layout/base/nsRefreshDriver.cpp
author Nathan Froyd <froydnj@gmail.com>
Mon, 20 Jun 2016 18:38:10 -0400
changeset 302098 8623823c103f0dfe35a4094f6e6752e65633deb8
parent 301327 6b1139b4cbf5cd0574e548da0b5ae4dec5b7e367
child 304581 769a86b5787dfd7d2bbd10584a54979320c260d9
permissions -rw-r--r--
Bug 1278925 - micro-optimize nsCOMArray appending with already_AddRefed AppendElement; r=erahm In all of the places touched by this patch, the smart pointer we're appending is about to become unused, so simply .forget()'ing its reference into the appropriate nsCOMArray works just fine.

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set shiftwidth=2 tabstop=8 autoindent cindent expandtab: */
/* 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/. */

/*
 * Code to notify things that animate before a refresh, at an appropriate
 * refresh rate.  (Perhaps temporary, until replaced by compositor.)
 *
 * Chrome and each tab have their own RefreshDriver, which in turn
 * hooks into one of a few global timer based on RefreshDriverTimer,
 * defined below.  There are two main global timers -- one for active
 * animations, and one for inactive ones.  These are implemented as
 * subclasses of RefreshDriverTimer; see below for a description of
 * their implementations.  In the future, additional timer types may
 * implement things like blocking on vsync.
 */

#ifdef XP_WIN
#include <windows.h>
// mmsystem isn't part of WIN32_LEAN_AND_MEAN, so we have
// to manually include it
#include <mmsystem.h>
#include "WinUtils.h"
#endif

#include "mozilla/ArrayUtils.h"
#include "mozilla/AutoRestore.h"
#include "mozilla/IntegerRange.h"
#include "nsHostObjectProtocolHandler.h"
#include "nsRefreshDriver.h"
#include "nsITimer.h"
#include "nsLayoutUtils.h"
#include "nsPresContext.h"
#include "nsComponentManagerUtils.h"
#include "mozilla/Logging.h"
#include "nsAutoPtr.h"
#include "nsIDocument.h"
#include "jsapi.h"
#include "nsContentUtils.h"
#include "mozilla/PendingAnimationTracker.h"
#include "mozilla/Preferences.h"
#include "nsViewManager.h"
#include "GeckoProfiler.h"
#include "nsNPAPIPluginInstance.h"
#include "mozilla/dom/Performance.h"
#include "mozilla/dom/WindowBinding.h"
#include "mozilla/RestyleManager.h"
#include "mozilla/RestyleManagerHandle.h"
#include "mozilla/RestyleManagerHandleInlines.h"
#include "Layers.h"
#include "imgIContainer.h"
#include "mozilla/dom/ScriptSettings.h"
#include "nsDocShell.h"
#include "nsISimpleEnumerator.h"
#include "nsJSEnvironment.h"
#include "mozilla/Telemetry.h"
#include "gfxPrefs.h"
#include "BackgroundChild.h"
#include "mozilla/ipc/PBackgroundChild.h"
#include "nsIIPCBackgroundChildCreateCallback.h"
#include "mozilla/layout/VsyncChild.h"
#include "VsyncSource.h"
#include "mozilla/VsyncDispatcher.h"
#include "nsThreadUtils.h"
#include "mozilla/unused.h"
#include "mozilla/TimelineConsumers.h"
#include "nsAnimationManager.h"
#include "nsIDOMEvent.h"

#ifdef MOZ_NUWA_PROCESS
#include "ipc/Nuwa.h"
#endif

using namespace mozilla;
using namespace mozilla::widget;
using namespace mozilla::ipc;
using namespace mozilla::layout;

static mozilla::LazyLogModule sRefreshDriverLog("nsRefreshDriver");
#define LOG(...) MOZ_LOG(sRefreshDriverLog, mozilla::LogLevel::Debug, (__VA_ARGS__))

#define DEFAULT_THROTTLED_FRAME_RATE 1
#define DEFAULT_RECOMPUTE_VISIBILITY_INTERVAL_MS 1000
// after 10 minutes, stop firing off inactive timers
#define DEFAULT_INACTIVE_TIMER_DISABLE_SECONDS 600

namespace {
  // `true` if we are currently in jank-critical mode.
  //
  // In jank-critical mode, any iteration of the event loop that takes
  // more than 16ms to compute will cause an ongoing animation to miss
  // frames.
  //
  // For simplicity, the current implementation assumes that we are in
  // jank-critical mode if and only if at least one vsync driver has
  // at least one observer.
  static uint64_t sActiveVsyncTimers = 0;

  // The latest value of process-wide jank levels.
  //
  // For each i, sJankLevels[i] counts the number of times delivery of
  // vsync to the main thread has been delayed by at least 2^i ms. Use
  // GetJankLevels to grab a copy of this array.
  uint64_t sJankLevels[12];

  // The number outstanding nsRefreshDrivers (that have been created but not
  // disconnected). When this reaches zero we will call
  // nsRefreshDriver::Shutdown.
  static uint32_t sRefreshDriverCount = 0;
}

namespace mozilla {

/*
 * The base class for all global refresh driver timers.  It takes care
 * of managing the list of refresh drivers attached to them and
 * provides interfaces for querying/setting the rate and actually
 * running a timer 'Tick'.  Subclasses must implement StartTimer(),
 * StopTimer(), and ScheduleNextTick() -- the first two just
 * start/stop whatever timer mechanism is in use, and ScheduleNextTick
 * is called at the start of the Tick() implementation to set a time
 * for the next tick.
 */
class RefreshDriverTimer {
public:
  RefreshDriverTimer()
    : mLastFireEpoch(0)
  {
  }

  virtual ~RefreshDriverTimer()
  {
    MOZ_ASSERT(mContentRefreshDrivers.Length() == 0, "Should have removed all content refresh drivers from here by now!");
    MOZ_ASSERT(mRootRefreshDrivers.Length() == 0, "Should have removed all root refresh drivers from here by now!");
  }

  virtual void AddRefreshDriver(nsRefreshDriver* aDriver)
  {
    LOG("[%p] AddRefreshDriver %p", this, aDriver);

    bool startTimer = mContentRefreshDrivers.IsEmpty() && mRootRefreshDrivers.IsEmpty();
    if (IsRootRefreshDriver(aDriver)) {
      NS_ASSERTION(!mRootRefreshDrivers.Contains(aDriver), "Adding a duplicate root refresh driver!");
      mRootRefreshDrivers.AppendElement(aDriver);
    } else {
      NS_ASSERTION(!mContentRefreshDrivers.Contains(aDriver), "Adding a duplicate content refresh driver!");
      mContentRefreshDrivers.AppendElement(aDriver);
    }

    if (startTimer) {
      StartTimer();
    }
  }

  virtual void RemoveRefreshDriver(nsRefreshDriver* aDriver)
  {
    LOG("[%p] RemoveRefreshDriver %p", this, aDriver);

    if (IsRootRefreshDriver(aDriver)) {
      NS_ASSERTION(mRootRefreshDrivers.Contains(aDriver), "RemoveRefreshDriver for a refresh driver that's not in the root refresh list!");
      mRootRefreshDrivers.RemoveElement(aDriver);
    } else {
      nsPresContext* rootContext = aDriver->PresContext()->GetRootPresContext();
      // During PresContext shutdown, we can't accurately detect
      // if a root refresh driver exists or not. Therefore, we have to
      // search and find out which list this driver exists in.
      if (!rootContext) {
        if (mRootRefreshDrivers.Contains(aDriver)) {
          mRootRefreshDrivers.RemoveElement(aDriver);
        } else {
          NS_ASSERTION(mContentRefreshDrivers.Contains(aDriver),
                       "RemoveRefreshDriver without a display root for a driver that is not in the content refresh list");
          mContentRefreshDrivers.RemoveElement(aDriver);
        }
      } else {
        NS_ASSERTION(mContentRefreshDrivers.Contains(aDriver), "RemoveRefreshDriver for a driver that is not in the content refresh list");
        mContentRefreshDrivers.RemoveElement(aDriver);
      }
    }

    bool stopTimer = mContentRefreshDrivers.IsEmpty() && mRootRefreshDrivers.IsEmpty();
    if (stopTimer) {
      StopTimer();
    }
  }

  TimeStamp MostRecentRefresh() const { return mLastFireTime; }
  int64_t MostRecentRefreshEpochTime() const { return mLastFireEpoch; }

  void SwapRefreshDrivers(RefreshDriverTimer* aNewTimer)
  {
    MOZ_ASSERT(NS_IsMainThread());

    for (nsRefreshDriver* driver : mContentRefreshDrivers) {
      aNewTimer->AddRefreshDriver(driver);
      driver->mActiveTimer = aNewTimer;
    }
    mContentRefreshDrivers.Clear();

    for (nsRefreshDriver* driver : mRootRefreshDrivers) {
      aNewTimer->AddRefreshDriver(driver);
      driver->mActiveTimer = aNewTimer;
    }
    mRootRefreshDrivers.Clear();

    aNewTimer->mLastFireEpoch = mLastFireEpoch;
    aNewTimer->mLastFireTime = mLastFireTime;
  }

protected:
  virtual void StartTimer() = 0;
  virtual void StopTimer() = 0;
  virtual void ScheduleNextTick(TimeStamp aNowTime) = 0;

  bool IsRootRefreshDriver(nsRefreshDriver* aDriver)
  {
    nsPresContext* rootContext = aDriver->PresContext()->GetRootPresContext();
    if (!rootContext) {
      return false;
    }

    return aDriver == rootContext->RefreshDriver();
  }

  /*
   * Actually runs a tick, poking all the attached RefreshDrivers.
   * Grabs the "now" time via JS_Now and TimeStamp::Now().
   */
  void Tick()
  {
    int64_t jsnow = JS_Now();
    TimeStamp now = TimeStamp::Now();
    Tick(jsnow, now);
  }

  void TickRefreshDrivers(int64_t aJsNow, TimeStamp aNow, nsTArray<RefPtr<nsRefreshDriver>>& aDrivers)
  {
    if (aDrivers.IsEmpty()) {
      return;
    }

    nsTArray<RefPtr<nsRefreshDriver> > drivers(aDrivers);
    for (nsRefreshDriver* driver : drivers) {
      // don't poke this driver if it's in test mode
      if (driver->IsTestControllingRefreshesEnabled()) {
        continue;
      }

