From b380f0ee73f813482b0a36bc0d966656c8273077 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Branimir=20Karad=C5=BEi=C4=87?= <branimirkaradzic@gmail.com>
Date: Wed, 16 Sep 2026 19:26:46 -0700
Subject: [PATCH] Fixed explicit swap chains in a headless init: MTL
 screenshots, MTL/VK/WGPU window list compaction, MTL/WGPU user depth pipeline
 format. (#3984)

---
 src/renderer_mtl.cpp    | 24 ++++++++++++------------
 src/renderer_vk.cpp     | 12 +++++-------
 src/renderer_webgpu.cpp | 21 +++++++++------------
 src/renderer_webgpu.h   |  1 +
 4 files changed, 27 insertions(+), 31 deletions(-)

diff --git a/src/renderer_mtl.cpp b/src/renderer_mtl.cpp
index ee2d06650..19b0d00b6 100644
--- a/src/renderer_mtl.cpp
+++ b/src/renderer_mtl.cpp
@@ -1787,17 +1787,14 @@ static_assert(BX_COUNTOF(s_accessNames) == Access::Count, "Invalid s_accessNames
 			{
 				--m_numWindows;
 
-				if (m_numWindows > 1)
+				if (m_numWindows != denseIdx)
 				{
 					FrameBufferHandle handle = m_windows[m_numWindows];
-					m_windows[m_numWindows]  = {kInvalidHandle};
-
-					if (m_numWindows != denseIdx)
-					{
-						m_windows[denseIdx] = handle;
-						m_frameBuffers[handle.idx].m_denseIdx = denseIdx;
-					}
+					m_windows[denseIdx] = handle;
+					m_frameBuffers[handle.idx].m_denseIdx = denseIdx;
 				}
+
+				m_windows[m_numWindows] = {kInvalidHandle};
 			}
 		}
 
@@ -5139,6 +5136,8 @@ static_assert(BX_COUNTOF(s_accessNames) == Access::Count, "Invalid s_accessNames
 		murmur.add(m_metalLayer->pixelFormat() );
 		murmur.add(formatColor);
 		murmur.add(formatDepthStencil);
+		murmur.add(NULL != m_backBufferDepth   ? m_backBufferDepth->pixelFormat()   : MTL::PixelFormatInvalid);
+		murmur.add(NULL != m_backBufferStencil ? m_backBufferStencil->pixelFormat() : MTL::PixelFormatInvalid);
 		murmur.add(sampleCount);
 
 		return murmur.end();
@@ -6015,17 +6014,18 @@ static_assert(BX_COUNTOF(s_accessNames) == Access::Count, "Invalid s_accessNames
 				continue;
 			}
 
-			const uint16_t fbhIdx = 0 == ii ? kInvalidHandle : m_windows[ii].idx;
+			const bool     isMainWindow = !isValid(m_windows[ii]);
+			const uint16_t fbhIdx = isMainWindow ? kInvalidHandle : m_windows[ii].idx;
 
-			bool needScreenshot = 0 == ii && NULL != m_capture;
+			bool needScreenshot = isMainWindow && NULL != m_capture;
 
 			for (uint8_t jj = 0, numShots = _render->m_numScreenShots; jj < numShots && !needScreenshot; ++jj)
 			{
 				needScreenshot = _render->m_screenShot[jj].handle.idx == fbhIdx;
 			}
 
-			const uint32_t width  = 0 == ii ? m_mainSwapChain.width  : frameBuffer.m_width;
-			const uint32_t height = 0 == ii ? m_mainSwapChain.height : frameBuffer.m_height;
+			const uint32_t width  = isMainWindow ? m_mainSwapChain.width  : frameBuffer.m_width;
+			const uint32_t height = isMainWindow ? m_mainSwapChain.height : frameBuffer.m_height;
 
