OverscrollGlow for mainThread-{BLINK CHANGES}

Source/core/page/EventHandler.cpp

Index: Source/core/page/EventHandler.cpp
diff --git a/Source/core/page/EventHandler.cpp b/Source/core/page/EventHandler.cpp
index fc8bd5cc5ebfae20dc2734db25ab32dff0425a14..ade9a87f375836e3c82dc7cc935699bd24ca3092 100644
--- a/Source/core/page/EventHandler.cpp
+++ b/Source/core/page/EventHandler.cpp
@@ -233,6 +233,8 @@ EventHandler::EventHandler(LocalFrame* frame)
     , m_eventHandlerWillResetCapturingMouseEventsNode(0)
     , m_clickCount(0)
     , m_shouldOnlyFireDragOverEvent(false)
+    , m_unusedDelta(FloatSize())
+    , m_accumulatedRootOverscroll(FloatSize())
     , m_mousePositionIsUnknown(true)
     , m_mouseDownTimestamp(0)
     , m_widgetIsLatched(false)
@@ -924,10 +926,10 @@ void EventHandler::stopAutoscroll()
         controller->stopAutoscroll();
 }
 
-bool EventHandler::scroll(ScrollDirection direction, ScrollGranularity granularity, Node* startNode, Node** stopNode, float delta, IntPoint absolutePoint)
+ScrollResultOneDimensional EventHandler::scroll(ScrollDirection direction, ScrollGranularity granularity, Node* startNode, Node** stopNode, float delta, IntPoint absolutePoint)
 {
     if (!delta)
-        return false;
+        return ScrollResultOneDimensional(false);
 
     Node* node = startNode;
 
@@ -938,7 +940,7 @@ bool EventHandler::scroll(ScrollDirection direction, ScrollGranularity granulari
         node = m_mousePressNode.get();
 
     if (!node || !node->layoutObject())
-        return false;
+        return ScrollResultOneDimensional(false, delta);
 
     LayoutBox* curBox = node->layoutObject()->enclosingBox();
     while (curBox && !curBox->isLayoutView()) {
@@ -947,20 +949,21 @@ bool EventHandler::scroll(ScrollDirection direction, ScrollGranularity granulari
 
         // If we're at the stopNode, we should try to scroll it but we shouldn't bubble past it
         bool shouldStopBubbling = stopNode && *stopNode && curBox->node() == *stopNode;
-        bool didScroll = curBox->scroll(physicalDirection, granularity, delta);
+        ScrollResultOneDimensional result = curBox->scroll(physicalDirection, granularity, delta);
 
-        if (didScroll && stopNode)
+        if (result.didScroll && stopNode)
             *stopNode = curBox->node();
 
-        if (didScroll || shouldStopBubbling) {
+        if (result.didScroll || shouldStopBubbling) {
             setFrameWasScrolledByUser();
-            return true;
+            result.didScroll = true;
+            return result;
         }
 
         curBox = curBox->containingBlock();
     }
 
-    return false;
+    return ScrollResultOneDimensional(false, delta);
 }
 
 void EventHandler::customizedScroll(const Node& startNode, ScrollState& scrollState)
@@ -980,11 +983,11 @@ bool EventHandler::bubblingScroll(ScrollDirection direction, ScrollGranularity g
     // here because of an onLoad event, in which case the final layout hasn't been performed yet.
     m_frame->document()->updateLayoutIgnorePendingStylesheets();
     // FIXME: enable scroll customization in this case. See crbug.com/410974.
-    if (scroll(direction, granularity, startingNode))
+    if (scroll(direction, granularity, startingNode).didScroll)
         return true;
     LocalFrame* frame = m_frame;
     FrameView* view = frame->view();
-    if (view && view->scroll(direction, granularity)) {
+    if (view && view->scroll(direction, granularity).didScroll) {
         setFrameWasScrolledByUser();
         return true;
     }
@@ -2200,11 +2203,11 @@ void EventHandler::defaultWheelEventHandler(Node* startNode, WheelEvent* wheelEv
 
