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::SetTouchPointStateStationary(
+    blink::WebTouchEvent* event, int touch_id) {
+  if (event->type == blink::WebInputEvent::TouchMove
+      || event->type == blink::WebInputEvent::TouchCancel) {

[tdresser, 2015/05/06 11:58:18]

Why TouchMove and TouchCancel?
Can't this occur with TouchStart/TouchEnd?

[jdduke (slow), 2015/05/06 15:23:45]

I don't think we will ever generate multiple press/release pointers per
MotionEvent, but it wouldn't hurt validate that.

[tdresser, 2015/05/06 15:28:34]

Right, thanks.

Do we generate multiple cancel pointers for a single MotionEvent on Aura?

[lanwei, 2015/05/07 02:37:56]

For touchstart and touchend, because motion_event has type of ACTION_DOWN and
ACTION_POINTER_DOWN, when converting from motion_event to webtouchevent, the
state is correctly setup.
https://code.google.com/p/chromium/codesearch#chromium/src/ui/events/blink/bl...

I tested for touchcancel, it has the same problem as touchmove, all the touch
points will be set to cancel ad the states, so we need to cleanup both touchmove
and touchcancel.

[tdresser, 2015/05/07 12:13:06]

Acknowledged.

+    size_t index = static_cast<int>(pointer_state_.GetIndexFromId(touch_id));

[tdresser, 2015/05/06 11:58:18]

I'm a bit uneasy about relying on the fact that we use the same index in
MotionEventAura and WebInputEvent.

Can't we just check the id for each pointer?

[jdduke (slow), 2015/05/06 15:23:45]

+1

[lanwei, 2015/05/07 02:37:56]

You are right, index is not safe, I am using touch_id instead.
Done.

+    for (size_t i = 0; i < event->touchesLength; ++i) {
+      if (i != index)
+        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 1359 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.
+  SetTouchPointStateStationary(&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