Revert 266470 "Implement async touchmove dispatch during scroll"

trunk/src/content/browser/renderer_host/input/touch_event_queue.cc

Index: trunk/src/content/browser/renderer_host/input/touch_event_queue.cc
===================================================================
--- trunk/src/content/browser/renderer_host/input/touch_event_queue.cc	(revision 266575)
+++ trunk/src/content/browser/renderer_host/input/touch_event_queue.cc	(working copy)
@@ -21,15 +21,6 @@
 namespace content {
 namespace {
 
-// Time interval at which touchmove events will be forwarded to the client while
-// scrolling is active and possible.
-const double kAsyncTouchMoveIntervalSec = .2;
-
-// A slop region just larger than that used by many web applications. When
-// touchmove's are being sent asynchronously, movement outside this region will
-// trigger an immediate async touchmove to cancel potential tap-related logic.
-const double kApplicationSlopRegionLengthDipsSqared = 15. * 15.;
-
 // Using a small epsilon when comparing slop distances allows pixel perfect
 // slop determination when using fractional DIP coordinates (assuming the slop
 // region and DPI scale are reasonably proportioned).
@@ -48,18 +39,11 @@
   return event;
 }
 
-bool ShouldTouchTriggerTimeout(const WebTouchEvent& event) {
-  return (event.type == WebInputEvent::TouchStart ||
-          event.type == WebInputEvent::TouchMove) &&
-         !WebInputEventTraits::IgnoresAckDisposition(event);
+bool ShouldTouchTypeTriggerTimeout(WebInputEvent::Type type) {
+  return type == WebInputEvent::TouchStart ||
+         type == WebInputEvent::TouchMove;
 }
 
-bool OutsideApplicationSlopRegion(const WebTouchEvent& event,
-                                  const gfx::PointF& anchor) {
-  return (gfx::PointF(event.touches[0].position) - anchor).LengthSquared() >
-         kApplicationSlopRegionLengthDipsSqared;
-}
-
 }  // namespace
 
 
@@ -79,7 +63,7 @@
 
   void Start(const TouchEventWithLatencyInfo& event) {
     DCHECK_EQ(pending_ack_state_, PENDING_ACK_NONE);
-    DCHECK(ShouldTouchTriggerTimeout(event.event));
+    DCHECK(ShouldTouchTypeTriggerTimeout(event.event.type));
     timeout_event_ = event;
     timeout_monitor_.Restart(timeout_delay_);
   }
@@ -94,7 +78,7 @@
           SetPendingAckState(PENDING_ACK_CANCEL_EVENT);
           TouchEventWithLatencyInfo cancel_event =
               ObtainCancelEventForTouchEvent(timeout_event_);
-          touch_queue_->SendTouchEventImmediately(cancel_event);
+          touch_queue_->client_->SendTouchEventImmediately(cancel_event);
         } else {
           SetPendingAckState(PENDING_ACK_NONE);
           touch_queue_->UpdateTouchAckStates(timeout_event_.event, ack_result);
@@ -244,27 +228,25 @@
 // the Client receives the event with their original timestamp.
 class CoalescedWebTouchEvent {
  public:
-  // Events for which |async| is true will not be ack'ed to the client after the
-  // corresponding ack is received following dispatch.
-  CoalescedWebTouchEvent(const TouchEventWithLatencyInfo& event, bool async)
-      : coalesced_event_(event) {
-    if (async)
-      coalesced_event_.event.cancelable = false;
-    else
-      events_to_ack_.push_back(event);
-
-    TRACE_EVENT_ASYNC_BEGIN0("input", "TouchEventQueue::QueueEvent", this);
+  CoalescedWebTouchEvent(const TouchEventWithLatencyInfo& event,
+                         bool ignore_ack)
+      : coalesced_event_(event),
+        ignore_ack_(ignore_ack) {
+    events_.push_back(event);
+    TRACE_EVENT_ASYNC_BEGIN0(
+        "input", "TouchEventQueue::QueueEvent", this);
   }
 
   ~CoalescedWebTouchEvent() {
-    TRACE_EVENT_ASYNC_END0("input", "TouchEventQueue::QueueEvent", this);
+    TRACE_EVENT_ASYNC_END0(
+        "input", "TouchEventQueue::QueueEvent", this);
   }
 
