Coalesce async touch move events until the ack back from render

content/browser/renderer_host/input/input_router_impl.cc

 // Copyright 2013 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/input_router_impl.h"
 
 #include <math.h>
 
 #include "base/auto_reset.h"
 #include "base/command_line.h"
@@ skipping 338 matching lines @@
                                       const ui::LatencyInfo& latency_info,
                                       bool is_keyboard_shortcut) {
   output_stream_validator_.Validate(input_event);
 
   if (OfferToClient(input_event, latency_info))
     return;
 
   OfferToRenderer(input_event, latency_info, is_keyboard_shortcut);
 
   // Touch events should always indicate in the event whether they are
-  // cancelable (respect ACK disposition) or not.
-  bool ignores_ack = WebInputEventTraits::IgnoresAckDisposition(input_event);
-  if (WebInputEvent::isTouchEventType(input_event.type)) {
+  // cancelable (respect ACK disposition) or not except touchmove.
+  bool needs_synthetic_ack =
+      WebInputEventTraits::WillReceiveAckFromRenderer(input_event);
+
+  if (WebInputEvent::isTouchEventType(input_event.type) &&
+      input_event.type != WebInputEvent::TouchMove) {
     const WebTouchEvent& touch = static_cast<const WebTouchEvent&>(input_event);
-    DCHECK_NE(ignores_ack, !!touch.cancelable);
+    DCHECK_EQ(needs_synthetic_ack, touch.cancelable);
   }
 
-  // If we don't care about the ack disposition, send the ack immediately.
-  if (ignores_ack) {
-    ProcessInputEventAck(input_event.type,
-                         INPUT_EVENT_ACK_STATE_IGNORED,
-                         latency_info,
-                         IGNORING_DISPOSITION);
+  // If we don't need synthetic ack from render, send the ack immediately.
+  if (!needs_synthetic_ack) {

[jdduke (slow), 2015/05/08 21:30:48]

Hmm, synthetic means fake, so I think this should be

if (needs_synthetic_ack) 

(so we need to reverse initialization of the variable).

[lanwei, 2015/05/11 19:27:56]

Done.

+    ProcessInputEventAck(
+        input_event.type, INPUT_EVENT_ACK_STATE_IGNORED, latency_info,
+        WebInputEventTraits::GetUniqueTouchEventId(input_event),
+        IGNORING_DISPOSITION);
   }
 }
 
 bool InputRouterImpl::OfferToClient(const WebInputEvent& input_event,
                                     const ui::LatencyInfo& latency_info) {
   bool consumed = false;
 
   InputEventAckState filter_ack =
       client_->FilterInputEvent(input_event, latency_info);
   switch (filter_ack) {
     case INPUT_EVENT_ACK_STATE_CONSUMED:
-    case INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS:
+    case INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS: {
       // Send the ACK and early exit.
       next_mouse_move_.reset();
-      ProcessInputEventAck(input_event.type, filter_ack, latency_info, CLIENT);
+      InputEventAck ack(

[jdduke (slow), 2015/05/08 21:30:48]

You can remove this unused variable.

[lanwei, 2015/05/11 19:27:55]

Done.

+          input_event.type, filter_ack, latency_info,
+          WebInputEventTraits::GetUniqueTouchEventId(input_event));
+      ProcessInputEventAck(
+          input_event.type, filter_ack, latency_info,
+          WebInputEventTraits::GetUniqueTouchEventId(input_event), CLIENT);
       // WARNING: |this| may be deleted at this point.
       consumed = true;
       break;
+    }
     case INPUT_EVENT_ACK_STATE_UNKNOWN:
       // Simply drop the event.
       consumed = true;
       break;
     default:
       break;
   }
 
   return consumed;
 }
 
 bool InputRouterImpl::OfferToRenderer(const WebInputEvent& input_event,
                                       const ui::LatencyInfo& latency_info,
                                       bool is_keyboard_shortcut) {
   if (Send(new InputMsg_HandleInputEvent(
           routing_id(), &input_event, latency_info, is_keyboard_shortcut))) {
     // Ack messages for ignored ack event types should never be sent by the
     // renderer. Consequently, such event types should not affect event time
     // or in-flight event count metrics.
-    if (!WebInputEventTraits::IgnoresAckDisposition(input_event)) {
+    if (WebInputEventTraits::WillReceiveAckFromRenderer(input_event)) {
       input_event_start_time_ = TimeTicks::Now();
       client_->IncrementInFlightEventCount();
     }
     return true;
   }
   return false;
 }
 
-void InputRouterImpl::OnInputEventAck(
-    const InputHostMsg_HandleInputEvent_ACK_Params& ack) {
+void InputRouterImpl::OnInputEventAck(const InputEventAck& ack) {
   client_->DecrementInFlightEventCount();
-
   // Log the time delta for processing an input event.
   TimeDelta delta = TimeTicks::Now() - input_event_start_time_;
   UMA_HISTOGRAM_TIMES("MPArch.IIR_InputEventDelta", delta);
 
   if (ack.overscroll) {
     DCHECK(ack.type == WebInputEvent::MouseWheel ||
            ack.type == WebInputEvent::GestureScrollUpdate);
     OnDidOverscroll(*ack.overscroll);
   }
 
