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 #include "mozilla/Assertions.h"
  11
  12 namespace mozilla {
  13 namespace a11y {
  14
  15 class DocAccessible;
  16
  17 /**
  18  * Used to organize and coalesce pending events.
  19  */
  20 class EventQueue {
  21  protected:
  22   explicit EventQueue(DocAccessible* aDocument) : mDocument(aDocument) {
  23     MOZ_ASSERT(mDocument,
  24                "There's no point creating an event queue for a null document");
  25   }
  26
  27   /**
  28    * Put an accessible event into the queue to process it later.
  29    */
  30   bool PushEvent(AccEvent* aEvent);
  31
  32   /**
  33    * Puts name and/or description change events into the queue, if needed.
  34    */
  35   bool PushNameOrDescriptionChange(AccEvent* aOrigEvent);
  36
  37   /**
  38    * Process events from the queue and fires events.
  39    */
  40   void ProcessEventQueue();
  41
  42  private:
  43   EventQueue(const EventQueue&) = delete;
  44   EventQueue& operator=(const EventQueue&) = delete;
  45
  46   // Event queue processing
  47   /**
  48    * Coalesce redundant events from the queue.
  49    */
  50   void CoalesceEvents();
  51
  52   /**
  53    * Coalesce events from the same subtree.
  54    */
  55   void CoalesceReorderEvents(AccEvent* aTailEvent);
  56
  57   /**
  58    * Coalesce two selection change events within the same select control.
  59    */
  60   void CoalesceSelChangeEvents(AccSelChangeEvent* aTailEvent,
  61                                AccSelChangeEvent* aThisEvent,
  62                                uint32_t aThisIndex);
  63
  64  protected:
  65   /**
  66    * The document accessible reference owning this queue.
  67    */
  68   DocAccessible* mDocument;
  69
  70   /**
  71    * Pending events array. Don't make this an AutoTArray; we use
  72    * SwapElements() on it.
  73    */
  74   nsTArray<RefPtr<AccEvent>> mEvents;
  75
  76   // Pending focus event.
  77   RefPtr<AccEvent> mFocusEvent;
  78 };
  79
  80 }  // namespace a11y
  81 }  // namespace mozilla
  82
  83 #endif  // mozilla_a11y_EventQueue_h_