   // Coalesces the event with the existing event if possible. Returns whether
   // the event was coalesced.
   bool CoalesceEventIfPossible(
       const TouchEventWithLatencyInfo& event_with_latency) {
-    if (!WillDispatchAckToClient())
+    if (ignore_ack_)
       return false;
 
     if (!coalesced_event_.CanCoalesceWith(event_with_latency))
@@ -273,51 +255,37 @@
     TRACE_EVENT_INSTANT0(
         "input", "TouchEventQueue::MoveCoalesced", TRACE_EVENT_SCOPE_THREAD);
     coalesced_event_.CoalesceWith(event_with_latency);
-    events_to_ack_.push_back(event_with_latency);
+    events_.push_back(event_with_latency);
     return true;
   }
 
-  void UpdateLatencyInfoForAck(const ui::LatencyInfo& renderer_latency_info) {
-    if (!WillDispatchAckToClient())
-      return;
-
-    for (WebTouchEventWithLatencyList::iterator iter = events_to_ack_.begin(),
-                                                end = events_to_ack_.end();
-         iter != end;
-         ++iter) {
-      iter->latency.AddNewLatencyFrom(renderer_latency_info);
-    }
+  const TouchEventWithLatencyInfo& coalesced_event() const {
+    return coalesced_event_;
   }
 
-  void DispatchAckToClient(InputEventAckState ack_result,
-                           TouchEventQueueClient* client) {
-    DCHECK(client);
-    if (!WillDispatchAckToClient())
-      return;
-
-    for (WebTouchEventWithLatencyList::const_iterator
-             iter = events_to_ack_.begin(),
-             end = events_to_ack_.end();
-         iter != end;
-         ++iter) {
-      client->OnTouchEventAck(*iter, ack_result);
-    }
+  WebTouchEventWithLatencyList::iterator begin() {
+    return events_.begin();
   }
 
-  const TouchEventWithLatencyInfo& coalesced_event() const {
-    return coalesced_event_;
+  WebTouchEventWithLatencyList::iterator end() {
+    return events_.end();
   }
 
+  size_t size() const { return events_.size(); }
+
+  bool ignore_ack() const { return ignore_ack_; }
+
  private:
-  bool WillDispatchAckToClient() const { return !events_to_ack_.empty(); }
-
   // This is the event that is forwarded to the renderer.
   TouchEventWithLatencyInfo coalesced_event_;
 
-  // This is the list of the original events that were coalesced, each requiring
-  // future ack dispatch to the client.
-  WebTouchEventWithLatencyList events_to_ack_;
+  // This is the list of the original events that were coalesced.
+  WebTouchEventWithLatencyList events_;
 
+  // If |ignore_ack_| is true, don't send this touch event to client
+  // when the event is acked.
+  bool ignore_ack_;
+
   DISALLOW_COPY_AND_ASSIGN(CoalescedWebTouchEvent);
 };
 
@@ -331,8 +299,7 @@
       ack_timeout_enabled_(false),
       touchmove_slop_suppressor_(new TouchMoveSlopSuppressor(
           touchmove_suppression_length_dips + kSlopEpsilon)),
-      send_touch_events_async_(false),
-      last_sent_touch_timestamp_sec_(0),
+      absorbing_touch_moves_(false),
       touch_scrolling_mode_(mode) {
   DCHECK(client);
 }
@@ -350,19 +317,17 @@
   if (touch_queue_.empty() && !dispatching_touch_ack_) {
     // Optimization of the case without touch handlers.  Removing this path
     // yields identical results, but this avoids unnecessary allocations.
-    PreFilterResult filter_result = FilterBeforeForwarding(event.event);
-    if (filter_result != FORWARD_TO_RENDERER) {
-      client_->OnTouchEventAck(event,
-                               filter_result == ACK_WITH_NO_CONSUMER_EXISTS
-                                   ? INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS
-                                   : INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    if (touch_filtering_state_ == DROP_ALL_TOUCHES ||
+        (touch_filtering_state_ == DROP_TOUCHES_IN_SEQUENCE &&
+         !WebTouchEventTraits::IsTouchSequenceStart(event.event))) {
+      client_->OnTouchEventAck(event, INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS);
       return;
     }
 
     // There is no touch event in the queue. Forward it to the renderer
     // immediately.
     touch_queue_.push_back(new CoalescedWebTouchEvent(event, false));
-    ForwardNextEventToRenderer();
+    TryForwardNextEventToRenderer();
     return;
   }
 
