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 39 matching lines @@
 #include "core/events/MouseEvent.h"
 #include "core/events/TextEvent.h"
 #include "core/events/ThreadLocalEventNames.h"
 #include "core/events/TouchEvent.h"
 #include "core/events/WheelEvent.h"
 #include "core/fetch/ImageResource.h"
 #include "core/html/HTMLDialogElement.h"
 #include "core/html/HTMLFrameElementBase.h"
 #include "core/html/HTMLFrameSetElement.h"
 #include "core/html/HTMLInputElement.h"
+#include "core/loader/EmptyClients.h"

[Rick Byers, 2014/02/14 21:27:53]

why do you need this new include?  Seems odd...

 #include "core/loader/FrameLoader.h"
 #include "core/loader/FrameLoaderClient.h"
 #include "core/page/AutoscrollController.h"
 #include "core/page/BackForwardClient.h"
 #include "core/page/Chrome.h"
 #include "core/page/ChromeClient.h"
 #include "core/page/DragController.h"
 #include "core/page/DragState.h"
 #include "core/page/EditorClient.h"
 #include "core/page/FocusController.h"
@@ skipping 221 matching lines @@
     , m_originatingTouchPointTargetKey(0)
     , m_touchPressed(false)
     , m_scrollGestureHandlingNode(0)
     , m_lastHitTestResultOverWidget(false)
     , m_maxMouseMovedDuration(0)
     , m_baseEventType(PlatformEvent::NoType)
     , m_didStartDrag(false)
     , m_longTapShouldInvokeContextMenu(false)
     , m_syntheticPageScaleFactor(0)
     , m_activeIntervalTimer(this, &EventHandler::activeIntervalTimerFired)
-    , m_lastShowPressTimestamp(0)
+    , m_lastActiveTimestamp(0)
+    , m_tapDownTriggeredActive(false)
 {
 }
 
 EventHandler::~EventHandler()
 {
     ASSERT(!m_fakeMouseMoveEventTimer.isActive());
 }
 
 DragState& EventHandler::dragState()
 {
@@ skipping 35 matching lines @@
     m_scrollGestureHandlingNode = 0;
     m_lastHitTestResultOverWidget = false;
     m_previousGestureScrolledNode = 0;
     m_scrollbarHandlingScrollGesture = 0;
     m_maxMouseMovedDuration = 0;
     m_baseEventType = PlatformEvent::NoType;
     m_didStartDrag = false;
     m_touchPressed = false;
     m_mouseDownMayStartSelect = false;
     m_mouseDownMayStartDrag = false;
-    m_lastShowPressTimestamp = 0;
+    m_lastActiveTimestamp = 0;
     m_lastDeferredTapElement = 0;
+    m_tapDownTriggeredActive = false;
 }
 
 void EventHandler::nodeWillBeRemoved(Node& nodeToBeRemoved)
 {
     if (!nodeToBeRemoved.containsIncludingShadowDOM(m_clickNode.get()))
         return;
     if (nodeToBeRemoved.isInShadowTree()) {
         m_clickNode = nodeToBeRemoved.parentOrShadowHostNode();
     } else {
         // We don't dispatch click events if the mousedown node is removed
@@ skipping 1846 matching lines @@
 
     if (scroll(ScrollDown, granularity, startNode, &stopNode, wheelEvent->deltaY(), roundedIntPoint(wheelEvent->absoluteLocation())))
         wheelEvent->setDefaultHandled();
 
     if (!m_latchedWheelEventNode)
         m_previousWheelScrolledNode = stopNode;
 }
 
 bool EventHandler::handleGestureShowPress()
 {
-    m_lastShowPressTimestamp = WTF::currentTime();
+    if (!m_tapDownTriggeredActive)
+        m_lastActiveTimestamp = 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) {
@@ skipping 11 matching lines @@
     RefPtr<Frame> subframe = 0;
     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::GestureTapDown:
+        m_tapDownTriggeredActive = false;
     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);
@@ skipping 11 matching lines @@
         || gestureEvent.type() == PlatformEvent::GestureScrollUpdate
         || gestureEvent.type() == PlatformEvent::GestureScrollUpdateWithoutPropagation
         || gestureEvent.type() == PlatformEvent::GestureFlingStart) {
         scrollbar = m_scrollbarHandlingScrollGesture.get();
         eventTarget = m_scrollGestureHandlingNode.get();
     }
 
     HitTestRequest::HitTestRequestType hitType = HitTestRequest::TouchEvent;
     double activeInterval = 0;
     bool shouldKeepActiveForMinInterval = false;
-    if (gestureEvent.type() == PlatformEvent::GestureShowPress
-        || gestureEvent.type() == PlatformEvent::GestureTapUnconfirmed) {
+    if (gestureEvent.type() == PlatformEvent::GestureTapDown) {
+        Page* page = m_frame->page();

[bokan, 2014/02/18 19:59:57]

Nit: I think this is involved enough that you could factor this out into a
helper method.