      TickDriver(driver, aJsNow, aNow);
    }
  }

  /*
   * Tick the refresh drivers based on the given timestamp.
   */
  void Tick(int64_t jsnow, TimeStamp now)
  {
    ScheduleNextTick(now);

    mLastFireEpoch = jsnow;
    mLastFireTime = now;

    LOG("[%p] ticking drivers...", this);
    // RD is short for RefreshDriver
    profiler_tracing("Paint", "RD", TRACING_INTERVAL_START);

    TickRefreshDrivers(jsnow, now, mContentRefreshDrivers);
    TickRefreshDrivers(jsnow, now, mRootRefreshDrivers);

    profiler_tracing("Paint", "RD", TRACING_INTERVAL_END);
    LOG("[%p] done.", this);
  }

  static void TickDriver(nsRefreshDriver* driver, int64_t jsnow, TimeStamp now)
  {
    LOG(">> TickDriver: %p (jsnow: %lld)", driver, jsnow);
    driver->Tick(jsnow, now);
  }

  int64_t mLastFireEpoch;
  TimeStamp mLastFireTime;
  TimeStamp mTargetTime;

  nsTArray<RefPtr<nsRefreshDriver> > mContentRefreshDrivers;
  nsTArray<RefPtr<nsRefreshDriver> > mRootRefreshDrivers;

  // useful callback for nsITimer-based derived classes, here
  // bacause of c++ protected shenanigans
  static void TimerTick(nsITimer* aTimer, void* aClosure)
  {
    RefreshDriverTimer *timer = static_cast<RefreshDriverTimer*>(aClosure);
    timer->Tick();
  }
};

/*
 * A RefreshDriverTimer that uses a nsITimer as the underlying timer.  Note that
 * this is a ONE_SHOT timer, not a repeating one!  Subclasses are expected to
 * implement ScheduleNextTick and intelligently calculate the next time to tick,
 * and to reset mTimer.  Using a repeating nsITimer gets us into a lot of pain
 * with its attempt at intelligent slack removal and such, so we don't do it.
 */
class SimpleTimerBasedRefreshDriverTimer :
    public RefreshDriverTimer
{
public:
  /*
   * aRate -- the delay, in milliseconds, requested between timer firings
   */
  explicit SimpleTimerBasedRefreshDriverTimer(double aRate)
  {
    SetRate(aRate);
    mTimer = do_CreateInstance(NS_TIMER_CONTRACTID);
  }

  virtual ~SimpleTimerBasedRefreshDriverTimer()
  {
    StopTimer();
  }

  // will take effect at next timer tick
  virtual void SetRate(double aNewRate)
  {
    mRateMilliseconds = aNewRate;
    mRateDuration = TimeDuration::FromMilliseconds(mRateMilliseconds);
  }

  double GetRate() const
  {
    return mRateMilliseconds;
  }

protected:

  virtual void StartTimer()
  {
    // pretend we just fired, and we schedule the next tick normally
    mLastFireEpoch = JS_Now();
    mLastFireTime = TimeStamp::Now();

    mTargetTime = mLastFireTime + mRateDuration;

    uint32_t delay = static_cast<uint32_t>(mRateMilliseconds);
    mTimer->InitWithFuncCallback(TimerTick, this, delay, nsITimer::TYPE_ONE_SHOT);
  }

  virtual void StopTimer()
  {
    mTimer->Cancel();
  }

  double mRateMilliseconds;
  TimeDuration mRateDuration;
  RefPtr<nsITimer> mTimer;
};

/*
 * A refresh driver that listens to vsync events and ticks the refresh driver
 * on vsync intervals. We throttle the refresh driver if we get too many
 * vsync events and wait to catch up again.
 */
class VsyncRefreshDriverTimer : public RefreshDriverTimer
{
public:
  VsyncRefreshDriverTimer()
    : mVsyncChild(nullptr)
  {
    MOZ_ASSERT(XRE_IsParentProcess());
    MOZ_ASSERT(NS_IsMainThread());
    mVsyncObserver = new RefreshDriverVsyncObserver(this);
    RefPtr<mozilla::gfx::VsyncSource> vsyncSource = gfxPlatform::GetPlatform()->GetHardwareVsync();
    MOZ_ALWAYS_TRUE(mVsyncDispatcher = vsyncSource->GetRefreshTimerVsyncDispatcher());
    mVsyncDispatcher->SetParentRefreshTimer(mVsyncObserver);
  }

  explicit VsyncRefreshDriverTimer(VsyncChild* aVsyncChild)
    : mVsyncChild(aVsyncChild)
  {
    MOZ_ASSERT(!XRE_IsParentProcess());
    MOZ_ASSERT(NS_IsMainThread());
    MOZ_ASSERT(mVsyncChild);
    mVsyncObserver = new RefreshDriverVsyncObserver(this);
    mVsyncChild->SetVsyncObserver(mVsyncObserver);
  }

private:
  // Since VsyncObservers are refCounted, but the RefreshDriverTimer are
  // explicitly shutdown. We create an inner class that has the VsyncObserver
  // and is shutdown when the RefreshDriverTimer is deleted. The alternative is
  // to (a) make all RefreshDriverTimer RefCounted or (b) use different
  // VsyncObserver types.
  class RefreshDriverVsyncObserver final : public VsyncObserver
  {
  public:
    explicit RefreshDriverVsyncObserver(VsyncRefreshDriverTimer* aVsyncRefreshDriverTimer)
      : mVsyncRefreshDriverTimer(aVsyncRefreshDriverTimer)
      , mRefreshTickLock("RefreshTickLock")
      , mRecentVsync(TimeStamp::Now())
      , mLastChildTick(TimeStamp::Now())
      , mVsyncRate(TimeDuration::Forever())
      , mProcessedVsync(true)
    {
      MOZ_ASSERT(NS_IsMainThread());
    }

    virtual bool NotifyVsync(TimeStamp aVsyncTimestamp) override
    {
      if (!NS_IsMainThread()) {
        MOZ_ASSERT(XRE_IsParentProcess());
        // Compress vsync notifications such that only 1 may run at a time
        // This is so that we don't flood the refresh driver with vsync messages
        // if the main thread is blocked for long periods of time
        { // scope lock
          MonitorAutoLock lock(mRefreshTickLock);
          mRecentVsync = aVsyncTimestamp;
          if (!mProcessedVsync) {
            return true;
          }
          mProcessedVsync = false;
        }

        nsCOMPtr<nsIRunnable> vsyncEvent =
             NewRunnableMethod<TimeStamp>(this,
                                          &RefreshDriverVsyncObserver::TickRefreshDriver,
                                          aVsyncTimestamp);
        NS_DispatchToMainThread(vsyncEvent);
      } else {
        TickRefreshDriver(aVsyncTimestamp);
      }

      return true;
    }

    void Shutdown()
    {
      MOZ_ASSERT(NS_IsMainThread());
      mVsyncRefreshDriverTimer = nullptr;
    }

    void OnTimerStart()
    {
      if (!XRE_IsParentProcess()) {
        mLastChildTick = TimeStamp::Now();
      }
    }

  private:
    virtual ~RefreshDriverVsyncObserver() {}

    void RecordTelemetryProbes(TimeStamp aVsyncTimestamp)
    {
      MOZ_ASSERT(NS_IsMainThread());
    #ifndef ANDROID  /* bug 1142079 */
      if (XRE_IsParentProcess()) {
        TimeDuration vsyncLatency = TimeStamp::Now() - aVsyncTimestamp;
        uint32_t sample = (uint32_t)vsyncLatency.ToMilliseconds();
        Telemetry::Accumulate(Telemetry::FX_REFRESH_DRIVER_CHROME_FRAME_DELAY_MS,
                              sample);
        Telemetry::Accumulate(Telemetry::FX_REFRESH_DRIVER_SYNC_SCROLL_FRAME_DELAY_MS,
                              sample);
        RecordJank(sample);
      } else if (mVsyncRate != TimeDuration::Forever()) {
        TimeDuration contentDelay = (TimeStamp::Now() - mLastChildTick) - mVsyncRate;
        if (contentDelay.ToMilliseconds() < 0 ){
          // Vsyncs are noisy and some can come at a rate quicker than
          // the reported hardware rate. In those cases, consider that we have 0 delay.
          contentDelay = TimeDuration::FromMilliseconds(0);
        }
        uint32_t sample = (uint32_t)contentDelay.ToMilliseconds();
        Telemetry::Accumulate(Telemetry::FX_REFRESH_DRIVER_CONTENT_FRAME_DELAY_MS,
                              sample);
        Telemetry::Accumulate(Telemetry::FX_REFRESH_DRIVER_SYNC_SCROLL_FRAME_DELAY_MS,
                              sample);
        RecordJank(sample);
      } else {
        // Request the vsync rate from the parent process. Might be a few vsyncs
        // until the parent responds.
        mVsyncRate = mVsyncRefreshDriverTimer->mVsyncChild->GetVsyncRate();
      }
    #endif
    }

    void RecordJank(uint32_t aJankMS)
    {
      uint32_t duration = 1 /* ms */;
      for (size_t i = 0;
           i < mozilla::ArrayLength(sJankLevels) && duration < aJankMS;
           ++i, duration *= 2) {
        sJankLevels[i]++;
      }
    }

    void TickRefreshDriver(TimeStamp aVsyncTimestamp)
    {
      MOZ_ASSERT(NS_IsMainThread());

      RecordTelemetryProbes(aVsyncTimestamp);
      if (XRE_IsParentProcess()) {
        MonitorAutoLock lock(mRefreshTickLock);
        aVsyncTimestamp = mRecentVsync;
        mProcessedVsync = true;
      } else {
        mLastChildTick = TimeStamp::Now();
      }
      MOZ_ASSERT(aVsyncTimestamp <= TimeStamp::Now());

      // We might have a problem that we call ~VsyncRefreshDriverTimer() before
      // the scheduled TickRefreshDriver() runs. Check mVsyncRefreshDriverTimer
      // before use.
      if (mVsyncRefreshDriverTimer) {
        mVsyncRefreshDriverTimer->RunRefreshDrivers(aVsyncTimestamp);
      }
    }