@@ -405,6 +370,7 @@
     touch_filtering_state_ = DROP_TOUCHES_IN_SEQUENCE;
   }
 
+  UpdateTouchAckStates(acked_event, ack_result);
   PopTouchEventToClient(ack_result, latency_info);
   TryForwardNextEventToRenderer();
 }
@@ -414,102 +380,47 @@
   // If there are queued touch events, then try to forward them to the renderer
   // immediately, or ACK the events back to the client if appropriate.
   while (!touch_queue_.empty()) {
-    PreFilterResult filter_result =
-        FilterBeforeForwarding(touch_queue_.front()->coalesced_event().event);
-    switch (filter_result) {
+    const TouchEventWithLatencyInfo& touch =
+        touch_queue_.front()->coalesced_event();
+    PreFilterResult result = FilterBeforeForwarding(touch.event);
+    switch (result) {
       case ACK_WITH_NO_CONSUMER_EXISTS:
-        PopTouchEventToClient(INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS);
+        PopTouchEventToClient(INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS,
+                              LatencyInfo());
         break;
       case ACK_WITH_NOT_CONSUMED:
-        PopTouchEventToClient(INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+        PopTouchEventToClient(INPUT_EVENT_ACK_STATE_NOT_CONSUMED,
+                              LatencyInfo());
         break;
       case FORWARD_TO_RENDERER:
-        ForwardNextEventToRenderer();
+        ForwardToRenderer(touch);
         return;
     }
   }
 }
 
-void TouchEventQueue::ForwardNextEventToRenderer() {
-  TRACE_EVENT0("input", "TouchEventQueue::ForwardNextEventToRenderer");
+void TouchEventQueue::ForwardToRenderer(
+    const TouchEventWithLatencyInfo& touch) {
+  TRACE_EVENT0("input", "TouchEventQueue::ForwardToRenderer");
 
-  DCHECK(!empty());
   DCHECK(!dispatching_touch_);
   DCHECK_NE(touch_filtering_state_, DROP_ALL_TOUCHES);
-  TouchEventWithLatencyInfo touch = touch_queue_.front()->coalesced_event();
 
   if (WebTouchEventTraits::IsTouchSequenceStart(touch.event)) {
     touch_filtering_state_ =
         ack_timeout_enabled_ ? FORWARD_TOUCHES_UNTIL_TIMEOUT
                              : FORWARD_ALL_TOUCHES;
     touch_ack_states_.clear();
-    send_touch_events_async_ = false;
-    touch_sequence_start_position_ =
-        gfx::PointF(touch.event.touches[0].position);
+    absorbing_touch_moves_ = false;
   }
 
-  if (send_touch_events_async_ &&
-      touch.event.type == WebInputEvent::TouchMove) {
-    // Throttling touchmove's in a continuous touchmove stream while scrolling
-    // reduces the risk of jank. However, it's still important that the web
-    // application be sent touches at key points in the gesture stream,
-    // e.g., when the application slop region is exceeded or touchmove
-    // coalescing fails because of different modifiers.
-    const bool send_touch_move_now =
-        size() > 1 ||
-        (touch.event.timeStampSeconds >=
-         last_sent_touch_timestamp_sec_ + kAsyncTouchMoveIntervalSec) ||
-        (needs_async_touch_move_for_outer_slop_region_ &&
-         OutsideApplicationSlopRegion(touch.event,
-                                      touch_sequence_start_position_)) ||
-        (pending_async_touch_move_ &&
-         !pending_async_touch_move_->CanCoalesceWith(touch));
-
-    if (!send_touch_move_now) {
-      if (!pending_async_touch_move_) {
-        pending_async_touch_move_.reset(new TouchEventWithLatencyInfo(touch));
-      } else {
-        DCHECK(pending_async_touch_move_->CanCoalesceWith(touch));
-        pending_async_touch_move_->CoalesceWith(touch);
-      }
-      PopTouchEventToClient(INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
-      return;
-    }
-  }
-
-  last_sent_touch_timestamp_sec_ = touch.event.timeStampSeconds;
-
-  // Flush any pending async touch move. If it can be combined with the current
-  // (touchmove) event, great, otherwise send it immediately but separately. Its
-  // ack will trigger forwarding of the original |touch| event.
-  if (pending_async_touch_move_) {
-    if (pending_async_touch_move_->CanCoalesceWith(touch)) {
-      pending_async_touch_move_->CoalesceWith(touch);
-      pending_async_touch_move_->event.cancelable = !send_touch_events_async_;
-      touch = *pending_async_touch_move_.Pass();
-    } else {
-      scoped_ptr<TouchEventWithLatencyInfo> async_move =
-          pending_async_touch_move_.Pass();
-      async_move->event.cancelable = false;
-      touch_queue_.push_front(new CoalescedWebTouchEvent(*async_move, true));
-      SendTouchEventImmediately(*async_move);
-      return;
-    }
-  }
-
-  // Note: Marking touchstart events as not-cancelable prevents them from
-  // blocking subsequent gestures, but it may not be the best long term solution
-  // for tracking touch point dispatch.
-  if (send_touch_events_async_)
-    touch.event.cancelable = false;
-
   // A synchronous ack will reset |dispatching_touch_|, in which case
   // the touch timeout should not be started.
   base::AutoReset<bool> dispatching_touch(&dispatching_touch_, true);
-  SendTouchEventImmediately(touch);
+  client_->SendTouchEventImmediately(touch);
   if (dispatching_touch_ &&
       touch_filtering_state_ == FORWARD_TOUCHES_UNTIL_TIMEOUT &&
-      ShouldTouchTriggerTimeout(touch.event)) {
+      ShouldTouchTypeTriggerTimeout(touch.event.type)) {
     DCHECK(timeout_handler_);
     timeout_handler_->Start(touch);
   }
@@ -520,12 +431,8 @@
   if (gesture_event.event.type != blink::WebInputEvent::GestureScrollBegin)
     return;
 
