1 files changed, 83 insertions, 0 deletions
diff --git a/accessible/base/EventQueue.h b/accessible/base/EventQueue.h
new file mode 100644
index 0000000000..87bcf89340
--- /dev/null
+++ b/accessible/base/EventQueue.h
@@ -0,0 +1,83 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_a11y_EventQueue_h_
+#define mozilla_a11y_EventQueue_h_
+
+#include "AccEvent.h"
+#include "mozilla/Assertions.h"
+
+namespace mozilla {
+namespace a11y {
+
+class DocAccessible;
+
+/**
+ * Used to organize and coalesce pending events.
+ */
+class EventQueue {
+ protected:
+  explicit EventQueue(DocAccessible* aDocument) : mDocument(aDocument) {
+    MOZ_ASSERT(mDocument,
+               "There's no point creating an event queue for a null document");
+  }
+
+  /**
+   * Put an accessible event into the queue to process it later.
+   */
+  bool PushEvent(AccEvent* aEvent);
+
+  /**
+   * Puts name and/or description change events into the queue, if needed.
+   */
+  bool PushNameOrDescriptionChange(AccEvent* aOrigEvent);
+
+  /**
+   * Process events from the queue and fires events.
+   */
+  void ProcessEventQueue();
+
+ private:
+  EventQueue(const EventQueue&) = delete;
+  EventQueue& operator=(const EventQueue&) = delete;
+
+  // Event queue processing
+  /**
+   * Coalesce redundant events from the queue.
+   */
+  void CoalesceEvents();
+
+  /**
+   * Coalesce events from the same subtree.
+   */
+  void CoalesceReorderEvents(AccEvent* aTailEvent);
+
+  /**
+   * Coalesce two selection change events within the same select control.
+   */
+  void CoalesceSelChangeEvents(AccSelChangeEvent* aTailEvent,
+                               AccSelChangeEvent* aThisEvent,
+                               uint32_t aThisIndex);
+
+ protected:
+  /**
+   * The document accessible reference owning this queue.
+   */
+  DocAccessible* mDocument;
+
+  /**
+   * Pending events array. Don't make this an AutoTArray; we use
+   * SwapElements() on it.
+   */
+  nsTArray<RefPtr<AccEvent>> mEvents;
+
+  // Pending focus event.
+  RefPtr<AccEvent> mFocusEvent;
+};
+
+}  // namespace a11y
+}  // namespace mozilla
+
+#endif  // mozilla_a11y_EventQueue_h_