    // VsyncRefreshDriverTimer holds this RefreshDriverVsyncObserver and it will
    // be always available before Shutdown(). We can just use the raw pointer
    // here.
    VsyncRefreshDriverTimer* mVsyncRefreshDriverTimer;
    Monitor mRefreshTickLock;
    TimeStamp mRecentVsync;
    TimeStamp mLastChildTick;
    TimeDuration mVsyncRate;
    bool mProcessedVsync;
  }; // RefreshDriverVsyncObserver

  virtual ~VsyncRefreshDriverTimer()
  {
    if (XRE_IsParentProcess()) {
      mVsyncDispatcher->SetParentRefreshTimer(nullptr);
      mVsyncDispatcher = nullptr;
    } else {
      // Since the PVsyncChild actors live through the life of the process, just
      // send the unobserveVsync message to disable vsync event. We don't need
      // to handle the cleanup stuff of this actor. PVsyncChild::ActorDestroy()
      // will be called and clean up this actor.
      Unused << mVsyncChild->SendUnobserve();
      mVsyncChild->SetVsyncObserver(nullptr);
      mVsyncChild = nullptr;
    }

    // Detach current vsync timer from this VsyncObserver. The observer will no
    // longer tick this timer.
    mVsyncObserver->Shutdown();
    mVsyncObserver = nullptr;
  }

  virtual void StartTimer() override
  {
    // Protect updates to `sActiveVsyncTimers`.
    MOZ_ASSERT(NS_IsMainThread());

    mLastFireEpoch = JS_Now();
    mLastFireTime = TimeStamp::Now();

    if (XRE_IsParentProcess()) {
      mVsyncDispatcher->SetParentRefreshTimer(mVsyncObserver);
    } else {
      Unused << mVsyncChild->SendObserve();
      mVsyncObserver->OnTimerStart();
    }

    ++sActiveVsyncTimers;
  }

  virtual void StopTimer() override
  {
    // Protect updates to `sActiveVsyncTimers`.
    MOZ_ASSERT(NS_IsMainThread());

    if (XRE_IsParentProcess()) {
      mVsyncDispatcher->SetParentRefreshTimer(nullptr);
    } else {
      Unused << mVsyncChild->SendUnobserve();
    }

    MOZ_ASSERT(sActiveVsyncTimers > 0);
    --sActiveVsyncTimers;
  }

  virtual void ScheduleNextTick(TimeStamp aNowTime) override
  {
    // Do nothing since we just wait for the next vsync from
    // RefreshDriverVsyncObserver.
  }

  void RunRefreshDrivers(TimeStamp aTimeStamp)
  {
    int64_t jsnow = JS_Now();
    TimeDuration diff = TimeStamp::Now() - aTimeStamp;
    int64_t vsyncJsNow = jsnow - diff.ToMicroseconds();
    Tick(vsyncJsNow, aTimeStamp);
  }

  RefPtr<RefreshDriverVsyncObserver> mVsyncObserver;
  // Used for parent process.
  RefPtr<RefreshTimerVsyncDispatcher> mVsyncDispatcher;
  // Used for child process.
  // The mVsyncChild will be always available before VsncChild::ActorDestroy().
  // After ActorDestroy(), StartTimer() and StopTimer() calls will be non-op.
  RefPtr<VsyncChild> mVsyncChild;
}; // VsyncRefreshDriverTimer

/**
 * Since the content process takes some time to setup
 * the vsync IPC connection, this timer is used
 * during the intial startup process.
 * During initial startup, the refresh drivers
 * are ticked off this timer, and are swapped out once content
 * vsync IPC connection is established.
 */
class StartupRefreshDriverTimer :
    public SimpleTimerBasedRefreshDriverTimer
{
public:
  explicit StartupRefreshDriverTimer(double aRate)
    : SimpleTimerBasedRefreshDriverTimer(aRate)
  {
  }

protected:
  virtual void ScheduleNextTick(TimeStamp aNowTime)
  {
    // Since this is only used for startup, it isn't super critical
    // that we tick at consistent intervals.
    TimeStamp newTarget = aNowTime + mRateDuration;
    uint32_t delay = static_cast<uint32_t>((newTarget - aNowTime).ToMilliseconds());
    mTimer->InitWithFuncCallback(TimerTick, this, delay, nsITimer::TYPE_ONE_SHOT);
    mTargetTime = newTarget;
  }
};

/*
 * A RefreshDriverTimer for inactive documents.  When a new refresh driver is
 * added, the rate is reset to the base (normally 1s/1fps).  Every time
 * it ticks, a single refresh driver is poked.  Once they have all been poked,
 * the duration between ticks doubles, up to mDisableAfterMilliseconds.  At that point,
 * the timer is quiet and doesn't tick (until something is added to it again).
 *
 * When a timer is removed, there is a possibility of another timer
 * being skipped for one cycle.  We could avoid this by adjusting
 * mNextDriverIndex in RemoveRefreshDriver, but there's little need to
 * add that complexity.  All we want is for inactive drivers to tick
 * at some point, but we don't care too much about how often.
 */
class InactiveRefreshDriverTimer final :
    public SimpleTimerBasedRefreshDriverTimer
{
public:
  explicit InactiveRefreshDriverTimer(double aRate)
    : SimpleTimerBasedRefreshDriverTimer(aRate),
      mNextTickDuration(aRate),
      mDisableAfterMilliseconds(-1.0),
      mNextDriverIndex(0)
  {
  }

  InactiveRefreshDriverTimer(double aRate, double aDisableAfterMilliseconds)
    : SimpleTimerBasedRefreshDriverTimer(aRate),
      mNextTickDuration(aRate),
      mDisableAfterMilliseconds(aDisableAfterMilliseconds),
      mNextDriverIndex(0)
  {
  }

  virtual void AddRefreshDriver(nsRefreshDriver* aDriver)
  {
    RefreshDriverTimer::AddRefreshDriver(aDriver);

    LOG("[%p] inactive timer got new refresh driver %p, resetting rate",
        this, aDriver);

    // reset the timer, and start with the newly added one next time.
    mNextTickDuration = mRateMilliseconds;

    // we don't really have to start with the newly added one, but we may as well
    // not tick the old ones at the fastest rate any more than we need to.
    mNextDriverIndex = GetRefreshDriverCount() - 1;

    StopTimer();
    StartTimer();
  }

protected:
  uint32_t GetRefreshDriverCount()
  {
    return mContentRefreshDrivers.Length() + mRootRefreshDrivers.Length();
  }

  virtual void StartTimer()
  {
    mLastFireEpoch = JS_Now();
    mLastFireTime = TimeStamp::Now();

    mTargetTime = mLastFireTime + mRateDuration;

    uint32_t delay = static_cast<uint32_t>(mRateMilliseconds);
    mTimer->InitWithFuncCallback(TimerTickOne, this, delay, nsITimer::TYPE_ONE_SHOT);
  }

  virtual void StopTimer()
  {
    mTimer->Cancel();
  }

  virtual void ScheduleNextTick(TimeStamp aNowTime)
  {
    if (mDisableAfterMilliseconds > 0.0 &&
        mNextTickDuration > mDisableAfterMilliseconds)
    {
      // We hit the time after which we should disable
      // inactive window refreshes; don't schedule anything
      // until we get kicked by an AddRefreshDriver call.
      return;
    }

    // double the next tick time if we've already gone through all of them once
    if (mNextDriverIndex >= GetRefreshDriverCount()) {
      mNextTickDuration *= 2.0;
      mNextDriverIndex = 0;
    }

    // this doesn't need to be precise; do a simple schedule
    uint32_t delay = static_cast<uint32_t>(mNextTickDuration);
    mTimer->InitWithFuncCallback(TimerTickOne, this, delay, nsITimer::TYPE_ONE_SHOT);

    LOG("[%p] inactive timer next tick in %f ms [index %d/%d]", this, mNextTickDuration,
        mNextDriverIndex, GetRefreshDriverCount());
  }

  /* Runs just one driver's tick. */
  void TickOne()
  {
    int64_t jsnow = JS_Now();
    TimeStamp now = TimeStamp::Now();

    ScheduleNextTick(now);

    mLastFireEpoch = jsnow;
    mLastFireTime = now;

    nsTArray<RefPtr<nsRefreshDriver> > drivers(mContentRefreshDrivers);
    drivers.AppendElements(mRootRefreshDrivers);

    if (mNextDriverIndex < drivers.Length() &&
        !drivers[mNextDriverIndex]->IsTestControllingRefreshesEnabled())
    {
      TickDriver(drivers[mNextDriverIndex], jsnow, now);
    }

    mNextDriverIndex++;
  }

  static void TimerTickOne(nsITimer* aTimer, void* aClosure)
  {
    InactiveRefreshDriverTimer *timer = static_cast<InactiveRefreshDriverTimer*>(aClosure);
    timer->TickOne();
  }

  double mNextTickDuration;
  double mDisableAfterMilliseconds;
  uint32_t mNextDriverIndex;
};

// The PBackground protocol connection callback. It will be called when
// PBackground is ready. Then we create the PVsync sub-protocol for our
// vsync-base RefreshTimer.
class VsyncChildCreateCallback final : public nsIIPCBackgroundChildCreateCallback
{
  NS_DECL_ISUPPORTS

public:
  VsyncChildCreateCallback()
  {
    MOZ_ASSERT(NS_IsMainThread());
  }

  static void CreateVsyncActor(PBackgroundChild* aPBackgroundChild)
  {
    MOZ_ASSERT(NS_IsMainThread());
    MOZ_ASSERT(aPBackgroundChild);

    layout::PVsyncChild* actor = aPBackgroundChild->SendPVsyncConstructor();
    layout::VsyncChild* child = static_cast<layout::VsyncChild*>(actor);
    nsRefreshDriver::PVsyncActorCreated(child);
  }

private:
  virtual ~VsyncChildCreateCallback() {}

  virtual void ActorCreated(PBackgroundChild* aPBackgroundChild) override
  {
    MOZ_ASSERT(NS_IsMainThread());
    MOZ_ASSERT(aPBackgroundChild);
    CreateVsyncActor(aPBackgroundChild);
  }

  virtual void ActorFailed() override
  {
    MOZ_ASSERT(NS_IsMainThread());
    MOZ_CRASH("Failed To Create VsyncChild Actor");
  }
}; // VsyncChildCreateCallback
NS_IMPL_ISUPPORTS(VsyncChildCreateCallback, nsIIPCBackgroundChildCreateCallback)

