dom/html/TextTrackManager.cpp
author Alastor Wu <alwu@mozilla.com>
Tue, 05 Mar 2019 19:48:31 +0000
changeset 520967 a0d8bc1dab63
parent 520965 ad7bfe5bbc3a
child 521668 440f5cace4fb
permissions -rw-r--r--
Bug 1509446 - part6 : update cues display without checking whether cue is active or not. r=jya We should update cue display everytime when the cues list changed. In addition, we shouldn't check whether cue is active when we update display, because it's always inactive when the cue has been removed from `TextTrack::RemoveCue()`. Differential Revision: https://phabricator.services.mozilla.com/D21143

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "mozilla/dom/TextTrackManager.h"
#include "mozilla/ClearOnShutdown.h"
#include "mozilla/CycleCollectedJSContext.h"
#include "mozilla/Telemetry.h"
#include "mozilla/dom/Event.h"
#include "mozilla/dom/HTMLMediaElement.h"
#include "mozilla/dom/HTMLTrackElement.h"
#include "mozilla/dom/HTMLVideoElement.h"
#include "mozilla/dom/TextTrack.h"
#include "mozilla/dom/TextTrackCue.h"
#include "nsComponentManagerUtils.h"
#include "nsGlobalWindow.h"
#include "nsIFrame.h"
#include "nsIWebVTTParserWrapper.h"
#include "nsVariant.h"
#include "nsVideoFrame.h"

static mozilla::LazyLogModule gTextTrackLog("TextTrackManager");
#define WEBVTT_LOG(...) MOZ_LOG(gTextTrackLog, LogLevel::Debug, (__VA_ARGS__))
#define WEBVTT_LOGV(...) \
  MOZ_LOG(gTextTrackLog, LogLevel::Verbose, (__VA_ARGS__))

namespace mozilla {
namespace dom {

NS_IMPL_ISUPPORTS(TextTrackManager::ShutdownObserverProxy, nsIObserver);

void TextTrackManager::ShutdownObserverProxy::Unregister() {
  nsContentUtils::UnregisterShutdownObserver(this);
  mManager = nullptr;
}

CompareTextTracks::CompareTextTracks(HTMLMediaElement* aMediaElement) {
  mMediaElement = aMediaElement;
}

int32_t CompareTextTracks::TrackChildPosition(TextTrack* aTextTrack) const {
  MOZ_DIAGNOSTIC_ASSERT(aTextTrack);
  HTMLTrackElement* trackElement = aTextTrack->GetTrackElement();
  if (!trackElement) {
    return -1;
  }
  return mMediaElement->ComputeIndexOf(trackElement);
}

bool CompareTextTracks::Equals(TextTrack* aOne, TextTrack* aTwo) const {
  // Two tracks can never be equal. If they have corresponding TrackElements
  // they would need to occupy the same tree position (impossible) and in the
  // case of tracks coming from AddTextTrack source we put the newest at the
  // last position, so they won't be equal as well.
  return false;
}

bool CompareTextTracks::LessThan(TextTrack* aOne, TextTrack* aTwo) const {
  // Protect against nullptr TextTrack objects; treat them as
  // sorting toward the end.
  if (!aOne) {
    return false;
  }
  if (!aTwo) {
    return true;
  }
  TextTrackSource sourceOne = aOne->GetTextTrackSource();
  TextTrackSource sourceTwo = aTwo->GetTextTrackSource();
  if (sourceOne != sourceTwo) {
    return sourceOne == TextTrackSource::Track ||
           (sourceOne == AddTextTrack && sourceTwo == MediaResourceSpecific);
  }
  switch (sourceOne) {
    case Track: {
      int32_t positionOne = TrackChildPosition(aOne);
      int32_t positionTwo = TrackChildPosition(aTwo);
      // If either position one or positiontwo are -1 then something has gone
      // wrong. In this case we should just put them at the back of the list.
      return positionOne != -1 && positionTwo != -1 &&
             positionOne < positionTwo;
    }
    case AddTextTrack:
      // For AddTextTrack sources the tracks will already be in the correct
      // relative order in the source array. Assume we're called in iteration
      // order and can therefore always report aOne < aTwo to maintain the
      // original temporal ordering.
      return true;
    case MediaResourceSpecific:
      // No rules for Media Resource Specific tracks yet.
      break;
  }
  return true;
}

NS_IMPL_CYCLE_COLLECTION(TextTrackManager, mMediaElement, mTextTracks,
                         mPendingTextTracks, mNewCues, mLastActiveCues)

NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(TextTrackManager)
  NS_INTERFACE_MAP_ENTRY(nsIDOMEventListener)
NS_INTERFACE_MAP_END

NS_IMPL_CYCLE_COLLECTING_ADDREF(TextTrackManager)
NS_IMPL_CYCLE_COLLECTING_RELEASE(TextTrackManager)

StaticRefPtr<nsIWebVTTParserWrapper> TextTrackManager::sParserWrapper;

TextTrackManager::TextTrackManager(HTMLMediaElement* aMediaElement)
    : mMediaElement(aMediaElement),
      mHasSeeked(false),
      mLastTimeMarchesOnCalled(0.0),
      mTimeMarchesOnDispatched(false),
      mUpdateCueDisplayDispatched(false),
      performedTrackSelection(false),
      mCueTelemetryReported(false),
      mShutdown(false) {
  nsISupports* parentObject = mMediaElement->OwnerDoc()->GetParentObject();

  NS_ENSURE_TRUE_VOID(parentObject);
  WEBVTT_LOG("%p Create TextTrackManager", this);
  nsCOMPtr<nsPIDOMWindowInner> window = do_QueryInterface(parentObject);
  mNewCues = new TextTrackCueList(window);
  mLastActiveCues = new TextTrackCueList(window);
  mTextTracks = new TextTrackList(window, this);
  mPendingTextTracks = new TextTrackList(window, this);

  if (!sParserWrapper) {
    nsCOMPtr<nsIWebVTTParserWrapper> parserWrapper =
        do_CreateInstance(NS_WEBVTTPARSERWRAPPER_CONTRACTID);
    MOZ_ASSERT(parserWrapper, "Can't create nsIWebVTTParserWrapper");
    sParserWrapper = parserWrapper;
    ClearOnShutdown(&sParserWrapper);
  }
  mShutdownProxy = new ShutdownObserverProxy(this);
}

TextTrackManager::~TextTrackManager() {
  WEBVTT_LOG("%p ~TextTrackManager", this);
  mShutdownProxy->Unregister();
}

TextTrackList* TextTrackManager::GetTextTracks() const { return mTextTracks; }

already_AddRefed<TextTrack> TextTrackManager::AddTextTrack(
    TextTrackKind aKind, const nsAString& aLabel, const nsAString& aLanguage,
    TextTrackMode aMode, TextTrackReadyState aReadyState,
    TextTrackSource aTextTrackSource) {
  if (!mMediaElement || !mTextTracks) {
    return nullptr;
  }
  WEBVTT_LOG("%p AddTextTrack", this);
  WEBVTT_LOGV("AddTextTrack kind %" PRIu32 " Label %s Language %s",
              static_cast<uint32_t>(aKind), NS_ConvertUTF16toUTF8(aLabel).get(),
              NS_ConvertUTF16toUTF8(aLanguage).get());
  RefPtr<TextTrack> track = mTextTracks->AddTextTrack(
      aKind, aLabel, aLanguage, aMode, aReadyState, aTextTrackSource,
      CompareTextTracks(mMediaElement));
  AddCues(track);
  ReportTelemetryForTrack(track);

  if (aTextTrackSource == TextTrackSource::Track) {
    RefPtr<nsIRunnable> task = NewRunnableMethod(
        "dom::TextTrackManager::HonorUserPreferencesForTrackSelection", this,
        &TextTrackManager::HonorUserPreferencesForTrackSelection);
    nsContentUtils::RunInStableState(task.forget());
  }

  return track.forget();
}

void TextTrackManager::AddTextTrack(TextTrack* aTextTrack) {
  if (!mMediaElement || !mTextTracks) {
    return;
  }
  WEBVTT_LOG("%p AddTextTrack TextTrack %p", this, aTextTrack);
  mTextTracks->AddTextTrack(aTextTrack, CompareTextTracks(mMediaElement));
  AddCues(aTextTrack);
  ReportTelemetryForTrack(aTextTrack);

  if (aTextTrack->GetTextTrackSource() == TextTrackSource::Track) {
    RefPtr<nsIRunnable> task = NewRunnableMethod(
        "dom::TextTrackManager::HonorUserPreferencesForTrackSelection", this,
        &TextTrackManager::HonorUserPreferencesForTrackSelection);
    nsContentUtils::RunInStableState(task.forget());
  }
}

void TextTrackManager::AddCues(TextTrack* aTextTrack) {
  if (!mNewCues) {
    WEBVTT_LOG("AddCues mNewCues is null");
    return;
  }

