    auto dispatch(get_t<Get...>, exclude_t<Exclude...>) const {
+        return reg.template view<constness_as_t<typename Get::value_type, Get>...>(exclude_t<constness_as_t<typename Exclude::value_type, Exclude>...>{});
     }
 
 public:
@@ -36,7 +35,7 @@ public:
      * @param source A valid reference to a registry.
      */
     as_view(registry_type &source) noexcept
-        : reg{&source} {}
+        : reg{source} {}
 
     /**
      * @brief Conversion function from a registry to a view.
@@ -50,7 +49,7 @@ public:
     }
 
 private:
-    registry_type *reg;
+    registry_type &reg;
 };
 
 /**
@@ -60,11 +59,11 @@ private:
 template<typename Registry>
 class as_group {
     template<typename... Owned, typename... Get, typename... Exclude>
-    [[nodiscard]] auto dispatch(owned_t<Owned...>, get_t<Get...>, exclude_t<Exclude...>) const {
+    auto dispatch(owned_t<Owned...>, get_t<Get...>, exclude_t<Exclude...>) const {
         if constexpr(std::is_const_v<registry_type>) {
-            return reg->template group_if_exists<typename Owned::element_type...>(get_t<typename Get::element_type...>{}, exclude_t<typename Exclude::element_type...>{});
+            return reg.template group_if_exists<typename Owned::value_type...>(get_t<typename Get::value_type...>{}, exclude_t<typename Exclude::value_type...>{});
         } else {
-            return reg->template group<constness_as_t<typename Owned::element_type, Owned>...>(get_t<constness_as_t<typename Get::element_type, Get>...>{}, exclude_t<constness_as_t<typename Exclude::element_type, Exclude>...>{});
+            return reg.template group<constness_as_t<typename Owned::value_type, Owned>...>(get_t<constness_as_t<typename Get::value_type, Get>...>{}, exclude_t<constness_as_t<typename Exclude::value_type, Exclude>...>{});
         }
     }
 
@@ -79,7 +78,7 @@ public:
      * @param source A valid reference to a registry.
      */
     as_group(registry_type &source) noexcept
-        : reg{&source} {}
+        : reg{source} {}
 
     /**
      * @brief Conversion function from a registry to a group.
@@ -94,47 +93,50 @@ public:
     }
 
 private:
-    registry_type *reg;
+    registry_type &reg;
 };
 
 /**
  * @brief Helper to create a listener that directly invokes a member function.
- * @tparam Member Member function to invoke on an element of the given type.
+ * @tparam Member Member function to invoke on a component of the given type.
  * @tparam Registry Basic registry type.
- * @param reg A registry that contains the given entity and its elements.
- * @param entt Entity from which to get the element.
+ * @param reg A registry that contains the given entity and its components.
+ * @param entt Entity from which to get the component.
  */
-template<auto Member, typename Registry = std::decay_t<nth_argument_t<0u, decltype(Member)>>>
+template<auto Member, typename Registry = std::decay_t<nth_argument_t<0u, Member>>>
 void invoke(Registry &reg, const typename Registry::entity_type entt) {
     static_assert(std::is_member_function_pointer_v<decltype(Member)>, "Invalid pointer to non-static member function");
-    (reg.template get<member_class_t<decltype(Member)>>(entt).*Member)(reg, entt);
+    delegate<void(Registry &, const typename Registry::entity_type)> func;
+    func.template connect<Member>(reg.template get<member_class_t<decltype(Member)>>(entt));
+    func(reg, entt);
 }
 
 /**
- * @brief Returns the entity associated with a given element.
+ * @brief Returns the entity associated with a given component.
  *
  * @warning
- * Currently, this function only works correctly with the default storage as it
- * makes assumptions about how the elements are laid out.
+ * Currently, this function only works correctly with the default pool as it
+ * makes assumptions about how the components are laid out.
  *
- * @tparam Args Storage type template parameters.
- * @param storage A storage that contains the given element.
- * @param instance A valid element instance.
- * @return The entity associated with the given element.
+ * @tparam Registry Basic registry type.
+ * @tparam Component Type of component.
+ * @param reg A registry that contains the given entity and its components.
+ * @param instance A valid component instance.
+ * @return The entity associated with the given component.
  */
-template<typename... Args>
-typename basic_storage<Args...>::entity_type to_entity(const basic_storage<Args...> &storage, const typename basic_storage<Args...>::value_type &instance) {
-    using traits_type = component_traits<typename basic_storage<Args...>::value_type, typename basic_storage<Args...>::entity_type>;
-    static_assert(traits_type::page_size != 0u, "Unexpected page size");
-    const auto *page = storage.raw();
+template<typename Registry, typename Component>
+typename Registry::entity_type to_entity(const Registry &reg, const Component &instance) {
+    if(const auto *storage = reg.template storage<Component>(); storage) {
+        constexpr auto page_size = std::remove_const_t<std::remove_pointer_t<decltype(storage)>>::traits_type::page_size;
+        const typename Registry::common_type &base = *storage;
+        const auto *addr = std::addressof(instance);
 
-    // NOLINTBEGIN(cppcoreguidelines-pro-bounds-pointer-arithmetic)
-    for(std::size_t pos{}, count = storage.size(); pos < count; pos += traits_type::page_size, ++page) {
-        if(const auto dist = (std::addressof(instance) - *page); dist >= 0 && dist < static_cast<decltype(dist)>(traits_type::page_size)) {
-            return *(static_cast<const typename basic_storage<Args...>::base_type &>(storage).rbegin() + static_cast<decltype(dist)>(pos) + dist);
+        for(auto it = base.rbegin(), last = base.rend(); it < last; it += page_size) {
+            if(const auto dist = (addr - std::addressof(storage->get(*it))); dist >= 0 && dist < static_cast<decltype(dist)>(page_size)) {
+                return *(it + dist);
+            }
         }
     }
-    // NOLINTEND(cppcoreguidelines-pro-bounds-pointer-arithmetic)
 
     return null;
 }

src/entt/entity/mixin.hpp

@@ -5,40 +5,12 @@
 #include <utility>
 #include "../config/config.h"
 #include "../core/any.hpp"
-#include "../core/type_info.hpp"
 #include "../signal/sigh.hpp"
 #include "entity.hpp"
 #include "fwd.hpp"
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
-namespace internal {
-
-template<typename, typename, typename = void>
-struct has_on_construct final: std::false_type {};
-
-template<typename Type, typename Registry>
-struct has_on_construct<Type, Registry, std::void_t<decltype(Type::on_construct(std::declval<Registry &>(), std::declval<Registry>().create()))>>
-    : std::true_type {};
-
-template<typename, typename, typename = void>
-struct has_on_update final: std::false_type {};
-
-template<typename Type, typename Registry>
-struct has_on_update<Type, Registry, std::void_t<decltype(Type::on_update(std::declval<Registry &>(), std::declval<Registry>().create()))>>
-    : std::true_type {};
-
-template<typename, typename, typename = void>
-struct has_on_destroy final: std::false_type {};
-
-template<typename Type, typename Registry>
-struct has_on_destroy<Type, Registry, std::void_t<decltype(Type::on_destroy(std::declval<Registry &>(), std::declval<Registry>().create()))>>
-    : std::true_type {};
-
-} // namespace internal
-/*! @endcond */
-
 /**
  * @brief Mixin type used to add signal support to storage types.
  *
@@ -50,26 +22,20 @@ struct has_on_destroy<Type, Registry, std::void_t<decltype(Type::on_destroy(std:
  *
  * This applies to all signals made available.
  *
- * @tparam Type Underlying storage type.
- * @tparam Registry Basic registry type.
+ * @tparam Type The type of the underlying storage.
  */
-template<typename Type, typename Registry>
-class basic_sigh_mixin final: public Type {
+template<typename Type>
+class sigh_mixin final: public Type {
     using underlying_type = Type;
-    using owner_type = Registry;
-
-    using basic_registry_type = basic_registry<typename owner_type::entity_type, typename owner_type::allocator_type>;
-    using sigh_type = sigh<void(owner_type &, const typename underlying_type::entity_type), typename underlying_type::allocator_type>;
+    using basic_registry_type = basic_registry<typename underlying_type::entity_type, typename underlying_type::base_type::allocator_type>;
+    using sigh_type = sigh<void(basic_registry_type &, const typename underlying_type::entity_type), typename underlying_type::allocator_type>;
     using underlying_iterator = typename underlying_type::base_type::basic_iterator;
 
-    static_assert(std::is_base_of_v<basic_registry_type, owner_type>, "Invalid registry type");
-
-    [[nodiscard]] auto &owner_or_assert() const noexcept {
+    basic_registry_type &owner_or_assert() const noexcept {
         ENTT_ASSERT(owner != nullptr, "Invalid pointer to registry");
-        return static_cast<owner_type &>(*owner);
+        return *owner;
     }
 
-private:
     void pop(underlying_iterator first, underlying_iterator last) final {
         if(auto &reg = owner_or_assert(); destruction.empty()) {
             underlying_type::pop(first, last);
@@ -85,19 +51,13 @@ private:
 
     void pop_all() final {
         if(auto &reg = owner_or_assert(); !destruction.empty()) {
-            if constexpr(std::is_same_v<typename underlying_type::element_type, entity_type>) {
-                for(typename underlying_type::size_type pos{}, last = underlying_type::free_list(); pos < last; ++pos) {
-                    destruction.publish(reg, underlying_type::base_type::operator[](pos));
-                }
-            } else {
-                for(auto entt: static_cast<typename underlying_type::base_type &>(*this)) {
-                    if constexpr(underlying_type::storage_policy == deletion_policy::in_place) {
-                        if(entt != tombstone) {
-                            destruction.publish(reg, entt);
-                        }
-                    } else {
+            for(auto pos = underlying_type::each().begin().base().index(); !(pos < 0); --pos) {
+                if constexpr(underlying_type::traits_type::in_place_delete) {
+                    if(const auto entt = underlying_type::operator[](static_cast<typename underlying_type::size_type>(pos)); entt != tombstone) {
                         destruction.publish(reg, entt);
                     }
+                } else {
+                    destruction.publish(reg, underlying_type::operator[](static_cast<typename underlying_type::size_type>(pos)));
                 }
             }
         }
@@ -115,99 +75,63 @@ private:
         return it;
     }
 
-    void bind_any(any value) noexcept final {
-        owner = any_cast<basic_registry_type>(&value);
-
-        if constexpr(!std::is_same_v<registry_type, basic_registry_type>) {
-            if(owner == nullptr) {
-                owner = any_cast<registry_type>(&value);
-            }
-        }
-
-        underlying_type::bind_any(std::move(value));
-    }
-
 public:
     /*! @brief Allocator type. */
     using allocator_type = typename underlying_type::allocator_type;
     /*! @brief Underlying entity identifier. */
     using entity_type = typename underlying_type::entity_type;
     /*! @brief Expected registry type. */
-    using registry_type = owner_type;
+    using registry_type = basic_registry_type;
 
     /*! @brief Default constructor. */
-    basic_sigh_mixin()
-        : basic_sigh_mixin{allocator_type{}} {}
+    sigh_mixin()
+        : sigh_mixin{allocator_type{}} {}
 
     /**
      * @brief Constructs an empty storage with a given allocator.
      * @param allocator The allocator to use.
      */
-    explicit basic_sigh_mixin(const allocator_type &allocator)
+    explicit sigh_mixin(const allocator_type &allocator)
         : underlying_type{allocator},
           owner{},
           construction{allocator},
           destruction{allocator},
-          update{allocator} {
-        if constexpr(internal::has_on_construct<typename underlying_type::element_type, Registry>::value) {
-            entt::sink{construction}.template connect<&underlying_type::element_type::on_construct>();
-        }
-
-        if constexpr(internal::has_on_update<typename underlying_type::element_type, Registry>::value) {
-            entt::sink{update}.template connect<&underlying_type::element_type::on_update>();
-        }
-
-        if constexpr(internal::has_on_destroy<typename underlying_type::element_type, Registry>::value) {
-            entt::sink{destruction}.template connect<&underlying_type::element_type::on_destroy>();
-        }
-    }
-
-    /*! @brief Default copy constructor, deleted on purpose. */
-    basic_sigh_mixin(const basic_sigh_mixin &) = delete;
+          update{allocator} {}
 
     /**
      * @brief Move constructor.
      * @param other The instance to move from.
      */
-    // NOLINTBEGIN(bugprone-use-after-move)
-    basic_sigh_mixin(basic_sigh_mixin &&other) noexcept
+    sigh_mixin(sigh_mixin &&other) noexcept
         : underlying_type{std::move(other)},
           owner{other.owner},
           construction{std::move(other.construction)},
           destruction{std::move(other.destruction)},
           update{std::move(other.update)} {}
-    // NOLINTEND(bugprone-use-after-move)
 
     /**
      * @brief Allocator-extended move constructor.
      * @param other The instance to move from.
      * @param allocator The allocator to use.
      */
-    // NOLINTBEGIN(bugprone-use-after-move)
-    basic_sigh_mixin(basic_sigh_mixin &&other, const allocator_type &allocator)
+    sigh_mixin(sigh_mixin &&other, const allocator_type &allocator) noexcept
         : underlying_type{std::move(other), allocator},
           owner{other.owner},
           construction{std::move(other.construction), allocator},
           destruction{std::move(other.destruction), allocator},
           update{std::move(other.update), allocator} {}
-    // NOLINTEND(bugprone-use-after-move)
-
-    /*! @brief Default destructor. */
-    ~basic_sigh_mixin() override = default;
-
-    /**
-     * @brief Default copy assignment operator, deleted on purpose.
-     * @return This mixin.
-     */
-    basic_sigh_mixin &operator=(const basic_sigh_mixin &) = delete;
 
     /**
      * @brief Move assignment operator.
      * @param other The instance to move from.
-     * @return This mixin.
+     * @return This storage.
      */
-    basic_sigh_mixin &operator=(basic_sigh_mixin &&other) noexcept {
-        swap(other);
+    sigh_mixin &operator=(sigh_mixin &&other) noexcept {
+        underlying_type::operator=(std::move(other));
+        owner = other.owner;
+        construction = std::move(other.construction);
+        destruction = std::move(other.destruction);
+        update = std::move(other.update);
         return *this;
     }
 
@@ -215,13 +139,13 @@ public:
      * @brief Exchanges the contents with those of a given storage.
      * @param other Storage to exchange the content with.
      */
-    void swap(basic_sigh_mixin &other) noexcept {
+    void swap(sigh_mixin &other) {
         using std::swap;
+        underlying_type::swap(other);
         swap(owner, other.owner);
         swap(construction, other.construction);
         swap(destruction, other.destruction);
         swap(update, other.update);
-        underlying_type::swap(other);
     }
 
     /**
@@ -270,80 +194,47 @@ public:
     }
 
     /**
-     * @brief Checks if a mixin refers to a valid registry.
-     * @return True if the mixin refers to a valid registry, false otherwise.
+     * @brief Emplace elements into a storage.
+     *
+     * The behavior of this operation depends on the underlying storage type
+     * (for example, components vs entities).<br/>
+     * Refer to the specific documentation for more details.
+     *
+     * @return A return value as returned by the underlying storage.
      */
-    [[nodiscard]] explicit operator bool() const noexcept {
-        return (owner != nullptr);
-    }
-
-    /**
-     * @brief Returns a pointer to the underlying registry, if any.
-     * @return A pointer to the underlying registry, if any.
-     */
-    [[nodiscard]] const registry_type &registry() const noexcept {
-        return owner_or_assert();
-    }
-
-    /*! @copydoc registry */
-    [[nodiscard]] registry_type &registry() noexcept {
-        return owner_or_assert();
-    }
-
-    /**
-     * @brief Creates a new identifier or recycles a destroyed one.
-     * @return A valid identifier.
-     */
-    auto generate() {
-        const auto entt = underlying_type::generate();
+    auto emplace() {
+        const auto entt = underlying_type::emplace();
         construction.publish(owner_or_assert(), entt);
         return entt;
     }
 
     /**
-     * @brief Creates a new identifier or recycles a destroyed one.
-     * @param hint Required identifier.
-     * @return A valid identifier.
+     * @brief Emplace elements into a storage.
+     *
+     * The behavior of this operation depends on the underlying storage type
+     * (for example, components vs entities).<br/>
+     * Refer to the specific documentation for more details.
+     *
+     * @tparam Args Types of arguments to forward to the underlying storage.
+     * @param hint A valid identifier.
+     * @param args Parameters to forward to the underlying storage.
+     * @return A return value as returned by the underlying storage.
      */
-    entity_type generate(const entity_type hint) {
-        const auto entt = underlying_type::generate(hint);
-        construction.publish(owner_or_assert(), entt);
-        return entt;
-    }
-
-    /**
-     * @brief Assigns each element in a range an identifier.
-     * @tparam It Type of mutable forward iterator.
-     * @param first An iterator to the first element of the range to generate.
-     * @param last An iterator past the last element of the range to generate.
-     */
-    template<typename It>
-    void generate(It first, It last) {
-        underlying_type::generate(first, last);
-
-        if(auto &reg = owner_or_assert(); !construction.empty()) {
-            for(; first != last; ++first) {
-                construction.publish(reg, *first);
-            }
+    template<typename... Args>
+    decltype(auto) emplace(const entity_type hint, Args &&...args) {
+        if constexpr(std::is_same_v<typename underlying_type::value_type, typename underlying_type::entity_type>) {
+            const auto entt = underlying_type::emplace(hint, std::forward<Args>(args)...);
+            construction.publish(owner_or_assert(), entt);
+            return entt;
+        } else {
+            underlying_type::emplace(hint, std::forward<Args>(args)...);
+            construction.publish(owner_or_assert(), hint);
+            return this->get(hint);
         }
     }
 
     /**
-     * @brief Assigns an entity to a storage and constructs its object.
-     * @tparam Args Types of arguments to forward to the underlying storage.
-     * @param entt A valid identifier.
-     * @param args Parameters to forward to the underlying storage.
-     * @return A reference to the newly created object.
-     */
-    template<typename... Args>
-    decltype(auto) emplace(const entity_type entt, Args &&...args) {
-        underlying_type::emplace(entt, std::forward<Args>(args)...);
-        construction.publish(owner_or_assert(), entt);
-        return this->get(entt);
-    }
-
-    /**
-     * @brief Updates the instance assigned to a given entity in-place.
+     * @brief Patches the given instance for an entity.
      * @tparam Func Types of the function objects to invoke.
      * @param entt A valid identifier.
      * @param func Valid function objects.
@@ -357,27 +248,39 @@ public:
     }
 
     /**
-     * @brief Assigns one or more entities to a storage and constructs their
-     * objects from a given instance.
-     * @tparam It Type of input iterator.
+     * @brief Emplace elements into a storage.
+     *
+     * The behavior of this operation depends on the underlying storage type
+     * (for example, components vs entities).<br/>
+     * Refer to the specific documentation for more details.
+     *
+     * @tparam It Iterator type (as required by the underlying storage type).
      * @tparam Args Types of arguments to forward to the underlying storage.
-     * @param first An iterator to the first element of the range of entities.
-     * @param last An iterator past the last element of the range of entities.
+     * @param first An iterator to the first element of the range.
+     * @param last An iterator past the last element of the range.
      * @param args Parameters to use to forward to the underlying storage.
      */
     template<typename It, typename... Args>
     void insert(It first, It last, Args &&...args) {
-        auto from = underlying_type::size();
         underlying_type::insert(first, last, std::forward<Args>(args)...);
 
         if(auto &reg = owner_or_assert(); !construction.empty()) {
-            // fine as long as insert passes force_back true to try_emplace
-            for(const auto to = underlying_type::size(); from != to; ++from) {
-                construction.publish(reg, underlying_type::operator[](from));
+            for(; first != last; ++first) {
+                construction.publish(reg, *first);
             }
         }
     }
 
+    /**
+     * @brief Forwards variables to derived classes, if any.
+     * @param value A variable wrapped in an opaque container.
+     */
+    void bind(any value) noexcept final {
+        auto *reg = any_cast<basic_registry_type>(&value);
+        owner = reg ? reg : owner;
+        underlying_type::bind(std::move(value));
+    }
+
 private:
     basic_registry_type *owner;
     sigh_type construction;
@@ -385,215 +288,6 @@ private:
     sigh_type update;
 };
 
-/**
- * @brief Mixin type used to add _reactive_ support to storage types.
- * @tparam Type Underlying storage type.
- * @tparam Registry Basic registry type.
- */
-template<typename Type, typename Registry>
-class basic_reactive_mixin final: public Type {
-    using underlying_type = Type;
-    using owner_type = Registry;
-
-    using alloc_traits = std::allocator_traits<typename underlying_type::allocator_type>;
-    using basic_registry_type = basic_registry<typename owner_type::entity_type, typename owner_type::allocator_type>;
-    using container_type = std::vector<connection, typename alloc_traits::template rebind_alloc<connection>>;
-
-    static_assert(std::is_base_of_v<basic_registry_type, owner_type>, "Invalid registry type");
-
-    [[nodiscard]] auto &owner_or_assert() const noexcept {
-        ENTT_ASSERT(owner != nullptr, "Invalid pointer to registry");
-        return static_cast<owner_type &>(*owner);
-    }
-
-    void emplace_element(const Registry &, typename underlying_type::entity_type entity) {
-        if(!underlying_type::contains(entity)) {
-            underlying_type::emplace(entity);
-        }
-    }
-
-private:
-    void bind_any(any value) noexcept final {
-        owner = any_cast<basic_registry_type>(&value);
-
-        if constexpr(!std::is_same_v<registry_type, basic_registry_type>) {
-            if(owner == nullptr) {
-                owner = any_cast<registry_type>(&value);
-            }
-        }
-
-        underlying_type::bind_any(std::move(value));
-    }
-
-public:
-    /*! @brief Allocator type. */
-    using allocator_type = typename underlying_type::allocator_type;
-    /*! @brief Underlying entity identifier. */
-    using entity_type = typename underlying_type::entity_type;
-    /*! @brief Expected registry type. */
-    using registry_type = owner_type;
-
-    /*! @brief Default constructor. */
-    basic_reactive_mixin()
-        : basic_reactive_mixin{allocator_type{}} {}
-
-    /**
-     * @brief Constructs an empty storage with a given allocator.
-     * @param allocator The allocator to use.
-     */
-    explicit basic_reactive_mixin(const allocator_type &allocator)
-        : underlying_type{allocator},
-          owner{},
-          conn{allocator} {
-    }
-
-    /*! @brief Default copy constructor, deleted on purpose. */
-    basic_reactive_mixin(const basic_reactive_mixin &) = delete;
-
-    /**
-     * @brief Move constructor.
-     * @param other The instance to move from.
-     */
-    // NOLINTBEGIN(bugprone-use-after-move)
-    basic_reactive_mixin(basic_reactive_mixin &&other) noexcept
-        : underlying_type{std::move(other)},
-          owner{other.owner},
-          conn{} {
-    }
-    // NOLINTEND(bugprone-use-after-move)
-
-    /**
-     * @brief Allocator-extended move constructor.
-     * @param other The instance to move from.
-     * @param allocator The allocator to use.
-     */
-    // NOLINTBEGIN(bugprone-use-after-move)
-    basic_reactive_mixin(basic_reactive_mixin &&other, const allocator_type &allocator)
-        : underlying_type{std::move(other), allocator},
-          owner{other.owner},
-          conn{allocator} {
-    }
-    // NOLINTEND(bugprone-use-after-move)
-
-    /*! @brief Default destructor. */
-    ~basic_reactive_mixin() override = default;
-
-    /**
-     * @brief Default copy assignment operator, deleted on purpose.
-     * @return This mixin.
-     */
-    basic_reactive_mixin &operator=(const basic_reactive_mixin &) = delete;
-
-    /**
-     * @brief Move assignment operator.
-     * @param other The instance to move from.
-     * @return This mixin.
-     */
-    basic_reactive_mixin &operator=(basic_reactive_mixin &&other) noexcept {
-        underlying_type::swap(other);
-        return *this;
-    }
-
-    /**
-     * @brief Makes storage _react_ to creation of objects of the given type.
-     * @tparam Clazz Type of element to _react_ to.
-     * @tparam Candidate Function to use to _react_ to the event.
-     * @param id Optional name used to map the storage within the registry.
-     * @return This mixin.
-     */
-    template<typename Clazz, auto Candidate = &basic_reactive_mixin::emplace_element>
-    basic_reactive_mixin &on_construct(const id_type id = type_hash<Clazz>::value()) {
-        auto curr = owner_or_assert().template storage<Clazz>(id).on_construct().template connect<Candidate>(*this);
-        conn.push_back(std::move(curr));
-        return *this;
-    }
-
-    /**
-     * @brief Makes storage _react_ to update of objects of the given type.
-     * @tparam Clazz Type of element to _react_ to.
-     * @tparam Candidate Function to use to _react_ to the event.
-     * @param id Optional name used to map the storage within the registry.
-     * @return This mixin.
-     */
-    template<typename Clazz, auto Candidate = &basic_reactive_mixin::emplace_element>
-    basic_reactive_mixin &on_update(const id_type id = type_hash<Clazz>::value()) {
-        auto curr = owner_or_assert().template storage<Clazz>(id).on_update().template connect<Candidate>(*this);
-        conn.push_back(std::move(curr));
-        return *this;
-    }
-
-    /**
-     * @brief Makes storage _react_ to destruction of objects of the given type.
-     * @tparam Clazz Type of element to _react_ to.
-     * @tparam Candidate Function to use to _react_ to the event.
-     * @param id Optional name used to map the storage within the registry.
-     * @return This mixin.
-     */
-    template<typename Clazz, auto Candidate = &basic_reactive_mixin::emplace_element>
-    basic_reactive_mixin &on_destroy(const id_type id = type_hash<Clazz>::value()) {
-        auto curr = owner_or_assert().template storage<Clazz>(id).on_destroy().template connect<Candidate>(*this);
-        conn.push_back(std::move(curr));
-        return *this;
-    }
-
-    /**
-     * @brief Checks if a mixin refers to a valid registry.
-     * @return True if the mixin refers to a valid registry, false otherwise.
-     */
-    [[nodiscard]] explicit operator bool() const noexcept {
-        return (owner != nullptr);
-    }
-
-    /**
-     * @brief Returns a pointer to the underlying registry, if any.
-     * @return A pointer to the underlying registry, if any.
-     */
-    [[nodiscard]] const registry_type &registry() const noexcept {
-        return owner_or_assert();
-    }
-
-    /*! @copydoc registry */
-    [[nodiscard]] registry_type &registry() noexcept {
-        return owner_or_assert();
-    }
-
-    /**
-     * @brief Returns a view that is filtered by the underlying storage.
-     * @tparam Get Types of elements used to construct the view.
-     * @tparam Exclude Types of elements used to filter the view.
-     * @return A newly created view.
-     */
-    template<typename... Get, typename... Exclude>
-    [[nodiscard]] basic_view<get_t<const basic_reactive_mixin, typename basic_registry_type::template storage_for_type<const Get>...>, exclude_t<typename basic_registry_type::template storage_for_type<const Exclude>...>>
-    view(exclude_t<Exclude...> = exclude_t{}) const {
-        const owner_type &parent = owner_or_assert();
-        basic_view<get_t<const basic_reactive_mixin, typename basic_registry_type::template storage_for_type<const Get>...>, exclude_t<typename basic_registry_type::template storage_for_type<const Exclude>...>> elem{};
-        [&elem](const auto *...curr) { ((curr ? elem.storage(*curr) : void()), ...); }(parent.template storage<std::remove_const_t<Exclude>>()..., parent.template storage<std::remove_const_t<Get>>()..., this);
-        return elem;
-    }
-
-    /*! @copydoc view */
-    template<typename... Get, typename... Exclude>
-    [[nodiscard]] basic_view<get_t<const basic_reactive_mixin, typename basic_registry_type::template storage_for_type<Get>...>, exclude_t<typename basic_registry_type::template storage_for_type<Exclude>...>>
-    view(exclude_t<Exclude...> = exclude_t{}) {
-        std::conditional_t<((std::is_const_v<Get> && ...) && (std::is_const_v<Exclude> && ...)), const owner_type, owner_type> &parent = owner_or_assert();
-        return {*this, parent.template storage<std::remove_const_t<Get>>()..., parent.template storage<std::remove_const_t<Exclude>>()...};
-    }
-
-    /*! @brief Releases all connections to the underlying registry, if any. */
-    void reset() {
-        for(auto &&curr: conn) {
-            curr.release();
-        }
-
-        conn.clear();
-    }
-
-private:
-    basic_registry_type *owner;
-    container_type conn;
-};
-
 } // namespace entt
 
