Allow repeated handler removal/addition with the TouchEventQueue

content/browser/renderer_host/input/touch_event_queue.h

 // 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.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EVENT_QUEUE_H_
 #define CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EVENT_QUEUE_H_
 
 #include <deque>
 #include <map>
 
 #include "base/basictypes.h"
 #include "base/time/time.h"
 #include "content/browser/renderer_host/event_with_latency_info.h"
 #include "content/common/content_export.h"
 #include "content/common/input/input_event_ack_state.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
+#include "ui/events/gesture_detection/bitset_32.h"
 #include "ui/gfx/geometry/point_f.h"
 
 namespace content {
 
 class CoalescedWebTouchEvent;
 
 // Interface with which TouchEventQueue can forward touch events, and dispatch
 // touch event responses.
 class CONTENT_EXPORT TouchEventQueueClient {
  public:
@@ skipping 80 matching lines @@
 
   // Returns whether the currently pending touch event (waiting ACK) is for
   // a touch start event.
   bool IsPendingAckTouchStart() const;
 
   // Sets whether a delayed touch ack will cancel and flush the current
   // touch sequence. Note that, if the timeout was previously disabled, enabling
   // it will take effect only for the following touch sequence.
   void SetAckTimeoutEnabled(bool enabled);
 
+  bool IsAckTimeoutEnabled() const;
+
+  bool IsForwardingTouches();
+
   bool empty() const WARN_UNUSED_RESULT {
     return touch_queue_.empty();
   }
 
   size_t size() const {
     return touch_queue_.size();
   }
 
-  bool ack_timeout_enabled() const {
-    return ack_timeout_enabled_;
-  }
-
-  bool has_handlers() const {
-    return touch_filtering_state_ != DROP_ALL_TOUCHES;
-  }
+  bool has_handlers() const { return has_handlers_; }
 
  private:
   class TouchTimeoutHandler;
   class TouchMoveSlopSuppressor;
   friend class TouchTimeoutHandler;
   friend class TouchEventQueueTest;
 
   bool HasPendingAsyncTouchMoveForTesting() const;
   bool IsTimeoutRunningForTesting() const;
   const TouchEventWithLatencyInfo& GetLatestEventForTesting() const;
@@ skipping 30 matching lines @@
 
   enum PreFilterResult {
     ACK_WITH_NO_CONSUMER_EXISTS,
     ACK_WITH_NOT_CONSUMED,
     FORWARD_TO_RENDERER,
   };
   // Filter touches prior to forwarding to the renderer, e.g., if the renderer
   // has no touch handler.
   PreFilterResult FilterBeforeForwarding(const blink::WebTouchEvent& event);
   void ForwardToRenderer(const TouchEventWithLatencyInfo& event);
-  void UpdateTouchAckStates(const blink::WebTouchEvent& event,
-                            InputEventAckState ack_result);
-  bool AllTouchAckStatesHaveState(InputEventAckState ack_state) const;
-
+  void UpdateTouchConsumerStates(const blink::WebTouchEvent& event,
+                                 InputEventAckState ack_result);
 
   // Handles touch event forwarding and ack'ed event dispatch.
   TouchEventQueueClient* client_;
 
   typedef std::deque<CoalescedWebTouchEvent*> TouchQueue;
   TouchQueue touch_queue_;
 
-  // Maintain the ACK status for each touch point.
-  typedef std::map<int, InputEventAckState> TouchPointAckStates;
-  TouchPointAckStates touch_ack_states_;
+  // Maps whether each active pointer has a consumer (i.e., a touch point has a
+  // valid consumer iff |touch_consumer_states[pointer.id]| is true.).
+  ui::BitSet32 touch_consumer_states_;

[Rick Byers, 2014/09/19 17:54:07]

I wonder if we could simplify this further by keeping track only of whether
_any_ touch point has a consumer.  Blink already has to deal with getting events
for touch points it didn't know were down.

[jdduke (slow), 2014/09/22 16:30:14]

Hmm, interesting, that is a tempting simplification, though I hesitate to to it
in this bug fix as we've had per-pointer filtering for as long as I can
remember. I'll add a TODO here and play with it as a follow-up.

 
   // Position of the first touch in the most recent sequence forwarded to the
   // client.
   gfx::PointF touch_sequence_start_position_;
 
   // Used to defer touch forwarding when ack dispatch triggers |QueueEvent()|.
   // If not NULL, |dispatching_touch_ack_| is the touch event of which the ack
   // is being dispatched.
   const CoalescedWebTouchEvent* dispatching_touch_ack_;
 
   // Used to prevent touch timeout scheduling if we receive a synchronous
   // ack after forwarding a touch event to the client.
   bool dispatching_touch_;
 
-  enum TouchFilteringState {
-    FORWARD_ALL_TOUCHES,           // Don't filter at all - the default.
-    FORWARD_TOUCHES_UNTIL_TIMEOUT, // Don't filter unless we get an ACK timeout.
-    DROP_TOUCHES_IN_SEQUENCE,      // Filter all events until a new touch
-                                   // sequence is received.
-    DROP_ALL_TOUCHES,              // Filter all events, e.g., no touch handler.
-    TOUCH_FILTERING_STATE_DEFAULT = FORWARD_ALL_TOUCHES,
-  };
-  TouchFilteringState touch_filtering_state_;
+  // Whether the renderer has at least one touch handler.
+  bool has_handlers_;
+
+  // Whether to allow any remaining touches for the current sequence. Note that
+  // this is a stricter condition than an empty |touch_consumer_states|, as it
+  // also prevents forwarding of touchstart events for new pointers in the
+  // current sequence. This is only used when the event is synthetically
+  // cancelled after a touch timeout, or after a scroll event when the
+  // mode is TOUCH_SCROLLING_MODE_TOUCHCANCEL.
+  bool drop_remaining_touches_in_sequence_;
 
   // Optional handler for timed-out touch event acks.
-  bool ack_timeout_enabled_;
   scoped_ptr<TouchTimeoutHandler> timeout_handler_;
 
   // Suppression of TouchMove's within a slop region when a sequence has not yet
   // been preventDefaulted.
   scoped_ptr<TouchMoveSlopSuppressor> touchmove_slop_suppressor_;
 
   // Whether touch events should remain buffered and dispatched asynchronously
   // while a scroll sequence is active.  In this mode, touchmove's are throttled
   // and ack'ed immediately, but remain buffered in |pending_async_touchmove_|
   // until a sufficient time period has elapsed since the last sent touch event.
   // For details see the design doc at http://goo.gl/lVyJAa.
   bool send_touch_events_async_;
   bool needs_async_touchmove_for_outer_slop_region_;
   scoped_ptr<TouchEventWithLatencyInfo> pending_async_touchmove_;
   double last_sent_touch_timestamp_sec_;
 
   // How touch events are handled during scrolling.  For now this is a global
   // setting for experimentation, but we may evolve it into an app-controlled
   // mode.
   const TouchScrollingMode touch_scrolling_mode_;
 
   DISALLOW_COPY_AND_ASSIGN(TouchEventQueue);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EVENT_QUEUE_H_