Attachment 360651 Details for Bug 172917 – Patch

[patch] Patch

bug-172917-20190130170638.patch (text/plain), 61.53 KB, created by Simon Fraser (smfr) on 2019-01-30 17:06:39 PST

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Creator: Simon Fraser (smfr)

Created: 2019-01-30 17:06:39 PST

Size: 61.53 KB

patch

obsolete

>Subversion Revision: 240713
>diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
>index fa6bd328897655d2c8ddeebebe22e7986e4112ce..c068d6749a8aaa3578de9eeb4c0e92f1ec223c2b 100644
>--- a/Source/WebCore/ChangeLog
>+++ b/Source/WebCore/ChangeLog
>@@ -1,3 +1,78 @@
>+2019-01-30  Simon Fraser  <simon.fraser@apple.com>
>+
>+        [Mac] Implement basic hit testing in the scrolling tree
>+        https://bugs.webkit.org/show_bug.cgi?id=172917
>+        <rdar://problem/34215516>
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        First steps to getting hit testing of scrolling nodes in the scrolling tree. Based on patch
>+        by FrÃ©dÃ©ric Wang.
>+
>+        First we pipe the "async scrolling enabled" setting through to the ScrollingTree via
>+        the root node (like the other settings; weird, but that's how it's done). For now,
>+        we hit test in the scrolling tree if either async overflow or frame scrolling are enabled
>+        (it's hard to deal with one without the other).
>+
>+        Nodes in the scrolling tree implement scrollingNodeForPoint() to implement hit testing.
>+        Two helper functions exist to simplify coordinate conversion: parentToLocalPoint()
>+        and localToContentsPoint(). Child nodes are hit-testing in reverse order to find nodes
>+        hightest in Z first. Only scrolling nodes are returned (not sure if we'll ever need
>+        to hit-test non-scrolling nodes). Nodes use parentRelativeScrollableRect and scroll positions
>+        to do these point mappings.
>+        
>+        handleWheelEvent() is changed to return a ScrollingEventResult.
>+        
>+        No tests yet; for ease of testing, I'd like to add an Internals API to hit-test the
>+        scrolling tree, rather than doing eventSender stuff everywhere.
>+
>+        * page/scrolling/AsyncScrollingCoordinator.cpp:
>+        (WebCore::AsyncScrollingCoordinator::frameViewLayoutUpdated):
>+        (WebCore::AsyncScrollingCoordinator::asyncFrameOrOverflowScrollingEnabled const):
>+        * page/scrolling/AsyncScrollingCoordinator.h:
>+        * page/scrolling/ScrollingStateFrameScrollingNode.cpp:
>+        (WebCore::ScrollingStateFrameScrollingNode::ScrollingStateFrameScrollingNode):
>+        (WebCore::ScrollingStateFrameScrollingNode::setAllPropertiesChanged):
>+        (WebCore::ScrollingStateFrameScrollingNode::setAsyncFrameOrOverflowScrollingEnabled):
>+        * page/scrolling/ScrollingStateFrameScrollingNode.h:
>+        * page/scrolling/ScrollingTree.cpp:
>+        (WebCore::ScrollingTree::shouldHandleWheelEventSynchronously):
>+        (WebCore::ScrollingTree::handleWheelEvent):
>+        (WebCore::ScrollingTree::commitTreeState):
>+        (WebCore::ScrollingTree::setAsyncFrameOrOverflowScrollingEnabled):
>+        * page/scrolling/ScrollingTree.h:
>+        (WebCore::ScrollingTree::asyncFrameOrOverflowScrollingEnabled const):
>+        * page/scrolling/ScrollingTreeFrameHostingNode.cpp:
>+        (WebCore::ScrollingTreeFrameHostingNode::parentToLocalPoint const):
>+        * page/scrolling/ScrollingTreeFrameHostingNode.h:
>+        * page/scrolling/ScrollingTreeFrameScrollingNode.cpp:
>+        (WebCore::ScrollingTreeFrameScrollingNode::parentToLocalPoint const):
>+        (WebCore::ScrollingTreeFrameScrollingNode::localToContentsPoint const):
>+        * page/scrolling/ScrollingTreeFrameScrollingNode.h:
>+        * page/scrolling/ScrollingTreeNode.cpp:
>+        (WebCore::ScrollingTreeNode::scrollingNodeForPoint const):
>+        * page/scrolling/ScrollingTreeNode.h:
>+        (WebCore::ScrollingTreeNode::children const):
>+        (WebCore::ScrollingTreeNode::parentToLocalPoint const):
>+        (WebCore::ScrollingTreeNode::localToContentsPoint const):
>+        * page/scrolling/ScrollingTreeScrollingNode.cpp:
>+        (WebCore::ScrollingTreeScrollingNode::scrollLimitReached const):
>+        (WebCore::ScrollingTreeScrollingNode::parentToLocalPoint const):
>+        (WebCore::ScrollingTreeScrollingNode::localToContentsPoint const):
>+        (WebCore::ScrollingTreeScrollingNode::scrollingNodeForPoint const):
>+        * page/scrolling/ScrollingTreeScrollingNode.h:
>+        * page/scrolling/ThreadedScrollingTree.cpp:
>+        (WebCore::ThreadedScrollingTree::handleWheelEvent):
>+        * page/scrolling/ThreadedScrollingTree.h:
>+        * page/scrolling/ios/ScrollingTreeFrameScrollingNodeIOS.h:
>+        * page/scrolling/ios/ScrollingTreeFrameScrollingNodeIOS.mm:
>+        (WebCore::ScrollingTreeFrameScrollingNodeIOS::handleWheelEvent):
>+        * page/scrolling/ios/ScrollingTreeIOS.h:
>+        * page/scrolling/mac/ScrollingTreeFrameScrollingNodeMac.h:
>+        * page/scrolling/mac/ScrollingTreeFrameScrollingNodeMac.mm:
>+        (WebCore::ScrollingTreeFrameScrollingNodeMac::handleWheelEvent):
>+        * page/scrolling/mac/ScrollingTreeOverflowScrollingNodeMac.h:
>+
> 2019-01-30  Simon Fraser  <simon.fraser@apple.com>
> 
>         Add some basic geometry information to the scrolling tree
>diff --git a/Source/WebKit/ChangeLog b/Source/WebKit/ChangeLog
>index 11d679ebbcab423c02e3f231904033eabe96c9a0..43e98540e3ea6c7d49731013246bf81c4e234438 100644
>--- a/Source/WebKit/ChangeLog
>+++ b/Source/WebKit/ChangeLog
>@@ -1,3 +1,25 @@
>+2019-01-30  Simon Fraser  <simon.fraser@apple.com>
>+
>+        [Mac] Implement basic hit testing in the scrolling tree
>+        https://bugs.webkit.org/show_bug.cgi?id=172917
>+        <rdar://problem/34215516>
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        Changed return types, "using namespace WebCore" in ScrollingTreeFrameScrollingNodeRemoteMac.cpp.
>+
>+        * Shared/RemoteLayerTree/RemoteScrollingCoordinatorTransaction.cpp:
>+        (ArgumentCoder<ScrollingStateFrameScrollingNode>::encode):
>+        * UIProcess/RemoteLayerTree/ios/ScrollingTreeOverflowScrollingNodeIOS.h:
>+        * UIProcess/RemoteLayerTree/mac/ScrollerPairMac.h:
>+        * UIProcess/RemoteLayerTree/mac/ScrollerPairMac.mm:
>+        (WebKit::ScrollerPairMac::handleWheelEvent):
>+        (WebKit::ScrollerPairMac::handleMouseEvent):
>+        * UIProcess/RemoteLayerTree/mac/ScrollingTreeFrameScrollingNodeRemoteMac.cpp:
>+        (WebKit::ScrollingTreeFrameScrollingNodeRemoteMac::handleWheelEvent):
>+        (WebKit::ScrollingTreeFrameScrollingNodeRemoteMac::handleMouseEvent):
>+        * UIProcess/RemoteLayerTree/mac/ScrollingTreeFrameScrollingNodeRemoteMac.h:
>+
> 2019-01-30  Simon Fraser  <simon.fraser@apple.com>
> 
>         Add some basic geometry information to the scrolling tree
>diff --git a/Source/WebCore/page/FrameView.cpp b/Source/WebCore/page/FrameView.cpp
>index b6bbaf3a7590b76605e3121f158330429b9a5789..d5c8897fe12ce6a4c81c75944870548fac1e9e83 100644
>--- a/Source/WebCore/page/FrameView.cpp
>+++ b/Source/WebCore/page/FrameView.cpp
>@@ -5011,7 +5011,7 @@ bool FrameView::wheelEvent(const PlatformWheelEvent& wheelEvent)
>     if (Page* page = frame().page()) {
>         if (ScrollingCoordinator* scrollingCoordinator = page->scrollingCoordinator()) {
>             if (scrollingCoordinator->coordinatesScrollingForFrameView(*this))
>-                return scrollingCoordinator->handleWheelEvent(*this, wheelEvent);
>+                return scrollingCoordinator->handleWheelEvent(*this, wheelEvent) != ScrollingEventResult::DidNotHandleEvent;
>         }
>     }
> #endif
>diff --git a/Source/WebCore/page/scrolling/AsyncScrollingCoordinator.cpp b/Source/WebCore/page/scrolling/AsyncScrollingCoordinator.cpp
>index f7d809da1c4f19129582ea14fae9a87076b00bbd..ee127d11cd4d8a91352319f6d1b3d63d872ebcc4 100644
>--- a/Source/WebCore/page/scrolling/AsyncScrollingCoordinator.cpp
>+++ b/Source/WebCore/page/scrolling/AsyncScrollingCoordinator.cpp
>@@ -130,30 +130,34 @@ void AsyncScrollingCoordinator::frameViewLayoutUpdated(FrameView& frameView)
>     if (!coordinatesScrollingForFrameView(frameView))
>         return;
> 
>-    auto* node = downcast<ScrollingStateFrameScrollingNode>(m_scrollingStateTree->stateNodeForID(frameView.scrollLayerID()));
>-    if (!node)
>+    auto* node = m_scrollingStateTree->stateNodeForID(frameView.scrollLayerID());
>+    if (!node || !is<ScrollingStateFrameScrollingNode>(*node))
>         return;
> 
>+    auto& frameScrollingNode = downcast<ScrollingStateFrameScrollingNode>(*node);
>+
>     auto* verticalScrollbar = frameView.verticalScrollbar();
>     auto* horizontalScrollbar = frameView.horizontalScrollbar();
>-    node->setScrollerImpsFromScrollbars(verticalScrollbar, horizontalScrollbar);
>-
>-    node->setFrameScaleFactor(frameView.frame().frameScaleFactor());
>-    node->setHeaderHeight(frameView.headerHeight());
>-    node->setFooterHeight(frameView.footerHeight());
>-    node->setTopContentInset(frameView.topContentInset());
>-
>-    node->setVisualViewportEnabled(visualViewportEnabled());
>-    node->setLayoutViewport(frameView.layoutViewportRect());
