/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "MainThreadIdlePeriod.h"

#include "mozilla/Maybe.h"

#include "mozilla/Preferences.h"

#include "nsRefreshDriver.h"

#include "nsThreadUtils.h"

// The amount of idle time (milliseconds) reserved for a long idle period.

static const double kLongIdlePeriodMS = 50.0;

// The minimum amount of time (milliseconds) required for an idle period to be

// scheduled on the main thread. N.B. layout.idle_period.time_limit adds

// padding at the end of the idle period, which makes the point in time that we

// expect to become busy again be:

//   now + kMinIdlePeriodMS + layout.idle_period.time_limit

static const double kMinIdlePeriodMS = 3.0;

static const uint32_t kMaxTimerThreadBound = 5;       // milliseconds

static const uint32_t kMaxTimerThreadBoundClamp = 15; // milliseconds

namespace mozilla {

NS_IMETHODIMP

MainThreadIdlePeriod::GetIdlePeriodHint(TimeStamp* aIdleDeadline)

{

  MOZ_ASSERT(NS_IsMainThread());

  MOZ_ASSERT(aIdleDeadline);

  TimeStamp now = TimeStamp::Now();

  TimeStamp currentGuess =

    now + TimeDuration::FromMilliseconds(kLongIdlePeriodMS);

  currentGuess = nsRefreshDriver::GetIdleDeadlineHint(currentGuess);

  currentGuess = NS_GetTimerDeadlineHintOnCurrentThread(currentGuess, kMaxTimerThreadBound);

  // If the idle period is too small, then just return a null time

  // to indicate we are busy. Otherwise return the actual deadline.

  TimeDuration minIdlePeriod =

    TimeDuration::FromMilliseconds(kMinIdlePeriodMS);

  bool busySoon = currentGuess.IsNull() ||

                  (now >= (currentGuess - minIdlePeriod)) ||

                  currentGuess < mLastIdleDeadline;

  if (!busySoon) {

    *aIdleDeadline = mLastIdleDeadline = currentGuess;

  }

  return NS_OK;

}

/* static */ float

MainThreadIdlePeriod::GetLongIdlePeriod()

{

  return kLongIdlePeriodMS;

}

} // namespace mozilla