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

Source/web/WebViewImpl.cpp

Index: Source/web/WebViewImpl.cpp
diff --git a/Source/web/WebViewImpl.cpp b/Source/web/WebViewImpl.cpp
index 0357f7dff29e05cb63ba935b5f90958435923a95..5f6f51368008b6c3ed0da5bb17107fd532c59c98 100644
--- a/Source/web/WebViewImpl.cpp
+++ b/Source/web/WebViewImpl.cpp
@@ -382,6 +382,7 @@ WebViewImpl::WebViewImpl(WebViewClient* client)
     , m_backgroundColorOverride(Color::transparent)
     , m_zoomFactorOverride(0)
     , m_helperPluginCloseTimer(this, &WebViewImpl::closePendingHelperPlugins)
+    , m_gestureTapDownTriggeredActive(false)
 {
     Page::PageClients pageClients;
     pageClients.chromeClient = &m_chromeClientImpl;
@@ -639,6 +640,10 @@ bool WebViewImpl::handleGestureEvent(const WebGestureEvent& event)
     // 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);
@@ -733,10 +738,13 @@ bool WebViewImpl::handleGestureEvent(const WebGestureEvent& event)
         // 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:
@@ -752,9 +760,39 @@ bool WebViewImpl::handleGestureEvent(const WebGestureEvent& event)
         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");
@@ -2950,6 +2988,15 @@ 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();