Quelle nsRefreshDriver.cpp Sprache: C

/* -*- 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/. */

/*
* 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.
*/

#include "nsRefreshDriver.h"
#include "mozilla/DataMutex.h"
#include "nsThreadUtils.h"

#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/AnimationEventDispatcher.h"
#include "mozilla/ArrayUtils.h"
#include "mozilla/Assertions.h"
#include "mozilla/AutoRestore.h"
#include "mozilla/BasePrincipal.h"
#include "mozilla/dom/MediaQueryList.h"
#include "mozilla/CycleCollectedJSContext.h"
#include "mozilla/DisplayPortUtils.h"
#include "mozilla/Hal.h"
#include "mozilla/InputTaskManager.h"
#include "mozilla/IntegerRange.h"
#include "mozilla/PresShell.h"
#include "mozilla/VsyncTaskManager.h"
#include "nsITimer.h"
#include "nsLayoutUtils.h"
#include "nsPresContext.h"
#include "imgRequest.h"
#include "nsComponentManagerUtils.h"
#include "mozilla/Logging.h"
#include "mozilla/dom/Document.h"
#include "mozilla/dom/DocumentTimeline.h"
#include "mozilla/dom/DocumentInlines.h"
#include "mozilla/dom/HTMLVideoElement.h"
#include "nsIXULRuntime.h"
#include "jsapi.h"
#include "nsContentUtils.h"
#include "nsTextFrame.h"
#include "mozilla/PendingFullscreenEvent.h"
#include "mozilla/dom/PerformanceMainThread.h"
#include "mozilla/Preferences.h"
#include "mozilla/StaticPrefs_apz.h"
#include "mozilla/StaticPrefs_gfx.h"
#include "mozilla/StaticPrefs_idle_period.h"
#include "mozilla/StaticPrefs_layout.h"
#include "mozilla/StaticPrefs_page_load.h"
#include "nsViewManager.h"
#include "GeckoProfiler.h"
#include "mozilla/dom/BrowserChild.h"
#include "mozilla/dom/CallbackDebuggerNotification.h"
#include "mozilla/dom/ContentChild.h"
#include "mozilla/dom/Event.h"
#include "mozilla/dom/Performance.h"
#include "mozilla/dom/Selection.h"
#include "mozilla/dom/VsyncMainChild.h"
#include "mozilla/dom/WindowBinding.h"
#include "mozilla/dom/LargestContentfulPaint.h"
#include "mozilla/layers/WebRenderLayerManager.h"
#include "mozilla/RestyleManager.h"
#include "mozilla/TaskController.h"
#include "imgIContainer.h"
#include "mozilla/dom/ScriptSettings.h"
#include "nsDocShell.h"
#include "nsISimpleEnumerator.h"
#include "nsJSEnvironment.h"
#include "mozilla/ScopeExit.h"
#include "mozilla/Telemetry.h"

#include "mozilla/ipc/BackgroundChild.h"
#include "mozilla/ipc/PBackgroundChild.h"
#include "VsyncSource.h"
#include "mozilla/VsyncDispatcher.h"
#include "mozilla/Unused.h"
#include "nsAnimationManager.h"
#include "nsDisplayList.h"
#include "nsDOMNavigationTiming.h"
#include "nsTransitionManager.h"

#if defined(MOZ_WIDGET_ANDROID)
#  include "VRManagerChild.h"
#endif  // defined(MOZ_WIDGET_ANDROID)

#include "nsXULPopupManager.h"

#include <numeric>

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

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

// after 10 minutes, stop firing off inactive timers
#define DEFAULT_INACTIVE_TIMER_DISABLE_SECONDS 600

// The number of seconds spent skipping frames because we are waiting for the
// compositor before logging.
#if defined(MOZ_ASAN)
#  define REFRESH_WAIT_WARNING 5
#elif defined(DEBUG) && !defined(MOZ_VALGRIND)
#  define REFRESH_WAIT_WARNING 5
#elif defined(DEBUG) && defined(MOZ_VALGRIND)
#  define REFRESH_WAIT_WARNING (RUNNING_ON_VALGRIND ? 20 : 5)
#elif defined(MOZ_VALGRIND)
#  define REFRESH_WAIT_WARNING (RUNNING_ON_VALGRIND ? 10 : 1)
#else
#  define REFRESH_WAIT_WARNING 1
#endif

MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(nsRefreshDriver::TickReasons);

namespace {
// 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

namespace mozilla {

static TimeStamp sMostRecentHighRateVsync;

static TimeDuration sMostRecentHighRate;

/*
* 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() = default;

  NS_INLINE_DECL_REFCOUNTING(RefreshDriverTimer)

  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();
    }
  }

  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* pc = aDriver->GetPresContext();
      nsPresContext* rootContext = pc ? pc->GetRootPresContext() : nullptr;
      // 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; }
  VsyncId MostRecentRefreshVsyncId() const { return mLastFireId; }
  virtual bool IsBlocked() { return false; }

  virtual TimeDuration GetTimerRate() = 0;

  TimeStamp GetIdleDeadlineHint(TimeStamp aDefault) {
    MOZ_ASSERT(NS_IsMainThread());

    if (!IsTicking() && !gfxPlatform::IsInLayoutAsapMode()) {
      return aDefault;
    }

    TimeStamp mostRecentRefresh = MostRecentRefresh();
    TimeDuration refreshPeriod = GetTimerRate();
    TimeStamp idleEnd = mostRecentRefresh + refreshPeriod;
    double highRateMultiplier = nsRefreshDriver::HighRateMultiplier();

    // If we haven't painted for some time, then guess that we won't paint
    // again for a while, so the refresh driver is not a good way to predict
    // idle time.
    if (highRateMultiplier == 1.0 &&
        (idleEnd +
             refreshPeriod *
                 StaticPrefs::layout_idle_period_required_quiescent_frames() <
         TimeStamp::Now())) {
      return aDefault;
    }

    // End the predicted idle time a little early, the amount controlled by a
    // pref, to prevent overrunning the idle time and delaying a frame.
    // But do that only if we aren't in high rate mode.
    idleEnd = idleEnd - TimeDuration::FromMilliseconds(
                            highRateMultiplier *
                            StaticPrefs::layout_idle_period_time_limit());
    return idleEnd < aDefault ? idleEnd : aDefault;
  }

  Maybe<TimeStamp> GetNextTickHint() {
    MOZ_ASSERT(NS_IsMainThread());
    TimeStamp nextTick = MostRecentRefresh() + GetTimerRate();
    return nextTick < TimeStamp::Now() ? Nothing() : Some(nextTick);
  }