     // FIXME: enable scroll customization in this case. See crbug.com/410974.
     if (wheelEvent->railsMode() != Event::RailsModeVertical
-        && scroll(ScrollRight, granularity, startNode, &stopNode, wheelEvent->deltaX(), absolutePosition))
+        && scroll(ScrollRight, granularity, startNode, &stopNode, wheelEvent->deltaX(), absolutePosition).didScroll)
         wheelEvent->setDefaultHandled();
 
     if (wheelEvent->railsMode() != Event::RailsModeHorizontal
-        && scroll(ScrollDown, granularity, startNode, &stopNode, wheelEvent->deltaY(), absolutePosition))
+        && scroll(ScrollDown, granularity, startNode, &stopNode, wheelEvent->deltaY(), absolutePosition).didScroll)
         wheelEvent->setDefaultHandled();
 
     if (!m_latchedWheelEventNode)
@@ -2705,14 +2708,27 @@ bool EventHandler::handleGestureScrollUpdate(const PlatformGestureEvent& gesture
 
             // First try to scroll the closest scrollable LayoutBox ancestor of |node|.
             ScrollGranularity granularity = ScrollByPrecisePixel;
-            bool horizontalScroll = scroll(ScrollLeft, granularity, node, &stopNode, delta.width());
+            m_unusedDelta = FloatSize();
+            ScrollResultOneDimensional result = scroll(ScrollLeft, granularity, node, &stopNode, delta.width());
+            bool horizontalScroll = result.didScroll;
             if (!gestureEvent.preventPropagation())
                 stopNode = nullptr;
-            bool verticalScroll = scroll(ScrollUp, granularity, node, &stopNode, delta.height());
+            result = scroll(ScrollUp, granularity, node, &stopNode, delta.height());
+            bool verticalScroll = result.didScroll;
             scrolled = horizontalScroll || verticalScroll;
 
             if (gestureEvent.preventPropagation())
                 m_previousGestureScrolledNode = stopNode;
+
+            if (horizontalScroll) {
+                m_accumulatedRootOverscroll.setWidth(0);
+                m_unusedDelta.setWidth(0);
+            }
+
+            if (verticalScroll) {
+                m_accumulatedRootOverscroll.setHeight(0);
+                m_unusedDelta.setHeight(0);
+            }
         }
         if (scrolled) {
             setFrameWasScrolledByUser();
@@ -2724,7 +2740,17 @@ bool EventHandler::handleGestureScrollUpdate(const PlatformGestureEvent& gesture
         return false;
 
     // Try to scroll the frame view.
-    if (m_frame->applyScrollDelta(delta, false)) {
+    ScrollResult resultScrollDelta = m_frame->applyScrollDelta(delta, false);
+    m_unusedDelta.setWidth(resultScrollDelta.unusedScrollDeltaX);
+    m_unusedDelta.setHeight(resultScrollDelta.unusedScrollDeltaY);
+    if (m_frame->isMainFrame() && m_unusedDelta != FloatSize()) {
+        m_accumulatedRootOverscroll += m_unusedDelta;
+        FloatPoint position = FloatPoint(gestureEvent.position().x(), gestureEvent.position().y());
+        FloatSize velocity = FloatSize(gestureEvent.velocityX(), gestureEvent.velocityY());
+        m_frame->chromeClient().didOverscroll(m_unusedDelta, m_accumulatedRootOverscroll, position, velocity);
+    }
+
+    if (resultScrollDelta.didScroll) {
         setFrameWasScrolledByUser();
         return true;
     }
@@ -2738,6 +2764,8 @@ void EventHandler::clearGestureScrollNodes()
     m_previousGestureScrolledNode = nullptr;
     m_deltaConsumedForScrollSequence = false;
     m_currentScrollChain.clear();
+    m_accumulatedRootOverscroll = FloatSize();
+    m_unusedDelta = FloatSize();
 }
 
 bool EventHandler::isScrollbarHandlingGestures() const
@@ -3639,7 +3667,7 @@ void EventHandler::defaultSpaceEventHandler(KeyboardEvent* event)
 
     ScrollDirection direction = event->shiftKey() ? ScrollBlockDirectionBackward : ScrollBlockDirectionForward;
     // FIXME: enable scroll customization in this case. See crbug.com/410974.
-    if (scroll(direction, ScrollByPage)) {
+    if (scroll(direction, ScrollByPage).didScroll) {
         event->setDefaultHandled();
         return;
     }
@@ -3648,7 +3676,7 @@ void EventHandler::defaultSpaceEventHandler(KeyboardEvent* event)
     if (!view)
         return;
 
-    if (view->scroll(direction, ScrollByPage))
+    if (view->scroll(direction, ScrollByPage).didScroll)
         event->setDefaultHandled();
 }