Gamepad API: add support for connection events

content/browser/gamepad/gamepad_service.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_GAMEPAD_GAMEPAD_SERVICE_H
 #define CONTENT_BROWSER_GAMEPAD_GAMEPAD_SERVICE_H
 
+#include <set>
+
 #include "base/basictypes.h"
 #include "base/callback_forward.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/shared_memory.h"
 #include "base/memory/singleton.h"
 #include "base/threading/thread_checker.h"
 #include "content/common/content_export.h"
 
+namespace blink {
+class WebGamepad;
+}
+
 namespace content {
 
+class GamepadConsumer;
 class GamepadDataFetcher;
 class GamepadProvider;
 class GamepadServiceTestConstructor;
 class RenderProcessHost;
 
 // Owns the GamepadProvider (the background polling thread) and keeps track of
 // the number of consumers currently using the data (and pausing the provider
 // when not in use).
 class CONTENT_EXPORT GamepadService {
  public:
   // Returns the GamepadService singleton.
   static GamepadService* GetInstance();
 
   // Increments the number of users of the provider. The Provider is running
   // when there's > 0 users, and is paused when the count drops to 0.
+  // consumer is registered to listen for gamepad connections. If this is the
+  // first time it is added to the set of consumers it will be treated
+  // specially: it will not be informed about connections before a new user
+  // gesture is observed at which point it will be notified for every connected
+  // gamepads.
   //
   // Must be called on the I/O thread.
-  void AddConsumer();
+  void ConsumerBecameActive(GamepadConsumer* consumer);
 
-  // Removes a consumer. Should be matched with an AddConsumer call.
+  // Decrements the number of users of the provider. consumer will not be
+  // informed about connections until it's added back via ConsumerBecameActive.
+  // Must be matched with a ConsumerBecameActive call.
   //
   // Must be called on the I/O thread.
-  void RemoveConsumer();
+  void ConsumerBecameInactive(GamepadConsumer* consumer);
+
+  // Decrements the number of users of the provider and removes consumer from
+  // the set of consumers. Should be matched with a a ConsumerBecameActive
+  // call.
+  //
+  // Must be called on the I/O thread.
+  void RemoveConsumer(GamepadConsumer* consumer);
 
   // Registers the given closure for calling when the user has interacted with
   // the device. This callback will only be issued once. Should only be called
   // while a consumer is active.
   void RegisterForUserGesture(const base::Closure& closure);
 
   // Returns the shared memory handle of the gamepad data duplicated into the
   // given process.
   base::SharedMemoryHandle GetSharedMemoryHandleForProcess(
       base::ProcessHandle handle);
 
   // Stop/join with the background thread in GamepadProvider |provider_|.
   void Terminate();
 
+  // Called on IO thread when a gamepad is connected.
+  void OnGamepadConnected(int index, const blink::WebGamepad& pad);
+
+  // Called on IO thread when a gamepad is disconnected.
+  void OnGamepadDisconnected(int index, const blink::WebGamepad& pad);
+
  private:
   friend struct DefaultSingletonTraits<GamepadService>;
   friend class GamepadServiceTestConstructor;
 
   GamepadService();
 
   // Constructor for testing. This specifies the data fetcher to use for a
   // provider, bypassing the default platform one.
   GamepadService(scoped_ptr<GamepadDataFetcher> fetcher);
 
   virtual ~GamepadService();
 
-  int num_readers_;
+  void OnUserGesture();
+
+  struct ConsumerInfo {
+    ConsumerInfo(GamepadConsumer* consumer)
+      : consumer(consumer),
+        did_observe_user_gesture(false) {
+    }
+
+    bool operator<(const ConsumerInfo& other) const {
+      return consumer < other.consumer;
+    }
+
+    GamepadConsumer* consumer;
+    mutable bool is_active;
+    mutable bool did_observe_user_gesture;
+  };
+
   scoped_ptr<GamepadProvider> provider_;
 
   base::ThreadChecker thread_checker_;
 
+  typedef std::set<ConsumerInfo> ConsumerSet;
+  ConsumerSet consumers_;
+
+  int num_active_consumers_;
+
+  bool gesture_callback_pending_;
+
   DISALLOW_COPY_AND_ASSIGN(GamepadService);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_GAMEPAD_GAMEPAD_SERVICE_H_