Bug 293471

Summary:

Compositing layers clip font glyphs with large ascenders/descenders

Product:

WebKit

Reporter:

Matt Moran <mattm>

Component:

Compositing

Assignee:

Nobody <webkit-unassigned>

Status:

NEW

Severity:

Normal

CC:

simon.fraser, webkit-bug-importer

Priority:

Keywords:

InRadar

Version:

Safari 18

Hardware:

All

OS:

All

See Also:

https://bugs.webkit.org/show_bug.cgi?id=6274

Attachments:

Description	Flags
Test case	none
Font with large ascenders & descenders	none
Screenshot of Safari, clipped S at the bottom	none
Screenshot of Chrome	none
Screenshot of Firefox	none

Matt Moran

Reported 2025-05-22 20:23:25 PDT

Compositing layers clip font glyphs with large ascenders/descenders. Steps to reproduce: 1. Load the provided test case 2. Observe that the first "S" renders correctly 3. Observe that the second "S" (with opacity: 0.5) is clipped at top and bottom 4. Click or highlight the middle paragraph 5. Observe that the bottom of the first "S" disappears Some other styles (e.g. `will-change: transform`) with the custom font causes immediate clipping

Attachments
Test case (347 bytes, text/html) 2025-05-22 20:23 PDT, Matt Moran	no flags	Details
Font with large ascenders & descenders (62.52 KB, font/woff) 2025-05-22 20:24 PDT, Matt Moran	no flags	Details
Screenshot of Safari, clipped S at the bottom (38.34 KB, image/png) 2025-05-22 20:24 PDT, Matt Moran	no flags	Details
Screenshot of Chrome (29.80 KB, image/png) 2025-05-22 20:24 PDT, Matt Moran	no flags	Details
Screenshot of Firefox (38.53 KB, image/png) 2025-05-22 20:25 PDT, Matt Moran	no flags	Details
View All Add attachment proposed patch, testcase, etc.

Matt Moran

Comment 1 2025-05-22 20:23:44 PDT

Created attachment 475346 [details] Test case

Matt Moran

Comment 2 2025-05-22 20:24:07 PDT

Created attachment 475347 [details] Font with large ascenders & descenders

Matt Moran

Comment 3 2025-05-22 20:24:37 PDT

Created attachment 475348 [details] Screenshot of Safari, clipped S at the bottom

Matt Moran

Comment 4 2025-05-22 20:24:57 PDT

Created attachment 475349 [details] Screenshot of Chrome

Matt Moran

Comment 5 2025-05-22 20:25:08 PDT

Created attachment 475350 [details] Screenshot of Firefox

Radar WebKit Bug Importer

Comment 6 2025-05-29 20:24:23 PDT

<rdar://problem/152289503>

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