Provided batched input delivery with a BufferedInputRouter

content/browser/renderer_host/input/input_queue.h

+// Copyright (c) 2013 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_INPUT_INPUT_QUEUE_H_
+#define CONTENT_BROWSER_RENDERER_HOST_INPUT_INPUT_QUEUE_H_
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "content/common/content_export.h"
+#include "content/common/input/input_event_disposition.h"
+
+namespace content {
+
+class BrowserInputEvent;
+class EventPacketAck;
+class InputQueueClient;
+
+// |InputQueue| handles browser input event batching and response.
+// Event packets are assembled into sequential event packets. A flush entails
+// delivery and dispatch of a single event packet, and continues until the
+// packet is ack'ed and all its events have been dispatched to the renderer.
+class CONTENT_EXPORT InputQueue {
+ public:
+  // The |client| should outlive the InputQueue.
+  InputQueue(InputQueueClient* client);
+  virtual ~InputQueue();
+
+  // If a flush is in progress, |event| will be dispatched in the next flush.
+  // If no flush is in progress, a flush will be requested if necessary.
+  // |event| is assumed to be both non-NULL and valid.
+  void QueueEvent(scoped_ptr<BrowserInputEvent> event);
+
+  // Initiates the flush of the pending event packet to |client_|, if necessary.
+  // This should only be called in response to |client_->SetNeedsFlush()|.
+  void BeginFlush();
+
+  // Called by the owner upon EventPacket responses from the sender target. This
+  // will dispatch event acks for events with a corresponding |ack_handler|.
+  enum AckResult {
+    ACK_OK,          // |acked_packet| was processed successfully.
+    ACK_UNEXPECTED,  // |acked_packet| was unexpected; no flush was in-progress.
+    ACK_INVALID,     // |acked_packet| contains invalid data.
+    ACK_SHUTDOWN     // |acked_packet| processing triggered queue shutdown.
+  };
+  AckResult OnEventPacketAck(int64 packet_id,
+                             const InputEventDispositions& dispositions);
+
+  // Total number of evenst in the queue, both being flushed and pending flush.
+  size_t QueuedEventCount() const;
+
+ protected:
+  friend class InputQueueTest;
+
+  // Delivers |in_flush_packet_| to the client.
+  void DeliverInFlushPacket();
+
+  // Requests a flush via |client_| if the necessary request has not been made.
+  void RequestFlushIfNecessary();
+
+  // True when |in_flush_packet_| is non-empty.
+  bool FlushInProgress() const;
+
+ private:
+  InputQueueClient* client_;
+
+  // Used to assign unique, non-zero ID's to each delivered EventPacket.
+  int64 next_packet_id_;
+
+  // Avoid spamming the client with redundant flush requests.
+  bool flush_requested_;
+
+  class BrowserEventPacket;
+  scoped_ptr<BrowserEventPacket> in_flush_packet_;
+  scoped_ptr<BrowserEventPacket> pending_flush_packet_;
+
+  DISALLOW_COPY_AND_ASSIGN(InputQueue);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_INPUT_QUEUE_H_