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

Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 364 matching lines @@
     , m_fullscreenController(FullscreenController::create(this))
     , m_showFPSCounter(false)
     , m_showPaintRects(false)
     , m_showDebugBorders(false)
     , m_continuousPaintingEnabled(false)
     , m_showScrollBottleneckRects(false)
     , m_baseBackgroundColor(Color::white)
     , m_backgroundColorOverride(Color::transparent)
     , m_zoomFactorOverride(0)
     , m_helperPluginCloseTimer(this, &WebViewImpl::closePendingHelperPlugins)
+    , m_gestureTapDownTriggeredActive(false)
 {
     Page::PageClients pageClients;
     pageClients.chromeClient = &m_chromeClientImpl;
     pageClients.contextMenuClient = &m_contextMenuClientImpl;
     pageClients.editorClient = &m_editorClientImpl;
     pageClients.dragClient = &m_dragClientImpl;
     pageClients.inspectorClient = &m_inspectorClientImpl;
     pageClients.backForwardClient = &m_backForwardClientImpl;
     pageClients.spellCheckerClient = &m_spellCheckerClientImpl;
     pageClients.storageClient = &m_storageClientImpl;
@@ skipping 237 matching lines @@
     default:
         break;
     }
 
     PlatformGestureEventBuilder platformEvent(mainFrameImpl()->frameView(), event);
 
     // Handle link highlighting outside the main switch to avoid getting lost in the
     // complicated set of cases handled below.
     switch (event.type) {
     case WebInputEvent::GestureShowPress:
+        // Skip if already seen a ShowPress triggered by TapDown.
+        if (m_gestureTapDownTriggeredActive)
+            return false;
+
         // Queue a highlight animation, then hand off to regular handler.
         if (settingsImpl()->gestureTapHighlightEnabled())
             enableTapHighlightAtPoint(platformEvent);
         break;
     case WebInputEvent::GestureTapCancel:
     case WebInputEvent::GestureTap:
     case WebInputEvent::GestureLongPress:
         for (size_t i = 0; i < m_linkHighlights.size(); ++i)
             m_linkHighlights[i]->startHighlightAnimationIfNeeded();
         break;
@@ skipping 74 matching lines @@
     }
     case WebInputEvent::GestureDoubleTap:
         if (m_webSettings->doubleTapToZoomEnabled() && minimumPageScaleFactor() != maximumPageScaleFactor()) {
             m_client->cancelScheduledContentIntents();
             animateDoubleTapZoom(platformEvent.position());
         }
         // GestureDoubleTap is currently only used by Android for zooming. For WebCore,
         // GestureTap with tap count = 2 is used instead. So we drop GestureDoubleTap here.
         eventSwallowed = true;
         break;
+    case WebInputEvent::GestureTapDown:
+        m_gestureTapDownTriggeredActive = false;
+        eventSwallowed = mainFrameImpl()->frame()->eventHandler().handleGestureEvent(platformEvent);
+        break;
     case WebInputEvent::GestureScrollBegin:
     case WebInputEvent::GesturePinchBegin:
         m_client->cancelScheduledContentIntents();
-    case WebInputEvent::GestureTapDown:
     case WebInputEvent::GestureScrollEnd:
     case WebInputEvent::GestureScrollUpdate:
     case WebInputEvent::GestureScrollUpdateWithoutPropagation:
     case WebInputEvent::GestureTapCancel:
     case WebInputEvent::GestureTapUnconfirmed:
     case WebInputEvent::GesturePinchEnd:
     case WebInputEvent::GesturePinchUpdate:
     case WebInputEvent::GestureFlingStart: {
         eventSwallowed = mainFrameImpl()->frame()->eventHandler().handleGestureEvent(platformEvent);
         break;
     }
     default:
         ASSERT_NOT_REACHED();
     }
     m_client->didHandleGestureEvent(event, eventCancelled);
+
+    if (event.type == WebInputEvent::GestureTapDown
+        && shouldGestureTapDownTriggerActive(platformEvent)) {
+        WebGestureEvent showPressEvent = event;
+        showPressEvent.type = WebInputEvent::GestureShowPress;
+        eventSwallowed =  handleGestureEvent(showPressEvent);

[Rick Byers, 2014/02/21 03:35:52]

nit: 2 spaces

[Zeeshan Qureshi, 2014/02/24 03:14:26]

Oh wow, would have never caught this, Thanks.

