C++ TextTrackCue::track方法代码示例

void MediaControlRootElement::updateTextTrackDisplay()
{
    if (!m_textDisplayContainer)
        createTextTrackDisplay();

    CueList activeCues = toParentMediaElement(m_textDisplayContainer)->currentlyActiveCues();
    m_textTrackDisplay->removeChildren();
    bool nothingToDisplay = true;
    for (size_t i = 0; i < activeCues.size(); ++i) {
        TextTrackCue* cue = activeCues[i].data();
        ASSERT(cue->isActive());
        if (!cue->track() || cue->track()->mode() != TextTrack::SHOWING)
            continue;

        String cueText = cue->text();
        if (!cueText.isEmpty()) {
            if (!nothingToDisplay)
                m_textTrackDisplay->appendChild(document()->createElement(HTMLNames::brTag, false), ASSERT_NO_EXCEPTION);
            m_textTrackDisplay->appendChild(document()->createTextNode(cueText), ASSERT_NO_EXCEPTION);
            nothingToDisplay = false;
        }
    }

    if (!nothingToDisplay)
        m_textDisplayContainer->show();
    else
        m_textDisplayContainer->hide();
}

bool TextTrackCue::hasEquivalentStartTime(const TextTrackCue& cue) const
{
    MediaTime startTimeVariance = MediaTime::zeroTime();
    if (track())
        startTimeVariance = track()->startTimeVariance();
    else if (cue.track())
        startTimeVariance = cue.track()->startTimeVariance();

    return abs(abs(startMediaTime()) - abs(cue.startMediaTime())) <= startTimeVariance;
}

bool JSTextTrackCueOwner::isReachableFromOpaqueRoots(JSC::Handle<JSC::Unknown> handle, void*, SlotVisitor& visitor)
{
    JSTextTrackCue* jsTextTrackCue = jsCast<JSTextTrackCue*>(handle.get().asCell());
    TextTrackCue* textTrackCue = static_cast<TextTrackCue*>(jsTextTrackCue->impl());

    // If the cue is firing event listeners, its wrapper is reachable because
    // the wrapper is responsible for marking those event listeners.
    if (textTrackCue->isFiringEventListeners())
        return true;

    // If the cue has no event listeners and has no custom properties, it is not reachable.
    if (!textTrackCue->hasEventListeners() && !jsTextTrackCue->hasCustomProperties())
        return false;

    // If the cue is not associated with a track, it is not reachable.
    if (!textTrackCue->track())
        return false;

    return visitor.containsOpaqueRoot(root(textTrackCue->track()));
}

void JSTextTrackCue::visitChildren(JSCell* cell, SlotVisitor& visitor)
{
    JSTextTrackCue* jsTextTrackCue = jsCast<JSTextTrackCue*>(cell);
    ASSERT_GC_OBJECT_INHERITS(jsTextTrackCue, &s_info);
    COMPILE_ASSERT(StructureFlags & OverridesVisitChildren, OverridesVisitChildrenWithoutSettingFlag);
    ASSERT(jsTextTrackCue->structure()->typeInfo().overridesVisitChildren());
    Base::visitChildren(jsTextTrackCue, visitor);
    
    // Mark the cue's track root if it has one.
    TextTrackCue* textTrackCue = static_cast<TextTrackCue*>(jsTextTrackCue->impl());
    if (TextTrack* textTrack = textTrackCue->track())
        visitor.addOpaqueRoot(root(textTrack));
    
    textTrackCue->visitJSEventListeners(visitor);
}

void MediaControlTextTrackContainerElement::updateDisplay()
{
    HTMLMediaElement* mediaElement = toParentMediaElement(this);

    // 1. If the media element is an audio element, or is another playback
    // mechanism with no rendering area, abort these steps. There is nothing to
    // render.
    if (!mediaElement->isVideo())
        return;

    // 2. Let video be the media element or other playback mechanism.
    HTMLVideoElement* video = static_cast<HTMLVideoElement*>(mediaElement);

    // 3. Let output be an empty list of absolutely positioned CSS block boxes.
    Vector<RefPtr<HTMLDivElement> > output;

    // 4. If the user agent is exposing a user interface for video, add to
    // output one or more completely transparent positioned CSS block boxes that
    // cover the same region as the user interface.

