Make sure send one WebTouchEvent ack per ui::TouchEvent

In our current code (RenderWidgetHostViewAura), we may send more than one ack
for one WebTouchEvent in the multi-touch scenario, but we should only send
one WebTouchEvent ack for each ui::TouchEvent. For touchmove and
touchcancel, we will only change the state for the actual touch point which
causes this touchevent for multi-touch.

BUG=484276

Review URL: https://codereview.chromium.org/1120293003

Cr-Commit-Position: refs/heads/master@{#329161}

2 files changed, 111 insertions, 5 deletions

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 420f475..93a4e93 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -277,6 +277,20 @@ bool IsFractionalScaleFactor(float scale_factor) {
   return (scale_factor - static_cast<int>(scale_factor)) > 0;
 }
 
+// Reset unchanged touch point to StateStationary for touchmove and
+// touchcancel.
+void 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;
+    }
+  }
+}
+
 }  // namespace
 
 // We need to watch for mouse events outside a Web Popup or its parent
@@ -1278,10 +1292,14 @@ void RenderWidgetHostViewAura::ProcessAckedTouchEvent(
       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;
+    }
   }
 }
 
@@ -2180,6 +2198,10 @@ void RenderWidgetHostViewAura::OnTouchEvent(ui::TouchEvent* event) {
   // processed by the gesture recognizer before events currently awaiting
   // dispatch in the touch queue.
   event->DisableSynchronousHandling();
+
+  // Set unchanged 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());
 }
 
diff --git a/content/browser/renderer_host/render_widget_host_view_aura_unittest.cc b/content/browser/renderer_host/render_widget_host_view_aura_unittest.cc
index aba2b57..eb32f72 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura_unittest.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura_unittest.cc
@@ -223,8 +223,10 @@ class FakeWindowEventDispatcher : public aura::WindowEventDispatcher {
     processed_touch_event_count_++;
   }
 
-  size_t processed_touch_event_count() {
-    return processed_touch_event_count_;
+  size_t GetAndResetProcessedTouchEventCount() {
+    size_t count = processed_touch_event_count_;
+    processed_touch_event_count_ = 0;
+    return count;
   }
 
  private:
@@ -1124,6 +1126,88 @@ TEST_F(RenderWidgetHostViewAuraTest, TouchEventState) {
   EXPECT_EQ(nullptr, view_->touch_event_);
 }
 