  // Returns null if the RefreshDriverTimer is attached to several
  // RefreshDrivers. That may happen for example when there are
  // several windows open.
  nsPresContext* GetPresContextForOnlyRefreshDriver() {
    if (mRootRefreshDrivers.Length() == 1 && mContentRefreshDrivers.IsEmpty()) {
      return mRootRefreshDrivers[0]->GetPresContext();
    }
    if (mContentRefreshDrivers.Length() == 1 && mRootRefreshDrivers.IsEmpty()) {
      return mContentRefreshDrivers[0]->GetPresContext();
    }
    return nullptr;
  }

  bool IsAnyToplevelContentPageLoading() {
    for (nsTArray<RefPtr<nsRefreshDriver>>* drivers :
         {&mRootRefreshDrivers, &mContentRefreshDrivers}) {
      for (RefPtr<nsRefreshDriver>& driver : *drivers) {
        if (nsPresContext* pc = driver->GetPresContext()) {
          if (pc->Document()->IsTopLevelContentDocument() &&
              pc->Document()->GetReadyStateEnum() <
                  Document::READYSTATE_COMPLETE) {
            return true;
          }
        }
      }
    }

    return false;
  }

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

public:
  virtual bool IsTicking() const = 0;

protected:
  bool IsRootRefreshDriver(nsRefreshDriver* aDriver) {
    nsPresContext* pc = aDriver->GetPresContext();
    nsPresContext* rootContext = pc ? pc->GetRootPresContext() : nullptr;
    if (!rootContext) {
      return false;
    }

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

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

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

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

      TickDriver(driver, aId, aNow);
    }
  }

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

    mLastFireTime = now;
    mLastFireId = aId;

    LOG("[%p] ticking drivers...", this);

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

    LOG("[%p] done.", this);
  }

  static void TickDriver(nsRefreshDriver* driver, VsyncId aId, TimeStamp now) {
    driver->Tick(aId, now);
  }

  TimeStamp mLastFireTime;
  VsyncId mLastFireId;
  TimeStamp mTargetTime;

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

  // useful callback for nsITimer-based derived classes, here
  // because of c++ protected shenanigans
  static void TimerTick(nsITimer* aTimer, void* aClosure) {
    RefPtr<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 = NS_NewTimer();
  }

  virtual ~SimpleTimerBasedRefreshDriverTimer() override { StopTimer(); }

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

  double GetRate() const { return mRateMilliseconds; }

  TimeDuration GetTimerRate() override { return mRateDuration; }

protected:
  void StartTimer() override {
    // pretend we just fired, and we schedule the next tick normally
    mLastFireTime = TimeStamp::Now();
    mLastFireId = VsyncId();

    mTargetTime = mLastFireTime + mRateDuration;

    uint32_t delay = static_cast<uint32_t>(mRateMilliseconds);
    mTimer->InitWithNamedFuncCallback(
        TimerTick, this, delay, nsITimer::TYPE_ONE_SHOT,
        "SimpleTimerBasedRefreshDriverTimer::StartTimer");
  }

  void StopTimer() override { 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:
  // This is used in the parent process for all platforms except Linux Wayland.
  static RefPtr<VsyncRefreshDriverTimer>
  CreateForParentProcessWithGlobalVsync() {
    MOZ_RELEASE_ASSERT(XRE_IsParentProcess());
    MOZ_RELEASE_ASSERT(NS_IsMainThread());
    RefPtr<VsyncDispatcher> vsyncDispatcher =
        gfxPlatform::GetPlatform()->GetGlobalVsyncDispatcher();
    RefPtr<VsyncRefreshDriverTimer> timer =
        new VsyncRefreshDriverTimer(std::move(vsyncDispatcher), nullptr);
    return timer.forget();
  }

  // This is used in the parent process for Linux Wayland only, where we have a
  // per-widget VsyncSource which is independent from the gfxPlatform's global
  // VsyncSource.
  static RefPtr<VsyncRefreshDriverTimer>
  CreateForParentProcessWithLocalVsyncDispatcher(
      RefPtr<VsyncDispatcher>&& aVsyncDispatcher) {
    MOZ_RELEASE_ASSERT(XRE_IsParentProcess());
    MOZ_RELEASE_ASSERT(NS_IsMainThread());
    RefPtr<VsyncRefreshDriverTimer> timer =
        new VsyncRefreshDriverTimer(std::move(aVsyncDispatcher), nullptr);
    return timer.forget();
  }

  // This is used in the content process.
  static RefPtr<VsyncRefreshDriverTimer> CreateForContentProcess(
      RefPtr<VsyncMainChild>&& aVsyncChild) {
    MOZ_RELEASE_ASSERT(XRE_IsContentProcess());
    MOZ_RELEASE_ASSERT(NS_IsMainThread());
    RefPtr<VsyncRefreshDriverTimer> timer =
        new VsyncRefreshDriverTimer(nullptr, std::move(aVsyncChild));
    return timer.forget();
  }

  TimeDuration GetTimerRate() override {
    if (mVsyncDispatcher) {
      mVsyncRate = mVsyncDispatcher->GetVsyncRate();
    } else if (mVsyncChild) {
      mVsyncRate = mVsyncChild->GetVsyncRate();
    }

    // If hardware queries fail / are unsupported, we have to just guess.
    return mVsyncRate != TimeDuration::Forever()
               ? mVsyncRate
               : TimeDuration::FromMilliseconds(1000.0 / 60.0);
  }

  bool IsBlocked() override {
    return !mSuspendVsyncPriorityTicksUntil.IsNull() &&
           mSuspendVsyncPriorityTicksUntil > TimeStamp::Now() &&
           ShouldGiveNonVsyncTasksMoreTime();
  }

private:
  // RefreshDriverVsyncObserver redirects vsync notifications to the main thread
  // and calls VsyncRefreshDriverTimer::NotifyVsyncOnMainThread on it. It also
  // acts as a weak reference to the refresh driver timer, dropping its
  // reference when RefreshDriverVsyncObserver::Shutdown is called from the
  // timer's destructor.
  //
  // RefreshDriverVsyncObserver::NotifyVsync is called from different places
  // depending on the process type.
  //
  // Parent process:
  // NotifyVsync is called by RefreshDriverVsyncDispatcher, on a background
  // thread. RefreshDriverVsyncDispatcher keeps strong references to its
  // VsyncObservers, both in its array of observers and while calling
  // NotifyVsync. So it might drop its last reference to the observer on a
  // background thread. This means that the VsyncRefreshDriverTimer itself can't
  // be the observer (because its destructor would potentially be run on a
  // background thread), and it's why we use this separate class.
  //
  // Child process:
  // NotifyVsync is called by VsyncMainChild, on the main thread.
  // VsyncMainChild keeps raw pointers to its observers.
  class RefreshDriverVsyncObserver final : public VsyncObserver {
    NS_INLINE_DECL_THREADSAFE_REFCOUNTING(
        VsyncRefreshDriverTimer::RefreshDriverVsyncObserver, override)

   public:
    explicit RefreshDriverVsyncObserver(
        VsyncRefreshDriverTimer* aVsyncRefreshDriverTimer)
        : mVsyncRefreshDriverTimer(aVsyncRefreshDriverTimer),
          mLastPendingVsyncNotification(
              "RefreshDriverVsyncObserver::mLastPendingVsyncNotification") {
      MOZ_ASSERT(NS_IsMainThread());
    }

    void NotifyVsync(const VsyncEvent& aVsync) override {
      // 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
        auto pendingVsync = mLastPendingVsyncNotification.Lock();
        bool hadPendingVsync = pendingVsync->isSome();
        *pendingVsync = Some(aVsync);
        if (hadPendingVsync) {
          return;
        }
      }

      if (XRE_IsContentProcess()) {
        // In the content process, NotifyVsync is called by VsyncMainChild on
        // the main thread. No need to use a runnable, just call
        // NotifyVsyncTimerOnMainThread() directly.
        NotifyVsyncTimerOnMainThread();
        return;
      }