>-    node->setMinLayoutViewportOrigin(frameView.minStableLayoutViewportOrigin());
>-    node->setMaxLayoutViewportOrigin(frameView.maxStableLayoutViewportOrigin());
>-
>-    node->setScrollOrigin(frameView.scrollOrigin());
>-    node->setScrollableAreaSize(frameView.visibleContentRect().size());
>-    node->setTotalContentsSize(frameView.totalContentsSize());
>-    node->setReachableContentsSize(frameView.totalContentsSize());
>-    node->setFixedElementsLayoutRelativeToFrame(frameView.fixedElementsLayoutRelativeToFrame());
>-    node->setScrollBehaviorForFixedElements(frameView.scrollBehaviorForFixedElements());
>+    frameScrollingNode.setScrollerImpsFromScrollbars(verticalScrollbar, horizontalScrollbar);
>+
>+    frameScrollingNode.setFrameScaleFactor(frameView.frame().frameScaleFactor());
>+    frameScrollingNode.setHeaderHeight(frameView.headerHeight());
>+    frameScrollingNode.setFooterHeight(frameView.footerHeight());
>+    frameScrollingNode.setTopContentInset(frameView.topContentInset());
>+
>+    frameScrollingNode.setVisualViewportEnabled(visualViewportEnabled());
>+    frameScrollingNode.setLayoutViewport(frameView.layoutViewportRect());
>+    frameScrollingNode.setAsyncFrameOrOverflowScrollingEnabled(asyncFrameOrOverflowScrollingEnabled());
>+
>+    frameScrollingNode.setMinLayoutViewportOrigin(frameView.minStableLayoutViewportOrigin());
>+    frameScrollingNode.setMaxLayoutViewportOrigin(frameView.maxStableLayoutViewportOrigin());
>+
>+    frameScrollingNode.setScrollOrigin(frameView.scrollOrigin());
>+    frameScrollingNode.setScrollableAreaSize(frameView.visibleContentRect().size());
>+    frameScrollingNode.setTotalContentsSize(frameView.totalContentsSize());
>+    frameScrollingNode.setReachableContentsSize(frameView.totalContentsSize());
>+    frameScrollingNode.setFixedElementsLayoutRelativeToFrame(frameView.fixedElementsLayoutRelativeToFrame());
>+    frameScrollingNode.setScrollBehaviorForFixedElements(frameView.scrollBehaviorForFixedElements());
> 
> #if ENABLE(CSS_SCROLL_SNAP)
>     frameView.updateSnapOffsets();
>@@ -164,7 +168,7 @@ void AsyncScrollingCoordinator::frameViewLayoutUpdated(FrameView& frameView)
>     auto* page = frameView.frame().page();
>     if (page && page->expectsWheelEventTriggers()) {
>         LOG(WheelEventTestTriggers, "    AsyncScrollingCoordinator::frameViewLayoutUpdated: Expects wheel event test trigger=%d", page->expectsWheelEventTriggers());
>-        node->setExpectsWheelEventTestTrigger(page->expectsWheelEventTriggers());
>+        frameScrollingNode.setExpectsWheelEventTestTrigger(page->expectsWheelEventTriggers());
>     }
> #endif
> 
>@@ -177,7 +181,7 @@ void AsyncScrollingCoordinator::frameViewLayoutUpdated(FrameView& frameView)
>     scrollParameters.verticalScrollbarMode = frameView.verticalScrollbarMode();
>     scrollParameters.useDarkAppearanceForScrollbars = frameView.useDarkAppearanceForScrollbars();
> 
>-    node->setScrollableAreaParameters(scrollParameters);
>+    frameScrollingNode.setScrollableAreaParameters(scrollParameters);
> }
> 
> void AsyncScrollingCoordinator::updateExpectsWheelEventTestTriggerWithFrameView(const FrameView& frameView)
>@@ -679,6 +683,12 @@ bool AsyncScrollingCoordinator::visualViewportEnabled() const
>     return m_page->mainFrame().settings().visualViewportEnabled();
> }
> 
>+bool AsyncScrollingCoordinator::asyncFrameOrOverflowScrollingEnabled() const
>+{
>+    auto& settings = m_page->mainFrame().settings();
>+    return settings.asyncFrameScrollingEnabled() || settings.asyncOverflowScrollingEnabled();
>+}
>+
> String AsyncScrollingCoordinator::scrollingStateTreeAsText(ScrollingStateTreeAsTextBehavior behavior) const
> {
>     if (m_scrollingStateTree->rootStateNode()) {
>diff --git a/Source/WebCore/page/scrolling/AsyncScrollingCoordinator.h b/Source/WebCore/page/scrolling/AsyncScrollingCoordinator.h
>index cc23da8f0be8926a1443ae15394042cf27abed34..345a374b4a6ca60fe3cc857be0b5e0713ccaa1bc 100644
>--- a/Source/WebCore/page/scrolling/AsyncScrollingCoordinator.h
>+++ b/Source/WebCore/page/scrolling/AsyncScrollingCoordinator.h
>@@ -90,6 +90,7 @@ private:
>     bool hasVisibleSlowRepaintViewportConstrainedObjects(const FrameView&) const override { return false; }
>     
>     bool visualViewportEnabled() const;
>+    bool asyncFrameOrOverflowScrollingEnabled() const;
> 
>     WEBCORE_EXPORT void frameViewLayoutUpdated(FrameView&) override;
>     WEBCORE_EXPORT void frameViewRootLayerDidChange(FrameView&) override;
>diff --git a/Source/WebCore/page/scrolling/ScrollingCoordinator.h b/Source/WebCore/page/scrolling/ScrollingCoordinator.h
>index 53322f666160c12f45acaadc90408fe03c5fe8e2..02cbb27391935a3614001183c01d167c6926ead8 100644
>--- a/Source/WebCore/page/scrolling/ScrollingCoordinator.h
>+++ b/Source/WebCore/page/scrolling/ScrollingCoordinator.h
>@@ -111,7 +111,7 @@ public:
>     // These virtual functions are currently unique to the threaded scrolling architecture. 
>     virtual void commitTreeStateIfNeeded() { }
>     virtual bool requestScrollPositionUpdate(FrameView&, const IntPoint&) { return false; }
>-    virtual bool handleWheelEvent(FrameView&, const PlatformWheelEvent&) { return true; }
>+    virtual ScrollingEventResult handleWheelEvent(FrameView&, const PlatformWheelEvent&) { return ScrollingEventResult::DidNotHandleEvent; }
> 
>     // Create an unparented node.
>     virtual ScrollingNodeID createNode(ScrollingNodeType, ScrollingNodeID newNodeID) { return newNodeID; }
>diff --git a/Source/WebCore/page/scrolling/ScrollingCoordinatorTypes.h b/Source/WebCore/page/scrolling/ScrollingCoordinatorTypes.h
>index 137ebd2ffcc9c8fe400c0cec67d6016967914b15..5d6e2009b0aa95dfdf0366b9c1369ae0655f5b87 100644
>--- a/Source/WebCore/page/scrolling/ScrollingCoordinatorTypes.h
>+++ b/Source/WebCore/page/scrolling/ScrollingCoordinatorTypes.h
>@@ -80,6 +80,12 @@ struct ScrollableAreaParameters {
>     }
> };
> 
>+enum class ScrollingEventResult {
>+    DidNotHandleEvent,
>+    DidHandleEvent,
>+    SendToMainThread
>+};
>+
> enum class ViewportRectStability {
>     Stable,
>     Unstable,
>diff --git a/Source/WebCore/page/scrolling/ScrollingStateFrameScrollingNode.cpp b/Source/WebCore/page/scrolling/ScrollingStateFrameScrollingNode.cpp
>index 76b1d0f56c48c9024f7992ef2f14f079ccddf36c..66cd7ecef88bff7ee19dbe7c5351e06619ff9668 100644
>--- a/Source/WebCore/page/scrolling/ScrollingStateFrameScrollingNode.cpp
>+++ b/Source/WebCore/page/scrolling/ScrollingStateFrameScrollingNode.cpp
>@@ -64,6 +64,7 @@ ScrollingStateFrameScrollingNode::ScrollingStateFrameScrollingNode(const Scrolli
>     , m_requestedScrollPositionRepresentsProgrammaticScroll(stateNode.requestedScrollPositionRepresentsProgrammaticScroll())
>     , m_fixedElementsLayoutRelativeToFrame(stateNode.fixedElementsLayoutRelativeToFrame())
>     , m_visualViewportEnabled(stateNode.visualViewportEnabled())
>+    , m_asyncFrameOrOverflowScrollingEnabled(stateNode.asyncFrameOrOverflowScrollingEnabled())
> {
>     if (hasChangedProperty(CounterScrollingLayer))
>         setCounterScrollingLayer(stateNode.counterScrollingLayer().toRepresentation(adoptiveTree.preferredLayerRepresentation()));
>@@ -114,6 +115,7 @@ void ScrollingStateFrameScrollingNode::setAllPropertiesChanged()
>     setPropertyChangedBit(TopContentInset);
>     setPropertyChangedBit(FixedElementsLayoutRelativeToFrame);
>     setPropertyChangedBit(VisualViewportEnabled);
>+    setPropertyChangedBit(AsyncFrameOrOverflowScrollingEnabled);
>     setPropertyChangedBit(LayoutViewport);
>     setPropertyChangedBit(MinLayoutViewportOrigin);
>     setPropertyChangedBit(MaxLayoutViewportOrigin);
>@@ -294,6 +296,15 @@ void ScrollingStateFrameScrollingNode::setVisualViewportEnabled(bool visualViewp
>     setPropertyChanged(VisualViewportEnabled);
> }
> 
>+void ScrollingStateFrameScrollingNode::setAsyncFrameOrOverflowScrollingEnabled(bool enabled)
>+{
>+    if (enabled == m_asyncFrameOrOverflowScrollingEnabled)
>+        return;
>+    
>+    m_asyncFrameOrOverflowScrollingEnabled = enabled;
>+    setPropertyChanged(AsyncFrameOrOverflowScrollingEnabled);
>+}
>+
> #if !PLATFORM(MAC)
> void ScrollingStateFrameScrollingNode::setScrollerImpsFromScrollbars(Scrollbar*, Scrollbar*)
> {
>diff --git a/Source/WebCore/page/scrolling/ScrollingStateFrameScrollingNode.h b/Source/WebCore/page/scrolling/ScrollingStateFrameScrollingNode.h
>index 7b5970a5443efdfecb0ec35cad0e33d905868edb..f5d8646ef407707684be7a4dbcbe95e7bf4151d8 100644
>--- a/Source/WebCore/page/scrolling/ScrollingStateFrameScrollingNode.h
>+++ b/Source/WebCore/page/scrolling/ScrollingStateFrameScrollingNode.h
>@@ -64,6 +64,7 @@ public:
>         TopContentInset,
>         FixedElementsLayoutRelativeToFrame,
>         VisualViewportEnabled,
>+        AsyncFrameOrOverflowScrollingEnabled,
>         LayoutViewport,
>         MinLayoutViewportOrigin,
>         MaxLayoutViewportOrigin,
>@@ -127,12 +128,16 @@ public:
>     const LayerRepresentation& horizontalScrollbarLayer() const { return m_horizontalScrollbarLayer; }
>     WEBCORE_EXPORT void setHorizontalScrollbarLayer(const LayerRepresentation&);
> 
>+    // These are more like Settings, and should probably move to the Scrolling{State}Tree itself.
>     bool fixedElementsLayoutRelativeToFrame() const { return m_fixedElementsLayoutRelativeToFrame; }
>     WEBCORE_EXPORT void setFixedElementsLayoutRelativeToFrame(bool);
> 
>     bool visualViewportEnabled() const { return m_visualViewportEnabled; };
>     WEBCORE_EXPORT void setVisualViewportEnabled(bool);
> 
>+    bool asyncFrameOrOverflowScrollingEnabled() const { return m_asyncFrameOrOverflowScrollingEnabled; }
>+    void setAsyncFrameOrOverflowScrollingEnabled(bool);
>+
> #if PLATFORM(MAC)
>     NSScrollerImp *verticalScrollerImp() const { return m_verticalScrollerImp.get(); }
>     NSScrollerImp *horizontalScrollerImp() const { return m_horizontalScrollerImp.get(); }
>@@ -176,6 +181,7 @@ private:
>     bool m_requestedScrollPositionRepresentsProgrammaticScroll { false };
>     bool m_fixedElementsLayoutRelativeToFrame { false };
>     bool m_visualViewportEnabled { false };
>+    bool m_asyncFrameOrOverflowScrollingEnabled { false };
> };
> 
> } // namespace WebCore
>diff --git a/Source/WebCore/page/scrolling/ScrollingTree.cpp b/Source/WebCore/page/scrolling/ScrollingTree.cpp
>index 7fb27f0327f3c68c65dadd23ae21f831d9406b28..27907010a53263c2a0024d1104564a9f3be0a402 100644
>--- a/Source/WebCore/page/scrolling/ScrollingTree.cpp
>+++ b/Source/WebCore/page/scrolling/ScrollingTree.cpp
>@@ -65,6 +65,8 @@ bool ScrollingTree::shouldHandleWheelEventSynchronously(const PlatformWheelEvent
> 
>         const EventNames& names = eventNames();
>         IntPoint roundedPosition = roundedIntPoint(position);
>+
>+        // Event regions are affected by page scale, so no need to map through scale.
>         bool isSynchronousDispatchRegion = m_eventTrackingRegions.trackingTypeForPoint(names.wheelEvent, roundedPosition) == TrackingType::Synchronous
>             || m_eventTrackingRegions.trackingTypeForPoint(names.mousewheelEvent, roundedPosition) == TrackingType::Synchronous;
>         LOG_WITH_STREAM(Scrolling, stream << "ScrollingTree::shouldHandleWheelEventSynchronously: wheelEvent at " << wheelEvent.position() << " mapped to content point " << position << ", in non-fast region " << isSynchronousDispatchRegion);
>@@ -83,10 +85,41 @@ void ScrollingTree::setOrClearLatchedNode(const PlatformWheelEvent& wheelEvent,
>         clearLatchedNode();
> }
> 
>-void ScrollingTree::handleWheelEvent(const PlatformWheelEvent& wheelEvent)
>+ScrollingEventResult ScrollingTree::handleWheelEvent(const PlatformWheelEvent& wheelEvent)
> {
>-    if (m_rootNode)
>-        downcast<ScrollingTreeScrollingNode>(*m_rootNode).handleWheelEvent(wheelEvent);
>+    LOG_WITH_STREAM(Scrolling, stream << "ScrollingTree " << this << " handleWheelEvent (async scrolling enabled: " << asyncFrameOrOverflowScrollingEnabled() << ")");
>+
>+    if (!asyncFrameOrOverflowScrollingEnabled()) {
>+        if (m_rootNode)
>+            downcast<ScrollingTreeScrollingNode>(*m_rootNode).handleWheelEvent(wheelEvent);
>+        return ScrollingEventResult::DidNotHandleEvent;
>+    }
>+
>+    if (hasLatchedNode()) {
>+        auto* node = nodeForID(latchedNode());
>+        if (is<ScrollingTreeScrollingNode>(node))
>+            return downcast<ScrollingTreeScrollingNode>(*node).handleWheelEvent(wheelEvent);
>+    }
>+
>+    if (m_rootNode) {
>+        auto& frameScrollingNode = downcast<ScrollingTreeFrameScrollingNode>(*m_rootNode);
>+
>+        FloatPoint position = wheelEvent.position();
>+        ScrollingTreeNode* node = frameScrollingNode.scrollingNodeForPoint(LayoutPoint(position));
>+
>+        LOG_WITH_STREAM(Scrolling, stream << "ScrollingTree::handleWheelEvent found node " << (node ? node->scrollingNodeID() : 0) << " for point " << position << "\n");
>+
>+        while (node) {
>+            if (is<ScrollingTreeScrollingNode>(*node)) {
>+                auto& scrollingNode = downcast<ScrollingTreeScrollingNode>(*node);
>+                // FIXME: this needs to consult latching logic.
>+                if (scrollingNode.handleWheelEvent(wheelEvent) == ScrollingEventResult::DidHandleEvent)
>+                    return ScrollingEventResult::DidHandleEvent;
>+            }
>+            node = node->parent();
>+        }
>+    }
>+    return ScrollingEventResult::DidNotHandleEvent;
> }
> 
> void ScrollingTree::viewportChangedViaDelegatedScrolling(ScrollingNodeID nodeID, const FloatRect& fixedPositionRect, double scale)
>@@ -115,14 +148,15 @@ void ScrollingTree::commitTreeState(std::unique_ptr<ScrollingStateTree> scrollin
> {
>     bool rootStateNodeChanged = scrollingStateTree->hasNewRootStateNode();
>     
>-    LOG(Scrolling, "\nScrollingTree::commitTreeState");
>+    LOG(Scrolling, "\nScrollingTree %p commitTreeState", this);
>     
>     auto* rootNode = scrollingStateTree->rootStateNode();
>     if (rootNode
>         && (rootStateNodeChanged
>             || rootNode->hasChangedProperty(ScrollingStateFrameScrollingNode::EventTrackingRegion)
>             || rootNode->hasChangedProperty(ScrollingStateNode::ScrollLayer)
>-            || rootNode->hasChangedProperty(ScrollingStateFrameScrollingNode::VisualViewportEnabled))) {
>+            || rootNode->hasChangedProperty(ScrollingStateFrameScrollingNode::VisualViewportEnabled)
>+            || rootNode->hasChangedProperty(ScrollingStateFrameScrollingNode::AsyncFrameOrOverflowScrollingEnabled))) {
>         LockHolder lock(m_mutex);
> 
>         if (rootStateNodeChanged || rootNode->hasChangedProperty(ScrollingStateNode::ScrollLayer))
>@@ -133,6 +167,9 @@ void ScrollingTree::commitTreeState(std::unique_ptr<ScrollingStateTree> scrollin
> 
>         if (rootStateNodeChanged || rootNode->hasChangedProperty(ScrollingStateFrameScrollingNode::VisualViewportEnabled))
>             m_visualViewportEnabled = scrollingStateTree->rootStateNode()->visualViewportEnabled();
>+
>+        if (rootStateNodeChanged || rootNode->hasChangedProperty(ScrollingStateFrameScrollingNode::AsyncFrameOrOverflowScrollingEnabled))
>+            m_asyncFrameOrOverflowScrollingEnabled = scrollingStateTree->rootStateNode()->asyncFrameOrOverflowScrollingEnabled();
>     }
>     
>     bool scrollRequestIsProgammatic = rootNode ? rootNode->requestedScrollPositionRepresentsProgrammaticScroll() : false;
>@@ -223,6 +260,12 @@ ScrollingTreeNode* ScrollingTree::nodeForID(ScrollingNodeID nodeID) const
>     return m_nodeMap.get(nodeID);
> }
> 
>+void ScrollingTree::setAsyncFrameOrOverflowScrollingEnabled(bool enabled)
>+{
>+    LockHolder lock(m_mutex);
>+    m_asyncFrameOrOverflowScrollingEnabled = enabled;
>+}
>+
> void ScrollingTree::setMainFramePinState(bool pinnedToTheLeft, bool pinnedToTheRight, bool pinnedToTheTop, bool pinnedToTheBottom)
> {
>     LockHolder locker(m_swipeStateMutex);
>diff --git a/Source/WebCore/page/scrolling/ScrollingTree.h b/Source/WebCore/page/scrolling/ScrollingTree.h
>index ec3dd6e0766537b53ac3a475e968b11697eca77f..d9378532ddc619ea72a5a2a3fa22cd84c832b0ca 100644
>--- a/Source/WebCore/page/scrolling/ScrollingTree.h
>+++ b/Source/WebCore/page/scrolling/ScrollingTree.h
>@@ -50,19 +50,17 @@ public:
>     WEBCORE_EXPORT ScrollingTree();
>     WEBCORE_EXPORT virtual ~ScrollingTree();
> 
>-    enum EventResult {
>-        DidNotHandleEvent,
>-        DidHandleEvent,
>-        SendToMainThread
>-    };
>-    
>     virtual bool isThreadedScrollingTree() const { return false; }
>     virtual bool isRemoteScrollingTree() const { return false; }
>     virtual bool isScrollingTreeIOS() const { return false; }
> 
>     bool visualViewportEnabled() const { return m_visualViewportEnabled; }
> 
>-    virtual EventResult tryToHandleWheelEvent(const PlatformWheelEvent&) = 0;
>+    // This implies that we'll do hit-testing in the scrolling tree.
>+    bool asyncFrameOrOverflowScrollingEnabled() const { return m_asyncFrameOrOverflowScrollingEnabled; }
>+    void setAsyncFrameOrOverflowScrollingEnabled(bool);
>+
>+    virtual ScrollingEventResult tryToHandleWheelEvent(const PlatformWheelEvent&) = 0;
>     WEBCORE_EXPORT bool shouldHandleWheelEventSynchronously(const PlatformWheelEvent&);
>     
>     void setMainFrameIsRubberBanding(bool);
>@@ -160,7 +158,7 @@ protected:
>     void setMainFrameScrollPosition(FloatPoint);
>     void setVisualViewportEnabled(bool b) { m_visualViewportEnabled = b; }
> 
>-    WEBCORE_EXPORT virtual void handleWheelEvent(const PlatformWheelEvent&);
>+    WEBCORE_EXPORT virtual ScrollingEventResult handleWheelEvent(const PlatformWheelEvent&);
> 
> private:
>     using OrphanScrollingNodeMap = HashMap<ScrollingNodeID, RefPtr<ScrollingTreeNode>>;
>@@ -196,6 +194,7 @@ private:
>     bool m_scrollingPerformanceLoggingEnabled { false };
>     bool m_isHandlingProgrammaticScroll { false };
>     bool m_visualViewportEnabled { false };
>+    bool m_asyncFrameOrOverflowScrollingEnabled { false };
> };
>     
> } // namespace WebCore
>diff --git a/Source/WebCore/page/scrolling/ScrollingTreeFrameHostingNode.cpp b/Source/WebCore/page/scrolling/ScrollingTreeFrameHostingNode.cpp
>index 24ad08fdb767d6ed35a7e9eedbe61c58b9601143..e1607e7700b757124526531dd190cf44bfbacf5e 100644
>--- a/Source/WebCore/page/scrolling/ScrollingTreeFrameHostingNode.cpp
>+++ b/Source/WebCore/page/scrolling/ScrollingTreeFrameHostingNode.cpp
>@@ -66,6 +66,11 @@ void ScrollingTreeFrameHostingNode::updateLayersAfterAncestorChange(const Scroll
>         child->updateLayersAfterAncestorChange(changedNode, fixedPositionRect, cumulativeDelta);
> }
> 
>+LayoutPoint ScrollingTreeFrameHostingNode::parentToLocalPoint(LayoutPoint point) const
>+{
>+    return point - toLayoutSize(parentRelativeScrollableRect().location());
>+}
>+
> void ScrollingTreeFrameHostingNode::dumpProperties(TextStream& ts, ScrollingStateTreeAsTextBehavior behavior) const
> {
>     ts << "frame hosting node";
>diff --git a/Source/WebCore/page/scrolling/ScrollingTreeFrameHostingNode.h b/Source/WebCore/page/scrolling/ScrollingTreeFrameHostingNode.h
>index 5c3b7974358012e2045639797f11d7f8022efe3d..ddf7adc61c405e7398635d43e6505d0994ceb7c5 100644
>--- a/Source/WebCore/page/scrolling/ScrollingTreeFrameHostingNode.h
>+++ b/Source/WebCore/page/scrolling/ScrollingTreeFrameHostingNode.h
>@@ -46,6 +46,8 @@ private:
> 
>     const LayoutRect& parentRelativeScrollableRect() const { return m_parentRelativeScrollableRect; }
> 
>+    LayoutPoint parentToLocalPoint(LayoutPoint) const final;
>+
>     WEBCORE_EXPORT void dumpProperties(WTF::TextStream&, ScrollingStateTreeAsTextBehavior) const override;
> 
>     LayoutRect m_parentRelativeScrollableRect;
>diff --git a/Source/WebCore/page/scrolling/ScrollingTreeFrameScrollingNode.cpp b/Source/WebCore/page/scrolling/ScrollingTreeFrameScrollingNode.cpp
>index f15a559d6e7114292a8ffc6976246d9c89024c8a..d0a9fb531e268909916b6a1c860d36fb64bf50ad 100644
>--- a/Source/WebCore/page/scrolling/ScrollingTreeFrameScrollingNode.cpp
>+++ b/Source/WebCore/page/scrolling/ScrollingTreeFrameScrollingNode.cpp
>@@ -126,6 +126,17 @@ FloatSize ScrollingTreeFrameScrollingNode::viewToContentsOffset(const FloatPoint
>     return toFloatSize(scrollPosition) - FloatSize(0, headerHeight() + topContentInset());
> }
> 
>+LayoutPoint ScrollingTreeFrameScrollingNode::parentToLocalPoint(LayoutPoint point) const
>+{
>+    return point - LayoutSize(0, headerHeight() + topContentInset());
>+}
>+
>+LayoutPoint ScrollingTreeFrameScrollingNode::localToContentsPoint(LayoutPoint point) const
>+{
>+    auto scrolledPoint = point + LayoutPoint(scrollPosition());
>+    return scrolledPoint.scaled(1 / frameScaleFactor());
>+}
>+
> void ScrollingTreeFrameScrollingNode::dumpProperties(TextStream& ts, ScrollingStateTreeAsTextBehavior behavior) const
> {
>     ts << "frame scrolling node";
>diff --git a/Source/WebCore/page/scrolling/ScrollingTreeFrameScrollingNode.h b/Source/WebCore/page/scrolling/ScrollingTreeFrameScrollingNode.h
>index 7b08a675e2c29640dc1add92d8d3132b7ea80656..18c913f7b40d7c3b68dcf3f0a173f8a98ee5a9a0 100644
>--- a/Source/WebCore/page/scrolling/ScrollingTreeFrameScrollingNode.h
>+++ b/Source/WebCore/page/scrolling/ScrollingTreeFrameScrollingNode.h
>@@ -44,7 +44,7 @@ public:
>     // FIXME: We should implement this when we support ScrollingTreeScrollingNodes as children.
>     void updateLayersAfterAncestorChange(const ScrollingTreeNode& /*changedNode*/, const FloatRect& /*fixedPositionRect*/, const FloatSize& /*cumulativeDelta*/) override { }
> 
>-    void handleWheelEvent(const PlatformWheelEvent&) override = 0;
>+    ScrollingEventResult handleWheelEvent(const PlatformWheelEvent&) override = 0;
>     void setScrollPosition(const FloatPoint&) override;
>     void setScrollPositionWithoutContentEdgeConstraints(const FloatPoint&) override = 0;
> 
>@@ -80,6 +80,9 @@ protected:
>     ScrollBehaviorForFixedElements scrollBehaviorForFixedElements() const { return m_behaviorForFixed; }
> 
> private:
>+    WEBCORE_EXPORT LayoutPoint parentToLocalPoint(LayoutPoint) const final;
>+    WEBCORE_EXPORT LayoutPoint localToContentsPoint(LayoutPoint) const final;
>+
>     WEBCORE_EXPORT void dumpProperties(WTF::TextStream&, ScrollingStateTreeAsTextBehavior) const override;
> 
>     FloatRect m_layoutViewport;
>diff --git a/Source/WebCore/page/scrolling/ScrollingTreeNode.cpp b/Source/WebCore/page/scrolling/ScrollingTreeNode.cpp
>index 0503cdb26caf7a20d1d1e10d22f6588503b54213..5855d5ea5588161f2ee4cc3bee9bf38e9beca3b3 100644
>--- a/Source/WebCore/page/scrolling/ScrollingTreeNode.cpp
>+++ b/Source/WebCore/page/scrolling/ScrollingTreeNode.cpp
>@@ -98,6 +98,21 @@ void ScrollingTreeNode::dump(TextStream& ts, ScrollingStateTreeAsTextBehavior be
>     }
> }
> 
>+ScrollingTreeScrollingNode* ScrollingTreeNode::scrollingNodeForPoint(LayoutPoint parentPoint) const
>+{
>+    LayoutPoint localPoint = parentToLocalPoint(parentPoint);
>+    LayoutPoint contentsPoint = localToContentsPoint(localPoint);
>+
>+    if (children()) {
>+        for (auto iterator = children()->rbegin(), end = children()->rend(); iterator != end; iterator++) {
>+            if (auto node = (**iterator).scrollingNodeForPoint(contentsPoint))
>+                return node;
>+        }
>+    }
>+
>+    return nullptr;
>+}
>+
> } // namespace WebCore
> 
> #endif // ENABLE(ASYNC_SCROLLING)
>diff --git a/Source/WebCore/page/scrolling/ScrollingTreeNode.h b/Source/WebCore/page/scrolling/ScrollingTreeNode.h
>index 2ae1a361f8197ad78ccf26d15a9c944b3d624060..b5096ab7880dd1b3d0fb63988c194aba5b195515 100644
>--- a/Source/WebCore/page/scrolling/ScrollingTreeNode.h
>+++ b/Source/WebCore/page/scrolling/ScrollingTreeNode.h
>@@ -40,6 +40,7 @@ namespace WebCore {
> class ScrollingStateFixedNode;
> class ScrollingStateScrollingNode;
> class ScrollingTreeFrameScrollingNode;
>+class ScrollingTreeScrollingNode;
> 
> class ScrollingTreeNode : public RefCounted<ScrollingTreeNode> {
> public:
>@@ -64,6 +65,7 @@ public:
>     void setParent(ScrollingTreeNode* parent) { m_parent = parent; }
> 
>     Vector<RefPtr<ScrollingTreeNode>>* children() { return m_children.get(); }
>+    const Vector<RefPtr<ScrollingTreeNode>>* children() const { return m_children.get(); }
> 
>     void appendChild(Ref<ScrollingTreeNode>&&);
>     void removeChild(ScrollingTreeNode&);
>@@ -72,6 +74,10 @@ public:
> 
>     WEBCORE_EXPORT void dump(WTF::TextStream&, ScrollingStateTreeAsTextBehavior) const;
> 
>+    virtual LayoutPoint parentToLocalPoint(LayoutPoint point) const { return point; }
>+    virtual LayoutPoint localToContentsPoint(LayoutPoint point) const { return point; }
>+    virtual ScrollingTreeScrollingNode* scrollingNodeForPoint(LayoutPoint) const;
>+
> protected:
>     ScrollingTreeNode(ScrollingTree&, ScrollingNodeType, ScrollingNodeID);
>     ScrollingTree& scrollingTree() const { return m_scrollingTree; }
>diff --git a/Source/WebCore/page/scrolling/ScrollingTreeScrollingNode.cpp b/Source/WebCore/page/scrolling/ScrollingTreeScrollingNode.cpp
>index 6b56b1fe6c6bd9fb0320da74785e1cd345521b0f..dcc96f1cb62517931119f9f0f63778068512a6f4 100644
>--- a/Source/WebCore/page/scrolling/ScrollingTreeScrollingNode.cpp
>+++ b/Source/WebCore/page/scrolling/ScrollingTreeScrollingNode.cpp
>@@ -28,6 +28,7 @@
> 
> #if ENABLE(ASYNC_SCROLLING)
> 
>+#include "Logging.h"
> #include "ScrollingStateScrollingNode.h"
> #include "ScrollingStateTree.h"
> #include "ScrollingTree.h"
>@@ -133,6 +134,35 @@ FloatPoint ScrollingTreeScrollingNode::maximumScrollPosition() const
>     return FloatPoint(contentSizePoint - scrollableAreaSize()).expandedTo(FloatPoint());
> }
> 
>+bool ScrollingTreeScrollingNode::scrollLimitReached(const PlatformWheelEvent& wheelEvent) const
>+{
>+    FloatPoint oldScrollPosition = scrollPosition();
>+    FloatPoint newScrollPosition = oldScrollPosition + FloatSize(wheelEvent.deltaX(), -wheelEvent.deltaY());
>+    newScrollPosition = newScrollPosition.constrainedBetween(minimumScrollPosition(), maximumScrollPosition());
>+    return newScrollPosition == oldScrollPosition;
>+}
>+
>+LayoutPoint ScrollingTreeScrollingNode::parentToLocalPoint(LayoutPoint point) const
>+{
>+    return point - toLayoutSize(parentRelativeScrollableRect().location());
>+}
>+
>+LayoutPoint ScrollingTreeScrollingNode::localToContentsPoint(LayoutPoint point) const
>+{
>+    return point + LayoutPoint(scrollPosition());
>+}
>+
>+ScrollingTreeScrollingNode* ScrollingTreeScrollingNode::scrollingNodeForPoint(LayoutPoint parentPoint) const
>+{
>+    if (auto* node = ScrollingTreeNode::scrollingNodeForPoint(parentPoint))
>+        return node;
>+
>+    if (parentRelativeScrollableRect().contains(parentPoint))
>+        return const_cast<ScrollingTreeScrollingNode*>(this);
>+
>+    return nullptr;
>+}
>+
> void ScrollingTreeScrollingNode::dumpProperties(TextStream& ts, ScrollingStateTreeAsTextBehavior behavior) const
> {
>     ScrollingTreeNode::dumpProperties(ts, behavior);
>diff --git a/Source/WebCore/page/scrolling/ScrollingTreeScrollingNode.h b/Source/WebCore/page/scrolling/ScrollingTreeScrollingNode.h
>index 70bd81d006d6e78f1b0de7aaf9312dbbc4011f37..f652b2d261e637188c69bd13f4471192e9baa573 100644
>--- a/Source/WebCore/page/scrolling/ScrollingTreeScrollingNode.h
>+++ b/Source/WebCore/page/scrolling/ScrollingTreeScrollingNode.h
>@@ -55,7 +55,7 @@ public:
> 
>     WEBCORE_EXPORT void updateLayersAfterAncestorChange(const ScrollingTreeNode& changedNode, const FloatRect& fixedPositionRect, const FloatSize& cumulativeDelta) override;
> 
>-    virtual void handleWheelEvent(const PlatformWheelEvent&) = 0;
>+    virtual ScrollingEventResult handleWheelEvent(const PlatformWheelEvent&) = 0;
>     WEBCORE_EXPORT virtual void setScrollPosition(const FloatPoint&);
>     WEBCORE_EXPORT virtual void setScrollPositionWithoutContentEdgeConstraints(const FloatPoint&);
> 
>@@ -79,6 +79,9 @@ public:
> 
>     bool useDarkAppearanceForScrollbars() const { return m_scrollableAreaParameters.useDarkAppearanceForScrollbars; }
> 
>+    bool scrollLimitReached(const PlatformWheelEvent&) const;
>+    WEBCORE_EXPORT ScrollingTreeScrollingNode* scrollingNodeForPoint(LayoutPoint) const override;
>+
> protected:
>     ScrollingTreeScrollingNode(ScrollingTree&, ScrollingNodeType, ScrollingNodeID);
> 
>@@ -106,6 +109,9 @@ protected:
> 
>     bool canHaveScrollbars() const { return m_scrollableAreaParameters.horizontalScrollbarMode != ScrollbarAlwaysOff || m_scrollableAreaParameters.verticalScrollbarMode != ScrollbarAlwaysOff; }
> 
>+    WEBCORE_EXPORT LayoutPoint parentToLocalPoint(LayoutPoint) const override;
>+    WEBCORE_EXPORT LayoutPoint localToContentsPoint(LayoutPoint) const override;
>+
>     WEBCORE_EXPORT void dumpProperties(WTF::TextStream&, ScrollingStateTreeAsTextBehavior) const override;
> 
> private:
>diff --git a/Source/WebCore/page/scrolling/ThreadedScrollingTree.cpp b/Source/WebCore/page/scrolling/ThreadedScrollingTree.cpp
>index 06b319609ea99223f00e11a9a81c1c64afa24c3c..127b95fc406c96d1ce040667b85870211bbe69ac 100644
>--- a/Source/WebCore/page/scrolling/ThreadedScrollingTree.cpp
>+++ b/Source/WebCore/page/scrolling/ThreadedScrollingTree.cpp
>@@ -48,26 +48,26 @@ ThreadedScrollingTree::~ThreadedScrollingTree()
>     ASSERT(!m_scrollingCoordinator);
> }
> 
>-ScrollingTree::EventResult ThreadedScrollingTree::tryToHandleWheelEvent(const PlatformWheelEvent& wheelEvent)
>+ScrollingEventResult ThreadedScrollingTree::tryToHandleWheelEvent(const PlatformWheelEvent& wheelEvent)
> {
>     if (shouldHandleWheelEventSynchronously(wheelEvent))
>-        return SendToMainThread;
>+        return ScrollingEventResult::SendToMainThread;
> 
>     if (willWheelEventStartSwipeGesture(wheelEvent))
>-        return DidNotHandleEvent;
>+        return ScrollingEventResult::DidNotHandleEvent;
> 
>     RefPtr<ThreadedScrollingTree> protectedThis(this);
>     ScrollingThread::dispatch([protectedThis, wheelEvent] {
>         protectedThis->handleWheelEvent(wheelEvent);
>     });
>     
>-    return DidHandleEvent;
>+    return ScrollingEventResult::DidHandleEvent;
> }
> 
>-void ThreadedScrollingTree::handleWheelEvent(const PlatformWheelEvent& wheelEvent)
>+ScrollingEventResult ThreadedScrollingTree::handleWheelEvent(const PlatformWheelEvent& wheelEvent)
> {
>     ASSERT(ScrollingThread::isCurrentThread());
>-    ScrollingTree::handleWheelEvent(wheelEvent);
>+    return ScrollingTree::handleWheelEvent(wheelEvent);
> }
> 
> void ThreadedScrollingTree::invalidate()
>diff --git a/Source/WebCore/page/scrolling/ThreadedScrollingTree.h b/Source/WebCore/page/scrolling/ThreadedScrollingTree.h
>index 402c2d92b2a2e8520b6d71c53d4e5ab368772188..e506ddd05b973a3db1aa68a372f71ecb06364e8a 100644
>--- a/Source/WebCore/page/scrolling/ThreadedScrollingTree.h
>+++ b/Source/WebCore/page/scrolling/ThreadedScrollingTree.h
>@@ -45,12 +45,12 @@ public:
> 
>     void commitTreeState(std::unique_ptr<ScrollingStateTree>) override;
> 
>-    void handleWheelEvent(const PlatformWheelEvent&) override;
>+    ScrollingEventResult handleWheelEvent(const PlatformWheelEvent&) override;
> 
>     // Can be called from any thread. Will try to handle the wheel event on the scrolling thread.
>     // Returns true if the wheel event can be handled on the scrolling thread and false if the
>     // event must be sent again to the WebCore event handler.
>-    EventResult tryToHandleWheelEvent(const PlatformWheelEvent&) override;
>+    ScrollingEventResult tryToHandleWheelEvent(const PlatformWheelEvent&) override;
> 
>     void invalidate() override;
> 
>diff --git a/Source/WebCore/page/scrolling/ios/ScrollingCoordinatorIOS.h b/Source/WebCore/page/scrolling/ios/ScrollingCoordinatorIOS.h
>index 595304c6ab5010159d0dba0a6095de61eae1f312..9cf639ecbd4e07589cb9a28bcf7d9b2b4f896fe0 100644
>--- a/Source/WebCore/page/scrolling/ios/ScrollingCoordinatorIOS.h
>+++ b/Source/WebCore/page/scrolling/ios/ScrollingCoordinatorIOS.h
>@@ -47,7 +47,7 @@ public:
>     void commitTreeStateIfNeeded() override;
> 
>     // Handle the wheel event on the scrolling thread. Returns whether the event was handled or not.
>-    bool handleWheelEvent(FrameView&, const PlatformWheelEvent&) override { return false; }
>+    ScrollingEventResult handleWheelEvent(FrameView&, const PlatformWheelEvent&) override { return ScrollingEventResult::DidNotHandleEvent; }
> 
> private:
>     void scheduleTreeStateCommit() override;
>diff --git a/Source/WebCore/page/scrolling/ios/ScrollingTreeFrameScrollingNodeIOS.h b/Source/WebCore/page/scrolling/ios/ScrollingTreeFrameScrollingNodeIOS.h
>index 56a4790747d6035c0e934a26d7f4cd9951500f7b..8a61a0f1c0063ddd59943f1593a6db36763d4541 100644
>--- a/Source/WebCore/page/scrolling/ios/ScrollingTreeFrameScrollingNodeIOS.h
>+++ b/Source/WebCore/page/scrolling/ios/ScrollingTreeFrameScrollingNodeIOS.h
>@@ -46,7 +46,7 @@ protected:
>     void commitStateBeforeChildren(const ScrollingStateNode&) override;
>     void commitStateAfterChildren(const ScrollingStateNode&) override;
> 
>-    void handleWheelEvent(const PlatformWheelEvent&) override { }
>+    ScrollingEventResult handleWheelEvent(const PlatformWheelEvent&) override;
> 
>     FloatPoint scrollPosition() const override;
>     void setScrollPositionWithoutContentEdgeConstraints(const FloatPoint&) override;
>diff --git a/Source/WebCore/page/scrolling/ios/ScrollingTreeFrameScrollingNodeIOS.mm b/Source/WebCore/page/scrolling/ios/ScrollingTreeFrameScrollingNodeIOS.mm
>index 24debd0bed7bce81e3d39f885c95a7a3968244f1..a4146a2a63610605e8b2fd3d52a758bdab4d3bdd 100644
>--- a/Source/WebCore/page/scrolling/ios/ScrollingTreeFrameScrollingNodeIOS.mm
>+++ b/Source/WebCore/page/scrolling/ios/ScrollingTreeFrameScrollingNodeIOS.mm
>@@ -96,6 +96,11 @@ void ScrollingTreeFrameScrollingNodeIOS::commitStateAfterChildren(const Scrollin
>         setScrollPosition(scrollingStateNode.requestedScrollPosition());
> }
> 
>+ScrollingEventResult ScrollingTreeFrameScrollingNodeIOS::handleWheelEvent(const PlatformWheelEvent&)
>+{
>+    return ScrollingEventResult::DidNotHandleEvent;
>+}
>+
> FloatPoint ScrollingTreeFrameScrollingNodeIOS::scrollPosition() const
> {
>     if (shouldUpdateScrollLayerPositionSynchronously())
>diff --git a/Source/WebCore/page/scrolling/ios/ScrollingTreeIOS.h b/Source/WebCore/page/scrolling/ios/ScrollingTreeIOS.h
>index fcc7ee2071301fb01d81153df391056d1ac119c4..e9035d0a22c904e8008d73c920e130d7696e9b8e 100644
>--- a/Source/WebCore/page/scrolling/ios/ScrollingTreeIOS.h
>+++ b/Source/WebCore/page/scrolling/ios/ScrollingTreeIOS.h
>@@ -45,8 +45,8 @@ private:
>     bool isScrollingTreeIOS() const final { return true; }
> 
>     // No wheel events on iOS
>-    void handleWheelEvent(const PlatformWheelEvent&) final { }
>-    EventResult tryToHandleWheelEvent(const PlatformWheelEvent&) final { return DidNotHandleEvent; }
>+    ScrollingEventResult handleWheelEvent(const PlatformWheelEvent&) final { return ScrollingEventResult::DidNotHandleEvent; }
>+    ScrollingEventResult tryToHandleWheelEvent(const PlatformWheelEvent&) final { return ScrollingEventResult::DidNotHandleEvent; }
> 
>     void invalidate() final;
> 
>diff --git a/Source/WebCore/page/scrolling/mac/ScrollingCoordinatorMac.h b/Source/WebCore/page/scrolling/mac/ScrollingCoordinatorMac.h
>index abf0d79911fd1233785b7c190d68ff487eea330c..893969b6a683b6f4b3fef405da1224a9282d139f 100644
>--- a/Source/WebCore/page/scrolling/mac/ScrollingCoordinatorMac.h
>+++ b/Source/WebCore/page/scrolling/mac/ScrollingCoordinatorMac.h
>@@ -47,7 +47,7 @@ public:
>     void commitTreeStateIfNeeded() override;
> 
>     // Handle the wheel event on the scrolling thread. Returns whether the event was handled or not.
>-    bool handleWheelEvent(FrameView&, const PlatformWheelEvent&) override;
>+    ScrollingEventResult handleWheelEvent(FrameView&, const PlatformWheelEvent&) override;
> 
> private:
>     void scheduleTreeStateCommit() override;
>diff --git a/Source/WebCore/page/scrolling/mac/ScrollingCoordinatorMac.mm b/Source/WebCore/page/scrolling/mac/ScrollingCoordinatorMac.mm
>index 572e427b161039bd2a3356af884a339e9d73d9a3..d157ceb963143f878e81bbaa502474d0737c7ddd 100644
>--- a/Source/WebCore/page/scrolling/mac/ScrollingCoordinatorMac.mm
>+++ b/Source/WebCore/page/scrolling/mac/ScrollingCoordinatorMac.mm
>@@ -82,19 +82,19 @@ void ScrollingCoordinatorMac::commitTreeStateIfNeeded()
>     m_scrollingStateTreeCommitterTimer.stop();
> }
> 
>-bool ScrollingCoordinatorMac::handleWheelEvent(FrameView&, const PlatformWheelEvent& wheelEvent)
>+ScrollingEventResult ScrollingCoordinatorMac::handleWheelEvent(FrameView&, const PlatformWheelEvent& wheelEvent)
> {
>     ASSERT(isMainThread());
>     ASSERT(m_page);
> 
>     if (scrollingTree()->willWheelEventStartSwipeGesture(wheelEvent))
>-        return false;
>+        return ScrollingEventResult::DidNotHandleEvent;
> 
>     RefPtr<ThreadedScrollingTree> threadedScrollingTree = downcast<ThreadedScrollingTree>(scrollingTree());
>     ScrollingThread::dispatch([threadedScrollingTree, wheelEvent] {
>         threadedScrollingTree->handleWheelEvent(wheelEvent);
>     });
>-    return true;
>+    return ScrollingEventResult::DidHandleEvent;
> }
> 
> void ScrollingCoordinatorMac::scheduleTreeStateCommit()
>diff --git a/Source/WebCore/page/scrolling/mac/ScrollingTreeFrameScrollingNodeMac.h b/Source/WebCore/page/scrolling/mac/ScrollingTreeFrameScrollingNodeMac.h
>index 5faf3fb5c44f81d4eb4de1976d52ac9663cef0da..178f1af644aad371c37d3df3a45d2b4b9c9532ad 100644
>--- a/Source/WebCore/page/scrolling/mac/ScrollingTreeFrameScrollingNodeMac.h
>+++ b/Source/WebCore/page/scrolling/mac/ScrollingTreeFrameScrollingNodeMac.h
>@@ -51,7 +51,7 @@ protected:
>     void commitStateBeforeChildren(const ScrollingStateNode&) override;
>     void commitStateAfterChildren(const ScrollingStateNode&) override;
> 
>-    void handleWheelEvent(const PlatformWheelEvent&) override;
>+    ScrollingEventResult handleWheelEvent(const PlatformWheelEvent&) override;
> 
>     // ScrollController member functions.
>     bool allowsHorizontalStretching(const PlatformWheelEvent&) override;
>diff --git a/Source/WebCore/page/scrolling/mac/ScrollingTreeFrameScrollingNodeMac.mm b/Source/WebCore/page/scrolling/mac/ScrollingTreeFrameScrollingNodeMac.mm
>index 06cb84975716abfa7c23e3dd1153255c27bc5668..0b3cbdb15a51df737c55342fec7c39446321e551 100644
>--- a/Source/WebCore/page/scrolling/mac/ScrollingTreeFrameScrollingNodeMac.mm
>+++ b/Source/WebCore/page/scrolling/mac/ScrollingTreeFrameScrollingNodeMac.mm
>@@ -184,10 +184,13 @@ void ScrollingTreeFrameScrollingNodeMac::commitStateAfterChildren(const Scrollin
>         updateMainFramePinState(scrollPosition());
> }
> 
>-void ScrollingTreeFrameScrollingNodeMac::handleWheelEvent(const PlatformWheelEvent& wheelEvent)
>+ScrollingEventResult ScrollingTreeFrameScrollingNodeMac::handleWheelEvent(const PlatformWheelEvent& wheelEvent)
> {
>     if (!canHaveScrollbars())
>-        return;
>+        return ScrollingEventResult::DidNotHandleEvent;
>+
>+    if (scrollLimitReached(wheelEvent))
>+        return ScrollingEventResult::DidNotHandleEvent;
> 
>     if (wheelEvent.momentumPhase() == PlatformWheelEventPhaseBegan) {
>         [m_verticalScrollerImp setUsePresentationValue:YES];
>@@ -215,6 +218,9 @@ void ScrollingTreeFrameScrollingNodeMac::handleWheelEvent(const PlatformWheelEve
> #endif
>     scrollingTree().setOrClearLatchedNode(wheelEvent, scrollingNodeID());
>     scrollingTree().handleWheelEventPhase(wheelEvent.phase());
>+    
>+    // FIXME: This needs to return whether the event was handled.
