Add dcomp on windows

[n1ght-hunter]

Connections
#3486
#7108
#5150

Description
This adds dcomp support to the dx12 backend.
My main goal for this was to get window transparency to work on windows

Testing
Tested using a basic wgpu app with transparency

Squash or Rebase?
Squash

Checklist

• Run cargo fmt.
• Run taplo format.
• Run cargo clippy --tests. If applicable, add:
  • --target wasm32-unknown-unknown
• Run cargo xtask test to run tests.
• If this contains user-facing changes, add a CHANGELOG.md entry.

I dont know if its normal or not but when running cargo xtask test i had 201 tests fail with code 0xc0000005: Invalid access to memory location. (os error 998) this is run on windows 10

[cwfitzgerald]

Generally looking good, some comments.

[n1ght-hunter]

will get to this in the next day or two

[n1ght-hunter]

@cwfitzgerald would you be able to re review when you get time thanks

[cwfitzgerald]

Sorry for the delay, looks good in general with a few small comments. I also think that the hardcoded list of blending modes needs to be adjusted based on if DXGI or DComp is selected

[cwfitzgerald]

This function should also be unsafe

[cwfitzgerald]

Suggested change

	let dcomp_device = {
	profiling::scope!("DirectComposition::DCompositionCreateDevice");
	unsafe {
	DirectComposition::DCompositionCreateDevice::<
	_,
	DirectComposition::IDCompositionDevice,
	>(&dxgi_device)
	let dcomp_device: DirectComposition::IDCompositionDevice = {
	profiling::scope!("DirectComposition::DCompositionCreateDevice");
	unsafe {
	DirectComposition::DCompositionCreateDevice(&dxgi_device)

This feels cleaner

[Anutrix]

Might totally be unfounded and not apply here but DirectComposition on Windows has issues with NVIDIA GPU when used with multiple monitors with different and high(60+) refresh rates. This was seen on Firefox so might be specific to it.
Recent ticket: https://bugzilla.mozilla.org/show_bug.cgi?id=1968876 . Couldn't find original ticket.

[cwfitzgerald]

I definitely wouldn't worry about it here. That issue seems to be Windows 10 specific too.

[melody-rs]

Oh! Thank you for doing this, transparency support in wgpu has been a pretty big pain point for me in the past

[n1ght-hunter]

Im just traveling abroad atm should be able to get to this in the next week or so

[cwfitzgerald]

Boop :)

[MarijnS95]

So if I understand this correctly, normally one would create and manage a composition (device, target) externally, and pass either the IDCompositionVisual (where wgpu will insert the internally-crated IDXGISwapChain1 as content into the visual) or a HANDLE to an opaque "composition surface" (which the caller should insert as the content of a visual themselves - useful for cross-process sharing) into wgpu surface creation. Allowing users to render into arbitrary surfaces with wgpu while possibly combining it with a much more complicated composition/transformation tree and surfaces filled by other sources.

This PR seems to abstract away the most basic form of that, by creating and managing that DirectComposition device and a single Visual spanning the full Target that wraps the window (where hopefully "someone" disables the backing redirection buffer...) so that users no longer have to deal with it?

i.e. maybe this PR should be retitled and have a better description of what it achieves. Technically "dcomp on Windows" is already supported :)

[MarijnS95]

As long as Create(Virtual)Surface() or BeginDraw() is not used, I'm quite sure you can just call DCompositionCreateDevice2(NULL) (None in Rust), without having to use the entire Direct3D11on12 emulation/mapping layer.

https://learn.microsoft.com/en-us/windows/win32/api/dcomp/nf-dcomp-dcompositioncreatedevice2#remarks:

If the renderingDevice parameter is NULL then the returned DirectComposition device cannot directly create DirectComposition surface objects. In particular, IDCompositionDevice2::CreateSurface and IDCompositionDevice2::CreateVirtualSurface methods return E_INVALIDARG, regardless of the supplied parameters. However, such a DirectComposition device object can still be used to indirectly create surfaces if the application creates a surface factory object via the IDCompositionDevice2::CreateSurfaceFactory method.

[n1ght-hunter]

thanks i will have a look

[n1ght-hunter]

sorry ended up being very busy. still traveling :). i will be home in about 3 weeks. should have time to work on it then. maybe before but unlikely. if someone else wants to fix it up no worries from me otherwise i will when i get time.