Bug 217697 - REGRESSION: fast/canvas/webgl/context-attributes-alpha.html fails
Summary: REGRESSION: fast/canvas/webgl/context-attributes-alpha.html fails
Alias: None
Product: WebKit
Classification: Unclassified
Component: WebGL (show other bugs)
Version: WebKit Local Build
Hardware: Unspecified Unspecified
: P2 Normal
Assignee: Kimmo Kinnunen
Keywords: InRadar
Depends on: 217212
Blocks: webglgpup
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Reported: 2020-10-14 01:30 PDT by Kimmo Kinnunen
Modified: 2020-10-14 12:55 PDT (History)
7 users (show)

See Also:

Patch (3.82 KB, patch)
2020-10-14 01:46 PDT, Kimmo Kinnunen
no flags Details | Formatted Diff | Diff

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Description Kimmo Kinnunen 2020-10-14 01:30:24 PDT
REGRESSION: fast/canvas/webgl/context-attributes-alpha.html fails
after bug 217212
Comment 1 Kimmo Kinnunen 2020-10-14 01:46:08 PDT
Created attachment 411306 [details]
Comment 2 Antti Koivisto 2020-10-14 02:00:04 PDT
Comment on attachment 411306 [details]

View in context: https://bugs.webkit.org/attachment.cgi?id=411306&action=review

> Source/WebCore/ChangeLog:10
> +        WebGLLayer contentsOpaque. Neither the EWS nor the local testing

Why is. that?
Comment 3 EWS 2020-10-14 02:18:27 PDT
Committed r268446: <https://trac.webkit.org/changeset/268446>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 411306 [details].
Comment 4 Radar WebKit Bug Importer 2020-10-14 02:19:25 PDT
Comment 5 Kimmo Kinnunen 2020-10-14 02:36:42 PDT
>> +        WebGLLayer contentsOpaque. Neither the EWS nor the local testing
> Why is. that?

It is unclear at this point, I'll investigate this more.

The knowns:
- I developed the patch on iMac with AMD card. I thought I ran the tests as supposed.
- I noticed the regression on MacBook Pro with Intel/AMD, with automatic switching on
- EWS runs Intel opus
- Intel GPUs have bugs around IOSurfaces and their alpha channels. ANGLE tries to work around them.
- The test and the expected.html both use the WebGL canvas alpha feature, which turned out to have the bug
- The test should be run on Mac and expected to work
- The -expected.html probably should not use the exact same code as what the test is testing, but it's somewhat tricky to alter the content in GPU-agnostic way

The unknowns:
- Did I run the tests locally? 
- Does Intel alpha bugs, ANGLE workarounds and the bug in question cancel each other out in EWS?
- Does EWS run fast/canvas/webgl/context-attributes-alpha.html 
- If the bugs cancel each other out, why don't they cancel out with my MacBook Pro? Does it use the AMD part or are the drivers different or is there a bug in ANGLE workaround selection.

I'll try to investigate the unknowns
Comment 6 Alexey Proskuryakov 2020-10-14 12:48:48 PDT
To clarify, EWS is Mac Pros with AMD GPUs.
Comment 7 Alexey Proskuryakov 2020-10-14 12:55:23 PDT
Bots that saw this failure were all newer AMD ones: