RESOLVED FIXED307966
(Regression: Safari 26.x) Underline animation leaves traces (repaint issue) 
https://bugs.webkit.org/show_bug.cgi?id=307966
Summary (Regression: Safari 26.x) Underline animation leaves traces (repaint issue)
Ahmad Saleem
Reported 2026-02-15 20:11:08 PST
Hi Team, While going through article about macOS Tahoe window resize issue on blog, I noticed the bug and now filling here: **** Steps to Reproduce *** 1. Go to https://noheger.at/blog/about/ 2. Hover over `Launch Bar` or `Little Snitch` 3. It animates underline but some time leaves traces *** Actual Results *** It leaves traces, upon resize, it goes away - so repaint issue. *** Expected Result *** It should not leave traces. *** Regression Info *** It does not reproduces on Safari 26.3 but does on Safari Technology Preview 237. *** Other browsers *** Does not reproduce on Chrome Canary 147. Just raising, so we can fix it. Thanks!
Attachments
STP237 - Video - Issue (7.78 MB, video/quicktime)
2026-02-15 20:12 PST, Ahmad Saleem 		no flags
Details
Test reduction (172.50 KB, text/html)
2026-02-16 10:49 PST, alan 		no flags
Details
[fast-cq]Patch (3.60 KB, patch)
2026-02-16 18:20 PST, alan 		no flags
DetailsFormatted DiffDiff
View All Add attachment proposed patch, testcase, etc.
Radar WebKit Bug Importer
Comment 1 2026-02-15 20:11:15 PST
<rdar://problem/170448325>
Ahmad Saleem
Comment 2 2026-02-15 20:12:33 PST
Created attachment 478368 [details] STP237 - Video - Issue
Ahmad Saleem
Comment 3 2026-02-15 20:13:47 PST
Good news - it is already fixed on WebKit ToT (Minibrowser - 307630@main).
alan
Comment 4 2026-02-16 10:49:55 PST
Created attachment 478377 [details] Test reduction This bug will come back with [subpixel inline layout]. It seems like we under-invalidate the area to repaint when content is on fractional pixel position.
alan
Comment 5 2026-02-16 18:20:03 PST
Created attachment 478380 [details] [fast-cq]Patch
EWS
Comment 6 2026-02-17 05:34:08 PST
Committed 307701@main (a349723e4b51): <https://commits.webkit.org/307701@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 478380 [details].
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