      // In the parent process, NotifyVsync is called on the vsync thread, which
      // on most platforms is different from the main thread, so we need to
      // dispatch a runnable for running NotifyVsyncTimerOnMainThread on the
      // main thread.
      // TODO: On Linux Wayland, the vsync thread is currently the main thread,
      // and yet we still dispatch the runnable. Do we need to?
      bool useVsyncPriority = mozilla::BrowserTabsRemoteAutostart();
      nsCOMPtr<nsIRunnable> vsyncEvent = new PrioritizableRunnable(
          NS_NewRunnableFunction(
              "RefreshDriverVsyncObserver::NotifyVsyncTimerOnMainThread",
              [self = RefPtr{this}]() {
                self->NotifyVsyncTimerOnMainThread();
              }),
          useVsyncPriority ? nsIRunnablePriority::PRIORITY_VSYNC
                           : nsIRunnablePriority::PRIORITY_NORMAL);
      NS_DispatchToMainThread(vsyncEvent);
    }

    void NotifyVsyncTimerOnMainThread() {
      MOZ_ASSERT(NS_IsMainThread());

      if (!mVsyncRefreshDriverTimer) {
        // Ignore calls after Shutdown.
        return;
      }

      VsyncEvent vsyncEvent;
      {
        // Get the last of the queued-up vsync notifications.
        auto pendingVsync = mLastPendingVsyncNotification.Lock();
        MOZ_RELEASE_ASSERT(
            pendingVsync->isSome(),
            "We should always have a pending vsync notification here.");
        vsyncEvent = pendingVsync->extract();
      }

      // Call VsyncRefreshDriverTimer::NotifyVsyncOnMainThread, and keep a
      // strong reference to it while calling the method.
      RefPtr<VsyncRefreshDriverTimer> timer = mVsyncRefreshDriverTimer;
      timer->NotifyVsyncOnMainThread(vsyncEvent);
    }

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

   private:
    ~RefreshDriverVsyncObserver() = default;

    // VsyncRefreshDriverTimer holds this RefreshDriverVsyncObserver and it will
    // be always available before Shutdown(). We can just use the raw pointer
    // here.
    // Only accessed on the main thread.
    VsyncRefreshDriverTimer* mVsyncRefreshDriverTimer;

    // Non-empty between a call to NotifyVsync and a call to
    // NotifyVsyncOnMainThread. When multiple vsync notifications have been
    // received between those two calls, this contains the last of the pending
    // notifications. This is used both in the parent process and in the child
    // process, but it only does something useful in the parent process. In the
    // child process, both calls happen on the main thread right after one
    // another, so there's only one notification to keep track of; vsync
    // notification coalescing for child processes happens at the IPC level
    // instead.
    DataMutex<Maybe<VsyncEvent>> mLastPendingVsyncNotification;

  };  // RefreshDriverVsyncObserver

  VsyncRefreshDriverTimer(RefPtr<VsyncDispatcher>&& aVsyncDispatcher,
                          RefPtr<VsyncMainChild>&& aVsyncChild)
      : mVsyncDispatcher(aVsyncDispatcher),
        mVsyncChild(aVsyncChild),
        mVsyncRate(TimeDuration::Forever()),
        mRecentVsync(TimeStamp::Now()),
        mLastTickStart(TimeStamp::Now()),
        mLastIdleTaskCount(0),
        mLastRunOutOfMTTasksCount(0),
        mProcessedVsync(true),
        mHasPendingLowPrioTask(false) {
    mVsyncObserver = new RefreshDriverVsyncObserver(this);
  }

  ~VsyncRefreshDriverTimer() override {
    if (mVsyncDispatcher) {
      mVsyncDispatcher->RemoveVsyncObserver(mVsyncObserver);
      mVsyncDispatcher = nullptr;
    } else if (mVsyncChild) {
      mVsyncChild->RemoveChildRefreshTimer(mVsyncObserver);
      mVsyncChild = nullptr;
    }

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

  bool ShouldGiveNonVsyncTasksMoreTime(bool aCheckOnlyNewPendingTasks = false) {
    TaskController* taskController = TaskController::Get();
    IdleTaskManager* idleTaskManager = taskController->GetIdleTaskManager();
    VsyncTaskManager* vsyncTaskManager = VsyncTaskManager::Get();

    // Note, pendingTaskCount includes also all the pending idle and vsync
    // tasks.
    uint64_t pendingTaskCount =
        taskController->PendingMainthreadTaskCountIncludingSuspended();
    uint64_t pendingIdleTaskCount = idleTaskManager->PendingTaskCount();
    uint64_t pendingVsyncTaskCount = vsyncTaskManager->PendingTaskCount();
    if (!(pendingTaskCount > (pendingIdleTaskCount + pendingVsyncTaskCount))) {
      return false;
    }
    if (aCheckOnlyNewPendingTasks) {
      return true;
    }

    uint64_t idleTaskCount = idleTaskManager->ProcessedTaskCount();

    // If we haven't processed new idle tasks and we have pending
    // non-idle tasks, give those non-idle tasks more time,
    // but only if the main thread wasn't totally empty at some point.
    // In the parent process RunOutOfMTTasksCount() is less meaningful
    // because some of the tasks run through AppShell.
    return mLastIdleTaskCount == idleTaskCount &&
           (taskController->RunOutOfMTTasksCount() ==
                mLastRunOutOfMTTasksCount ||
            XRE_IsParentProcess());
  }

  void NotifyVsyncOnMainThread(const VsyncEvent& aVsyncEvent) {
    MOZ_ASSERT(NS_IsMainThread());

    mRecentVsync = aVsyncEvent.mTime;
    mRecentVsyncId = aVsyncEvent.mId;
    if (!mSuspendVsyncPriorityTicksUntil.IsNull() &&
        mSuspendVsyncPriorityTicksUntil > TimeStamp::Now()) {
      if (ShouldGiveNonVsyncTasksMoreTime()) {
        if (!IsAnyToplevelContentPageLoading()) {
          // If pages aren't loading and there aren't other tasks to run,
          // trigger the pending vsync notification.
          mPendingVsync = mRecentVsync;
          mPendingVsyncId = mRecentVsyncId;
          if (!mHasPendingLowPrioTask) {
            mHasPendingLowPrioTask = true;
            NS_DispatchToMainThreadQueue(
                NS_NewRunnableFunction(
                    "NotifyVsyncOnMainThread[low priority]",
                    [self = RefPtr{this}]() {
                      self->mHasPendingLowPrioTask = false;
                      if (self->mRecentVsync == self->mPendingVsync &&
                          self->mRecentVsyncId == self->mPendingVsyncId &&
                          !self->ShouldGiveNonVsyncTasksMoreTime()) {
                        self->mSuspendVsyncPriorityTicksUntil = TimeStamp();
                        self->NotifyVsyncOnMainThread({self->mPendingVsyncId,
                                                       self->mPendingVsync,
                                                       /* unused */
                                                       TimeStamp()});
                      }
                    }),
                EventQueuePriority::Low);
          }
        }
        return;
      }