 #endif

src/entt/entity/observer.hpp

@@ -0,0 +1,436 @@
+#ifndef ENTT_ENTITY_OBSERVER_HPP
+#define ENTT_ENTITY_OBSERVER_HPP
+
+#include <cstddef>
+#include <cstdint>
+#include <limits>
+#include <type_traits>
+#include <utility>
+#include "../core/type_traits.hpp"
+#include "../signal/delegate.hpp"
+#include "fwd.hpp"
+#include "storage.hpp"
+
+namespace entt {
+
+/*! @brief Grouping matcher. */
+template<typename...>
+struct matcher {};
+
+/**
+ * @brief Collector.
+ *
+ * Primary template isn't defined on purpose. All the specializations give a
+ * compile-time error, but for a few reasonable cases.
+ */
+template<typename...>
+struct basic_collector;
+
+/**
+ * @brief Collector.
+ *
+ * A collector contains a set of rules (literally, matchers) to use to track
+ * entities.<br/>
+ * Its main purpose is to generate a descriptor that allows an observer to know
+ * how to connect to a registry.
+ */
+template<>
+struct basic_collector<> {
+    /**
+     * @brief Adds a grouping matcher to the collector.
+     * @tparam AllOf Types of components tracked by the matcher.
+     * @tparam NoneOf Types of components used to filter out entities.
+     * @return The updated collector.
+     */
+    template<typename... AllOf, typename... NoneOf>
+    static constexpr auto group(exclude_t<NoneOf...> = exclude_t{}) noexcept {
+        return basic_collector<matcher<type_list<>, type_list<>, type_list<NoneOf...>, AllOf...>>{};
+    }
+
+    /**
+     * @brief Adds an observing matcher to the collector.
+     * @tparam AnyOf Type of component for which changes should be detected.
+     * @return The updated collector.
+     */
+    template<typename AnyOf>
+    static constexpr auto update() noexcept {
+        return basic_collector<matcher<type_list<>, type_list<>, AnyOf>>{};
+    }
+};
+
+/**
+ * @brief Collector.
+ * @copydetails basic_collector<>
+ * @tparam Reject Untracked types used to filter out entities.
+ * @tparam Require Untracked types required by the matcher.
+ * @tparam Rule Specific details of the current matcher.
+ * @tparam Other Other matchers.
+ */
+template<typename... Reject, typename... Require, typename... Rule, typename... Other>
+struct basic_collector<matcher<type_list<Reject...>, type_list<Require...>, Rule...>, Other...> {
+    /*! @brief Current matcher. */
+    using current_type = matcher<type_list<Reject...>, type_list<Require...>, Rule...>;
+
+    /**
+     * @brief Adds a grouping matcher to the collector.
+     * @tparam AllOf Types of components tracked by the matcher.
+     * @tparam NoneOf Types of components used to filter out entities.
+     * @return The updated collector.
+     */
+    template<typename... AllOf, typename... NoneOf>
+    static constexpr auto group(exclude_t<NoneOf...> = exclude_t{}) noexcept {
+        return basic_collector<matcher<type_list<>, type_list<>, type_list<NoneOf...>, AllOf...>, current_type, Other...>{};
+    }
+
+    /**
+     * @brief Adds an observing matcher to the collector.
+     * @tparam AnyOf Type of component for which changes should be detected.
+     * @return The updated collector.
+     */
+    template<typename AnyOf>
+    static constexpr auto update() noexcept {
+        return basic_collector<matcher<type_list<>, type_list<>, AnyOf>, current_type, Other...>{};
+    }
+
+    /**
+     * @brief Updates the filter of the last added matcher.
+     * @tparam AllOf Types of components required by the matcher.
+     * @tparam NoneOf Types of components used to filter out entities.
+     * @return The updated collector.
+     */
+    template<typename... AllOf, typename... NoneOf>
+    static constexpr auto where(exclude_t<NoneOf...> = exclude_t{}) noexcept {
+        using extended_type = matcher<type_list<Reject..., NoneOf...>, type_list<Require..., AllOf...>, Rule...>;
+        return basic_collector<extended_type, Other...>{};
+    }
+};
+
+/*! @brief Variable template used to ease the definition of collectors. */
+inline constexpr basic_collector<> collector{};
+
+/**
+ * @brief Observer.
+ *
+ * An observer returns all the entities and only the entities that fit the
+ * requirements of at least one matcher. Moreover, it's guaranteed that the
+ * entity list is tightly packed in memory for fast iterations.<br/>
+ * In general, observers don't stay true to the order of any set of components.
+ *
+ * Observers work mainly with two types of matchers, provided through a
+ * collector:
+ *
+ * * Observing matcher: an observer will return at least all the living entities
+ *   for which one or more of the given components have been updated and not yet
+ *   destroyed.
+ * * Grouping matcher: an observer will return at least all the living entities
+ *   that would have entered the given group if it existed and that would have
+ *   not yet left it.
+ *
+ * If an entity respects the requirements of multiple matchers, it will be
+ * returned once and only once by the observer in any case.
+ *
+ * Matchers support also filtering by means of a _where_ clause that accepts
+ * both a list of types and an exclusion list.<br/>
+ * Whenever a matcher finds that an entity matches its requirements, the
+ * condition of the filter is verified before to register the entity itself.
+ * Moreover, a registered entity isn't returned by the observer if the condition
+ * set by the filter is broken in the meantime.
+ *
+ * @b Important
+ *
+ * Iterators aren't invalidated if:
+ *
+ * * New instances of the given components are created and assigned to entities.
+ * * The entity currently pointed is modified (as an example, if one of the
+ *   given components is removed from the entity to which the iterator points).
+ * * The entity currently pointed is destroyed.
+ *
+ * In all the other cases, modifying the pools of the given components in any
+ * way invalidates all the iterators.
+ *
+ * @warning
+ * Lifetime of an observer doesn't necessarily have to overcome that of the
+ * registry to which it is connected. However, the observer must be disconnected
+ * from the registry before being destroyed to avoid crashes due to dangling
+ * pointers.
+ *
+ * @tparam Registry Basic registry type.
+ * @tparam Mask Mask type.
+ * @tparam Allocator Type of allocator used to manage memory and elements.
+ */
+template<typename Registry, typename Mask, typename Allocator>
+class basic_observer: private basic_storage<Mask, typename Registry::entity_type, Allocator> {
+    using base_type = basic_storage<Mask, typename Registry::entity_type, Allocator>;
+
+    template<typename>
+    struct matcher_handler;
+
+    template<typename... Reject, typename... Require, typename AnyOf>
+    struct matcher_handler<matcher<type_list<Reject...>, type_list<Require...>, AnyOf>> {
+        template<std::size_t Index>
+        static void maybe_valid_if(basic_observer &obs, Registry &reg, const typename Registry::entity_type entt) {
+            if(reg.template all_of<Require...>(entt) && !reg.template any_of<Reject...>(entt)) {
+                if(!obs.contains(entt)) {
+                    obs.emplace(entt);
+                }
+
+                obs.get(entt) |= (1 << Index);
+            }
+        }
+
+        template<std::size_t Index>
+        static void discard_if(basic_observer &obs, Registry &, const typename Registry::entity_type entt) {
+            if(obs.contains(entt) && !(obs.get(entt) &= (~(1 << Index)))) {
+                obs.erase(entt);
+            }
+        }
+
+        template<std::size_t Index>
+        static void connect(basic_observer &obs, Registry &reg) {
+            (reg.template on_destroy<Require>().template connect<&discard_if<Index>>(obs), ...);
+            (reg.template on_construct<Reject>().template connect<&discard_if<Index>>(obs), ...);
+            reg.template on_update<AnyOf>().template connect<&maybe_valid_if<Index>>(obs);
+            reg.template on_destroy<AnyOf>().template connect<&discard_if<Index>>(obs);
+        }
+
+        static void disconnect(basic_observer &obs, Registry &reg) {
+            (reg.template on_destroy<Require>().disconnect(&obs), ...);
+            (reg.template on_construct<Reject>().disconnect(&obs), ...);
+            reg.template on_update<AnyOf>().disconnect(&obs);
+            reg.template on_destroy<AnyOf>().disconnect(&obs);
+        }
+    };
+
+    template<typename... Reject, typename... Require, typename... NoneOf, typename... AllOf>
+    struct matcher_handler<matcher<type_list<Reject...>, type_list<Require...>, type_list<NoneOf...>, AllOf...>> {
+        template<std::size_t Index, typename... Ignore>
+        static void maybe_valid_if(basic_observer &obs, Registry &reg, const typename Registry::entity_type entt) {
+            auto condition = [&reg, entt]() {
+                if constexpr(sizeof...(Ignore) == 0) {
+                    return reg.template all_of<AllOf..., Require...>(entt) && !reg.template any_of<NoneOf..., Reject...>(entt);
+                } else {
+                    return reg.template all_of<AllOf..., Require...>(entt) && ((std::is_same_v<Ignore..., NoneOf> || !reg.template any_of<NoneOf>(entt)) && ...) && !reg.template any_of<Reject...>(entt);
+                }
+            };
+
+            if(condition()) {
+                if(!obs.contains(entt)) {
+                    obs.emplace(entt);
+                }
+
+                obs.get(entt) |= (1 << Index);
+            }
+        }
+
+        template<std::size_t Index>
+        static void discard_if(basic_observer &obs, Registry &, const typename Registry::entity_type entt) {
+            if(obs.contains(entt) && !(obs.get(entt) &= (~(1 << Index)))) {
+                obs.erase(entt);
+            }
+        }
+
+        template<std::size_t Index>
+        static void connect(basic_observer &obs, Registry &reg) {
+            (reg.template on_destroy<Require>().template connect<&discard_if<Index>>(obs), ...);
+            (reg.template on_construct<Reject>().template connect<&discard_if<Index>>(obs), ...);
+            (reg.template on_construct<AllOf>().template connect<&maybe_valid_if<Index>>(obs), ...);
+            (reg.template on_destroy<NoneOf>().template connect<&maybe_valid_if<Index, NoneOf>>(obs), ...);
+            (reg.template on_destroy<AllOf>().template connect<&discard_if<Index>>(obs), ...);
+            (reg.template on_construct<NoneOf>().template connect<&discard_if<Index>>(obs), ...);
+        }
+
+        static void disconnect(basic_observer &obs, Registry &reg) {
+            (reg.template on_destroy<Require>().disconnect(&obs), ...);
+            (reg.template on_construct<Reject>().disconnect(&obs), ...);
+            (reg.template on_construct<AllOf>().disconnect(&obs), ...);
+            (reg.template on_destroy<NoneOf>().disconnect(&obs), ...);
+            (reg.template on_destroy<AllOf>().disconnect(&obs), ...);
+            (reg.template on_construct<NoneOf>().disconnect(&obs), ...);
+        }
+    };
+
+    template<typename... Matcher>
+    static void disconnect(Registry &reg, basic_observer &obs) {
+        (matcher_handler<Matcher>::disconnect(obs, reg), ...);
+    }
+
+    template<typename... Matcher, std::size_t... Index>
+    void connect(Registry &reg, std::index_sequence<Index...>) {
+        static_assert(sizeof...(Matcher) < std::numeric_limits<typename base_type::value_type>::digits, "Too many matchers");
+        (matcher_handler<Matcher>::template connect<Index>(*this, reg), ...);
+        release.template connect<&basic_observer::disconnect<Matcher...>>(reg);
+    }
+
+public:
+    /*! Basic registry type. */
+    using registry_type = Registry;
+    /*! @brief Underlying entity identifier. */
+    using entity_type = typename registry_type::entity_type;
+    /*! @brief Unsigned integer type. */
+    using size_type = std::size_t;
+    /*! @brief Allocator type. */
+    using allocator_type = Allocator;
+    /*! @brief Random access iterator type. */
+    using iterator = typename registry_type::common_type::iterator;
+
+    /*! @brief Default constructor. */
+    basic_observer()
+        : basic_observer{allocator_type{}} {}
+
+    /**
+     * @brief Constructs an empty storage with a given allocator.
+     * @param allocator The allocator to use.
+     */
+    explicit basic_observer(const allocator_type &allocator)
+        : base_type{allocator},
+          release{} {}
+
+    /*! @brief Default copy constructor, deleted on purpose. */
+    basic_observer(const basic_observer &) = delete;
+
+    /*! @brief Default move constructor, deleted on purpose. */
+    basic_observer(basic_observer &&) = delete;
+
+    /**
+     * @brief Creates an observer and connects it to a given registry.
+     * @tparam Matcher Types of matchers to use to initialize the observer.
+     * @param reg A valid reference to a registry.
+     * @param allocator The allocator to use.
+     */
+    template<typename... Matcher>
+    basic_observer(registry_type &reg, basic_collector<Matcher...>, const allocator_type &allocator = allocator_type{})
+        : basic_observer{allocator} {
+        connect<Matcher...>(reg, std::index_sequence_for<Matcher...>{});
+    }
+
+    /**
+     * @brief Default copy assignment operator, deleted on purpose.
+     * @return This observer.
+     */
+    basic_observer &operator=(const basic_observer &) = delete;
+
+    /**
+     * @brief Default move assignment operator, deleted on purpose.
+     * @return This observer.
+     */
+    basic_observer &operator=(basic_observer &&) = delete;
+
+    /**
+     * @brief Connects an observer to a given registry.
+     * @tparam Matcher Types of matchers to use to initialize the observer.
+     * @param reg A valid reference to a registry.
+     */
+    template<typename... Matcher>
+    void connect(registry_type &reg, basic_collector<Matcher...>) {
+        disconnect();
+        connect<Matcher...>(reg, std::index_sequence_for<Matcher...>{});
+        base_type::clear();
+    }
+
+    /*! @brief Disconnects an observer from the registry it keeps track of. */
+    void disconnect() {
+        if(release) {
+            release(*this);
+            release.reset();
+        }
+    }
+
+    /**
+     * @brief Returns the number of elements in an observer.
+     * @return Number of elements.
+     */
+    [[nodiscard]] size_type size() const noexcept {
+        return base_type::size();
+    }
+
+    /**
+     * @brief Checks whether an observer is empty.
+     * @return True if the observer is empty, false otherwise.
+     */
+    [[nodiscard]] bool empty() const noexcept {
+        return base_type::empty();
+    }
+
+    /**
+     * @brief Direct access to the list of entities of the observer.
+     *
+     * The returned pointer is such that range `[data(), data() + size())` is
+     * always a valid range, even if the container is empty.
+     *
+     * @note
+     * Entities are in the reverse order as returned by the `begin`/`end`
+     * iterators.
+     *
+     * @return A pointer to the array of entities.
+     */
+    [[nodiscard]] const entity_type *data() const noexcept {
+        return base_type::data();
+    }
+
+    /**
+     * @brief Returns an iterator to the first entity of the observer.
+     *
+     * If the observer is empty, the returned iterator will be equal to `end()`.
+     *
+     * @return An iterator to the first entity of the observer.
+     */
+    [[nodiscard]] iterator begin() const noexcept {
+        return base_type::base_type::begin();
+    }
+
+    /**
+     * @brief Returns an iterator that is past the last entity of the observer.
+     * @return An iterator to the entity following the last entity of the
+     * observer.
+     */
+    [[nodiscard]] iterator end() const noexcept {
+        return base_type::base_type::end();
+    }
+
+    /*! @brief Clears the underlying container. */
+    void clear() noexcept {
+        base_type::clear();
+    }
+
+    /**
+     * @brief Iterates entities and applies the given function object to them.
+     *
+     * The function object is invoked for each entity.<br/>
+     * The signature of the function must be equivalent to the following form:
+     *
+     * @code{.cpp}
+     * void(const entity_type);
+     * @endcode
+     *
+     * @tparam Func Type of the function object to invoke.
+     * @param func A valid function object.
+     */
+    template<typename Func>
+    void each(Func func) const {
+        for(const auto entity: *this) {
+            func(entity);
+        }
+    }
+
+    /**
+     * @brief Iterates entities and applies the given function object to them,
+     * then clears the observer.
+     *
+     * @sa each
+     *
+     * @tparam Func Type of the function object to invoke.
+     * @param func A valid function object.
+     */
+    template<typename Func>
+    void each(Func func) {
+        std::as_const(*this).each(std::move(func));
+        clear();
+    }
+
+private:
+    delegate<void(basic_observer &)> release;
+};
+
+} // namespace entt
+
+#endif

src/entt/entity/organizer.hpp

@@ -15,7 +15,11 @@
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 template<typename>
@@ -27,15 +31,6 @@ struct is_view<basic_view<Args...>>: std::true_type {};
 template<typename Type>
 inline constexpr bool is_view_v = is_view<Type>::value;
 
-template<typename>
-struct is_group: std::false_type {};
-
-template<typename... Args>
-struct is_group<basic_group<Args...>>: std::true_type {};
-
-template<typename Type>
-inline constexpr bool is_group_v = is_group<Type>::value;
-
 template<typename Type, typename Override>
 struct unpack_type {
     using ro = std::conditional_t<
@@ -61,24 +56,14 @@ struct unpack_type<const basic_registry<Args...>, type_list<Override...>>
 
 template<typename... Get, typename... Exclude, typename... Override>
 struct unpack_type<basic_view<get_t<Get...>, exclude_t<Exclude...>>, type_list<Override...>> {
-    using ro = type_list_cat_t<type_list<typename Exclude::element_type...>, typename unpack_type<constness_as_t<typename Get::element_type, Get>, type_list<Override...>>::ro...>;
-    using rw = type_list_cat_t<typename unpack_type<constness_as_t<typename Get::element_type, Get>, type_list<Override...>>::rw...>;
+    using ro = type_list_cat_t<type_list<typename Exclude::value_type...>, typename unpack_type<constness_as_t<typename Get::value_type, Get>, type_list<Override...>>::ro...>;
+    using rw = type_list_cat_t<typename unpack_type<constness_as_t<typename Get::value_type, Get>, type_list<Override...>>::rw...>;
 };
 
 template<typename... Get, typename... Exclude, typename... Override>
 struct unpack_type<const basic_view<get_t<Get...>, exclude_t<Exclude...>>, type_list<Override...>>
     : unpack_type<basic_view<get_t<Get...>, exclude_t<Exclude...>>, type_list<Override...>> {};
 
-template<typename... Owned, typename... Get, typename... Exclude, typename... Override>
-struct unpack_type<basic_group<owned_t<Owned...>, get_t<Get...>, exclude_t<Exclude...>>, type_list<Override...>> {
-    using ro = type_list_cat_t<type_list<typename Exclude::element_type...>, typename unpack_type<constness_as_t<typename Get::element_type, Get>, type_list<Override...>>::ro..., typename unpack_type<constness_as_t<typename Owned::element_type, Owned>, type_list<Override...>>::ro...>;
-    using rw = type_list_cat_t<typename unpack_type<constness_as_t<typename Get::element_type, Get>, type_list<Override...>>::rw..., typename unpack_type<constness_as_t<typename Owned::element_type, Owned>, type_list<Override...>>::rw...>;
-};
-
-template<typename... Owned, typename... Get, typename... Exclude, typename... Override>
-struct unpack_type<const basic_group<owned_t<Owned...>, get_t<Get...>, exclude_t<Exclude...>>, type_list<Override...>>
-    : unpack_type<basic_group<owned_t<Owned...>, get_t<Get...>, exclude_t<Exclude...>>, type_list<Override...>> {};
-
 template<typename, typename>
 struct resource_traits;
 
@@ -102,7 +87,11 @@ template<typename... Req, typename Ret, typename Class, typename... Args>
 resource_traits<type_list<std::remove_reference_t<Args>...>, type_list<Req...>> constrained_function_to_resource_traits(Ret (Class::*)(Args...) const);
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /**
  * @brief Utility class for creating a static task graph.
@@ -127,7 +116,7 @@ class basic_organizer final {
         const char *name{};
         const void *payload{};
         callback_type *callback{};
-        dependency_type *dependency{};
+        dependency_type *dependency;
         prepare_type *prepare{};
         const type_info *info{};
     };
@@ -138,8 +127,6 @@ class basic_organizer final {
             return reg;
         } else if constexpr(internal::is_view_v<Type>) {
             return static_cast<Type>(as_view{reg});
-        } else if constexpr(internal::is_group_v<Type>) {
-            return static_cast<Type>(as_group{reg});
         } else {
             return reg.ctx().template emplace<std::remove_reference_t<Type>>();
         }
@@ -151,16 +138,14 @@ class basic_organizer final {
     }
 
     template<typename... Type>
-    [[nodiscard]] static std::size_t fill_dependencies(type_list<Type...>, [[maybe_unused]] const type_info **buffer, [[maybe_unused]] const std::size_t count) {
+    static std::size_t fill_dependencies(type_list<Type...>, [[maybe_unused]] const type_info **buffer, [[maybe_unused]] const std::size_t count) {
         if constexpr(sizeof...(Type) == 0u) {
             return {};
         } else {
-            // NOLINTNEXTLINE(cppcoreguidelines-avoid-c-arrays, modernize-avoid-c-arrays)
-            const type_info *info[]{&type_id<Type>()...};
+            const type_info *info[sizeof...(Type)]{&type_id<Type>()...};
             const auto length = count < sizeof...(Type) ? count : sizeof...(Type);
 
             for(std::size_t pos{}; pos < length; ++pos) {
-                // NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-pointer-arithmetic)
                 buffer[pos] = info[pos];
             }
 
@@ -190,14 +175,14 @@ public:
     struct vertex {
         /**
          * @brief Constructs a vertex of the task graph.
+         * @param vtype True if the vertex is a top-level one, false otherwise.
          * @param data The data associated with the vertex.
-         * @param from List of in-edges of the vertex.
-         * @param to List of out-edges of the vertex.
+         * @param edges The indices of the children in the adjacency list.
          */
-        vertex(vertex_data data, std::vector<std::size_t> from, std::vector<std::size_t> to)
-            : node{std::move(data)},
-              in{std::move(from)},
-              out{std::move(to)} {}
+        vertex(const bool vtype, vertex_data data, std::vector<std::size_t> edges)
+            : is_top_level{vtype},
+              node{std::move(data)},
+              reachable{std::move(edges)} {}
 
         /**
          * @brief Fills a buffer with the type info objects for the writable
@@ -206,7 +191,7 @@ public:
          * @param length The length of the user-supplied buffer.
          * @return The number of type info objects written to the buffer.
          */
-        [[nodiscard]] size_type ro_dependency(const type_info **buffer, const std::size_t length) const noexcept {
+        size_type ro_dependency(const type_info **buffer, const std::size_t length) const noexcept {
             return node.dependency(false, buffer, length);
         }
 
@@ -217,7 +202,7 @@ public:
          * @param length The length of the user-supplied buffer.
          * @return The number of type info objects written to the buffer.
          */
-        [[nodiscard]] size_type rw_dependency(const type_info **buffer, const std::size_t length) const noexcept {
+        size_type rw_dependency(const type_info **buffer, const std::size_t length) const noexcept {
             return node.dependency(true, buffer, length);
         }
 
@@ -225,7 +210,7 @@ public:
          * @brief Returns the number of read-only resources of a vertex.
          * @return The number of read-only resources of the vertex.
          */
-        [[nodiscard]] size_type ro_count() const noexcept {
+        size_type ro_count() const noexcept {
             return node.ro_count;
         }
 
@@ -233,7 +218,7 @@ public:
          * @brief Returns the number of writable resources of a vertex.
          * @return The number of writable resources of the vertex.
          */
-        [[nodiscard]] size_type rw_count() const noexcept {
+        size_type rw_count() const noexcept {
             return node.rw_count;
         }
 
@@ -241,15 +226,15 @@ public:
          * @brief Checks if a vertex is also a top-level one.
          * @return True if the vertex is a top-level one, false otherwise.
          */
-        [[nodiscard]] bool top_level() const noexcept {
-            return in.empty();
+        bool top_level() const noexcept {
+            return is_top_level;
         }
 
         /**
          * @brief Returns a type info object associated with a vertex.
          * @return A properly initialized type info object.
          */
-        [[nodiscard]] const type_info &info() const noexcept {
+        const type_info &info() const noexcept {
             return *node.info;
         }
 
@@ -257,7 +242,7 @@ public:
          * @brief Returns a user defined name associated with a vertex, if any.
          * @return The user defined name associated with the vertex, if any.
          */
-        [[nodiscard]] const char *name() const noexcept {
+        const char *name() const noexcept {
             return node.name;
         }
 
@@ -265,7 +250,7 @@ public:
          * @brief Returns the function associated with a vertex.
          * @return The function associated with the vertex.
          */
-        [[nodiscard]] function_type *callback() const noexcept {
+        function_type *callback() const noexcept {
             return node.callback;
         }
 
@@ -273,24 +258,16 @@ public:
          * @brief Returns the payload associated with a vertex, if any.
          * @return The payload associated with the vertex, if any.
          */
-        [[nodiscard]] const void *data() const noexcept {
+        const void *data() const noexcept {
             return node.payload;
         }
 
         /**
-         * @brief Returns the list of in-edges of a vertex.
-         * @return The list of in-edges of a vertex.
+         * @brief Returns the list of nodes reachable from a given vertex.
+         * @return The list of nodes reachable from the vertex.
          */
-        [[nodiscard]] const std::vector<std::size_t> &in_edges() const noexcept {
-            return in;
-        }
-
-        /**
-         * @brief Returns the list of out-edges of a vertex.
-         * @return The list of out-edges of a vertex.
-         */
-        [[nodiscard]] const std::vector<std::size_t> &out_edges() const noexcept {
-            return out;
+        const std::vector<std::size_t> &children() const noexcept {
+            return reachable;
         }
 
         /**
@@ -303,9 +280,9 @@ public:
         }
 
     private:
+        bool is_top_level;
         vertex_data node;
-        std::vector<std::size_t> in;
-        std::vector<std::size_t> out;
+        std::vector<std::size_t> reachable;
     };
 
     /**
@@ -400,24 +377,20 @@ public:
      * @brief Generates a task graph for the current content.
      * @return The adjacency list of the task graph.
      */
-    [[nodiscard]] std::vector<vertex> graph() {
+    std::vector<vertex> graph() {
         std::vector<vertex> adjacency_list{};
         adjacency_list.reserve(vertices.size());
         auto adjacency_matrix = builder.graph();
 
         for(auto curr: adjacency_matrix.vertices()) {
-            std::vector<std::size_t> in{};
-            std::vector<std::size_t> out{};
-
-            for(auto &&edge: adjacency_matrix.in_edges(curr)) {
-                in.push_back(edge.first);
-            }
+            const auto iterable = adjacency_matrix.in_edges(curr);
+            std::vector<std::size_t> reachable{};
 
             for(auto &&edge: adjacency_matrix.out_edges(curr)) {
-                out.push_back(edge.second);
+                reachable.push_back(edge.second);
             }
 
-            adjacency_list.emplace_back(vertices[curr], std::move(in), std::move(out));
+            adjacency_list.emplace_back(iterable.cbegin() == iterable.cend(), vertices[curr], std::move(reachable));
         }
 
         return adjacency_list;

src/entt/entity/ranges.hpp

@@ -1,26 +0,0 @@
-#ifndef ENTT_ENTITY_RANGES_HPP
-#define ENTT_ENTITY_RANGES_HPP
-
-#if __has_include(<version>)
-#    include <version>
-#
-#    if defined(__cpp_lib_ranges)
-#        include <ranges>
-#        include "fwd.hpp"
-
-template<class... Args>
-inline constexpr bool std::ranges::enable_borrowed_range<entt::basic_view<Args...>>{true};
-
-template<class... Args>
-inline constexpr bool std::ranges::enable_borrowed_range<entt::basic_group<Args...>>{true};
-
-template<class... Args>
-inline constexpr bool std::ranges::enable_view<entt::basic_view<Args...>>{true};
-
-template<class... Args>
-inline constexpr bool std::ranges::enable_view<entt::basic_group<Args...>>{true};
-
-#    endif
-#endif
-
-#endif

src/entt/entity/runtime_view.hpp

@@ -11,13 +11,16 @@
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 template<typename Set>
 class runtime_view_iterator final {
     using iterator_type = typename Set::iterator;
-    using iterator_traits = std::iterator_traits<iterator_type>;
 
