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 230 matching lines @@
   current_view_flags_ = view_flags;
 
   // A fixed page scale or mobile viewport should disable the touch ack timeout.
   UpdateTouchAckTimeoutEnabled();
 }
 
 bool InputRouterImpl::OnMessageReceived(const IPC::Message& message) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(InputRouterImpl, message)
     IPC_MESSAGE_HANDLER(InputHostMsg_HandleInputEvent_ACK, OnInputEventAck)
+    IPC_MESSAGE_HANDLER(InputHostMsg_HandleAsyncTouchEvent_ACK,
+                        OnAsyncTouchEventAck)
     IPC_MESSAGE_HANDLER(InputHostMsg_DidOverscroll, OnDidOverscroll)
     IPC_MESSAGE_HANDLER(InputHostMsg_MoveCaret_ACK, OnMsgMoveCaretAck)
     IPC_MESSAGE_HANDLER(InputHostMsg_SelectRange_ACK, OnSelectMessageAck)
     IPC_MESSAGE_HANDLER(InputHostMsg_MoveRangeSelectionExtent_ACK,
                         OnSelectMessageAck)
     IPC_MESSAGE_HANDLER(ViewHostMsg_HasTouchEventHandlers,
                         OnHasTouchEventHandlers)
     IPC_MESSAGE_HANDLER(InputHostMsg_SetTouchAction,
                         OnSetTouchAction)
     IPC_MESSAGE_UNHANDLED(handled = false)
@@ skipping 79 matching lines @@
   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);
+  bool is_async_touch_move = false;
   if (WebInputEvent::isTouchEventType(input_event.type)) {
     const WebTouchEvent& touch = static_cast<const WebTouchEvent&>(input_event);
-    DCHECK_NE(ignores_ack, !!touch.cancelable);
+    if (touch.type == WebInputEvent::TouchMove && !touch.cancelable)
+      is_async_touch_move = true;
+
+    if (touch.type != WebInputEvent::TouchMove)
+      DCHECK_NE(ignores_ack, touch.cancelable);
   }
 
-  // If we don't care about the ack disposition, send the ack immediately.
-  if (ignores_ack) {
+  // If we don't care about the ack disposition, or it is an async touchmove
+  // event, send the ack immediately.
+  if (ignores_ack || is_async_touch_move) {
     ProcessInputEventAck(input_event.type,
                          INPUT_EVENT_ACK_STATE_IGNORED,
                          latency_info,
                          IGNORING_DISPOSITION);
   }
 }
 
 bool InputRouterImpl::OfferToClient(const WebInputEvent& input_event,
                                     const ui::LatencyInfo& latency_info) {
   bool consumed = false;
@@ skipping 61 matching lines @@
   // (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));
 }
 
+void InputRouterImpl::OnAsyncTouchEventAck(
+    const InputHostMsg_HandleAsyncTouchEvent_ACK_Params& ack) {
+  ProcessAsyncTouchAck();
+  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));
+}
+
 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 142 matching lines @@
   gesture_event_queue_.ProcessGestureAck(ack_result, type, latency);
 }
 
 void InputRouterImpl::ProcessTouchAck(
     InputEventAckState ack_result,
     const ui::LatencyInfo& latency) {
   // |touch_event_queue_| will forward to OnTouchEventAck when appropriate.
   touch_event_queue_.ProcessTouchAck(ack_result, latency);
 }
 
+void InputRouterImpl::ProcessAsyncTouchAck() {
+  touch_event_queue_.ProcessAsyncTouchAck();
+}
+
 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
   // to page functionality, so the timeout could do more harm than good.
   const bool touch_action_none =
@@ skipping 20 matching lines @@
   return !touch_event_queue_.empty() ||
          !gesture_event_queue_.empty() ||
          !key_queue_.empty() ||
          mouse_move_pending_ ||
          mouse_wheel_pending_ ||
          select_message_pending_ ||
          move_caret_pending_;
 }
 
 }  // namespace content