      // Clear the value since we aren't blocking anymore because there aren't
      // any non-idle tasks to process.
      mSuspendVsyncPriorityTicksUntil = TimeStamp();
    }

    if (StaticPrefs::layout_lower_priority_refresh_driver_during_load() &&
        ShouldGiveNonVsyncTasksMoreTime()) {
      nsPresContext* pctx = GetPresContextForOnlyRefreshDriver();
      if (pctx && pctx->HadFirstContentfulPaint() && pctx->Document() &&
          pctx->Document()->GetReadyStateEnum() <
              Document::READYSTATE_COMPLETE) {
        nsPIDOMWindowInner* win = pctx->Document()->GetInnerWindow();
        uint32_t frameRateMultiplier = pctx->GetNextFrameRateMultiplier();
        if (!frameRateMultiplier) {
          pctx->DidUseFrameRateMultiplier();
        }
        if (win && frameRateMultiplier) {
          dom::Performance* perf = win->GetPerformance();
          // Limit slower refresh rate to 5 seconds between the
          // first contentful paint and page load.
          if (perf &&
              perf->Now() < StaticPrefs::page_load_deprioritization_period()) {
            if (mProcessedVsync) {
              mProcessedVsync = false;
              TimeDuration rate = GetTimerRate();
              uint32_t slowRate = static_cast<uint32_t>(rate.ToMilliseconds() *
                                                        frameRateMultiplier);
              pctx->DidUseFrameRateMultiplier();
              nsCOMPtr<nsIRunnable> vsyncEvent = NewRunnableMethod<>(
                  "VsyncRefreshDriverTimer::IdlePriorityNotify", this,
                  &VsyncRefreshDriverTimer::IdlePriorityNotify);
              NS_DispatchToCurrentThreadQueue(vsyncEvent.forget(), slowRate,
                                              EventQueuePriority::Idle);
            }
            return;
          }
        }
      }
    }

    TickRefreshDriver(aVsyncEvent.mId, aVsyncEvent.mTime);
  }

  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);
    } else if (mVsyncRate != TimeDuration::Forever()) {
      TimeDuration contentDelay =
          (TimeStamp::Now() - mLastTickStart) - 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);
    } else {
      // Request the vsync rate which VsyncChild stored the last time it got a
      // vsync notification.
      mVsyncRate = mVsyncChild->GetVsyncRate();
    }
#endif
  }

  void OnTimerStart() {
    mLastTickStart = TimeStamp::Now();
    mLastTickEnd = TimeStamp();
    mLastIdleTaskCount = 0;
  }

  void IdlePriorityNotify() {
    if (mLastProcessedTick.IsNull() || mRecentVsync > mLastProcessedTick) {
      // mSuspendVsyncPriorityTicksUntil is for high priority vsync
      // notifications only.
      mSuspendVsyncPriorityTicksUntil = TimeStamp();
      TickRefreshDriver(mRecentVsyncId, mRecentVsync);
    }

    mProcessedVsync = true;
  }

  hal::PerformanceHintSession* GetPerformanceHintSession() {
    // The ContentChild creates/destroys the PerformanceHintSession in response
    // to the process' priority being foregrounded/backgrounded. We can only use
    // this session when using a single vsync source for the process, otherwise
    // these threads may be performing work for multiple
    // VsyncRefreshDriverTimers and we will misreport the work duration.
    const ContentChild* contentChild = ContentChild::GetSingleton();
    if (contentChild && mVsyncChild) {
      return contentChild->PerformanceHintSession();
    }

    return nullptr;
  }

  void TickRefreshDriver(VsyncId aId, TimeStamp aVsyncTimestamp) {
    MOZ_ASSERT(NS_IsMainThread());

    RecordTelemetryProbes(aVsyncTimestamp);

    TimeStamp tickStart = TimeStamp::Now();

    const TimeDuration previousRate = mVsyncRate;
    const TimeDuration rate = GetTimerRate();

    if (rate != previousRate) {
      if (auto* const performanceHintSession = GetPerformanceHintSession()) {
        performanceHintSession->UpdateTargetWorkDuration(
            ContentChild::GetPerformanceHintTarget(rate));
      }
    }

    if (TimeDuration::FromMilliseconds(nsRefreshDriver::DefaultInterval()) >
        rate) {
      sMostRecentHighRateVsync = tickStart;
      sMostRecentHighRate = rate;
    }

    // On 32-bit Windows we sometimes get times where TimeStamp::Now() is not
    // monotonic because the underlying system apis produce non-monontonic
    // results. (bug 1306896)
#if !defined(_WIN32)
    MOZ_ASSERT(aVsyncTimestamp <= tickStart);
#endif

    bool shouldGiveNonVSyncTasksMoreTime = ShouldGiveNonVsyncTasksMoreTime();

    // Set these variables before calling RunRefreshDrivers so that they are
    // visible to any nested ticks.
    mLastTickStart = tickStart;
    mLastProcessedTick = aVsyncTimestamp;

    RunRefreshDrivers(aId, aVsyncTimestamp);

    TimeStamp tickEnd = TimeStamp::Now();

    if (auto* const performanceHintSession = GetPerformanceHintSession()) {
      performanceHintSession->ReportActualWorkDuration(tickEnd - tickStart);
    }

    // Re-read mLastTickStart in case there was a nested tick inside this
    // tick.
    TimeStamp mostRecentTickStart = mLastTickStart;

