src/content/browser/renderer_host/input/touch_disposition_gesture_filter.h

   1 // Copyright 2014 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_DISPOSITION_GESTURE_FILTER_H_
   6 #define CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_DISPOSITION_GESTURE_FILTER_H_
   7
   8 #include <queue>
   9 #include <set>
  10
  11 #include "content/browser/renderer_host/input/gesture_event_packet.h"
  12 #include "content/common/content_export.h"
  13 #include "content/port/common/input_event_ack_state.h"
  14 #include "third_party/WebKit/public/web/WebInputEvent.h"
  15
  16 namespace content {
  17
  18 // Interface with which the |TouchDispositionGestureFilter| forwards gestures
  19 // for a given touch event.
  20 class CONTENT_EXPORT TouchDispositionGestureFilterClient {
  21  public:
  22   virtual void ForwardGestureEvent(const blink::WebGestureEvent&) = 0;
  23 };
  24
  25 // Given a stream of touch-derived gesture packets, produces a refined gesture
  26 // sequence based on the ack dispositions of the generating touch events.
  27 class CONTENT_EXPORT TouchDispositionGestureFilter {
  28  public:
  29   explicit TouchDispositionGestureFilter(
  30       TouchDispositionGestureFilterClient* client);
  31   ~TouchDispositionGestureFilter();
  32
  33   // To be called upon production of touch-derived gestures by the platform,
  34   // *prior* to the generating touch being forward to the renderer.  In
  35   // particular, |packet| contains [0, n] gestures that correspond to a given
  36   // touch event. It is imperative that a single packet is received for
  37   // *each* touch event, even those that did not produce a gesture.
  38   enum PacketResult {
  39     SUCCESS,              // Packet successfully queued.
  40     INVALID_PACKET_ORDER, // Packets were received in the wrong order, i.e.,
  41                           // TOUCH_BEGIN should always precede other packets.
  42     INVALID_PACKET_TYPE,  // Packet had an invalid type.
  43   };
  44   PacketResult OnGestureEventPacket(const GestureEventPacket& packet);
  45
  46   // To be called upon receipt of *all* touch event acks.
  47   void OnTouchEventAck(InputEventAckState ack_state);
  48
  49   // Whether there are any active gesture sequences still queued in the filter.
  50   bool IsEmpty() const;
  51
  52  private:
  53   // Utility class for tracking gesture events and dispositions for a single
  54   // gesture sequence. A single sequence corresponds to all gestures created
  55   // between the first finger down and the last finger up, including gestures
  56   // generated by timeouts from a statinoary finger.
  57   class GestureSequence {
  58    public:
  59     struct GestureHandlingState {
  60       GestureHandlingState();
  61       // True iff the sequence has had at least one touch acked.
  62       bool seen_ack;
  63       // True iff the sequence has had any touch down event consumed.
  64       bool start_consumed;
  65       // True iff the first ack received for this sequence reported that no
  66       // consumer exists.
  67       bool no_consumer;
  68     };
  69
  70     GestureSequence();
  71     ~GestureSequence();
  72
  73     void Push(const GestureEventPacket& packet);
  74     void Pop();
  75     const GestureEventPacket& Front() const;
  76     void UpdateState(GestureEventPacket::GestureSource gesture_source,
  77                      InputEventAckState ack_state);
  78     bool IsEmpty() const;
  79     const GestureHandlingState& state() const { return state_; };
  80
  81    private:
  82     std::queue<GestureEventPacket> packets_;
  83     GestureHandlingState state_;
  84   };
  85   bool IsGesturePrevented(blink::WebInputEvent::Type type,
  86                           InputEventAckState current,
  87                           const GestureSequence::GestureHandlingState& state)
  88       const;
  89
  90   void UpdateAndDispatchPackets(GestureSequence* sequence,
  91                                 InputEventAckState ack_result);
  92
  93   void FilterAndSendPacket(
  94       const GestureEventPacket& packet,
  95       const GestureSequence::GestureHandlingState& sequence_state,
  96       InputEventAckState ack_state);
  97
  98   void SendGesture(const blink::WebGestureEvent& gesture);
  99   void CancelTapIfNecessary();
 100   void CancelFlingIfNecessary();
 101   GestureSequence& Head();
 102   GestureSequence& Tail();
 103
 104   TouchDispositionGestureFilterClient* client_;
 105   std::queue<GestureSequence> sequences_;
 106
 107   // If the previous gesture of a given type was dropped instead of being
 108   // dispatched, its type will occur in this set. Cleared when a new touch
 109   // sequence begins to be acked.
 110   std::set<blink::WebInputEvent::Type> last_event_of_type_dropped_;
 111
 112   // Bookkeeping for inserting synthetic Gesture{Tap,Fling}Cancel events
 113   // when necessary, e.g., GestureTapCancel when scrolling begins, or
 114   // GestureFlingCancel when a user taps following a GestureFlingStart.
 115   bool needs_tap_ending_event_;
 116   bool needs_fling_ending_event_;
 117
 118   DISALLOW_COPY_AND_ASSIGN(TouchDispositionGestureFilter);
 119 };
 120
 121 }  // namespace content
 122
 123 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_DISPOSITION_GESTURE_FILTER_H_