Add support for builtin DComp swapchains #7550

n1ght-hunter · 2025-04-16T06:17:44Z

Description
add support for builtin DComp swapchains 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.

wgpu-hal/src/dx12/mod.rs

wgpu-types/src/instance.rs

wgpu-hal/src/dx12/mod.rs

n1ght-hunter · 2025-04-17T12:51:38Z

will get to this in the next day or two

…tions

… traits

…options

…d of use_dcomp

…-hunter/wgpu into dev/windows-os-transparent

n1ght-hunter · 2025-05-06T16:52:13Z

@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

wgpu-hal/src/dx12/dcomp.rs

Anutrix · 2025-05-30T06:35:09Z

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 · 2025-05-30T18:56:58Z

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

melody-rs · 2025-06-03T22:02:28Z

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

n1ght-hunter · 2025-06-10T16:18:56Z

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

cwfitzgerald · 2025-06-25T18:51:33Z

Boop :)

MarijnS95 · 2025-07-06T15:30:47Z

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 :)

wgpu-hal/src/dx12/dcomp.rs

n1ght-hunter · 2025-07-10T11:07:06Z

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.

…ositionCreateDevice2

…ition initialization

n1ght-hunter · 2025-08-04T06:41:18Z

i have updated this pr now. i believe i have fixed all comments except for title of pr.
im terrible with coming up with titles so suggestions are welcome

cwfitzgerald

Sorry for another round of comments, we're almost there!

CHANGELOG.md

wgpu-types/src/instance.rs

cwfitzgerald · 2025-08-13T23:49:12Z

wgpu-types/src/instance.rs

+    /// Use the DXGI presentation system.
+    #[default]
+    Dxgi,
+    /// Use the DirectComposition presentation system.


Suggested change

/// Use the DirectComposition presentation system.

/// Use a DXGI swapchain made from a DirectComposition visual made from the window.

///

/// This supports transparent windows, but does not support fullscreen optimization.

@cwfitzgerald these user-facing documentation bits need links to upstream documentation exactly how all this works. Perhaps we need to explain that users cannot or should not use this in conjunction with SurfaceTargetUnsafe::CompositionVisual/SurfaceTargetUnsafe::SurfaceHandle if they're already managing a layer tree externally (themselves).

Can you backup (link) exactly how this doesn't support "fullscreen optimization" (like borderless fullscreen)? I was under the impression that this uses flip-style present as well which should allow for hardware-compositable/presentable planes in the sawpchain?

EDIT: Or are you saying this because translucent surfaces inevitably require the underlying plane(s) to be rendered and blended (hopefully accelerated in hardware by MPO blending) too? If the user disables alpha blending on the swapchain it should still be able to make this optimization.

Should we also recommend users to set WS_EX_NOREDIRECTIONBITMAP?

these user-facing documentation bits need links to upstream documentation exactly how all this works. Perhaps we need to explain that users cannot or should not use this in conjunction with SurfaceTargetUnsafe::CompositionVisual/SurfaceTargetUnsafe::SurfaceHandle if they're already managing a layer tree externally (themselves).

I agree, though we can leave this to another PR and spin off an issue from this one, I don't want to hold it up too long as I've already let it sit a while.

Can you backup (link) exactly how this doesn't support "fullscreen optimization" (like borderless fullscreen)? I was under the impression that this uses flip-style present as well which should allow for hardware-compositable/presentable planes in the sawpchain?

I thought I had a conversation about this with Jesse on the d3d12 discord a while ago but I can't find it, so I'll ask again and see what they say.

Should we also recommend users to set WS_EX_NOREDIRECTIONBITMAP?

I honestly don't know.

Re: mpo

I was wrong! Things made from visuals are still eligible for full screen optimization.

wgpu-types/src/instance.rs

Co-authored-by: Connor Fitzgerald <[email protected]>

n1ght-hunter · 2025-08-14T13:20:50Z

@cwfitzgerald done :)

MarijnS95 · 2025-08-14T13:36:00Z

wgpu-types/src/instance.rs

+            .as_deref()?
+            .to_lowercase();
+        match value.as_str() {
+            "dcomp" => Some(Self::DirectComposition),


Also update the argument name?

oh ya was gonna ask we wanted to update that. though i could see leaving it so its short in the cli

I think having both would be reasonable as well.

