Clarify the role of "mainFrameCanRubberBand" at the ScrollingTree level

https://bugs.webkit.org/show_bug.cgi?id=268697
rdar://122242780

Reviewed by Tim Horton.

ScrollingTree::mainFrameCanRubberBandOnSide() is easy to mis-use: it doesn't mean that rubber-banding
will happen, only that the client (Safari, Mail etc) has allowed rubber-banding to happen on this side.
So rename it accordingly.

This make it clear that `ScrollingTreeScrollingNodeDelegateMac::shouldRubberBandOnSide()` isn't
using it correctly. Future changes will fix that.

* Source/WebCore/page/scrolling/ScrollingTree.cpp:
(WebCore::ScrollingTree::setClientAllowedMainFrameRubberBandableEdges):
(WebCore::ScrollingTree::clientAllowsMainFrameRubberBandingOnSide):
(WebCore::ScrollingTree::willWheelEventStartSwipeGesture):
(WebCore::ScrollingTree::setMainFrameCanRubberBand): Deleted.
(WebCore::ScrollingTree::mainFrameCanRubberBandOnSide): Deleted.
* Source/WebCore/page/scrolling/ScrollingTree.h:
* Source/WebCore/page/scrolling/mac/ScrollingTreeScrollingNodeDelegateMac.mm:
(WebCore::ScrollingTreeScrollingNodeDelegateMac::shouldRubberBandOnSide const):
* Source/WebKit/UIProcess/RemoteLayerTree/RemoteScrollingCoordinatorProxy.cpp:
(WebKit::RemoteScrollingCoordinatorProxy::handleWheelEvent):
* Source/WebKit/UIProcess/RemoteLayerTree/mac/RemoteLayerTreeEventDispatcher.cpp:
(WebKit::RemoteLayerTreeEventDispatcher::determineWheelEventProcessing):
* Source/WebKit/WebProcess/WebPage/EventDispatcher.cpp:
(WebKit::EventDispatcher::internalWheelEvent):

Canonical link: https://commits.webkit.org/274061@main

Source/WebCore/page/scrolling/ScrollingTree.cpp

@@ -783,17 +783,17 @@ void ScrollingTree::setMainFramePinnedState(RectEdges<bool> edgePinningState)
     m_swipeState.mainFramePinnedState = edgePinningState;
 }
 
-void ScrollingTree::setMainFrameCanRubberBand(RectEdges<bool> canRubberBand)
+void ScrollingTree::setClientAllowedMainFrameRubberBandableEdges(RectEdges<bool> clientAllowedRubberBandableEdges)
 {
     Locker locker { m_swipeStateLock };
 
-    m_swipeState.canRubberBand = canRubberBand;
+    m_swipeState.clientAllowedRubberBandableEdges = clientAllowedRubberBandableEdges;
 }
 
-bool ScrollingTree::mainFrameCanRubberBandOnSide(BoxSide side)
+bool ScrollingTree::clientAllowsMainFrameRubberBandingOnSide(BoxSide side)
 {
     Locker locker { m_swipeStateLock };
-    return m_swipeState.canRubberBand.at(side);
+    return m_swipeState.clientAllowedRubberBandableEdges.at(side);
 }
 
 void ScrollingTree::addPendingScrollUpdate(ScrollUpdate&& update)
@@ -843,13 +843,13 @@ bool ScrollingTree::willWheelEventStartSwipeGesture(const PlatformWheelEvent& wh
 
     Locker locker { m_swipeStateLock };
 
-    if (wheelEvent.deltaX() > 0 && m_swipeState.mainFramePinnedState.left() && !m_swipeState.canRubberBand.left())
+    if (wheelEvent.deltaX() > 0 && m_swipeState.mainFramePinnedState.left() && !m_swipeState.clientAllowedRubberBandableEdges.left())
         return true;
-    if (wheelEvent.deltaX() < 0 && m_swipeState.mainFramePinnedState.right() && !m_swipeState.canRubberBand.right())
+    if (wheelEvent.deltaX() < 0 && m_swipeState.mainFramePinnedState.right() && !m_swipeState.clientAllowedRubberBandableEdges.right())
         return true;
-    if (wheelEvent.deltaY() > 0 && m_swipeState.mainFramePinnedState.top() && !m_swipeState.canRubberBand.top())
+    if (wheelEvent.deltaY() > 0 && m_swipeState.mainFramePinnedState.top() && !m_swipeState.clientAllowedRubberBandableEdges.top())
         return true;
-    if (wheelEvent.deltaY() < 0 && m_swipeState.mainFramePinnedState.bottom() && !m_swipeState.canRubberBand.bottom())
+    if (wheelEvent.deltaY() < 0 && m_swipeState.mainFramePinnedState.bottom() && !m_swipeState.clientAllowedRubberBandableEdges.bottom())
         return true;
 
     return false;

Source/WebCore/page/scrolling/ScrollingTree.h

@@ -166,8 +166,8 @@ class ScrollingTree : public ThreadSafeRefCounted<ScrollingTree> {
     void setMainFramePinnedState(RectEdges<bool>);
 
     // Can be called from any thread. Will update what edges allow rubber-banding.
-    WEBCORE_EXPORT void setMainFrameCanRubberBand(RectEdges<bool>);
-    bool mainFrameCanRubberBandOnSide(BoxSide);
+    WEBCORE_EXPORT void setClientAllowedMainFrameRubberBandableEdges(RectEdges<bool>);
+    bool clientAllowsMainFrameRubberBandingOnSide(BoxSide);
 
     bool isHandlingProgrammaticScroll() const { return m_isHandlingProgrammaticScroll; }
     void setIsHandlingProgrammaticScroll(bool isHandlingProgrammaticScroll) { m_isHandlingProgrammaticScroll = isHandlingProgrammaticScroll; }
@@ -320,7 +320,7 @@ class ScrollingTree : public ThreadSafeRefCounted<ScrollingTree> {
     TreeState m_treeState WTF_GUARDED_BY_LOCK(m_treeStateLock);
 
     struct SwipeState {
-        RectEdges<bool> canRubberBand  { true, true, true, true };
+        RectEdges<bool> clientAllowedRubberBandableEdges  { true, true, true, true };
         RectEdges<bool> mainFramePinnedState { true, true, true, true };
         ScrollPinningBehavior scrollPinningBehavior { ScrollPinningBehavior::DoNotPin };
     };

Source/WebCore/page/scrolling/mac/ScrollingTreeScrollingNodeDelegateMac.mm

@@ -277,7 +277,7 @@
 bool ScrollingTreeScrollingNodeDelegateMac::shouldRubberBandOnSide(BoxSide side) const
 {
     if (scrollingNode().isRootNode())
-        return scrollingTree().mainFrameCanRubberBandOnSide(side);
+        return scrollingTree().clientAllowsMainFrameRubberBandingOnSide(side);
 
     switch (side) {
     case BoxSide::Top:

Source/WebKit/UIProcess/RemoteLayerTree/RemoteScrollingCoordinatorProxy.cpp

@@ -117,7 +117,7 @@ void RemoteScrollingCoordinatorProxy::handleWheelEvent(const WebWheelEvent& whee
     // Replicate the hack in EventDispatcher::internalWheelEvent(). We could pass rubberBandableEdges all the way through the
     // WebProcess and back via the ScrollingTree, but we only ever need to consult it here.
     if (platformWheelEvent.phase() == PlatformWheelEventPhase::Began)
-        m_scrollingTree->setMainFrameCanRubberBand(rubberBandableEdges);
+        m_scrollingTree->setClientAllowedMainFrameRubberBandableEdges(rubberBandableEdges);
 
     auto processingSteps = m_scrollingTree->determineWheelEventProcessing(platformWheelEvent);
     if (!processingSteps.contains(WheelEventProcessingSteps::AsyncScrolling)) {

Source/WebKit/UIProcess/RemoteLayerTree/mac/RemoteLayerTreeEventDispatcher.cpp

@@ -255,7 +255,7 @@ OptionSet<WheelEventProcessingSteps> RemoteLayerTreeEventDispatcher::determineWh
     // Replicate the hack in EventDispatcher::internalWheelEvent(). We could pass rubberBandableEdges all the way through the
     // WebProcess and back via the ScrollingTree, but we only ever need to consult it here.
     if (wheelEvent.phase() == PlatformWheelEventPhase::Began)
-        scrollingTree->setMainFrameCanRubberBand(rubberBandableEdges);
+        scrollingTree->setClientAllowedMainFrameRubberBandableEdges(rubberBandableEdges);
 
     return scrollingTree->determineWheelEventProcessing(wheelEvent);
 }

Source/WebKit/WebProcess/WebPage/EventDispatcher.cpp

@@ -141,7 +141,7 @@ void EventDispatcher::internalWheelEvent(PageIdentifier pageID, const WebWheelEv
         // scrolling tree can be notified.
         // We only need to do this at the beginning of the gesture.
         if (platformWheelEvent.phase() == PlatformWheelEventPhase::Began)
-            scrollingTree->setMainFrameCanRubberBand(rubberBandableEdges);
+            scrollingTree->setClientAllowedMainFrameRubberBandableEdges(rubberBandableEdges);
 
         auto processingSteps = scrollingTree->determineWheelEventProcessing(platformWheelEvent);
         bool useMainThreadForScrolling = processingSteps.contains(WheelEventProcessingSteps::SynchronousScrolling);