>+    return ScrollingEventResult::DidHandleEvent;
> }
> 
> // FIXME: We should find a way to share some of the code from newGestureIsStarting(), isAlreadyPinnedInDirectionOfGesture(),
>diff --git a/Source/WebCore/page/scrolling/mac/ScrollingTreeOverflowScrollingNodeMac.h b/Source/WebCore/page/scrolling/mac/ScrollingTreeOverflowScrollingNodeMac.h
>index f1eedbedef3db06259ad16c5f707e5d2b3538962..ce397b9926ba6e77df0ab0de584f9a0b624edca1 100644
>--- a/Source/WebCore/page/scrolling/mac/ScrollingTreeOverflowScrollingNodeMac.h
>+++ b/Source/WebCore/page/scrolling/mac/ScrollingTreeOverflowScrollingNodeMac.h
>@@ -51,7 +51,7 @@ private:
> 
>     void updateLayersAfterAncestorChange(const WebCore::ScrollingTreeNode& changedNode, const WebCore::FloatRect& fixedPositionRect, const WebCore::FloatSize& cumulativeDelta) override;
> 
>-    void handleWheelEvent(const WebCore::PlatformWheelEvent&) override { }
>+    ScrollingEventResult handleWheelEvent(const WebCore::PlatformWheelEvent&) override { return ScrollingEventResult::DidNotHandleEvent; }
> };
> 
> } // namespace WebKit
>diff --git a/Source/WebKit/Shared/RemoteLayerTree/RemoteScrollingCoordinatorTransaction.cpp b/Source/WebKit/Shared/RemoteLayerTree/RemoteScrollingCoordinatorTransaction.cpp
>index 0d01f33c1c8284eaeba57f67f9cae10a41f56905..8b38a42ecd36d1bdc9afd830fb40aa14d5eb9fe4 100644
>--- a/Source/WebKit/Shared/RemoteLayerTree/RemoteScrollingCoordinatorTransaction.cpp
>+++ b/Source/WebKit/Shared/RemoteLayerTree/RemoteScrollingCoordinatorTransaction.cpp
>@@ -158,6 +158,7 @@ void ArgumentCoder<ScrollingStateFrameScrollingNode>::encode(Encoder& encoder, c
>     SCROLLING_NODE_ENCODE(ScrollingStateFrameScrollingNode::TopContentInset, topContentInset)
>     SCROLLING_NODE_ENCODE(ScrollingStateFrameScrollingNode::FixedElementsLayoutRelativeToFrame, fixedElementsLayoutRelativeToFrame)
>     SCROLLING_NODE_ENCODE(ScrollingStateFrameScrollingNode::VisualViewportEnabled, visualViewportEnabled)
>+    // AsyncFrameOrOverflowScrollingEnabled is not relevant for UI-side compositing.
>     SCROLLING_NODE_ENCODE(ScrollingStateFrameScrollingNode::LayoutViewport, layoutViewport)
>     SCROLLING_NODE_ENCODE(ScrollingStateFrameScrollingNode::MinLayoutViewportOrigin, minLayoutViewportOrigin)
>     SCROLLING_NODE_ENCODE(ScrollingStateFrameScrollingNode::MaxLayoutViewportOrigin, maxLayoutViewportOrigin)
>diff --git a/Source/WebKit/UIProcess/RemoteLayerTree/RemoteScrollingCoordinatorProxy.cpp b/Source/WebKit/UIProcess/RemoteLayerTree/RemoteScrollingCoordinatorProxy.cpp
>index f964fc981ed314cab7eb44ef83cd369287fae34c..9752e9544398d9016312a581bf9a4d1620adcc60 100644
>--- a/Source/WebKit/UIProcess/RemoteLayerTree/RemoteScrollingCoordinatorProxy.cpp
>+++ b/Source/WebKit/UIProcess/RemoteLayerTree/RemoteScrollingCoordinatorProxy.cpp
>@@ -151,8 +151,8 @@ void RemoteScrollingCoordinatorProxy::connectStateNodeLayers(ScrollingStateTree&
> 
> bool RemoteScrollingCoordinatorProxy::handleWheelEvent(const PlatformWheelEvent& event)
> {
>-    ScrollingTree::EventResult result = m_scrollingTree->tryToHandleWheelEvent(event);
>-    return result == ScrollingTree::DidHandleEvent; // FIXME: handle other values.
>+    ScrollingEventResult result = m_scrollingTree->tryToHandleWheelEvent(event);
>+    return result == ScrollingEventResult::DidHandleEvent; // FIXME: handle other values.
> }
> 
> void RemoteScrollingCoordinatorProxy::handleMouseEvent(const WebCore::PlatformMouseEvent& event)
>diff --git a/Source/WebKit/UIProcess/RemoteLayerTree/RemoteScrollingTree.cpp b/Source/WebKit/UIProcess/RemoteLayerTree/RemoteScrollingTree.cpp
>index 26d970930ab46b7f2e95b626721838fadc2c6f38..f30e25ca112918babab686a051112be7758c7161 100644
>--- a/Source/WebKit/UIProcess/RemoteLayerTree/RemoteScrollingTree.cpp
>+++ b/Source/WebKit/UIProcess/RemoteLayerTree/RemoteScrollingTree.cpp
>@@ -59,16 +59,16 @@ RemoteScrollingTree::~RemoteScrollingTree()
> {
> }
> 
>-ScrollingTree::EventResult RemoteScrollingTree::tryToHandleWheelEvent(const PlatformWheelEvent& wheelEvent)
>+ScrollingEventResult RemoteScrollingTree::tryToHandleWheelEvent(const PlatformWheelEvent& wheelEvent)
> {
>     if (shouldHandleWheelEventSynchronously(wheelEvent))
>-        return SendToMainThread;
>+        return ScrollingEventResult::SendToMainThread;
> 
>     if (willWheelEventStartSwipeGesture(wheelEvent))
>-        return DidNotHandleEvent;
>+        return ScrollingEventResult::DidNotHandleEvent;
> 
>     handleWheelEvent(wheelEvent);
>-    return DidHandleEvent;
>+    return ScrollingEventResult::DidHandleEvent;
> }
> 
> #if PLATFORM(MAC)
>diff --git a/Source/WebKit/UIProcess/RemoteLayerTree/RemoteScrollingTree.h b/Source/WebKit/UIProcess/RemoteLayerTree/RemoteScrollingTree.h
>index 685b4f5118764a647cc1a0ea21c81d3fa16f2dd9..a5f46521fcec84f1b10a1c04b6e408e02e508bf7 100644
>--- a/Source/WebKit/UIProcess/RemoteLayerTree/RemoteScrollingTree.h
>+++ b/Source/WebKit/UIProcess/RemoteLayerTree/RemoteScrollingTree.h
>@@ -45,7 +45,7 @@ public:
>     virtual ~RemoteScrollingTree();
> 
>     bool isRemoteScrollingTree() const override { return true; }
>-    EventResult tryToHandleWheelEvent(const WebCore::PlatformWheelEvent&) override;
>+    WebCore::ScrollingEventResult tryToHandleWheelEvent(const WebCore::PlatformWheelEvent&) override;
> 
>     void handleMouseEvent(const WebCore::PlatformMouseEvent&);
> 
>diff --git a/Source/WebKit/UIProcess/RemoteLayerTree/ios/ScrollingTreeOverflowScrollingNodeIOS.h b/Source/WebKit/UIProcess/RemoteLayerTree/ios/ScrollingTreeOverflowScrollingNodeIOS.h
>index 842a9877a74d51e90689d0114ac470ca0fbad16f..bfbeb08614eb458518804c7351ddc49cc42a797b 100644
>--- a/Source/WebKit/UIProcess/RemoteLayerTree/ios/ScrollingTreeOverflowScrollingNodeIOS.h
>+++ b/Source/WebKit/UIProcess/RemoteLayerTree/ios/ScrollingTreeOverflowScrollingNodeIOS.h
>@@ -53,7 +53,7 @@ private:
> 
>     void updateLayersAfterAncestorChange(const WebCore::ScrollingTreeNode& changedNode, const WebCore::FloatRect& fixedPositionRect, const WebCore::FloatSize& cumulativeDelta) override;
> 
>-    void handleWheelEvent(const WebCore::PlatformWheelEvent&) override { }
>+    WebCore::ScrollingEventResult handleWheelEvent(const WebCore::PlatformWheelEvent&) override { return ScrollingEventResult::DidNotHandleEvent; }
> 
>     std::unique_ptr<ScrollingTreeScrollingNodeDelegateIOS> m_scrollingNodeDelegate;
> };
>diff --git a/Source/WebKit/UIProcess/RemoteLayerTree/mac/ScrollerPairMac.h b/Source/WebKit/UIProcess/RemoteLayerTree/mac/ScrollerPairMac.h
>index f0725a02a2817c458c9819167b6a25ef2050856c..b310b108d2072d0a6e24c9579e35b3d35292abda 100644
>--- a/Source/WebKit/UIProcess/RemoteLayerTree/mac/ScrollerPairMac.h
>+++ b/Source/WebKit/UIProcess/RemoteLayerTree/mac/ScrollerPairMac.h
>@@ -52,8 +52,8 @@ public:
>     ScrollerMac& verticalScroller() { return m_verticalScroller; }
>     ScrollerMac& horizontalScroller() { return m_horizontalScroller; }
> 
>-    void handleWheelEvent(const WebCore::PlatformWheelEvent&);
>-    void handleMouseEvent(const WebCore::PlatformMouseEvent&);
>+    bool handleWheelEvent(const WebCore::PlatformWheelEvent&);
>+    bool handleMouseEvent(const WebCore::PlatformMouseEvent&);
> 
>     void updateValues();
> 
>diff --git a/Source/WebKit/UIProcess/RemoteLayerTree/mac/ScrollerPairMac.mm b/Source/WebKit/UIProcess/RemoteLayerTree/mac/ScrollerPairMac.mm
>index 9b9f678905332aae654837eb0a5182e1239ba9fe..c226fc595a40940666a78a4d16be072819487e71 100644
>--- a/Source/WebKit/UIProcess/RemoteLayerTree/mac/ScrollerPairMac.mm
>+++ b/Source/WebKit/UIProcess/RemoteLayerTree/mac/ScrollerPairMac.mm
>@@ -141,7 +141,7 @@ ScrollerPairMac::~ScrollerPairMac()
>     [m_scrollerImpPair setDelegate:nil];
> }
> 
>-void ScrollerPairMac::handleWheelEvent(const WebCore::PlatformWheelEvent& event)
>+bool ScrollerPairMac::handleWheelEvent(const WebCore::PlatformWheelEvent& event)
> {
>     switch (event.phase()) {
>     case WebCore::PlatformWheelEventPhaseBegan:
>@@ -158,15 +158,19 @@ void ScrollerPairMac::handleWheelEvent(const WebCore::PlatformWheelEvent& event)
>     default:
>         break;
>     }
>+    // FIXME: this needs to return whether the event was handled.