     [[nodiscard]] bool valid() const {
         return (!tombstone_check || *it != tombstone)
@@ -26,10 +29,10 @@ class runtime_view_iterator final {
     }
 
 public:
-    using value_type = typename iterator_traits::value_type;
-    using pointer = typename iterator_traits::pointer;
-    using reference = typename iterator_traits::reference;
-    using difference_type = typename iterator_traits::difference_type;
+    using difference_type = typename iterator_type::difference_type;
+    using value_type = typename iterator_type::value_type;
+    using pointer = typename iterator_type::pointer;
+    using reference = typename iterator_type::reference;
     using iterator_category = std::bidirectional_iterator_tag;
 
     constexpr runtime_view_iterator() noexcept
@@ -38,7 +41,6 @@ public:
           it{},
           tombstone_check{} {}
 
-    // NOLINTNEXTLINE(bugprone-easily-swappable-parameters)
     runtime_view_iterator(const std::vector<Set *> &cpools, const std::vector<Set *> &ignore, iterator_type curr) noexcept
         : pools{&cpools},
           filter{&ignore},
@@ -50,24 +52,22 @@ public:
     }
 
     runtime_view_iterator &operator++() {
-        ++it;
-        for(const auto last = (*pools)[0]->end(); it != last && !valid(); ++it) {}
+        while(++it != (*pools)[0]->end() && !valid()) {}
         return *this;
     }
 
     runtime_view_iterator operator++(int) {
-        const runtime_view_iterator orig = *this;
+        runtime_view_iterator orig = *this;
         return ++(*this), orig;
     }
 
     runtime_view_iterator &operator--() {
-        --it;
-        for(const auto first = (*pools)[0]->begin(); it != first && !valid(); --it) {}
+        while(--it != (*pools)[0]->begin() && !valid()) {}
         return *this;
     }
 
     runtime_view_iterator operator--(int) {
-        const runtime_view_iterator orig = *this;
+        runtime_view_iterator orig = *this;
         return operator--(), orig;
     }
 
@@ -95,22 +95,26 @@ private:
 };
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /**
  * @brief Generic runtime view.
  *
  * Runtime views iterate over those entities that are at least in the given
  * storage. During initialization, a runtime view looks at the number of
- * entities available for each element and uses the smallest set in order to get
- * a performance boost when iterating.
+ * entities available for each component and uses the smallest set in order to
+ * get a performance boost when iterating.
  *
  * @b Important
  *
  * Iterators aren't invalidated if:
  *
  * * New elements are added to the storage.
- * * The entity currently pointed is modified (for example, elements are added
+ * * The entity currently pointed is modified (for example, components are added
  *   or removed from it).
  * * The entity currently pointed is destroyed.
  *
@@ -163,7 +167,7 @@ public:
           filter{other.filter, allocator} {}
 
     /*! @brief Default move constructor. */
-    basic_runtime_view(basic_runtime_view &&) noexcept = default;
+    basic_runtime_view(basic_runtime_view &&) noexcept(std::is_nothrow_move_constructible_v<container_type>) = default;
 
     /**
      * @brief Allocator-extended move constructor.
@@ -174,26 +178,23 @@ public:
         : pools{std::move(other.pools), allocator},
           filter{std::move(other.filter), allocator} {}
 
-    /*! @brief Default destructor. */
-    ~basic_runtime_view() = default;
-
     /**
      * @brief Default copy assignment operator.
-     * @return This runtime view.
+     * @return This container.
      */
     basic_runtime_view &operator=(const basic_runtime_view &) = default;
 
     /**
      * @brief Default move assignment operator.
-     * @return This runtime view.
+     * @return This container.
      */
-    basic_runtime_view &operator=(basic_runtime_view &&) noexcept = default;
+    basic_runtime_view &operator=(basic_runtime_view &&) noexcept(std::is_nothrow_move_assignable_v<container_type>) = default;
 
     /**
      * @brief Exchanges the contents with those of a given view.
      * @param other View to exchange the content with.
      */
-    void swap(basic_runtime_view &other) noexcept {
+    void swap(basic_runtime_view &other) {
         using std::swap;
         swap(pools, other.pools);
         swap(filter, other.filter);
@@ -248,11 +249,11 @@ public:
 
     /**
      * @brief Returns an iterator to the first entity that has the given
-     * elements.
+     * components.
      *
      * If the view is empty, the returned iterator will be equal to `end()`.
      *
-     * @return An iterator to the first entity that has the given elements.
+     * @return An iterator to the first entity that has the given components.
      */
     [[nodiscard]] iterator begin() const {
         return pools.empty() ? iterator{} : iterator{pools, filter, pools[0]->begin()};
@@ -260,22 +261,14 @@ public:
 
     /**
      * @brief Returns an iterator that is past the last entity that has the
-     * given elements.
+     * given components.
      * @return An iterator to the entity following the last entity that has the
-     * given elements.
+     * given components.
      */
     [[nodiscard]] iterator end() const {
         return pools.empty() ? iterator{} : iterator{pools, filter, pools[0]->end()};
     }
 
-    /**
-     * @brief Checks whether a view is initialized or not.
-     * @return True if the view is initialized, false otherwise.
-     */
-    [[nodiscard]] explicit operator bool() const noexcept {
-        return !(pools.empty() && filter.empty());
-    }
-
     /**
      * @brief Checks if a view contains an entity.
      * @param entt A valid identifier.

src/entt/entity/snapshot.hpp

@@ -16,28 +16,36 @@
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 template<typename Registry>
 void orphans(Registry &registry) {
-    auto &storage = registry.template storage<typename Registry::entity_type>();
+    auto view = registry.template view<typename Registry::entity_type>();
 
-    for(auto entt: storage) {
+    for(auto entt: view) {
         if(registry.orphan(entt)) {
-            storage.erase(entt);
+            view.storage()->erase(entt);
         }
     }
 }
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /**
  * @brief Utility class to create snapshots from a registry.
  *
  * A _snapshot_ can be either a dump of the entire registry or a narrower
- * selection of elements of interest.<br/>
+ * selection of components of interest.<br/>
  * This type can be used in both cases if provided with a correctly configured
  * output archive.
  *
@@ -46,7 +54,7 @@ void orphans(Registry &registry) {
 template<typename Registry>
 class basic_snapshot {
     static_assert(!std::is_const_v<Registry>, "Non-const registry type required");
-    using traits_type = entt_traits<typename Registry::entity_type>;
+    using traits_type = typename Registry::traits_type;
 
 public:
     /*! Basic registry type. */
@@ -61,25 +69,10 @@ public:
     basic_snapshot(const registry_type &source) noexcept
         : reg{&source} {}
 
-    /*! @brief Default copy constructor, deleted on purpose. */
-    basic_snapshot(const basic_snapshot &) = delete;
-
     /*! @brief Default move constructor. */
     basic_snapshot(basic_snapshot &&) noexcept = default;
 
-    /*! @brief Default destructor. */
-    ~basic_snapshot() = default;
-
-    /**
-     * @brief Default copy assignment operator, deleted on purpose.
-     * @return This snapshot.
-     */
-    basic_snapshot &operator=(const basic_snapshot &) = delete;
-
-    /**
-     * @brief Default move assignment operator.
-     * @return This snapshot.
-     */
+    /*! @brief Default move assignment operator. @return This snapshot. */
     basic_snapshot &operator=(basic_snapshot &&) noexcept = default;
 
     /**
@@ -93,25 +86,14 @@ public:
     template<typename Type, typename Archive>
     const basic_snapshot &get(Archive &archive, const id_type id = type_hash<Type>::value()) const {
         if(const auto *storage = reg->template storage<Type>(id); storage) {
-            const typename registry_type::common_type &base = *storage;
-
             archive(static_cast<typename traits_type::entity_type>(storage->size()));
 
             if constexpr(std::is_same_v<Type, entity_type>) {
-                archive(static_cast<typename traits_type::entity_type>(storage->free_list()));
+                archive(static_cast<typename traits_type::entity_type>(storage->in_use()));
 
-                for(auto first = base.rbegin(), last = base.rend(); first != last; ++first) {
+                for(auto first = storage->data(), last = first + storage->size(); first != last; ++first) {
                     archive(*first);
                 }
-            } else if constexpr(registry_type::template storage_for_type<Type>::storage_policy == deletion_policy::in_place) {
-                for(auto it = base.rbegin(), last = base.rend(); it != last; ++it) {
-                    if(const auto entt = *it; entt == tombstone) {
-                        archive(static_cast<entity_type>(null));
-                    } else {
-                        archive(entt);
-                        std::apply([&archive](auto &&...args) { (archive(std::forward<decltype(args)>(args)), ...); }, storage->get_as_tuple(entt));
-                    }
-                }
             } else {
                 for(auto elem: storage->reach()) {
                     std::apply([&archive](auto &&...args) { (archive(std::forward<decltype(args)>(args)), ...); }, elem);
@@ -158,6 +140,45 @@ public:
         return *this;
     }
 
+    /**
+     * @brief Serializes all identifiers, including those to be recycled.
+     * @tparam Archive Type of output archive.
+     * @param archive A valid reference to an output archive.
+     * @return An object of this type to continue creating the snapshot.
+     */
+    template<typename Archive>
+    [[deprecated("use .get<Entity>(archive) instead")]] const basic_snapshot &entities(Archive &archive) const {
+        return get<entity_type>(archive);
+    }
+
+    /**
+     * @brief Serializes all elements of a type with associated identifiers.
+     * @tparam Component Types of components to serialize.
+     * @tparam Archive Type of output archive.
+     * @param archive A valid reference to an output archive.
+     * @return An object of this type to continue creating the snapshot.
+     */
+    template<typename... Component, typename Archive>
+    [[deprecated("use .get<Type>(archive) instead")]] const basic_snapshot &component(Archive &archive) const {
+        return (get<Component>(archive), ...);
+    }
+
+    /**
+     * @brief Serializes all elements of a type with associated identifiers for
+     * the entities in a range.
+     * @tparam Component Types of components to serialize.
+     * @tparam Archive Type of output archive.
+     * @tparam It Type of input iterator.
+     * @param archive A valid reference to an output archive.
+     * @param first An iterator to the first element of the range to serialize.
+     * @param last An iterator past the last element of the range to serialize.
+     * @return An object of this type to continue creating the snapshot.
+     */
+    template<typename... Component, typename Archive, typename It>
+    [[deprecated("use .get<Type>(archive, first, last) instead")]] const basic_snapshot &component(Archive &archive, It first, It last) const {
+        return (get<Component>(archive, first, last), ...);
+    }
+
 private:
     const registry_type *reg;
 };
@@ -175,7 +196,7 @@ private:
 template<typename Registry>
 class basic_snapshot_loader {
     static_assert(!std::is_const_v<Registry>, "Non-const registry type required");
-    using traits_type = entt_traits<typename Registry::entity_type>;
+    using traits_type = typename Registry::traits_type;
 
 public:
     /*! Basic registry type. */
@@ -190,28 +211,15 @@ public:
     basic_snapshot_loader(registry_type &source) noexcept
         : reg{&source} {
         // restoring a snapshot as a whole requires a clean registry
-        ENTT_ASSERT(reg->template storage<entity_type>().free_list() == 0u, "Registry must be empty");
+        for([[maybe_unused]] auto elem: source.storage()) {
+            ENTT_ASSERT(elem.second.empty(), "Registry must be empty");
+        }
     }
 
-    /*! @brief Default copy constructor, deleted on purpose. */
-    basic_snapshot_loader(const basic_snapshot_loader &) = delete;
-
     /*! @brief Default move constructor. */
     basic_snapshot_loader(basic_snapshot_loader &&) noexcept = default;
 
-    /*! @brief Default destructor. */
-    ~basic_snapshot_loader() = default;
-
-    /**
-     * @brief Default copy assignment operator, deleted on purpose.
-     * @return This loader.
-     */
-    basic_snapshot_loader &operator=(const basic_snapshot_loader &) = delete;
-
-    /**
-     * @brief Default move assignment operator.
-     * @return This loader.
-     */
+    /*! @brief Default move assignment operator. @return This loader. */
     basic_snapshot_loader &operator=(basic_snapshot_loader &&) noexcept = default;
 
     /**
@@ -223,37 +231,34 @@ public:
      * @return A valid loader to continue restoring data.
      */
     template<typename Type, typename Archive>
-    basic_snapshot_loader &get(Archive &archive, const id_type id = type_hash<Type>::value()) {
+    basic_snapshot_loader &get([[maybe_unused]] Archive &archive, const id_type id = type_hash<Type>::value()) {
         auto &storage = reg->template storage<Type>(id);
         typename traits_type::entity_type length{};
 
         archive(length);
 
         if constexpr(std::is_same_v<Type, entity_type>) {
-            typename traits_type::entity_type count{};
-            entity_type placeholder{};
+            typename traits_type::entity_type in_use{};
 
             storage.reserve(length);
-            archive(count);
+            archive(in_use);
 
             for(entity_type entity = null; length; --length) {
                 archive(entity);
-                storage.generate(entity);
-                placeholder = (entity > placeholder) ? entity : placeholder;
+                storage.emplace(entity);
             }
 
-            storage.start_from(traits_type::next(placeholder));
-            storage.free_list(count);
+            storage.in_use(in_use);
         } else {
             auto &other = reg->template storage<entity_type>();
             entity_type entt{null};
 
             while(length--) {
                 if(archive(entt); entt != null) {
-                    const auto entity = other.contains(entt) ? entt : other.generate(entt);
+                    const auto entity = other.contains(entt) ? entt : other.emplace(entt);
                     ENTT_ASSERT(entity == entt, "Entity not available for use");
 
-                    if constexpr(std::tuple_size_v<decltype(storage.get_as_tuple({}))> == 0u) {
+                    if constexpr(Registry::template storage_for_type<Type>::traits_type::page_size == 0u) {
                         storage.emplace(entity);
                     } else {
                         Type elem{};
@@ -268,10 +273,37 @@ public:
     }
 
     /**
-     * @brief Destroys those entities that have no elements.
+     * @brief Restores all identifiers, including those to be recycled.
+     * @tparam Archive Type of input archive.
+     * @param archive A valid reference to an input archive.
+     * @return A valid loader to continue restoring data.
+     */
+    template<typename Archive>
+    [[deprecated("use .get<Entity>(archive) instead")]] basic_snapshot_loader &entities(Archive &archive) {
+        return get<entity_type>(archive);
+    }
+
+    /**
+     * @brief Restores all elements of a type with associated identifiers.
      *
-     * In case all the entities were serialized but only part of the elements
-     * was saved, it could happen that some of the entities have no elements
+     * The template parameter list must be exactly the same used during
+     * serialization.
+     *
+     * @tparam Component Type of component to restore.
+     * @tparam Archive Type of input archive.
+     * @param archive A valid reference to an input archive.
+     * @return A valid loader to continue restoring data.
+     */
+    template<typename... Component, typename Archive>
+    [[deprecated("use .get<Type>(archive) instead")]] basic_snapshot_loader &component(Archive &archive) {
+        return (get<Component>(archive), ...);
+    }
+
+    /**
+     * @brief Destroys those entities that have no components.
+     *
+     * In case all the entities were serialized but only part of the components
+     * was saved, it could happen that some of the entities have no components
      * once restored.<br/>
      * This function helps to identify and destroy those entities.
      *
@@ -305,7 +337,7 @@ private:
 template<typename Registry>
 class basic_continuous_loader {
     static_assert(!std::is_const_v<Registry>, "Non-const registry type required");
-    using traits_type = entt_traits<typename Registry::entity_type>;
+    using traits_type = typename Registry::traits_type;
 
     void restore(typename Registry::entity_type entt) {
         if(const auto entity = to_entity(entt); remloc.contains(entity) && remloc[entity].first == entt) {
@@ -376,26 +408,11 @@ public:
         : remloc{source.get_allocator()},
           reg{&source} {}
 
-    /*! @brief Default copy constructor, deleted on purpose. */
-    basic_continuous_loader(const basic_continuous_loader &) = delete;
-
     /*! @brief Default move constructor. */
-    basic_continuous_loader(basic_continuous_loader &&) noexcept = default;
+    basic_continuous_loader(basic_continuous_loader &&) = default;
 
-    /*! @brief Default destructor. */
-    ~basic_continuous_loader() = default;
-
-    /**
-     * @brief Default copy assignment operator, deleted on purpose.
-     * @return This loader.
-     */
-    basic_continuous_loader &operator=(const basic_continuous_loader &) = delete;
-
-    /**
-     * @brief Default move assignment operator.
-     * @return This loader.
-     */
-    basic_continuous_loader &operator=(basic_continuous_loader &&) noexcept = default;
+    /*! @brief Default move assignment operator. @return This loader. */
+    basic_continuous_loader &operator=(basic_continuous_loader &&) = default;
 
     /**
      * @brief Restores all elements of a type with associated identifiers.
@@ -412,7 +429,7 @@ public:
      * @return A valid loader to continue restoring data.
      */
     template<typename Type, typename Archive>
-    basic_continuous_loader &get(Archive &archive, const id_type id = type_hash<Type>::value()) {
+    basic_continuous_loader &get([[maybe_unused]] Archive &archive, const id_type id = type_hash<Type>::value()) {
         auto &storage = reg->template storage<Type>(id);
         typename traits_type::entity_type length{};
         entity_type entt{null};
@@ -450,7 +467,7 @@ public:
                 if(archive(entt); entt != null) {
                     restore(entt);
 
-                    if constexpr(std::tuple_size_v<decltype(storage.get_as_tuple({}))> == 0u) {
+                    if constexpr(Registry::template storage_for_type<Type>::traits_type::page_size == 0u) {
                         storage.emplace(map(entt));
                     } else {
                         Type elem{};
@@ -465,10 +482,83 @@ public:
     }
 
     /**
-     * @brief Destroys those entities that have no elements.
+     * @brief Restores all identifiers, including those to be recycled.
      *
-     * In case all the entities were serialized but only part of the elements
-     * was saved, it could happen that some of the entities have no elements
+     * It creates local counterparts for remote elements as needed.
+     *
+     * @tparam Archive Type of input archive.
+     * @param archive A valid reference to an input archive.
+     * @return A non-const reference to this loader.
+     */
+    template<typename Archive>
+    [[deprecated("use .get<Entity>(archive) instead")]] basic_continuous_loader &entities(Archive &archive) {
+        return get<entity_type>(archive);
+    }
+
+    /**
+     * @brief Serializes all elements of a type with associated identifiers.
+     *
+     * It creates local counterparts for remote elements as needed.<br/>
+     * Members are either data members of type entity_type or containers of
+     * entities. In both cases, a loader visits them and replaces entities with
+     * their local counterpart.
+     *
+     * @tparam Component Type of component to restore.
+     * @tparam Archive Type of input archive.
+     * @tparam Member Types of members to update with their local counterparts.
+     * @param archive A valid reference to an input archive.
+     * @param member Members to update with their local counterparts.
+     * @return A non-const reference to this loader.
+     */
+    template<typename... Component, typename Archive, typename... Member, typename... Clazz>
+    [[deprecated("use .component<Type>(archive, members...) instead")]] basic_continuous_loader &component(Archive &archive, Member Clazz::*...member) {
+        ([&](auto &storage) {
+            for(auto &&ref: remloc) {
+                storage.remove(ref.second.second);
+            }
+
+            typename traits_type::entity_type length{};
+            entity_type entt{null};
+
+            archive(length);
+
+            while(length--) {
+                if(archive(entt); entt != null) {
+                    restore(entt);
+
+                    if constexpr(std::remove_reference_t<decltype(storage)>::traits_type::page_size == 0u) {
+                        storage.emplace(map(entt));
+                    } else {
+                        typename std::remove_reference_t<decltype(storage)>::value_type elem{};
+                        archive(elem);
+                        (update(elem, member), ...);
+                        storage.emplace(map(entt), std::move(elem));
+                    }
+                }
+            }
+        }(reg->template storage<Component>()),
+         ...);
+
+        return *this;
+    }
+
+    /**
+     * @brief Helps to purge entities that no longer have a counterpart.
+     *
+     * Users should invoke this member function after restoring each snapshot,
+     * unless they know exactly what they are doing.
+     *
+     * @return A non-const reference to this loader.
+     */
+    [[deprecated("use .get<Entity>(archive) instead")]] basic_continuous_loader &shrink() {
+        return *this;
+    }
+
+    /**
+     * @brief Destroys those entities that have no components.
+     *
+     * In case all the entities were serialized but only part of the components
+     * was saved, it could happen that some of the entities have no components
      * once restored.<br/>
      * This function helps to identify and destroy those entities.
      *

src/entt/entity/sparse_set.hpp

@@ -10,14 +10,18 @@
 #include "../config/config.h"
 #include "../core/algorithm.hpp"
 #include "../core/any.hpp"
-#include "../core/bit.hpp"
+#include "../core/memory.hpp"
 #include "../core/type_info.hpp"
 #include "entity.hpp"
 #include "fwd.hpp"
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 template<typename Container>
@@ -33,7 +37,7 @@ struct sparse_set_iterator final {
           offset{} {}
 
     constexpr sparse_set_iterator(const Container &ref, const difference_type idx) noexcept
-        : packed{&ref},
+        : packed{std::addressof(ref)},
           offset{idx} {}
 
     constexpr sparse_set_iterator &operator++() noexcept {
@@ -41,7 +45,7 @@ struct sparse_set_iterator final {
     }
 
     constexpr sparse_set_iterator operator++(int) noexcept {
-        const sparse_set_iterator orig = *this;
+        sparse_set_iterator orig = *this;
         return ++(*this), orig;
     }
 
@@ -50,7 +54,7 @@ struct sparse_set_iterator final {
     }
 
     constexpr sparse_set_iterator operator--(int) noexcept {
-        const sparse_set_iterator orig = *this;
+        sparse_set_iterator orig = *this;
         return operator--(), orig;
     }
 
@@ -73,15 +77,15 @@ struct sparse_set_iterator final {
     }
 
     [[nodiscard]] constexpr reference operator[](const difference_type value) const noexcept {
-        return (*packed)[static_cast<typename Container::size_type>(index() - value)];
+        return packed->data()[index() - value];
     }
 
     [[nodiscard]] constexpr pointer operator->() const noexcept {
-        return std::addressof(operator[](0));
+        return packed->data() + index();
     }
 
     [[nodiscard]] constexpr reference operator*() const noexcept {
-        return operator[](0);
+        return *operator->();
     }
 
     [[nodiscard]] constexpr pointer data() const noexcept {
@@ -133,10 +137,14 @@ template<typename Container>
 }
 
 } // namespace internal
-/*! @endcond */
 
 /**
- * @brief Sparse set implementation.
+ * Internal details not to be documented.
+ * @endcond
+ */
+
+/**
+ * @brief Basic sparse set implementation.
  *
  * Sparse set or packed array or whatever is the name users give it.<br/>
  * Two arrays: an _external_ one and an _internal_ one; a _sparse_ one and a
@@ -160,55 +168,40 @@ class basic_sparse_set {
     static_assert(std::is_same_v<typename alloc_traits::value_type, Entity>, "Invalid value type");
     using sparse_container_type = std::vector<typename alloc_traits::pointer, typename alloc_traits::template rebind_alloc<typename alloc_traits::pointer>>;
     using packed_container_type = std::vector<Entity, Allocator>;
-    using traits_type = entt_traits<Entity>;
-
-    static constexpr auto max_size = static_cast<std::size_t>(traits_type::to_entity(null));
-
-    // it could be auto but gcc complains and emits a warning due to a false positive
-    [[nodiscard]] std::size_t policy_to_head() const noexcept {
-        return static_cast<size_type>(max_size * static_cast<std::remove_const_t<decltype(max_size)>>(mode != deletion_policy::swap_only));
-    }
-
-    [[nodiscard]] auto entity_to_pos(const Entity entt) const noexcept {
-        return static_cast<size_type>(traits_type::to_entity(entt));
-    }
-
-    [[nodiscard]] auto pos_to_page(const std::size_t pos) const noexcept {
-        return static_cast<size_type>(pos / traits_type::page_size);
-    }
 
     [[nodiscard]] auto sparse_ptr(const Entity entt) const {
-        const auto pos = entity_to_pos(entt);
-        const auto page = pos_to_page(pos);
+        const auto pos = static_cast<size_type>(traits_type::to_entity(entt));
+        const auto page = pos / traits_type::page_size;
         return (page < sparse.size() && sparse[page]) ? (sparse[page] + fast_mod(pos, traits_type::page_size)) : nullptr;
     }
 
     [[nodiscard]] auto &sparse_ref(const Entity entt) const {
         ENTT_ASSERT(sparse_ptr(entt), "Invalid element");
-        const auto pos = entity_to_pos(entt);
-        return sparse[pos_to_page(pos)][fast_mod(pos, traits_type::page_size)];
+        const auto pos = static_cast<size_type>(traits_type::to_entity(entt));
+        return sparse[pos / traits_type::page_size][fast_mod(pos, traits_type::page_size)];
     }
 
     [[nodiscard]] auto to_iterator(const Entity entt) const {
-        return --(end() - static_cast<difference_type>(index(entt)));
+        return --(end() - index(entt));
     }
 
     [[nodiscard]] auto &assure_at_least(const Entity entt) {
-        const auto pos = entity_to_pos(entt);
-        const auto page = pos_to_page(pos);
+        const auto pos = static_cast<size_type>(traits_type::to_entity(entt));
+        const auto page = pos / traits_type::page_size;
 
         if(!(page < sparse.size())) {
             sparse.resize(page + 1u, nullptr);
         }
 
         if(!sparse[page]) {
-            constexpr entity_type init = null;
             auto page_allocator{packed.get_allocator()};
             sparse[page] = alloc_traits::allocate(page_allocator, traits_type::page_size);
-            std::uninitialized_fill(sparse[page], sparse[page] + traits_type::page_size, init);
+            std::uninitialized_fill(sparse[page], sparse[page] + traits_type::page_size, null);
         }
 
-        return sparse[page][fast_mod(pos, traits_type::page_size)];
+        auto &elem = sparse[page][fast_mod(pos, traits_type::page_size)];
+        ENTT_ASSERT(elem == null, "Slot not available");
+        return elem;
     }
 
     void release_sparse_pages() {
@@ -223,38 +216,31 @@ class basic_sparse_set {
         }
     }
 
-    void swap_at(const std::size_t lhs, const std::size_t rhs) {
-        auto &from = packed[lhs];
-        auto &to = packed[rhs];
-
-        sparse_ref(from) = traits_type::combine(static_cast<typename traits_type::entity_type>(rhs), traits_type::to_integral(from));
-        sparse_ref(to) = traits_type::combine(static_cast<typename traits_type::entity_type>(lhs), traits_type::to_integral(to));
-
-        std::swap(from, to);
-    }
-
 private:
-    [[nodiscard]] virtual const void *get_at(const std::size_t) const {
+    virtual const void *get_at(const std::size_t) const {
         return nullptr;
     }
 
-    virtual void swap_or_move([[maybe_unused]] const std::size_t lhs, [[maybe_unused]] const std::size_t rhs) {
-        ENTT_ASSERT((mode != deletion_policy::swap_only) || ((lhs < head) == (rhs < head)), "Cross swapping is not supported");
-    }
+    virtual void swap_or_move(const std::size_t, const std::size_t) {}
 
 protected:
     /*! @brief Random access iterator type. */
     using basic_iterator = internal::sparse_set_iterator<packed_container_type>;
 
