Title: [286411] trunk/Source/WebCore
- Revision
- 286411
- Author
- simon.fra...@apple.com
- Date
- 2021-12-01 20:58:54 -0800 (Wed, 01 Dec 2021)
Log Message
Scrolling complex websites can stutter: scrolling thread frame can fail to process wheel events
https://bugs.webkit.org/show_bug.cgi?id=233739
rdar://85946176
Reviewed by Tim Horton.
While the scrolling thread is chilling in
ThreadedScrollingTree::waitForRenderingUpdateCompletionOrTimeout(), waiting up to half a
frame to allow the main thread to handle the commit (for scroll synchronization), wheel
events may have been dispatched to the scrolling thread.
If we blow the timeout and commit anyway, we need to make sure we've handled these wheel
events first, so that the current frame can commit some layer movement. We can achieve this
by dispatching the applyLayerPositions(), which will enqueue it behind any waiting wheel
event dispatch from EventDispatcher::internalWheelEvent().
* page/scrolling/ScrollingTree.cpp:
(WebCore::ScrollingTree::applyLayerPositions):
* page/scrolling/ThreadedScrollingTree.cpp:
(WebCore::ThreadedScrollingTree::waitForRenderingUpdateCompletionOrTimeout):
Modified Paths
Diff
Modified: trunk/Source/WebCore/ChangeLog (286410 => 286411)
--- trunk/Source/WebCore/ChangeLog 2021-12-02 04:58:49 UTC (rev 286410)
+++ trunk/Source/WebCore/ChangeLog 2021-12-02 04:58:54 UTC (rev 286411)
@@ -1,5 +1,28 @@
2021-12-01 Simon Fraser <simon.fra...@apple.com>
+ Scrolling complex websites can stutter: scrolling thread frame can fail to process wheel events
+ https://bugs.webkit.org/show_bug.cgi?id=233739
+ rdar://85946176
+
+ Reviewed by Tim Horton.
+
+ While the scrolling thread is chilling in
+ ThreadedScrollingTree::waitForRenderingUpdateCompletionOrTimeout(), waiting up to half a
+ frame to allow the main thread to handle the commit (for scroll synchronization), wheel
+ events may have been dispatched to the scrolling thread.
+
+ If we blow the timeout and commit anyway, we need to make sure we've handled these wheel
+ events first, so that the current frame can commit some layer movement. We can achieve this
+ by dispatching the applyLayerPositions(), which will enqueue it behind any waiting wheel
+ event dispatch from EventDispatcher::internalWheelEvent().
+
+ * page/scrolling/ScrollingTree.cpp:
+ (WebCore::ScrollingTree::applyLayerPositions):
+ * page/scrolling/ThreadedScrollingTree.cpp:
+ (WebCore::ThreadedScrollingTree::waitForRenderingUpdateCompletionOrTimeout):
+
+2021-12-01 Simon Fraser <simon.fra...@apple.com>
+
Scrolling complex websites can stutter: scrolling thread commit can get blocked on scroll synchronization
https://bugs.webkit.org/show_bug.cgi?id=233738
rdar://85880147
Modified: trunk/Source/WebCore/page/scrolling/ScrollingTree.cpp (286410 => 286411)
--- trunk/Source/WebCore/page/scrolling/ScrollingTree.cpp 2021-12-02 04:58:49 UTC (rev 286410)
+++ trunk/Source/WebCore/page/scrolling/ScrollingTree.cpp 2021-12-02 04:58:54 UTC (rev 286411)
@@ -437,7 +437,6 @@
void ScrollingTree::applyLayerPositions()
{
- ASSERT(isMainThread());
Locker locker { m_treeLock };
applyLayerPositionsInternal();
Modified: trunk/Source/WebCore/page/scrolling/ThreadedScrollingTree.cpp (286410 => 286411)
--- trunk/Source/WebCore/page/scrolling/ThreadedScrollingTree.cpp 2021-12-02 04:58:49 UTC (rev 286410)
+++ trunk/Source/WebCore/page/scrolling/ThreadedScrollingTree.cpp 2021-12-02 04:58:54 UTC (rev 286411)
@@ -417,8 +417,12 @@
m_state = SynchronizationState::Desynchronized;
// At this point we know the main thread is taking too long in the rendering update,
// so we give up trying to sync with the main thread and update layers here on the scrolling thread.
- if (canUpdateLayersOnScrollingThread())
- applyLayerPositionsInternal();
+ if (canUpdateLayersOnScrollingThread()) {
+ // Dispatch to allow for the scrolling thread to handle any outstanding wheel events before we commit layers.
+ ScrollingThread::dispatch([protectedThis = Ref { *this }]() {
+ protectedThis->applyLayerPositions();
+ });
+ }
tracePoint(ScrollingThreadRenderUpdateSyncEnd, 1);
} else
tracePoint(ScrollingThreadRenderUpdateSyncEnd);
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