  TextTrackCueList* cueList = aTextTrack->GetCues();
  if (cueList) {
    bool dummy;
    WEBVTT_LOGV("AddCues cueList->Length() %d", cueList->Length());
    for (uint32_t i = 0; i < cueList->Length(); ++i) {
      mNewCues->AddCue(*cueList->IndexedGetter(i, dummy));
    }
    TimeMarchesOn();
  }
}

void TextTrackManager::RemoveTextTrack(TextTrack* aTextTrack,
                                       bool aPendingListOnly) {
  if (!mPendingTextTracks || !mTextTracks) {
    return;
  }

  WEBVTT_LOG("%p RemoveTextTrack TextTrack %p", this, aTextTrack);
  mPendingTextTracks->RemoveTextTrack(aTextTrack);
  if (aPendingListOnly) {
    return;
  }

  mTextTracks->RemoveTextTrack(aTextTrack);
  // Remove the cues in mNewCues belong to aTextTrack.
  TextTrackCueList* removeCueList = aTextTrack->GetCues();
  if (removeCueList) {
    WEBVTT_LOGV("RemoveTextTrack removeCueList->Length() %d",
                removeCueList->Length());
    for (uint32_t i = 0; i < removeCueList->Length(); ++i) {
      mNewCues->RemoveCue(*((*removeCueList)[i]));
    }
    TimeMarchesOn();
  }
}

void TextTrackManager::DidSeek() {
  WEBVTT_LOG("%p DidSeek", this);
  if (mMediaElement) {
    mLastTimeMarchesOnCalled = mMediaElement->CurrentTime();
    WEBVTT_LOGV("DidSeek set mLastTimeMarchesOnCalled %lf",
                mLastTimeMarchesOnCalled);
  }
  mHasSeeked = true;
}

void TextTrackManager::UpdateCueDisplay() {
  WEBVTT_LOG("UpdateCueDisplay");
  mUpdateCueDisplayDispatched = false;

  if (!mMediaElement || !mTextTracks || IsShutdown()) {
    return;
  }

  nsIFrame* frame = mMediaElement->GetPrimaryFrame();
  nsVideoFrame* videoFrame = do_QueryFrame(frame);
  if (!videoFrame) {
    return;
  }

  nsCOMPtr<nsIContent> overlay = videoFrame->GetCaptionOverlay();
  nsCOMPtr<nsIContent> controls = videoFrame->GetVideoControls();
  if (!overlay) {
    return;
  }

  nsTArray<RefPtr<TextTrackCue>> showingCues;
  mTextTracks->GetShowingCues(showingCues);

  if (showingCues.Length() > 0) {
    WEBVTT_LOG("UpdateCueDisplay ProcessCues");
    WEBVTT_LOGV("UpdateCueDisplay showingCues.Length() %zu",
                showingCues.Length());
    RefPtr<nsVariantCC> jsCues = new nsVariantCC();

    jsCues->SetAsArray(nsIDataType::VTYPE_INTERFACE, &NS_GET_IID(EventTarget),
                       showingCues.Length(),
                       static_cast<void*>(showingCues.Elements()));
    nsPIDOMWindowInner* window = mMediaElement->OwnerDoc()->GetInnerWindow();
    if (window) {
      sParserWrapper->ProcessCues(window, jsCues, overlay, controls);
    }
  } else if (overlay->Length() > 0) {
    WEBVTT_LOG("UpdateCueDisplay EmptyString");
    nsContentUtils::SetNodeTextContent(overlay, EmptyString(), true);
  }
}

void TextTrackManager::NotifyCueAdded(TextTrackCue& aCue) {
  WEBVTT_LOG("NotifyCueAdded");
  if (mNewCues) {
    mNewCues->AddCue(aCue);
  }
  TimeMarchesOn();
  ReportTelemetryForCue();
}

void TextTrackManager::NotifyCueRemoved(TextTrackCue& aCue) {
  WEBVTT_LOG("NotifyCueRemoved");
  if (mNewCues) {
    mNewCues->RemoveCue(aCue);
  }
  TimeMarchesOn();
  DispatchUpdateCueDisplay();
}

void TextTrackManager::PopulatePendingList() {
  if (!mTextTracks || !mPendingTextTracks || !mMediaElement) {
    return;
  }
  uint32_t len = mTextTracks->Length();
  bool dummy;
  for (uint32_t index = 0; index < len; ++index) {
    TextTrack* ttrack = mTextTracks->IndexedGetter(index, dummy);
    if (ttrack && ttrack->Mode() != TextTrackMode::Disabled &&
        ttrack->ReadyState() == TextTrackReadyState::Loading) {
      mPendingTextTracks->AddTextTrack(ttrack,
                                       CompareTextTracks(mMediaElement));
    }
  }
}

