base/system_monitor/system_monitor.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_SYSTEM_MONITOR_SYSTEM_MONITOR_H_
   6 #define BASE_SYSTEM_MONITOR_SYSTEM_MONITOR_H_
   7
   8 #include "base/base_export.h"
   9 #include "base/basictypes.h"
  10 #include "base/memory/ref_counted.h"
  11 #include "base/observer_list_threadsafe.h"
  12 #include "build/build_config.h"
  13
  14 namespace base {
  15
  16 // Class for monitoring various system-related subsystems
  17 // such as power management, network status, etc.
  18 // TODO(mbelshe):  Add support beyond just power management.
  19 class BASE_EXPORT SystemMonitor {
  20  public:
  21   // Type of devices whose change need to be monitored, such as add/remove.
  22   enum DeviceType {
  23     DEVTYPE_AUDIO_CAPTURE,  // Audio capture device, e.g., microphone.
  24     DEVTYPE_VIDEO_CAPTURE,  // Video capture device, e.g., webcam.
  25     DEVTYPE_UNKNOWN,  // Other devices.
  26   };
  27
  28   // Create SystemMonitor. Only one SystemMonitor instance per application
  29   // is allowed.
  30   SystemMonitor();
  31   ~SystemMonitor();
  32
  33   // Get the application-wide SystemMonitor (if not present, returns NULL).
  34   static SystemMonitor* Get();
  35
  36   class BASE_EXPORT DevicesChangedObserver {
  37    public:
  38     // Notification that the devices connected to the system have changed.
  39     // This is only implemented on Windows currently.
  40     virtual void OnDevicesChanged(DeviceType device_type) {}
  41
  42    protected:
  43     virtual ~DevicesChangedObserver() {}
  44   };
  45
  46   // Add a new observer.
  47   // Can be called from any thread.
  48   // Must not be called from within a notification callback.
  49   void AddDevicesChangedObserver(DevicesChangedObserver* obs);
  50
  51   // Remove an existing observer.
  52   // Can be called from any thread.
  53   // Must not be called from within a notification callback.
  54   void RemoveDevicesChangedObserver(DevicesChangedObserver* obs);
  55
  56   // The ProcessFoo() style methods are a broken pattern and should not
  57   // be copied. Any significant addition to this class is blocked on
  58   // refactoring to improve the state of affairs. See http://crbug.com/149059
  59
  60   // Cross-platform handling of a device change event.
  61   void ProcessDevicesChanged(DeviceType device_type);
  62
  63  private:
  64   // Functions to trigger notifications.
  65   void NotifyDevicesChanged(DeviceType device_type);
  66
  67   scoped_refptr<ObserverListThreadSafe<DevicesChangedObserver> >
  68       devices_changed_observer_list_;
  69
  70   DISALLOW_COPY_AND_ASSIGN(SystemMonitor);
  71 };
  72
  73 }  // namespace base
  74
  75 #endif  // BASE_SYSTEM_MONITOR_SYSTEM_MONITOR_H_