     /**
-     * @brief Erases an entity from a sparse set.
-     * @param it An iterator to the element to pop.
+     * @brief Swaps two items at specific locations.
+     * @param lhs A position to move from.
+     * @param rhs The other position to move from.
      */
-    void swap_only(const basic_iterator it) {
-        ENTT_ASSERT(mode == deletion_policy::swap_only, "Deletion policy mismatch");
-        const auto pos = index(*it);
-        bump(traits_type::next(*it));
-        swap_at(pos, head -= (pos < head));
+    void swap_at(const std::size_t lhs, const std::size_t rhs) {
+        const auto entity = static_cast<typename traits_type::entity_type>(lhs);
+        const auto other = static_cast<typename traits_type::entity_type>(rhs);
+
+        sparse_ref(packed[lhs]) = traits_type::combine(other, traits_type::to_integral(packed[lhs]));
+        sparse_ref(packed[rhs]) = traits_type::combine(entity, traits_type::to_integral(packed[rhs]));
+
+        using std::swap;
+        swap(packed[lhs], packed[rhs]);
     }
 
     /**
@@ -262,13 +248,12 @@ protected:
      * @param it An iterator to the element to pop.
      */
     void swap_and_pop(const basic_iterator it) {
-        ENTT_ASSERT(mode == deletion_policy::swap_and_pop, "Deletion policy mismatch");
+        ENTT_ASSERT(mode == deletion_policy::swap_and_pop, "Deletion policy mismatched");
         auto &self = sparse_ref(*it);
         const auto entt = traits_type::to_entity(self);
         sparse_ref(packed.back()) = traits_type::combine(entt, traits_type::to_integral(packed.back()));
         packed[static_cast<size_type>(entt)] = packed.back();
         // unnecessary but it helps to detect nasty bugs
-        // NOLINTNEXTLINE(bugprone-assert-side-effect)
         ENTT_ASSERT((packed.back() = null, true), "");
         // lazy self-assignment guard
         self = null;
@@ -280,58 +265,43 @@ protected:
      * @param it An iterator to the element to pop.
      */
     void in_place_pop(const basic_iterator it) {
-        ENTT_ASSERT(mode == deletion_policy::in_place, "Deletion policy mismatch");
-        const auto pos = entity_to_pos(std::exchange(sparse_ref(*it), null));
-        packed[pos] = traits_type::combine(static_cast<typename traits_type::entity_type>(std::exchange(head, pos)), tombstone);
+        ENTT_ASSERT(mode == deletion_policy::in_place, "Deletion policy mismatched");
+        const auto entt = traits_type::to_entity(std::exchange(sparse_ref(*it), null));
+        packed[static_cast<size_type>(entt)] = std::exchange(free_list, traits_type::combine(entt, tombstone));
     }
 
+protected:
     /**
      * @brief Erases entities from a sparse set.
      * @param first An iterator to the first element of the range of entities.
      * @param last An iterator past the last element of the range of entities.
      */
     virtual void pop(basic_iterator first, basic_iterator last) {
-        switch(mode) {
-        case deletion_policy::swap_and_pop:
+        if(mode == deletion_policy::swap_and_pop) {
             for(; first != last; ++first) {
                 swap_and_pop(first);
             }
-            break;
-        case deletion_policy::in_place:
+        } else {
             for(; first != last; ++first) {
                 in_place_pop(first);
             }
-            break;
-        case deletion_policy::swap_only:
-            for(; first != last; ++first) {
-                swap_only(first);
-            }
-            break;
         }
     }
 
     /*! @brief Erases all entities of a sparse set. */
     virtual void pop_all() {
-        switch(mode) {
-        case deletion_policy::in_place:
-            if(head != max_size) {
-                for(auto &&elem: packed) {
-                    if(elem != tombstone) {
-                        sparse_ref(elem) = null;
-                    }
+        if(const auto prev = std::exchange(free_list, tombstone); prev == null) {
+            for(auto first = begin(); !(first.index() < 0); ++first) {
+                sparse_ref(*first) = null;
+            }
+        } else {
+            for(auto first = begin(); !(first.index() < 0); ++first) {
+                if(*first != tombstone) {
+                    sparse_ref(*first) = null;
                 }
-                break;
             }
-            [[fallthrough]];
-        case deletion_policy::swap_only:
-        case deletion_policy::swap_and_pop:
-            for(auto &&elem: packed) {
-                sparse_ref(elem) = null;
-            }
-            break;
         }
 
-        head = policy_to_head();
         packed.clear();
     }
 
@@ -342,57 +312,31 @@ protected:
      * @return Iterator pointing to the emplaced element.
      */
     virtual basic_iterator try_emplace(const Entity entt, const bool force_back, const void * = nullptr) {
-        ENTT_ASSERT(entt != null && entt != tombstone, "Invalid element");
-        auto &elem = assure_at_least(entt);
-        auto pos = size();
+        ENTT_ASSERT(!contains(entt), "Set already contains entity");
 
-        switch(mode) {
-        case deletion_policy::in_place:
-            if(head != max_size && !force_back) {
-                pos = head;
-                ENTT_ASSERT(elem == null, "Slot not available");
-                elem = traits_type::combine(static_cast<typename traits_type::entity_type>(head), traits_type::to_integral(entt));
-                head = entity_to_pos(std::exchange(packed[pos], entt));
-                break;
-            }
-            [[fallthrough]];
-        case deletion_policy::swap_and_pop:
+        if(auto &elem = assure_at_least(entt); free_list == null || force_back) {
             packed.push_back(entt);
-            ENTT_ASSERT(elem == null, "Slot not available");
             elem = traits_type::combine(static_cast<typename traits_type::entity_type>(packed.size() - 1u), traits_type::to_integral(entt));
-            break;
-        case deletion_policy::swap_only:
-            if(elem == null) {
-                packed.push_back(entt);
-                elem = traits_type::combine(static_cast<typename traits_type::entity_type>(packed.size() - 1u), traits_type::to_integral(entt));
-            } else {
-                ENTT_ASSERT(!(entity_to_pos(elem) < head), "Slot not available");
-                bump(entt);
-            }
-
-            pos = head++;
-            swap_at(entity_to_pos(elem), pos);
-            break;
+            return begin();
+        } else {
+            const auto pos = static_cast<size_type>(traits_type::to_entity(free_list));
+            elem = traits_type::combine(traits_type::to_integral(free_list), traits_type::to_integral(entt));
+            free_list = std::exchange(packed[pos], entt);
+            return --(end() - pos);
         }
-
-        return --(end() - static_cast<difference_type>(pos));
     }
 
-    /*! @brief Forwards variables to derived classes, if any. */
-    // NOLINTNEXTLINE(performance-unnecessary-value-param)
-    virtual void bind_any(any) noexcept {}
-
 public:
-    /*! @brief Allocator type. */
-    using allocator_type = Allocator;
+    /*! @brief Entity traits. */
+    using traits_type = entt_traits<Entity>;
     /*! @brief Underlying entity identifier. */
     using entity_type = typename traits_type::value_type;
     /*! @brief Underlying version type. */
     using version_type = typename traits_type::version_type;
     /*! @brief Unsigned integer type. */
     using size_type = std::size_t;
-    /*! @brief Signed integer type. */
-    using difference_type = std::ptrdiff_t;
+    /*! @brief Allocator type. */
+    using allocator_type = Allocator;
     /*! @brief Pointer type to contained entities. */
     using pointer = typename packed_container_type::const_pointer;
     /*! @brief Random access iterator type. */
@@ -413,7 +357,7 @@ public:
      * @param allocator The allocator to use.
      */
     explicit basic_sparse_set(const allocator_type &allocator)
-        : basic_sparse_set{deletion_policy::swap_and_pop, allocator} {}
+        : basic_sparse_set{type_id<void>(), deletion_policy::swap_and_pop, allocator} {}
 
     /**
      * @brief Constructs an empty container with the given policy and allocator.
@@ -434,13 +378,8 @@ public:
         : sparse{allocator},
           packed{allocator},
           info{&elem},
-          mode{pol},
-          head{policy_to_head()} {
-        ENTT_ASSERT(traits_type::version_mask || mode != deletion_policy::in_place, "Policy does not support zero-sized versions");
-    }
-
-    /*! @brief Default copy constructor, deleted on purpose. */
-    basic_sparse_set(const basic_sparse_set &) = delete;
+          free_list{tombstone},
+          mode{pol} {}
 
     /**
      * @brief Move constructor.
@@ -450,21 +389,21 @@ public:
         : sparse{std::move(other.sparse)},
           packed{std::move(other.packed)},
           info{other.info},
-          mode{other.mode},
-          head{std::exchange(other.head, policy_to_head())} {}
+          free_list{std::exchange(other.free_list, tombstone)},
+          mode{other.mode} {}
 
     /**
      * @brief Allocator-extended move constructor.
      * @param other The instance to move from.
      * @param allocator The allocator to use.
      */
-    basic_sparse_set(basic_sparse_set &&other, const allocator_type &allocator)
+    basic_sparse_set(basic_sparse_set &&other, const allocator_type &allocator) noexcept
         : sparse{std::move(other.sparse), allocator},
           packed{std::move(other.packed), allocator},
           info{other.info},
-          mode{other.mode},
-          head{std::exchange(other.head, policy_to_head())} {
-        ENTT_ASSERT(alloc_traits::is_always_equal::value || get_allocator() == other.get_allocator(), "Copying a sparse set is not allowed");
+          free_list{std::exchange(other.free_list, tombstone)},
+          mode{other.mode} {
+        ENTT_ASSERT(alloc_traits::is_always_equal::value || packed.get_allocator() == other.packed.get_allocator(), "Copying a sparse set is not allowed");
     }
 
     /*! @brief Default destructor. */
@@ -472,20 +411,20 @@ public:
         release_sparse_pages();
     }
 
-    /**
-     * @brief Default copy assignment operator, deleted on purpose.
-     * @return This sparse set.
-     */
-    basic_sparse_set &operator=(const basic_sparse_set &) = delete;
-
     /**
      * @brief Move assignment operator.
      * @param other The instance to move from.
      * @return This sparse set.
      */
     basic_sparse_set &operator=(basic_sparse_set &&other) noexcept {
-        ENTT_ASSERT(alloc_traits::is_always_equal::value || get_allocator() == other.get_allocator(), "Copying a sparse set is not allowed");
-        swap(other);
+        ENTT_ASSERT(alloc_traits::is_always_equal::value || packed.get_allocator() == other.packed.get_allocator(), "Copying a sparse set is not allowed");
+
+        release_sparse_pages();
+        sparse = std::move(other.sparse);
+        packed = std::move(other.packed);
+        info = other.info;
+        free_list = std::exchange(other.free_list, tombstone);
+        mode = other.mode;
         return *this;
     }
 
@@ -493,13 +432,13 @@ public:
      * @brief Exchanges the contents with those of a given sparse set.
      * @param other Sparse set to exchange the content with.
      */
-    void swap(basic_sparse_set &other) noexcept {
+    void swap(basic_sparse_set &other) {
         using std::swap;
         swap(sparse, other.sparse);
         swap(packed, other.packed);
         swap(info, other.info);
+        swap(free_list, other.free_list);
         swap(mode, other.mode);
-        swap(head, other.head);
     }
 
     /**
@@ -518,23 +457,6 @@ public:
         return mode;
     }
 
-    /**
-     * @brief Returns data on the free list whose meaning depends on the mode.
-     * @return Free list information that is mode dependent.
-     */
-    [[nodiscard]] size_type free_list() const noexcept {
-        return head;
-    }
-
-    /**
-     * @brief Sets data on the free list whose meaning depends on the mode.
-     * @param value Free list information that is mode dependent.
-     */
-    void free_list(const size_type value) noexcept {
-        ENTT_ASSERT((mode == deletion_policy::swap_only) && !(value > packed.size()), "Invalid value");
-        head = value;
-    }
-
     /**
      * @brief Increases the capacity of a sparse set.
      *
@@ -558,33 +480,6 @@ public:
 
     /*! @brief Requests the removal of unused capacity. */
     virtual void shrink_to_fit() {
-        sparse_container_type other{sparse.get_allocator()};
-        const auto len = sparse.size();
-        size_type cnt{};
-
-        other.reserve(len);
-
-        for(auto &&elem: std::as_const(packed)) {
-            if(elem != tombstone) {
-                if(const auto page = pos_to_page(entity_to_pos(elem)); sparse[page] != nullptr) {
-                    if(const auto sz = page + 1u; sz > other.size()) {
-                        other.resize(sz, nullptr);
-                    }
-
-                    other[page] = std::exchange(sparse[page], nullptr);
-
-                    if(++cnt == len) {
-                        // early exit due to lack of pages
-                        break;
-                    }
-                }
-            }
-        }
-
-        release_sparse_pages();
-        sparse.swap(other);
-
-        sparse.shrink_to_fit();
         packed.shrink_to_fit();
     }
 
@@ -592,8 +487,9 @@ public:
      * @brief Returns the extent of a sparse set.
      *
      * The extent of a sparse set is also the size of the internal sparse array.
-     * There is no guarantee that all pages have been allocated, nor that the
-     * internal packed array is be the same size.
+     * There is no guarantee that the internal packed array has the same size.
+     * Usually the size of the internal sparse array is equal or greater than
+     * the one of the internal packed array.
      *
      * @return Extent of the sparse set.
      */
@@ -628,7 +524,7 @@ public:
      * @return True if the sparse set is fully packed, false otherwise.
      */
     [[nodiscard]] bool contiguous() const noexcept {
-        return (mode != deletion_policy::in_place) || (head == max_size);
+        return (free_list == null);
     }
 
     /**
@@ -647,8 +543,8 @@ public:
      *
      * @return An iterator to the first entity of the sparse set.
      */
-    [[nodiscard]] iterator begin() const noexcept {
-        const auto pos = static_cast<difference_type>(packed.size());
+    [[nodiscard]] const_iterator begin() const noexcept {
+        const auto pos = static_cast<typename iterator::difference_type>(packed.size());
         return iterator{packed, pos};
     }
 
@@ -680,7 +576,7 @@ public:
      * @return An iterator to the first entity of the reversed internal packed
      * array.
      */
-    [[nodiscard]] reverse_iterator rbegin() const noexcept {
+    [[nodiscard]] const_reverse_iterator rbegin() const noexcept {
         return std::make_reverse_iterator(end());
     }
 
@@ -709,7 +605,7 @@ public:
      * @return An iterator to the given entity if it's found, past the end
      * iterator otherwise.
      */
-    [[nodiscard]] const_iterator find(const entity_type entt) const noexcept {
+    [[nodiscard]] iterator find(const entity_type entt) const noexcept {
         return contains(entt) ? to_iterator(entt) : end();
     }
 
@@ -719,11 +615,10 @@ public:
      * @return True if the sparse set contains the entity, false otherwise.
      */
     [[nodiscard]] bool contains(const entity_type entt) const noexcept {
-        const auto *elem = sparse_ptr(entt);
-        constexpr auto cap = traits_type::entity_mask;
-        constexpr auto mask = traits_type::to_integral(null) & ~cap;
+        const auto elem = sparse_ptr(entt);
+        constexpr auto cap = traits_type::to_entity(null);
         // testing versions permits to avoid accessing the packed array
-        return elem && (((mask & traits_type::to_integral(entt)) ^ traits_type::to_integral(*elem)) < cap);
+        return elem && (((~cap & traits_type::to_integral(entt)) ^ traits_type::to_integral(*elem)) < cap);
     }
 
     /**
@@ -733,7 +628,7 @@ public:
      * version otherwise.
      */
     [[nodiscard]] version_type current(const entity_type entt) const noexcept {
-        const auto *elem = sparse_ptr(entt);
+        const auto elem = sparse_ptr(entt);
         constexpr auto fallback = traits_type::to_version(tombstone);
         return elem ? traits_type::to_version(*elem) : fallback;
     }
@@ -750,16 +645,25 @@ public:
      */
     [[nodiscard]] size_type index(const entity_type entt) const noexcept {
         ENTT_ASSERT(contains(entt), "Set does not contain entity");
-        return entity_to_pos(sparse_ref(entt));
+        return static_cast<size_type>(traits_type::to_entity(sparse_ref(entt)));
     }
 
     /**
-     * @brief Returns the entity at specified location.
+     * @brief Returns the entity at specified location, with bounds checking.
+     * @param pos The position for which to return the entity.
+     * @return The entity at specified location if any, a null entity otherwise.
+     */
+    [[nodiscard]] entity_type at(const size_type pos) const noexcept {
+        return pos < packed.size() ? packed[pos] : null;
+    }
+
+    /**
+     * @brief Returns the entity at specified location, without bounds checking.
      * @param pos The position for which to return the entity.
      * @return The entity at specified location.
      */
     [[nodiscard]] entity_type operator[](const size_type pos) const noexcept {
-        ENTT_ASSERT(pos < packed.size(), "Index out of bounds");
+        ENTT_ASSERT(pos < packed.size(), "Position is out of bounds");
         return packed[pos];
     }
 
@@ -813,13 +717,11 @@ public:
      */
     template<typename It>
     iterator push(It first, It last) {
-        auto curr = end();
-
-        for(; first != last; ++first) {
-            curr = try_emplace(*first, true);
+        for(auto it = first; it != last; ++it) {
+            try_emplace(*it, true);
         }
 
-        return curr;
+        return first == last ? end() : find(*first);
     }
 
     /**
@@ -833,10 +735,10 @@ public:
      * @return The version of the given identifier.
      */
     version_type bump(const entity_type entt) {
-        auto &elem = sparse_ref(entt);
-        ENTT_ASSERT(entt != null && elem != tombstone, "Cannot set the required version");
-        elem = traits_type::combine(traits_type::to_integral(elem), traits_type::to_integral(entt));
-        packed[entity_to_pos(elem)] = entt;
+        auto &entity = sparse_ref(entt);
+        ENTT_ASSERT(entt != tombstone && entity != null, "Cannot set the required version");
+        entity = traits_type::combine(traits_type::to_integral(entity), traits_type::to_integral(entt));
+        packed[static_cast<size_type>(traits_type::to_entity(entity))] = entt;
         return traits_type::to_version(entt);
     }
 
@@ -906,7 +808,7 @@ public:
                     ++first;
                 }
 
-                count += static_cast<size_type>(std::distance(it, first));
+                count += std::distance(it, first);
                 erase(it, first);
             }
         } else {
@@ -920,27 +822,25 @@ public:
 
     /*! @brief Removes all tombstones from a sparse set. */
     void compact() {
-        if(mode == deletion_policy::in_place) {
-            size_type from = packed.size();
-            size_type pos = std::exchange(head, max_size);
+        size_type from = packed.size();
+        for(; from && packed[from - 1u] == tombstone; --from) {}
 
-            for(; from && packed[from - 1u] == tombstone; --from) {}
+        for(auto *it = &free_list; *it != null && from; it = std::addressof(packed[traits_type::to_entity(*it)])) {
+            if(const size_type to = traits_type::to_entity(*it); to < from) {
+                --from;
+                swap_or_move(from, to);
 
-            while(pos != max_size) {
-                if(const auto to = std::exchange(pos, entity_to_pos(packed[pos])); to < from) {
-                    --from;
-                    swap_or_move(from, to);
+                packed[to] = std::exchange(packed[from], tombstone);
+                const auto entity = static_cast<typename traits_type::entity_type>(to);
+                sparse_ref(packed[to]) = traits_type::combine(entity, traits_type::to_integral(packed[to]));
 
-                    packed[to] = packed[from];
-                    const auto elem = static_cast<typename traits_type::entity_type>(to);
-                    sparse_ref(packed[to]) = traits_type::combine(elem, traits_type::to_integral(packed[to]));
-
-                    for(; from && packed[from - 1u] == tombstone; --from) {}
-                }
+                *it = traits_type::combine(static_cast<typename traits_type::entity_type>(from), tombstone);
+                for(; from && packed[from - 1u] == tombstone; --from) {}
             }
-
-            packed.erase(packed.begin() + static_cast<difference_type>(from), packed.end());
         }
+
+        free_list = tombstone;
+        packed.resize(from);
     }
 
     /**
@@ -997,10 +897,10 @@ public:
      */
     template<typename Compare, typename Sort = std_sort, typename... Args>
     void sort_n(const size_type length, Compare compare, Sort algo = Sort{}, Args &&...args) {
-        ENTT_ASSERT((mode != deletion_policy::in_place) || (head == max_size), "Sorting with tombstones not allowed");
         ENTT_ASSERT(!(length > packed.size()), "Length exceeds the number of elements");
+        ENTT_ASSERT(free_list == null, "Partial sorting with tombstones is not supported");
 
-        algo(packed.rend() - static_cast<difference_type>(length), packed.rend(), std::move(compare), std::forward<Args>(args)...);
+        algo(packed.rend() - length, packed.rend(), std::move(compare), std::forward<Args>(args)...);
 
         for(size_type pos{}; pos < length; ++pos) {
             auto curr = pos;
@@ -1011,8 +911,8 @@ public:
                 const auto entt = packed[curr];
 
                 swap_or_move(next, idx);
-                const auto elem = static_cast<typename traits_type::entity_type>(curr);
-                sparse_ref(entt) = traits_type::combine(elem, traits_type::to_integral(packed[curr]));
+                const auto entity = static_cast<typename traits_type::entity_type>(curr);
+                sparse_ref(entt) = traits_type::combine(entity, traits_type::to_integral(packed[curr]));
                 curr = std::exchange(next, idx);
             }
         }
@@ -1032,31 +932,28 @@ public:
      */
     template<typename Compare, typename Sort = std_sort, typename... Args>
     void sort(Compare compare, Sort algo = Sort{}, Args &&...args) {
-        const size_type len = (mode == deletion_policy::swap_only) ? head : packed.size();
-        sort_n(len, std::move(compare), std::move(algo), std::forward<Args>(args)...);
+        compact();
+        sort_n(packed.size(), std::move(compare), std::move(algo), std::forward<Args>(args)...);
     }
 
     /**
-     * @brief Sort entities according to their order in a range.
+     * @brief Sort entities according to their order in another sparse set.
      *
-     * Entities that are part of both the sparse set and the range are ordered
-     * internally according to the order they have in the range.<br/>
-     * All other entities goes to the end of the sparse set and there are no
+     * Entities that are part of both the sparse sets are ordered internally
+     * according to the order they have in `other`.<br/>
+     * All the other entities goes to the end of the list and there are no
      * guarantees on their order.
      *
-     * @tparam It Type of input iterator.
-     * @param first An iterator to the first element of the range of entities.
-     * @param last An iterator past the last element of the range of entities.
-     * @return An iterator past the last of the elements actually shared.
+     * @param other The sparse sets that imposes the order of the entities.
      */
-    template<typename It>
-    iterator sort_as(It first, It last) {
-        ENTT_ASSERT((mode != deletion_policy::in_place) || (head == max_size), "Sorting with tombstones not allowed");
-        const size_type len = (mode == deletion_policy::swap_only) ? head : packed.size();
-        auto it = end() - static_cast<difference_type>(len);
+    void sort_as(const basic_sparse_set &other) {
+        compact();
 
-        for(const auto other = end(); (it != other) && (first != last); ++first) {
-            if(const auto curr = *first; contains(curr)) {
+        const auto to = other.end();
+        auto from = other.begin();
+
+        for(auto it = begin(); it.index() && from != to; ++from) {
+            if(const auto curr = *from; contains(curr)) {
                 if(const auto entt = *it; entt != curr) {
                     // basic no-leak guarantee (with invalid state) if swapping throws
                     swap_elements(entt, curr);
@@ -1065,8 +962,6 @@ public:
                 ++it;
             }
         }
-
-        return it;
     }
 
     /*! @brief Clears a sparse set. */
@@ -1074,7 +969,7 @@ public:
         pop_all();
         // sanity check to avoid subtle issues due to storage classes
         ENTT_ASSERT((compact(), size()) == 0u, "Non-empty set");
-        head = policy_to_head();
+        free_list = tombstone;
         packed.clear();
     }
 
@@ -1082,26 +977,19 @@ public:
      * @brief Returned value type, if any.
      * @return Returned value type, if any.
      */
-    [[nodiscard]] const type_info &type() const noexcept {
+    const type_info &type() const noexcept {
         return *info;
     }
 
-    /**
-     * @brief Forwards variables to derived classes, if any.
-     * @tparam Type Type of the element to forward.
-     * @param value The element to forward.
-     */
-    template<typename Type>
-    void bind(Type &&value) noexcept {
-        bind_any(forward_as_any(std::forward<Type>(value)));
-    }
+    /*! @brief Forwards variables to derived classes, if any. */
+    virtual void bind(any) noexcept {}
 
 private:
     sparse_container_type sparse;
     packed_container_type packed;
     const type_info *info;
+    entity_type free_list;
     deletion_policy mode;
-    size_type head;
 };
 
 } // namespace entt

src/entt/entity/storage.hpp

@@ -9,7 +9,6 @@
 #include <utility>
 #include <vector>
 #include "../config/config.h"
-#include "../core/bit.hpp"
 #include "../core/iterator.hpp"
 #include "../core/memory.hpp"
 #include "../core/type_info.hpp"
@@ -20,12 +19,16 @@
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
-template<typename Container, auto Page>
+template<typename Container, std::size_t Size>
 class storage_iterator final {
-    friend storage_iterator<const Container, Page>;
+    friend storage_iterator<const Container, Size>;
 
     using container_type = std::remove_const_t<Container>;
     using alloc_traits = std::allocator_traits<typename container_type::allocator_type>;
@@ -49,7 +52,7 @@ public:
           offset{idx} {}
 
     template<bool Const = std::is_const_v<Container>, typename = std::enable_if_t<Const>>
-    constexpr storage_iterator(const storage_iterator<std::remove_const_t<Container>, Page> &other) noexcept
+    constexpr storage_iterator(const storage_iterator<std::remove_const_t<Container>, Size> &other) noexcept
         : storage_iterator{other.payload, other.offset} {}
 
     constexpr storage_iterator &operator++() noexcept {
@@ -57,7 +60,7 @@ public:
     }
 
     constexpr storage_iterator operator++(int) noexcept {
-        const storage_iterator orig = *this;
+        storage_iterator orig = *this;
         return ++(*this), orig;
     }
 
@@ -66,7 +69,7 @@ public:
     }
 
     constexpr storage_iterator operator--(int) noexcept {
-        const storage_iterator orig = *this;
+        storage_iterator orig = *this;
         return operator--(), orig;
     }
 
@@ -89,16 +92,17 @@ public:
     }
 
     [[nodiscard]] constexpr reference operator[](const difference_type value) const noexcept {
-        const auto pos = static_cast<typename Container::size_type>(index() - value);
-        return (*payload)[pos / Page][fast_mod(static_cast<std::size_t>(pos), Page)];
+        const auto pos = index() - value;
+        return (*payload)[pos / Size][fast_mod(pos, Size)];
     }
 
     [[nodiscard]] constexpr pointer operator->() const noexcept {
-        return std::addressof(operator[](0));
+        const auto pos = index();
+        return (*payload)[pos / Size] + fast_mod(pos, Size);
     }
 
     [[nodiscard]] constexpr reference operator*() const noexcept {
-        return operator[](0);
+        return *operator->();
     }
 
     [[nodiscard]] constexpr difference_type index() const noexcept {
@@ -110,38 +114,38 @@ private:
     difference_type offset;
 };
 
-template<typename Lhs, typename Rhs, auto Page>
-[[nodiscard]] constexpr std::ptrdiff_t operator-(const storage_iterator<Lhs, Page> &lhs, const storage_iterator<Rhs, Page> &rhs) noexcept {
+template<typename Lhs, typename Rhs, std::size_t Size>
+[[nodiscard]] constexpr std::ptrdiff_t operator-(const storage_iterator<Lhs, Size> &lhs, const storage_iterator<Rhs, Size> &rhs) noexcept {
     return rhs.index() - lhs.index();
 }
 
-template<typename Lhs, typename Rhs, auto Page>
-[[nodiscard]] constexpr bool operator==(const storage_iterator<Lhs, Page> &lhs, const storage_iterator<Rhs, Page> &rhs) noexcept {
+template<typename Lhs, typename Rhs, std::size_t Size>
+[[nodiscard]] constexpr bool operator==(const storage_iterator<Lhs, Size> &lhs, const storage_iterator<Rhs, Size> &rhs) noexcept {
     return lhs.index() == rhs.index();
 }
 