-  if (touch_scrolling_mode_ == TOUCH_SCROLLING_MODE_ASYNC_TOUCHMOVE) {
-    pending_async_touch_move_.reset();
-    send_touch_events_async_ = true;
-    needs_async_touch_move_for_outer_slop_region_ = true;
-    return;
-  }
+  if (touch_scrolling_mode_ == TOUCH_SCROLLING_MODE_ABSORB_TOUCHMOVE)
+    absorbing_touch_moves_ = true;
 
   if (touch_scrolling_mode_ != TOUCH_SCROLLING_MODE_TOUCHCANCEL)
     return;
@@ -556,21 +463,18 @@
 void TouchEventQueue::OnGestureEventAck(
     const GestureEventWithLatencyInfo& event,
     InputEventAckState ack_result) {
-  if (touch_scrolling_mode_ != TOUCH_SCROLLING_MODE_ASYNC_TOUCHMOVE)
+  if (touch_scrolling_mode_ != TOUCH_SCROLLING_MODE_ABSORB_TOUCHMOVE)
     return;
 
   if (event.event.type != blink::WebInputEvent::GestureScrollUpdate)
     return;
 
-  // Throttle sending touchmove events as long as the scroll events are handled.
+  // Suspend sending touchmove events as long as the scroll events are handled.
   // Note that there's no guarantee that this ACK is for the most recent
   // gesture event (or even part of the current sequence).  Worst case, the
-  // delay in updating the absorption state will result in minor UI glitches.
-  // A valid |pending_async_touch_move_| will be flushed when the next event is
-  // forwarded.
-  send_touch_events_async_ = (ack_result == INPUT_EVENT_ACK_STATE_CONSUMED);
-  if (!send_touch_events_async_)
-    needs_async_touch_move_for_outer_slop_region_ = false;
+  // delay in updating the absorption state should only result in minor UI
+  // glitches.
+  absorbing_touch_moves_ = (ack_result == INPUT_EVENT_ACK_STATE_CONSUMED);
 }
 
 void TouchEventQueue::OnHasTouchEventHandlers(bool has_handlers) {
@@ -588,7 +492,6 @@
     // TODO(jdduke): Synthesize a TouchCancel if necessary to update Blink touch
     // state tracking (e.g., if the touch handler was removed mid-sequence).
     touch_filtering_state_ = DROP_ALL_TOUCHES;
-    pending_async_touch_move_.reset();
     if (timeout_handler_)
       timeout_handler_->Reset();
     if (!touch_queue_.empty())
@@ -629,10 +532,6 @@
     timeout_handler_->set_timeout_delay(ack_timeout_delay);
 }
 
