Bug 242673 – A containing block with overflow:hidden wrongly clips descendant position:fixed

• Status: RESOLVED
• Resolution: FIXED
• Component: CSS

[Fujii Hironori]

Created attachment 460843 [details]
test case

A containing block with overflow:hidden wrongly clips descendant position:fixed

[Fujii Hironori]

Created attachment 460844 [details]
test case

[Fujii Hironori]

Created attachment 460845 [details]
Patch

[Fujii Hironori]

EWS reported two regressions.

Regressions: Unexpected image-only failures (2)
  transforms/2d/perspective-not-fixed-container.html [ ImageOnlyFailure ]
  transforms/2d/preserve3d-not-fixed-container.html [ ImageOnlyFailure ]

However, WebKit now behave same with Chrome and Firefox. This seems progressions.
I think I can remove the tests.

[Fujii Hironori]

Rather than removing the tests, I should create a test for the new behavior.

[Fujii Hironori]

Created attachment 460866 [details]
Patch

[Fujii Hironori]

Created attachment 460867 [details]
Patch

[Fujii Hironori]

Created attachment 460878 [details]
Patch

[Karl Dubost]

Created attachment 460880 [details]
rendering in Safari, firefox, chrome

As a reference. 

Safari Technology Preview 16.0 Release 148 (Safari 16.0, WebKit 18614.1.17.3)
Firefox Nightly 104.0a1
Google Chrome Canary 105.0.5178.0

[Radar WebKit Bug Importer]

<rdar://problem/97298971>

[Fujii Hironori]

Could anyone review?

[Simon Fraser (smfr)]

Comment on attachment 460878 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=460878&action=review

> LayoutTests/transforms/containing-block-for-fixed-expected.html:22
> +    scrollTo(0, 300);

On iOS this scroll will probably need a waitUntilDone/await UIHelper.waitForScrollCompletion() for the pixel test to correctly reflect the scroll.

[Fujii Hironori]

Comment on attachment 460878 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=460878&action=review

Thank you very much.

>> LayoutTests/transforms/containing-block-for-fixed-expected.html:22
>> +    scrollTo(0, 300);
> 
> On iOS this scroll will probably need a waitUntilDone/await UIHelper.waitForScrollCompletion() for the pixel test to correctly reflect the scroll.

I copied the code from transforms/2d/perspective-not-fixed-container.html, and this test isn't flaky for iOS.
"await UIHelper.waitForScrollCompletion()" can't be used with scrollTo() because scrollTo scrolls synchronously by default.
Some tests are using "await UIHelper.waitForScrollCompletion()", but they don't use it with synchronous scrollTo().
I think this code won't be flaky.

[EWS]

Committed 252721@main (d188f7e50205): <https://commits.webkit.org/252721@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 460878 [details].