-template<typename Lhs, typename Rhs, auto Page>
-[[nodiscard]] constexpr bool operator!=(const storage_iterator<Lhs, Page> &lhs, const storage_iterator<Rhs, Page> &rhs) noexcept {
+template<typename Lhs, typename Rhs, std::size_t Size>
+[[nodiscard]] constexpr bool operator!=(const storage_iterator<Lhs, Size> &lhs, const storage_iterator<Rhs, Size> &rhs) noexcept {
     return !(lhs == rhs);
 }
 
-template<typename Lhs, typename Rhs, auto Page>
-[[nodiscard]] constexpr bool operator<(const storage_iterator<Lhs, Page> &lhs, const storage_iterator<Rhs, Page> &rhs) noexcept {
+template<typename Lhs, typename Rhs, std::size_t Size>
+[[nodiscard]] constexpr bool operator<(const storage_iterator<Lhs, Size> &lhs, const storage_iterator<Rhs, Size> &rhs) noexcept {
     return lhs.index() > rhs.index();
 }
 
-template<typename Lhs, typename Rhs, auto Page>
-[[nodiscard]] constexpr bool operator>(const storage_iterator<Lhs, Page> &lhs, const storage_iterator<Rhs, Page> &rhs) noexcept {
+template<typename Lhs, typename Rhs, std::size_t Size>
+[[nodiscard]] constexpr bool operator>(const storage_iterator<Lhs, Size> &lhs, const storage_iterator<Rhs, Size> &rhs) noexcept {
     return rhs < lhs;
 }
 
-template<typename Lhs, typename Rhs, auto Page>
-[[nodiscard]] constexpr bool operator<=(const storage_iterator<Lhs, Page> &lhs, const storage_iterator<Rhs, Page> &rhs) noexcept {
+template<typename Lhs, typename Rhs, std::size_t Size>
+[[nodiscard]] constexpr bool operator<=(const storage_iterator<Lhs, Size> &lhs, const storage_iterator<Rhs, Size> &rhs) noexcept {
     return !(lhs > rhs);
 }
 
-template<typename Lhs, typename Rhs, auto Page>
-[[nodiscard]] constexpr bool operator>=(const storage_iterator<Lhs, Page> &lhs, const storage_iterator<Rhs, Page> &rhs) noexcept {
+template<typename Lhs, typename Rhs, std::size_t Size>
+[[nodiscard]] constexpr bool operator>=(const storage_iterator<Lhs, Size> &lhs, const storage_iterator<Rhs, Size> &rhs) noexcept {
     return !(lhs < rhs);
 }
 
@@ -152,17 +156,16 @@ class extended_storage_iterator final {
 
 public:
     using iterator_type = It;
+    using difference_type = std::ptrdiff_t;
     using value_type = decltype(std::tuple_cat(std::make_tuple(*std::declval<It>()), std::forward_as_tuple(*std::declval<Other>()...)));
     using pointer = input_iterator_pointer<value_type>;
     using reference = value_type;
-    using difference_type = std::ptrdiff_t;
     using iterator_category = std::input_iterator_tag;
-    using iterator_concept = std::forward_iterator_tag;
 
     constexpr extended_storage_iterator()
         : it{} {}
 
-    constexpr extended_storage_iterator(iterator_type base, Other... other)
+    constexpr extended_storage_iterator(It base, Other... other)
         : it{base, other...} {}
 
     template<typename... Args, typename = std::enable_if_t<(!std::is_same_v<Other, Args> && ...) && (std::is_constructible_v<Other, Args> && ...)>>
@@ -174,7 +177,7 @@ public:
     }
 
     constexpr extended_storage_iterator operator++(int) noexcept {
-        const extended_storage_iterator orig = *this;
+        extended_storage_iterator orig = *this;
         return ++(*this), orig;
     }
 
@@ -208,10 +211,14 @@ template<typename... Lhs, typename... Rhs>
 }
 
 } // namespace internal
-/*! @endcond */
 
 /**
- * @brief Storage implementation.
+ * Internal details not to be documented.
+ * @endcond
+ */
+
+/**
+ * @brief Basic storage implementation.
  *
  * Internal data structures arrange elements to maximize performance. There are
  * no guarantees that objects are returned in the insertion order when iterate
@@ -221,7 +228,7 @@ template<typename... Lhs, typename... Rhs>
  * Empty types aren't explicitly instantiated. Therefore, many of the functions
  * normally available for non-empty types will not be available for empty ones.
  *
- * @tparam Type Element type.
+ * @tparam Type Type of objects assigned to the entities.
  * @tparam Entity A valid entity type.
  * @tparam Allocator Type of allocator used to manage memory and elements.
  */
@@ -232,7 +239,8 @@ class basic_storage: public basic_sparse_set<Entity, typename std::allocator_tra
     using container_type = std::vector<typename alloc_traits::pointer, typename alloc_traits::template rebind_alloc<typename alloc_traits::pointer>>;
     using underlying_type = basic_sparse_set<Entity, typename alloc_traits::template rebind_alloc<Entity>>;
     using underlying_iterator = typename underlying_type::basic_iterator;
-    using traits_type = component_traits<Type, Entity>;
+
+    static constexpr bool is_pinned_type_v = !(std::is_move_constructible_v<Type> && std::is_move_assignable_v<Type>);
 
     [[nodiscard]] auto &element_at(const std::size_t pos) const {
         return payload[pos / traits_type::page_size][fast_mod(pos, traits_type::page_size)];
@@ -265,8 +273,8 @@ class basic_storage: public basic_sparse_set<Entity, typename std::allocator_tra
         const auto it = base_type::try_emplace(entt, force_back);
 
         ENTT_TRY {
-            auto *elem = to_address(assure_at_least(static_cast<size_type>(it.index())));
-            entt::uninitialized_construct_using_allocator(elem, get_allocator(), std::forward<Args>(args)...);
+            auto elem = assure_at_least(static_cast<size_type>(it.index()));
+            entt::uninitialized_construct_using_allocator(to_address(elem), get_allocator(), std::forward<Args>(args)...);
         }
         ENTT_CATCH {
             base_type::pop(it, it + 1u);
@@ -282,7 +290,7 @@ class basic_storage: public basic_sparse_set<Entity, typename std::allocator_tra
 
         for(auto pos = sz, length = base_type::size(); pos < length; ++pos) {
             if constexpr(traits_type::in_place_delete) {
-                if(base_type::data()[pos] != tombstone) {
+                if(base_type::at(pos) != tombstone) {
                     alloc_traits::destroy(allocator, std::addressof(element_at(pos)));
                 }
             } else {
@@ -295,37 +303,31 @@ class basic_storage: public basic_sparse_set<Entity, typename std::allocator_tra
         }
 
         payload.resize(from);
-        payload.shrink_to_fit();
-    }
-
-    void swap_at(const std::size_t lhs, const std::size_t rhs) {
-        using std::swap;
-        swap(element_at(lhs), element_at(rhs));
-    }
-
-    void move_to(const std::size_t lhs, const std::size_t rhs) {
-        auto &elem = element_at(lhs);
-        allocator_type allocator{get_allocator()};
-        entt::uninitialized_construct_using_allocator(to_address(assure_at_least(rhs)), allocator, std::move(elem));
-        alloc_traits::destroy(allocator, std::addressof(elem));
     }
 
 private:
-    [[nodiscard]] const void *get_at(const std::size_t pos) const final {
+    const void *get_at(const std::size_t pos) const final {
         return std::addressof(element_at(pos));
     }
 
     void swap_or_move([[maybe_unused]] const std::size_t from, [[maybe_unused]] const std::size_t to) override {
-        static constexpr bool is_pinned_type = !(std::is_move_constructible_v<Type> && std::is_move_assignable_v<Type>);
         // use a runtime value to avoid compile-time suppression that drives the code coverage tool crazy
-        ENTT_ASSERT((from + 1u) && !is_pinned_type, "Pinned type");
+        ENTT_ASSERT((from + 1u) && !is_pinned_type_v, "Pinned type");
+
+        if constexpr(!is_pinned_type_v) {
+            auto &elem = element_at(from);
 
-        if constexpr(!is_pinned_type) {
             if constexpr(traits_type::in_place_delete) {
-                (base_type::operator[](to) == tombstone) ? move_to(from, to) : swap_at(from, to);
-            } else {
-                swap_at(from, to);
+                if(base_type::operator[](to) == tombstone) {
+                    allocator_type allocator{get_allocator()};
+                    entt::uninitialized_construct_using_allocator(to_address(assure_at_least(to)), allocator, std::move(elem));
+                    alloc_traits::destroy(allocator, std::addressof(elem));
+                    return;
+                }
             }
+
+            using std::swap;
+            swap(elem, element_at(to));
         }
     }
 
@@ -378,14 +380,14 @@ protected:
      * @return Iterator pointing to the emplaced element.
      */
     underlying_iterator try_emplace([[maybe_unused]] const Entity entt, [[maybe_unused]] const bool force_back, const void *value) override {
-        if(value != nullptr) {
-            if constexpr(std::is_copy_constructible_v<element_type>) {
-                return emplace_element(entt, force_back, *static_cast<const element_type *>(value));
+        if(value) {
+            if constexpr(std::is_copy_constructible_v<value_type>) {
+                return emplace_element(entt, force_back, *static_cast<const value_type *>(value));
             } else {
                 return base_type::end();
             }
         } else {
-            if constexpr(std::is_default_constructible_v<element_type>) {
+            if constexpr(std::is_default_constructible_v<value_type>) {
                 return emplace_element(entt, force_back);
             } else {
                 return base_type::end();
@@ -394,20 +396,18 @@ protected:
     }
 
 public:
-    /*! @brief Allocator type. */
-    using allocator_type = Allocator;
     /*! @brief Base type. */
     using base_type = underlying_type;
-    /*! @brief Element type. */
-    using element_type = Type;
     /*! @brief Type of the objects assigned to entities. */
-    using value_type = element_type;
+    using value_type = Type;
+    /*! @brief Component traits. */
+    using traits_type = component_traits<value_type>;
     /*! @brief Underlying entity identifier. */
     using entity_type = Entity;
     /*! @brief Unsigned integer type. */
     using size_type = std::size_t;
-    /*! @brief Signed integer type. */
-    using difference_type = std::ptrdiff_t;
+    /*! @brief Allocator type. */
+    using allocator_type = Allocator;
     /*! @brief Pointer type to contained elements. */
     using pointer = typename container_type::pointer;
     /*! @brief Constant pointer type to contained elements. */
@@ -428,8 +428,6 @@ public:
     using reverse_iterable = iterable_adaptor<internal::extended_storage_iterator<typename base_type::reverse_iterator, reverse_iterator>>;
     /*! @brief Constant extended reverse iterable storage proxy. */
     using const_reverse_iterable = iterable_adaptor<internal::extended_storage_iterator<typename base_type::const_reverse_iterator, const_reverse_iterator>>;
-    /*! @brief Storage deletion policy. */
-    static constexpr deletion_policy storage_policy{traits_type::in_place_delete};
 
     /*! @brief Default constructor. */
     basic_storage()
@@ -440,55 +438,44 @@ public:
      * @param allocator The allocator to use.
      */
     explicit basic_storage(const allocator_type &allocator)
-        : base_type{type_id<element_type>(), storage_policy, allocator},
+        : base_type{type_id<value_type>(), deletion_policy{traits_type::in_place_delete}, allocator},
           payload{allocator} {}
 
-    /*! @brief Default copy constructor, deleted on purpose. */
-    basic_storage(const basic_storage &) = delete;
-
     /**
      * @brief Move constructor.
      * @param other The instance to move from.
      */
-    // NOLINTBEGIN(bugprone-use-after-move)
     basic_storage(basic_storage &&other) noexcept
         : base_type{std::move(other)},
           payload{std::move(other.payload)} {}
-    // NOLINTEND(bugprone-use-after-move)
 
     /**
      * @brief Allocator-extended move constructor.
      * @param other The instance to move from.
      * @param allocator The allocator to use.
      */
-    // NOLINTBEGIN(bugprone-use-after-move)
-    basic_storage(basic_storage &&other, const allocator_type &allocator)
+    basic_storage(basic_storage &&other, const allocator_type &allocator) noexcept
         : base_type{std::move(other), allocator},
           payload{std::move(other.payload), allocator} {
-        ENTT_ASSERT(alloc_traits::is_always_equal::value || get_allocator() == other.get_allocator(), "Copying a storage is not allowed");
+        ENTT_ASSERT(alloc_traits::is_always_equal::value || payload.get_allocator() == other.payload.get_allocator(), "Copying a storage is not allowed");
     }
-    // NOLINTEND(bugprone-use-after-move)
 
     /*! @brief Default destructor. */
-    // NOLINTNEXTLINE(bugprone-exception-escape)
     ~basic_storage() override {
         shrink_to_size(0u);
     }
 
-    /**
-     * @brief Default copy assignment operator, deleted on purpose.
-     * @return This storage.
-     */
-    basic_storage &operator=(const basic_storage &) = delete;
-
     /**
      * @brief Move assignment operator.
      * @param other The instance to move from.
      * @return This storage.
      */
     basic_storage &operator=(basic_storage &&other) noexcept {
-        ENTT_ASSERT(alloc_traits::is_always_equal::value || get_allocator() == other.get_allocator(), "Copying a storage is not allowed");
-        swap(other);
+        ENTT_ASSERT(alloc_traits::is_always_equal::value || payload.get_allocator() == other.payload.get_allocator(), "Copying a storage is not allowed");
+
+        shrink_to_size(0u);
+        base_type::operator=(std::move(other));
+        payload = std::move(other.payload);
         return *this;
     }
 
@@ -496,10 +483,10 @@ public:
      * @brief Exchanges the contents with those of a given storage.
      * @param other Storage to exchange the content with.
      */
-    void swap(basic_storage &other) noexcept {
+    void swap(basic_storage &other) {
         using std::swap;
-        swap(payload, other.payload);
         base_type::swap(other);
+        swap(payload, other.payload);
     }
 
     /**
@@ -561,7 +548,7 @@ public:
      * @return An iterator to the first instance of the internal array.
      */
     [[nodiscard]] const_iterator cbegin() const noexcept {
-        const auto pos = static_cast<difference_type>(base_type::size());
+        const auto pos = static_cast<typename iterator::difference_type>(base_type::size());
         return const_iterator{&payload, pos};
     }
 
@@ -572,7 +559,7 @@ public:
 
     /*! @copydoc begin */
     [[nodiscard]] iterator begin() noexcept {
-        const auto pos = static_cast<difference_type>(base_type::size());
+        const auto pos = static_cast<typename iterator::difference_type>(base_type::size());
         return iterator{&payload, pos};
     }
 
@@ -718,7 +705,7 @@ public:
      * @param first An iterator to the first element of the range of entities.
      * @param last An iterator past the last element of the range of entities.
      * @param value An instance of the object to construct.
-     * @return Iterator pointing to the first element inserted, if any.
+     * @return Iterator pointing to the last element inserted, if any.
      */
     template<typename It>
     iterator insert(It first, It last, const value_type &value = {}) {
@@ -755,17 +742,17 @@ public:
      * @brief Returns an iterable object to use to _visit_ a storage.
      *
      * The iterable object returns a tuple that contains the current entity and
-     * a reference to its element.
+     * a reference to its component.
      *
      * @return An iterable object to use to _visit_ the storage.
      */
     [[nodiscard]] iterable each() noexcept {
-        return iterable{{base_type::begin(), begin()}, {base_type::end(), end()}};
+        return {internal::extended_storage_iterator{base_type::begin(), begin()}, internal::extended_storage_iterator{base_type::end(), end()}};
     }
 
     /*! @copydoc each */
     [[nodiscard]] const_iterable each() const noexcept {
-        return const_iterable{{base_type::cbegin(), cbegin()}, {base_type::cend(), cend()}};
+        return {internal::extended_storage_iterator{base_type::cbegin(), cbegin()}, internal::extended_storage_iterator{base_type::cend(), cend()}};
     }
 
     /**
@@ -776,12 +763,12 @@ public:
      * @return A reverse iterable object to use to _visit_ the storage.
      */
     [[nodiscard]] reverse_iterable reach() noexcept {
-        return reverse_iterable{{base_type::rbegin(), rbegin()}, {base_type::rend(), rend()}};
+        return {internal::extended_storage_iterator{base_type::rbegin(), rbegin()}, internal::extended_storage_iterator{base_type::rend(), rend()}};
     }
 
     /*! @copydoc reach */
     [[nodiscard]] const_reverse_iterable reach() const noexcept {
-        return const_reverse_iterable{{base_type::crbegin(), crbegin()}, {base_type::crend(), crend()}};
+        return {internal::extended_storage_iterator{base_type::crbegin(), crbegin()}, internal::extended_storage_iterator{base_type::crend(), crend()}};
     }
 
 private:
@@ -790,27 +777,24 @@ private:
 
 /*! @copydoc basic_storage */
 template<typename Type, typename Entity, typename Allocator>
-class basic_storage<Type, Entity, Allocator, std::enable_if_t<component_traits<Type, Entity>::page_size == 0u>>
+class basic_storage<Type, Entity, Allocator, std::enable_if_t<component_traits<Type>::page_size == 0u>>
     : public basic_sparse_set<Entity, typename std::allocator_traits<Allocator>::template rebind_alloc<Entity>> {
     using alloc_traits = std::allocator_traits<Allocator>;
     static_assert(std::is_same_v<typename alloc_traits::value_type, Type>, "Invalid value type");
-    using traits_type = component_traits<Type, Entity>;
 
 public:
-    /*! @brief Allocator type. */
-    using allocator_type = Allocator;
     /*! @brief Base type. */
     using base_type = basic_sparse_set<Entity, typename alloc_traits::template rebind_alloc<Entity>>;
-    /*! @brief Element type. */
-    using element_type = Type;
     /*! @brief Type of the objects assigned to entities. */
-    using value_type = void;
+    using value_type = Type;
+    /*! @brief Component traits. */
+    using traits_type = component_traits<value_type>;
     /*! @brief Underlying entity identifier. */
     using entity_type = Entity;
     /*! @brief Unsigned integer type. */
     using size_type = std::size_t;
-    /*! @brief Signed integer type. */
-    using difference_type = std::ptrdiff_t;
+    /*! @brief Allocator type. */
+    using allocator_type = Allocator;
     /*! @brief Extended iterable storage proxy. */
     using iterable = iterable_adaptor<internal::extended_storage_iterator<typename base_type::iterator>>;
     /*! @brief Constant extended iterable storage proxy. */
@@ -819,8 +803,6 @@ public:
     using reverse_iterable = iterable_adaptor<internal::extended_storage_iterator<typename base_type::reverse_iterator>>;
     /*! @brief Constant extended reverse iterable storage proxy. */
     using const_reverse_iterable = iterable_adaptor<internal::extended_storage_iterator<typename base_type::const_reverse_iterator>>;
-    /*! @brief Storage deletion policy. */
-    static constexpr deletion_policy storage_policy{traits_type::in_place_delete};
 
     /*! @brief Default constructor. */
     basic_storage()
@@ -831,10 +813,7 @@ public:
      * @param allocator The allocator to use.
      */
     explicit basic_storage(const allocator_type &allocator)
-        : base_type{type_id<element_type>(), storage_policy, allocator} {}
-
-    /*! @brief Default copy constructor, deleted on purpose. */
-    basic_storage(const basic_storage &) = delete;
+        : base_type{type_id<value_type>(), deletion_policy{traits_type::in_place_delete}, allocator} {}
 
     /**
      * @brief Move constructor.
@@ -847,18 +826,9 @@ public:
      * @param other The instance to move from.
      * @param allocator The allocator to use.
      */
-    basic_storage(basic_storage &&other, const allocator_type &allocator)
+    basic_storage(basic_storage &&other, const allocator_type &allocator) noexcept
         : base_type{std::move(other), allocator} {}
 
-    /*! @brief Default destructor. */
-    ~basic_storage() override = default;
-
-    /**
-     * @brief Default copy assignment operator, deleted on purpose.
-     * @return This storage.
-     */
-    basic_storage &operator=(const basic_storage &) = delete;
-
     /**
      * @brief Move assignment operator.
      * @param other The instance to move from.
@@ -871,12 +841,7 @@ public:
      * @return The associated allocator.
      */
     [[nodiscard]] constexpr allocator_type get_allocator() const noexcept {
-        // std::allocator<void> has no cross constructors (waiting for C++20)
-        if constexpr(std::is_void_v<element_type> && !std::is_constructible_v<allocator_type, typename base_type::allocator_type>) {
-            return allocator_type{};
-        } else {
-            return allocator_type{base_type::get_allocator()};
-        }
+        return allocator_type{base_type::get_allocator()};
     }
 
     /**
@@ -889,16 +854,21 @@ public:
      * @param entt A valid identifier.
      */
     void get([[maybe_unused]] const entity_type entt) const noexcept {
-        ENTT_ASSERT(base_type::contains(entt), "Invalid entity");
+        ENTT_ASSERT(base_type::contains(entt), "Storage does not contain entity");
     }
 
     /**
      * @brief Returns an empty tuple.
+     *
+     * @warning
+     * Attempting to use an entity that doesn't belong to the storage results in
+     * undefined behavior.
+     *
      * @param entt A valid identifier.
      * @return Returns an empty tuple.
      */
     [[nodiscard]] std::tuple<> get_as_tuple([[maybe_unused]] const entity_type entt) const noexcept {
-        ENTT_ASSERT(base_type::contains(entt), "Invalid entity");
+        ENTT_ASSERT(base_type::contains(entt), "Storage does not contain entity");
         return std::tuple{};
     }
 
@@ -913,7 +883,6 @@ public:
      * @param entt A valid identifier.
      */
     template<typename... Args>
-    // NOLINTNEXTLINE(cppcoreguidelines-missing-std-forward)
     void emplace(const entity_type entt, Args &&...) {
         base_type::try_emplace(entt, false);
     }
@@ -926,7 +895,7 @@ public:
      */
     template<typename... Func>
     void patch([[maybe_unused]] const entity_type entt, Func &&...func) {
-        ENTT_ASSERT(base_type::contains(entt), "Invalid entity");
+        ENTT_ASSERT(base_type::contains(entt), "Storage does not contain entity");
         (std::forward<Func>(func)(), ...);
     }
 
@@ -938,7 +907,6 @@ public:
      * @param last An iterator past the last element of the range of entities.
      */
     template<typename It, typename... Args>
-    // NOLINTNEXTLINE(cppcoreguidelines-missing-std-forward)
     void insert(It first, It last, Args &&...) {
         for(; first != last; ++first) {
             base_type::try_emplace(*first, true);
@@ -953,12 +921,12 @@ public:
      * @return An iterable object to use to _visit_ the storage.
      */
     [[nodiscard]] iterable each() noexcept {
-        return iterable{base_type::begin(), base_type::end()};
+        return {internal::extended_storage_iterator{base_type::begin()}, internal::extended_storage_iterator{base_type::end()}};
     }
 
     /*! @copydoc each */
     [[nodiscard]] const_iterable each() const noexcept {
-        return const_iterable{base_type::cbegin(), base_type::cend()};
+        return {internal::extended_storage_iterator{base_type::cbegin()}, internal::extended_storage_iterator{base_type::cend()}};
     }
 
     /**
@@ -969,12 +937,12 @@ public:
      * @return A reverse iterable object to use to _visit_ the storage.
      */
     [[nodiscard]] reverse_iterable reach() noexcept {
-        return reverse_iterable{{base_type::rbegin()}, {base_type::rend()}};
+        return {internal::extended_storage_iterator{base_type::rbegin()}, internal::extended_storage_iterator{base_type::rend()}};
     }
 
     /*! @copydoc reach */
     [[nodiscard]] const_reverse_iterable reach() const noexcept {
-        return const_reverse_iterable{{base_type::crbegin()}, {base_type::crend()}};
+        return {internal::extended_storage_iterator{base_type::crbegin()}, internal::extended_storage_iterator{base_type::crend()}};
     }
 };
 
@@ -988,31 +956,42 @@ class basic_storage<Entity, Entity, Allocator>
     : public basic_sparse_set<Entity, Allocator> {
     using alloc_traits = std::allocator_traits<Allocator>;
     static_assert(std::is_same_v<typename alloc_traits::value_type, Entity>, "Invalid value type");
-    using underlying_iterator = typename basic_sparse_set<Entity, Allocator>::basic_iterator;
-    using traits_type = entt_traits<Entity>;
+    using underlying_type = basic_sparse_set<Entity, typename alloc_traits::template rebind_alloc<Entity>>;
+    using underlying_iterator = typename underlying_type::basic_iterator;
+    using local_traits_type = entt_traits<Entity>;
 
-    auto from_placeholder() noexcept {
-        const auto entt = traits_type::combine(static_cast<typename traits_type::entity_type>(placeholder), {});
-        ENTT_ASSERT(entt != null, "No more entities available");
-        placeholder += static_cast<size_type>(entt != null);
-        return entt;
+    auto entity_at(const std::size_t pos) const noexcept {
+        ENTT_ASSERT(pos < local_traits_type::to_entity(null), "Invalid element");
+        return local_traits_type::combine(static_cast<typename local_traits_type::entity_type>(pos), {});
     }
 
-    auto next() noexcept {
-        entity_type entt = from_placeholder();
-
-        while(base_type::current(entt) != traits_type::to_version(tombstone) && entt != null) {
-            entt = from_placeholder();
-        }
-
-        return entt;
+private:
+    void swap_or_move([[maybe_unused]] const std::size_t lhs, [[maybe_unused]] const std::size_t rhs) override {
+        ENTT_ASSERT(((lhs < length) + (rhs < length)) != 1u, "Cross swapping is not supported");
     }
 
 protected:
-    /*! @brief Erases all entities of a storage. */
+    /**
+     * @brief Erases entities from a storage.
+     * @param first An iterator to the first element of the range of entities.
+     * @param last An iterator past the last element of the range of entities.
+     */
+    void pop(underlying_iterator first, underlying_iterator last) override {
+        for(; first != last; ++first) {
+            if(const auto pos = base_type::index(*first); pos < length) {
+                base_type::bump(local_traits_type::next(*first));
+
+                if(pos != --length) {
+                    base_type::swap_at(pos, length);
+                }
+            }
+        }
+    }
+
+    /*! @brief Erases all entities of a sparse set. */
     void pop_all() override {
+        length = 0u;
         base_type::pop_all();
-        placeholder = {};
     }
 
     /**
@@ -1021,24 +1000,22 @@ protected:
      * @return Iterator pointing to the emplaced element.
      */
     underlying_iterator try_emplace(const Entity hint, const bool, const void *) override {
-        return base_type::find(generate(hint));
+        return base_type::find(emplace(hint));
     }
 
 public:
-    /*! @brief Allocator type. */
-    using allocator_type = Allocator;
     /*! @brief Base type. */
     using base_type = basic_sparse_set<Entity, Allocator>;
-    /*! @brief Element type. */
-    using element_type = Entity;
     /*! @brief Type of the objects assigned to entities. */
-    using value_type = void;
+    using value_type = Entity;
+    /*! @brief Component traits. */
+    using traits_type = component_traits<value_type>;
     /*! @brief Underlying entity identifier. */
     using entity_type = Entity;
     /*! @brief Unsigned integer type. */
     using size_type = std::size_t;
-    /*! @brief Signed integer type. */
-    using difference_type = std::ptrdiff_t;
+    /*! @brief Allocator type. */
+    using allocator_type = Allocator;
     /*! @brief Extended iterable storage proxy. */
     using iterable = iterable_adaptor<internal::extended_storage_iterator<typename base_type::iterator>>;
     /*! @brief Constant extended iterable storage proxy. */
@@ -1047,8 +1024,6 @@ public:
     using reverse_iterable = iterable_adaptor<internal::extended_storage_iterator<typename base_type::reverse_iterator>>;
     /*! @brief Constant extended reverse iterable storage proxy. */
     using const_reverse_iterable = iterable_adaptor<internal::extended_storage_iterator<typename base_type::const_reverse_iterator>>;
-    /*! @brief Storage deletion policy. */
-    static constexpr deletion_policy storage_policy = deletion_policy::swap_only;
 