    // Let also non-RefreshDriver code to run at least for awhile if we have
    // a mVsyncRefreshDriverTimer.
    // Always give a tiny bit, 5% of the vsync interval, time outside the
    // tick
    // In case there are both normal tasks and RefreshDrivers are doing
    // work, mSuspendVsyncPriorityTicksUntil will be set to a timestamp in the
    // future where the period between the previous tick start
    // (mostRecentTickStart) and the next tick needs to be at least the amount
    // of work normal tasks and RefreshDrivers did together (minus short grace
    // period).
    TimeDuration gracePeriod = rate / int64_t(20);

    if (shouldGiveNonVSyncTasksMoreTime && !mLastTickEnd.IsNull() &&
        XRE_IsContentProcess() &&
        // For RefreshDriver scheduling during page load there is currently
        // idle priority based setup.
        // XXX Consider to remove the page load specific code paths.
        !IsAnyToplevelContentPageLoading()) {
      // In case normal tasks are doing lots of work, we still want to paint
      // every now and then, so only at maximum 4 * rate of work is counted
      // here.
      // If we're giving extra time for tasks outside a tick, try to
      // ensure the next vsync after that period is handled, so subtract
      // a grace period.
      TimeDuration timeForOutsideTick = std::clamp(
          tickStart - mLastTickEnd - gracePeriod, gracePeriod, rate * 4);
      mSuspendVsyncPriorityTicksUntil = tickEnd + timeForOutsideTick;
    } else if (ShouldGiveNonVsyncTasksMoreTime(true)) {
      // We've got some new tasks, give them some extra time.
      // This handles also the case when mLastTickEnd.IsNull() above and we
      // should give some more time for non-vsync tasks.
      mSuspendVsyncPriorityTicksUntil = tickEnd + gracePeriod;
    } else {
      mSuspendVsyncPriorityTicksUntil = mostRecentTickStart + gracePeriod;
    }

    mLastIdleTaskCount =
        TaskController::Get()->GetIdleTaskManager()->ProcessedTaskCount();
    mLastRunOutOfMTTasksCount = TaskController::Get()->RunOutOfMTTasksCount();
    mLastTickEnd = tickEnd;
  }

  void StartTimer() override {
    MOZ_ASSERT(NS_IsMainThread());

    mLastFireTime = TimeStamp::Now();
    mLastFireId = VsyncId();

    if (mVsyncDispatcher) {
      mVsyncDispatcher->AddVsyncObserver(mVsyncObserver);
    } else if (mVsyncChild) {
      mVsyncChild->AddChildRefreshTimer(mVsyncObserver);
      OnTimerStart();
    }
    mIsTicking = true;
  }

  void StopTimer() override {
    MOZ_ASSERT(NS_IsMainThread());

    if (mVsyncDispatcher) {
      mVsyncDispatcher->RemoveVsyncObserver(mVsyncObserver);
    } else if (mVsyncChild) {
      mVsyncChild->RemoveChildRefreshTimer(mVsyncObserver);
    }
    mIsTicking = false;
  }

public:
  bool IsTicking() const override { return mIsTicking; }

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

  void RunRefreshDrivers(VsyncId aId, TimeStamp aTimeStamp) {
    Tick(aId, aTimeStamp);
    for (auto& driver : mContentRefreshDrivers) {
      driver->FinishedVsyncTick();
    }
    for (auto& driver : mRootRefreshDrivers) {
      driver->FinishedVsyncTick();
    }
  }

  // Always non-null. Has a weak pointer to us and notifies us of vsync.
  RefPtr<RefreshDriverVsyncObserver> mVsyncObserver;

  // Used in the parent process. We register mVsyncObserver with it for the
  // duration during which we want to receive vsync notifications. We also
  // use it to query the current vsync rate.
  RefPtr<VsyncDispatcher> mVsyncDispatcher;
  // Used it the content process. We register mVsyncObserver with it for the
  // duration during which we want to receive vsync notifications. The
  // mVsyncChild will be always available before VsyncChild::ActorDestroy().
  // After ActorDestroy(), StartTimer() and StopTimer() calls will be non-op.
  RefPtr<VsyncMainChild> mVsyncChild;

  TimeDuration mVsyncRate;
  bool mIsTicking = false;

  TimeStamp mRecentVsync;
  VsyncId mRecentVsyncId;
  // The local start time when RefreshDrivers' Tick was called last time.
  TimeStamp mLastTickStart;
  // The local end time of the last RefreshDrivers' tick.
  TimeStamp mLastTickEnd;
  // The number of idle tasks the main thread has processed. It is updated
  // right after RefreshDrivers' tick.
  uint64_t mLastIdleTaskCount;
  // If there were no idle tasks, we need to check if the main event queue
  // was totally empty at times.
  uint64_t mLastRunOutOfMTTasksCount;
  // Note, mLastProcessedTick stores the vsync timestamp, which may be coming
  // from a different process.
  TimeStamp mLastProcessedTick;
  // mSuspendVsyncPriorityTicksUntil is used to block too high refresh rate in
  // case the main thread has also other non-idle tasks to process.
  // The timestamp is effectively mLastTickEnd + some duration.
  TimeStamp mSuspendVsyncPriorityTicksUntil;
  bool mProcessedVsync;

  TimeStamp mPendingVsync;
  VsyncId mPendingVsyncId;
  bool mHasPendingLowPrioTask;
};  // 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:
  void ScheduleNextTick(TimeStamp aNowTime) override {
    // 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->InitWithNamedFuncCallback(
        TimerTick, this, delay, nsITimer::TYPE_ONE_SHOT,
        "StartupRefreshDriverTimer::ScheduleNextTick");
    mTargetTime = newTarget;
  }

public:
  bool IsTicking() const override { return true; }
};

/*
* 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) {}

  void AddRefreshDriver(nsRefreshDriver* aDriver) override {
    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();
  }

  TimeDuration GetTimerRate() override {
    return TimeDuration::FromMilliseconds(mNextTickDuration);
  }

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

  void StartTimer() override {
    mLastFireTime = TimeStamp::Now();
    mLastFireId = VsyncId();

    mTargetTime = mLastFireTime + mRateDuration;

    uint32_t delay = static_cast<uint32_t>(mRateMilliseconds);
    mTimer->InitWithNamedFuncCallback(TimerTickOne, this, delay,
                                      nsITimer::TYPE_ONE_SHOT,
                                      "InactiveRefreshDriverTimer::StartTimer");
    mIsTicking = true;
  }

  void StopTimer() override {
    mTimer->Cancel();
    mIsTicking = false;
  }

  void ScheduleNextTick(TimeStamp aNowTime) override {
    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->InitWithNamedFuncCallback(
        TimerTickOne, this, delay, nsITimer::TYPE_ONE_SHOT,
        "InactiveRefreshDriverTimer::ScheduleNextTick");

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

public:
  bool IsTicking() const override { return mIsTicking; }

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

    ScheduleNextTick(now);

    mLastFireTime = now;
    mLastFireId = VsyncId();

    nsTArray<RefPtr<nsRefreshDriver>> drivers(mContentRefreshDrivers.Clone());
    drivers.AppendElements(mRootRefreshDrivers);
    size_t index = mNextDriverIndex;

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

    mNextDriverIndex++;
  }

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

  double mNextTickDuration;
  double mDisableAfterMilliseconds;
  uint32_t mNextDriverIndex;
  bool mIsTicking = false;
};

}  // namespace mozilla

static StaticRefPtr<RefreshDriverTimer> sRegularRateTimer;
static StaticAutoPtr<nsTArray<RefreshDriverTimer*>> sRegularRateTimerList;
static StaticRefPtr<InactiveRefreshDriverTimer> sThrottledRateTimer;

