chromium/base/timer/wall_clock_timer.h

// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_TIMER_WALL_CLOCK_TIMER_H_
#define BASE_TIMER_WALL_CLOCK_TIMER_H_

#include "base/base_export.h"
#include "base/functional/bind.h"
#include "base/functional/callback.h"
#include "base/location.h"
#include "base/memory/raw_ptr.h"
#include "base/power_monitor/power_observer.h"
#include "base/time/default_clock.h"
#include "base/time/time.h"
#include "base/timer/timer.h"

namespace base {
class Clock;
class TickClock;

// WallClockTimer is based on OneShotTimer and provides a simple timer API
// which is mostly similar to OneShotTimer's API. The main difference is that
// WallClockTimer is using Time (which is system-dependent) to schedule task.
// WallClockTimer calls you back once scheduled time has come.
//
// Comparison with OneShotTimer: WallClockTimer runs |user_task_| after |delay_|
// expires according to usual time, while OneShotTimer runs |user_task_| after
// |delay_| expires according to TimeTicks which may freeze on some platforms
// when power suspends (desktop falls asleep). On platforms where TimeTicks
// don't freeze, the WallClockTimer has the same behavior as OneShotTimer.
//
// The API is not thread safe. All methods must be called from the same
// sequence (not necessarily the construction sequence), except for the
// destructor.
// - The destructor may be called from any sequence when the timer is not
// running and there is no scheduled task active.
class BASE_EXPORT WallClockTimer : public PowerSuspendObserver { … };

}  // namespace base

#endif  // BASE_TIMER_WALL_CLOCK_TIMER_H_