Win32PlatformOptions.UseCompositionSwapchain - #22115
Open
kekekeks wants to merge 2 commits into
Open
Conversation
…der thread Adds an opaque CompositionTarget.TopLevelSpecificSceneInfo bag (with the corresponding ITopLevelImpl property and changed callback) that travels through the composition transport and arrives in RenderTargetSceneInfo. The Win32 backend publishes the theme variant through it. The WinUI/DComp composited window render targets now apply blur/mica visual state in BeginDraw, based on the transparency level and theme variant from the scene info, inside the same transaction as the frame. The UI-thread ICompositionEffectsSurface.SetBlur path is removed, so effect changes can no longer race the render thread and produce frames with mismatched alpha mode and blur state. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01TrfgSxPjyUvvKsAPFZoLR1
When enabled with the WinUIComposition or DirectComposition composition mode, the window content is rendered into a DXGI flip-model swapchain created via CreateSwapChainForComposition and attached as the content of the window's visual, instead of a composition drawing surface. This allows DWM to use optimized presentation modes (independent flip) for fullscreen windows and reduces presentation latency. The swapchain uses Present(0, 0) without ALLOW_TEARING, and is recreated when the transparency level changes alpha mode between IGNORE and PREMULTIPLIED. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01TrfgSxPjyUvvKsAPFZoLR1
kekekeks
changed the title
3 tasks
maxkatz6
reviewed
Aug 31, 2026
Comment on lines
+83
to
+102
| var desc = new DXGI_SWAP_CHAIN_DESC1 | ||
| { | ||
| Width = (uint)size.Width, | ||
| Height = (uint)size.Height, | ||
| Format = DXGI_FORMAT.DXGI_FORMAT_B8G8R8A8_UNORM, | ||
| SampleDesc = { Count = 1, Quality = 0 }, | ||
| BufferUsage = DxgiRenderTarget.DXGI_USAGE_RENDER_TARGET_OUTPUT, | ||
| BufferCount = 2, | ||
| Scaling = DXGI_SCALING.DXGI_SCALING_STRETCH, | ||
| // FLIP_DISCARD is not available on Windows 8.x | ||
| SwapEffect = Win32Platform.WindowsVersion >= PlatformConstants.Windows10 ? | ||
| DXGI_SWAP_EFFECT.DXGI_SWAP_EFFECT_FLIP_DISCARD : | ||
| DXGI_SWAP_EFFECT.DXGI_SWAP_EFFECT_FLIP_SEQUENTIAL, | ||
| // Premultiplied alpha increases the DWM composition cost and prevents optimized | ||
| // presentation modes, so it's only used when the window is actually transparent, | ||
| // see https://github.com/AvaloniaUI/Avalonia/issues/20643 | ||
| AlphaMode = isTransparency ? | ||
| DXGI_ALPHA_MODE.DXGI_ALPHA_MODE_PREMULTIPLIED : | ||
| DXGI_ALPHA_MODE.DXGI_ALPHA_MODE_IGNORE | ||
| }; |
Member
There was a problem hiding this comment.
nit: there is some duplication with WinUI embedded backend -
Avalonia/src/Windows/Avalonia.Win32/OpenGl/Angle/SwapChainGlSurface.cs
Lines 108 to 119 in a61d80b
I think it's fine to keep these separated, winui one is angle+winui specific. But just FYI.
Member
There was a problem hiding this comment.
I suppose WinUI backend could implement ISwapchainVisualHost and reuse part
maxkatz6
reviewed
Aug 31, 2026
| /// WinUI composition path, looser visual synchronization during interactive resize. | ||
| /// The default value is null, which lets the framework decide (currently: disabled). | ||
| /// </summary> | ||
| public bool? UseCompositionSwapchain { get; set; } |
Member
There was a problem hiding this comment.
Do we deprecate Win32CompositionMode.LowLatencyDxgiSwapChain?
maxkatz6
reviewed
Aug 31, 2026
| /// WinUI composition path, looser visual synchronization during interactive resize. | ||
| /// The default value is null, which lets the framework decide (currently: disabled). | ||
| /// </summary> | ||
| public bool? UseCompositionSwapchain { get; set; } |
Member
There was a problem hiding this comment.
Alternative API:
public enum Win32CompositionMode
{
WinUIComposition = 1,
DirectComposition = 2,
+ [Obsolete("Use WinUICompositionSwapchain or DirectCompositionSwapchain")]
LowLatencyDxgiSwapChain = 3,
RedirectionSurface = 4,
+ WinUICompositionSwapchain = 5,
+ DirectCompositionSwapchain = 6,
}
Member
There was a problem hiding this comment.
Not sure if it's really better, but what do you think.
UseCompositionSwapchain on its own doesn't make sense without composition mode. And less root options API pollution. But then we are only limited to enums in composition mode. With this another API we would also lose "null default" state, but not sure if it's necessary.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
This PR introduces
Win32PlatformOptions.UseCompositionSwapchainthat usesCreateSwapchainForCompositioninstead of our existing frugal "dear-DWM-give-us-a-texture-chunk-to-render-into" approach. This enables Direct/Independent Flip for our primary supported WinUI and DirectComposition modes instead of "low latency swapchain" mode we've attached via duct tape a while ago.Merge after #22114