Send early ShowPress on TapDown when page isn't scrollable/pinchable.

Source/core/page/EventHandler.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2012 Digia Plc. and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 2202 matching lines @@
     if (scroll(ScrollRight, granularity, startNode, &stopNode, wheelEvent->deltaX(), roundedIntPoint(wheelEvent->absoluteLocation())))
         wheelEvent->setDefaultHandled();
 
     if (scroll(ScrollDown, granularity, startNode, &stopNode, wheelEvent->deltaY(), roundedIntPoint(wheelEvent->absoluteLocation())))
         wheelEvent->setDefaultHandled();
 
     if (!m_latchedWheelEventNode)
         m_previousWheelScrolledNode = stopNode;
 }
 
+bool EventHandler::hasScrollableAncestor(const Node* node) const
+{
+    RenderObject* renderer = node->renderer();
+    while (node && !renderer) {
+        node = node->parentElement();
+        renderer = node ? node->renderer() : 0;
+    }
+
+    if (renderer && renderer->isBox()) {
+        RenderBox* box = toRenderBox(renderer);
+        if (box->canBeScrolledAndHasScrollableArea())
+            return true;
+    }
+
+    if (renderer && renderer->enclosingScrollableBox())
+        return true;
+
+    LocalFrame* parent = m_frame->tree().parent();
+    if (!parent)
+        return false;
+
+    return parent->eventHandler().hasScrollableAncestor(m_frame->ownerElement());
+}
+
 bool EventHandler::handleGestureShowPress()
 {
     m_lastShowPressTimestamp = WTF::currentTime();
 
     FrameView* view = m_frame->view();
     if (!view)
         return false;
     if (ScrollAnimator* scrollAnimator = view->existingScrollAnimator())
         scrollAnimator->cancelAnimations();
     const FrameView::ScrollableAreaSet* areas = view->scrollableAreas();
     if (!areas)
         return false;
     for (FrameView::ScrollableAreaSet::const_iterator it = areas->begin(); it != areas->end(); ++it) {
         ScrollableArea* sa = *it;
         ScrollAnimator* animator = sa->scrollAnimator();
         if (animator)
             animator->cancelAnimations();
     }
     return false;
 }
 
 bool EventHandler::handleGestureEvent(const PlatformGestureEvent& gestureEvent)
 {
     IntPoint adjustedPoint = gestureEvent.position();
-    RefPtr<LocalFrame> subframe = nullptr;
-    switch (gestureEvent.type()) {
-    case PlatformEvent::GestureScrollBegin:
-    case PlatformEvent::GestureScrollUpdate:
-    case PlatformEvent::GestureScrollUpdateWithoutPropagation:
-    case PlatformEvent::GestureScrollEnd:
-    case PlatformEvent::GestureFlingStart:
-        // Handle directly in main frame
-        break;
-
-    case PlatformEvent::GestureTap:
-    case PlatformEvent::GestureTapUnconfirmed:
-    case PlatformEvent::GestureTapDown:
-    case PlatformEvent::GestureShowPress:
-    case PlatformEvent::GestureTapDownCancel:
-    case PlatformEvent::GestureTwoFingerTap:
-    case PlatformEvent::GestureLongPress:
-    case PlatformEvent::GestureLongTap:
-    case PlatformEvent::GesturePinchBegin:
-    case PlatformEvent::GesturePinchEnd:
-    case PlatformEvent::GesturePinchUpdate:
-        adjustGesturePosition(gestureEvent, adjustedPoint);
-        subframe = getSubFrameForGestureEvent(adjustedPoint, gestureEvent);
-        if (subframe)
-            return subframe->eventHandler().handleGestureEvent(gestureEvent);
-        break;
-
-    default:
-        ASSERT_NOT_REACHED();
-    }
+    RefPtr<LocalFrame> subframe = frameForGestureEvent(gestureEvent, adjustedPoint);
+    if (subframe != m_frame)
+        return subframe->eventHandler().handleGestureEvent(gestureEvent);
 
