content/browser/renderer_host/input/touch_event_queue.h

   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 CONTENT_EXPORT 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 CONTENT_EXPORT TouchEventQueue {
  37  public:
  38
  39   // The |client| must outlive the TouchEventQueue.
  40   explicit TouchEventQueue(TouchEventQueueClient* client);
  41   ~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   // When GestureScrollBegin is received, we send a touch cancel to renderer,
  56   // route all the following touch events directly to client, and ignore the
  57   // ack for the touch cancel. When Gesture{ScrollEnd,FlingStart} is received,
  58   // resume the normal flow of sending touch events to the renderer.
  59   void OnGestureScrollEvent(const GestureEventWithLatencyInfo& gesture_event);
  60
  61   // Empties the queue of touch events. This may result in any number of gesture
  62   // events being sent to the renderer.
  63   void FlushQueue();
  64
  65   // Returns whether the currently pending touch event (waiting ACK) is for
  66   // a touch start event.
  67   bool IsPendingAckTouchStart() const;
  68
  69   // Sets whether a delayed touch ack will cancel and flush the current
  70   // touch sequence.
  71   void SetAckTimeoutEnabled(bool enabled, size_t ack_timeout_delay_ms);
  72
  73   bool empty() const WARN_UNUSED_RESULT {
  74     return touch_queue_.empty();
  75   }
  76
  77   size_t size() const {
  78     return touch_queue_.size();
  79   }
  80
  81   bool ack_timeout_enabled() const {
  82     return ack_timeout_enabled_;
  83   }
  84
  85  private:
  86   class TouchTimeoutHandler;
  87   friend class TouchTimeoutHandler;
  88   friend class TouchEventQueueTest;
  89
  90   bool HasTimeoutEvent() const;
  91   bool IsTimeoutRunningForTesting() const;
  92   const TouchEventWithLatencyInfo& GetLatestEventForTesting() const;
  93
  94   // Walks the queue, checking each event for |ShouldForwardToRenderer()|.
  95   // If true, forwards the touch event and stops processing further events.
  96   // If false, acks the event with |INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS|.
  97   void TryForwardNextEventToRenderer();
  98
  99   // Pops the touch-event from the top of the queue and sends it to the
 100   // TouchEventQueueClient. This reduces the size of the queue by one.
 101   void PopTouchEventToClient(InputEventAckState ack_result,
 102                              const ui::LatencyInfo& renderer_latency_info);
 103
 104   bool ShouldForwardToRenderer(const blink::WebTouchEvent& event) const;
 105   void ForwardToRenderer(const TouchEventWithLatencyInfo& event);
 106   void UpdateTouchAckStates(const blink::WebTouchEvent& event,
 107                             InputEventAckState ack_result);
 108
 109
 110   // Handles touch event forwarding and ack'ed event dispatch.
 111   TouchEventQueueClient* client_;
 112
 113   typedef std::deque<CoalescedWebTouchEvent*> TouchQueue;
 114   TouchQueue touch_queue_;
 115
 116   // Maintain the ACK status for each touch point.
 117   typedef std::map<int, InputEventAckState> TouchPointAckStates;
 118   TouchPointAckStates touch_ack_states_;
 119
 120   // Used to defer touch forwarding when ack dispatch triggers |QueueEvent()|.
 121   // If not NULL, |dispatching_touch_ack_| is the touch event of which the ack
 122   // is being dispatched.
 123   CoalescedWebTouchEvent* dispatching_touch_ack_;
 124
 125   // Used to prevent touch timeout scheduling if we receive a synchronous
 126   // ack after forwarding a touch event to the client.
 127   bool dispatching_touch_;
 128
 129   // Don't send touch events to the renderer while scrolling.
 130   bool no_touch_to_renderer_;
 131
 132   // Whether an event in the current (multi)touch sequence was consumed by the
 133   // renderer.  The touch timeout will never be activated when this is true.
 134   bool renderer_is_consuming_touch_gesture_;
 135
 136   // Optional handler for timed-out touch event acks, disabled by default.
 137   bool ack_timeout_enabled_;
 138   scoped_ptr<TouchTimeoutHandler> timeout_handler_;
 139
 140   DISALLOW_COPY_AND_ASSIGN(TouchEventQueue);
 141 };
 142
 143 }  // namespace content
 144
 145 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EVENT_QUEUE_H_