void TextTrackManager::AddListeners() {
  if (mMediaElement) {
    mMediaElement->AddEventListener(NS_LITERAL_STRING("resizevideocontrols"),
                                    this, false, false);
    mMediaElement->AddEventListener(NS_LITERAL_STRING("seeked"), this, false,
                                    false);
    mMediaElement->AddEventListener(NS_LITERAL_STRING("controlbarchange"), this,
                                    false, true);
  }
}

void TextTrackManager::HonorUserPreferencesForTrackSelection() {
  if (performedTrackSelection || !mTextTracks) {
    return;
  }
  WEBVTT_LOG("HonorUserPreferencesForTrackSelection");
  TextTrackKind ttKinds[] = {TextTrackKind::Captions, TextTrackKind::Subtitles};

  // Steps 1 - 3: Perform automatic track selection for different TextTrack
  // Kinds.
  PerformTrackSelection(ttKinds, ArrayLength(ttKinds));
  PerformTrackSelection(TextTrackKind::Descriptions);
  PerformTrackSelection(TextTrackKind::Chapters);

  // Step 4: Set all TextTracks with a kind of metadata that are disabled
  // to hidden.
  for (uint32_t i = 0; i < mTextTracks->Length(); i++) {
    TextTrack* track = (*mTextTracks)[i];
    if (track->Kind() == TextTrackKind::Metadata && TrackIsDefault(track) &&
        track->Mode() == TextTrackMode::Disabled) {
      track->SetMode(TextTrackMode::Hidden);
    }
  }

  performedTrackSelection = true;
}

bool TextTrackManager::TrackIsDefault(TextTrack* aTextTrack) {
  HTMLTrackElement* trackElement = aTextTrack->GetTrackElement();
  if (!trackElement) {
    return false;
  }
  return trackElement->Default();
}

void TextTrackManager::PerformTrackSelection(TextTrackKind aTextTrackKind) {
  TextTrackKind ttKinds[] = {aTextTrackKind};
  PerformTrackSelection(ttKinds, ArrayLength(ttKinds));
}

void TextTrackManager::PerformTrackSelection(TextTrackKind aTextTrackKinds[],
                                             uint32_t size) {
  nsTArray<TextTrack*> candidates;
  GetTextTracksOfKinds(aTextTrackKinds, size, candidates);

  // Step 3: If any TextTracks in candidates are showing then abort these steps.
  for (uint32_t i = 0; i < candidates.Length(); i++) {
    if (candidates[i]->Mode() == TextTrackMode::Showing) {
      WEBVTT_LOGV("PerformTrackSelection Showing return kind %d",
                  static_cast<int>(candidates[i]->Kind()));
      return;
    }
  }

  // Step 4: Honor user preferences for track selection, otherwise, set the
  // first TextTrack in candidates with a default attribute to showing.
  // TODO: Bug 981691 - Honor user preferences for text track selection.
  for (uint32_t i = 0; i < candidates.Length(); i++) {
    if (TrackIsDefault(candidates[i]) &&
        candidates[i]->Mode() == TextTrackMode::Disabled) {
      candidates[i]->SetMode(TextTrackMode::Showing);
      WEBVTT_LOGV("PerformTrackSelection set Showing kind %d",
                  static_cast<int>(candidates[i]->Kind()));
      return;
    }
  }
}

void TextTrackManager::GetTextTracksOfKinds(TextTrackKind aTextTrackKinds[],
                                            uint32_t size,
                                            nsTArray<TextTrack*>& aTextTracks) {
  for (uint32_t i = 0; i < size; i++) {
    GetTextTracksOfKind(aTextTrackKinds[i], aTextTracks);
  }
}

void TextTrackManager::GetTextTracksOfKind(TextTrackKind aTextTrackKind,
                                           nsTArray<TextTrack*>& aTextTracks) {
  if (!mTextTracks) {
    return;
  }
  for (uint32_t i = 0; i < mTextTracks->Length(); i++) {
    TextTrack* textTrack = (*mTextTracks)[i];
    if (textTrack->Kind() == aTextTrackKind) {
      aTextTracks.AppendElement(textTrack);
    }
  }
}