     Node* eventTarget = 0;
     Scrollbar* scrollbar = 0;
     if (gestureEvent.type() == PlatformEvent::GestureScrollEnd
         || gestureEvent.type() == PlatformEvent::GestureScrollUpdate
         || gestureEvent.type() == PlatformEvent::GestureScrollUpdateWithoutPropagation
         || gestureEvent.type() == PlatformEvent::GestureFlingStart) {
         scrollbar = m_scrollbarHandlingScrollGesture.get();
         eventTarget = m_scrollGestureHandlingNode.get();
     }
@@ skipping 356 matching lines @@
         gestureEvent.shiftKey(), gestureEvent.ctrlKey(), gestureEvent.altKey(), gestureEvent.metaKey());
     syntheticWheelEvent.setHasPreciseScrollingDeltas(true);
 
     bool scrolledFrame = view->wheelEvent(syntheticWheelEvent);
     if (scrolledFrame)
         setFrameWasScrolledByUser();
 
     return scrolledFrame;
 }
 
-LocalFrame* EventHandler::getSubFrameForGestureEvent(const IntPoint& touchAdjustedPoint, const PlatformGestureEvent& gestureEvent)
+LocalFrame* EventHandler::frameForGestureEvent(const PlatformGestureEvent& gestureEvent, IntPoint& adjustedPoint)
 {
-    PlatformMouseEvent mouseDown(touchAdjustedPoint, gestureEvent.globalPosition(), LeftButton, PlatformEvent::MousePressed, 1,
-        gestureEvent.shiftKey(), gestureEvent.ctrlKey(), gestureEvent.altKey(), gestureEvent.metaKey(), gestureEvent.timestamp());
-    HitTestRequest request(HitTestRequest::ReadOnly);
-    MouseEventWithHitTestResults mev = prepareMouseEvent(request, mouseDown);
-    return subframeForHitTestResult(mev);
+    switch (gestureEvent.type()) {
+    case PlatformEvent::GestureScrollBegin:
+    case PlatformEvent::GestureScrollUpdate:
+    case PlatformEvent::GestureScrollUpdateWithoutPropagation:
+    case PlatformEvent::GestureScrollEnd:
+    case PlatformEvent::GestureFlingStart:
+        // Handle in current frame
+        break;
+
+    case PlatformEvent::GestureTap:
+    case PlatformEvent::GestureTapUnconfirmed:
+    case PlatformEvent::GestureTapDown:
+    case PlatformEvent::GestureShowPress:
+    case PlatformEvent::GestureTapDownCancel:
+    case PlatformEvent::GestureTwoFingerTap:
+    case PlatformEvent::GestureLongPress:
+    case PlatformEvent::GestureLongTap:
+    case PlatformEvent::GesturePinchBegin:

[Rick Byers, 2014/03/13 01:40:06]

I know you're just moving code around here, but this division feels odd to me. 
Ideally we'd have a comment saying how we decided which should be handled in the
current frame and which need adjustment down to the subframe.  Eg. pinch should
probably be handled in the same way as scroll (although I don't think we
actually receive pinch events in WebCore).

[Zeeshan Qureshi, 2014/03/24 21:37:43]

I'm not quite sure why, I was hoping to dig into it when continuing work on
http://crrev.com/130433009 as it will require modifying a good chunk of
EventHandler::handleGestureEvent().

[Rick Byers, 2014/03/25 19:46:47]

Ok, deferring this to a future CL is fine.  Thanks.

+    case PlatformEvent::GesturePinchEnd:
+    case PlatformEvent::GesturePinchUpdate: {
+        adjustGesturePosition(gestureEvent, adjustedPoint);
+        PlatformMouseEvent mouseDown(adjustedPoint, gestureEvent.globalPosition(), LeftButton, PlatformEvent::MousePressed, 1,
+            gestureEvent.shiftKey(), gestureEvent.ctrlKey(), gestureEvent.altKey(), gestureEvent.metaKey(), gestureEvent.timestamp());
+        HitTestRequest request(HitTestRequest::ReadOnly);
+        MouseEventWithHitTestResults mev = prepareMouseEvent(request, mouseDown);
+        RefPtr<LocalFrame> subframe = subframeForHitTestResult(mev);
+        if (subframe)
+            return subframe->eventHandler().frameForGestureEvent(gestureEvent, adjustedPoint);
+        break;
+    }
+
+    default:
+        ASSERT_NOT_REACHED();
+    }
+
+    return m_frame;
 }
 
 void EventHandler::clearGestureScrollNodes()
 {
     m_scrollGestureHandlingNode = nullptr;
     m_previousGestureScrolledNode = nullptr;
 }
 
 bool EventHandler::isScrollbarHandlingGestures() const
 {
@@ skipping 1345 matching lines @@
 unsigned EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return PlatformEvent::CtrlKey | PlatformEvent::AltKey;
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace WebCore