[WebGPU] Transparent canvases are not supported in WebGPU

[mwyrzykowski]

1ab851a

[WebGPU] Transparent canvases are not supported in WebGPU
https://bugs.webkit.org/show_bug.cgi?id=279373
rdar://135563124

Reviewed by Tadeu Zagallo.

The canvas alphaMode defaults to 'opaque', use 'premultiplied' for transparency.

This resolves the lack of transparency with https://webgpu.github.io/webgpu-samples/?sample=transparentCanvas

* Source/WebCore/html/canvas/GPUCanvasContextCocoa.mm:
(WebCore::GPUCanvasContextCocoa::configure):

Canonical link: https://commits.webkit.org/286121@main

a31a11c

Misc	iOS, visionOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	🛠 win
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	🧪 wpe-wk2	🧪 win-tests
✅ 🧪 webkitperl	🧪 ios-wk2	✅ 🧪 api-mac	🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	🧪 mac-wk1	🛠 wpe-cairo
	🧪 api-ios	✅ 🧪 mac-wk2	✅ 🛠 gtk
	✅ 🛠 vision	✅ 🧪 mac-AS-debug-wk2	🧪 gtk-wk2
	✅ 🛠 vision-sim	✅ 🧪 mac-wk2-stress	🧪 api-gtk
✅ 🛠 🧪 merge	🧪 vision-wk2	✅ 🧪 mac-intel-wk2
	✅ 🛠 tv	🛠 mac-safer-cpp
	🛠 tv-sim
	🛠 watch
	✅ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on previous version of this PR (hash 50c6d8b)

Misc	iOS, visionOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 win
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2	✅ 🧪 win-tests
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	✅ 🛠 wpe-cairo
	✅ 🧪 api-ios	✅ 🧪 mac-wk2	✅ 🛠 gtk
	✅ 🛠 vision	✅ 🧪 mac-AS-debug-wk2	✅ 🧪 gtk-wk2
	✅ 🛠 vision-sim	✅ 🧪 mac-wk2-stress	✅ 🧪 api-gtk
	✅ 🧪 vision-wk2	✅ 🧪 mac-intel-wk2
	✅ 🛠 tv	✅ 🛠 mac-safer-cpp
	✅ 🛠 tv-sim
	✅ 🛠 watch
	✅ 🛠 watch-sim

[tadeuzagallo]

Might be worth mentioning the sample in the commit message or adding a regression test.

[webkit-early-warning-system]

EWS run on current version of this PR (hash a31a11c)

Misc	iOS, visionOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	🛠 win
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	🧪 wpe-wk2	🧪 win-tests
✅ 🧪 webkitperl	🧪 ios-wk2	✅ 🧪 api-mac	🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	🧪 mac-wk1	🛠 wpe-cairo
	🧪 api-ios	✅ 🧪 mac-wk2	✅ 🛠 gtk
	✅ 🛠 vision	✅ 🧪 mac-AS-debug-wk2	🧪 gtk-wk2
	✅ 🛠 vision-sim	✅ 🧪 mac-wk2-stress	🧪 api-gtk
✅ 🛠 🧪 merge	🧪 vision-wk2	✅ 🧪 mac-intel-wk2
	✅ 🛠 tv	🛠 mac-safer-cpp
	🛠 tv-sim
	🛠 watch
	✅ 🛠 watch-sim

[mwyrzykowski]

Might be worth mentioning the sample in the commit message or adding a regression test.

I added a link since I'm not sure how to test CALayer's (isOpaque) property which is the only point where this breaks.

[webkit-commit-queue]

Committed 286121@main (1ab851a): https://commits.webkit.org/286121@main

Reviewed commits have been landed. Closing PR #36089 and removing active labels.