cc/base/delayed_unique_notifier.cc

// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "cc/base/delayed_unique_notifier.h"

#include <utility>

#include "base/functional/bind.h"
#include "base/functional/callback_helpers.h"
#include "base/location.h"
#include "base/task/sequenced_task_runner.h"

namespace cc {

DelayedUniqueNotifier::DelayedUniqueNotifier(
    base::SequencedTaskRunner* task_runner,
    base::RepeatingClosure closure,
    const base::TimeDelta& delay)
    : task_runner_(task_runner),
      closure_(std::move(closure)),
      delay_(delay),
      notification_pending_(false) {
  DCHECK(!delay_.is_zero());
}

DelayedUniqueNotifier::~DelayedUniqueNotifier() = default;

void DelayedUniqueNotifier::Schedule() {
  DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
  if (notification_pending_) {
    next_notification_time_ = Now() + delay_;
    return;
  }

  next_notification_time_ = Now() + delay_;
  task_runner_->PostDelayedTask(
      FROM_HERE,
      base::BindOnce(&DelayedUniqueNotifier::NotifyIfTime,
                     weak_ptr_factory_.GetWeakPtr()),
      delay_);
  notification_pending_ = true;
}

void DelayedUniqueNotifier::Cancel() {
  DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
  next_notification_time_ = base::TimeTicks();
}

void DelayedUniqueNotifier::Shutdown() {
  DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);

  // This function must destroy any weak ptrs since after being cancelled, this
  // class may be destroyed on another thread during compositor shutdown.
  weak_ptr_factory_.InvalidateWeakPtrs();
  // Deliberately leaves notification_pending_ = true forever so new tasks with
  // weak ptrs can not be created.
  notification_pending_ = true;
}

bool DelayedUniqueNotifier::HasPendingNotification() const {
  DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
  return notification_pending_ && !next_notification_time_.is_null();
}

base::TimeTicks DelayedUniqueNotifier::Now() const {
  return base::TimeTicks::Now();
}

void DelayedUniqueNotifier::NotifyIfTime() {
  DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
  // If next notifiaction time is not valid, then this schedule was canceled.
  if (next_notification_time_.is_null()) {
    notification_pending_ = false;
    return;
  }

  // If the notification was rescheduled or arrived too early for any other
  // reason, then post another task instead of running the callback.
  base::TimeTicks now = Now();
  if (next_notification_time_ > now) {
    task_runner_->PostDelayedTask(
        FROM_HERE,
        base::BindOnce(&DelayedUniqueNotifier::NotifyIfTime,
                       weak_ptr_factory_.GetWeakPtr()),
        next_notification_time_ - now);
    return;
  }

  // Note the order here is important since closure might schedule another
  // run.
  notification_pending_ = false;

  closure_.Run();
}

}  // namespace cc