} // namespace mozilla

static RefreshDriverTimer* sRegularRateTimer;
static InactiveRefreshDriverTimer* sThrottledRateTimer;

#ifdef XP_WIN
static int32_t sHighPrecisionTimerRequests = 0;
// a bare pointer to avoid introducing a static constructor
static nsITimer *sDisableHighPrecisionTimersTimer = nullptr;
#endif

static void
CreateContentVsyncRefreshTimer(void*)
{
  MOZ_ASSERT(NS_IsMainThread());
  MOZ_ASSERT(!XRE_IsParentProcess());

  // Create the PVsync actor child for vsync-base refresh timer.
  // PBackgroundChild is created asynchronously. If PBackgroundChild is still
  // unavailable, setup VsyncChildCreateCallback callback to handle the async
  // connect. We will still use software timer before PVsync ready, and change
  // to use hw timer when the connection is done. Please check
  // VsyncChildCreateCallback::CreateVsyncActor() and
  // nsRefreshDriver::PVsyncActorCreated().
  PBackgroundChild* backgroundChild = BackgroundChild::GetForCurrentThread();
  if (backgroundChild) {
    // If we already have PBackgroundChild, create the
    // child VsyncRefreshDriverTimer here.
    VsyncChildCreateCallback::CreateVsyncActor(backgroundChild);
    return;
  }
  // Setup VsyncChildCreateCallback callback
  RefPtr<nsIIPCBackgroundChildCreateCallback> callback = new VsyncChildCreateCallback();
  if (NS_WARN_IF(!BackgroundChild::GetOrCreateForCurrentThread(callback))) {
    MOZ_CRASH("PVsync actor create failed!");
  }
}

static void
CreateVsyncRefreshTimer()
{
  MOZ_ASSERT(NS_IsMainThread());

  PodArrayZero(sJankLevels);
  // Sometimes, gfxPrefs is not initialized here. Make sure the gfxPrefs is
  // ready.
  gfxPrefs::GetSingleton();

  if (gfxPlatform::IsInLayoutAsapMode()) {
    return;
  }

  if (XRE_IsParentProcess()) {
    // Make sure all vsync systems are ready.
    gfxPlatform::GetPlatform();
    // In parent process, we don't need to use ipc. We can create the
    // VsyncRefreshDriverTimer directly.
    sRegularRateTimer = new VsyncRefreshDriverTimer();
    return;
  }

#ifdef MOZ_NUWA_PROCESS
  // NUWA process will just use software timer. Use NuwaAddFinalConstructor()
  // to register a callback to create the vsync-base refresh timer after a
  // process is created.
  if (IsNuwaProcess()) {
    NuwaAddFinalConstructor(&CreateContentVsyncRefreshTimer, nullptr);
    return;
  }
#endif
  // If this process is not created by NUWA, just create the vsync timer here.
  CreateContentVsyncRefreshTimer(nullptr);
}

static uint32_t
GetFirstFrameDelay(imgIRequest* req)
{
  nsCOMPtr<imgIContainer> container;
  if (NS_FAILED(req->GetImage(getter_AddRefs(container))) || !container) {
    return 0;
  }

  // If this image isn't animated, there isn't a first frame delay.
  int32_t delay = container->GetFirstFrameDelay();
  if (delay < 0)
    return 0;

  return static_cast<uint32_t>(delay);
}

/* static */ void
nsRefreshDriver::Shutdown()
{
  // clean up our timers
  delete sRegularRateTimer;
  delete sThrottledRateTimer;

  sRegularRateTimer = nullptr;
  sThrottledRateTimer = nullptr;

#ifdef XP_WIN
  if (sDisableHighPrecisionTimersTimer) {
    sDisableHighPrecisionTimersTimer->Cancel();
    NS_RELEASE(sDisableHighPrecisionTimersTimer);
    timeEndPeriod(1);
  } else if (sHighPrecisionTimerRequests) {
    timeEndPeriod(1);
  }
#endif
}

/* static */ int32_t
nsRefreshDriver::DefaultInterval()
{
  return NSToIntRound(1000.0 / gfxPlatform::GetDefaultFrameRate());
}

// Compute the interval to use for the refresh driver timer, in milliseconds.
// outIsDefault indicates that rate was not explicitly set by the user
// so we might choose other, more appropriate rates (e.g. vsync, etc)
// layout.frame_rate=0 indicates "ASAP mode".
// In ASAP mode rendering is iterated as fast as possible (typically for stress testing).
// A target rate of 10k is used internally instead of special-handling 0.
// Backends which block on swap/present/etc should try to not block
// when layout.frame_rate=0 - to comply with "ASAP" as much as possible.
double
nsRefreshDriver::GetRegularTimerInterval(bool *outIsDefault) const
{
  int32_t rate = Preferences::GetInt("layout.frame_rate", -1);
  if (rate < 0) {
    rate = gfxPlatform::GetDefaultFrameRate();
    if (outIsDefault) {
      *outIsDefault = true;
    }
  } else {
    if (outIsDefault) {
      *outIsDefault = false;
    }
  }

  if (rate == 0) {
    rate = 10000;
  }

  return 1000.0 / rate;
}

/* static */ double
nsRefreshDriver::GetThrottledTimerInterval()
{
  int32_t rate = Preferences::GetInt("layout.throttled_frame_rate", -1);
  if (rate <= 0) {
    rate = DEFAULT_THROTTLED_FRAME_RATE;
  }
  return 1000.0 / rate;
}

/* static */ mozilla::TimeDuration
nsRefreshDriver::GetMinRecomputeVisibilityInterval()
{
  int32_t interval =
    Preferences::GetInt("layout.visibility.min-recompute-interval-ms", -1);
  if (interval <= 0) {
    interval = DEFAULT_RECOMPUTE_VISIBILITY_INTERVAL_MS;
  }
  return TimeDuration::FromMilliseconds(interval);
}

double
nsRefreshDriver::GetRefreshTimerInterval() const
{
  return mThrottled ? GetThrottledTimerInterval() : GetRegularTimerInterval();
}

RefreshDriverTimer*
nsRefreshDriver::ChooseTimer() const
{
  if (mThrottled) {
    if (!sThrottledRateTimer)
      sThrottledRateTimer = new InactiveRefreshDriverTimer(GetThrottledTimerInterval(),
                                                           DEFAULT_INACTIVE_TIMER_DISABLE_SECONDS * 1000.0);
    return sThrottledRateTimer;
  }

  if (!sRegularRateTimer) {
    bool isDefault = true;
    double rate = GetRegularTimerInterval(&isDefault);

    // Try to use vsync-base refresh timer first for sRegularRateTimer.
    CreateVsyncRefreshTimer();

    if (!sRegularRateTimer) {
      sRegularRateTimer = new StartupRefreshDriverTimer(rate);
    }
  }
  return sRegularRateTimer;
}

nsRefreshDriver::nsRefreshDriver(nsPresContext* aPresContext)
  : mActiveTimer(nullptr),
    mReflowCause(nullptr),
    mStyleCause(nullptr),
    mPresContext(aPresContext),
    mRootRefresh(nullptr),
    mPendingTransaction(0),
    mCompletedTransaction(0),
    mFreezeCount(0),
    mThrottledFrameRequestInterval(TimeDuration::FromMilliseconds(
                                     GetThrottledTimerInterval())),
    mMinRecomputeVisibilityInterval(GetMinRecomputeVisibilityInterval()),
    mThrottled(false),
    mNeedToRecomputeVisibility(false),
    mTestControllingRefreshes(false),
    mViewManagerFlushIsPending(false),
    mRequestedHighPrecision(false),
    mInRefresh(false),
    mWaitingForTransaction(false),
    mSkippedPaints(false),
    mResizeSuppressed(false)
{
  MOZ_ASSERT(NS_IsMainThread());
  MOZ_ASSERT(mPresContext,
             "Need a pres context to tell us to call Disconnect() later "
             "and decrement sRefreshDriverCount.");

  mMostRecentRefreshEpochTime = JS_Now();
  mMostRecentRefresh = TimeStamp::Now();
  mMostRecentTick = mMostRecentRefresh;
  mNextThrottledFrameRequestTick = mMostRecentTick;
  mNextRecomputeVisibilityTick = mMostRecentTick;

  ++sRefreshDriverCount;
}

nsRefreshDriver::~nsRefreshDriver()
{
  MOZ_ASSERT(NS_IsMainThread());
  MOZ_ASSERT(ObserverCount() == 0,
             "observers should have unregistered");
  MOZ_ASSERT(!mActiveTimer, "timer should be gone");
  MOZ_ASSERT(!mPresContext,
             "Should have called Disconnect() and decremented "
             "sRefreshDriverCount!");

  if (mRootRefresh) {
    mRootRefresh->RemoveRefreshObserver(this, Flush_Style);
    mRootRefresh = nullptr;
  }
  for (nsIPresShell* shell : mPresShellsToInvalidateIfHidden) {
    shell->InvalidatePresShellIfHidden();
  }
  mPresShellsToInvalidateIfHidden.Clear();

  profiler_free_backtrace(mStyleCause);
  profiler_free_backtrace(mReflowCause);
}

// Method for testing.  See nsIDOMWindowUtils.advanceTimeAndRefresh
// for description.
void
nsRefreshDriver::AdvanceTimeAndRefresh(int64_t aMilliseconds)
{
  // ensure that we're removed from our driver
  StopTimer();

  if (!mTestControllingRefreshes) {
    mMostRecentRefreshEpochTime = JS_Now();
    mMostRecentRefresh = TimeStamp::Now();

    mTestControllingRefreshes = true;
    if (mWaitingForTransaction) {
      // Disable any refresh driver throttling when entering test mode
      mWaitingForTransaction = false;
      mSkippedPaints = false;
    }
  }

  mMostRecentRefreshEpochTime += aMilliseconds * 1000;
  mMostRecentRefresh += TimeDuration::FromMilliseconds((double) aMilliseconds);

  mozilla::dom::AutoNoJSAPI nojsapi;
  DoTick();
}

void
nsRefreshDriver::RestoreNormalRefresh()
{
  mTestControllingRefreshes = false;
  EnsureTimerStarted(eAllowTimeToGoBackwards);
  mCompletedTransaction = mPendingTransaction;
}