     /*! @brief Default constructor. */
     basic_storage()
@@ -1060,40 +1035,25 @@ public:
      * @param allocator The allocator to use.
      */
     explicit basic_storage(const allocator_type &allocator)
-        : base_type{type_id<void>(), storage_policy, allocator} {}
-
-    /*! @brief Default copy constructor, deleted on purpose. */
-    basic_storage(const basic_storage &) = delete;
+        : base_type{type_id<value_type>(), deletion_policy::swap_and_pop, allocator},
+          length{} {}
 
     /**
      * @brief Move constructor.
      * @param other The instance to move from.
      */
-    // NOLINTBEGIN(bugprone-use-after-move)
     basic_storage(basic_storage &&other) noexcept
         : base_type{std::move(other)},
-          placeholder{other.placeholder} {}
-    // NOLINTEND(bugprone-use-after-move)
+          length{std::exchange(other.length, size_type{})} {}
 
     /**
      * @brief Allocator-extended move constructor.
      * @param other The instance to move from.
      * @param allocator The allocator to use.
      */
-    // NOLINTBEGIN(bugprone-use-after-move)
-    basic_storage(basic_storage &&other, const allocator_type &allocator)
+    basic_storage(basic_storage &&other, const allocator_type &allocator) noexcept
         : base_type{std::move(other), allocator},
-          placeholder{other.placeholder} {}
-    // NOLINTEND(bugprone-use-after-move)
-
-    /*! @brief Default destructor. */
-    ~basic_storage() override = default;
-
-    /**
-     * @brief Default copy assignment operator, deleted on purpose.
-     * @return This storage.
-     */
-    basic_storage &operator=(const basic_storage &) = delete;
+          length{std::exchange(other.length, size_type{})} {}
 
     /**
      * @brief Move assignment operator.
@@ -1101,8 +1061,8 @@ public:
      * @return This storage.
      */
     basic_storage &operator=(basic_storage &&other) noexcept {
-        placeholder = other.placeholder;
         base_type::operator=(std::move(other));
+        length = std::exchange(other.length, size_type{});
         return *this;
     }
 
@@ -1116,27 +1076,44 @@ public:
      * @param entt A valid identifier.
      */
     void get([[maybe_unused]] const entity_type entt) const noexcept {
-        ENTT_ASSERT(base_type::index(entt) < base_type::free_list(), "The requested entity is not a live one");
+        ENTT_ASSERT(base_type::index(entt) < length, "The requested entity is not a live one");
     }
 
     /**
      * @brief Returns an empty tuple.
+     *
+     * @warning
+     * Attempting to use an entity that doesn't belong to the storage results in
+     * undefined behavior.
+     *
      * @param entt A valid identifier.
      * @return Returns an empty tuple.
      */
     [[nodiscard]] std::tuple<> get_as_tuple([[maybe_unused]] const entity_type entt) const noexcept {
-        ENTT_ASSERT(base_type::index(entt) < base_type::free_list(), "The requested entity is not a live one");
+        ENTT_ASSERT(base_type::index(entt) < length, "The requested entity is not a live one");
         return std::tuple{};
     }
 
+    /**
+     * @brief Exchanges the contents with those of a given storage.
+     * @param other Storage to exchange the content with.
+     */
+    void swap(basic_storage &other) {
+        using std::swap;
+        base_type::swap(other);
+        swap(length, other.length);
+    }
+
     /**
      * @brief Creates a new identifier or recycles a destroyed one.
      * @return A valid identifier.
      */
-    entity_type generate() {
-        const auto len = base_type::free_list();
-        const auto entt = (len == base_type::size()) ? next() : base_type::data()[len];
-        return *base_type::try_emplace(entt, true);
+    entity_type emplace() {
+        if(length == base_type::size()) {
+            return *base_type::try_emplace(entity_at(length++), true);
+        }
+
+        return base_type::operator[](length++);
     }
 
     /**
@@ -1148,52 +1125,26 @@ public:
      * @param hint Required identifier.
      * @return A valid identifier.
      */
-    entity_type generate(const entity_type hint) {
-        if(hint != null && hint != tombstone) {
-            if(const auto curr = traits_type::construct(traits_type::to_entity(hint), base_type::current(hint)); curr == tombstone || !(base_type::index(curr) < base_type::free_list())) {
-                return *base_type::try_emplace(hint, true);
+    entity_type emplace(const entity_type hint) {
+        if(hint == null || hint == tombstone) {
+            return emplace();
+        } else if(const auto curr = local_traits_type::construct(local_traits_type::to_entity(hint), base_type::current(hint)); curr == tombstone) {
+            const auto pos = static_cast<size_type>(local_traits_type::to_entity(hint));
+
+            while(!(pos < base_type::size())) {
+                base_type::try_emplace(entity_at(base_type::size()), true);
             }
+
+            base_type::swap_at(pos, length++);
+        } else if(const auto idx = base_type::index(curr); idx < length) {
+            return emplace();
+        } else {
+            base_type::swap_at(idx, length++);
         }
 
-        return generate();
-    }
+        base_type::bump(hint);
 
-    /**
-     * @brief Assigns each element in a range an identifier.
-     * @tparam It Type of mutable forward iterator.
-     * @param first An iterator to the first element of the range to generate.
-     * @param last An iterator past the last element of the range to generate.
-     */
-    template<typename It>
-    void generate(It first, It last) {
-        for(const auto sz = base_type::size(); first != last && base_type::free_list() != sz; ++first) {
-            *first = *base_type::try_emplace(base_type::data()[base_type::free_list()], true);
-        }
-
-        for(; first != last; ++first) {
-            *first = *base_type::try_emplace(next(), true);
-        }
-    }
-
-    /**
-     * @brief Creates a new identifier or recycles a destroyed one.
-     * @return A valid identifier.
-     */
-    [[deprecated("use ::generate() instead")]] entity_type emplace() {
-        return generate();
-    }
-
-    /**
-     * @brief Creates a new identifier or recycles a destroyed one.
-     *
-     * If the requested identifier isn't in use, the suggested one is used.
-     * Otherwise, a new identifier is returned.
-     *
-     * @param hint Required identifier.
-     * @return A valid identifier.
-     */
-    [[deprecated("use ::generate(hint) instead")]] entity_type emplace(const entity_type hint) {
-        return generate(hint);
+        return hint;
     }
 
     /**
@@ -1204,7 +1155,7 @@ public:
      */
     template<typename... Func>
     void patch([[maybe_unused]] const entity_type entt, Func &&...func) {
-        ENTT_ASSERT(base_type::index(entt) < base_type::free_list(), "The requested entity is not a live one");
+        ENTT_ASSERT(base_type::contains(entt), "Storage does not contain entity");
         (std::forward<Func>(func)(), ...);
     }
 
@@ -1215,8 +1166,51 @@ public:
      * @param last An iterator past the last element of the range to generate.
      */
     template<typename It>
-    [[deprecated("use ::generate(first, last) instead")]] void insert(It first, It last) {
-        generate(std::move(first), std::move(last));
+    void insert(It first, It last) {
+        for(const auto sz = base_type::size(); first != last && length != sz; ++first, ++length) {
+            *first = base_type::operator[](length);
+        }
+
+        for(; first != last; ++first) {
+            *first = *base_type::try_emplace(entity_at(length++), true);
+        }
+    }
+
+    /**
+     * @brief Makes all elements in a range contiguous.
+     * @tparam It Type of forward iterator.
+     * @param first An iterator to the first element of the range to pack.
+     * @param last An iterator past the last element of the range to pack.
+     * @return The number of elements within the newly created range.
+     */
+    template<typename It>
+    size_type pack(It first, It last) {
+        size_type len = length;
+
+        for(; first != last; ++first, --len) {
+            const auto pos = base_type::index(*first);
+            ENTT_ASSERT(pos < length, "Invalid element");
+            base_type::swap_at(pos, static_cast<size_type>(len - 1u));
+        }
+
+        return (length - len);
+    }
+
+    /**
+     * @brief Returns the number of elements considered still in use.
+     * @return The number of elements considered still in use.
+     */
+    [[nodiscard]] size_type in_use() const noexcept {
+        return length;
+    }
+
+    /**
+     * @brief Sets the number of elements considered still in use.
+     * @param len The number of elements considered still in use.
+     */
+    void in_use(const size_type len) noexcept {
+        ENTT_ASSERT(!(len > base_type::size()), "Invalid length");
+        length = len;
     }
 
     /**
@@ -1227,14 +1221,12 @@ public:
      * @return An iterable object to use to _visit_ the storage.
      */
     [[nodiscard]] iterable each() noexcept {
-        return std::as_const(*this).each();
+        return {internal::extended_storage_iterator{base_type::end() - length}, internal::extended_storage_iterator{base_type::end()}};
     }
 
     /*! @copydoc each */
     [[nodiscard]] const_iterable each() const noexcept {
-        const auto it = base_type::cend();
-        const auto offset = static_cast<difference_type>(base_type::free_list());
-        return const_iterable{it - offset, it};
+        return {internal::extended_storage_iterator{base_type::cend() - length}, internal::extended_storage_iterator{base_type::cend()}};
     }
 
     /**
@@ -1245,29 +1237,16 @@ public:
      * @return A reverse iterable object to use to _visit_ the storage.
      */
     [[nodiscard]] reverse_iterable reach() noexcept {
-        return std::as_const(*this).reach();
+        return {internal::extended_storage_iterator{base_type::rbegin()}, internal::extended_storage_iterator{base_type::rbegin() + length}};
     }
 
     /*! @copydoc reach */
     [[nodiscard]] const_reverse_iterable reach() const noexcept {
-        const auto it = base_type::crbegin();
-        const auto offset = static_cast<difference_type>(base_type::free_list());
-        return const_reverse_iterable{it, it + offset};
-    }
-
-    /**
-     * @brief Sets the starting identifier for generation.
-     *
-     * The version is ignored, regardless of the value.
-     *
-     * @param hint A valid identifier.
-     */
-    void start_from(const entity_type hint) {
-        placeholder = static_cast<size_type>(traits_type::to_entity(hint));
+        return {internal::extended_storage_iterator{base_type::crbegin()}, internal::extended_storage_iterator{base_type::crbegin() + length}};
     }
 
 private:
-    size_type placeholder{};
+    size_type length;
 };
 
 } // namespace entt

src/entt/entt.hpp

@@ -1,17 +1,12 @@
-/*! @brief `EnTT` default namespace. */
-namespace entt {}
-
 // IWYU pragma: begin_exports
 #include "config/config.h"
 #include "config/macro.h"
 #include "config/version.h"
 #include "container/dense_map.hpp"
 #include "container/dense_set.hpp"
-#include "container/table.hpp"
 #include "core/algorithm.hpp"
 #include "core/any.hpp"
 #include "core/attribute.h"
-#include "core/bit.hpp"
 #include "core/compressed_pair.hpp"
 #include "core/enum.hpp"
 #include "core/family.hpp"
@@ -20,7 +15,6 @@ namespace entt {}
 #include "core/iterator.hpp"
 #include "core/memory.hpp"
 #include "core/monostate.hpp"
-#include "core/ranges.hpp"
 #include "core/tuple.hpp"
 #include "core/type_info.hpp"
 #include "core/type_traits.hpp"
@@ -31,8 +25,8 @@ namespace entt {}
 #include "entity/handle.hpp"
 #include "entity/helper.hpp"
 #include "entity/mixin.hpp"
+#include "entity/observer.hpp"
 #include "entity/organizer.hpp"
-#include "entity/ranges.hpp"
 #include "entity/registry.hpp"
 #include "entity/runtime_view.hpp"
 #include "entity/snapshot.hpp"
@@ -56,6 +50,7 @@ namespace entt {}
 #include "meta/template.hpp"
 #include "meta/type_traits.hpp"
 #include "meta/utility.hpp"
+#include "platform/android-ndk-r17.hpp"
 #include "poly/poly.hpp"
 #include "process/process.hpp"
 #include "process/scheduler.hpp"

src/entt/graph/adjacency_matrix.hpp

@@ -13,45 +13,47 @@
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 template<typename It>
 class edge_iterator {
     using size_type = std::size_t;
 
-    void find_next() noexcept {
-        for(; pos != last && !it[static_cast<typename It::difference_type>(pos)]; pos += offset) {}
-    }
-
 public:
     using value_type = std::pair<size_type, size_type>;
     using pointer = input_iterator_pointer<value_type>;
     using reference = value_type;
     using difference_type = std::ptrdiff_t;
     using iterator_category = std::input_iterator_tag;
-    using iterator_concept = std::forward_iterator_tag;
 
-    constexpr edge_iterator() noexcept = default;
+    constexpr edge_iterator() noexcept
+        : it{},
+          vert{},
+          pos{},
+          last{},
+          offset{} {}
 
-    // NOLINTNEXTLINE(bugprone-easily-swappable-parameters)
     constexpr edge_iterator(It base, const size_type vertices, const size_type from, const size_type to, const size_type step) noexcept
         : it{std::move(base)},
           vert{vertices},
           pos{from},
           last{to},
           offset{step} {
-        find_next();
+        for(; pos != last && !it[pos]; pos += offset) {}
     }
 
     constexpr edge_iterator &operator++() noexcept {
-        pos += offset;
-        find_next();
+        for(pos += offset; pos != last && !it[pos]; pos += offset) {}
         return *this;
     }
 
     constexpr edge_iterator operator++(int) noexcept {
-        const edge_iterator orig = *this;
+        edge_iterator orig = *this;
         return ++(*this), orig;
     }
 
@@ -67,25 +69,29 @@ public:
     friend constexpr bool operator==(const edge_iterator<Type> &, const edge_iterator<Type> &) noexcept;
 
 private:
-    It it{};
-    size_type vert{};
-    size_type pos{};
-    size_type last{};
+    It it;
+    size_type vert;
+    size_type pos;
+    size_type last;
     size_type offset{};
 };
 
 template<typename Container>
-[[nodiscard]] constexpr bool operator==(const edge_iterator<Container> &lhs, const edge_iterator<Container> &rhs) noexcept {
+[[nodiscard]] inline constexpr bool operator==(const edge_iterator<Container> &lhs, const edge_iterator<Container> &rhs) noexcept {
     return lhs.pos == rhs.pos;
 }
 
 template<typename Container>
-[[nodiscard]] constexpr bool operator!=(const edge_iterator<Container> &lhs, const edge_iterator<Container> &rhs) noexcept {
+[[nodiscard]] inline constexpr bool operator!=(const edge_iterator<Container> &lhs, const edge_iterator<Container> &rhs) noexcept {
     return !(lhs == rhs);
 }
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /**
  * @brief Basic implementation of a directed adjacency matrix.
@@ -112,17 +118,16 @@ public:
     using vertex_iterator = iota_iterator<vertex_type>;
     /*! @brief Edge iterator type. */
     using edge_iterator = internal::edge_iterator<typename container_type::const_iterator>;
-    /*! @brief Out-edge iterator type. */
+    /*! @brief Out edge iterator type. */
     using out_edge_iterator = edge_iterator;
-    /*! @brief In-edge iterator type. */
+    /*! @brief In edge iterator type. */
     using in_edge_iterator = edge_iterator;
     /*! @brief Graph category tag. */
     using graph_category = Category;
 
     /*! @brief Default constructor. */
     adjacency_matrix() noexcept(noexcept(allocator_type{}))
-        : adjacency_matrix{0u} {
-    }
+        : adjacency_matrix{0u} {}
 
     /**
      * @brief Constructs an empty container with a given allocator.
@@ -141,8 +146,12 @@ public:
         : matrix{vertices * vertices, allocator},
           vert{vertices} {}
 
-    /*! @brief Default copy constructor. */
-    adjacency_matrix(const adjacency_matrix &) = default;
+    /**
+     * @brief Copy constructor.
+     * @param other The instance to copy from.
+     */
+    adjacency_matrix(const adjacency_matrix &other)
+        : adjacency_matrix{other, other.get_allocator()} {}
 
     /**
      * @brief Allocator-extended copy constructor.
@@ -153,8 +162,12 @@ public:
         : matrix{other.matrix, allocator},
           vert{other.vert} {}
 
-    /*! @brief Default move constructor. */
-    adjacency_matrix(adjacency_matrix &&) noexcept = default;
+    /**
+     * @brief Move constructor.
+     * @param other The instance to move from.
+     */
+    adjacency_matrix(adjacency_matrix &&other) noexcept
+        : adjacency_matrix{std::move(other), other.get_allocator()} {}
 
     /**
      * @brief Allocator-extended move constructor.
@@ -163,31 +176,28 @@ public:
      */
     adjacency_matrix(adjacency_matrix &&other, const allocator_type &allocator)
         : matrix{std::move(other.matrix), allocator},
-          vert{other.vert} {}
-
-    /*! @brief Default destructor. */
-    ~adjacency_matrix() = default;
+          vert{std::exchange(other.vert, 0u)} {}
 
     /**
      * @brief Default copy assignment operator.
+     * @param other The instance to copy from.
      * @return This container.
      */
-    adjacency_matrix &operator=(const adjacency_matrix &) = default;
+    adjacency_matrix &operator=(const adjacency_matrix &other) {
+        matrix = other.matrix;
+        vert = other.vert;
+        return *this;
+    }
 
     /**
      * @brief Default move assignment operator.
+     * @param other The instance to move from.
      * @return This container.
      */
-    adjacency_matrix &operator=(adjacency_matrix &&) noexcept = default;
-
-    /**
-     * @brief Exchanges the contents with those of a given adjacency matrix.
-     * @param other Adjacency matrix to exchange the content with.
-     */
-    void swap(adjacency_matrix &other) noexcept {
-        using std::swap;
-        swap(matrix, other.matrix);
-        swap(vert, other.vert);
+    adjacency_matrix &operator=(adjacency_matrix &&other) noexcept {
+        matrix = std::move(other.matrix);
+        vert = std::exchange(other.vert, 0u);
+        return *this;
     }
 
     /**
@@ -205,16 +215,13 @@ public:
     }
 
     /**
-     * @brief Returns true if an adjacency matrix is empty, false otherwise.
-     *
-     * @warning
-     * Potentially expensive, try to avoid it on hot paths.
-     *
-     * @return True if the adjacency matrix is empty, false otherwise.
+     * @brief Exchanges the contents with those of a given adjacency matrix.
+     * @param other Adjacency matrix to exchange the content with.
      */
-    [[nodiscard]] bool empty() const noexcept {
-        const auto iterable = edges();
-        return (iterable.begin() == iterable.end());
+    void swap(adjacency_matrix &other) {
+        using std::swap;
+        swap(matrix, other.matrix);
+        swap(vert, other.vert);
     }
 
     /**
@@ -244,9 +251,9 @@ public:
     }
 
     /**
-     * @brief Returns an iterable object to visit all out-edges of a vertex.
-     * @param vertex The vertex of which to return all out-edges.
-     * @return An iterable object to visit all out-edges of a vertex.
+     * @brief Returns an iterable object to visit all out edges of a vertex.
+     * @param vertex The vertex of which to return all out edges.
+     * @return An iterable object to visit all out edges of a vertex.
      */
     [[nodiscard]] iterable_adaptor<out_edge_iterator> out_edges(const vertex_type vertex) const noexcept {
         const auto it = matrix.cbegin();
@@ -256,9 +263,9 @@ public:
     }
 
     /**
-     * @brief Returns an iterable object to visit all in-edges of a vertex.
-     * @param vertex The vertex of which to return all in-edges.
-     * @return An iterable object to visit all in-edges of a vertex.
+     * @brief Returns an iterable object to visit all in edges of a vertex.
+     * @param vertex The vertex of which to return all in edges.
+     * @return An iterable object to visit all in edges of a vertex.
      */
     [[nodiscard]] iterable_adaptor<in_edge_iterator> in_edges(const vertex_type vertex) const noexcept {
         const auto it = matrix.cbegin();

src/entt/graph/flow.hpp

@@ -29,9 +29,9 @@ template<typename Allocator>
 class basic_flow {
     using alloc_traits = std::allocator_traits<Allocator>;
     static_assert(std::is_same_v<typename alloc_traits::value_type, id_type>, "Invalid value type");
-    using task_container_type = dense_set<id_type, identity, std::equal_to<>, typename alloc_traits::template rebind_alloc<id_type>>;
+    using task_container_type = dense_set<id_type, identity, std::equal_to<id_type>, typename alloc_traits::template rebind_alloc<id_type>>;
     using ro_rw_container_type = std::vector<std::pair<std::size_t, bool>, typename alloc_traits::template rebind_alloc<std::pair<std::size_t, bool>>>;
-    using deps_container_type = dense_map<id_type, ro_rw_container_type, identity, std::equal_to<>, typename alloc_traits::template rebind_alloc<std::pair<const id_type, ro_rw_container_type>>>;
+    using deps_container_type = dense_map<id_type, ro_rw_container_type, identity, std::equal_to<id_type>, typename alloc_traits::template rebind_alloc<std::pair<const id_type, ro_rw_container_type>>>;
     using adjacency_matrix_type = adjacency_matrix<directed_tag, typename alloc_traits::template rebind_alloc<std::size_t>>;
 
     void emplace(const id_type res, const bool is_rw) {
@@ -134,8 +134,9 @@ public:
      */
     explicit basic_flow(const allocator_type &allocator)
         : index{0u, allocator},
-          vertices{allocator},
-          deps{allocator} {}
+          vertices{},
+          deps{},
+          sync_on{} {}
 
     /*! @brief Default copy constructor. */
     basic_flow(const basic_flow &) = default;
@@ -165,9 +166,6 @@ public:
           deps{std::move(other.deps), allocator},
           sync_on{other.sync_on} {}
 
-    /*! @brief Default destructor. */
-    ~basic_flow() = default;
-
     /**
      * @brief Default copy assignment operator.
      * @return This flow builder.
@@ -180,18 +178,6 @@ public:
      */
     basic_flow &operator=(basic_flow &&) noexcept = default;
 
-    /**
-     * @brief Exchanges the contents with those of a given flow builder.
-     * @param other Flow builder to exchange the content with.
-     */
-    void swap(basic_flow &other) noexcept {
-        using std::swap;
-        std::swap(index, other.index);
-        std::swap(vertices, other.vertices);
-        std::swap(deps, other.deps);
-        std::swap(sync_on, other.sync_on);
-    }
-
     /**
      * @brief Returns the associated allocator.
      * @return The associated allocator.
@@ -206,7 +192,7 @@ public:
      * @return The requested identifier.
      */
     [[nodiscard]] id_type operator[](const size_type pos) const {
-        return vertices.cbegin()[static_cast<typename task_container_type::difference_type>(pos)];
+        return vertices.cbegin()[pos];
     }
 
     /*! @brief Clears the flow builder. */
@@ -218,11 +204,15 @@ public:
     }
 
     /**
-     * @brief Returns true if a flow builder contains no tasks, false otherwise.
-     * @return True if the flow builder contains no tasks, false otherwise.
+     * @brief Exchanges the contents with those of a given flow builder.
+     * @param other Flow builder to exchange the content with.
      */
-    [[nodiscard]] bool empty() const noexcept {
-        return vertices.empty();
+    void swap(basic_flow &other) {
+        using std::swap;
+        std::swap(index, other.index);
+        std::swap(vertices, other.vertices);
+        std::swap(deps, other.deps);
+        std::swap(sync_on, other.sync_on);
     }
 
     /**
@@ -343,7 +333,7 @@ private:
     compressed_pair<size_type, allocator_type> index;
     task_container_type vertices;
     deps_container_type deps;
-    size_type sync_on{};
+    size_type sync_on;
 };
 
 } // namespace entt

src/entt/locator/locator.hpp

@@ -38,19 +38,9 @@ public:
 
     /*! @brief Default constructor, deleted on purpose. */
     locator() = delete;
-
-    /*! @brief Default copy constructor, deleted on purpose. */
-    locator(const locator &) = delete;
-
     /*! @brief Default destructor, deleted on purpose. */
     ~locator() = delete;
 
-    /**
-     * @brief Default copy assignment operator, deleted on purpose.
-     * @return This locator.
-     */
-    locator &operator=(const locator &) = delete;
-
     /**
      * @brief Checks whether a service locator contains a value.
      * @return True if the service locator contains a value, false otherwise.
@@ -149,7 +139,6 @@ public:
 
 private:
     // std::shared_ptr because of its type erased allocator which is useful here
-    // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
     inline static std::shared_ptr<Service> service{};
 };
 

src/entt/meta/container.hpp

@@ -1,5 +1,3 @@
-// IWYU pragma: always_keep
-
 #ifndef ENTT_META_CONTAINER_HPP
 #define ENTT_META_CONTAINER_HPP
 
@@ -21,292 +19,153 @@
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 template<typename, typename = void>
-struct fixed_size_sequence_container: std::true_type {};
+struct is_dynamic_sequence_container: std::false_type {};
 
 template<typename Type>
-struct fixed_size_sequence_container<Type, std::void_t<decltype(&Type::clear)>>: std::false_type {};
-
-template<typename Type>
-inline constexpr bool fixed_size_sequence_container_v = fixed_size_sequence_container<Type>::value;
+struct is_dynamic_sequence_container<Type, std::void_t<decltype(&Type::clear)>>: std::true_type {};
 
 template<typename, typename = void>
-struct key_only_associative_container: std::true_type {};
+struct is_key_only_meta_associative_container: std::true_type {};
 
 template<typename Type>
-struct key_only_associative_container<Type, std::void_t<typename Type::mapped_type>>: std::false_type {};
+struct is_key_only_meta_associative_container<Type, std::void_t<typename Type::mapped_type>>: std::false_type {};
 
-template<typename Type>
-inline constexpr bool key_only_associative_container_v = key_only_associative_container<Type>::value;
-
-template<typename, typename = void>
-struct reserve_aware_container: std::false_type {};
-
-template<typename Type>
-struct reserve_aware_container<Type, std::void_t<decltype(&Type::reserve)>>: std::true_type {};
-
-template<typename Type>
-inline constexpr bool reserve_aware_container_v = reserve_aware_container<Type>::value;
-
-} // namespace internal
-/*! @endcond */
-
-/**
- * @brief General purpose implementation of meta sequence container traits.
- * @tparam Type Type of underlying sequence container.
- */
 template<typename Type>
 struct basic_meta_sequence_container_traits {
-    static_assert(std::is_same_v<Type, std::remove_cv_t<std::remove_reference_t<Type>>>, "Unexpected type");
+    using iterator = meta_sequence_container::iterator;
+    using size_type = std::size_t;
 
-    /*! @brief Unsigned integer type. */
-    using size_type = typename meta_sequence_container::size_type;
-    /*! @brief Meta iterator type. */
-    using iterator = typename meta_sequence_container::iterator;
-
-    /*! @brief True in case of key-only containers, false otherwise. */
-    static constexpr bool fixed_size = internal::fixed_size_sequence_container_v<Type>;
-
-    /**
-     * @brief Returns the number of elements in a container.
-     * @param container Opaque pointer to a container of the given type.
-     * @return Number of elements.
-     */
-    [[nodiscard]] static size_type size(const void *container) {
-        return static_cast<const Type *>(container)->size();
+    [[nodiscard]] static size_type size(const any &container) noexcept {
+        return any_cast<const Type &>(container).size();
     }
 
-    /**
-     * @brief Clears a container.
-     * @param container Opaque pointer to a container of the given type.
-     * @return True in case of success, false otherwise.
-     */
-    [[nodiscard]] static bool clear([[maybe_unused]] void *container) {
-        if constexpr(fixed_size) {
-            return false;
-        } else {
-            static_cast<Type *>(container)->clear();
-            return true;
+    [[nodiscard]] static bool resize([[maybe_unused]] any &container, [[maybe_unused]] size_type sz) {
+        if constexpr(is_dynamic_sequence_container<Type>::value) {
+            if(auto *const cont = any_cast<Type>(&container); cont) {
+                cont->resize(sz);
+                return true;
+            }
         }
+
+        return false;
     }
 
