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// 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.
#include "base/base_export.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/observer_list_threadsafe.h"
#include "base/synchronization/lock.h"
namespace base {
class PowerMonitor;
// Communicates power state changes to the power monitor.
class BASE_EXPORT PowerMonitorSource {
virtual ~PowerMonitorSource();
// 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.
// Is the computer currently on battery power. Can be called on any thread.
bool IsOnBatteryPower();
// Called by PowerMonitor just before PowerMonitor destroys both itself and
// this instance). After return from this call it is no longer safe for
// subclasses to call into PowerMonitor (e.g., via PowerMonitor::Get(). Hence,
// subclasses should take any necessary actions here to ensure that after
// return from this invocation they will no longer make any calls on
// PowerMonitor.
virtual void Shutdown() = 0;
friend class PowerMonitorTest;
// Friend function that is allowed to access the protected ProcessPowerEvent.
friend void ProcessPowerEventHelper(PowerEvent);
// ProcessPowerEvent should only be called from a single thread, most likely
// the UI thread or, in child processes, the IO thread.
static 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.
virtual bool IsOnBatteryPowerImpl() = 0;
// Sets the initial state for |on_battery_power_|, which defaults to false
// since not all implementations can provide the value at construction. May
// only be called before a base::PowerMonitor has been created.
void SetInitialOnBatteryPowerState(bool on_battery_power);
bool on_battery_power_ = false;
bool suspended_ = false;
// This lock guards access to on_battery_power_, to ensure that
// IsOnBatteryPower can be called from any thread.
Lock battery_lock_;
} // namespace base