SystemMonitor refactoring: move power state monitor into a separate class called PowerMonitor

base/power_monitor/power_monitor.h

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Copyright 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 BASE_SYSTEM_MONITOR_SYSTEM_MONITOR_H_
-#define BASE_SYSTEM_MONITOR_SYSTEM_MONITOR_H_
-
-#include <map>
-#include <string>
-#include <vector>
+#ifndef BASE_POWER_MONITOR_POWER_MONITOR_H_
+#define BASE_POWER_MONITOR_POWER_MONITOR_H_
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
-#include "build/build_config.h"
+#include "base/memory/scoped_ptr.h"

[vandebo (ex-Chrome), 2013/03/19 23:36:04]

you want base/memory/ref_counted.h for scoped_refptr

[Hongbo Min, 2013/03/20 13:01:50]

Added. But I am still a bit confused why to use scoped_refptr for observers_, do
you agree to declare the observers_ directly without scoped_refptr? like:

  ObserverListThreadSafe<PowerObserver> observers_;

[vandebo (ex-Chrome), 2013/03/20 20:36:26]

I think it is kept in a scoped_refptr to avoid including the header for it in
the power_monitor.h header.  I think it would be ok with way, so lets just leave
it this way.

+#include "base/observer_list_threadsafe.h"
+#include "base/power_monitor/power_observer.h"
 
+#if defined(OS_WIN)
+#include <windows.h>
 // Windows HiRes timers drain the battery faster so we need to know the battery

[vandebo (ex-Chrome), 2013/03/19 23:36:04]

Nit: add an empty line above comment.

[Hongbo Min, 2013/03/20 13:01:50]

Done.

 // status.  This isn't true for other platforms.
-#if defined(OS_WIN)
 #define ENABLE_BATTERY_MONITORING 1
 #else
 #undef ENABLE_BATTERY_MONITORING
 #endif  // !OS_WIN
 
-#include "base/observer_list_threadsafe.h"
 #if defined(ENABLE_BATTERY_MONITORING)
 #include "base/timer.h"
 #endif  // defined(ENABLE_BATTERY_MONITORING)
 
-#if defined(OS_MACOSX) && !defined(OS_IOS)
-#include <IOKit/pwr_mgt/IOPMLib.h>
-#include <IOKit/IOMessage.h>
-#endif  // OS_MACOSX && !OS_IOS
-
 #if defined(OS_IOS)
 #include <objc/runtime.h>
 #endif  // OS_IOS
 
 namespace base {
 
-// Class for monitoring various system-related subsystems
-// such as power management, network status, etc.
-// TODO(mbelshe):  Add support beyond just power management.
-class BASE_EXPORT SystemMonitor {
+// A class used to monitor the power state change and notify the observers about
+// the change event.
+class BASE_EXPORT PowerMonitor {
  public:
   // Normalized list of power events.
   enum PowerEvent {
     POWER_STATE_EVENT,  // The Power status of the system has changed.
     SUSPEND_EVENT,      // The system is being suspended.
     RESUME_EVENT        // The system is being resumed.
   };
 
-  // Type of devices whose change need to be monitored, such as add/remove.
-  enum DeviceType {
-    DEVTYPE_AUDIO_CAPTURE,  // Audio capture device, e.g., microphone.
-    DEVTYPE_VIDEO_CAPTURE,  // Video capture device, e.g., webcam.
-    DEVTYPE_UNKNOWN,  // Other devices.
-  };
+  PowerMonitor();
+  ~PowerMonitor();
 
-  // Create SystemMonitor. Only one SystemMonitor instance per application
-  // is allowed.
-  SystemMonitor();
-  ~SystemMonitor();
-
-  // Get the application-wide SystemMonitor (if not present, returns NULL).
-  static SystemMonitor* Get();
+  // Get the application-wide PowerMonitor (if not present, returns NULL).
+  static PowerMonitor* Get();
 
 #if defined(OS_MACOSX)
-  // Allocate system resources needed by the SystemMonitor class.
+  // Allocate system resources needed by the PowerMonitor class.
   //
   // This function must be called before instantiating an instance of the class
   // and before the Sandbox is initialized.
 #if !defined(OS_IOS)
   static void AllocateSystemIOPorts();
 #else
   static void AllocateSystemIOPorts() {}
 #endif  // OS_IOS
 #endif  // OS_MACOSX
 
-  //
-  // Power-related APIs
-  //
+  // Add and remove an observer.
+  // Can be called from any thread.
+  // Must not be called from within a notification callback.
+  void AddObserver(PowerObserver* observer);
+  void RemoveObserver(PowerObserver* observer);
 
-  // Is the computer currently on battery power.
-  // Can be called on any thread.
+  // Is the computer currently on battery power. Can be called on any thread.
   bool BatteryPower() const {
     // Using a lock here is not necessary for just a bool.
     return battery_in_use_;
   }
 
