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   // Notifies the queue whether the renderer has at least one touch handler.
  62   void OnHasTouchEventHandlers(bool has_handlers);
  63
  64   // Returns whether the currently pending touch event (waiting ACK) is for
  65   // a touch start event.
  66   bool IsPendingAckTouchStart() const;
  67
  68   // Sets whether a delayed touch ack will cancel and flush the current
  69   // touch sequence.
  70   void SetAckTimeoutEnabled(bool enabled, size_t ack_timeout_delay_ms);
  71
  72   bool empty() const WARN_UNUSED_RESULT {
  73     return touch_queue_.empty();
  74   }
  75
  76   size_t size() const {
  77     return touch_queue_.size();
  78   }
  79
  80   bool ack_timeout_enabled() const {
  81     return ack_timeout_enabled_;
  82   }
  83
  84   bool has_handlers() const {
  85     return has_handlers_;
  86   }
  87
  88  private:
  89   class TouchTimeoutHandler;
  90   friend class TouchTimeoutHandler;
  91   friend class TouchEventQueueTest;
  92
  93   bool HasTimeoutEvent() const;
  94   bool IsTimeoutRunningForTesting() const;
  95   const TouchEventWithLatencyInfo& GetLatestEventForTesting() const;
  96
  97   // Empties the queue of touch events. This may result in any number of gesture
  98   // events being sent to the renderer.
  99   void FlushQueue();
 100
 101   // Walks the queue, checking each event for |ShouldForwardToRenderer()|.
 102   // If true, forwards the touch event and stops processing further events.
 103   // If false, acks the event with |INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS|.
 104   void TryForwardNextEventToRenderer();
 105
 106   // Pops the touch-event from the top of the queue and sends it to the
 107   // TouchEventQueueClient. This reduces the size of the queue by one.
 108   void PopTouchEventToClient(InputEventAckState ack_result,
 109                              const ui::LatencyInfo& renderer_latency_info);
 110
 111   bool ShouldForwardToRenderer(const blink::WebTouchEvent& event) const;
 112   void ForwardToRenderer(const TouchEventWithLatencyInfo& event);
 113   void UpdateTouchAckStates(const blink::WebTouchEvent& event,
 114                             InputEventAckState ack_result);
 115
 116
 117   // Handles touch event forwarding and ack'ed event dispatch.
 118   TouchEventQueueClient* client_;
 119
 120   typedef std::deque<CoalescedWebTouchEvent*> TouchQueue;
 121   TouchQueue touch_queue_;
 122
 123   // Maintain the ACK status for each touch point.
 124   typedef std::map<int, InputEventAckState> TouchPointAckStates;
 125   TouchPointAckStates touch_ack_states_;
 126
 127   // Used to defer touch forwarding when ack dispatch triggers |QueueEvent()|.
 128   // If not NULL, |dispatching_touch_ack_| is the touch event of which the ack
 129   // is being dispatched.
 130   CoalescedWebTouchEvent* dispatching_touch_ack_;
 131
 132   // Used to prevent touch timeout scheduling if we receive a synchronous
 133   // ack after forwarding a touch event to the client.
 134   bool dispatching_touch_;
 135
 136   // Whether there are any registered touch handlers. Defaults to false.
 137   bool has_handlers_;
 138
 139   // Don't send touch events to the renderer while scrolling.
 140   bool scroll_in_progress_;
 141
 142   // Whether an event in the current (multi)touch sequence was consumed by the
 143   // renderer.  The touch timeout will never be activated when this is true.
 144   bool renderer_is_consuming_touch_gesture_;
 145
 146   // Optional handler for timed-out touch event acks, disabled by default.
 147   bool ack_timeout_enabled_;
 148   scoped_ptr<TouchTimeoutHandler> timeout_handler_;
 149
 150   DISALLOW_COPY_AND_ASSIGN(TouchEventQueue);
 151 };
 152
 153 }  // namespace content
 154
 155 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EVENT_QUEUE_H_