Make sure send one WebTouchEvent ack per ui::TouchEvent

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index fd85fcc8745cdf59c93e87322518bda129aff961..75b9df1b453ba8426aff8f04e90ae630b2469f1c 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -805,6 +805,18 @@ void RenderWidgetHostViewAura::ParentHierarchyChanged() {
   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)
@@ -2184,6 +2196,10 @@ void RenderWidgetHostViewAura::OnTouchEvent(ui::TouchEvent* event) {
   // 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());
 }