NS_IMETHODIMP
TextTrackManager::HandleEvent(Event* aEvent) {
  if (!mTextTracks) {
    return NS_OK;
  }

  nsAutoString type;
  aEvent->GetType(type);
  if (type.EqualsLiteral("resizevideocontrols") ||
      type.EqualsLiteral("seeked")) {
    for (uint32_t i = 0; i < mTextTracks->Length(); i++) {
      ((*mTextTracks)[i])->SetCuesDirty();
    }
  }

  if (type.EqualsLiteral("controlbarchange")) {
    UpdateCueDisplay();
  }

  return NS_OK;
}

class SimpleTextTrackEvent : public Runnable {
 public:
  friend class CompareSimpleTextTrackEvents;
  SimpleTextTrackEvent(const nsAString& aEventName, double aTime,
                       TextTrack* aTrack, TextTrackCue* aCue)
      : Runnable("dom::SimpleTextTrackEvent"),
        mName(aEventName),
        mTime(aTime),
        mTrack(aTrack),
        mCue(aCue) {}

  NS_IMETHOD Run() override {
    WEBVTT_LOGV("SimpleTextTrackEvent cue %p mName %s mTime %lf", mCue.get(),
                NS_ConvertUTF16toUTF8(mName).get(), mTime);
    mCue->DispatchTrustedEvent(mName);
    return NS_OK;
  }

  void Dispatch() {
    if (nsCOMPtr<nsIGlobalObject> global = mCue->GetOwnerGlobal()) {
      global->Dispatch(TaskCategory::Other, do_AddRef(this));
    } else {
      NS_DispatchToMainThread(do_AddRef(this));
    }
  }

 private:
  nsString mName;
  double mTime;
  TextTrack* mTrack;
  RefPtr<TextTrackCue> mCue;
};

class CompareSimpleTextTrackEvents {
 private:
  int32_t TrackChildPosition(SimpleTextTrackEvent* aEvent) const {
    if (aEvent->mTrack) {
      HTMLTrackElement* trackElement = aEvent->mTrack->GetTrackElement();
      if (trackElement) {
        return mMediaElement->ComputeIndexOf(trackElement);
      }
    }
    return -1;
  }
  HTMLMediaElement* mMediaElement;

 public:
  explicit CompareSimpleTextTrackEvents(HTMLMediaElement* aMediaElement) {
    mMediaElement = aMediaElement;
  }

  bool Equals(SimpleTextTrackEvent* aOne, SimpleTextTrackEvent* aTwo) const {
    return false;
  }

  bool LessThan(SimpleTextTrackEvent* aOne, SimpleTextTrackEvent* aTwo) const {
    // TimeMarchesOn step 13.1.
    if (aOne->mTime < aTwo->mTime) {
      return true;
    } else if (aOne->mTime > aTwo->mTime) {
      return false;
    }

    // TimeMarchesOn step 13.2 text track cue order.
    // TextTrack position in TextTrackList
    TextTrack* t1 = aOne->mTrack;
    TextTrack* t2 = aTwo->mTrack;
    MOZ_ASSERT(t1, "CompareSimpleTextTrackEvents t1 is null");
    MOZ_ASSERT(t2, "CompareSimpleTextTrackEvents t2 is null");
    if (t1 != t2) {
      TextTrackList* tList = t1->GetTextTrackList();
      MOZ_ASSERT(tList, "CompareSimpleTextTrackEvents tList is null");
      nsTArray<RefPtr<TextTrack>>& textTracks = tList->GetTextTrackArray();
      auto index1 = textTracks.IndexOf(t1);
      auto index2 = textTracks.IndexOf(t2);
      if (index1 < index2) {
        return true;
      } else if (index1 > index2) {
        return false;
      }
    }

    MOZ_ASSERT(t1 == t2, "CompareSimpleTextTrackEvents t1 != t2");
    // c1 and c2 are both belongs to t1.
    TextTrackCue* c1 = aOne->mCue;
    TextTrackCue* c2 = aTwo->mCue;
    if (c1 != c2) {
      if (c1->StartTime() < c2->StartTime()) {
        return true;
      } else if (c1->StartTime() > c2->StartTime()) {
        return false;
      }
      if (c1->EndTime() < c2->EndTime()) {
        return true;
      } else if (c1->EndTime() > c2->EndTime()) {
        return false;
      }

      TextTrackCueList* cueList = t1->GetCues();
      nsTArray<RefPtr<TextTrackCue>>& cues = cueList->GetCuesArray();
      auto index1 = cues.IndexOf(c1);
      auto index2 = cues.IndexOf(c2);
      if (index1 < index2) {
        return true;
      } else if (index1 > index2) {
        return false;
      }
    }

