gesture recognizer: Remove the touch-event queue.

content/browser/renderer_host/touch_event_queue.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/touch_event_queue.h"
 
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/port/browser/render_widget_host_view_port.h"
 
 namespace content {
 
 TouchEventQueue::TouchEventQueue(RenderWidgetHostImpl* host)
     : render_widget_host_(host) {
 }
 
 TouchEventQueue::~TouchEventQueue() {
 }
 
 void TouchEventQueue::QueueEvent(const WebKit::WebTouchEvent& event) {
   if (touch_queue_.empty()) {
     // There is no touch event in the queue. Forward it to the renderer
     // immediately.
     touch_queue_.push_back(event);
     render_widget_host_->ForwardTouchEventImmediately(event);
     return;
   }
 
-  // TODO(sad): Coalesce with |touch_queue_.back()| if appropriate.
-  // http://crbug.com/110231
-  touch_queue_.push_back(event);
+  if (!CoalesceIfPossible(event))
+    touch_queue_.push_back(event);

[aelias_OOO_until_Jul13, 2012/10/17 01:52:57]

Can we just move the coalescing logic into QueueEvent?  It seems weird to have
two push_back calls.

[sadrul, 2012/10/17 02:18:00]

Good idea. Done.

 }
 
 void TouchEventQueue::ProcessTouchAck(bool processed) {
+  PopTouchEventToView(processed);
+  // If there's a queued touch-event, then forward it to the renderer now.
+  if (!touch_queue_.empty())
+    render_widget_host_->ForwardTouchEventImmediately(touch_queue_.front());
+}
+
+void TouchEventQueue::FlushQueue() {
+  while (!touch_queue_.empty())
+    PopTouchEventToView(false);
+}
+
+void TouchEventQueue::Reset() {
+  touch_queue_.clear();
+}
+
+void TouchEventQueue::PopTouchEventToView(bool processed) {
   CHECK(!touch_queue_.empty());
   WebKit::WebTouchEvent acked_event = touch_queue_.front();
   touch_queue_.pop_front();
 
   // Note that acking the touch-event may result in multiple gestures being sent
   // to the renderer.
   RenderWidgetHostViewPort* view = RenderWidgetHostViewPort::FromRWHV(
       render_widget_host_->GetView());
   view->ProcessAckedTouchEvent(acked_event, processed);
+}
 
-  // If there's a queued touch-event, then forward it to the renderer now.
-  if (!touch_queue_.empty())
-    render_widget_host_->ForwardTouchEventImmediately(touch_queue_.front());
+bool TouchEventQueue::CoalesceIfPossible(const WebKit::WebTouchEvent& event) {
+  if (empty())
+    return false;
+
+  // Allow coalescing only touch-move events, and only if they have the same
+  // number of touches and the same modifiers.
+  WebKit::WebTouchEvent& last_event = touch_queue_.back();
+  if (event.type != WebKit::WebInputEvent::TouchMove ||
+      last_event.type != WebKit::WebInputEvent::TouchMove)
+    return false;
+
+  if (event.modifiers != last_event.modifiers)
+    return false;
+  if (event.touchesLength != last_event.touchesLength)
+    return false;
+
+  // The WebTouchPoints include absolute position information. So it is
+  // sufficient to simply replace the previous event with the new event.
+  touch_queue_.pop_back();
+  touch_queue_.push_back(event);
+  return true;
 }
 
 }  // namespace content