-    /**
-     * @brief Increases the capacity of a container.
-     * @param container Opaque pointer to a container of the given type.
-     * @param sz Desired capacity.
-     * @return True in case of success, false otherwise.
-     */
-    [[nodiscard]] static bool reserve([[maybe_unused]] void *container, [[maybe_unused]] const size_type sz) {
-        if constexpr(internal::reserve_aware_container_v<Type>) {
-            static_cast<Type *>(container)->reserve(sz);
-            return true;
-        } else {
-            return false;
+    [[nodiscard]] static iterator iter(const meta_ctx &ctx, any &container, const bool as_end) {
+        if(auto *const cont = any_cast<Type>(&container); cont) {
+            return iterator{ctx, as_end ? cont->end() : cont->begin()};
         }
+
+        const Type &as_const = any_cast<const Type &>(container);
+        return iterator{ctx, as_end ? as_const.end() : as_const.begin()};
     }
 
-    /**
-     * @brief Resizes a container.
-     * @param container Opaque pointer to a container of the given type.
-     * @param sz The new number of elements.
-     * @return True in case of success, false otherwise.
-     */
-    [[nodiscard]] static bool resize([[maybe_unused]] void *container, [[maybe_unused]] const size_type sz) {
-        if constexpr(fixed_size || !std::is_default_constructible_v<typename Type::value_type>) {
-            return false;
-        } else {
-            static_cast<Type *>(container)->resize(sz);
-            return true;
+    [[nodiscard]] static iterator insert_or_erase([[maybe_unused]] const meta_ctx &ctx, [[maybe_unused]] any &container, [[maybe_unused]] const any &handle, [[maybe_unused]] meta_any &value) {
+        if constexpr(is_dynamic_sequence_container<Type>::value) {
+            if(auto *const cont = any_cast<Type>(&container); cont) {
+                typename Type::const_iterator it{};
+
+                if(auto *non_const = any_cast<typename Type::iterator>(&handle); non_const) {
+                    it = *non_const;
+                } else {
+                    it = any_cast<const typename Type::const_iterator &>(handle);
+                }
+
+                if(value) {
+                    // this abomination is necessary because only on macos value_type and const_reference are different types for std::vector<bool>
+                    if(value.allow_cast<typename Type::const_reference>() || value.allow_cast<typename Type::value_type>()) {
+                        const auto *element = value.try_cast<std::remove_reference_t<typename Type::const_reference>>();
+                        return iterator{ctx, cont->insert(it, element ? *element : value.cast<typename Type::value_type>())};
+                    }
+                } else {
+                    return iterator{ctx, cont->erase(it)};
+                }
+            }
         }
-    }
 
-    /**
-     * @brief Returns a possibly const iterator to the beginning.
-     * @param area The context to pass to the newly created iterator.
-     * @param container Opaque pointer to a container of the given type.
-     * @param as_const Const opaque pointer fallback.
-     * @return An iterator to the first element of the container.
-     */
-    static iterator begin(const meta_ctx &area, void *container, const void *as_const) {
-        return (container != nullptr) ? iterator{area, static_cast<Type *>(container)->begin()}
-                                      : iterator{area, static_cast<const Type *>(as_const)->begin()};
-    }
-
-    /**
-     * @brief Returns a possibly const iterator to the end.
-     * @param area The context to pass to the newly created iterator.
-     * @param container Opaque pointer to a container of the given type.
-     * @param as_const Const opaque pointer fallback.
-     * @return An iterator that is past the last element of the container.
-     */
-    static iterator end(const meta_ctx &area, void *container, const void *as_const) {
-        return (container != nullptr) ? iterator{area, static_cast<Type *>(container)->end()}
-                                      : iterator{area, static_cast<const Type *>(as_const)->end()};
-    }
-
-    /**
-     * @brief Assigns one element to a container and constructs its object from
-     * a given opaque instance.
-     * @param area The context to pass to the newly created iterator.
-     * @param container Opaque pointer to a container of the given type.
-     * @param value Optional opaque instance of the object to construct (as
-     * value type).
-     * @param cref Optional opaque instance of the object to construct (as
-     * decayed const reference type).
-     * @param it Iterator before which the element will be inserted.
-     * @return A possibly invalid iterator to the inserted element.
-     */
-    [[nodiscard]] static iterator insert([[maybe_unused]] const meta_ctx &area, [[maybe_unused]] void *container, [[maybe_unused]] const void *value, [[maybe_unused]] const void *cref, [[maybe_unused]] const iterator &it) {
-        if constexpr(fixed_size) {
-            return iterator{};
-        } else {
-            auto *const non_const = any_cast<typename Type::iterator>(&it.base());
-            return {area, static_cast<Type *>(container)->insert(
-                              non_const ? *non_const : any_cast<const typename Type::const_iterator &>(it.base()),
-                              (value != nullptr) ? *static_cast<const typename Type::value_type *>(value) : *static_cast<const std::remove_reference_t<typename Type::const_reference> *>(cref))};
-        }
-    }
-
-    /**
-     * @brief Erases an element from a container.
-     * @param area The context to pass to the newly created iterator.
-     * @param container Opaque pointer to a container of the given type.
-     * @param it An opaque iterator to the element to erase.
-     * @return A possibly invalid iterator following the last removed element.
-     */
-    [[nodiscard]] static iterator erase([[maybe_unused]] const meta_ctx &area, [[maybe_unused]] void *container, [[maybe_unused]] const iterator &it) {
-        if constexpr(fixed_size) {
-            return iterator{};
-        } else {
-            auto *const non_const = any_cast<typename Type::iterator>(&it.base());
-            return {area, static_cast<Type *>(container)->erase(non_const ? *non_const : any_cast<const typename Type::const_iterator &>(it.base()))};
-        }
+        return iterator{};
     }
 };
 
-/**
- * @brief General purpose implementation of meta associative container traits.
- * @tparam Type Type of underlying associative container.
- */
 template<typename Type>
 struct basic_meta_associative_container_traits {
-    static_assert(std::is_same_v<Type, std::remove_cv_t<std::remove_reference_t<Type>>>, "Unexpected type");
+    using iterator = meta_associative_container::iterator;
+    using size_type = std::size_t;
 
-    /*! @brief Unsigned integer type. */
-    using size_type = typename meta_associative_container::size_type;
-    /*! @brief Meta iterator type. */
-    using iterator = typename meta_associative_container::iterator;
+    static constexpr auto key_only = is_key_only_meta_associative_container<Type>::value;
 
-    /*! @brief True in case of key-only containers, false otherwise. */
-    static constexpr bool key_only = internal::key_only_associative_container_v<Type>;
-
-    /**
-     * @brief Returns the number of elements in a container.
-     * @param container Opaque pointer to a container of the given type.
-     * @return Number of elements.
-     */
-    [[nodiscard]] static size_type size(const void *container) {
-        return static_cast<const Type *>(container)->size();
+    [[nodiscard]] static size_type size(const any &container) noexcept {
+        return any_cast<const Type &>(container).size();
     }
 
-    /**
-     * @brief Clears a container.
-     * @param container Opaque pointer to a container of the given type.
-     * @return True in case of success, false otherwise.
-     */
-    [[nodiscard]] static bool clear(void *container) {
-        static_cast<Type *>(container)->clear();
-        return true;
-    }
-
-    /**
-     * @brief Increases the capacity of a container.
-     * @param container Opaque pointer to a container of the given type.
-     * @param sz Desired capacity.
-     * @return True in case of success, false otherwise.
-     */
-    [[nodiscard]] static bool reserve([[maybe_unused]] void *container, [[maybe_unused]] const size_type sz) {
-        if constexpr(internal::reserve_aware_container_v<Type>) {
-            static_cast<Type *>(container)->reserve(sz);
+    [[nodiscard]] static bool clear(any &container) {
+        if(auto *const cont = any_cast<Type>(&container); cont) {
+            cont->clear();
             return true;
-        } else {
-            return false;
         }
+
+        return false;
     }
 
-    /**
-     * @brief Returns a possibly const iterator to the beginning.
-     * @param area The context to pass to the newly created iterator.
-     * @param container Opaque pointer to a container of the given type.
-     * @param as_const Const opaque pointer fallback.
-     * @return An iterator to the first element of the container.
-     */
-    static iterator begin(const meta_ctx &area, void *container, const void *as_const) {
-        return (container != nullptr) ? iterator{area, std::bool_constant<key_only>{}, static_cast<Type *>(container)->begin()}
-                                      : iterator{area, std::bool_constant<key_only>{}, static_cast<const Type *>(as_const)->begin()};
-    }
-
-    /**
-     * @brief Returns a possibly const iterator to the end.
-     * @param area The context to pass to the newly created iterator.
-     * @param container Opaque pointer to a container of the given type.
-     * @param as_const Const opaque pointer fallback.
-     * @return An iterator that is past the last element of the container.
-     */
-    static iterator end(const meta_ctx &area, void *container, const void *as_const) {
-        return (container != nullptr) ? iterator{area, std::bool_constant<key_only>{}, static_cast<Type *>(container)->end()}
-                                      : iterator{area, std::bool_constant<key_only>{}, static_cast<const Type *>(as_const)->end()};
-    }
-
-    /**
-     * @brief Inserts an element into a container, if the key does not exist.
-     * @param container Opaque pointer to a container of the given type.
-     * @param key An opaque key value of an element to insert.
-     * @param value Optional opaque value to insert (key-value containers).
-     * @return True if the insertion took place, false otherwise.
-     */
-    [[nodiscard]] static bool insert(void *container, const void *key, [[maybe_unused]] const void *value) {
-        if constexpr(key_only) {
-            return static_cast<Type *>(container)->insert(*static_cast<const typename Type::key_type *>(key)).second;
-        } else {
-            return static_cast<Type *>(container)->emplace(*static_cast<const typename Type::key_type *>(key), *static_cast<const typename Type::mapped_type *>(value)).second;
+    [[nodiscard]] static iterator iter(const meta_ctx &ctx, any &container, const bool as_end) {
+        if(auto *const cont = any_cast<Type>(&container); cont) {
+            return iterator{ctx, std::bool_constant<key_only>{}, as_end ? cont->end() : cont->begin()};
         }
+
+        const auto &as_const = any_cast<const Type &>(container);
+        return iterator{ctx, std::bool_constant<key_only>{}, as_end ? as_const.end() : as_const.begin()};
     }
 
-    /**
-     * @brief Removes an element from a container.
-     * @param container Opaque pointer to a container of the given type.
-     * @param key An opaque key value of an element to remove.
-     * @return Number of elements removed (either 0 or 1).
-     */
-    [[nodiscard]] static size_type erase(void *container, const void *key) {
-        return static_cast<Type *>(container)->erase(*static_cast<const typename Type::key_type *>(key));
+    [[nodiscard]] static size_type insert_or_erase(any &container, meta_any &key, meta_any &value) {
+        if(auto *const cont = any_cast<Type>(&container); cont && key.allow_cast<const typename Type::key_type &>()) {
+            if(value) {
+                if constexpr(key_only) {
+                    return cont->insert(key.cast<const typename Type::key_type &>()).second;
+                } else {
+                    return value.allow_cast<const typename Type::mapped_type &>() && cont->emplace(key.cast<const typename Type::key_type &>(), value.cast<const typename Type::mapped_type &>()).second;
+                }
+            } else {
+                return cont->erase(key.cast<const typename Type::key_type &>());
+            }
+        }
+
+        return 0u;
     }
 
-    /**
-     * @brief Finds an element with a given key.
-     * @param area The context to pass to the newly created iterator.
-     * @param container Opaque pointer to a container of the given type.
-     * @param as_const Const opaque pointer fallback.
-     * @param key Opaque key value of an element to search for.
-     * @return An iterator to the element with the given key, if any.
-     */
-    static iterator find(const meta_ctx &area, void *container, const void *as_const, const void *key) {
-        return (container != nullptr) ? iterator{area, std::bool_constant<key_only>{}, static_cast<Type *>(container)->find(*static_cast<const typename Type::key_type *>(key))}
-                                      : iterator{area, std::bool_constant<key_only>{}, static_cast<const Type *>(as_const)->find(*static_cast<const typename Type::key_type *>(key))};
+    [[nodiscard]] static iterator find(const meta_ctx &ctx, any &container, meta_any &key) {
+        if(key.allow_cast<const typename Type::key_type &>()) {
+            if(auto *const cont = any_cast<Type>(&container); cont) {
+                return iterator{ctx, std::bool_constant<key_only>{}, cont->find(key.cast<const typename Type::key_type &>())};
+            }
+
+            return iterator{ctx, std::bool_constant<key_only>{}, any_cast<const Type &>(container).find(key.cast<const typename Type::key_type &>())};
+        }
+
+        return iterator{};
     }
 };
 
+} // namespace internal
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
+
 /**
  * @brief Meta sequence container traits for `std::vector`s of any type.
  * @tparam Args Template arguments for the container.
  */
 template<typename... Args>
 struct meta_sequence_container_traits<std::vector<Args...>>
-    : basic_meta_sequence_container_traits<std::vector<Args...>> {};
+    : internal::basic_meta_sequence_container_traits<std::vector<Args...>> {};
 
 /**
  * @brief Meta sequence container traits for `std::array`s of any type.
@@ -315,7 +174,7 @@ struct meta_sequence_container_traits<std::vector<Args...>>
  */
 template<typename Type, auto N>
 struct meta_sequence_container_traits<std::array<Type, N>>
-    : basic_meta_sequence_container_traits<std::array<Type, N>> {};
+    : internal::basic_meta_sequence_container_traits<std::array<Type, N>> {};
 
 /**
  * @brief Meta sequence container traits for `std::list`s of any type.
@@ -323,7 +182,7 @@ struct meta_sequence_container_traits<std::array<Type, N>>
  */
 template<typename... Args>
 struct meta_sequence_container_traits<std::list<Args...>>
-    : basic_meta_sequence_container_traits<std::list<Args...>> {};
+    : internal::basic_meta_sequence_container_traits<std::list<Args...>> {};
 
 /**
  * @brief Meta sequence container traits for `std::deque`s of any type.
@@ -331,7 +190,7 @@ struct meta_sequence_container_traits<std::list<Args...>>
  */
 template<typename... Args>
 struct meta_sequence_container_traits<std::deque<Args...>>
-    : basic_meta_sequence_container_traits<std::deque<Args...>> {};
+    : internal::basic_meta_sequence_container_traits<std::deque<Args...>> {};
 
 /**
  * @brief Meta associative container traits for `std::map`s of any type.
@@ -339,7 +198,7 @@ struct meta_sequence_container_traits<std::deque<Args...>>
  */
 template<typename... Args>
 struct meta_associative_container_traits<std::map<Args...>>
-    : basic_meta_associative_container_traits<std::map<Args...>> {};
+    : internal::basic_meta_associative_container_traits<std::map<Args...>> {};
 
 /**
  * @brief Meta associative container traits for `std::unordered_map`s of any
@@ -348,7 +207,7 @@ struct meta_associative_container_traits<std::map<Args...>>
  */
 template<typename... Args>
 struct meta_associative_container_traits<std::unordered_map<Args...>>
-    : basic_meta_associative_container_traits<std::unordered_map<Args...>> {};
+    : internal::basic_meta_associative_container_traits<std::unordered_map<Args...>> {};
 
 /**
  * @brief Meta associative container traits for `std::set`s of any type.
@@ -356,7 +215,7 @@ struct meta_associative_container_traits<std::unordered_map<Args...>>
  */
 template<typename... Args>
 struct meta_associative_container_traits<std::set<Args...>>
-    : basic_meta_associative_container_traits<std::set<Args...>> {};
+    : internal::basic_meta_associative_container_traits<std::set<Args...>> {};
 
 /**
  * @brief Meta associative container traits for `std::unordered_set`s of any
@@ -365,7 +224,7 @@ struct meta_associative_container_traits<std::set<Args...>>
  */
 template<typename... Args>
 struct meta_associative_container_traits<std::unordered_set<Args...>>
-    : basic_meta_associative_container_traits<std::unordered_set<Args...>> {};
+    : internal::basic_meta_associative_container_traits<std::unordered_set<Args...>> {};
 
 /**
  * @brief Meta associative container traits for `dense_map`s of any type.
@@ -373,7 +232,7 @@ struct meta_associative_container_traits<std::unordered_set<Args...>>
  */
 template<typename... Args>
 struct meta_associative_container_traits<dense_map<Args...>>
-    : basic_meta_associative_container_traits<dense_map<Args...>> {};
+    : internal::basic_meta_associative_container_traits<dense_map<Args...>> {};
 
 /**
  * @brief Meta associative container traits for `dense_set`s of any type.
@@ -381,7 +240,7 @@ struct meta_associative_container_traits<dense_map<Args...>>
  */
 template<typename... Args>
 struct meta_associative_container_traits<dense_set<Args...>>
-    : basic_meta_associative_container_traits<dense_set<Args...>> {};
+    : internal::basic_meta_associative_container_traits<dense_set<Args...>> {};
 
 } // namespace entt
 

src/entt/meta/context.hpp

@@ -9,20 +9,28 @@ namespace entt {
 
 class meta_ctx;
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 struct meta_type_node;
 
 struct meta_context {
-    dense_map<id_type, meta_type_node, identity> value;
+    dense_map<id_type, meta_type_node, identity> value{};
 
-    [[nodiscard]] inline static meta_context &from(meta_ctx &ctx);
-    [[nodiscard]] inline static const meta_context &from(const meta_ctx &ctx);
+    [[nodiscard]] static inline meta_context &from(meta_ctx &ctx);
+    [[nodiscard]] static inline const meta_context &from(const meta_ctx &ctx);
 };
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 /*! @brief Disambiguation tag for constructors and the like. */
 class meta_ctx_arg_t final {};
@@ -32,11 +40,15 @@ inline constexpr meta_ctx_arg_t meta_ctx_arg{};
 
 /*! @brief Opaque meta context type. */
 class meta_ctx: private internal::meta_context {
-    // attorney idiom like model to access the base class
+    /*! @brief Attorney idiom like model to access the base class. */
     friend struct internal::meta_context;
 };
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 [[nodiscard]] inline internal::meta_context &internal::meta_context::from(meta_ctx &ctx) {
     return ctx;
 }
@@ -44,7 +56,11 @@ class meta_ctx: private internal::meta_context {
 [[nodiscard]] inline const internal::meta_context &internal::meta_context::from(const meta_ctx &ctx) {
     return ctx;
 }
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 } // namespace entt
 

src/entt/meta/factory.hpp

@@ -2,14 +2,12 @@
 #define ENTT_META_FACTORY_HPP
 
 #include <cstddef>
-#include <cstdint>
 #include <functional>
 #include <memory>
 #include <tuple>
 #include <type_traits>
 #include <utility>
 #include "../config/config.h"
-#include "../core/bit.hpp"
 #include "../core/fwd.hpp"
 #include "../core/type_info.hpp"
 #include "../core/type_traits.hpp"
@@ -24,149 +22,72 @@
 
 namespace entt {
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
-class basic_meta_factory {
-    using invoke_type = std::remove_pointer_t<decltype(meta_func_node::invoke)>;
+[[nodiscard]] inline decltype(auto) owner(meta_ctx &ctx, const type_info &info) {
+    auto &&context = internal::meta_context::from(ctx);
+    ENTT_ASSERT(context.value.contains(info.hash()), "Type not available");
+    return context.value[info.hash()];
+}
 
-    auto *find_member_or_assert() {
-        auto *member = find_member<&meta_data_node::id>(details->data, bucket);
-        ENTT_ASSERT(member != nullptr, "Cannot find member");
-        return member;
-    }
+inline meta_data_node &meta_extend(internal::meta_type_node &parent, const id_type id, meta_data_node node) {
+    return parent.details->data.insert_or_assign(id, std::move(node)).first->second;
+}
 
-    auto *find_overload_or_assert() {
-        auto *overload = find_overload(find_member<&meta_func_node::id>(details->func, bucket), invoke);
-        ENTT_ASSERT(overload != nullptr, "Cannot find overload");
-        return overload;
-    }
-
-    void reset_bucket(const id_type id, invoke_type *const ref = nullptr) {
-        invoke = ref;
-        bucket = id;
-    }
-
-protected:
-    void type(const id_type id) noexcept {
-        reset_bucket(parent);
-        auto &&elem = meta_context::from(*ctx).value[parent];
-        ENTT_ASSERT(elem.id == id || !resolve(*ctx, id), "Duplicate identifier");
-        elem.id = id;
-    }
-
-    template<typename Type>
-    void insert_or_assign(Type node) {
-        reset_bucket(parent);
-
-        if constexpr(std::is_same_v<Type, meta_base_node>) {
-            auto *member = find_member<&meta_base_node::type>(details->base, node.type);
-            member ? (*member = node) : details->base.emplace_back(node);
-        } else if constexpr(std::is_same_v<Type, meta_conv_node>) {
-            auto *member = find_member<&meta_conv_node::type>(details->conv, node.type);
-            member ? (*member = node) : details->conv.emplace_back(node);
-        } else {
-            static_assert(std::is_same_v<Type, meta_ctor_node>, "Unexpected type");
-            auto *member = find_member<&meta_ctor_node::id>(details->ctor, node.id);
-            member ? (*member = node) : details->ctor.emplace_back(node);
+inline meta_func_node &meta_extend(internal::meta_type_node &parent, const id_type id, meta_func_node node) {
+    if(auto it = parent.details->func.find(id); it != parent.details->func.end()) {
+        for(auto *curr = &it->second; curr; curr = curr->next.get()) {
+            if(curr->invoke == node.invoke) {
+                node.next = std::move(curr->next);
+                *curr = std::move(node);
+                return *curr;
+            }
         }
+
+        // locally overloaded function
+        node.next = std::make_shared<meta_func_node>(std::move(parent.details->func[id]));
     }
 
-    void dtor(meta_dtor_node node) {
-        reset_bucket(parent);
-        meta_context::from(*ctx).value[parent].dtor = node;
-    }
-
-    void data(meta_data_node node) {
-        reset_bucket(node.id);
-
-        if(auto *member = find_member<&meta_data_node::id>(details->data, node.id); member == nullptr) {
-            details->data.emplace_back(std::move(node));
-        } else if(member->set != node.set || member->get != node.get) {
-            *member = std::move(node);
-        }
-    }
-
-    void func(meta_func_node node) {
-        reset_bucket(node.id, node.invoke);
-
-        if(auto *member = find_member<&meta_func_node::id>(details->func, node.id); member == nullptr) {
-            details->func.emplace_back(std::move(node));
-        } else if(auto *overload = find_overload(member, node.invoke); overload == nullptr) {
-            while(member->next != nullptr) { member = member->next.get(); }
-            member->next = std::make_shared<meta_func_node>(std::move(node));
-        }
-    }
-
-    void traits(const meta_traits value) {
-        if(bucket == parent) {
-            meta_context::from(*ctx).value[bucket].traits |= value;
-        } else if(invoke == nullptr) {
-            find_member_or_assert()->traits |= value;
-        } else {
-            find_overload_or_assert()->traits |= value;
-        }
-    }
-
-    void custom(meta_custom_node node) {
-        if(bucket == parent) {
-            meta_context::from(*ctx).value[bucket].custom = std::move(node);
-        } else if(invoke == nullptr) {
-            find_member_or_assert()->custom = std::move(node);
-        } else {
-            find_overload_or_assert()->custom = std::move(node);
-        }
-    }
-
-public:
-    basic_meta_factory(meta_ctx &area, meta_type_node node)
-        : ctx{&area},
-          parent{node.info->hash()},
-          bucket{parent},
-          details{node.details.get()} {
-        if(details == nullptr) {
-            node.details = std::make_shared<meta_type_descriptor>();
-            meta_context::from(*ctx).value[parent] = node;
-            details = node.details.get();
-        }
-    }
-
-private:
-    meta_ctx *ctx{};
-    id_type parent{};
-    id_type bucket{};
-    invoke_type *invoke{};
-    meta_type_descriptor *details{};
-};
+    return parent.details->func.insert_or_assign(id, std::move(node)).first->second;
+}
 
 } // namespace internal
-/*! @endcond */
 
 /**
- * @brief Meta factory to be used for reflection purposes.
+ * Internal details not to be documented.
+ * @endcond
+ */
+
+/**
+ * @brief Basic meta factory to be used for reflection purposes.
  * @tparam Type Reflected type for which the factory was created.
  */
 template<typename Type>
-class meta_factory: private internal::basic_meta_factory {
-    using base_type = internal::basic_meta_factory;
-
+class meta_factory {
     template<typename Setter, auto Getter, typename Policy, std::size_t... Index>
-    [[deprecated("use variant types or conversion support")]]
     void data(const id_type id, std::index_sequence<Index...>) noexcept {
         using data_type = std::invoke_result_t<decltype(Getter), Type &>;
         using args_type = type_list<typename meta_function_helper_t<Type, decltype(value_list_element_v<Index, Setter>)>::args_type...>;
         static_assert(Policy::template value<data_type>, "Invalid return type for the given policy");
 
-        base_type::data(
+        auto &&elem = internal::meta_extend(
+            internal::owner(*ctx, *info),
+            id,
             internal::meta_data_node{
-                id,
                 /* this is never static */
                 (std::is_member_object_pointer_v<decltype(value_list_element_v<Index, Setter>)> && ... && std::is_const_v<std::remove_reference_t<data_type>>) ? internal::meta_traits::is_const : internal::meta_traits::is_none,
                 Setter::size,
                 &internal::resolve<std::remove_cv_t<std::remove_reference_t<data_type>>>,
-                &meta_arg<type_list<type_list_element_t<static_cast<std::size_t>(type_list_element_t<Index, args_type>::size != 1u), type_list_element_t<Index, args_type>>...>>,
+                &meta_arg<type_list<type_list_element_t<type_list_element_t<Index, args_type>::size != 1u, type_list_element_t<Index, args_type>>...>>,
                 +[](meta_handle instance, meta_any value) { return (meta_setter<Type, value_list_element_v<Index, Setter>>(*instance.operator->(), value.as_ref()) || ...); },
                 &meta_getter<Type, Getter, Policy>});
+
+        bucket = &elem.prop;
     }
 
 public:
@@ -179,15 +100,28 @@ public:
      * @param area The context into which to construct meta types.
      */
     meta_factory(meta_ctx &area) noexcept
-        : internal::basic_meta_factory{area, internal::resolve<Type>(internal::meta_context::from(area))} {}
+        : ctx{&area},
+          bucket{},
+          info{&type_id<Type>()} {
+        auto &&elem = internal::owner(*ctx, *info);
+
+        if(!elem.details) {
+            elem.details = std::make_shared<internal::meta_type_descriptor>();
+        }
+
+        bucket = &elem.details->prop;
+    }
 
     /**
      * @brief Assigns a custom unique identifier to a meta type.
      * @param id A custom unique identifier.
-     * @return A meta factory for the given type.
+     * @return An extended meta factory for the given type.
      */
-    meta_factory type(const id_type id) noexcept {
-        base_type::type(id);
+    auto type(const id_type id) noexcept {
+        auto &&elem = internal::owner(*ctx, *info);
+        ENTT_ASSERT(elem.id == id || !resolve(*ctx, id), "Duplicate identifier");
+        bucket = &elem.details->prop;
+        elem.id = id;
         return *this;
     }
 
@@ -200,10 +134,11 @@ public:
      * @return A meta factory for the parent type.
      */
     template<typename Base>
-    meta_factory base() noexcept {
+    auto base() noexcept {
         static_assert(!std::is_same_v<Type, Base> && std::is_base_of_v<Base, Type>, "Invalid base type");
         auto *const op = +[](const void *instance) noexcept { return static_cast<const void *>(static_cast<const Base *>(static_cast<const Type *>(instance))); };
-        base_type::insert_or_assign(internal::meta_base_node{type_id<Base>().hash(), &internal::resolve<Base>, op});
+        internal::owner(*ctx, *info).details->base.insert_or_assign(type_id<Base>().hash(), internal::meta_base_node{&internal::resolve<Base>, op});
+        bucket = nullptr;
         return *this;
     }
 
@@ -223,7 +158,8 @@ public:
     auto conv() noexcept {
         using conv_type = std::remove_cv_t<std::remove_reference_t<std::invoke_result_t<decltype(Candidate), Type &>>>;
         auto *const op = +[](const meta_ctx &area, const void *instance) { return forward_as_meta(area, std::invoke(Candidate, *static_cast<const Type *>(instance))); };
-        base_type::insert_or_assign(internal::meta_conv_node{type_id<conv_type>().hash(), op});
+        internal::owner(*ctx, *info).details->conv.insert_or_assign(type_id<conv_type>().hash(), internal::meta_conv_node{op});
+        bucket = nullptr;
         return *this;
     }
 
