https://bugs.webkit.org/show_bug.cgi?id=220761
<rdar://problem/69075263>
Reviewed by Antti Koivisto.
Source/WebCore:
When a position:absolute element is inside nested overflow scroll, and its containing block is the outer
scroller, then we failed to make a positioning scrolling tree node for it, so it would fail
to track during async scrolling.
The bug was that RenderLayerCompositor::layerScrollBehahaviorRelativeToCompositedAncestor() failed
to deal with nested scrollers. The correct question to ask when determining if we need a "Moves" node
is "is there an overflow scroll layer between this layer and its composited ancestor". Previously,
we would just find the enclosing scroller (with the same scrolling scope) and assume we didn't need
a node.
We can also simplify the "Stationary" code path to just ask about scrolling scopes.
Tests: scrollingcoordinator/ios/absolute-in-nested-overflow-scroll-intermediate-stacking-2.html
scrollingcoordinator/ios/absolute-in-nested-overflow-scroll-intermediate-stacking.html
scrollingcoordinator/ios/absolute-in-nested-overflow-scroll.html
scrollingcoordinator/scrolling-tree/absolute-in-nested-overflow-scroll.html
* rendering/RenderLayerCompositor.cpp:
(WebCore::RenderLayerCompositor::layerScrollBehahaviorRelativeToCompositedAncestor):
(WebCore::isScrolledByOverflowScrollLayer): Deleted.
(WebCore::enclosingCompositedScrollingLayer): Deleted.
LayoutTests:
Add a scrolling tree dump test, and three iOS interactive tests, since testing scrolling-tree-only
behaviors is easier on iOS than macOS. absolute-in-nested-overflow-scroll.html is the basic test.
The two "stacking" variants have an opacity layer below and above the inner scroller to test some
more layer configurations.
* platform/ios-wk2/scrollingcoordinator/scrolling-tree/absolute-in-nested-overflow-scroll-expected.txt: Added.
* scrollingcoordinator/ios/absolute-in-nested-overflow-scroll-expected.html: Added.
* scrollingcoordinator/ios/absolute-in-nested-overflow-scroll-intermediate-stacking-2-expected.html: Added.
* scrollingcoordinator/ios/absolute-in-nested-overflow-scroll-intermediate-stacking-2.html: Added.
* scrollingcoordinator/ios/absolute-in-nested-overflow-scroll-intermediate-stacking-expected.html: Added.
* scrollingcoordinator/ios/absolute-in-nested-overflow-scroll-intermediate-stacking.html: Added.
* scrollingcoordinator/ios/absolute-in-nested-overflow-scroll.html: Added.
* scrollingcoordinator/scrolling-tree/absolute-in-nested-overflow-scroll-expected.txt: Added.
* scrollingcoordinator/scrolling-tree/absolute-in-nested-overflow-scroll.html: Added.
Canonical link: https://commits.webkit.org/233177@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@271651 268f45cc-cd09-0410-ab3c-d52691b4dbfc
a20d0f7496