Question about SKColorType in LowLatencyDxgiSwapChain

[lindexi]

As the code shows, Avalonia use DXGI_FORMAT.DXGI_FORMAT_B8G8R8A8_UNORM (know as BGRA 32) when the SwapChain created:

Avalonia/src/Windows/Avalonia.Win32/DirectX/DxgiRenderTarget.cs

Lines 49 to 57 in 1ee1509

	dxgiSwapChainDesc.Format = DXGI_FORMAT.DXGI_FORMAT_B8G8R8A8_UNORM;
	dxgiSwapChainDesc.SampleDesc.Count = 1U;
	dxgiSwapChainDesc.SampleDesc.Quality = 0U;
	dxgiSwapChainDesc.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
	dxgiSwapChainDesc.AlphaMode = DXGI_ALPHA_MODE.DXGI_ALPHA_MODE_IGNORE;
	dxgiSwapChainDesc.Width = (uint)_window.Size.Width;
	dxgiSwapChainDesc.Height = (uint)_window.Size.Height;
	dxgiSwapChainDesc.BufferCount = 2U;
	dxgiSwapChainDesc.SwapEffect = DXGI_SWAP_EFFECT.DXGI_SWAP_EFFECT_FLIP_DISCARD;

But then Avalonia render with SKColorType.Rgba8888 in GlRenderTarget.BeginRenderingSessionCore:

Avalonia/src/Skia/Avalonia.Skia/Gpu/OpenGl/GlRenderTarget.cs

Line 80 in 1ee1509

var colorType = SKColorType.Rgba8888;

I’m not sure how much of a performance cost this process will incur, but it seems that we can use the SKColorType.Bgra8888 pixel format here.

My question is why should use SKColorType.Rgba8888 in GlRenderTarget.BeginRenderingSessionCore?

And I know why use DXGI_FORMAT.DXGI_FORMAT_B8G8R8A8_UNORM here, because as the document says:

We recommend that you use DXGI_FORMAT_B8G8R8A8_UNORM as the pixel format for better performance. This is particularly helpful for software render targets. BGRA format targets perform better than RGBA formats.