Gamepad API: add support for connection events

content/renderer/gamepad_shared_memory_reader.h

 // Copyright (c) 2011 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_RENDERER_GAMEPAD_SHARED_MEMORY_READER_H_
 #define CONTENT_RENDERER_GAMEPAD_SHARED_MEMORY_READER_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/shared_memory.h"
+#include "content/common/gamepad_messages.h"
+#include "ipc/message_filter.h"
 #include "third_party/WebKit/public/platform/WebGamepads.h"
 
+namespace blink { class WebGamepadListener; }
+
 namespace content {
 
 struct GamepadHardwareBuffer;
 
-class GamepadSharedMemoryReader {
+class GamepadSharedMemoryReader : public IPC::MessageFilter {

[jam, 2014/05/05 21:19:09]

generally, you would implement an IPC::MessageFilter in a child process if you
want to dispatch IPCs on a thread other than the main thread. but here, you're
dispatching them on the IO thread and then posttask'ing to the main thread. so
they should just be dispatched there directly.

the way to do this for control IPCs is to derive from RenderProcessObserver and
override OnControlMessageReceived.

[kbalazs, 2014/05/06 22:20:34]

Done, indeed much better this way.

  public:
-  GamepadSharedMemoryReader();
+  GamepadSharedMemoryReader(
+      const scoped_refptr<base::MessageLoopProxy>& io_message_loop);
+  void SampleGamepads(blink::WebGamepads&);
+  void SetGamepadListener(blink::WebGamepadListener* listener);
+
+ protected:
   virtual ~GamepadSharedMemoryReader();
-  void SampleGamepads(blink::WebGamepads&);
 
  private:
+  void StartPollingIfNecessary();
+  void StopPollingIfNecessary();
+
+  // IPC::ChannelProxy::MessageFilter override. Called on |io_message_loop|.
+  virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
+
+  // Called when a gamepad is connected to the system
+  void OnGamepadConnected(int index, const blink::WebGamepad& gamepad);
+
+  // Called when a gamepad is disconnected from the system
+  void OnGamepadDisconnected(int index, const blink::WebGamepad& gamepad);
+
+  void DispatchGamepadConnected(int index, const blink::WebGamepad& gamepad);
+  void DispatchGamepadDisconnected(int index, const blink::WebGamepad& gamepad);
+
+  // Message loop on which IPC calls are driven.
+  const scoped_refptr<base::MessageLoopProxy> io_message_loop_;
+
+  // Main thread's message loop.
+  scoped_refptr<base::MessageLoopProxy> main_message_loop_;
+
   base::SharedMemoryHandle renderer_shared_memory_handle_;
   scoped_ptr<base::SharedMemory> renderer_shared_memory_;
   GamepadHardwareBuffer* gamepad_hardware_buffer_;
+  blink::WebGamepadListener* gamepad_listener_;
 
+  bool is_polling_;
   bool ever_interacted_with_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_GAMEPAD_SHARED_MEMORY_READER_H_