From 230a5d8a9347dde220a047aba802ed4ff556cf8a Mon Sep 17 00:00:00 2001
From: Mathias Agopian <mathias@google.com>
Date: Fri, 31 Oct 2025 14:28:45 -0700
Subject: [PATCH] Fix GLES2 UBO emulation (#9392)

The binding cache didn't take into account the UBO offset.

FIXES=[456802974]
---
 filament/backend/src/opengl/GLDescriptorSet.cpp | 5 +----
 filament/backend/src/opengl/OpenGLProgram.cpp   | 9 +++++++--
 filament/backend/src/opengl/OpenGLProgram.h     | 3 ++-
 3 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/filament/backend/src/opengl/GLDescriptorSet.cpp b/filament/backend/src/opengl/GLDescriptorSet.cpp
index fc5f7b7e87..aacee30679 100644
--- a/filament/backend/src/opengl/GLDescriptorSet.cpp
+++ b/filament/backend/src/opengl/GLDescriptorSet.cpp
@@ -303,13 +303,10 @@ void GLDescriptorSet::bind(
                     offset += offsets[dynamicOffsetIndex++];
                 }
                 if (arg.bo) {
-                    auto buffer = static_cast<char const*>(arg.bo->gl.buffer) + offset;
-                    p.updateUniforms(bindingPoint, arg.bo->gl.id, buffer, arg.bo->age);
+                    p.updateUniforms(bindingPoint, arg.bo->gl.id, arg.bo->gl.buffer, arg.bo->age, offset);
                 }
             } else if constexpr (std::is_same_v<T, Sampler>) {
                 GLuint const unit = p.getTextureUnit(set, binding);
-
-
                 if (arg.handle) {
                     GLTexture const* const t = handleAllocator.handle_cast<GLTexture*>(arg.handle);
                     gl.bindTexture(unit, t->gl.target, t->gl.id, t->gl.external);
diff --git a/filament/backend/src/opengl/OpenGLProgram.cpp b/filament/backend/src/opengl/OpenGLProgram.cpp
index 8975d001f6..74e433dc99 100644
--- a/filament/backend/src/opengl/OpenGLProgram.cpp
+++ b/filament/backend/src/opengl/OpenGLProgram.cpp
@@ -262,20 +262,25 @@ void OpenGLProgram::initializeProgramState(OpenGLContext& context, GLuint progra
 }
 
 void OpenGLProgram::updateUniforms(
-        uint32_t index, GLuint id, void const* buffer, uint16_t age) const noexcept {
+        uint32_t const index, GLuint const id, void const* buffer,
+        uint16_t const age, uint32_t const offset) const noexcept {
     assert_invariant(mUniformsRecords);
     assert_invariant(buffer);
 
     // only update the uniforms if the UBO has changed since last time we updated
     UniformsRecord const& records = mUniformsRecords[index];
-    if (records.id == id && records.age == age) {
+    if (records.id == id && records.age == age && records.offset == offset) {
         return;
     }
     records.id = id;
     records.age = age;
+    records.offset = offset;
 
     assert_invariant(records.uniforms.size() == records.locations.size());
 
+    // apply the offset to the buffer
+    buffer = static_cast<char const*>(buffer) + offset;
+
     for (size_t i = 0, c = records.uniforms.size(); i < c; i++) {
         Program::Uniform const& u = records.uniforms[i];
         GLint const loc = records.locations[i];
diff --git a/filament/backend/src/opengl/OpenGLProgram.h b/filament/backend/src/opengl/OpenGLProgram.h
index 4d4a1ca17b..c5ceccfbc0 100644
--- a/filament/backend/src/opengl/OpenGLProgram.h
+++ b/filament/backend/src/opengl/OpenGLProgram.h
@@ -88,7 +88,7 @@ public:
     }
 
     // For ES2 only
-    void updateUniforms(uint32_t index, GLuint id, void const* buffer, uint16_t age) const noexcept;
+    void updateUniforms(uint32_t index, GLuint id, void const* buffer, uint16_t age, uint32_t offset) const noexcept;
     void setRec709ColorSpace(bool rec709) const noexcept;
 
     PushConstantBundle getPushConstants() {
@@ -123,6 +123,7 @@ private:
         LocationInfo locations;
         mutable GLuint id = 0;
         mutable uint16_t age = std::numeric_limits<uint16_t>::max();
+        mutable uint32_t offset = 0;
     };
     UniformsRecord const* mUniformsRecords = nullptr;
     GLint mRec709Location : 24;     // 4 bytes