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      1 // Copyright 2013 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EVENT_QUEUE_H_
      6 #define CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EVENT_QUEUE_H_
      7 
      8 #include <deque>
      9 #include <map>
     10 
     11 #include "base/basictypes.h"
     12 #include "content/common/content_export.h"
     13 #include "content/port/browser/event_with_latency_info.h"
     14 #include "content/port/common/input_event_ack_state.h"
     15 #include "third_party/WebKit/public/web/WebInputEvent.h"
     16 
     17 namespace content {
     18 
     19 class CoalescedWebTouchEvent;
     20 
     21 // Interface with which TouchEventQueue can forward touch events, and dispatch
     22 // touch event responses.
     23 class TouchEventQueueClient {
     24  public:
     25   virtual ~TouchEventQueueClient() {}
     26 
     27   virtual void SendTouchEventImmediately(
     28       const TouchEventWithLatencyInfo& event) = 0;
     29 
     30   virtual void OnTouchEventAck(
     31       const TouchEventWithLatencyInfo& event,
     32       InputEventAckState ack_result) = 0;
     33 };
     34 
     35 // A queue for throttling and coalescing touch-events.
     36 class TouchEventQueue {
     37  public:
     38 
     39   // The |client| must outlive the TouchEventQueue.
     40   explicit TouchEventQueue(TouchEventQueueClient* client);
     41   virtual ~TouchEventQueue();
     42 
     43   // Adds an event to the queue. The event may be coalesced with previously
     44   // queued events (e.g. consecutive touch-move events can be coalesced into a
     45   // single touch-move event). The event may also be immediately forwarded to
     46   // the renderer (e.g. when there are no other queued touch event).
     47   void QueueEvent(const TouchEventWithLatencyInfo& event);
     48 
     49   // Notifies the queue that a touch-event has been processed by the renderer.
     50   // At this point, the queue may send one or more gesture events and/or
     51   // additional queued touch-events to the renderer.
     52   void ProcessTouchAck(InputEventAckState ack_result,
     53                        const ui::LatencyInfo& latency_info);
     54 
     55   // Empties the queue of touch events. This may result in any number of gesture
     56   // events being sent to the renderer.
     57   void FlushQueue();
     58 
     59   // Returns whether the event-queue is empty.
     60   bool empty() const WARN_UNUSED_RESULT {
     61     return touch_queue_.empty();
     62   }
     63 
     64  private:
     65   friend class MockRenderWidgetHost;
     66   friend class ImmediateInputRouterTest;
     67 
     68   CONTENT_EXPORT size_t GetQueueSize() const;
     69   CONTENT_EXPORT const TouchEventWithLatencyInfo& GetLatestEvent() const;
     70 
     71   // Pops the touch-event from the top of the queue and sends it to the
     72   // TouchEventQueueClient. This reduces the size of the queue by one.
     73   void PopTouchEventToClient(InputEventAckState ack_result,
     74                              const ui::LatencyInfo& renderer_latency_info);
     75 
     76   bool ShouldForwardToRenderer(const WebKit::WebTouchEvent& event) const;
     77 
     78   // Handles touch event forwarding and ack'ed event dispatch.
     79   TouchEventQueueClient* client_;
     80 
     81   typedef std::deque<CoalescedWebTouchEvent*> TouchQueue;
     82   TouchQueue touch_queue_;
     83 
     84   // Maintain the ACK status for each touch point.
     85   typedef std::map<int, InputEventAckState> TouchPointAckStates;
     86   TouchPointAckStates touch_ack_states_;
     87 
     88   // Used to defer touch forwarding when ack dispatch triggers |QueueEvent()|.
     89   bool dispatching_touch_ack_;
     90 
     91   DISALLOW_COPY_AND_ASSIGN(TouchEventQueue);
     92 };
     93 
     94 }  // namespace content
     95 
     96 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EVENT_QUEUE_H_
     97