touch-event queue: Add a touch-event queue for all platforms.

content/browser/renderer_host/touch_event_queue.h

+// Copyright (c) 2012 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_TOUCH_EVENT_QUEUE_H_
+#define CONTENT_BROWSER_RENDERER_HOST_TOUCH_EVENT_QUEUE_H_
+
+#include <deque>
+
+#include "base/basictypes.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebInputEvent.h"
+
+namespace content {
+
+class RenderWidgetHostImpl;
+
+// A queue for throttling and coalescing touch-events.
+class TouchEventQueue {
+ public:
+  explicit TouchEventQueue(RenderWidgetHostImpl* host);
+  virtual ~TouchEventQueue();
+
+  // Adds an event to the queue. The event may be coalesced with previously
+  // queued events (e.g. consecutive touch-move events can be coalesced into a
+  // single touch-move event). The event may also be immediately forwarded to
+  // the renderer (e.g. when there are no other queued touch event).
+  void QueueEvent(const WebKit::WebTouchEvent& event);
+
+  // Notifies the queue that a touch-event has been processed by the renderer.
+  // At this point, the queue may send one or more gesture events and/or
+  // additional queued touch-events to the renderer.
+  void ProcessTouchAck(bool processed);
+
+ private:
+  // The RenderWidgetHost that owns this event-queue.
+  RenderWidgetHostImpl* render_widget_host_;
+
+  typedef std::deque<WebKit::WebTouchEvent> TouchQueue;
+  TouchQueue touch_queue_;
+
+  DISALLOW_COPY_AND_ASSIGN(TouchEventQueue);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_TOUCH_EVENT_QUEUE_H_