Signal input flush when all flings have terminated

content/browser/renderer_host/input/gesture_event_queue.cc

 // Copyright 2014 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/input/gesture_event_queue.h"
 
 #include "base/trace_event/trace_event.h"
 #include "content/browser/renderer_host/input/touchpad_tap_suppression_controller.h"
 #include "content/browser/renderer_host/input/touchscreen_tap_suppression_controller.h"
 
@@ skipping 44 matching lines @@
 }  // namespace
 
 GestureEventQueue::Config::Config() {
 }
 
 GestureEventQueue::GestureEventQueue(
     GestureEventQueueClient* client,
     TouchpadTapSuppressionControllerClient* touchpad_client,
     const Config& config)
     : client_(client),
-      fling_in_progress_(false),
+      active_fling_count_(0),
       scrolling_in_progress_(false),
       ignore_next_ack_(false),
       touchpad_tap_suppression_controller_(
           touchpad_client,
           config.touchpad_tap_suppression_config),
       touchscreen_tap_suppression_controller_(
           this,
           config.touchscreen_tap_suppression_config),
       debounce_interval_(config.debounce_interval) {
   DCHECK(client);
   DCHECK(touchpad_client);
 }
 
 GestureEventQueue::~GestureEventQueue() { }
 
 void GestureEventQueue::QueueEvent(
     const GestureEventWithLatencyInfo& gesture_event) {
   TRACE_EVENT0("input", "GestureEventQueue::QueueEvent");
   if (!ShouldForwardForBounceReduction(gesture_event) ||
       !ShouldForwardForGFCFiltering(gesture_event) ||
       !ShouldForwardForTapSuppression(gesture_event)) {
     return;
   }
 
   QueueAndForwardIfNecessary(gesture_event);
 }
 
 bool GestureEventQueue::ShouldDiscardFlingCancelEvent(
     const GestureEventWithLatencyInfo& gesture_event) const {
-  if (coalesced_gesture_events_.empty() && fling_in_progress_)
-    return false;
   GestureQueue::const_reverse_iterator it =
       coalesced_gesture_events_.rbegin();
   while (it != coalesced_gesture_events_.rend()) {
     if (it->event.type == WebInputEvent::GestureFlingStart)
       return false;
     if (it->event.type == WebInputEvent::GestureFlingCancel)
       return true;
     it++;
   }
-  return true;
+  // If there are no fling-affecting events in the queue, and there's still an
+  // active fling in the renderer, the cancel event should not be dropped.
+  return !active_fling_count_;
 }
 
 bool GestureEventQueue::ShouldForwardForBounceReduction(
     const GestureEventWithLatencyInfo& gesture_event) {
   if (debounce_interval_ <= base::TimeDelta())
     return true;
   switch (gesture_event.event.type) {
     case WebInputEvent::GestureScrollUpdate:
       if (!scrolling_in_progress_) {
         debounce_deferring_timer_.Start(
@@ skipping 51 matching lines @@
       }
       return true;
     default:
       return true;
   }
 }
 
 void GestureEventQueue::QueueAndForwardIfNecessary(
     const GestureEventWithLatencyInfo& gesture_event) {
   switch (gesture_event.event.type) {
-    case WebInputEvent::GestureFlingCancel:
-      fling_in_progress_ = false;
-      break;
-    case WebInputEvent::GestureFlingStart:
-      fling_in_progress_ = true;
-      break;
     case WebInputEvent::GesturePinchUpdate:
     case WebInputEvent::GestureScrollUpdate:
       QueueScrollOrPinchAndForwardIfNecessary(gesture_event);
       return;
     default:
       break;
   }
 
   coalesced_gesture_events_.push_back(gesture_event);
   if (coalesced_gesture_events_.size() == 1)
     client_->SendGestureEventImmediately(gesture_event);
 }
 
 void GestureEventQueue::ProcessGestureAck(InputEventAckState ack_result,
                                           WebInputEvent::Type type,
                                           const ui::LatencyInfo& latency) {
   TRACE_EVENT0("input", "GestureEventQueue::ProcessGestureAck");
 
   if (coalesced_gesture_events_.empty()) {
     DLOG(ERROR) << "Received unexpected ACK for event type " << type;
     return;
   }
 
+  if (ack_result == INPUT_EVENT_ACK_STATE_CONSUMED &&
+      type == blink::WebInputEvent::GestureFlingStart) {
+    ++active_fling_count_;
+  }
+
   // It's possible that the ack for the second event in an in-flight, coalesced
   // Gesture{Scroll,Pinch}Update pair is received prior to the first event ack.
   // TODO(jdduke): Unify GSU/GPU pairs into a single event, crbug.com/359115.
   size_t event_index = 0;
   if (ignore_next_ack_ &&
       coalesced_gesture_events_.size() > 1 &&
       coalesced_gesture_events_[0].event.type != type &&
       coalesced_gesture_events_[1].event.type == type) {
     event_index = 1;
   }
@@ skipping 45 matching lines @@
   client_->SendGestureEventImmediately(first_gesture_event);
   if (second_gesture_event.event.type != WebInputEvent::Undefined)
     client_->SendGestureEventImmediately(second_gesture_event);
 }
 
 TouchpadTapSuppressionController*
     GestureEventQueue::GetTouchpadTapSuppressionController() {
   return &touchpad_tap_suppression_controller_;
 }
 
-void GestureEventQueue::FlingHasBeenHalted() {
-  fling_in_progress_ = false;
+void GestureEventQueue::DidStopFlinging() {
+  DCHECK_GE(active_fling_count_, 0);
+  --active_fling_count_;
 }
 
 void GestureEventQueue::ForwardGestureEvent(
     const GestureEventWithLatencyInfo& gesture_event) {
   QueueAndForwardIfNecessary(gesture_event);
 }
 
 void GestureEventQueue::SendScrollEndingEventsNow() {
   scrolling_in_progress_ = false;
   if (debouncing_deferral_queue_.empty())
@@ skipping 105 matching lines @@
     return 0;
 
   if (!ignore_next_ack_)
     return 1;
 
   DCHECK_GT(coalesced_gesture_events_.size(), 1U);
   return 2;
 }
 
 }  // namespace content