MarijnS95 · 2025-08-14T13:37:24Z

wgpu-hal/src/dx12/dcomp.rs

+            profiling::scope!("DirectComposition::DCompositionCreateDevice");
+            unsafe { DirectComposition::DCompositionCreateDevice2(None) }.map_err(|err| {
+                log::error!("DirectComposition::DCompositionCreateDevice failed: {err}");
+                crate::SurfaceError::Other("DirectComposition::DCompositionCreateDevice")


It's surprising that SurfaceError doesn't have an inner error like InstanceError.

MarijnS95 · 2025-08-14T13:44:18Z

wgpu-types/src/instance.rs

+    /// Use the DXGI presentation system.
+    #[default]
+    Dxgi,
+    /// Use the DirectComposition presentation system.


@cwfitzgerald these user-facing documentation bits need links to upstream documentation exactly how all this works. Perhaps we need to explain that users cannot or should not use this in conjunction with SurfaceTargetUnsafe::CompositionVisual/SurfaceTargetUnsafe::SurfaceHandle if they're already managing a layer tree externally (themselves).

Can you backup (link) exactly how this doesn't support "fullscreen optimization" (like borderless fullscreen)? I was under the impression that this uses flip-style present as well which should allow for hardware-compositable/presentable planes in the sawpchain?

EDIT: Or are you saying this because translucent surfaces inevitably require the underlying plane(s) to be rendered and blended (hopefully accelerated in hardware by MPO blending) too? If the user disables alpha blending on the swapchain it should still be able to make this optimization.

CHANGELOG.md

MarijnS95 · 2025-08-14T13:53:26Z

wgpu-hal/src/dx12/dcomp.rs

+    /// Creates a DirectComposition device and a target for the given window handle.
+    pub unsafe fn init(hwnd: &HWND) -> Result<Self, crate::SurfaceError> {
+        let dcomp_device: DirectComposition::IDCompositionDevice = {
+            profiling::scope!("DirectComposition::DCompositionCreateDevice");


Just wondering, is it normal to wrap every external API call - especially these that are well off the hot path - in a profiling scope?

perhaps just a single profile scope for the whole init scope?

Yeah lets do a single scope - generally the decision for what to scope depends on how long it takes, so if there's a single item that takes a long time, scope that, but for processes that only really take a while in aggregate, we can use a single scope.

MarijnS95 · 2025-08-14T13:54:47Z

wgpu-types/src/instance.rs

+    /// Use the DXGI presentation system.
+    #[default]
+    Dxgi,
+    /// Use the DirectComposition presentation system.


Should we also recommend users to set WS_EX_NOREDIRECTIONBITMAP?

melody-rs · 2025-08-14T21:17:42Z

Could we maybe get an example showing how to use DComp to make window transparency work?

Window transparency with wgpu has been a frustration for a while now and having a working example to base things off of would be super helpful imo

n1ght-hunter · 2025-08-15T03:43:06Z

Could we maybe get an example showing how to use DComp to make window transparency work?

Window transparency with wgpu has been a frustration for a while now and having a working example to base things off of would be super helpful imo

sure i have a testing example i can its basiclly just a triangle with partly clear background

Co-authored-by: Marijn Suijten <[email protected]>

cwfitzgerald · 2025-08-20T17:30:09Z

Could we maybe get an example showing how to use DComp to make window transparency work?

I think we should, but we can do this as a follow up.

n1ght-hunter added 4 commits April 13, 2025 15:57

add dx12 dcomp option to backend options

e6d7e5f

impl dcomp for the dx12 backend

c328699

Merge branch 'gfx-rs:trunk' into dev/windows-os-transparent

3f91a00

Merge branch 'gfx-rs:trunk' into dev/windows-os-transparent

b8131bf

n1ght-hunter requested review from crowlKats and a team as code owners April 16, 2025 06:17