-  // Callbacks will be called on the thread which creates the SystemMonitor.
-  // During the callback, Add/RemoveObserver will block until the callbacks
-  // are finished. Observers should implement quick callback functions; if
-  // lengthy operations are needed, the observer should take care to invoke
-  // the operation on an appropriate thread.
-  class BASE_EXPORT PowerObserver {
-   public:
-    // Notification of a change in power status of the computer, such
-    // as from switching between battery and A/C power.
-    virtual void OnPowerStateChange(bool on_battery_power) {}
+ private:
+  friend class PowerMonitorTest;
+  // A friend function that is allowed to access the private ProcessPowerEvent.
+  friend void ProcessPowerEventHelper(PowerEvent);
 
-    // Notification that the system is suspending.
-    virtual void OnSuspend() {}
-
-    // Notification that the system is resuming.
-    virtual void OnResume() {}
-
-   protected:
-    virtual ~PowerObserver() {}
-  };
-
-  class BASE_EXPORT DevicesChangedObserver {
-   public:
-    // Notification that the devices connected to the system have changed.
-    // This is only implemented on Windows currently.
-    virtual void OnDevicesChanged(DeviceType device_type) {}
-
-   protected:
-    virtual ~DevicesChangedObserver() {}
-  };
-
-  // Add a new observer.
-  // Can be called from any thread.
-  // Must not be called from within a notification callback.
-  void AddPowerObserver(PowerObserver* obs);
-  void AddDevicesChangedObserver(DevicesChangedObserver* obs);
-
-  // Remove an existing observer.
-  // Can be called from any thread.
-  // Must not be called from within a notification callback.
-  void RemovePowerObserver(PowerObserver* obs);
-  void RemoveDevicesChangedObserver(DevicesChangedObserver* obs);
-
-  // The ProcessFoo() style methods are a broken pattern and should not
-  // be copied. Any significant addition to this class is blocked on
-  // refactoring to improve the state of affairs. See http://crbug.com/149059
-
-  // Cross-platform handling of a power event.
-  void ProcessPowerMessage(PowerEvent event_id);
-
-  // Cross-platform handling of a device change event.
-  void ProcessDevicesChanged(DeviceType device_type);
-
- private:
 #if defined(OS_WIN)
   // Represents a message-only window for power message handling on Windows.
-  // Only allow SystemMonitor to create it.
+  // Only allow PowerMonitor to create it.
   class PowerMessageWindow {
    public:
     PowerMessageWindow();
     ~PowerMessageWindow();
 
    private:
     void ProcessWmPowerBroadcastMessage(int event_id);
     LRESULT CALLBACK WndProc(HWND hwnd, UINT message,
                              WPARAM wparam, LPARAM lparam);
     static LRESULT CALLBACK WndProcThunk(HWND hwnd,
                                          UINT message,
                                          WPARAM wparam,
                                          LPARAM lparam);
     // Instance of the module containing the window procedure.
     HMODULE instance_;
     // A hidden message-only window.
     HWND message_hwnd_;
   };
-#endif
+#endif  // OS_WIN
 
 #if defined(OS_MACOSX)
   void PlatformInit();
   void PlatformDestroy();
 #endif
 
+  // Cross-platform handling of a power event.
+  void ProcessPowerEvent(PowerEvent event_id);
+
   // Platform-specific method to check whether the system is currently
   // running on battery power.  Returns true if running on batteries,
   // false otherwise.
   bool IsBatteryPower();
 
   // Checks the battery status and notifies observers if the battery
   // status has changed.
   void BatteryCheck();
 
-  // Functions to trigger notifications.
-  void NotifyDevicesChanged(DeviceType device_type);
   void NotifyPowerStateChange();
   void NotifySuspend();
   void NotifyResume();
 
-  scoped_refptr<ObserverListThreadSafe<PowerObserver> > power_observer_list_;
-  scoped_refptr<ObserverListThreadSafe<DevicesChangedObserver> >
-      devices_changed_observer_list_;
-  bool battery_in_use_;
-  bool suspended_;
-
-#if defined(ENABLE_BATTERY_MONITORING)
-  base::OneShotTimer<SystemMonitor> delayed_battery_check_;
-#endif
-
 #if defined(OS_IOS)
   // Holds pointers to system event notification observers.
   std::vector<id> notification_observers_;
 #endif
 
+#if defined(ENABLE_BATTERY_MONITORING)
+  base::OneShotTimer<PowerMonitor> delayed_battery_check_;
+#endif
+
+  scoped_refptr<ObserverListThreadSafe<PowerObserver> > observers_;
+  bool battery_in_use_;
+  bool suspended_;
+
 #if defined(OS_WIN)
   PowerMessageWindow power_message_window_;
 #endif
 
-  DISALLOW_COPY_AND_ASSIGN(SystemMonitor);
+  DISALLOW_COPY_AND_ASSIGN(PowerMonitor);
 };
 
 }  // namespace base
 
-#endif  // BASE_SYSTEM_MONITOR_SYSTEM_MONITOR_H_
+#endif  // BASE_POWER_MONITOR_POWER_MONITOR_H_