    // TimeMarchesOn step 13.3.
    if (aOne->mName.EqualsLiteral("enter") ||
        aTwo->mName.EqualsLiteral("exit")) {
      return true;
    }
    return false;
  }
};

class TextTrackListInternal {
 public:
  void AddTextTrack(TextTrack* aTextTrack,
                    const CompareTextTracks& aCompareTT) {
    if (!mTextTracks.Contains(aTextTrack)) {
      mTextTracks.InsertElementSorted(aTextTrack, aCompareTT);
    }
  }
  uint32_t Length() const { return mTextTracks.Length(); }
  TextTrack* operator[](uint32_t aIndex) {
    return mTextTracks.SafeElementAt(aIndex, nullptr);
  }

 private:
  nsTArray<RefPtr<TextTrack>> mTextTracks;
};

void TextTrackManager::DispatchUpdateCueDisplay() {
  if (!mUpdateCueDisplayDispatched && !IsShutdown() &&
      mMediaElement->IsCurrentlyPlaying()) {
    WEBVTT_LOG("DispatchUpdateCueDisplay");
    nsPIDOMWindowInner* win = mMediaElement->OwnerDoc()->GetInnerWindow();
    if (win) {
      nsGlobalWindowInner::Cast(win)->Dispatch(
          TaskCategory::Other,
          NewRunnableMethod("dom::TextTrackManager::UpdateCueDisplay", this,
                            &TextTrackManager::UpdateCueDisplay));
      mUpdateCueDisplayDispatched = true;
    }
  }
}

void TextTrackManager::DispatchTimeMarchesOn() {
  // Run the algorithm if no previous instance is still running, otherwise
  // enqueue the current playback position and whether only that changed
  // through its usual monotonic increase during normal playback; current
  // executing call upon completion will check queue for further 'work'.
  if (!mTimeMarchesOnDispatched && !IsShutdown() &&
      mMediaElement->IsCurrentlyPlaying()) {
    WEBVTT_LOG("DispatchTimeMarchesOn");
    nsPIDOMWindowInner* win = mMediaElement->OwnerDoc()->GetInnerWindow();
    if (win) {
      nsGlobalWindowInner::Cast(win)->Dispatch(
          TaskCategory::Other,
          NewRunnableMethod("dom::TextTrackManager::TimeMarchesOn", this,
                            &TextTrackManager::TimeMarchesOn));
      mTimeMarchesOnDispatched = true;
    }
  }
}

// https://html.spec.whatwg.org/multipage/embedded-content.html#time-marches-on
void TextTrackManager::TimeMarchesOn() {
  NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
  mTimeMarchesOnDispatched = false;

  CycleCollectedJSContext* context = CycleCollectedJSContext::Get();
  if (context && context->IsInStableOrMetaStableState()) {
    // FireTimeUpdate can be called while at stable state following a
    // current position change which triggered a state watcher in MediaDecoder
    // (see bug 1443429).
    // TimeMarchesOn() will modify JS attributes which is forbidden while in
    // stable state. So we dispatch a task to perform such operation later
    // instead.
    DispatchTimeMarchesOn();
    return;
  }
  WEBVTT_LOG("TimeMarchesOn");

  // Early return if we don't have any TextTracks or shutting down.
  if (!mTextTracks || mTextTracks->Length() == 0 || IsShutdown()) {
    return;
  }

  nsISupports* parentObject = mMediaElement->OwnerDoc()->GetParentObject();
  if (NS_WARN_IF(!parentObject)) {
    return;
  }
  nsCOMPtr<nsPIDOMWindowInner> window = do_QueryInterface(parentObject);

  if (mMediaElement &&
      (!(mMediaElement->GetPlayedOrSeeked()) || mMediaElement->Seeking())) {
    WEBVTT_LOG("TimeMarchesOn seeking or post return");
    return;
  }

  // Step 3.
  double currentPlaybackTime = mMediaElement->CurrentTime();
  bool hasNormalPlayback = !mHasSeeked;
  mHasSeeked = false;
  WEBVTT_LOG(
      "TimeMarchesOn mLastTimeMarchesOnCalled %lf currentPlaybackTime %lf "
      "hasNormalPlayback %d",
      mLastTimeMarchesOnCalled, currentPlaybackTime, hasNormalPlayback);