    // 5. If the last time these rules were run, the user agent was not exposing
    // a user interface for video, but now it is, let reset be true. Otherwise,
    // let reset be false.

    // There is nothing to be done explicitly for 4th and 5th steps, as
    // everything is handled through CSS. The caption box is on top of the
    // controls box, in a container set with the -webkit-box display property.

    // 6. Let tracks be the subset of video's list of text tracks that have as
    // their rules for updating the text track rendering these rules for
    // updating the display of WebVTT text tracks, and whose text track mode is
    // showing or showing by default.
    // 7. Let cues be an empty list of text track cues.
    // 8. For each track track in tracks, append to cues all the cues from
    // track's list of cues that have their text track cue active flag set.
    CueList activeCues = video->currentlyActiveCues();

    // 9. If reset is false, then, for each text track cue cue in cues: if cue's
    // text track cue display state has a set of CSS boxes, then add those boxes
    // to output, and remove cue from cues.

    // There is nothing explicitly to be done here, as all the caching occurs
    // within the TextTrackCue instance itself. If parameters of the cue change,
    // the display tree is cleared.

    // 10. For each text track cue cue in cues that has not yet had
    // corresponding CSS boxes added to output, in text track cue order, run the
    // following substeps:
    for (size_t i = 0; i < activeCues.size(); ++i) {
        TextTrackCue* cue = activeCues[i].data();

        ASSERT(cue->isActive());
        if (!cue->track() || !cue->track()->isRendered())
            continue;

        RefPtr<TextTrackCueBox> displayBox = cue->getDisplayTree();

        if (displayBox->hasChildNodes() && !contains(static_cast<Node*>(displayBox.get())))
            // Note: the display tree of a cue is removed when the active flag of the cue is unset.
            appendChild(displayBox, ASSERT_NO_EXCEPTION, false);
    }

    // 11. Return output.
    hasChildNodes() ? show() : hide();
}

void MediaControlTextTrackContainerElement::updateDisplay()
{
    if (!mediaController()->closedCaptionsVisible())
        removeChildren();

    HTMLMediaElement* mediaElement = parentMediaElement(this);
    // 1. If the media element is an audio element, or is another playback
    // mechanism with no rendering area, abort these steps. There is nothing to
    // render.
    if (!mediaElement || !mediaElement->isVideo())
        return;

    // 2. Let video be the media element or other playback mechanism.
    HTMLVideoElement* video = toHTMLVideoElement(mediaElement);

    // 3. Let output be an empty list of absolutely positioned CSS block boxes.
    Vector<RefPtr<HTMLDivElement>> output;

    // 4. If the user agent is exposing a user interface for video, add to
    // output one or more completely transparent positioned CSS block boxes that
    // cover the same region as the user interface.

    // 5. If the last time these rules were run, the user agent was not exposing
    // a user interface for video, but now it is, let reset be true. Otherwise,
    // let reset be false.

    // There is nothing to be done explicitly for 4th and 5th steps, as
    // everything is handled through CSS. The caption box is on top of the
    // controls box, in a container set with the -webkit-box display property.

    // 6. Let tracks be the subset of video's list of text tracks that have as
    // their rules for updating the text track rendering these rules for
    // updating the display of WebVTT text tracks, and whose text track mode is
    // showing or showing by default.
    // 7. Let cues be an empty list of text track cues.
    // 8. For each track track in tracks, append to cues all the cues from
    // track's list of cues that have their text track cue active flag set.
    CueList activeCues = video->currentlyActiveCues();

    // 9. If reset is false, then, for each text track cue cue in cues: if cue's
    // text track cue display state has a set of CSS boxes, then add those boxes
    // to output, and remove cue from cues.

    // There is nothing explicitly to be done here, as all the caching occurs
    // within the TextTrackCue instance itself. If parameters of the cue change,
    // the display tree is cleared.

