Bug 265362

Summary: Element flickers when transitioning boxShadow with large spread value
Product: WebKit Reporter: Ethan Wong <bunnnywong>
Component: Layout and RenderingAssignee: Nobody <webkit-unassigned>
Status: RESOLVED MOVED    
Severity: Normal CC: ahmad.saleem792, bfulgham, sabouhallawa, simon.fraser, webkit-bug-importer, zalan
Priority: P2 Keywords: InRadar
Version: Safari 17   
Hardware: Mac (Apple Silicon)   
OS: macOS 14   
Attachments:
Description Flags
a page to reproduce the flickering issue
none
screen recording for the flickering issue none

Description Ethan Wong 2023-11-26 22:15:00 PST
Created attachment 468761 [details]
a page to reproduce the flickering issue

Element flickers when transitioning `box-shadow` with a large spread value, see the attached html file and screen recording.

This issue happens when the element has non-zero `border-radius` and non-integer `margin`s.

It happens only on macOS 14.

Force using using `PathRoundedRect::Strategy::PreferBezier` for `PathCG::addRoundedRect(const FloatRoundedRect&, PathRoundedRect::Strategy)` seems to work around this issue.
Comment 1 Ethan Wong 2023-11-26 22:15:34 PST
Created attachment 468762 [details]
screen recording for the flickering issue
Comment 2 Radar WebKit Bug Importer 2023-11-27 10:35:27 PST
<rdar://problem/118840547>
Comment 3 Simon Fraser (smfr) 2023-11-27 10:36:46 PST
Thanks for the report. This is a bug in a system component below webkit.
Comment 4 Brent Fulgham 2023-12-21 15:07:06 PST
The actual work for this fix was done under <rdar://118793261>.