  // Step 1, 2.
  RefPtr<TextTrackCueList> currentCues = new TextTrackCueList(window);
  RefPtr<TextTrackCueList> otherCues = new TextTrackCueList(window);
  bool dummy;
  for (uint32_t index = 0; index < mTextTracks->Length(); ++index) {
    TextTrack* ttrack = mTextTracks->IndexedGetter(index, dummy);
    if (ttrack && dummy) {
      // TODO: call GetCueListByTimeInterval on mNewCues?
      ttrack->GetCurrentCueList(currentCues);
    }
  }
  WEBVTT_LOGV("TimeMarchesOn currentCues %d", currentCues->Length());
  // Populate otherCues with 'non-active" cues.
  if (hasNormalPlayback) {
    if (currentPlaybackTime < mLastTimeMarchesOnCalled) {
      // TODO: Add log and find the root cause why the
      // playback position goes backward.
      mLastTimeMarchesOnCalled = currentPlaybackTime;
    }
    media::Interval<double> interval(mLastTimeMarchesOnCalled,
                                     currentPlaybackTime);
    otherCues = mNewCues->GetCueListByTimeInterval(interval);
    ;
  } else {
    // Seek case. Put the mLastActiveCues into otherCues.
    otherCues = mLastActiveCues;
  }
  for (uint32_t i = 0; i < currentCues->Length(); ++i) {
    TextTrackCue* cue = (*currentCues)[i];
    otherCues->RemoveCue(*cue);
  }
  WEBVTT_LOGV("TimeMarchesOn otherCues %d", otherCues->Length());
  // Step 4.
  RefPtr<TextTrackCueList> missedCues = new TextTrackCueList(window);
  if (hasNormalPlayback) {
    for (uint32_t i = 0; i < otherCues->Length(); ++i) {
      TextTrackCue* cue = (*otherCues)[i];
      if (cue->StartTime() >= mLastTimeMarchesOnCalled &&
          cue->EndTime() <= currentPlaybackTime) {
        missedCues->AddCue(*cue);
      }
    }
  }
  WEBVTT_LOGV("TimeMarchesOn missedCues %d", missedCues->Length());
  // Step 5. Empty now.
  // TODO: Step 6: fire timeupdate?

  // Step 7. Abort steps if condition 1, 2, 3 are satisfied.
  // 1. All of the cues in current cues have their active flag set.
  // 2. None of the cues in other cues have their active flag set.
  // 3. Missed cues is empty.
  bool c1 = true;
  for (uint32_t i = 0; i < currentCues->Length(); ++i) {
    if (!(*currentCues)[i]->GetActive()) {
      c1 = false;
      break;
    }
  }
  bool c2 = true;
  for (uint32_t i = 0; i < otherCues->Length(); ++i) {
    if ((*otherCues)[i]->GetActive()) {
      c2 = false;
      break;
    }
  }
  bool c3 = (missedCues->Length() == 0);
  if (c1 && c2 && c3) {
    mLastTimeMarchesOnCalled = currentPlaybackTime;
    WEBVTT_LOG("TimeMarchesOn step 7 return, mLastTimeMarchesOnCalled %lf",
               mLastTimeMarchesOnCalled);
    return;
  }

  // Step 8. Respect PauseOnExit flag if not seek.
  if (hasNormalPlayback) {
    for (uint32_t i = 0; i < otherCues->Length(); ++i) {
      TextTrackCue* cue = (*otherCues)[i];
      if (cue && cue->PauseOnExit() && cue->GetActive()) {
        WEBVTT_LOG("TimeMarchesOn pause the MediaElement");
        mMediaElement->Pause();
        break;
      }
    }
    for (uint32_t i = 0; i < missedCues->Length(); ++i) {
      TextTrackCue* cue = (*missedCues)[i];
      if (cue && cue->PauseOnExit()) {
        WEBVTT_LOG("TimeMarchesOn pause the MediaElement");
        mMediaElement->Pause();
        break;
      }
    }
  }

  // Step 15.
  // Sort text tracks in the same order as the text tracks appear
  // in the media element's list of text tracks, and remove
  // duplicates.
  TextTrackListInternal affectedTracks;
  // Step 13, 14.
  nsTArray<RefPtr<SimpleTextTrackEvent>> eventList;
  // Step 9, 10.
  // For each text track cue in missed cues, prepare an event named
  // enter for the TextTrackCue object with the cue start time.
  for (uint32_t i = 0; i < missedCues->Length(); ++i) {
    TextTrackCue* cue = (*missedCues)[i];
    if (cue) {
      SimpleTextTrackEvent* event = new SimpleTextTrackEvent(
          NS_LITERAL_STRING("enter"), cue->StartTime(), cue->GetTrack(), cue);
      eventList.InsertElementSorted(
          event, CompareSimpleTextTrackEvents(mMediaElement));
      affectedTracks.AddTextTrack(cue->GetTrack(),
                                  CompareTextTracks(mMediaElement));
    }
  }