    // 10. For each text track cue cue in cues that has not yet had
    // corresponding CSS boxes added to output, in text track cue order, run the
    // following substeps:
    for (size_t i = 0; i < activeCues.size(); ++i) {
        TextTrackCue* cue = activeCues[i].data();

        ASSERT(cue->isActive());
        if (!cue->track() || !cue->track()->isRendered() || !cue->isActive() || cue->text().isEmpty())
            continue;

        RefPtr<TextTrackCueBox> displayBox = cue->getDisplayTree(m_videoDisplaySize.size());
        if (displayBox->hasChildNodes() && !contains(displayBox.get())) {
            // Note: the display tree of a cue is removed when the active flag of the cue is unset.
            appendChild(displayBox, ASSERT_NO_EXCEPTION, AttachNow);
            cue->setFontSize(m_fontSize, m_videoDisplaySize.size(), m_fontSizeIsImportant);
        }
    }

    // 11. Return output.
    if (hasChildNodes()) {
        show();
        if (mediaElement->requiresTextTrackRepresentation()) {
            if (!m_textTrackRepresentation)
                m_textTrackRepresentation = TextTrackRepresentation::create(this);
            mediaElement->setTextTrackRepresentation(m_textTrackRepresentation.get());

            if (Page* page = document().page())
                m_textTrackRepresentation->setContentScale(page->deviceScaleFactor());

            m_textTrackRepresentation->update();
            setInlineStyleProperty(CSSPropertyWidth, m_videoDisplaySize.size().width(), CSSPrimitiveValue::CSS_PX);
            setInlineStyleProperty(CSSPropertyHeight, m_videoDisplaySize.size().height(), CSSPrimitiveValue::CSS_PX);
        }
    } else {
        hide();
        clearTextTrackRepresentation();
    }
}

void MediaControlTextTrackContainerElement::updateDisplay()
{
    if (!mediaElement().closedCaptionsVisible()) {
        removeChildren();
        return;
    }

    // 1. If the media element is an audio element, or is another playback
    // mechanism with no rendering area, abort these steps. There is nothing to
    // render.
    if (isHTMLAudioElement(mediaElement()))
        return;

    // 2. Let video be the media element or other playback mechanism.
    HTMLVideoElement& video = toHTMLVideoElement(mediaElement());

    // 3. Let output be an empty list of absolutely positioned CSS block boxes.

    // 4. If the user agent is exposing a user interface for video, add to
    // output one or more completely transparent positioned CSS block boxes that
    // cover the same region as the user interface.

    // 5. If the last time these rules were run, the user agent was not exposing
    // a user interface for video, but now it is, let reset be true. Otherwise,
    // let reset be false.

    // There is nothing to be done explicitly for 4th and 5th steps, as
    // everything is handled through CSS. The caption box is on top of the
    // controls box, in a container set with the -webkit-box display property.

    // 6. Let tracks be the subset of video's list of text tracks that have as
    // their rules for updating the text track rendering these rules for
    // updating the display of WebVTT text tracks, and whose text track mode is
    // showing or showing by default.
    // 7. Let cues be an empty list of text track cues.
    // 8. For each track track in tracks, append to cues all the cues from
    // track's list of cues that have their text track cue active flag set.
    CueList activeCues = video.currentlyActiveCues();

    // 9. If reset is false, then, for each text track cue cue in cues: if cue's
    // text track cue display state has a set of CSS boxes, then add those boxes
    // to output, and remove cue from cues.

    // There is nothing explicitly to be done here, as all the caching occurs
    // within the TextTrackCue instance itself. If parameters of the cue change,
    // the display tree is cleared.

    // 10. For each text track cue cue in cues that has not yet had
    // corresponding CSS boxes added to output, in text track cue order, run the
    // following substeps:
    for (size_t i = 0; i < activeCues.size(); ++i) {
        TextTrackCue* cue = activeCues[i].data();

        ASSERT(cue->isActive());
        if (!cue->track() || !cue->track()->isRendered() || !cue->isActive())
            continue;

        cue->updateDisplay(m_videoDisplaySize.size(), *this);
    }

    // 11. Return output.
    if (hasChildren())
        show();
    else
        hide();
}