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

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

  if (!mOwnTimer) {
    // If available, we fetch the widget-specific vsync source.
    nsPresContext* pc = GetPresContext();
    nsCOMPtr<nsIWidget> widget = pc->GetRootWidget();
    if (widget) {
      if (RefPtr<VsyncDispatcher> vsyncDispatcher =
              widget->GetVsyncDispatcher()) {
        mOwnTimer = VsyncRefreshDriverTimer::
            CreateForParentProcessWithLocalVsyncDispatcher(
                std::move(vsyncDispatcher));
        sRegularRateTimerList->AppendElement(mOwnTimer.get());
        return;
      }
      if (BrowserChild* browserChild = widget->GetOwningBrowserChild()) {
        if (RefPtr<VsyncMainChild> vsyncChildViaPBrowser =
                browserChild->GetVsyncChild()) {
          mOwnTimer = VsyncRefreshDriverTimer::CreateForContentProcess(
              std::move(vsyncChildViaPBrowser));
          sRegularRateTimerList->AppendElement(mOwnTimer.get());
          return;
        }
      }
    }
  }
  if (!sRegularRateTimer) {
    if (XRE_IsParentProcess()) {
      // Make sure all vsync systems are ready.
      gfxPlatform::GetPlatform();
      // In parent process, we can create the VsyncRefreshDriverTimer directly.
      sRegularRateTimer =
          VsyncRefreshDriverTimer::CreateForParentProcessWithGlobalVsync();
    } else {
      PBackgroundChild* actorChild =
          BackgroundChild::GetOrCreateForCurrentThread();
      if (NS_WARN_IF(!actorChild)) {
        return;
      }

      auto vsyncChildViaPBackground = MakeRefPtr<dom::VsyncMainChild>();
      dom::PVsyncChild* actor =
          actorChild->SendPVsyncConstructor(vsyncChildViaPBackground);
      if (NS_WARN_IF(!actor)) {
        return;
      }

      RefPtr<RefreshDriverTimer> vsyncRefreshDriverTimer =
          VsyncRefreshDriverTimer::CreateForContentProcess(
              std::move(vsyncChildViaPBackground));

      sRegularRateTimer = std::move(vsyncRefreshDriverTimer);
    }
  }
}

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() {
  MOZ_ASSERT(NS_IsMainThread());
  // clean up our timers
  sRegularRateTimer = nullptr;
  sRegularRateTimerList = nullptr;
  sThrottledRateTimer = nullptr;
}

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

/* static */
double nsRefreshDriver::HighRateMultiplier() {
  // We're in high rate mode if we've gotten a fast rate during the last
  // DefaultInterval().
  bool inHighRateMode =
      !gfxPlatform::IsInLayoutAsapMode() &&
      StaticPrefs::layout_expose_high_rate_mode_from_refreshdriver() &&
      !sMostRecentHighRateVsync.IsNull() &&
      (sMostRecentHighRateVsync +
       TimeDuration::FromMilliseconds(DefaultInterval())) > TimeStamp::Now();
  if (!inHighRateMode) {
    // Clear the timestamp so that the next call is faster.
    sMostRecentHighRateVsync = TimeStamp();
    sMostRecentHighRate = TimeDuration();
    return 1.0;
  }

  return sMostRecentHighRate.ToMilliseconds() / DefaultInterval();
}

// 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() const {
  int32_t rate = Preferences::GetInt("layout.frame_rate", -1);
  if (rate < 0) {
    rate = gfxPlatform::GetDefaultFrameRate();
  } else if (rate == 0) {
    rate = 10000;
  }

  return 1000.0 / rate;
}

/* static */
double nsRefreshDriver::GetThrottledTimerInterval() {
  uint32_t rate = StaticPrefs::layout_throttled_frame_rate();
  return 1000.0 / rate;
}

/* static */
TimeDuration nsRefreshDriver::GetMinRecomputeVisibilityInterval() {
  return TimeDuration::FromMilliseconds(
      StaticPrefs::layout_visibility_min_recompute_interval_ms());
}

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

  if (!mOwnTimer) {
    CreateVsyncRefreshTimer();
  }

  if (mOwnTimer) {
    return mOwnTimer.get();
  }

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

  return sRegularRateTimer;
}

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

nsRefreshDriver::nsRefreshDriver(nsPresContext* aPresContext)
    : mActiveTimer(nullptr),
      mOwnTimer(nullptr),
      mPresContext(aPresContext),
      mRootRefresh(nullptr),
      mNextTransactionId{0},
      mFreezeCount(0),
      mThrottledFrameRequestInterval(
          TimeDuration::FromMilliseconds(GetThrottledTimerInterval())),
      mMinRecomputeVisibilityInterval(GetMinRecomputeVisibilityInterval()),
      mThrottled(false),
      mNeedToRecomputeVisibility(false),
      mTestControllingRefreshes(false),
      mViewManagerFlushIsPending(false),
      mHasScheduleFlush(false),
      mInRefresh(false),
      mWaitingForTransaction(false),
      mSkippedPaints(false),
      mResizeSuppressed(false),
      mNeedToUpdateIntersectionObservations(false),
      mNeedToUpdateResizeObservers(false),
      mNeedToUpdateViewTransitions(false),
      mNeedToRunFrameRequestCallbacks(false),
      mNeedToUpdateAnimations(false),
      mMightNeedMediaQueryListenerUpdate(false),
      mNeedToUpdateContentRelevancy(false),
      mInNormalTick(false),
      mAttemptedExtraTickSinceLastVsync(false),
      mHasExceededAfterLoadTickPeriod(false),
      mHasStartedTimerAtLeastOnce(false) {
  MOZ_ASSERT(NS_IsMainThread());
  MOZ_ASSERT(mPresContext,
             "Need a pres context to tell us to call Disconnect() later "
             "and decrement sRefreshDriverCount.");
  mMostRecentRefresh = TimeStamp::Now();
  mNextThrottledFrameRequestTick = mMostRecentRefresh;
  mNextRecomputeVisibilityTick = mMostRecentRefresh;

  if (!sRegularRateTimerList) {
    sRegularRateTimerList = new nsTArray<RefreshDriverTimer*>();
  }
  ++sRefreshDriverCount;
}

nsRefreshDriver::~nsRefreshDriver() {
  MOZ_ASSERT(NS_IsMainThread());
  MOZ_ASSERT(ObserverCount() == mEarlyRunners.Length(),
             "observers, except pending selection scrolls, "
             "should have been unregistered");
  MOZ_ASSERT(!mActiveTimer, "timer should be gone");
  MOZ_ASSERT(!mPresContext,
             "Should have called Disconnect() and decremented "
             "sRefreshDriverCount!");

  if (mRootRefresh) {
    mRootRefresh->RemoveRefreshObserver(this, FlushType::Style);
    mRootRefresh = nullptr;
  }
  if (mOwnTimer && sRegularRateTimerList) {
    sRegularRateTimerList->RemoveElement(mOwnTimer.get());
  }
}

// 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) {
    mMostRecentRefresh = TimeStamp::Now();

