Honor the surface's alphaMode on the Vulkan and D3D swapchains - #69
Honor the surface's alphaMode on the Vulkan and D3D swapchains#69d3x0r wants to merge 2 commits into
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👋 Thanks for your contribution! Your PR has been imported to Gerrit. |
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Latest revision failed to import to Gerrit (our code review tool), due to the merge conflict. Could you update the PR? |
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Import worked! I think some of the comments on Gerrit still need to be addressed though. |
ChooseConfig hardcoded VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR outside of Android, so a surface configured with a transparent alphaMode was composited as opaque. Convert the WebGPU enum directly: Surface.cpp has already resolved Auto and validated the mode against the capabilities PhysicalDeviceVk reports. Add a transparent-window mode (T) to ManualSurfaceTest so the alpha modes can be checked against the desktop.
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SwapChainD3D hardcoded DXGI_ALPHA_MODE_IGNORE even though PhysicalDeviceD3D advertises Premultiplied as supported. DXGI rejects a non-opaque alpha mode on CreateSwapChainForHwnd, so a premultiplied HWND surface is now created with CreateSwapChainForComposition and bound to the window through a DirectComposition visual, whose lifetime follows the swapchain across recycling.
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Dawn hardcoded an opaque composite alpha in both swapchain backends, so a surface configured with a transparent
alphaModewas composited as opaque even though the adapter advertised the mode as supported.Vulkan:
SwapChainVk::ChooseConfigconverts the WebGPU enum directly. Auto and unsupported modes are already resolved and validated inSurface.cpp, so the Android-only fallback loop is gone.D3D:
SwapChainD3Dasked forDXGI_ALPHA_MODE_IGNORE. DXGI rejects a non-opaque alpha mode onCreateSwapChainForHwnd, so a premultiplied HWND surface is created withCreateSwapChainForCompositionand bound to the window through a DirectComposition visual. Recycling an existing swapchain now also requires the alpha mode to be unchanged, sinceAlphaModeis fixed at creation and a composition swapchain is not interchangeable with an HWND one.Tested with
ManualSurfaceTest:Topens a window with a transparent framebuffer,Rswitches to the clear-cycle render mode (its clear is premultiplied and cycles its alpha) andAcycles alpha modes. On Windows that covers the backends presenting directly to the HWND; the D3D composition path additionally needs a window created withWS_EX_NOREDIRECTIONBITMAP, which GLFW does not do and which cannot be set afterwards, so it was verified against a Node addon embedding Dawn (@d3x0r/sack-gui) driving three.jsWebGPURendererover such a window, on D3D12 and Vulkan, Windows 11 + NVIDIA.