TimeStamp
nsRefreshDriver::MostRecentRefresh() const
{
  const_cast<nsRefreshDriver*>(this)->EnsureTimerStarted();

  return mMostRecentRefresh;
}

int64_t
nsRefreshDriver::MostRecentRefreshEpochTime() const
{
  const_cast<nsRefreshDriver*>(this)->EnsureTimerStarted();

  return mMostRecentRefreshEpochTime;
}

bool
nsRefreshDriver::AddRefreshObserver(nsARefreshObserver* aObserver,
                                    mozFlushType aFlushType)
{
  ObserverArray& array = ArrayFor(aFlushType);
  bool success = array.AppendElement(aObserver) != nullptr;
  EnsureTimerStarted();
  return success;
}

bool
nsRefreshDriver::RemoveRefreshObserver(nsARefreshObserver* aObserver,
                                       mozFlushType aFlushType)
{
  ObserverArray& array = ArrayFor(aFlushType);
  return array.RemoveElement(aObserver);
}

void
nsRefreshDriver::AddPostRefreshObserver(nsAPostRefreshObserver* aObserver)
{
  mPostRefreshObservers.AppendElement(aObserver);
}

void
nsRefreshDriver::RemovePostRefreshObserver(nsAPostRefreshObserver* aObserver)
{
  mPostRefreshObservers.RemoveElement(aObserver);
}

bool
nsRefreshDriver::AddImageRequest(imgIRequest* aRequest)
{
  uint32_t delay = GetFirstFrameDelay(aRequest);
  if (delay == 0) {
    if (!mRequests.PutEntry(aRequest)) {
      return false;
    }
  } else {
    ImageStartData* start = mStartTable.Get(delay);
    if (!start) {
      start = new ImageStartData();
      mStartTable.Put(delay, start);
    }
    start->mEntries.PutEntry(aRequest);
  }

  EnsureTimerStarted();

  return true;
}

void
nsRefreshDriver::RemoveImageRequest(imgIRequest* aRequest)
{
  // Try to remove from both places, just in case, because we can't tell
  // whether RemoveEntry() succeeds.
  mRequests.RemoveEntry(aRequest);
  uint32_t delay = GetFirstFrameDelay(aRequest);
  if (delay != 0) {
    ImageStartData* start = mStartTable.Get(delay);
    if (start) {
      start->mEntries.RemoveEntry(aRequest);
    }
  }
}

void
nsRefreshDriver::EnsureTimerStarted(EnsureTimerStartedFlags aFlags)
{
  if (mTestControllingRefreshes)
    return;

  // will it already fire, and no other changes needed?
  if (mActiveTimer && !(aFlags & eForceAdjustTimer))
    return;

  if (IsFrozen() || !mPresContext) {
    // If we don't want to start it now, or we've been disconnected.
    StopTimer();
    return;
  }

  if (mPresContext->Document()->IsBeingUsedAsImage()) {
    // Image documents receive ticks from clients' refresh drivers.
    // XXXdholbert Exclude SVG-in-opentype fonts from this optimization, until
    // they receive refresh-driver ticks from their client docs (bug 1107252).
    nsIURI* uri = mPresContext->Document()->GetDocumentURI();
    if (!uri || !IsFontTableURI(uri)) {
      MOZ_ASSERT(!mActiveTimer,
                 "image doc refresh driver should never have its own timer");
      return;
    }
  }

  // We got here because we're either adjusting the time *or* we're
  // starting it for the first time.  Add to the right timer,
  // prehaps removing it from a previously-set one.
  RefreshDriverTimer *newTimer = ChooseTimer();
  if (newTimer != mActiveTimer) {
    if (mActiveTimer)
      mActiveTimer->RemoveRefreshDriver(this);
    mActiveTimer = newTimer;
    mActiveTimer->AddRefreshDriver(this);
  }

  // When switching from an inactive timer to an active timer, the root
  // refresh driver is skipped due to being set to the content refresh
  // driver's timestamp. In case of EnsureTimerStarted is called from
  // ScheduleViewManagerFlush, we should avoid this behavior to flush
  // a paint in the same tick on the root refresh driver.
  if (aFlags & eNeverAdjustTimer) {
    return;
  }

  // Since the different timers are sampled at different rates, when switching
  // timers, the most recent refresh of the new timer may be *before* the
  // most recent refresh of the old timer. However, the refresh driver time
  // should not go backwards so we clamp the most recent refresh time.
  //
  // The one exception to this is when we are restoring the refresh driver
  // from test control in which case the time is expected to go backwards
  // (see bug 1043078).
  mMostRecentRefresh =
    aFlags & eAllowTimeToGoBackwards
    ? mActiveTimer->MostRecentRefresh()
    : std::max(mActiveTimer->MostRecentRefresh(), mMostRecentRefresh);
  mMostRecentRefreshEpochTime =
    aFlags & eAllowTimeToGoBackwards
    ? mActiveTimer->MostRecentRefreshEpochTime()
    : std::max(mActiveTimer->MostRecentRefreshEpochTime(),
               mMostRecentRefreshEpochTime);
}

void
nsRefreshDriver::StopTimer()
{
  if (!mActiveTimer)
    return;

  mActiveTimer->RemoveRefreshDriver(this);
  mActiveTimer = nullptr;

  if (mRequestedHighPrecision) {
    SetHighPrecisionTimersEnabled(false);
  }
}

#ifdef XP_WIN
static void
DisableHighPrecisionTimersCallback(nsITimer *aTimer, void *aClosure)
{
  timeEndPeriod(1);
  NS_RELEASE(sDisableHighPrecisionTimersTimer);
}
#endif

void
nsRefreshDriver::ConfigureHighPrecision()
{
  bool haveUnthrottledFrameRequestCallbacks =
    mFrameRequestCallbackDocs.Length() > 0;

  // if the only change that's needed is that we need high precision,
  // then just set that
  if (!mThrottled && !mRequestedHighPrecision &&
      haveUnthrottledFrameRequestCallbacks) {
    SetHighPrecisionTimersEnabled(true);
  } else if (mRequestedHighPrecision && !haveUnthrottledFrameRequestCallbacks) {
    SetHighPrecisionTimersEnabled(false);
  }
}

void
nsRefreshDriver::SetHighPrecisionTimersEnabled(bool aEnable)
{
  LOG("[%p] SetHighPrecisionTimersEnabled (%s)", this, aEnable ? "true" : "false");

  if (aEnable) {
    NS_ASSERTION(!mRequestedHighPrecision, "SetHighPrecisionTimersEnabled(true) called when already requested!");
#ifdef XP_WIN
    if (++sHighPrecisionTimerRequests == 1) {
      // If we had a timer scheduled to disable it, that means that it's already
      // enabled; just cancel the timer.  Otherwise, really enable it.
      if (sDisableHighPrecisionTimersTimer) {
        sDisableHighPrecisionTimersTimer->Cancel();
        NS_RELEASE(sDisableHighPrecisionTimersTimer);
      } else {
        timeBeginPeriod(1);
      }
    }
#endif
    mRequestedHighPrecision = true;
  } else {
    NS_ASSERTION(mRequestedHighPrecision, "SetHighPrecisionTimersEnabled(false) called when not requested!");
#ifdef XP_WIN
    if (--sHighPrecisionTimerRequests == 0) {
      // Don't jerk us around between high precision and low precision
      // timers; instead, only allow leaving high precision timers
      // after 90 seconds.  This is arbitrary, but hopefully good
      // enough.
      NS_ASSERTION(!sDisableHighPrecisionTimersTimer, "We shouldn't have an outstanding disable-high-precision timer !");

      nsCOMPtr<nsITimer> timer = do_CreateInstance(NS_TIMER_CONTRACTID);
      if (timer) {
        timer.forget(&sDisableHighPrecisionTimersTimer);
        sDisableHighPrecisionTimersTimer->InitWithFuncCallback(DisableHighPrecisionTimersCallback,
                                                               nullptr,
                                                               90 * 1000,
                                                               nsITimer::TYPE_ONE_SHOT);
      } else {
        // might happen if we're shutting down XPCOM; just drop the time period down
        // immediately
        timeEndPeriod(1);
      }
    }
#endif
    mRequestedHighPrecision = false;
  }
}

uint32_t
nsRefreshDriver::ObserverCount() const
{
  uint32_t sum = 0;
  for (uint32_t i = 0; i < ArrayLength(mObservers); ++i) {
    sum += mObservers[i].Length();
  }

  // Even while throttled, we need to process layout and style changes.  Style
  // changes can trigger transitions which fire events when they complete, and
  // layout changes can affect media queries on child documents, triggering
  // style changes, etc.
  sum += mStyleFlushObservers.Length();
  sum += mLayoutFlushObservers.Length();
  sum += mPendingEvents.Length();
  sum += mFrameRequestCallbackDocs.Length();
  sum += mThrottledFrameRequestCallbackDocs.Length();
  sum += mViewManagerFlushIsPending;
  return sum;
}

uint32_t
nsRefreshDriver::ImageRequestCount() const
{
  uint32_t count = 0;
  for (auto iter = mStartTable.ConstIter(); !iter.Done(); iter.Next()) {
    count += iter.UserData()->mEntries.Count();
  }
  return count + mRequests.Count();
}

nsRefreshDriver::ObserverArray&
nsRefreshDriver::ArrayFor(mozFlushType aFlushType)
{
  switch (aFlushType) {
    case Flush_Style:
      return mObservers[0];
    case Flush_Layout:
      return mObservers[1];
    case Flush_Display:
      return mObservers[2];
    default:
      MOZ_ASSERT(false, "bad flush type");
      return *static_cast<ObserverArray*>(nullptr);
  }
}