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

  mMostRecentRefresh += TimeDuration::FromMilliseconds((double)aMilliseconds);

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

void nsRefreshDriver::RestoreNormalRefresh() {
  mTestControllingRefreshes = false;
  EnsureTimerStarted(eAllowTimeToGoBackwards);
  mPendingTransactions.Clear();
}

TimeStamp nsRefreshDriver::MostRecentRefresh(bool aEnsureTimerStarted) const {
  // In case of stylo traversal, we have already activated the refresh driver in
  // RestyleManager::ProcessPendingRestyles().
  if (aEnsureTimerStarted && !ServoStyleSet::IsInServoTraversal()) {
    const_cast<nsRefreshDriver*>(this)->EnsureTimerStarted();
  }

  return mMostRecentRefresh;
}

void nsRefreshDriver::AddRefreshObserver(nsARefreshObserver* aObserver,
                                         FlushType aFlushType,
                                         const char* aObserverDescription) {
  ObserverArray& array = ArrayFor(aFlushType);
  MOZ_ASSERT(!array.Contains(aObserver),
             "We don't want to redundantly register the same observer");
  array.AppendElement(
      ObserverData{aObserver, aObserverDescription, TimeStamp::Now(),
                   MarkerInnerWindowIdFromDocShell(GetDocShell(mPresContext)),
                   profiler_capture_backtrace(), aFlushType});
#ifdef DEBUG
  MOZ_ASSERT(aObserver->mRegistrationCount >= 0,
             "Registration count shouldn't be able to go negative");
  aObserver->mRegistrationCount++;
#endif
  EnsureTimerStarted();
}

bool nsRefreshDriver::RemoveRefreshObserver(nsARefreshObserver* aObserver,
                                            FlushType aFlushType) {
  ObserverArray& array = ArrayFor(aFlushType);
  auto index = array.IndexOf(aObserver);
  if (index == ObserverArray::array_type::NoIndex) {
    return false;
  }

  if (profiler_thread_is_being_profiled_for_markers()) {
    auto& data = array.ElementAt(index);
    nsPrintfCString str("%s [%s]", data.mDescription,
                        kFlushTypeNames[aFlushType]);
    PROFILER_MARKER_TEXT(
        "RefreshObserver", GRAPHICS,
        MarkerOptions(MarkerStack::TakeBacktrace(std::move(data.mCause)),
                      MarkerTiming::IntervalUntilNowFrom(data.mRegisterTime),
                      std::move(data.mInnerWindowId)),
        str);
  }

  array.RemoveElementAt(index);
#ifdef DEBUG
  aObserver->mRegistrationCount--;
  MOZ_ASSERT(aObserver->mRegistrationCount >= 0,
             "Registration count shouldn't be able to go negative");
#endif
  return true;
}

void nsRefreshDriver::PostVisualViewportResizeEvent(
    VVPResizeEvent* aResizeEvent) {
  mVisualViewportResizeEvents.AppendElement(aResizeEvent);
  EnsureTimerStarted();
}

void nsRefreshDriver::DispatchVisualViewportResizeEvents() {
  // We're taking a hint from scroll events and only dispatch the current set
  // of queued resize events. If additional events are posted in response to
  // the current events being dispatched, we'll dispatch them on the next tick.
  VisualViewportResizeEventArray events =
      std::move(mVisualViewportResizeEvents);
  for (auto& event : events) {
    event->Run();
  }
}

void nsRefreshDriver::PostScrollEvent(mozilla::Runnable* aScrollEvent,
                                      bool aDelayed) {
  if (aDelayed) {
    mDelayedScrollEvents.AppendElement(aScrollEvent);
  } else {
    mScrollEvents.AppendElement(aScrollEvent);
    EnsureTimerStarted();
  }
}

void nsRefreshDriver::PostScrollEndEvent(mozilla::Runnable* aScrollEndEvent,
                                         bool aDelayed) {
  if (aDelayed) {
    mDelayedScrollEndEvents.AppendElement(aScrollEndEvent);
  } else {
    mScrollEndEvents.AppendElement(aScrollEndEvent);
    EnsureTimerStarted();
  }
}

void nsRefreshDriver::DispatchScrollEvents() {
  // Scroll events are one-shot, so after running them we can drop them.
  // However, dispatching a scroll event can potentially cause more scroll
  // events to be posted, so we move the initial set into a temporary array
  // first. (Newly posted scroll events will be dispatched on the next tick.)
  ScrollEventArray events = std::move(mScrollEvents);
  for (auto& event : events) {
    event->Run();
  }
}

void nsRefreshDriver::DispatchScrollEndEvents() {
  ScrollEventArray events = std::move(mScrollEndEvents);
  for (auto& event : events) {
    event->Run();
  }
}

void nsRefreshDriver::PostVisualViewportScrollEvent(
    VVPScrollEvent* aScrollEvent) {
  mVisualViewportScrollEvents.AppendElement(aScrollEvent);
  EnsureTimerStarted();
}

void nsRefreshDriver::DispatchVisualViewportScrollEvents() {
  // Scroll events are one-shot, so after running them we can drop them.
  // However, dispatching a scroll event can potentially cause more scroll
  // events to be posted, so we move the initial set into a temporary array
  // first. (Newly posted scroll events will be dispatched on the next tick.)
  VisualViewportScrollEventArray events =
      std::move(mVisualViewportScrollEvents);
  for (auto& event : events) {
    event->Run();
  }
}

// https://drafts.csswg.org/cssom-view/#evaluate-media-queries-and-report-changes
void nsRefreshDriver::EvaluateMediaQueriesAndReportChanges() {
  if (!mMightNeedMediaQueryListenerUpdate) {
    return;
  }
  mMightNeedMediaQueryListenerUpdate = false;
  if (!mPresContext) {
    return;
  }
  AUTO_PROFILER_LABEL_RELEVANT_FOR_JS(
      "Evaluate media queries and report changes", LAYOUT);
  RefPtr<Document> doc = mPresContext->Document();
  doc->EvaluateMediaQueriesAndReportChanges(/* aRecurse = */ true);
}

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

void nsRefreshDriver::RemovePostRefreshObserver(
    nsAPostRefreshObserver* aObserver) {
  bool removed = mPostRefreshObservers.RemoveElement(aObserver);
  MOZ_DIAGNOSTIC_ASSERT(removed);
  Unused << removed;
}

void nsRefreshDriver::AddImageRequest(imgIRequest* aRequest) {
  uint32_t delay = GetFirstFrameDelay(aRequest);
  if (delay == 0) {
    mRequests.Insert(aRequest);
  } else {
    auto* const start = mStartTable.GetOrInsertNew(delay);
    start->mEntries.Insert(aRequest);
  }

  EnsureTimerStarted();

  if (profiler_thread_is_being_profiled_for_markers()) {
    nsCOMPtr<nsIURI> uri = aRequest->GetURI();

