tree 9360377e357950f6e73d72b3af09a44e4153316e
parent 674d9fbcce25fd2369567eef836b25809ee6b93a
author simon.fraser@apple.com <simon.fraser@apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc> 1571350509 +0000
committer simon.fraser@apple.com <simon.fraser@apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc> 1571350509 +0000

[ Mojave+ ] Layout Test compositing/fixed-with-main-thread-scrolling.html is a flaky timeout
https://bugs.webkit.org/show_bug.cgi?id=198757

Reviewed by Tim Horton.

Source/WebCore:

WheelEventTestMonitor depends on "deferral reasons" getting added and removed, such that there is always
at least one reason active until scrolling quiesces.

WheelEventTestMonitor made the incorrect assumption that every call into ScrollingTreeScrollingNodeDelegateMac::handleWheelEvent()
would result in a scroll change making it to the main thread, so it would defer "ScrollingThreadSyncNeeded" there,
and rely on AsyncScrollingCoordinator::updateScrollPositionAfterAsyncScroll() to remove that deferral reason.
That assumption is wrong, because wheel events may coalesce, or have no impact on scroll position if already scrolled
to the max/min extent (e.g. when rubber banding).

Fix by adding a new "HandlingWheelEvent" deferral reason for the duration that the scrolling thread is processing an wheel event,
and then having ScrollingThreadSyncNeeded just represent the phase where any resulting scroll is being sent to the UI process.
These phases should always overlap.

This required moving isMonitoringWheelEvents() from the root scrolling node to the ScrollingTree.

* page/WheelEventTestMonitor.cpp:
(WebCore::operator<<):
* page/WheelEventTestMonitor.h:
* page/scrolling/AsyncScrollingCoordinator.cpp:
(WebCore::AsyncScrollingCoordinator::updateScrollPositionAfterAsyncScroll):
* page/scrolling/ScrollingTree.cpp:
(WebCore::ScrollingTree::commitTreeState):
* page/scrolling/ScrollingTree.h:
(WebCore::ScrollingTree::isMonitoringWheelEvents const):
* page/scrolling/ScrollingTreeScrollingNode.cpp:
(WebCore::ScrollingTreeScrollingNode::commitStateBeforeChildren):
* page/scrolling/ScrollingTreeScrollingNode.h:
* page/scrolling/ThreadedScrollingTree.cpp:
(WebCore::ThreadedScrollingTree::scrollingTreeNodeDidScroll):
* page/scrolling/mac/ScrollingTreeScrollingNodeDelegateMac.mm:
(WebCore::ScrollingTreeScrollingNodeDelegateMac::handleWheelEvent):
(WebCore::ScrollingTreeScrollingNodeDelegateMac::deferWheelEventTestCompletionForReason const):
(WebCore::ScrollingTreeScrollingNodeDelegateMac::removeWheelEventTestCompletionDeferralForReason const):

LayoutTests:

Remove expectation for compositing/fixed-with-main-thread-scrolling.html.

* platform/mac-wk2/TestExpectations:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@251262 268f45cc-cd09-0410-ab3c-d52691b4dbfc