Bug 221322

Summary: WebKit box-shadow rendering artifacts and imprecise calculation when relative units are used!
Product: WebKit Reporter: Tobias Høegh <tobias>
Component: CSSAssignee: Nobody <webkit-unassigned>
Status: NEW    
Severity: Major CC: ahmad.saleem792, koivisto, simon.fraser, smoley, webkit-bug-importer, zalan
Priority: P2 Keywords: InRadar
Version: Safari 14   
Hardware: All   
OS: All   
URL: https://codepen.io/tujoworker/pen/ExNVjZm
Attachments:
Description Flags
All visible lines should have the same thickness none

Tobias Høegh
Reported 2021-02-03 02:05:41 PST
Created attachment 419115 [details] All visible lines should have the same thickness WebKit box-shadow rendering has artifacts and imprecise calculation when relative units are used. Take a look at the Code-Pen example: https://codepen.io/tujoworker/pen/ExNVjZm These two test cases do share the same box-shadow CSS, but has clearly a difference on how Safari/WebKit renders box-shadow when a different font-size is inherited. No CSS then the browser defaults style should influence the test cases. To make it more visible, we use 0.0625em (1px). But the imprecise calculation applies also to larger box-shadow sizes. None of other tested browser does have that (Firefox/Chromium). More info in the PEN, shared above.
Attachments
All visible lines should have the same thickness (5.65 KB, image/png)
2021-02-03 02:05 PST, Tobias Høegh 		no flags
Details
View All Add attachment proposed patch, testcase, etc.
Simon Fraser (smfr)
Comment 1 2021-02-03 19:24:25 PST
Pixel snapping?
Radar WebKit Bug Importer
Comment 2 2021-02-09 16:38:39 PST
<rdar://problem/74165770>
Ahmad Saleem
Comment 3 2023-02-20 15:16:32 PST
I am able to reproduce this bug in Safari 16.3, STP163 and WebKit ToT (260566@main). Just wanted to update latest testing results. Thanks!
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