Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 46572d8428cba7c77d2ea1182c7a1c9502b12ab8
https://github.com/WebKit/WebKit/commit/46572d8428cba7c77d2ea1182c7a1c9502b12ab8
Author: Simon Fraser <simon.fra...@apple.com>
Date: 2023-05-02 (Tue, 02 May 2023)
Changed paths:
M Source/WebCore/page/scrolling/ScrollingStateTree.cpp
M Source/WebCore/page/scrolling/ScrollingStateTree.h
M Source/WebCore/rendering/RenderLayerCompositor.cpp
M Source/WebCore/rendering/RenderLayerCompositor.h
Log Message:
-----------
Assert that the scrolling tree is valid, and fix issues with negative z-index
layers
https://bugs.webkit.org/show_bug.cgi?id=256193
rdar://108769471
Reviewed by Tim Horton.
To make it easier to detect invalid scrolling trees which can result in
MESSAGE_CHECKs
(rdar://108204370) add code to check the validity of the scrolling tree in the
web process, and
assert when not valid. This code checks that nodes that have cross-references
to other scrolling
tree nodes actually point to live nodes.
This detected a case where we have incorrect behavior (tested by
scrollingcoordinator/scrolling-tree/scroller-with-negative-z-child.html and two
similar tests); when
an overflow:scroll has composited descendant which is not a paint-order child,
the child gets an
"ancestor clipping stack" which points to
ScrollingStateOverflowScrollProxyNodes, which reference
the actual overflow scrolling node. However, if the child has negative z-index,
we encounter the
child before the overflow scroller so fail to find its scrolling tree node.
Fix this by keeping track of RenderLayers with unresolved scrolling tree
references in
m_layersWithUnresolvedRelations, and updating them at the end of the "update
backing and hierarchy"
compositing phase.
* Source/WebCore/page/scrolling/ScrollingStateTree.cpp:
(WebCore::ScrollingStateTree::commit):
(WebCore::ScrollingStateTree::traverse const):
(WebCore::ScrollingStateTree::isValid const):
* Source/WebCore/page/scrolling/ScrollingStateTree.h:
* Source/WebCore/rendering/RenderLayerCompositor.cpp:
(WebCore::RenderLayerCompositor::updateCompositingLayers):
(WebCore::RenderLayerCompositor::setupScrollProxyRelatedOverflowScrollingNode):
(WebCore::RenderLayerCompositor::updateScrollingNodeForScrollingProxyRole):
(WebCore::RenderLayerCompositor::resolveScrollingTreeRelationships):
* Source/WebCore/rendering/RenderLayerCompositor.h:
Canonical link: https://commits.webkit.org/263620@main
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