    PROFILER_MARKER_TEXT("Image Animation", GRAPHICS,
                         MarkerOptions(MarkerTiming::IntervalStart(),
                                       MarkerInnerWindowIdFromDocShell(
                                           GetDocShell(mPresContext))),
                         nsContentUtils::TruncatedURLForDisplay(uri));
  }
}

void nsRefreshDriver::RemoveImageRequest(imgIRequest* aRequest) {
  // Try to remove from both places, just in case.
  bool removed = mRequests.EnsureRemoved(aRequest);
  uint32_t delay = GetFirstFrameDelay(aRequest);
  if (delay != 0) {
    ImageStartData* start = mStartTable.Get(delay);
    if (start) {
      removed = removed | start->mEntries.EnsureRemoved(aRequest);
    }
  }

  if (removed && profiler_thread_is_being_profiled_for_markers()) {
    nsCOMPtr<nsIURI> uri = aRequest->GetURI();

    PROFILER_MARKER_TEXT("Image Animation", GRAPHICS,
                         MarkerOptions(MarkerTiming::IntervalEnd(),
                                       MarkerInnerWindowIdFromDocShell(
                                           GetDocShell(mPresContext))),
                         nsContentUtils::TruncatedURLForDisplay(uri));
  }
}

void nsRefreshDriver::RegisterCompositionPayload(
    const mozilla::layers::CompositionPayload& aPayload) {
  mCompositionPayloads.AppendElement(aPayload);
}

void nsRefreshDriver::AddForceNotifyContentfulPaintPresContext(
    nsPresContext* aPresContext) {
  mForceNotifyContentfulPaintPresContexts.AppendElement(aPresContext);
}

void nsRefreshDriver::FlushForceNotifyContentfulPaintPresContext() {
  while (!mForceNotifyContentfulPaintPresContexts.IsEmpty()) {
    WeakPtr<nsPresContext> presContext =
        mForceNotifyContentfulPaintPresContexts.PopLastElement();
    if (presContext) {
      presContext->NotifyContentfulPaint();
    }
  }
}

void nsRefreshDriver::RunDelayedEventsSoon() {
  // Place entries for delayed events into their corresponding normal list,
  // and schedule a refresh. When these delayed events run, if their document
  // still has events suppressed then they will be readded to the delayed
  // events list.

  mScrollEvents.AppendElements(mDelayedScrollEvents);
  mDelayedScrollEvents.Clear();

  mScrollEndEvents.AppendElements(mDelayedScrollEvents);
  mDelayedScrollEndEvents.Clear();

  mResizeEventFlushObservers.AppendElements(mDelayedResizeEventFlushObservers);
  mDelayedResizeEventFlushObservers.Clear();

  EnsureTimerStarted();
}

bool nsRefreshDriver::CanDoCatchUpTick() {
  if (mTestControllingRefreshes || !mActiveTimer) {
    return false;
  }

  // If we've already ticked for the current timer refresh (or more recently
  // than that), then we don't need to do any catching up.
  if (mMostRecentRefresh >= mActiveTimer->MostRecentRefresh()) {
    return false;
  }

  if (mActiveTimer->IsBlocked()) {
    return false;
  }

  if (mTickVsyncTime.IsNull()) {
    // Don't try to run a catch-up tick before there has been at least one
    // normal tick. The catch-up tick could negatively affect page load
    // performance.
    return false;
  }

  if (mPresContext && mPresContext->Document()->GetReadyStateEnum() <
                          Document::READYSTATE_COMPLETE) {
    // Don't try to run a catch-up tick before the page has finished loading.
    // The catch-up tick could negatively affect page load performance.
    return false;
  }

  return true;
}

bool nsRefreshDriver::CanDoExtraTick() {
  // Only allow one extra tick per normal vsync tick.
  if (mAttemptedExtraTickSinceLastVsync) {
    return false;
  }

  // If we don't have a timer, or we didn't tick on the timer's
  // refresh then we can't do an 'extra' tick (but we may still
  // do a catch up tick).
  if (!mActiveTimer ||
      mActiveTimer->MostRecentRefresh() != mMostRecentRefresh) {
    return false;
  }

  // Grab the current timestamp before checking the tick hint to be sure
  // sure that it's equal or smaller than the value used within checking
  // the tick hint.
  TimeStamp now = TimeStamp::Now();
  Maybe<TimeStamp> nextTick = mActiveTimer->GetNextTickHint();
  int32_t minimumRequiredTime = StaticPrefs::layout_extra_tick_minimum_ms();
  // If there's less than 4 milliseconds until the next tick, it's probably
  // not worth trying to catch up.
  if (minimumRequiredTime < 0 || !nextTick ||
      (*nextTick - now) < TimeDuration::FromMilliseconds(minimumRequiredTime)) {
    return false;
  }

  return true;
}

void nsRefreshDriver::EnsureTimerStarted(EnsureTimerStartedFlags aFlags) {
  // FIXME: Bug 1346065: We should also assert the case where we have no
  // stylo-threads.
  MOZ_ASSERT(!ServoStyleSet::IsInServoTraversal() || NS_IsMainThread(),
             "EnsureTimerStarted should be called only when we are not "
             "in servo traversal or on the main-thread");

  if (mTestControllingRefreshes) {
    return;
  }

  if (!mRefreshTimerStartedCause) {
    mRefreshTimerStartedCause = profiler_capture_backtrace();
  }

  // will it already fire, and no other changes needed?
  if (mActiveTimer && !(aFlags & eForceAdjustTimer)) {
    // If we're being called from within a user input handler, and we think
    // there's time to rush an extra tick immediately, then schedule a runnable
    // to run the extra tick.
    if (mUserInputProcessingCount && CanDoExtraTick()) {
      RefPtr<nsRefreshDriver> self = this;
      NS_DispatchToCurrentThreadQueue(
          NS_NewRunnableFunction(
              "RefreshDriver::EnsureTimerStarted::extra",
              [self]() -> void {
                // Re-check if we can still do an extra tick, in case anything
                // changed while the runnable was pending.
                if (self->CanDoExtraTick()) {
                  PROFILER_MARKER_UNTYPED("ExtraRefreshDriverTick", GRAPHICS);
                  LOG("[%p] Doing extra tick for user input", self.get());
                  self->mAttemptedExtraTickSinceLastVsync = true;
                  self->Tick(self->mActiveTimer->MostRecentRefreshVsyncId(),
                             self->mActiveTimer->MostRecentRefresh(),
                             IsExtraTick::Yes);
                }
              }),
          EventQueuePriority::Vsync);
    }
    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).
    if (!mPresContext->Document()->IsSVGGlyphsDocument()) {
      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);

    if (!mHasStartedTimerAtLeastOnce) {
      mHasStartedTimerAtLeastOnce = true;
      if (profiler_thread_is_being_profiled_for_markers()) {
        nsCString text = "initial timer start "_ns;
        if (mPresContext->Document()->GetDocumentURI()) {
          text.Append(nsContentUtils::TruncatedURLForDisplay(
              mPresContext->Document()->GetDocumentURI()));
        }

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