@@ -237,10 +173,11 @@ public:
      * @return A meta factory for the parent type.
      */
     template<typename To>
-    meta_factory conv() noexcept {
+    auto conv() noexcept {
         using conv_type = std::remove_cv_t<std::remove_reference_t<To>>;
         auto *const op = +[](const meta_ctx &area, const void *instance) { return forward_as_meta(area, static_cast<To>(*static_cast<const Type *>(instance))); };
-        base_type::insert_or_assign(internal::meta_conv_node{type_id<conv_type>().hash(), op});
+        internal::owner(*ctx, *info).details->conv.insert_or_assign(type_id<conv_type>().hash(), internal::meta_conv_node{op});
+        bucket = nullptr;
         return *this;
     }
 
@@ -255,14 +192,15 @@ public:
      *
      * @tparam Candidate The actual function to use as a constructor.
      * @tparam Policy Optional policy (no policy set by default).
-     * @return A meta factory for the parent type.
+     * @return An extended meta factory for the parent type.
      */
     template<auto Candidate, typename Policy = as_is_t>
-    meta_factory ctor() noexcept {
+    auto ctor() noexcept {
         using descriptor = meta_function_helper_t<Type, decltype(Candidate)>;
         static_assert(Policy::template value<typename descriptor::return_type>, "Invalid return type for the given policy");
         static_assert(std::is_same_v<std::remove_cv_t<std::remove_reference_t<typename descriptor::return_type>>, Type>, "The function doesn't return an object of the required type");
-        base_type::insert_or_assign(internal::meta_ctor_node{type_id<typename descriptor::args_type>().hash(), descriptor::args_type::size, &meta_arg<typename descriptor::args_type>, &meta_construct<Type, Candidate, Policy>});
+        internal::owner(*ctx, *info).details->ctor.insert_or_assign(type_id<typename descriptor::args_type>().hash(), internal::meta_ctor_node{descriptor::args_type::size, &meta_arg<typename descriptor::args_type>, &meta_construct<Type, Candidate, Policy>});
+        bucket = nullptr;
         return *this;
     }
 
@@ -274,16 +212,17 @@ public:
      * type that can be invoked with parameters whose types are those given.
      *
      * @tparam Args Types of arguments to use to construct an instance.
-     * @return A meta factory for the parent type.
+     * @return An extended meta factory for the parent type.
      */
     template<typename... Args>
-    meta_factory ctor() noexcept {
+    auto ctor() noexcept {
         // default constructor is already implicitly generated, no need for redundancy
         if constexpr(sizeof...(Args) != 0u) {
             using descriptor = meta_function_helper_t<Type, Type (*)(Args...)>;
-            base_type::insert_or_assign(internal::meta_ctor_node{type_id<typename descriptor::args_type>().hash(), descriptor::args_type::size, &meta_arg<typename descriptor::args_type>, &meta_construct<Type, Args...>});
+            internal::owner(*ctx, *info).details->ctor.insert_or_assign(type_id<typename descriptor::args_type>().hash(), internal::meta_ctor_node{descriptor::args_type::size, &meta_arg<typename descriptor::args_type>, &meta_construct<Type, Args...>});
         }
 
+        bucket = nullptr;
         return *this;
     }
 
@@ -306,10 +245,11 @@ public:
      * @return A meta factory for the parent type.
      */
     template<auto Func>
-    meta_factory dtor() noexcept {
+    auto dtor() noexcept {
         static_assert(std::is_invocable_v<decltype(Func), Type &>, "The function doesn't accept an object of the type provided");
         auto *const op = +[](void *instance) { std::invoke(Func, *static_cast<Type *>(instance)); };
-        base_type::dtor(internal::meta_dtor_node{op});
+        internal::owner(*ctx, *info).dtor = internal::meta_dtor_node{op};
+        bucket = nullptr;
         return *this;
     }
 
@@ -324,17 +264,18 @@ public:
      * @tparam Data The actual variable to attach to the meta type.
      * @tparam Policy Optional policy (no policy set by default).
      * @param id Unique identifier.
-     * @return A meta factory for the parent type.
+     * @return An extended meta factory for the parent type.
      */
     template<auto Data, typename Policy = as_is_t>
-    meta_factory data(const id_type id) noexcept {
+    auto data(const id_type id) noexcept {
         if constexpr(std::is_member_object_pointer_v<decltype(Data)>) {
             using data_type = std::invoke_result_t<decltype(Data), Type &>;
             static_assert(Policy::template value<data_type>, "Invalid return type for the given policy");
 
-            base_type::data(
+            auto &&elem = internal::meta_extend(
+                internal::owner(*ctx, *info),
+                id,
                 internal::meta_data_node{
-                    id,
                     /* this is never static */
                     std::is_const_v<std::remove_reference_t<data_type>> ? internal::meta_traits::is_const : internal::meta_traits::is_none,
                     1u,
@@ -342,6 +283,8 @@ public:
                     &meta_arg<type_list<std::remove_cv_t<std::remove_reference_t<data_type>>>>,
                     &meta_setter<Type, Data>,
                     &meta_getter<Type, Data, Policy>});
+
+            bucket = &elem.prop;
         } else {
             using data_type = std::remove_pointer_t<decltype(Data)>;
 
@@ -351,15 +294,18 @@ public:
                 static_assert(Policy::template value<data_type>, "Invalid return type for the given policy");
             }
 
-            base_type::data(
+            auto &&elem = internal::meta_extend(
+                internal::owner(*ctx, *info),
+                id,
                 internal::meta_data_node{
-                    id,
-                    ((!std::is_pointer_v<decltype(Data)> || std::is_const_v<data_type>) ? internal::meta_traits::is_const : internal::meta_traits::is_none) | internal::meta_traits::is_static,
+                    ((std::is_same_v<Type, std::remove_cv_t<std::remove_reference_t<data_type>>> || std::is_const_v<std::remove_reference_t<data_type>>) ? internal::meta_traits::is_const : internal::meta_traits::is_none) | internal::meta_traits::is_static,
                     1u,
                     &internal::resolve<std::remove_cv_t<std::remove_reference_t<data_type>>>,
                     &meta_arg<type_list<std::remove_cv_t<std::remove_reference_t<data_type>>>>,
                     &meta_setter<Type, Data>,
                     &meta_getter<Type, Data, Policy>});
+
+            bucket = &elem.prop;
         }
 
         return *this;
@@ -383,37 +329,43 @@ public:
      * @tparam Getter The actual function to use as a getter.
      * @tparam Policy Optional policy (no policy set by default).
      * @param id Unique identifier.
-     * @return A meta factory for the parent type.
+     * @return An extended meta factory for the parent type.
      */
     template<auto Setter, auto Getter, typename Policy = as_is_t>
-    meta_factory data(const id_type id) noexcept {
-        using descriptor = meta_function_helper_t<Type, decltype(Getter)>;
-        static_assert(Policy::template value<typename descriptor::return_type>, "Invalid return type for the given policy");
+    auto data(const id_type id) noexcept {
+        using data_type = std::invoke_result_t<decltype(Getter), Type &>;
+        static_assert(Policy::template value<data_type>, "Invalid return type for the given policy");
 
         if constexpr(std::is_same_v<decltype(Setter), std::nullptr_t>) {
-            base_type::data(
+            auto &&elem = internal::meta_extend(
+                internal::owner(*ctx, *info),
+                id,
                 internal::meta_data_node{
-                    id,
                     /* this is never static */
                     internal::meta_traits::is_const,
                     0u,
-                    &internal::resolve<std::remove_cv_t<std::remove_reference_t<typename descriptor::return_type>>>,
+                    &internal::resolve<std::remove_cv_t<std::remove_reference_t<data_type>>>,
                     &meta_arg<type_list<>>,
                     &meta_setter<Type, Setter>,
                     &meta_getter<Type, Getter, Policy>});
+
+            bucket = &elem.prop;
         } else {
             using args_type = typename meta_function_helper_t<Type, decltype(Setter)>::args_type;
 
-            base_type::data(
+            auto &&elem = internal::meta_extend(
+                internal::owner(*ctx, *info),
+                id,
                 internal::meta_data_node{
-                    id,
                     /* this is never static nor const */
                     internal::meta_traits::is_none,
                     1u,
-                    &internal::resolve<std::remove_cv_t<std::remove_reference_t<typename descriptor::return_type>>>,
-                    &meta_arg<type_list<type_list_element_t<static_cast<std::size_t>(args_type::size != 1u), args_type>>>,
+                    &internal::resolve<std::remove_cv_t<std::remove_reference_t<data_type>>>,
+                    &meta_arg<type_list<type_list_element_t<args_type::size != 1u, args_type>>>,
                     &meta_setter<Type, Setter>,
                     &meta_getter<Type, Getter, Policy>});
+
+            bucket = &elem.prop;
         }
 
         return *this;
@@ -434,11 +386,10 @@ public:
      * @tparam Getter The actual getter function.
      * @tparam Policy Optional policy (no policy set by default).
      * @param id Unique identifier.
-     * @return A meta factory for the parent type.
+     * @return An extended meta factory for the parent type.
      */
     template<typename Setter, auto Getter, typename Policy = as_is_t>
-    [[deprecated("use variant types or conversion support")]]
-    meta_factory data(const id_type id) noexcept {
+    auto data(const id_type id) noexcept {
         data<Setter, Getter, Policy>(id, std::make_index_sequence<Setter::size>{});
         return *this;
     }
@@ -454,53 +405,56 @@ public:
      * @tparam Candidate The actual function to attach to the meta type.
      * @tparam Policy Optional policy (no policy set by default).
      * @param id Unique identifier.
-     * @return A meta factory for the parent type.
+     * @return An extended meta factory for the parent type.
      */
     template<auto Candidate, typename Policy = as_is_t>
-    meta_factory func(const id_type id) noexcept {
+    auto func(const id_type id) noexcept {
         using descriptor = meta_function_helper_t<Type, decltype(Candidate)>;
         static_assert(Policy::template value<typename descriptor::return_type>, "Invalid return type for the given policy");
 
-        base_type::func(
+        auto &&elem = internal::meta_extend(
+            internal::owner(*ctx, *info),
+            id,
             internal::meta_func_node{
-                id,
                 (descriptor::is_const ? internal::meta_traits::is_const : internal::meta_traits::is_none) | (descriptor::is_static ? internal::meta_traits::is_static : internal::meta_traits::is_none),
                 descriptor::args_type::size,
                 &internal::resolve<std::conditional_t<std::is_same_v<Policy, as_void_t>, void, std::remove_cv_t<std::remove_reference_t<typename descriptor::return_type>>>>,
                 &meta_arg<typename descriptor::args_type>,
                 &meta_invoke<Type, Candidate, Policy>});
 
+        bucket = &elem.prop;
         return *this;
     }
 
     /**
-     * @brief Sets traits on the last created meta object.
+     * @brief Assigns a property to the last meta object created.
      *
-     * The assigned value must be an enum and intended as a bitmask.
+     * Both the key and the value (if any) must be at least copy constructible.
      *
-     * @tparam Value Type of the traits value.
-     * @param value Traits value.
-     * @return A meta factory for the parent type.
+     * @tparam Value Optional type of the property value.
+     * @param id Property key.
+     * @param value Optional property value.
+     * @return An extended meta factory for the given type.
      */
-    template<typename Value>
-    meta_factory traits(const Value value) {
-        static_assert(std::is_enum_v<Value>, "Invalid enum type");
-        base_type::traits(internal::user_to_meta_traits(value));
+    template<typename... Value>
+    meta_factory prop(id_type id, [[maybe_unused]] Value &&...value) {
+        ENTT_ASSERT(bucket != nullptr, "Meta object does not support properties");
+
+        if constexpr(sizeof...(Value) == 0u) {
+            (*bucket)[id] = internal::meta_prop_node{&internal::resolve<void>};
+        } else {
+            (*bucket)[id] = internal::meta_prop_node{
+                &internal::resolve<std::decay_t<Value>>...,
+                std::make_shared<std::decay_t<Value>>(std::forward<Value>(value))...};
+        }
+
         return *this;
     }
 
-    /**
-     * @brief Sets user defined data that will never be used by the library.
-     * @tparam Value Type of user defined data to store.
-     * @tparam Args Types of arguments to use to construct the user data.
-     * @param args Parameters to use to initialize the user data.
-     * @return A meta factory for the parent type.
-     */
-    template<typename Value, typename... Args>
-    meta_factory custom(Args &&...args) {
-        base_type::custom(internal::meta_custom_node{type_id<Value>().hash(), std::make_shared<Value>(std::forward<Args>(args)...)});
-        return *this;
-    }
+private:
+    meta_ctx *ctx;
+    dense_map<id_type, internal::meta_prop_node, identity> *bucket;
+    const type_info *info;
 };
 
 /**
@@ -516,7 +470,10 @@ public:
  * @return A meta factory for the given type.
  */
 template<typename Type>
-[[nodiscard]] [[deprecated("use meta_factory directly instead")]] auto meta(meta_ctx &ctx) noexcept {
+[[nodiscard]] auto meta(meta_ctx &ctx) noexcept {
+    auto &&context = internal::meta_context::from(ctx);
+    // make sure the type exists in the context before returning a factory
+    context.value.try_emplace(type_id<Type>().hash(), internal::resolve<Type>(context));
     return meta_factory<Type>{ctx};
 }
 
@@ -532,7 +489,7 @@ template<typename Type>
  * @return A meta factory for the given type.
  */
 template<typename Type>
-[[nodiscard]] [[deprecated("use meta_factory directly instead")]] auto meta() noexcept {
+[[nodiscard]] auto meta() noexcept {
     return meta<Type>(locator<meta_ctx>::value_or());
 }
 

src/entt/meta/fwd.hpp

@@ -11,7 +11,7 @@ class meta_any;
 
 struct meta_handle;
 
-struct meta_custom;
+struct meta_prop;
 
 struct meta_data;
 

src/entt/meta/node.hpp

@@ -5,10 +5,9 @@
 #include <memory>
 #include <type_traits>
 #include <utility>
-#include <vector>
 #include "../config/config.h"
+#include "../container/dense_map.hpp"
 #include "../core/attribute.h"
-#include "../core/bit.hpp"
 #include "../core/enum.hpp"
 #include "../core/fwd.hpp"
 #include "../core/type_info.hpp"
@@ -23,7 +22,11 @@ class meta_any;
 class meta_type;
 struct meta_handle;
 
-/*! @cond TURN_OFF_DOXYGEN */
+/**
+ * @cond TURN_OFF_DOXYGEN
+ * Internal details not to be documented.
+ */
+
 namespace internal {
 
 enum class meta_traits : std::uint32_t {
@@ -36,52 +39,31 @@ enum class meta_traits : std::uint32_t {
     is_array = 0x0020,
     is_enum = 0x0040,
     is_class = 0x0080,
-    is_pointer = 0x0100,
-    is_pointer_like = 0x0200,
-    is_sequence_container = 0x0400,
-    is_associative_container = 0x0800,
-    _user_defined_traits = 0xFFFF,
-    _entt_enum_as_bitmask = 0xFFFF
+    is_meta_pointer_like = 0x0100,
+    is_meta_sequence_container = 0x0200,
+    is_meta_associative_container = 0x0400,
+    _entt_enum_as_bitmask
 };
 
-template<typename Type>
-[[nodiscard]] auto meta_to_user_traits(const meta_traits traits) noexcept {
-    static_assert(std::is_enum_v<Type>, "Invalid enum type");
-    constexpr auto shift = popcount(static_cast<std::underlying_type_t<meta_traits>>(meta_traits::_user_defined_traits));
-    return Type{static_cast<std::underlying_type_t<Type>>(static_cast<std::underlying_type_t<meta_traits>>(traits) >> shift)};
-}
-
-template<typename Type>
-[[nodiscard]] auto user_to_meta_traits(const Type value) noexcept {
-    static_assert(std::is_enum_v<Type>, "Invalid enum type");
-    constexpr auto shift = popcount(static_cast<std::underlying_type_t<meta_traits>>(meta_traits::_user_defined_traits));
-    const auto traits = static_cast<std::underlying_type_t<internal::meta_traits>>(static_cast<std::underlying_type_t<Type>>(value));
-    ENTT_ASSERT(traits < ((~static_cast<std::underlying_type_t<meta_traits>>(meta_traits::_user_defined_traits)) >> shift), "Invalid traits");
-    return meta_traits{traits << shift};
-}
-
 struct meta_type_node;
 
-struct meta_custom_node {
-    id_type type{};
-    std::shared_ptr<void> value;
+struct meta_prop_node {
+    meta_type_node (*type)(const meta_context &) noexcept {};
+    std::shared_ptr<void> value{};
 };
 
 struct meta_base_node {
-    id_type type{};
-    meta_type_node (*resolve)(const meta_context &) noexcept {};
+    meta_type_node (*type)(const meta_context &) noexcept {};
     const void *(*cast)(const void *) noexcept {};
 };
 
 struct meta_conv_node {
-    id_type type{};
     meta_any (*conv)(const meta_ctx &, const void *){};
 };
 
 struct meta_ctor_node {
     using size_type = std::size_t;
 
-    id_type id{};
     size_type arity{0u};
     meta_type (*arg)(const meta_ctx &, const size_type) noexcept {};
     meta_any (*invoke)(const meta_ctx &, meta_any *const){};
@@ -94,43 +76,42 @@ struct meta_dtor_node {
 struct meta_data_node {
     using size_type = std::size_t;
 
-    id_type id{};
     meta_traits traits{meta_traits::is_none};
     size_type arity{0u};
     meta_type_node (*type)(const meta_context &) noexcept {};
     meta_type (*arg)(const meta_ctx &, const size_type) noexcept {};
     bool (*set)(meta_handle, meta_any){};
-    meta_any (*get)(meta_handle){};
-    meta_custom_node custom{};
+    meta_any (*get)(const meta_ctx &, meta_handle){};
+    dense_map<id_type, meta_prop_node, identity> prop{};
 };
 
 struct meta_func_node {
     using size_type = std::size_t;
 
-    id_type id{};
     meta_traits traits{meta_traits::is_none};
     size_type arity{0u};
     meta_type_node (*ret)(const meta_context &) noexcept {};
     meta_type (*arg)(const meta_ctx &, const size_type) noexcept {};
-    meta_any (*invoke)(meta_handle, meta_any *const){};
-    std::shared_ptr<meta_func_node> next;
-    meta_custom_node custom{};
+    meta_any (*invoke)(const meta_ctx &, meta_handle, meta_any *const){};
+    std::shared_ptr<meta_func_node> next{};
+    dense_map<id_type, meta_prop_node, identity> prop{};
 };
 
 struct meta_template_node {
     using size_type = std::size_t;
 
     size_type arity{0u};
-    meta_type_node (*resolve)(const meta_context &) noexcept {};
+    meta_type_node (*type)(const meta_context &) noexcept {};
     meta_type_node (*arg)(const meta_context &, const size_type) noexcept {};
 };
 
 struct meta_type_descriptor {
-    std::vector<meta_ctor_node> ctor;
-    std::vector<meta_base_node> base;
-    std::vector<meta_conv_node> conv;
-    std::vector<meta_data_node> data;
-    std::vector<meta_func_node> func;
+    dense_map<id_type, meta_ctor_node, identity> ctor{};
+    dense_map<id_type, meta_base_node, identity> base{};
+    dense_map<id_type, meta_conv_node, identity> conv{};
+    dense_map<id_type, meta_data_node, identity> data{};
+    dense_map<id_type, meta_func_node, identity> func{};
+    dense_map<id_type, meta_prop_node, identity> prop{};
 };
 
 struct meta_type_node {
@@ -147,69 +128,29 @@ struct meta_type_node {
     meta_any (*from_void)(const meta_ctx &, void *, const void *){};
     meta_template_node templ{};
     meta_dtor_node dtor{};
-    meta_custom_node custom{};
-    std::shared_ptr<meta_type_descriptor> details;
+    std::shared_ptr<meta_type_descriptor> details{};
 };
 
-template<auto Member, typename Type, typename Value>
-[[nodiscard]] auto *find_member(Type &from, const Value value) {
-    for(auto &&elem: from) {
-        if((elem.*Member) == value) {
-            return &elem;
-        }
-    }
-
-    return static_cast<typename Type::value_type *>(nullptr);
-}
-
-[[nodiscard]] inline auto *find_overload(meta_func_node *curr, std::remove_pointer_t<decltype(meta_func_node::invoke)> *const ref) {
-    while((curr != nullptr) && (curr->invoke != ref)) { curr = curr->next.get(); }
-    return curr;
-}
-
-template<auto Member>
-[[nodiscard]] auto *look_for(const meta_context &context, const meta_type_node &node, const id_type id) {
-    using value_type = typename std::remove_reference_t<decltype((node.details.get()->*Member))>::value_type;
-
-    if(node.details) {
-        if(auto *member = find_member<&value_type::id>((node.details.get()->*Member), id); member != nullptr) {
-            return member;
-        }
-
-        for(auto &&curr: node.details->base) {
-            if(auto *elem = look_for<Member>(context, curr.resolve(context), id); elem) {
-                return elem;
-            }
-        }
-    }
-
-    return static_cast<value_type *>(nullptr);
-}
-
 template<typename Type>
 meta_type_node resolve(const meta_context &) noexcept;
 
 template<typename... Args>
 [[nodiscard]] auto meta_arg_node(const meta_context &context, type_list<Args...>, [[maybe_unused]] const std::size_t index) noexcept {
+    [[maybe_unused]] std::size_t pos{};
     meta_type_node (*value)(const meta_context &) noexcept = nullptr;
-
-    if constexpr(sizeof...(Args) != 0u) {
-        std::size_t pos{};
-        ((value = (pos++ == index ? &resolve<std::remove_cv_t<std::remove_reference_t<Args>>> : value)), ...);
-    }
-
+    ((value = (pos++ == index ? &resolve<std::remove_cv_t<std::remove_reference_t<Args>>> : value)), ...);
     ENTT_ASSERT(value != nullptr, "Out of bounds");
     return value(context);
 }
 
-[[nodiscard]] inline const void *try_cast(const meta_context &context, const meta_type_node &from, const type_info &to, const void *instance) noexcept {
-    if((from.info != nullptr) && *from.info == to) {
+[[nodiscard]] inline const void *try_cast(const meta_context &context, const meta_type_node &from, const meta_type_node &to, const void *instance) noexcept {
+    if(from.info && to.info && *from.info == *to.info) {
         return instance;
     }
 
     if(from.details) {
         for(auto &&curr: from.details->base) {
-            if(const void *elem = try_cast(context, curr.resolve(context), to, curr.cast(instance)); elem) {
+            if(const void *elem = try_cast(context, curr.second.type(context), to, curr.second.cast(instance)); elem) {
                 return elem;
             }
         }
@@ -218,33 +159,6 @@ template<typename... Args>
     return nullptr;
 }
 
-template<typename Func>
-[[nodiscard]] inline auto try_convert(const meta_context &context, const meta_type_node &from, const type_info &to, const bool arithmetic_or_enum, const void *instance, Func func) {
-    if(from.info && *from.info == to) {
-        return func(instance, from);
-    }
-
-    if(from.details) {
-        for(auto &&elem: from.details->conv) {
-            if(elem.type == to.hash()) {
-                return func(instance, elem);
-            }
-        }
-
-        for(auto &&curr: from.details->base) {
-            if(auto other = try_convert(context, curr.resolve(context), to, arithmetic_or_enum, curr.cast(instance), func); other) {
-                return other;
-            }
-        }
-    }
-
-    if(from.conversion_helper && arithmetic_or_enum) {
-        return func(instance, from.conversion_helper);
-    }
-
-    return func(instance);
-}
-
 [[nodiscard]] inline const meta_type_node *try_resolve(const meta_context &context, const type_info &info) noexcept {
     const auto it = context.value.find(info.hash());
     return it != context.value.end() ? &it->second : nullptr;
@@ -267,10 +181,9 @@ template<typename Type>
             | (std::is_array_v<Type> ? meta_traits::is_array : meta_traits::is_none)
             | (std::is_enum_v<Type> ? meta_traits::is_enum : meta_traits::is_none)
             | (std::is_class_v<Type> ? meta_traits::is_class : meta_traits::is_none)
-            | (std::is_pointer_v<Type> ? meta_traits::is_pointer : meta_traits::is_none)
-            | (is_meta_pointer_like_v<Type> ? meta_traits::is_pointer_like : meta_traits::is_none)
-            | (is_complete_v<meta_sequence_container_traits<Type>> ? meta_traits::is_sequence_container : meta_traits::is_none)
-            | (is_complete_v<meta_associative_container_traits<Type>> ? meta_traits::is_associative_container : meta_traits::is_none),
+            | (is_meta_pointer_like_v<Type> ? meta_traits::is_meta_pointer_like : meta_traits::is_none)
+            | (is_complete_v<meta_sequence_container_traits<Type>> ? meta_traits::is_meta_sequence_container : meta_traits::is_none)
+            | (is_complete_v<meta_associative_container_traits<Type>> ? meta_traits::is_meta_associative_container : meta_traits::is_none),
         size_of_v<Type>,
         &resolve<Type>,
         &resolve<std::remove_cv_t<std::remove_pointer_t<Type>>>};
@@ -282,27 +195,22 @@ template<typename Type>
     }
 
     if constexpr(std::is_arithmetic_v<Type>) {
-        node.conversion_helper = +[](void *lhs, const void *rhs) {
-            return lhs ? static_cast<double>(*static_cast<Type *>(lhs) = static_cast<Type>(*static_cast<const double *>(rhs))) : static_cast<double>(*static_cast<const Type *>(rhs));
+        node.conversion_helper = +[](void *bin, const void *value) {
+            return bin ? static_cast<double>(*static_cast<Type *>(bin) = static_cast<Type>(*static_cast<const double *>(value))) : static_cast<double>(*static_cast<const Type *>(value));
         };
     } else if constexpr(std::is_enum_v<Type>) {
-        node.conversion_helper = +[](void *lhs, const void *rhs) {
-            return lhs ? static_cast<double>(*static_cast<Type *>(lhs) = static_cast<Type>(static_cast<std::underlying_type_t<Type>>(*static_cast<const double *>(rhs)))) : static_cast<double>(*static_cast<const Type *>(rhs));
+        node.conversion_helper = +[](void *bin, const void *value) {
+            return bin ? static_cast<double>(*static_cast<Type *>(bin) = static_cast<Type>(static_cast<std::underlying_type_t<Type>>(*static_cast<const double *>(value)))) : static_cast<double>(*static_cast<const Type *>(value));
         };
     }
 
-    if constexpr(!std::is_void_v<Type> && !std::is_function_v<Type>) {
-        node.from_void = +[](const meta_ctx &ctx, void *elem, const void *celem) {
-            if(elem && celem) { // ownership construction request
-                return meta_any{ctx, std::in_place, static_cast<std::decay_t<Type> *>(elem)};
+    if constexpr(!std::is_same_v<Type, void> && !std::is_function_v<Type>) {
+        node.from_void = +[](const meta_ctx &ctx, void *element, const void *as_const) {
+            if(element) {
+                return meta_any{ctx, std::in_place_type<std::decay_t<Type> &>, *static_cast<std::decay_t<Type> *>(element)};
             }
 
-            if(elem) { // non-const reference construction request
-                return meta_any{ctx, std::in_place_type<std::decay_t<Type> &>, *static_cast<std::decay_t<Type> *>(elem)};
-            }
-
-            // const reference construction request
-            return meta_any{ctx, std::in_place_type<const std::decay_t<Type> &>, *static_cast<const std::decay_t<Type> *>(celem)};
+            return meta_any{ctx, std::in_place_type<const std::decay_t<Type> &>, *static_cast<const std::decay_t<Type> *>(as_const)};
         };
     }
 
@@ -317,7 +225,11 @@ template<typename Type>
 }
 
 } // namespace internal
-/*! @endcond */
+
+/**
+ * Internal details not to be documented.
+ * @endcond
+ */
 
 } // namespace entt