[webkit-changes] [WebKit/WebKit] b72f84: REGRESSION (279847 at main): Expanding threaded email...

[Simon Fraser]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: b72f845e52d9b27dc8a6cd67aed3215f59f56031
      https://github.com/WebKit/WebKit/commit/b72f845e52d9b27dc8a6cd67aed3215f59f56031
  Author: Simon Fraser <simon.fraser at apple.com>
  Date:   2024-08-08 (Thu, 08 Aug 2024)

  Changed paths:
    A LayoutTests/fast/repaint/simplified-repaint-with-overflow-expected.txt
    A LayoutTests/fast/repaint/simplified-repaint-with-overflow.html
    M Source/WebCore/rendering/RenderLayer.cpp

  Log Message:
  -----------
  REGRESSION (279847 at main): Expanding threaded emails in Fastmail web UI results in missing content, repaint artifacts, broken rendering
https://bugs.webkit.org/show_bug.cgi?id=277782
rdar://133344580

Reviewed by Tim Horton.

The optimization added in 279847 at main caused us to skip repaints on a layer which moved, when the movement is triggered by
layout on an ancestor layer. This caused repaint bugs on Google Sheets when dragging rows, and Fastmail when collapsing
rows.

Fix by undoing the "simplified repaint" optimization on the descendant layers of a layer with overflow, by removing the check for
the layer also having a transform.

* LayoutTests/fast/repaint/simplified-repaint-with-overflow-expected.txt: Added.
* LayoutTests/fast/repaint/simplified-repaint-with-overflow.html: Added.
* Source/WebCore/rendering/RenderLayer.cpp:
(WebCore::RenderLayer::recursiveUpdateLayerPositions):

Canonical link: https://commits.webkit.org/281993@main



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