Bug 282215

Summary: WebCore's main thread scroll position is poorly synchronized with the UI-process scroll position
Product: WebKit Reporter: Simon Fraser (smfr) <simon.fraser>
Component: ScrollingAssignee: Simon Fraser (smfr) <simon.fraser>
Status: RESOLVED FIXED    
Severity: Normal CC: simon.fraser, webkit-bug-importer
Priority: P2 Keywords: InRadar
Version: WebKit Nightly Build   
Hardware: Unspecified   
OS: Unspecified   
Attachments:
Description Flags
JS-driven fixed testcase none

Simon Fraser (smfr)
Reported 2024-10-28 17:46:50 PDT
Som page effects rely on the main thread scroll position in WebCore code, for example painting of `background-attachment:fixed` content on a non-root element, and JS-driven fake fixed and sticky elements. With UI-side compositing, the synchronization between the UI-process and web process scroll positions is worse than it should be.
Attachments
JS-driven fixed testcase (2.98 KB, text/html)
2024-10-28 17:47 PDT, Simon Fraser (smfr) 		no flags
Details
View All Add attachment proposed patch, testcase, etc.
Simon Fraser (smfr)
Comment 1 2024-10-28 17:47:29 PDT
Created attachment 473068 [details] JS-driven fixed testcase This JS-driven fake-fixed testcaase shows more stutters than it should.
Radar WebKit Bug Importer
Comment 2 2024-10-28 17:48:18 PDT
<rdar://problem/138804403>
Simon Fraser (smfr)
Comment 3 2024-10-28 18:15:09 PDT
Pull request: https://github.com/WebKit/WebKit/pull/35839
EWS
Comment 4 2024-11-04 09:42:11 PST
Committed 286095@main (3056a40d3e23): <https://commits.webkit.org/286095@main> Reviewed commits have been landed. Closing PR #35839 and removing active labels.
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