/*
 * nsITimerCallback implementation
 */

void
nsRefreshDriver::DoTick()
{
  NS_PRECONDITION(!IsFrozen(), "Why are we notified while frozen?");
  NS_PRECONDITION(mPresContext, "Why are we notified after disconnection?");
  NS_PRECONDITION(!nsContentUtils::GetCurrentJSContext(),
                  "Shouldn't have a JSContext on the stack");

  if (mTestControllingRefreshes) {
    Tick(mMostRecentRefreshEpochTime, mMostRecentRefresh);
  } else {
    Tick(JS_Now(), TimeStamp::Now());
  }
}

struct DocumentFrameCallbacks {
  explicit DocumentFrameCallbacks(nsIDocument* aDocument) :
    mDocument(aDocument)
  {}

  nsCOMPtr<nsIDocument> mDocument;
  nsIDocument::FrameRequestCallbackList mCallbacks;
};

static nsDocShell* GetDocShell(nsPresContext* aPresContext)
{
  return static_cast<nsDocShell*>(aPresContext->GetDocShell());
}

static bool
HasPendingAnimations(nsIPresShell* aShell)
{
  nsIDocument* doc = aShell->GetDocument();
  if (!doc) {
    return false;
  }

  PendingAnimationTracker* tracker = doc->GetPendingAnimationTracker();
  return tracker && tracker->HasPendingAnimations();
}

/**
 * Return a list of all the child docShells in a given root docShell that are
 * visible and are recording markers for the profilingTimeline
 */
static void GetProfileTimelineSubDocShells(nsDocShell* aRootDocShell,
                                           nsTArray<nsDocShell*>& aShells)
{
  if (!aRootDocShell) {
    return;
  }

  RefPtr<TimelineConsumers> timelines = TimelineConsumers::Get();
  if (!timelines || timelines->IsEmpty()) {
    return;
  }

  nsCOMPtr<nsISimpleEnumerator> enumerator;
  nsresult rv = aRootDocShell->GetDocShellEnumerator(
    nsIDocShellTreeItem::typeAll,
    nsIDocShell::ENUMERATE_BACKWARDS,
    getter_AddRefs(enumerator));

  if (NS_FAILED(rv)) {
    return;
  }

  nsCOMPtr<nsIDocShell> curItem;
  bool hasMore = false;
  while (NS_SUCCEEDED(enumerator->HasMoreElements(&hasMore)) && hasMore) {
    nsCOMPtr<nsISupports> curSupports;
    enumerator->GetNext(getter_AddRefs(curSupports));
    curItem = do_QueryInterface(curSupports);

    if (!curItem || !curItem->GetRecordProfileTimelineMarkers()) {
      continue;
    }

    nsDocShell* shell = static_cast<nsDocShell*>(curItem.get());
    bool isVisible = false;
    shell->GetVisibility(&isVisible);
    if (!isVisible) {
      continue;
    }

    aShells.AppendElement(shell);
  }
}

static void
TakeFrameRequestCallbacksFrom(nsIDocument* aDocument,
                              nsTArray<DocumentFrameCallbacks>& aTarget)
{
  aTarget.AppendElement(aDocument);
  aDocument->TakeFrameRequestCallbacks(aTarget.LastElement().mCallbacks);
}

void
nsRefreshDriver::DispatchPendingEvents()
{
  // Swap out the current pending events
  nsTArray<PendingEvent> pendingEvents(Move(mPendingEvents));
  for (PendingEvent& event : pendingEvents) {
    bool dummy;
    event.mTarget->DispatchEvent(event.mEvent, &dummy);
  }
}

static bool
CollectDocuments(nsIDocument* aDocument, void* aDocArray)
{
  static_cast<nsCOMArray<nsIDocument>*>(aDocArray)->AppendObject(aDocument);
  aDocument->EnumerateSubDocuments(CollectDocuments, aDocArray);
  return true;
}

void
nsRefreshDriver::DispatchAnimationEvents()
{
  if (!mPresContext) {
    return;
  }

  nsCOMArray<nsIDocument> documents;
  CollectDocuments(mPresContext->Document(), &documents);

  for (int32_t i = 0; i < documents.Count(); ++i) {
    nsIDocument* doc = documents[i];
    nsIPresShell* shell = doc->GetShell();
    if (!shell) {
      continue;
    }

    RefPtr<nsPresContext> context = shell->GetPresContext();
    if (!context || context->RefreshDriver() != this) {
      continue;
    }

    context->TransitionManager()->SortEvents();
    context->AnimationManager()->SortEvents();

    // Dispatch transition events first since transitions conceptually sit
    // below animations in terms of compositing order.
    context->TransitionManager()->DispatchEvents();
    // Check that the presshell has not been destroyed
    if (context->GetPresShell()) {
      context->AnimationManager()->DispatchEvents();
    }
  }
}

void
nsRefreshDriver::RunFrameRequestCallbacks(TimeStamp aNowTime)
{
  // Grab all of our frame request callbacks up front.
  nsTArray<DocumentFrameCallbacks>
    frameRequestCallbacks(mFrameRequestCallbackDocs.Length() +
                          mThrottledFrameRequestCallbackDocs.Length());

  // First, grab throttled frame request callbacks.
  {
    nsTArray<nsIDocument*> docsToRemove;

    // We always tick throttled frame requests if the entire refresh driver is
    // throttled, because in that situation throttled frame requests tick at the
    // same frequency as non-throttled frame requests.
    bool tickThrottledFrameRequests = mThrottled;

    if (!tickThrottledFrameRequests &&
        aNowTime >= mNextThrottledFrameRequestTick) {
      mNextThrottledFrameRequestTick = aNowTime + mThrottledFrameRequestInterval;
      tickThrottledFrameRequests = true;
    }

    for (nsIDocument* doc : mThrottledFrameRequestCallbackDocs) {
      if (tickThrottledFrameRequests) {
        // We're ticking throttled documents, so grab this document's requests.
        // We don't bother appending to docsToRemove because we're going to
        // clear mThrottledFrameRequestCallbackDocs anyway.
        TakeFrameRequestCallbacksFrom(doc, frameRequestCallbacks);
      } else if (!doc->ShouldThrottleFrameRequests()) {
        // This document is no longer throttled, so grab its requests even
        // though we're not ticking throttled frame requests right now. If
        // this is the first unthrottled document with frame requests, we'll
        // enter high precision mode the next time the callback is scheduled.
        TakeFrameRequestCallbacksFrom(doc, frameRequestCallbacks);
        docsToRemove.AppendElement(doc);
      }
    }

    // Remove all the documents we're ticking from
    // mThrottledFrameRequestCallbackDocs so they can be readded as needed.
    if (tickThrottledFrameRequests) {
      mThrottledFrameRequestCallbackDocs.Clear();
    } else {
      // XXX(seth): We're using this approach to avoid concurrent modification
      // of mThrottledFrameRequestCallbackDocs. docsToRemove usually has either
      // zero elements or a very small number, so this should be OK in practice.
      for (nsIDocument* doc : docsToRemove) {
        mThrottledFrameRequestCallbackDocs.RemoveElement(doc);
      }
    }
  }

  // Now grab unthrottled frame request callbacks.
  for (nsIDocument* doc : mFrameRequestCallbackDocs) {
    TakeFrameRequestCallbacksFrom(doc, frameRequestCallbacks);
  }

  // Reset mFrameRequestCallbackDocs so they can be readded as needed.
  mFrameRequestCallbackDocs.Clear();

  if (!frameRequestCallbacks.IsEmpty()) {
    profiler_tracing("Paint", "Scripts", TRACING_INTERVAL_START);
    for (const DocumentFrameCallbacks& docCallbacks : frameRequestCallbacks) {
      // XXXbz Bug 863140: GetInnerWindow can return the outer
      // window in some cases.
      nsPIDOMWindowInner* innerWindow =
        docCallbacks.mDocument->GetInnerWindow();
      DOMHighResTimeStamp timeStamp = 0;
      if (innerWindow && innerWindow->IsInnerWindow()) {
        mozilla::dom::Performance* perf = innerWindow->GetPerformance();
        if (perf) {
          timeStamp = perf->GetDOMTiming()->TimeStampToDOMHighRes(aNowTime);
        }
        // else window is partially torn down already
      }
      for (auto& callback : docCallbacks.mCallbacks) {
        callback->Call(timeStamp);
      }
    }
    profiler_tracing("Paint", "Scripts", TRACING_INTERVAL_END);
  }
}

void
nsRefreshDriver::Tick(int64_t aNowEpoch, TimeStamp aNowTime)
{
  NS_PRECONDITION(!nsContentUtils::GetCurrentJSContext(),
                  "Shouldn't have a JSContext on the stack");

  if (nsNPAPIPluginInstance::InPluginCallUnsafeForReentry()) {
    NS_ERROR("Refresh driver should not run during plugin call!");
    // Try to survive this by just ignoring the refresh tick.
    return;
  }

  PROFILER_LABEL("nsRefreshDriver", "Tick",
    js::ProfileEntry::Category::GRAPHICS);

  // We're either frozen or we were disconnected (likely in the middle
  // of a tick iteration).  Just do nothing here, since our
  // prescontext went away.
  if (IsFrozen() || !mPresContext) {
    return;
  }

  // We can have a race condition where the vsync timestamp
  // is before the most recent refresh due to a forced refresh.
  // The underlying assumption is that the refresh driver tick can only
  // go forward in time, not backwards. To prevent the refresh
  // driver from going back in time, just skip this tick and
  // wait until the next tick.
  if ((aNowTime <= mMostRecentRefresh) && !mTestControllingRefreshes) {
    return;
  }