 			if (needScreenshot)
 			{
diff --git a/src/renderer_vk.cpp b/src/renderer_vk.cpp
index a5f2d9950..f882cdb18 100644
--- a/src/renderer_vk.cpp
+++ b/src/renderer_vk.cpp
@@ -2911,16 +2911,14 @@ VK_IMPORT_DEVICE
 			if (UINT16_MAX != denseIdx)
 			{
 				--m_numWindows;
-				if (m_numWindows > 1)
+				if (m_numWindows != denseIdx)
 				{
 					FrameBufferHandle handle = m_windows[m_numWindows];
-					m_windows[m_numWindows]  = {kInvalidHandle};
-					if (m_numWindows != denseIdx)
-					{
-						m_windows[denseIdx] = handle;
-						m_frameBuffers[handle.idx].m_denseIdx = denseIdx;
-					}
+					m_windows[denseIdx] = handle;
+					m_frameBuffers[handle.idx].m_denseIdx = denseIdx;
 				}
+
+				m_windows[m_numWindows] = {kInvalidHandle};
 			}
 		}
 
diff --git a/src/renderer_webgpu.cpp b/src/renderer_webgpu.cpp
index 9643b3ca7..900defdba 100644
--- a/src/renderer_webgpu.cpp
+++ b/src/renderer_webgpu.cpp
@@ -2176,16 +2176,14 @@ WGPU_IMPORT
 			if (UINT16_MAX != denseIdx)
 			{
 				--m_numWindows;
-				if (m_numWindows > 1)
+				if (m_numWindows != denseIdx)
 				{
 					FrameBufferHandle handle = m_windows[m_numWindows];
-					m_windows[m_numWindows]  = {kInvalidHandle};
-					if (m_numWindows != denseIdx)
-					{
-						m_windows[denseIdx] = handle;
-						m_frameBuffers[handle.idx].m_denseIdx = denseIdx;
-					}
+					m_windows[denseIdx] = handle;
+					m_frameBuffers[handle.idx].m_denseIdx = denseIdx;
 				}
+
+				m_windows[m_numWindows] = {kInvalidHandle};
 			}
 		}
 
@@ -3442,10 +3440,7 @@ WGPU_IMPORT
 				: NULL
 				;
 
-			const TextureFormat::Enum formatDepthStencil = fb.isSwapChain()
-				? fb.m_swapChain.m_desc.formatDepthStencil
-				: TextureFormat::Enum(fb.m_formatDepthStencil)
-				;
+			const TextureFormat::Enum formatDepthStencil = TextureFormat::Enum(fb.m_formatDepthStencil);
 
 			const bool hasFragmentShader = NULL != program.m_fsh;
 			const bool bgra8Storage = hasBgra8Storage(entries, entryCount);
@@ -3822,7 +3817,7 @@ WGPU_IMPORT
 			{
 				_murmur.add(_fb.m_swapChain.m_viewFormat);
 				_murmur.add(_fb.m_swapChain.m_desc.formatColor);
-				_murmur.add(_fb.m_swapChain.m_desc.formatDepthStencil);
+				_murmur.add(_fb.m_swapChain.m_formatDepthStencil);
 
 				return;
 			}
@@ -5339,6 +5334,8 @@ WGPU_IMPORT
 		wgpuRelease(m_depthStencilView);
 		wgpuRelease(m_msaaTextureView);
 
+		m_formatDepthStencil = uint8_t(TextureFormat::Count);
+
 		if (isValid(m_desc.depth) )
 		{
 			const TextureWGPU& texture = s_renderWGPU->m_textures[m_desc.depth.idx];
diff --git a/src/renderer_webgpu.h b/src/renderer_webgpu.h
index bd88a8c04..bf370afa1 100644
--- a/src/renderer_webgpu.h
+++ b/src/renderer_webgpu.h
@@ -679,6 +679,7 @@ namespace wgpu {
 			, m_msaaTextureView(NULL)
 			, m_depthStencilView(NULL)
 			, m_viewFormat(WGPUTextureFormat_Undefined)
+			, m_formatDepthStencil(uint8_t(TextureFormat::Count) )
 			, m_readable(false)
 		{
 		}