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+/* -*- 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"
+
+namespace mozilla {
+namespace a11y {
+
+class DocAccessible;
+
+/**
+ * Used to organize and coalesce pending events.
+ */
+class EventQueue {
+ protected:
+ explicit EventQueue(DocAccessible* aDocument) : mDocument(aDocument) {}
+
+ /**
+ * 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_