-bool TouchEventQueue::HasPendingAsyncTouchMoveForTesting() const {
-  return pending_async_touch_move_;
-}
-
 bool TouchEventQueue::IsTimeoutRunningForTesting() const {
   return timeout_handler_ && timeout_handler_->IsTimeoutTimerRunning();
 }
@@ -645,59 +544,37 @@
 void TouchEventQueue::FlushQueue() {
   DCHECK(!dispatching_touch_ack_);
   DCHECK(!dispatching_touch_);
-  pending_async_touch_move_.reset();
   if (touch_filtering_state_ != DROP_ALL_TOUCHES)
     touch_filtering_state_ = DROP_TOUCHES_IN_SEQUENCE;
-  while (!touch_queue_.empty())
-    PopTouchEventToClient(INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS);
+  while (!touch_queue_.empty()) {
+    PopTouchEventToClient(INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS,
+                          LatencyInfo());
+  }
 }
 
-void TouchEventQueue::PopTouchEventToClient(InputEventAckState ack_result) {
-  AckTouchEventToClient(ack_result, PopTouchEvent());
-}
-
 void TouchEventQueue::PopTouchEventToClient(
     InputEventAckState ack_result,
     const LatencyInfo& renderer_latency_info) {
-  scoped_ptr<CoalescedWebTouchEvent> acked_event = PopTouchEvent();
-  acked_event->UpdateLatencyInfoForAck(renderer_latency_info);
-  AckTouchEventToClient(ack_result, acked_event.Pass());
-}
-
-void TouchEventQueue::AckTouchEventToClient(
-    InputEventAckState ack_result,
-    scoped_ptr<CoalescedWebTouchEvent> acked_event) {
-  DCHECK(acked_event);
   DCHECK(!dispatching_touch_ack_);
-  UpdateTouchAckStates(acked_event->coalesced_event().event, ack_result);
+  if (touch_queue_.empty())
+    return;
+  scoped_ptr<CoalescedWebTouchEvent> acked_event(touch_queue_.front());
+  touch_queue_.pop_front();
 
+  if (acked_event->ignore_ack())
+    return;
+
   // Note that acking the touch-event may result in multiple gestures being sent
   // to the renderer, or touch-events being queued.
-  base::AutoReset<const CoalescedWebTouchEvent*> dispatching_touch_ack(
-      &dispatching_touch_ack_, acked_event.get());
-  acked_event->DispatchAckToClient(ack_result, client_);
-}
+  base::AutoReset<CoalescedWebTouchEvent*>
+      dispatching_touch_ack(&dispatching_touch_ack_, acked_event.get());
 
-scoped_ptr<CoalescedWebTouchEvent> TouchEventQueue::PopTouchEvent() {
-  DCHECK(!touch_queue_.empty());
-  scoped_ptr<CoalescedWebTouchEvent> event(touch_queue_.front());
-  touch_queue_.pop_front();
-  return event.Pass();
-}
-
-void TouchEventQueue::SendTouchEventImmediately(
-    const TouchEventWithLatencyInfo& touch) {
-  if (needs_async_touch_move_for_outer_slop_region_) {
-    // Any event other than a touchmove (e.g., touchcancel or secondary
-    // touchstart) after a scroll has started will interrupt the need to send a
-    // an outer slop-region exceeding touchmove.
-    if (touch.event.type != WebInputEvent::TouchMove ||
-        OutsideApplicationSlopRegion(touch.event,
-                                     touch_sequence_start_position_))
-      needs_async_touch_move_for_outer_slop_region_ = false;
+  for (WebTouchEventWithLatencyList::iterator iter = acked_event->begin(),
+       end = acked_event->end();
+       iter != end; ++iter) {
+    iter->latency.AddNewLatencyFrom(renderer_latency_info);
+    client_->OnTouchEventAck((*iter), ack_result);
   }
-
-  client_->SendTouchEventImmediately(touch);
 }
 
 TouchEventQueue::PreFilterResult
@@ -715,9 +592,12 @@
       event.type != WebInputEvent::TouchCancel) {
     if (WebTouchEventTraits::IsTouchSequenceStart(event))
       return FORWARD_TO_RENDERER;
-    return ACK_WITH_NO_CONSUMER_EXISTS;
+    return ACK_WITH_NOT_CONSUMED;
   }
 
+  if (absorbing_touch_moves_ && event.type == WebInputEvent::TouchMove)
+    return ACK_WITH_NOT_CONSUMED;
+
   // Touch press events should always be forwarded to the renderer.
   if (event.type == WebInputEvent::TouchStart)
     return FORWARD_TO_RENDERER;