Make sure send one WebTouchEvent ack per ui::TouchEvent

content/browser/renderer_host/render_widget_host_view_aura.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/render_widget_host_view_aura.h"
 
 #include <set>
 
 #include "base/auto_reset.h"
 #include "base/basictypes.h"
@@ skipping 787 matching lines @@
   }
 #endif
 }
 
 void RenderWidgetHostViewAura::ParentHierarchyChanged() {
   ancestor_window_observer_.reset(new WindowAncestorObserver(this));
   // Snap when we receive a hierarchy changed. http://crbug.com/388908.
   HandleParentBoundsChanged();
 }
 
+void RenderWidgetHostViewAura::MarkUnchangedTouchPointsAsStationary(
+    blink::WebTouchEvent* event,
+    int changed_touch_id) {
+  if (event->type == blink::WebInputEvent::TouchMove ||
+      event->type == blink::WebInputEvent::TouchCancel) {
+    for (size_t i = 0; i < event->touchesLength; ++i) {
+      if (event->touches[i].id != changed_touch_id)
+        event->touches[i].state = blink::WebTouchPoint::StateStationary;
+    }
+  }
+}
+
 void RenderWidgetHostViewAura::MovePluginWindows(
     const std::vector<WebPluginGeometry>& plugin_window_moves) {
 #if defined(OS_WIN)
   // We need to clip the rectangle to the tab's viewport, otherwise we will draw
   // over the browser UI.
   if (!window_->GetRootWindow()) {
     DCHECK(plugin_window_moves.empty());
     return;
   }
   HWND parent = window_->GetHost()->GetAcceleratedWidget();
@@ skipping 457 matching lines @@
       break;
     case blink::WebInputEvent::TouchCancel:
       required_state = blink::WebTouchPoint::StateCancelled;
       break;
     default:
       required_state = blink::WebTouchPoint::StateUndefined;
       NOTREACHED();
       break;
   }
 
-  // Only send acks for changed touches.
+  // Only send acks for one changed touch point.
+  bool sent_ack = false;
   for (size_t i = 0; i < touch.event.touchesLength; ++i) {
-    if (touch.event.touches[i].state == required_state)
+    if (touch.event.touches[i].state == required_state) {
+      DCHECK(!sent_ack);
       host->dispatcher()->ProcessedTouchEvent(window_, result);
+      sent_ack = true;
+    }
   }
 }
 
 scoped_ptr<SyntheticGestureTarget>
 RenderWidgetHostViewAura::CreateSyntheticGestureTarget() {
   return scoped_ptr<SyntheticGestureTarget>(
       new SyntheticGestureTargetAura(host_));
 }
 
 InputEventAckState RenderWidgetHostViewAura::FilterInputEvent(
@@ skipping 878 matching lines @@
 
   blink::WebTouchEvent touch_event = ui::CreateWebTouchEventFromMotionEvent(
       pointer_state_, event->may_cause_scrolling());
   pointer_state_.CleanupRemovedTouchPoints(*event);
 
   // It is important to always mark events as being handled asynchronously when
   // they are forwarded. This ensures that the current event does not get
   // processed by the gesture recognizer before events currently awaiting
   // dispatch in the touch queue.
   event->DisableSynchronousHandling();
+
+  // Set unchange touch point to StateStationary for touchmove and
+  // touchcancel to make sure only send one ack per WebTouchEvent.
+  MarkUnchangedTouchPointsAsStationary(&touch_event, event->touch_id());
   host_->ForwardTouchEventWithLatencyInfo(touch_event, *event->latency());
 }
 
 void RenderWidgetHostViewAura::OnGestureEvent(ui::GestureEvent* event) {
   TRACE_EVENT0("input", "RenderWidgetHostViewAura::OnGestureEvent");
   if ((event->type() == ui::ET_GESTURE_PINCH_BEGIN ||
       event->type() == ui::ET_GESTURE_PINCH_UPDATE ||
       event->type() == ui::ET_GESTURE_PINCH_END) && !pinch_zoom_enabled_) {
     event->SetHandled();
     return;
@@ skipping 567 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // RenderWidgetHostViewBase, public:
 
 // static
 void RenderWidgetHostViewBase::GetDefaultScreenInfo(WebScreenInfo* results) {
   GetScreenInfoForWindow(results, NULL);
 }
 
 }  // namespace content