>+    return true;
> }
> 
>-void ScrollerPairMac::handleMouseEvent(const WebCore::PlatformMouseEvent& event)
>+bool ScrollerPairMac::handleMouseEvent(const WebCore::PlatformMouseEvent& event)
> {
>     if (event.type() != WebCore::PlatformEvent::MouseMoved)
>-        return;
>+        return false;
> 
>     m_lastKnownMousePosition = event.position();
>     [m_scrollerImpPair mouseMovedInContentArea];
>+    // FIXME: this needs to return whether the event was handled.
>+    return true;
> }
> 
> void ScrollerPairMac::updateValues()
>diff --git a/Source/WebKit/UIProcess/RemoteLayerTree/mac/ScrollingTreeFrameScrollingNodeRemoteMac.cpp b/Source/WebKit/UIProcess/RemoteLayerTree/mac/ScrollingTreeFrameScrollingNodeRemoteMac.cpp
>index 90866dc4093f1b89b11814186d1f0e4d205262b3..80e8eef8c73a1f5bb34a848fd6816bb040ed7d5f 100644
>--- a/Source/WebKit/UIProcess/RemoteLayerTree/mac/ScrollingTreeFrameScrollingNodeRemoteMac.cpp
>+++ b/Source/WebKit/UIProcess/RemoteLayerTree/mac/ScrollingTreeFrameScrollingNodeRemoteMac.cpp
>@@ -32,9 +32,10 @@
> #include "ScrollerPairMac.h"
> 
> namespace WebKit {
>+using namespace WebCore;
> 
>-ScrollingTreeFrameScrollingNodeRemoteMac::ScrollingTreeFrameScrollingNodeRemoteMac(WebCore::ScrollingTree& tree, WebCore::ScrollingNodeType nodeType, WebCore::ScrollingNodeID nodeID)
>-    : WebCore::ScrollingTreeFrameScrollingNodeMac(tree, nodeType, nodeID)
>+ScrollingTreeFrameScrollingNodeRemoteMac::ScrollingTreeFrameScrollingNodeRemoteMac(ScrollingTree& tree, ScrollingNodeType nodeType, ScrollingNodeID nodeID)
>+    : ScrollingTreeFrameScrollingNodeMac(tree, nodeType, nodeID)
>     , m_scrollerPair(std::make_unique<ScrollerPairMac>(*this))
> {
> }
>@@ -43,42 +44,42 @@ ScrollingTreeFrameScrollingNodeRemoteMac::~ScrollingTreeFrameScrollingNodeRemote
> {
> }
> 
>-Ref<ScrollingTreeFrameScrollingNodeRemoteMac> ScrollingTreeFrameScrollingNodeRemoteMac::create(WebCore::ScrollingTree& tree, WebCore::ScrollingNodeType nodeType, WebCore::ScrollingNodeID nodeID)
>+Ref<ScrollingTreeFrameScrollingNodeRemoteMac> ScrollingTreeFrameScrollingNodeRemoteMac::create(ScrollingTree& tree, ScrollingNodeType nodeType, ScrollingNodeID nodeID)
> {
>     return adoptRef(*new ScrollingTreeFrameScrollingNodeRemoteMac(tree, nodeType, nodeID));
> }
> 
>-void ScrollingTreeFrameScrollingNodeRemoteMac::commitStateBeforeChildren(const WebCore::ScrollingStateNode& stateNode)
>+void ScrollingTreeFrameScrollingNodeRemoteMac::commitStateBeforeChildren(const ScrollingStateNode& stateNode)
> {
>-    WebCore::ScrollingTreeFrameScrollingNodeMac::commitStateBeforeChildren(stateNode);
>-    const auto& scrollingStateNode = downcast<WebCore::ScrollingStateFrameScrollingNode>(stateNode);
>+    ScrollingTreeFrameScrollingNodeMac::commitStateBeforeChildren(stateNode);
>+    const auto& scrollingStateNode = downcast<ScrollingStateFrameScrollingNode>(stateNode);
> 
>-    if (scrollingStateNode.hasChangedProperty(WebCore::ScrollingStateFrameScrollingNode::VerticalScrollbarLayer))
>+    if (scrollingStateNode.hasChangedProperty(ScrollingStateFrameScrollingNode::VerticalScrollbarLayer))
>         m_scrollerPair->verticalScroller().setHostLayer(scrollingStateNode.verticalScrollbarLayer());
> 
>-    if (scrollingStateNode.hasChangedProperty(WebCore::ScrollingStateFrameScrollingNode::HorizontalScrollbarLayer))
>+    if (scrollingStateNode.hasChangedProperty(ScrollingStateFrameScrollingNode::HorizontalScrollbarLayer))
>         m_scrollerPair->horizontalScroller().setHostLayer(scrollingStateNode.horizontalScrollbarLayer());
> 
>     m_scrollerPair->updateValues();
> }
> 
>-void ScrollingTreeFrameScrollingNodeRemoteMac::setScrollLayerPosition(const WebCore::FloatPoint& position, const WebCore::FloatRect& layoutViewport)
>+void ScrollingTreeFrameScrollingNodeRemoteMac::setScrollLayerPosition(const FloatPoint& position, const FloatRect& layoutViewport)
> {
>     ScrollingTreeFrameScrollingNodeMac::setScrollLayerPosition(position, layoutViewport);
> 
>     m_scrollerPair->updateValues();
> }
> 
>-void ScrollingTreeFrameScrollingNodeRemoteMac::handleWheelEvent(const WebCore::PlatformWheelEvent& wheelEvent)
>+ScrollingEventResult ScrollingTreeFrameScrollingNodeRemoteMac::handleWheelEvent(const PlatformWheelEvent& wheelEvent)
> {
>     ScrollingTreeFrameScrollingNodeMac::handleWheelEvent(wheelEvent);
> 
>-    m_scrollerPair->handleWheelEvent(wheelEvent);
>+    return m_scrollerPair->handleWheelEvent(wheelEvent) ? ScrollingEventResult::DidHandleEvent : ScrollingEventResult::DidNotHandleEvent;
> }
> 
>-void ScrollingTreeFrameScrollingNodeRemoteMac::handleMouseEvent(const WebCore::PlatformMouseEvent& mouseEvent)
>+bool ScrollingTreeFrameScrollingNodeRemoteMac::handleMouseEvent(const PlatformMouseEvent& mouseEvent)
> {
>-    m_scrollerPair->handleMouseEvent(mouseEvent);
>+    return m_scrollerPair->handleMouseEvent(mouseEvent);
> }
> 
> }
>diff --git a/Source/WebKit/UIProcess/RemoteLayerTree/mac/ScrollingTreeFrameScrollingNodeRemoteMac.h b/Source/WebKit/UIProcess/RemoteLayerTree/mac/ScrollingTreeFrameScrollingNodeRemoteMac.h
>index f2c32b53c7cc5ea35720fbc903181497ec102746..3c368474d590c3d8f1ca1fb13ee0dbc9fad2be6d 100644
>--- a/Source/WebKit/UIProcess/RemoteLayerTree/mac/ScrollingTreeFrameScrollingNodeRemoteMac.h
>+++ b/Source/WebKit/UIProcess/RemoteLayerTree/mac/ScrollingTreeFrameScrollingNodeRemoteMac.h
>@@ -38,13 +38,13 @@ public:
>     WEBCORE_EXPORT static Ref<ScrollingTreeFrameScrollingNodeRemoteMac> create(WebCore::ScrollingTree&, WebCore::ScrollingNodeType, WebCore::ScrollingNodeID);
>     virtual ~ScrollingTreeFrameScrollingNodeRemoteMac();
> 
>-    void handleMouseEvent(const WebCore::PlatformMouseEvent&);
>+    bool handleMouseEvent(const WebCore::PlatformMouseEvent&);
> 
> private:
>     ScrollingTreeFrameScrollingNodeRemoteMac(WebCore::ScrollingTree&, WebCore::ScrollingNodeType, WebCore::ScrollingNodeID);
> 
>     void commitStateBeforeChildren(const WebCore::ScrollingStateNode&) override;
>-    void handleWheelEvent(const WebCore::PlatformWheelEvent&) override;
>+    WebCore::ScrollingEventResult handleWheelEvent(const WebCore::PlatformWheelEvent&) override;
>     void setScrollLayerPosition(const WebCore::FloatPoint& position, const WebCore::FloatRect& layoutViewport) override;
> 
>     std::unique_ptr<ScrollerPairMac> m_scrollerPair;
>diff --git a/Source/WebKit/WebProcess/WebPage/EventDispatcher.cpp b/Source/WebKit/WebProcess/WebPage/EventDispatcher.cpp
>index 76c482675de8944fd992959618369e72e67e7404..691830b593c67ad33d77a0e68c547a631c5ab6d7 100644
>--- a/Source/WebKit/WebProcess/WebPage/EventDispatcher.cpp
>+++ b/Source/WebKit/WebProcess/WebPage/EventDispatcher.cpp
>@@ -122,10 +122,10 @@ void EventDispatcher::wheelEvent(uint64_t pageID, const WebWheelEvent& wheelEven
>         if (platformWheelEvent.phase() == PlatformWheelEventPhaseBegan)
>             scrollingTree->setCanRubberBandState(canRubberBandAtLeft, canRubberBandAtRight, canRubberBandAtTop, canRubberBandAtBottom);
> 
>-        ScrollingTree::EventResult result = scrollingTree->tryToHandleWheelEvent(platformWheelEvent);
>+        ScrollingEventResult result = scrollingTree->tryToHandleWheelEvent(platformWheelEvent);
> 
>-        if (result == ScrollingTree::DidHandleEvent || result == ScrollingTree::DidNotHandleEvent) {
>-            sendDidReceiveEvent(pageID, wheelEvent, result == ScrollingTree::DidHandleEvent);
>+        if (result == ScrollingEventResult::DidHandleEvent || result == ScrollingEventResult::DidNotHandleEvent) {
>+            sendDidReceiveEvent(pageID, wheelEvent, result == ScrollingEventResult::DidHandleEvent);
>             return;
>         }
>     }

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