Bug 225443

Summary: will-change: position should not create a containing block for position: fixed elements
Product: WebKit Reporter: Tim Nguyen (:ntim) <ntim>
Component: Layout and RenderingAssignee: Tim Nguyen (:ntim) <ntim>
Status: RESOLVED FIXED    
Severity: Normal CC: bfulgham, changseok, esprehn+autocc, ews-watchlist, glenn, koivisto, kondapallykalyan, pdr, simon.fraser, webkit-bug-importer, zalan
Priority: P2 Keywords: InRadar
Version: WebKit Nightly Build   
Hardware: Unspecified   
OS: Unspecified   
See Also: https://bugs.chromium.org/p/chromium/issues/detail?id=1205953
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Description Tim Nguyen (:ntim) 2021-05-06 02:30:34 PDT 
Not sure why tbh, but Chrome & Edge also fail here. Only Firefox passes.
Comment 2 Radar WebKit Bug Importer 2021-05-13 02:31:17 PDT 
<rdar://problem/77958400>
Comment 3 Tim Nguyen (:ntim) 2021-05-16 01:49:01 PDT 
I got some clarification from Emilio:

No value of `position` triggers a containing block for a position: fixed; child element, so `will-change: position` also shouldn't trigger a containing block.
Comment 4 Tim Nguyen (:ntim) 2021-05-16 02:01:02 PDT 
Created attachment 428779 [details]
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Comment 5 Simon Fraser (smfr) 2021-05-16 08:26:59 PDT 
Comment on attachment 428779 [details]
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View in context: https://bugs.webkit.org/attachment.cgi?id=428779&action=review

> Source/WebCore/ChangeLog:8
> +        Marked relevant WPT as pass.

Please write more words here about how you are undoing a previous change. Reference that other commit, and reference the test that is exercising the change.
Comment 6 Tim Nguyen (:ntim) 2021-05-16 09:31:21 PDT 
Created attachment 428791 [details]
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Comment 7 Tim Nguyen (:ntim) 2021-05-16 09:35:59 PDT 
Created attachment 428792 [details]
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Comment 8 Tim Nguyen (:ntim) 2021-05-16 09:37:54 PDT 
Created attachment 428793 [details]
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Comment 9 EWS 2021-05-17 03:09:11 PDT 
Committed r277579 (237806@main): <https://commits.webkit.org/237806@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 428793 [details].