  TimeStamp previousRefresh = mMostRecentRefresh;

  mMostRecentRefresh = aNowTime;
  mMostRecentRefreshEpochTime = aNowEpoch;

  if (IsWaitingForPaint(aNowTime)) {
    // We're currently suspended waiting for earlier Tick's to
    // be completed (on the Compositor). Mark that we missed the paint
    // and keep waiting.
    return;
  }
  mMostRecentTick = aNowTime;
  if (mRootRefresh) {
    mRootRefresh->RemoveRefreshObserver(this, Flush_Style);
    mRootRefresh = nullptr;
  }
  mSkippedPaints = false;

  nsCOMPtr<nsIPresShell> presShell = mPresContext->GetPresShell();
  if (!presShell || (ObserverCount() == 0 && ImageRequestCount() == 0)) {
    // Things are being destroyed, or we no longer have any observers.
    // We don't want to stop the timer when observers are initially
    // removed, because sometimes observers can be added and removed
    // often depending on what other things are going on and in that
    // situation we don't want to thrash our timer.  So instead we
    // wait until we get a Notify() call when we have no observers
    // before stopping the timer.
    StopTimer();
    return;
  }

  mResizeSuppressed = false;

  AutoRestore<bool> restoreInRefresh(mInRefresh);
  mInRefresh = true;

  AutoRestore<TimeStamp> restoreTickStart(mTickStart);
  mTickStart = TimeStamp::Now();

  gfxPlatform::GetPlatform()->SchedulePaintIfDeviceReset();

  // We want to process any pending APZ metrics ahead of their positions
  // in the queue. This will prevent us from spending precious time
  // painting a stale displayport.
  if (gfxPrefs::APZPeekMessages()) {
    nsLayoutUtils::UpdateDisplayPortMarginsFromPendingMessages();
  }

  /*
   * The timer holds a reference to |this| while calling |Notify|.
   * However, implementations of |WillRefresh| are permitted to destroy
   * the pres context, which will cause our |mPresContext| to become
   * null.  If this happens, we must stop notifying observers.
   */
  for (uint32_t i = 0; i < ArrayLength(mObservers); ++i) {
    ObserverArray::EndLimitedIterator etor(mObservers[i]);
    while (etor.HasMore()) {
      RefPtr<nsARefreshObserver> obs = etor.GetNext();
      obs->WillRefresh(aNowTime);

      if (!mPresContext || !mPresContext->GetPresShell()) {
        StopTimer();
        return;
      }
    }

    if (i == 0) {
      // This is the Flush_Style case.

      DispatchAnimationEvents();
      DispatchPendingEvents();
      RunFrameRequestCallbacks(aNowTime);

      if (mPresContext && mPresContext->GetPresShell()) {
        bool tracingStyleFlush = false;
        AutoTArray<nsIPresShell*, 16> observers;
        observers.AppendElements(mStyleFlushObservers);
        for (uint32_t j = observers.Length();
             j && mPresContext && mPresContext->GetPresShell(); --j) {
          // Make sure to not process observers which might have been removed
          // during previous iterations.
          nsIPresShell* shell = observers[j - 1];
          if (!mStyleFlushObservers.Contains(shell))
            continue;

          if (!tracingStyleFlush) {
            tracingStyleFlush = true;
            profiler_tracing("Paint", "Styles", mStyleCause, TRACING_INTERVAL_START);
            mStyleCause = nullptr;
          }

          NS_ADDREF(shell);
          mStyleFlushObservers.RemoveElement(shell);
          RestyleManagerHandle restyleManager =
            shell->GetPresContext()->RestyleManager();
          // XXX stylo: ServoRestyleManager does not observer the refresh driver yet.
          if (restyleManager->IsGecko()) {
            restyleManager->AsGecko()->mObservingRefreshDriver = false;
          }
          shell->FlushPendingNotifications(ChangesToFlush(Flush_Style, false));
          // Inform the FontFaceSet that we ticked, so that it can resolve its
          // ready promise if it needs to (though it might still be waiting on
          // a layout flush).
          nsPresContext* presContext = shell->GetPresContext();
          if (presContext) {
            presContext->NotifyFontFaceSetOnRefresh();
          }
          NS_RELEASE(shell);

          mNeedToRecomputeVisibility = true;
        }


        if (tracingStyleFlush) {
          profiler_tracing("Paint", "Styles", TRACING_INTERVAL_END);
        }
      }
    } else if  (i == 1) {
      // This is the Flush_Layout case.
      bool tracingLayoutFlush = false;
      AutoTArray<nsIPresShell*, 16> observers;
      observers.AppendElements(mLayoutFlushObservers);
      for (uint32_t j = observers.Length();
           j && mPresContext && mPresContext->GetPresShell(); --j) {
        // Make sure to not process observers which might have been removed
        // during previous iterations.
        nsIPresShell* shell = observers[j - 1];
        if (!mLayoutFlushObservers.Contains(shell))
          continue;

        if (!tracingLayoutFlush) {
          tracingLayoutFlush = true;
          profiler_tracing("Paint", "Reflow", mReflowCause, TRACING_INTERVAL_START);
          mReflowCause = nullptr;
        }

        NS_ADDREF(shell);
        mLayoutFlushObservers.RemoveElement(shell);
        shell->mReflowScheduled = false;
        shell->mSuppressInterruptibleReflows = false;
        mozFlushType flushType = HasPendingAnimations(shell)
                               ? Flush_Layout
                               : Flush_InterruptibleLayout;
        shell->FlushPendingNotifications(ChangesToFlush(flushType, false));
        // Inform the FontFaceSet that we ticked, so that it can resolve its
        // ready promise if it needs to.
        nsPresContext* presContext = shell->GetPresContext();
        if (presContext) {
          presContext->NotifyFontFaceSetOnRefresh();
        }
        NS_RELEASE(shell);

        mNeedToRecomputeVisibility = true;
      }

      if (tracingLayoutFlush) {
        profiler_tracing("Paint", "Reflow", TRACING_INTERVAL_END);
      }
    }

    // The pres context may be destroyed during we do the flushing.
    if (!mPresContext || !mPresContext->GetPresShell()) {
      StopTimer();
      return;
    }
  }

  // Recompute approximate frame visibility if it's necessary and enough time
  // has passed since the last time we did it.
  if (mNeedToRecomputeVisibility && !mThrottled &&
      aNowTime >= mNextRecomputeVisibilityTick &&
      !presShell->IsPaintingSuppressed()) {
    mNextRecomputeVisibilityTick = aNowTime + mMinRecomputeVisibilityInterval;
    mNeedToRecomputeVisibility = false;

    presShell->ScheduleApproximateFrameVisibilityUpdateNow();
  }

  /*
   * Perform notification to imgIRequests subscribed to listen
   * for refresh events.
   */

  for (auto iter = mStartTable.Iter(); !iter.Done(); iter.Next()) {
    const uint32_t& delay = iter.Key();
    ImageStartData* data = iter.UserData();

    if (data->mStartTime) {
      TimeStamp& start = *data->mStartTime;
      TimeDuration prev = previousRefresh - start;
      TimeDuration curr = aNowTime - start;
      uint32_t prevMultiple = uint32_t(prev.ToMilliseconds()) / delay;

      // We want to trigger images' refresh if we've just crossed over a
      // multiple of the first image's start time. If so, set the animation
      // start time to the nearest multiple of the delay and move all the
      // images in this table to the main requests table.
      if (prevMultiple != uint32_t(curr.ToMilliseconds()) / delay) {
        mozilla::TimeStamp desired =
          start + TimeDuration::FromMilliseconds(prevMultiple * delay);
        BeginRefreshingImages(data->mEntries, desired);
      }
    } else {
      // This is the very first time we've drawn images with this time delay.
      // Set the animation start time to "now" and move all the images in this
      // table to the main requests table.
      mozilla::TimeStamp desired = aNowTime;
      BeginRefreshingImages(data->mEntries, desired);
      data->mStartTime.emplace(aNowTime);
    }
  }

  if (mRequests.Count()) {
    // RequestRefresh may run scripts, so it's not safe to directly call it
    // while using a hashtable enumerator to enumerate mRequests in case
    // script modifies the hashtable. Instead, we build a (local) array of
    // images to refresh, and then we refresh each image in that array.
    nsCOMArray<imgIContainer> imagesToRefresh(mRequests.Count());

    for (auto iter = mRequests.Iter(); !iter.Done(); iter.Next()) {
      nsISupportsHashKey* entry = iter.Get();
      auto req = static_cast<imgIRequest*>(entry->GetKey());
      MOZ_ASSERT(req, "Unable to retrieve the image request");
      nsCOMPtr<imgIContainer> image;
      if (NS_SUCCEEDED(req->GetImage(getter_AddRefs(image)))) {
        imagesToRefresh.AppendElement(image.forget());
      }
    }

    for (uint32_t i = 0; i < imagesToRefresh.Length(); i++) {
      imagesToRefresh[i]->RequestRefresh(aNowTime);
    }
  }

  for (nsIPresShell* shell : mPresShellsToInvalidateIfHidden) {
    shell->InvalidatePresShellIfHidden();
  }
  mPresShellsToInvalidateIfHidden.Clear();

  if (mViewManagerFlushIsPending) {
    RefPtr<TimelineConsumers> timelines = TimelineConsumers::Get();

    nsTArray<nsDocShell*> profilingDocShells;
    GetProfileTimelineSubDocShells(GetDocShell(mPresContext), profilingDocShells);
    for (nsDocShell* docShell : profilingDocShells) {
      // For the sake of the profile timeline's simplicity, this is flagged as
      // paint even if it includes creating display lists
      MOZ_ASSERT(timelines);
      MOZ_ASSERT(timelines->HasConsumer(docShell));
      timelines->AddMarkerForDocShell(docShell, "Paint",  MarkerTracingType::START);
    }

#ifdef MOZ_DUMP_PAINTING
    if (nsLayoutUtils::InvalidationDebuggingIsEnabled()) {
      printf_stderr("Starting ProcessPendingUpdates\n");
    }
#endif

    mViewManagerFlushIsPending = false;
    RefPtr<nsViewManager> vm = mPresContext->GetPresShell()->GetViewManager();
    vm->ProcessPendingUpdates();

#ifdef MOZ_DUMP_PAINTING
    if (nsLayoutUtils::InvalidationDebuggingIsEnabled()) {
      printf_stderr("Ending ProcessPendingUpdates\n");
    }
#endif

    for (nsDocShell* docShell : profilingDocShells) {
      MOZ_ASSERT(timelines);
      MOZ_ASSERT(timelines->HasConsumer(docShell));
      timelines->AddMarkerForDocShell(docShell, "Paint",  MarkerTracingType::END);
    }

    if (nsContentUtils::XPConnect()) {
      nsContentUtils::XPConnect()->NotifyDidPaint();
      nsJSContext::NotifyDidPaint();
    }
  }