-  ProcessInputEventAck(ack.type, ack.state, ack.latency, RENDERER);
-  // WARNING: |this| may be deleted at this point.
-
-  // This is used only for testing, and the other end does not use the
-  // source object.  On linux, specifying
-  // Source<RenderWidgetHost> results in a very strange
-  // runtime error in the epilogue of the enclosing
-  // (ProcessInputEventAck) method, but not on other platforms; using
-  // 'void' instead is just as safe (since NotificationSource
-  // is not actually typesafe) and avoids this error.
-  int type = static_cast<int>(ack.type);
-  NotificationService::current()->Notify(
-      NOTIFICATION_RENDER_WIDGET_HOST_DID_RECEIVE_INPUT_EVENT_ACK,
-      Source<void>(this),
-      Details<int>(&type));
+  ProcessInputEventAck(ack.type, ack.state, ack.latency,
+                       ack.unique_touch_event_id, RENDERER);
 }
 
 void InputRouterImpl::OnDidOverscroll(const DidOverscrollParams& params) {
   client_->DidOverscroll(params);
 }
 
 void InputRouterImpl::OnMsgMoveCaretAck() {
   move_caret_pending_ = false;
   if (next_move_caret_)
     SendMoveCaret(next_move_caret_.Pass());
@@ skipping 38 matching lines @@
   // TOUCH_ACTION_NONE should disable the touch ack timeout.
   UpdateTouchAckTimeoutEnabled();
 }
 
 void InputRouterImpl::OnDidStopFlinging() {
   // TODO(jdduke): Track fling status to allow flush notifications after a fling
   // has terminated, crbug.com/483037.
   client_->DidStopFlinging();
 }
 
-void InputRouterImpl::ProcessInputEventAck(
-    WebInputEvent::Type event_type,
-    InputEventAckState ack_result,
-    const ui::LatencyInfo& latency_info,
-    AckSource ack_source) {
+void InputRouterImpl::ProcessInputEventAck(WebInputEvent::Type event_type,
+                                           InputEventAckState ack_result,
+                                           const ui::LatencyInfo& latency_info,
+                                           uint32 unique_touch_event_id,
+                                           AckSource ack_source) {
   TRACE_EVENT2("input", "InputRouterImpl::ProcessInputEventAck",
                "type", WebInputEventTraits::GetName(event_type),
                "ack", GetEventAckName(ack_result));
 
   // Note: The keyboard ack must be treated carefully, as it may result in
   // synchronous destruction of |this|. Handling immediately guards against
   // future references to |this|, as with |auto_reset_current_ack_source| below.
   if (WebInputEvent::isKeyboardEventType(event_type)) {
     ProcessKeyboardAck(event_type, ack_result);
     // WARNING: |this| may be deleted at this point.
     return;
   }
 
   base::AutoReset<AckSource> auto_reset_current_ack_source(
       &current_ack_source_, ack_source);
 
   if (WebInputEvent::isMouseEventType(event_type)) {
     ProcessMouseAck(event_type, ack_result);
   } else if (event_type == WebInputEvent::MouseWheel) {
     ProcessWheelAck(ack_result, latency_info);
   } else if (WebInputEvent::isTouchEventType(event_type)) {
-    ProcessTouchAck(ack_result, latency_info);
+    ProcessTouchAck(ack_result, latency_info, unique_touch_event_id);
   } else if (WebInputEvent::isGestureEventType(event_type)) {
     ProcessGestureAck(event_type, ack_result, latency_info);
   } else if (event_type != WebInputEvent::Undefined) {
     ack_handler_->OnUnexpectedEventAck(InputAckHandler::BAD_ACK_MESSAGE);
   }
 
   SignalFlushedIfNecessary();
 }
 
 void InputRouterImpl::ProcessKeyboardAck(blink::WebInputEvent::Type type,
@@ skipping 58 matching lines @@
   }
 }
 
 void InputRouterImpl::ProcessGestureAck(WebInputEvent::Type type,
                                         InputEventAckState ack_result,
                                         const ui::LatencyInfo& latency) {
   // |gesture_event_queue_| will forward to OnGestureEventAck when appropriate.
   gesture_event_queue_.ProcessGestureAck(ack_result, type, latency);
 }
 
-void InputRouterImpl::ProcessTouchAck(
-    InputEventAckState ack_result,
-    const ui::LatencyInfo& latency) {
+void InputRouterImpl::ProcessTouchAck(InputEventAckState ack_result,
+                                      const ui::LatencyInfo& latency,
+                                      uint32 unique_touch_event_id) {
   // |touch_event_queue_| will forward to OnTouchEventAck when appropriate.
-  touch_event_queue_.ProcessTouchAck(ack_result, latency);
+  touch_event_queue_.ProcessTouchAck(ack_result, latency,
+                                     unique_touch_event_id);
 }
 
 void InputRouterImpl::UpdateTouchAckTimeoutEnabled() {
   // Mobile sites tend to be well-behaved with respect to touch handling, so
   // they have less need for the touch timeout fallback.
   const bool fixed_page_scale = (current_view_flags_ & FIXED_PAGE_SCALE) != 0;
   const bool mobile_viewport = (current_view_flags_ & MOBILE_VIEWPORT) != 0;
 
   // TOUCH_ACTION_NONE will prevent scrolling, in which case the timeout serves
   // little purpose. It's also a strong signal that touch handling is critical
@@ skipping 12 matching lines @@
     return;
 
   if (HasPendingEvents())
     return;
 
   flush_requested_ = false;
   client_->DidFlush();
 }
 
 }  // namespace content