  // Step 11, 17.
  for (uint32_t i = 0; i < otherCues->Length(); ++i) {
    TextTrackCue* cue = (*otherCues)[i];
    if (cue->GetActive() || missedCues->IsCueExist(cue)) {
      double time =
          cue->StartTime() > cue->EndTime() ? cue->StartTime() : cue->EndTime();
      SimpleTextTrackEvent* event = new SimpleTextTrackEvent(
          NS_LITERAL_STRING("exit"), time, cue->GetTrack(), cue);
      eventList.InsertElementSorted(
          event, CompareSimpleTextTrackEvents(mMediaElement));
      affectedTracks.AddTextTrack(cue->GetTrack(),
                                  CompareTextTracks(mMediaElement));
    }
    cue->SetActive(false);
  }

  // Step 12, 17.
  for (uint32_t i = 0; i < currentCues->Length(); ++i) {
    TextTrackCue* cue = (*currentCues)[i];
    if (!cue->GetActive()) {
      SimpleTextTrackEvent* event = new SimpleTextTrackEvent(
          NS_LITERAL_STRING("enter"), cue->StartTime(), cue->GetTrack(), cue);
      eventList.InsertElementSorted(
          event, CompareSimpleTextTrackEvents(mMediaElement));
      affectedTracks.AddTextTrack(cue->GetTrack(),
                                  CompareTextTracks(mMediaElement));
    }
    cue->SetActive(true);
  }

  // Fire the eventList
  for (uint32_t i = 0; i < eventList.Length(); ++i) {
    eventList[i]->Dispatch();
  }

  // Step 16.
  for (uint32_t i = 0; i < affectedTracks.Length(); ++i) {
    TextTrack* ttrack = affectedTracks[i];
    if (ttrack) {
      ttrack->DispatchAsyncTrustedEvent(NS_LITERAL_STRING("cuechange"));
      HTMLTrackElement* trackElement = ttrack->GetTrackElement();
      if (trackElement) {
        trackElement->DispatchTrackRunnable(NS_LITERAL_STRING("cuechange"));
      }
    }
  }

  mLastTimeMarchesOnCalled = currentPlaybackTime;
  mLastActiveCues = currentCues;

  // Step 18.
  UpdateCueDisplay();
}

void TextTrackManager::NotifyCueUpdated(TextTrackCue* aCue) {
  // TODO: Add/Reorder the cue to mNewCues if we have some optimization?
  WEBVTT_LOG("NotifyCueUpdated");
  TimeMarchesOn();
  // For the case "Texttrack.mode = hidden/showing", if the mode
  // changing between showing and hidden, TimeMarchesOn
  // doesn't render the cue. Call DispatchUpdateCueDisplay() explicitly.
  DispatchUpdateCueDisplay();
}

void TextTrackManager::NotifyReset() {
  WEBVTT_LOG("NotifyReset");
  mLastTimeMarchesOnCalled = 0.0;
}

void TextTrackManager::ReportTelemetryForTrack(TextTrack* aTextTrack) const {
  MOZ_ASSERT(NS_IsMainThread());
  MOZ_ASSERT(aTextTrack);
  MOZ_ASSERT(mTextTracks->Length() > 0);

  TextTrackKind kind = aTextTrack->Kind();
  Telemetry::Accumulate(Telemetry::WEBVTT_TRACK_KINDS, uint32_t(kind));
}

void TextTrackManager::ReportTelemetryForCue() {
  MOZ_ASSERT(NS_IsMainThread());
  MOZ_ASSERT(!mNewCues->IsEmpty() || !mLastActiveCues->IsEmpty());

  if (!mCueTelemetryReported) {
    Telemetry::Accumulate(Telemetry::WEBVTT_USED_VTT_CUES, 1);
    mCueTelemetryReported = true;
  }
}

bool TextTrackManager::IsLoaded() {
  return mTextTracks ? mTextTracks->AreTextTracksLoaded() : true;
}

bool TextTrackManager::IsShutdown() const {
  return (mShutdown || !sParserWrapper);
}

}  // namespace dom
}  // namespace mozilla