Add Dcomp support to DX12 backend in changelog

1f70a9a

cwfitzgerald requested changes Apr 16, 2025

View reviewed changes

wgpu-hal/src/dx12/mod.rs Outdated Show resolved Hide resolved

wgpu-types/src/instance.rs Outdated Show resolved Hide resolved

wgpu-hal/src/dx12/mod.rs Outdated Show resolved Hide resolved

wgpu-hal/src/dx12/mod.rs Show resolved Hide resolved

cwfitzgerald self-assigned this Apr 16, 2025

n1ght-hunter added 7 commits April 23, 2025 16:28

move decomp to another module

60a747c

refactor: replace use_dcomp with presentation_system in Dx12BackendOp…

8b012f3

…tions

refactor: enhance Dx12PresentationSystem with Copy, PartialEq, and Eq…

91d98af

… traits

refactor: replace use_dcomp with presentation_system in Dx12 backend …

bae60c3

…options

Merge branch 'trunk' into dev/windows-os-transparent

194a685

refactor: update Dx12BackendOptions to use presentation_system instea…

32ce523

…d of use_dcomp

Merge branch 'dev/windows-os-transparent' of https://github.com/n1ght…

157c1c6

…-hunter/wgpu into dev/windows-os-transparent

n1ght-hunter requested a review from cwfitzgerald April 23, 2025 04:48

Merge branch 'trunk' into dev/windows-os-transparent

cd41a6e

cwfitzgerald requested changes May 29, 2025

View reviewed changes

wgpu-hal/src/dx12/dcomp.rs Outdated Show resolved Hide resolved

wgpu-hal/src/dx12/dcomp.rs Outdated Show resolved Hide resolved

MarijnS95 reviewed Jul 6, 2025

View reviewed changes

wgpu-hal/src/dx12/dcomp.rs Outdated Show resolved Hide resolved

This was referenced Jul 6, 2025

Increased input-to-screen latency on vulkan #6932

Open

Extended Presentation API Investigation #2869

Open

GPeaky mentioned this pull request Jul 25, 2025

Window transparency does not work under Windows iced-rs/iced#2525

Open

4 tasks

n1ght-hunter added 6 commits August 2, 2025 00:40

refactor(dx12): update DirectComposition device creation to use DComp…

73579d3

…ositionCreateDevice2

Merge branch 'trunk' into dev/windows-os-transparent

cae67ca

cleanup dcomp create device types

830bf2b

clean dcomp code

f40d9b5

refactor(dx12): remove unused Direct3D 11 dependencies from Cargo.toml

2302705

refactor(dx12): remove unnecessary device parameter from DirectCompos…

504dfa1

…ition initialization

n1ght-hunter requested review from cwfitzgerald and MarijnS95 August 1, 2025 12:51

cwfitzgerald changed the title ~~Add dcomp on windows~~ Add support for builtin DComp swapchains Aug 13, 2025

cwfitzgerald requested changes Aug 13, 2025

View reviewed changes

n1ght-hunter and others added 8 commits August 15, 2025 01:06

Update wgpu-types/src/instance.rs

62758fe

Co-authored-by: Connor Fitzgerald <[email protected]>

Update wgpu-types/src/instance.rs

25f68fa

Co-authored-by: Connor Fitzgerald <[email protected]>

Update wgpu-types/src/instance.rs

7b5d124

Co-authored-by: Connor Fitzgerald <[email protected]>

Update wgpu-types/src/instance.rs

eab2de6

Co-authored-by: Connor Fitzgerald <[email protected]>

Update CHANGELOG.md

a9ddf45

Co-authored-by: Connor Fitzgerald <[email protected]>

Update CHANGELOG.md

55659a1

Co-authored-by: Connor Fitzgerald <[email protected]>

Merge branch 'trunk' into dev/windows-os-transparent

92afbbc

fmt

783e730

n1ght-hunter requested a review from cwfitzgerald August 14, 2025 13:20

MarijnS95 reviewed Aug 14, 2025

View reviewed changes

Update CHANGELOG.md

1a9ff41

Co-authored-by: Marijn Suijten <[email protected]>

-    /// Use the DirectComposition presentation system.
+    /// Use a DXGI swapchain made from a DirectComposition visual made from the window.
+    ///
+    /// This supports transparent windows, but does not support fullscreen optimization.

Add support for builtin DComp swapchains #7550

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n1ght-hunter commented Apr 16, 2025 •

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