+        Frame* mainFrame = page ? page->mainFrame() : 0;
+        FrameView* frameView = mainFrame ? mainFrame->view() : 0;
+        ChromeClient& chromeClient = mainFrame ? mainFrame->chromeClient() : *new EmptyChromeClient();

[Rick Byers, 2014/02/14 21:27:53]

we should probably avoid creating a fake client (just use a different branch
instead).  Also you'd want stack allocation not heap allocation to avoid
leaking.

+
+        // Only activate on TapDown if page isn't scrollable or pinchable and
+        // this isn't the start of a scroll.
+        if (frameView && !frameView->isScrollable() && chromeClient.minimumPageScaleFactor() == chromeClient.maximumPageScaleFactor()) {
+            IntPoint hitTestPoint = m_frame->view()->windowToContents(adjustedPoint);
+            HitTestResult result = hitTestResultAtPoint(hitTestPoint, HitTestRequest::TouchEvent | HitTestRequest::ReadOnly  | HitTestRequest::AllowFrameScrollbars);
+            RenderObject* renderer = result.innerElement()->renderer();
+
+            // If no ancestor is scrollable then this couldn't possibly be the start of a scroll.
+            bool shouldTapDownTriggerActive = true;
+            for (RenderLayer* parent = renderer ? renderer->enclosingLayer() : 0; parent && shouldTapDownTriggerActive; parent = parent->parent()) {

[bokan, 2014/02/18 19:59:57]

I think this will break if your renderer is contained in an iframe; there may be
a scrollable frame or renderer up the hierarchy, but parent() will end at the
RenderView for the frame.

I think you should walk up ScrollableArea::enclosingScrollableArea, but they're
filled with FIXMEs to implement this case I just mentioned. See 
EventHandler::bubblingScroll for how to do this. If you're looking for brownie
points, implement those ScrollableArea FIXMEs and use those. 

+                if (parent->scrollsOverflow())
+                    shouldTapDownTriggerActive = false;

[bokan, 2014/02/18 19:59:57]

You can 'break' out of the loop here 

+            }
+
+            if (shouldTapDownTriggerActive) {
+                m_tapDownTriggeredActive = true;
+                hitType |= HitTestRequest::Active;
+            }
+        }
+    } else if (gestureEvent.type() == PlatformEvent::GestureShowPress && !m_tapDownTriggeredActive) {
+        hitType |= HitTestRequest::Active;
+    } else if (gestureEvent.type() == PlatformEvent::GestureTapUnconfirmed) {
         hitType |= HitTestRequest::Active;
     } else if (gestureEvent.type() == PlatformEvent::GestureTapDownCancel) {
         hitType |= HitTestRequest::Release;
         // A TapDownCancel received when no element is active shouldn't really be changing hover state.
         if (!m_frame->document()->activeHoverElement())
             hitType |= HitTestRequest::ReadOnly;
     } else if (gestureEvent.type() == PlatformEvent::GestureTap) {
         hitType |= HitTestRequest::Release;
         // If the Tap is received very shortly after ShowPress, we want to delay clearing
         // of the active state so that it's visible to the user for at least one frame.
-        activeInterval = WTF::currentTime() - m_lastShowPressTimestamp;
-        shouldKeepActiveForMinInterval = m_lastShowPressTimestamp && activeInterval < minimumActiveInterval;
+        activeInterval = WTF::currentTime() - m_lastActiveTimestamp;
+        shouldKeepActiveForMinInterval = m_lastActiveTimestamp && activeInterval < minimumActiveInterval;
         if (shouldKeepActiveForMinInterval)
             hitType |= HitTestRequest::ReadOnly;
     }
     else
         hitType |= HitTestRequest::Active | HitTestRequest::ReadOnly;
 
     if ((!scrollbar && !eventTarget) || !(hitType & HitTestRequest::ReadOnly)) {
         IntPoint hitTestPoint = m_frame->view()->windowToContents(adjustedPoint);
         HitTestResult result = hitTestResultAtPoint(hitTestPoint, hitType | HitTestRequest::AllowFrameScrollbars);
 
@@ skipping 56 matching lines @@
         return handleGestureTap(gestureEvent, adjustedPoint);
     case PlatformEvent::GestureShowPress:
         return handleGestureShowPress();
     case PlatformEvent::GestureLongPress:
         return handleGestureLongPress(gestureEvent, adjustedPoint);
     case PlatformEvent::GestureLongTap:
         return handleGestureLongTap(gestureEvent, adjustedPoint);
     case PlatformEvent::GestureTwoFingerTap:
         return handleGestureTwoFingerTap(gestureEvent, adjustedPoint);
     case PlatformEvent::GestureTapDown:
+        if (m_tapDownTriggeredActive)
+            m_lastActiveTimestamp = WTF::currentTime();
     case PlatformEvent::GesturePinchBegin:
     case PlatformEvent::GesturePinchEnd:
     case PlatformEvent::GesturePinchUpdate:
     case PlatformEvent::GestureTapDownCancel:
     case PlatformEvent::GestureTapUnconfirmed:
     case PlatformEvent::GestureFlingStart:
         break;
     default:
         ASSERT_NOT_REACHED();
     }
@@ skipping 1623 matching lines @@
 unsigned EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return PlatformEvent::CtrlKey | PlatformEvent::AltKey;
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace WebCore