Bug 299728

Summary:

REGRESSION (Safari 26): Missing paint invalidation of area previously covered by a repositioned element

Product:

WebKit

Reporter:

Jonas Walldén <jonasw>

Component:

Layout and Rendering

Assignee:

alan <zalan>

Status:

RESOLVED FIXED

Severity:

Normal

CC:

bfulgham, simon.fraser, webkit-bug-importer, zalan

Priority:

Keywords:

InRadar

Version:

Safari 26

Hardware:

Mac (Apple Silicon)

OS:

macOS 26

Attachments:

Description	Flags
Test case	none
Screenshot from Safari 26.0.1 on macOS 15.7	none
Test reduction	none
Patch	none
[fast-cq]Patch	none

Jonas Walldén

Reported 2025-09-29 05:01:27 PDT

Created attachment 476890 [details] Test case The attached test case creates a ruler and tracks the mouse to render a measurement value on top of the ruler. When mousing around in the window I see remnants of earlier placements still on screen. This is a regression from before version 26, and I've reproduced it in two different macOS installations: Safari 21622.1.22.11.14 running on macOS 26.0 (25A354), and Safari 20622.1.22.118.4 running on macOS 15.7 (24G222). It's also present in Safari Technology Preview r228. I've noticed three workarounds which are included in the test case as `body.workaround1`, `body.workaround2` and `body.workaround3`. They include switching from fixed to absolute positioning, disabling overflow and not setting a z-index.

Attachments
Test case (2.23 KB, text/html) 2025-09-29 05:01 PDT, Jonas Walldén	no flags	Details
Screenshot from Safari 26.0.1 on macOS 15.7 (16.94 KB, image/jpeg) 2025-09-29 05:02 PDT, Jonas Walldén	no flags	Details
Test reduction (466 bytes, text/html) 2025-10-14 10:27 PDT, alan	no flags	Details
Patch (6.15 KB, patch) 2025-10-14 18:50 PDT, alan	no flags	Details Formatted Diff Diff
[fast-cq]Patch (6.22 KB, patch) 2025-10-15 15:28 PDT, alan	no flags	Details Formatted Diff Diff
Show Obsolete (1) View All Add attachment proposed patch, testcase, etc.

Jonas Walldén

Comment 1 2025-09-29 05:02:36 PDT

Created attachment 476891 [details] Screenshot from Safari 26.0.1 on macOS 15.7

Jonas Walldén

Comment 2 2025-09-29 05:03:22 PDT

*** Bug 299727 has been marked as a duplicate of this bug. ***

Radar WebKit Bug Importer

Comment 3 2025-09-29 08:09:31 PDT

<rdar://problem/161570899>

alan

Comment 4 2025-10-14 10:00:50 PDT

I am able to reproduce this repaint issue all the way back to May of 2024 (279284@main -the oldest build I have locally).

alan

Comment 5 2025-10-14 10:27:46 PDT

Created attachment 477073 [details] Test reduction

alan

Comment 6 2025-10-14 18:50:54 PDT

Created attachment 477080 [details] Patch

alan

Comment 7 2025-10-15 15:28:23 PDT

Created attachment 477093 [details] [fast-cq]Patch

EWS

Comment 8 2025-10-16 05:30:21 PDT

Committed 301625@main (1ea46dc05aa6): <https://commits.webkit.org/301625@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 477093 [details].

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