Implement LowLatencyDxgiSwapChain window transparency

[lindexi]

What does the pull request do?

See #20615

Base on: #20757

• Implement LowLatencyDxgiSwapChain window transparency
• Using the expectedPixelSize in DxgiRenderTarget.BeginDrawCore

What's the difference between this change and DirectComposition in Transparency mode?

When using LowLatencyDxgiSwapChain with Transparency mode, the IDXGISwapChain1 object is created via the CreateSwapChainForComposition method. Rendering operations are then executed using this SwapChain; once rendering is complete, the IDXGISwapChain1.Present method is invoked to submit the rendered content.

In contrast, DirectComposition directly acquires a texture for rendering by calling IDCompositionVirtualSurface.BeginDraw. After finishing rendering, the IDCompositionDevice2.Commit and IDCompositionDevice2.WaitForCommitCompletion methods are called to wait for the rendering process to finalize.

Based on my practical tests, I observed that using LowLatencyDxgiSwapChain in Transparency mode yields higher frame rates and lower rendering latency compared to DirectComposition.

Testing the RenderDemo in my device:

• Screen: 3840x2160 (4K) + 100% DPI
• CPU: i5-12450H
• GPU: - (Integrated graphics card)

// In RenderDemo App.xaml.cs:
        static AppBuilder BuildAvaloniaApp()
           => AppBuilder.Configure<App>()
+              .With(new Win32PlatformOptions
+              {
+                  OverlayPopups = true,
+                   CompositionMode = [Win32CompositionMode.LowLatencyDxgiSwapChain]
+               })
                .UsePlatformDetect()
                .WithDeveloperTools()
                .LogToTrace();

Win32CompositionMode	Frame rate	GPU for RenderDemo	GPU for DWM
WinUIComposition + Transparency	25-30	27%	45%
WinUIComposition + not Transparency	30	31%	12%
LowLatencyDxgiSwapChain + Transparency	60	45%	30%
LowLatencyDxgiSwapChain + not Transparency	60	70%	0%

What is the current behavior?

What is the updated/expected behavior with this PR?

How was the solution implemented (if it's not obvious)?

Checklist

• Added unit tests (if possible)?
• Added XML documentation to any related classes?
• Consider submitting a PR to https://github.com/AvaloniaUI/avalonia-docs with user documentation

Breaking changes

Obsoletions / Deprecations

Fixed issues

Fixes #20615

[avaloniaui-bot]

You can test this PR using the following package version. 12.0.999-cibuild0063311-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[avaloniaui-bot]

You can test this PR using the following package version. 12.0.999-cibuild0063319-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]