accessible/base/EventQueue.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #ifndef mozilla_a11y_EventQueue_h_
   7 #define mozilla_a11y_EventQueue_h_
   8
   9 #include "AccEvent.h"
  10
  11 namespace mozilla {
  12 namespace a11y {
  13
  14 class DocAccessible;
  15
  16 /**
  17  * Used to organize and coalesce pending events.
  18  */
  19 class EventQueue {
  20  protected:
  21   explicit EventQueue(DocAccessible* aDocument) : mDocument(aDocument) {}
  22
  23   /**
  24    * Put an accessible event into the queue to process it later.
  25    */
  26   bool PushEvent(AccEvent* aEvent);
  27
  28   /**
  29    * Puts name and/or description change events into the queue, if needed.
  30    */
  31   bool PushNameOrDescriptionChange(LocalAccessible* aTarget);
  32
  33   /**
  34    * Process events from the queue and fires events.
  35    */
  36   void ProcessEventQueue();
  37
  38  private:
  39   EventQueue(const EventQueue&) = delete;
  40   EventQueue& operator=(const EventQueue&) = delete;
  41
  42   // Event queue processing
  43   /**
  44    * Coalesce redundant events from the queue.
  45    */
  46   void CoalesceEvents();
  47
  48   /**
  49    * Coalesce events from the same subtree.
  50    */
  51   void CoalesceReorderEvents(AccEvent* aTailEvent);
  52
  53   /**
  54    * Coalesce two selection change events within the same select control.
  55    */
  56   void CoalesceSelChangeEvents(AccSelChangeEvent* aTailEvent,
  57                                AccSelChangeEvent* aThisEvent,
  58                                uint32_t aThisIndex);
  59
  60  protected:
  61   /**
  62    * The document accessible reference owning this queue.
  63    */
  64   DocAccessible* mDocument;
  65
  66   /**
  67    * Pending events array. Don't make this an AutoTArray; we use
  68    * SwapElements() on it.
  69    */
  70   nsTArray<RefPtr<AccEvent>> mEvents;
  71 };
  72
  73 }  // namespace a11y
  74 }  // namespace mozilla
  75
  76 #endif  // mozilla_a11y_EventQueue_h_