#ifndef ANDROID  /* bug 1142079 */
  mozilla::Telemetry::AccumulateTimeDelta(mozilla::Telemetry::REFRESH_DRIVER_TICK, mTickStart);
#endif

  nsTObserverArray<nsAPostRefreshObserver*>::ForwardIterator iter(mPostRefreshObservers);
  while (iter.HasMore()) {
    nsAPostRefreshObserver* observer = iter.GetNext();
    observer->DidRefresh();
  }

  ConfigureHighPrecision();

  NS_ASSERTION(mInRefresh, "Still in refresh");
}

void
nsRefreshDriver::BeginRefreshingImages(RequestTable& aEntries,
                                       mozilla::TimeStamp aDesired)
{
  for (auto iter = aEntries.Iter(); !iter.Done(); iter.Next()) {
    auto req = static_cast<imgIRequest*>(iter.Get()->GetKey());
    MOZ_ASSERT(req, "Unable to retrieve the image request");

    mRequests.PutEntry(req);

    nsCOMPtr<imgIContainer> image;
    if (NS_SUCCEEDED(req->GetImage(getter_AddRefs(image)))) {
      image->SetAnimationStartTime(aDesired);
    }
  }
  aEntries.Clear();
}

void
nsRefreshDriver::Freeze()
{
  StopTimer();
  mFreezeCount++;
}

void
nsRefreshDriver::Thaw()
{
  NS_ASSERTION(mFreezeCount > 0, "Thaw() called on an unfrozen refresh driver");

  if (mFreezeCount > 0) {
    mFreezeCount--;
  }

  if (mFreezeCount == 0) {
    if (ObserverCount() || ImageRequestCount()) {
      // FIXME: This isn't quite right, since our EnsureTimerStarted call
      // updates our mMostRecentRefresh, but the DoRefresh call won't run
      // and notify our observers until we get back to the event loop.
      // Thus MostRecentRefresh() will lie between now and the DoRefresh.
      NS_DispatchToCurrentThread(NewRunnableMethod(this, &nsRefreshDriver::DoRefresh));
      EnsureTimerStarted();
    }
  }
}

void
nsRefreshDriver::FinishedWaitingForTransaction()
{
  mWaitingForTransaction = false;
  if (mSkippedPaints &&
      !IsInRefresh() &&
      (ObserverCount() || ImageRequestCount())) {
    profiler_tracing("Paint", "RD", TRACING_INTERVAL_START);
    DoRefresh();
    profiler_tracing("Paint", "RD", TRACING_INTERVAL_END);
  }
  mSkippedPaints = false;
}

uint64_t
nsRefreshDriver::GetTransactionId()
{
  ++mPendingTransaction;

  if (mPendingTransaction >= mCompletedTransaction + 2 &&
      !mWaitingForTransaction &&
      !mTestControllingRefreshes) {
    mWaitingForTransaction = true;
    mSkippedPaints = false;
  }

  return mPendingTransaction;
}

uint64_t
nsRefreshDriver::LastTransactionId() const
{
  return mPendingTransaction;
}

void
nsRefreshDriver::RevokeTransactionId(uint64_t aTransactionId)
{
  MOZ_ASSERT(aTransactionId == mPendingTransaction);
  if (mPendingTransaction == mCompletedTransaction + 2 &&
      mWaitingForTransaction) {
    MOZ_ASSERT(!mSkippedPaints, "How did we skip a paint when we're in the middle of one?");
    FinishedWaitingForTransaction();
  }
  mPendingTransaction--;
}

mozilla::TimeStamp
nsRefreshDriver::GetTransactionStart()
{
  return mTickStart;
}

void
nsRefreshDriver::NotifyTransactionCompleted(uint64_t aTransactionId)
{
  if (aTransactionId > mCompletedTransaction) {
    if (mPendingTransaction > mCompletedTransaction + 1 &&
        mWaitingForTransaction) {
      mCompletedTransaction = aTransactionId;
      FinishedWaitingForTransaction();
    } else {
      mCompletedTransaction = aTransactionId;
    }
  }
}

void
nsRefreshDriver::WillRefresh(mozilla::TimeStamp aTime)
{
  mRootRefresh->RemoveRefreshObserver(this, Flush_Style);
  mRootRefresh = nullptr;
  if (mSkippedPaints) {
    DoRefresh();
  }
}

bool
nsRefreshDriver::IsWaitingForPaint(mozilla::TimeStamp aTime)
{
  if (mTestControllingRefreshes) {
    return false;
  }
  // If we've skipped too many ticks then it's possible
  // that something went wrong and we're waiting on
  // a notification that will never arrive.
  if (aTime > (mMostRecentTick + TimeDuration::FromMilliseconds(200))) {
    mSkippedPaints = false;
    mWaitingForTransaction = false;
    if (mRootRefresh) {
      mRootRefresh->RemoveRefreshObserver(this, Flush_Style);
    }
    return false;
  }
  if (mWaitingForTransaction) {
    mSkippedPaints = true;
    return true;
  }

  // Try find the 'root' refresh driver for the current window and check
  // if that is waiting for a paint.
  nsPresContext *rootContext = PresContext()->GetRootPresContext();
  if (rootContext) {
    nsRefreshDriver *rootRefresh = rootContext->RefreshDriver();
    if (rootRefresh && rootRefresh != this) {
      if (rootRefresh->IsWaitingForPaint(aTime)) {
        if (mRootRefresh != rootRefresh) {
          if (mRootRefresh) {
            mRootRefresh->RemoveRefreshObserver(this, Flush_Style);
          }
          rootRefresh->AddRefreshObserver(this, Flush_Style);
          mRootRefresh = rootRefresh;
        }
        mSkippedPaints = true;
        return true;
      }
    }
  }
  return false;
}

void
nsRefreshDriver::SetThrottled(bool aThrottled)
{
  if (aThrottled != mThrottled) {
    mThrottled = aThrottled;
    if (mActiveTimer) {
      // We want to switch our timer type here, so just stop and
      // restart the timer.
      EnsureTimerStarted(eForceAdjustTimer);
    }
  }
}

/*static*/ void
nsRefreshDriver::PVsyncActorCreated(VsyncChild* aVsyncChild)
{
  MOZ_ASSERT(NS_IsMainThread());
  MOZ_ASSERT(!XRE_IsParentProcess());
  VsyncRefreshDriverTimer* vsyncRefreshDriverTimer =
                           new VsyncRefreshDriverTimer(aVsyncChild);

  // If we are using software timer, swap current timer to
  // VsyncRefreshDriverTimer.
  if (sRegularRateTimer) {
    sRegularRateTimer->SwapRefreshDrivers(vsyncRefreshDriverTimer);
    delete sRegularRateTimer;
  }
  sRegularRateTimer = vsyncRefreshDriverTimer;
}

void
nsRefreshDriver::DoRefresh()
{
  // Don't do a refresh unless we're in a state where we should be refreshing.
  if (!IsFrozen() && mPresContext && mActiveTimer) {
    DoTick();
  }
}

#ifdef DEBUG
bool
nsRefreshDriver::IsRefreshObserver(nsARefreshObserver* aObserver,
                                   mozFlushType aFlushType)
{
  ObserverArray& array = ArrayFor(aFlushType);
  return array.Contains(aObserver);
}
#endif

void
nsRefreshDriver::ScheduleViewManagerFlush()
{
  NS_ASSERTION(mPresContext->IsRoot(),
               "Should only schedule view manager flush on root prescontexts");
  mViewManagerFlushIsPending = true;
  EnsureTimerStarted(eNeverAdjustTimer);
}

void
nsRefreshDriver::ScheduleFrameRequestCallbacks(nsIDocument* aDocument)
{
  NS_ASSERTION(mFrameRequestCallbackDocs.IndexOf(aDocument) ==
               mFrameRequestCallbackDocs.NoIndex &&
               mThrottledFrameRequestCallbackDocs.IndexOf(aDocument) ==
               mThrottledFrameRequestCallbackDocs.NoIndex,
               "Don't schedule the same document multiple times");
  if (aDocument->ShouldThrottleFrameRequests()) {
    mThrottledFrameRequestCallbackDocs.AppendElement(aDocument);
  } else {
    mFrameRequestCallbackDocs.AppendElement(aDocument);
  }

  // make sure that the timer is running
  ConfigureHighPrecision();
  EnsureTimerStarted();
}

void
nsRefreshDriver::RevokeFrameRequestCallbacks(nsIDocument* aDocument)
{
  mFrameRequestCallbackDocs.RemoveElement(aDocument);
  mThrottledFrameRequestCallbackDocs.RemoveElement(aDocument);
  ConfigureHighPrecision();
  // No need to worry about restarting our timer in slack mode if it's already
  // running; that will happen automatically when it fires.
}

void
nsRefreshDriver::ScheduleEventDispatch(nsINode* aTarget, nsIDOMEvent* aEvent)
{
  mPendingEvents.AppendElement(PendingEvent{aTarget, aEvent});
  // make sure that the timer is running
  EnsureTimerStarted();
}

void
nsRefreshDriver::CancelPendingEvents(nsIDocument* aDocument)
{
  for (auto i : Reversed(MakeRange(mPendingEvents.Length()))) {
    if (mPendingEvents[i].mTarget->OwnerDoc() == aDocument) {
      mPendingEvents.RemoveElementAt(i);
    }
  }
}

void
nsRefreshDriver::Disconnect()
{
  MOZ_ASSERT(NS_IsMainThread());

  StopTimer();

  if (mPresContext) {
    mPresContext = nullptr;
    if (--sRefreshDriverCount == 0) {
      Shutdown();
    }
  }
}

/* static */ bool
nsRefreshDriver::IsJankCritical()
{
  MOZ_ASSERT(NS_IsMainThread());
  return sActiveVsyncTimers > 0;
}

/* static */ bool
nsRefreshDriver::GetJankLevels(Vector<uint64_t>& aJank) {
  aJank.clear();
  return aJank.append(sJankLevels, ArrayLength(sJankLevels));
}

#undef LOG