media/device_monitors/device_monitor_mac.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 MEDIA_DEVICE_MONITORS_DEVICE_MONITOR_MAC_H_
#define MEDIA_DEVICE_MONITORS_DEVICE_MONITOR_MAC_H_

#include <memory>

#include "base/macros.h"
#include "base/single_thread_task_runner.h"
#include "base/system/system_monitor.h"
#include "base/threading/thread_checker.h"
#include "media/base/media_export.h"

namespace {
class DeviceMonitorMacImpl;
}

namespace media {

// Class to track video devices removal or addition via callback to
// base::SystemMonitor ProcessDevicesChanged(). A single object of this class
// is created from the browser main process and lives as long as this one.
class MEDIA_EXPORT DeviceMonitorMac {
 public:
  // The |device_task_runner| argument represents the thread on which device
  // enumeration will occur.
  explicit DeviceMonitorMac(
      scoped_refptr<base::SingleThreadTaskRunner> device_task_runner);
  ~DeviceMonitorMac();

  // Registers the observers for the video device removal, connection and
  // suspension. The AVFoundation library is also loaded and initialised if the
  // OS supports it.
  void StartMonitoring();

  // Method called by the internal DeviceMonitorMacImpl object
  // |device_monitor_impl_| when a device of type |type| has been added to or
  // removed from the system. This code executes in the notification thread.
  void NotifyDeviceChanged(base::SystemMonitor::DeviceType type);

 private:
  scoped_refptr<base::SingleThreadTaskRunner> device_task_runner_;
  std::unique_ptr<DeviceMonitorMacImpl> device_monitor_impl_;

  // |thread_checker_| is used to check that constructor and StartMonitoring()
  // are called in the correct thread, the UI thread, that also owns the object.
  base::ThreadChecker thread_checker_;

  DISALLOW_COPY_AND_ASSIGN(DeviceMonitorMac);
};

}  // namespace media

#endif  // MEDIA_DEVICE_MONITORS_DEVICE_MONITOR_MAC_H_