Bug 300089

Summary: REGRESSION (Safari 26): Container queries length unit wrong values
Product: WebKit Reporter: diego
Component: Layout and RenderingAssignee: Antti Koivisto <koivisto>
Status: RESOLVED FIXED    
Severity: Normal CC: bfulgham, koivisto, ntim, rniwa, simon.fraser, webkit-bug-importer, zalan
Priority: P2 Keywords: InRadar
Version: Safari 26   
Hardware: iPhone / iPad   
OS: iOS 26   
See Also: https://bugs.webkit.org/show_bug.cgi?id=253939
https://github.com/web-platform-tests/wpt/pull/55368
Attachments:
Description Flags
The same element is attached to two different parents, with one defining a shadow root with only one <slot> element inside none

diego
Reported 2025-10-03 03:12:09 PDT
Created attachment 476948 [details] The same element is attached to two different parents, with one defining a shadow root with only one <slot> element inside This is almost exactly the same issue reported in https://bugs.webkit.org/show_bug.cgi?id=260462, which has been fixed, but now happens when the element containing the container-type property is placed in the light DOM of another element with a shadow ROOT. It is a regression because I couldn't notice this problem in Safari 18.6, which is the version I am using in my desktop, but can be verified in the Safari 26 (I could only test the iOS version, so it needs to be verified in the other versions too). Attached, you can see the reproduction of the issue, that was taken from the one previously linked, with the change to add the element defining the container context to a parent with a shadow root.
Attachments
The same element is attached to two different parents, with one defining a shadow root with only one <slot> element inside (717 bytes, text/html)
2025-10-03 03:12 PDT, diego 		no flags
Details
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Alexey Proskuryakov
Comment 1 2025-10-03 08:33:07 PDT
Thank you for the report! Confirmed that this reproduces on macOS.
Radar WebKit Bug Importer
Comment 2 2025-10-03 08:33:47 PDT
<rdar://problem/161897768>
Antti Koivisto
Comment 3 2025-10-10 09:30:17 PDT
Pull request: https://github.com/WebKit/WebKit/pull/52125
EWS
Comment 4 2025-10-10 12:39:58 PDT
Committed 301324@main (3286a2880158): <https://commits.webkit.org/301324@main> Reviewed commits have been landed. Closing PR #52125 and removing active labels.
Antti Koivisto
Comment 5 2025-10-10 21:41:42 PDT
Submitted web-platform-tests pull request: https://github.com/web-platform-tests/wpt/pull/55368
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