Bug 298709

Summary: Sticky element disappears past a certain scroll threshold and glitches if it contains an element with a backdrop filter
Product: WebKit Reporter: Anthony Catel <paraboul>
Component: Layout and RenderingAssignee: Matt Woodrow <mattwoodrow>
Status: REOPENED    
Severity: Normal CC: bfulgham, commit-queue, simon.fraser, webkit-bug-importer, zalan
Priority: P2 Keywords: InRadar
Version: Safari 26   
Hardware: iPhone / iPad   
OS: iOS 26   
Bug Depends on: 301145    
Bug Blocks:    
Attachments:
Description Flags
Minimal test case.
none
Video showing the bug none

Anthony Catel
Reported 2025-09-11 04:53:14 PDT
Created attachment 476693 [details] Minimal test case. I noticed a strange bug in the navigation menu while testing on Safari 16 (iOS simulator). When scrolling past the maximum bottom threshold: - The sticky element at the top disappears after a certain point. - If the sticky element contains a child with a backdrop filter, that child element disapears first (before the sticky element) and the backdrop effect itself remains visible. I've attached a minimal reproduction test case that highlights the issue in the iOS 26 simulator.
Attachments
Minimal test case. (1.63 KB, text/html)
2025-09-11 04:53 PDT, Anthony Catel 		no flags
Details
Video showing the bug (11.91 MB, video/quicktime)
2025-09-11 04:58 PDT, Anthony Catel 		no flags
Details
View All Add attachment proposed patch, testcase, etc.
Anthony Catel
Comment 1 2025-09-11 04:58:33 PDT
Created attachment 476694 [details] Video showing the bug Here is a video showing the bug
Anthony Catel
Comment 2 2025-09-11 05:01:58 PDT
(In reply to Anthony Catel from comment #0) > Created attachment 476693 [details] > Minimal test case. > > I noticed a strange bug in the navigation menu while testing on Safari 16 > (iOS simulator). > > When scrolling past the maximum bottom threshold: > > - The sticky element at the top disappears after a certain point. > - If the sticky element contains a child with a backdrop filter, that child > element disapears first (before the sticky element) and the backdrop effect > itself remains visible. > > I've attached a minimal reproduction test case that highlights the issue in > the iOS 26 simulator. s/Safari 16/Safari 26
Simon Fraser (smfr)
Comment 3 2025-09-11 10:17:19 PDT
Thank you for the nice test case, I can reproduce.
Radar WebKit Bug Importer
Comment 4 2025-09-11 10:17:29 PDT
<rdar://problem/160385933>
Matt Woodrow
Comment 5 2025-09-25 00:44:08 PDT
Pull request: https://github.com/WebKit/WebKit/pull/51305
EWS
Comment 6 2025-09-25 18:23:56 PDT
Committed 300544@main (8a1585ea9d5f): <https://commits.webkit.org/300544@main> Reviewed commits have been landed. Closing PR #51305 and removing active labels.
EWS
Comment 7 2025-09-30 22:55:29 PDT
Committed 297297.494@safari-7622-branch (595c5cbed739): <https://commits.webkit.org/297297.494@safari-7622-branch> Reviewed commits have been landed. Closing PR #3736 and removing active labels.
WebKit Commit Bot
Comment 8 2025-10-20 16:10:40 PDT
Re-opened since this is blocked by bug 301145
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