+// Checks that touch-event state is maintained correctly for multiple touch
+// points.
+TEST_F(RenderWidgetHostViewAuraTest, MultiTouchPointsStates) {
+  view_->InitAsFullscreen(parent_view_);
+  view_->Show();
+  view_->UseFakeDispatcher();
+  GetSentMessageCountAndResetSink();
+
+  ui::TouchEvent press0(ui::ET_TOUCH_PRESSED, gfx::Point(30, 30), 0,
+                        ui::EventTimeForNow());
+
+  view_->OnTouchEvent(&press0);
+  SendInputEventACK(blink::WebInputEvent::TouchStart,
+                    INPUT_EVENT_ACK_STATE_CONSUMED);
+  EXPECT_EQ(blink::WebInputEvent::TouchStart, view_->touch_event_->type);
+  EXPECT_EQ(1U, view_->touch_event_->touchesLength);
+  EXPECT_EQ(1U, view_->dispatcher_->GetAndResetProcessedTouchEventCount());
+
+  ui::TouchEvent move0(ui::ET_TOUCH_MOVED, gfx::Point(20, 20), 0,
+                       ui::EventTimeForNow());
+
+  view_->OnTouchEvent(&move0);
+  SendInputEventACK(blink::WebInputEvent::TouchMove,
+                    INPUT_EVENT_ACK_STATE_CONSUMED);
+  EXPECT_EQ(blink::WebInputEvent::TouchMove, view_->touch_event_->type);
+  EXPECT_EQ(1U, view_->touch_event_->touchesLength);
+  EXPECT_EQ(1U, view_->dispatcher_->GetAndResetProcessedTouchEventCount());
+
+  // For the second touchstart, only the state of the second touch point is
+  // StatePressed, the state of the first touch point is StateStationary.
+  ui::TouchEvent press1(ui::ET_TOUCH_PRESSED, gfx::Point(10, 10), 1,
+                        ui::EventTimeForNow());
+
+  view_->OnTouchEvent(&press1);
+  SendInputEventACK(blink::WebInputEvent::TouchStart,
+                    INPUT_EVENT_ACK_STATE_CONSUMED);
+  EXPECT_EQ(blink::WebInputEvent::TouchStart, view_->touch_event_->type);
+  EXPECT_EQ(2U, view_->touch_event_->touchesLength);
+  EXPECT_EQ(1U, view_->dispatcher_->GetAndResetProcessedTouchEventCount());
+
+  // For the touchmove of second point, the state of the second touch point is
+  // StateMoved, the state of the first touch point is StateStationary.
+  ui::TouchEvent move1(ui::ET_TOUCH_MOVED, gfx::Point(30, 30), 1,
+                       ui::EventTimeForNow());
+
+  view_->OnTouchEvent(&move1);
+  SendInputEventACK(blink::WebInputEvent::TouchMove,
+                    INPUT_EVENT_ACK_STATE_CONSUMED);
+  EXPECT_EQ(blink::WebInputEvent::TouchMove, view_->touch_event_->type);
+  EXPECT_EQ(2U, view_->touch_event_->touchesLength);
+  EXPECT_EQ(1U, view_->dispatcher_->GetAndResetProcessedTouchEventCount());
+
+  // For the touchmove of first point, the state of the first touch point is
+  // StateMoved, the state of the second touch point is StateStationary.
+  ui::TouchEvent move2(ui::ET_TOUCH_MOVED, gfx::Point(10, 10), 0,
+                       ui::EventTimeForNow());
+
+  view_->OnTouchEvent(&move2);
+  SendInputEventACK(blink::WebInputEvent::TouchMove,
+                    INPUT_EVENT_ACK_STATE_CONSUMED);
+  EXPECT_EQ(blink::WebInputEvent::TouchMove, view_->touch_event_->type);
+  EXPECT_EQ(2U, view_->touch_event_->touchesLength);
+  EXPECT_EQ(1U, view_->dispatcher_->GetAndResetProcessedTouchEventCount());
+
+  ui::TouchEvent cancel0(ui::ET_TOUCH_CANCELLED, gfx::Point(10, 10), 0,
+                         ui::EventTimeForNow());
+
+  // For the touchcancel, only the state of the current touch point is
+  // StateCancelled, the state of the other touch point is StateStationary.
+  view_->OnTouchEvent(&cancel0);
+  EXPECT_EQ(blink::WebInputEvent::TouchCancel, view_-> touch_event_->type);
+  EXPECT_EQ(1U, view_->touch_event_->touchesLength);
+  EXPECT_EQ(1U, view_->dispatcher_->GetAndResetProcessedTouchEventCount());
+
+  ui::TouchEvent cancel1(ui::ET_TOUCH_CANCELLED, gfx::Point(30, 30), 1,
+                         ui::EventTimeForNow());
+
+  view_->OnTouchEvent(&cancel1);
+  EXPECT_EQ(1U, view_->dispatcher_->GetAndResetProcessedTouchEventCount());
+  EXPECT_EQ(nullptr, view_->touch_event_);
+}
+
 // Checks that touch-events are queued properly when there is a touch-event
 // handler on the page.
 TEST_F(RenderWidgetHostViewAuraTest, TouchEventSyncAsync) {
@@ -3321,7 +3405,7 @@ TEST_F(RenderWidgetHostViewAuraTest, CorrectNumberOfAcksAreDispatched) {
   SendInputEventACK(blink::WebInputEvent::TouchStart,
                     INPUT_EVENT_ACK_STATE_CONSUMED);
 
-  EXPECT_EQ(2U, view_->dispatcher_->processed_touch_event_count());
+  EXPECT_EQ(2U, view_->dispatcher_->GetAndResetProcessedTouchEventCount());
 }
 
 // Tests that the scroll deltas stored within the overscroll controller get