+        // Ignore subsequent ShowPress events until another TapDown
+        m_gestureTapDownTriggeredActive = true;
+    }
+
     return eventSwallowed;
 }
 
+bool WebViewImpl::shouldGestureTapDownTriggerActive(const WebCore::PlatformGestureEvent& event)
+{
+    Frame* mainFrame = mainFrameImpl()->frame();
+    FrameView* frameView = mainFrame->view();
+
+    // Only activate on TapDown if page isn't scrollable or pinchable and

[Rick Byers, 2014/02/21 03:35:52]

A little more explanation is probably in order around this function.  I'd say
something like "GestureShowPress is normally delayed to avoid triggering on the
start of scroll, but when scrolling and pinching aren't possible we can do the
ShowPress early, immediately after TapDown".

+    // this isn't the start of a scroll.
+    if (frameView && !frameView->isScrollable() && !isPinchZoomable()) {
+        IntPoint adjustedPoint = event.position();
+        Frame* eventFrame = mainFrame->eventHandler().frameForGestureEvent(event, adjustedPoint);
+        IntPoint hitTestPoint = eventFrame->view()->windowToContents(event.position());
+        HitTestResult result = mainFrame->eventHandler().hitTestResultAtPoint(hitTestPoint, HitTestRequest::TouchEvent | HitTestRequest::ReadOnly  | HitTestRequest::AllowFrameScrollbars);
+
+        // If no ancestor is scrollable then this couldn't possibly be the start of a scroll.
+        return !eventFrame->eventHandler().hasScrollableAncestor(result.innerElement());
+    }
+
+    return false;
+}
+
 void WebViewImpl::transferActiveWheelFlingAnimation(const WebActiveWheelFlingParameters& parameters)
 {
     TRACE_EVENT0("webkit", "WebViewImpl::transferActiveWheelFlingAnimation");
     ASSERT(!m_gestureAnimation);
     m_positionOnFlingStart = parameters.point;
     m_globalPositionOnFlingStart = parameters.globalPoint;
     m_flingModifier = parameters.modifiers;
     OwnPtr<WebGestureCurve> curve = adoptPtr(Platform::current()->createFlingAnimationCurve(parameters.sourceDevice, WebFloatPoint(parameters.delta), parameters.cumulativeScroll));
     m_gestureAnimation = WebActiveGestureAnimation::createWithTimeOffset(curve.release(), this, parameters.startTime);
     scheduleAnimation();
@@ skipping 2175 matching lines @@
 float WebViewImpl::minimumPageScaleFactor() const
 {
     return m_pageScaleConstraintsSet.finalConstraints().minimumScale;
 }
 
 float WebViewImpl::maximumPageScaleFactor() const
 {
     return m_pageScaleConstraintsSet.finalConstraints().maximumScale;
 }
 
+bool WebViewImpl::isPinchZoomable() const
+{
+    // This covers all cases:
+    //  * viewport user-scalable: no
+    //  * viewport minimum and maximum scale equal
+    //  * pinch disabled by command line flag
+    return minimumPageScaleFactor() != maximumPageScaleFactor();
+}
+
 void WebViewImpl::saveScrollAndScaleState()
 {
     m_savedPageScaleFactor = pageScaleFactor();
     m_savedScrollOffset = mainFrame()->scrollOffset();
 }
 
 void WebViewImpl::restoreScrollAndScaleState()
 {
     if (!m_savedPageScaleFactor)
         return;
@@ skipping 1022 matching lines @@
     const PageScaleConstraints& constraints = m_pageScaleConstraintsSet.pageDefinedConstraints();
 
     if (!mainFrameImpl() || !mainFrameImpl()->frameView())
         return false;
 
     return mainFrameImpl()->frameView()->layoutSize().width() == m_size.width
         || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 } // namespace blink