shaka-player
Version:
DASH/EME video player library
268 lines (232 loc) • 7.12 kB
JavaScript
/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @fileoverview
*/
goog.provide('shaka.text.SimpleTextDisplayer');
goog.require('goog.asserts');
goog.require('shaka.text.Utils');
/**
* A text displayer plugin using the browser's native VTTCue interface.
*
* @implements {shaka.extern.TextDisplayer}
* @export
*/
shaka.text.SimpleTextDisplayer = class {
/**
* @param {HTMLMediaElement} video
* @param {string} label
*/
constructor(video, label) {
/** @private {HTMLMediaElement} */
this.video_ = video;
/** @private {string} */
this.textTrackLabel_ = label;
/** @private {TextTrack} */
this.textTrack_ = null;
// TODO: Test that in all cases, the built-in CC controls in the video
// element are toggling our TextTrack.
// If the video element has TextTracks, disable them. If we see one that
// was created by a previous instance of Shaka Player, reuse it.
for (const track of Array.from(this.video_.textTracks)) {
if (track.kind === 'metadata' || track.kind === 'chapters') {
continue;
}
// NOTE: There is no API available to remove a TextTrack from a video
// element.
track.mode = 'disabled';
if (track.label == this.textTrackLabel_) {
this.textTrack_ = track;
}
}
if (this.textTrack_) {
this.textTrack_.mode = 'hidden';
}
}
/**
* @override
* @export
*/
configure(config) {
// Unused.
}
/**
* @override
* @export
*/
remove(start, end) {
// Check that the displayer hasn't been destroyed.
if (!this.textTrack_) {
return false;
}
const removeInRange = (cue) => {
const inside = cue.startTime < end && cue.endTime > start;
return inside;
};
shaka.text.SimpleTextDisplayer.removeWhere_(this.textTrack_, removeInRange);
return true;
}
/**
* @override
* @export
*/
append(cues) {
if (!this.textTrack_) {
return;
}
const flattenedCues = shaka.text.Utils.getCuesToFlatten(cues);
// Convert cues.
const textTrackCues = [];
const cuesInTextTrack = this.textTrack_.cues ?
Array.from(this.textTrack_.cues) : [];
for (const inCue of flattenedCues) {
// When a VTT cue spans a segment boundary, the cue will be duplicated
// into two segments.
// To avoid displaying duplicate cues, if the current textTrack cues
// list already contains the cue, skip it.
const containsCue = cuesInTextTrack.some((cueInTextTrack) => {
if (cueInTextTrack.startTime == inCue.startTime &&
cueInTextTrack.endTime == inCue.endTime &&
cueInTextTrack.text == inCue.payload) {
return true;
}
return false;
});
if (!containsCue && inCue.payload) {
const cue =
shaka.text.Utils.mapShakaCueToNativeCue(inCue);
if (cue) {
textTrackCues.push(cue);
}
}
}
// Sort the cues based on start/end times. Make a copy of the array so
// we can get the index in the original ordering. Out of order cues are
// rejected by Edge. See https://bit.ly/2K9VX3s
const sortedCues = textTrackCues.slice().sort((a, b) => {
if (a.startTime != b.startTime) {
return a.startTime - b.startTime;
} else if (a.endTime != b.endTime) {
return a.endTime - b.startTime;
} else {
// The browser will display cues with identical time ranges from the
// bottom up. Reversing the order of equal cues means the first one
// parsed will be at the top, as you would expect.
// See https://github.com/shaka-project/shaka-player/issues/848 for
// more info.
// However, this ordering behavior is part of VTTCue's "line" field.
// Some platforms don't have a real VTTCue and use a polyfill instead.
// When VTTCue is polyfilled or does not support "line", we should _not_
// reverse the order. This occurs on legacy Edge.
// eslint-disable-next-line no-restricted-syntax
if ('line' in VTTCue.prototype) {
// Native VTTCue
return textTrackCues.indexOf(b) - textTrackCues.indexOf(a);
} else {
// Polyfilled VTTCue
return textTrackCues.indexOf(a) - textTrackCues.indexOf(b);
}
}
});
for (const cue of sortedCues) {
this.textTrack_.addCue(cue);
}
}
/**
* @override
* @export
*/
destroy() {
if (this.textTrack_) {
const removeIt = (cue) => true;
shaka.text.SimpleTextDisplayer.removeWhere_(this.textTrack_, removeIt);
// NOTE: There is no API available to remove a TextTrack from a video
// element.
this.textTrack_.mode = 'disabled';
}
this.video_ = null;
this.textTrack_ = null;
return Promise.resolve();
}
/**
* @override
* @export
*/
isTextVisible() {
if (!this.textTrack_) {
return false;
}
return this.textTrack_.mode == 'showing';
}
/**
* @override
* @export
*/
setTextVisibility(on) {
if (on && !this.textTrack_) {
this.createTextTrack_();
}
if (this.textTrack_) {
this.textTrack_.mode = on ? 'showing' : 'hidden';
}
}
/**
* @override
* @export
*/
setTextLanguage(language) {
}
/**
* @override
* @export
*/
enableTextDisplayer() {
this.createTextTrack_();
}
/**
* @private
*/
createTextTrack_() {
if (this.video_ && !this.textTrack_) {
// As far as I can tell, there is no observable difference between setting
// kind to 'subtitles' or 'captions' when creating the TextTrack object.
// The individual text tracks from the manifest will still have their own
// kinds which can be displayed in the app's UI.
this.textTrack_ =
this.video_.addTextTrack('subtitles', this.textTrackLabel_);
this.textTrack_.mode = 'hidden';
}
}
/**
* Iterate over all the cues in a text track and remove all those for which
* |predicate(cue)| returns true.
*
* @param {!TextTrack} track
* @param {function(!TextTrackCue):boolean} predicate
* @private
*/
static removeWhere_(track, predicate) {
// Since |track.cues| can be null if |track.mode| is "disabled", force it to
// something other than "disabled".
//
// If the track is already showing, then we should keep it as showing. But
// if it something else, we will use hidden so that we don't "flash" cues on
// the screen.
const oldState = track.mode;
const tempState = oldState == 'showing' ? 'showing' : 'hidden';
track.mode = tempState;
goog.asserts.assert(
track.cues,
'Cues should be accessible when mode is set to "' + tempState + '".');
// Create a copy of the list to avoid errors while iterating.
for (const cue of Array.from(track.cues)) {
if (cue && predicate(cue)) {
track.removeCue(cue);
}
}
track.mode = oldState;
}
};