/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @fileoverview
* @suppress {missingRequire} TODO(b/152540451): this shouldn't be needed
*/
goog.provide('shaka.text.SimpleTextDisplayer');
goog.require('goog.asserts');
goog.require('shaka.log');
goog.require('shaka.text.Cue');
/**
* A text displayer plugin using the browser's native VTTCue interface.
*
* @implements {shaka.extern.TextDisplayer}
* @export
*/
shaka.text.SimpleTextDisplayer = class {
/** @param {HTMLMediaElement} video */
constructor(video) {
/** @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(video.textTracks)) {
// NOTE: There is no API available to remove a TextTrack from a video
// element.
track.mode = 'disabled';
if (track.label == shaka.Player.TextTrackLabel) {
this.textTrack_ = track;
}
}
if (!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_ = video.addTextTrack(
'subtitles', shaka.Player.TextTrackLabel);
}
this.textTrack_.mode = 'hidden';
}
/**
* @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) {
// Flatten nested cue payloads recursively. If a cue has nested cues,
// their contents should be combined and replace the payload of the parent.
const flattenPayload = (cue) => {
// Handle styles (currently bold/italics/underline).
// TODO add support for color rendering.
const openStyleTags = [];
const bold = cue.fontWeight >= shaka.text.Cue.fontWeight.BOLD;
const italics = cue.fontStyle == shaka.text.Cue.fontStyle.ITALIC;
const underline = cue.textDecoration.includes(
shaka.text.Cue.textDecoration.UNDERLINE);
if (bold) {
openStyleTags.push('b');
}
if (italics) {
openStyleTags.push('i');
}
if (underline) {
openStyleTags.push('u');
}
// Prefix opens tags, suffix closes tags in reverse order of opening.
const prefixStyleTags = openStyleTags.reduce((acc, tag) => {
return `${acc}<${tag}>`;
}, '');
const suffixStyleTags = openStyleTags.reduceRight((acc, tag) => {
return `${acc}</${tag}>`;
}, '');
if (cue.lineBreak) {
// This is a vertical lineBreak, so insert a newline.
return '\n';
} else if (cue.nestedCues.length) {
return cue.nestedCues.map(flattenPayload).join('');
} else {
// This is a real cue.
return prefixStyleTags + cue.payload + suffixStyleTags;
}
};
// We don't want to modify the array or objects passed in, since we don't
// technically own them. So we build a new array and replace certain items
// in it if they need to be flattened.
// We also don't want to flatten the text payloads starting at a container
// element; otherwise, for containers encapsulating multiple caption lines,
// the lines would merge into a single cue. This is undesirable when a
// subset of the captions are outside of the append time window. To fix
// this, we only call flattenPayload() starting at elements marked as
// isContainer = false.
const getCuesToFlatten = (cues, result) => {
for (const cue of cues) {
if (cue.isContainer) {
// Recurse to find the actual text payload cues.
getCuesToFlatten(cue.nestedCues, result);
} else {
// Flatten the payload.
const flatCue = cue.clone();
flatCue.nestedCues = [];
flatCue.payload = flattenPayload(cue);
result.push(flatCue);
}
}
return result;
};
const flattenedCues = 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) {
const cue =
shaka.text.SimpleTextDisplayer.convertToTextTrackCue_(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.textTrack_ = null;
return Promise.resolve();
}
/**
* @override
* @export
*/
isTextVisible() {
return this.textTrack_.mode == 'showing';
}
/**
* @override
* @export
*/
setTextVisibility(on) {
this.textTrack_.mode = on ? 'showing' : 'hidden';
}
/**
* @param {!shaka.extern.Cue} shakaCue
* @return {TextTrackCue}
* @private
*/
static convertToTextTrackCue_(shakaCue) {
if (shakaCue.startTime >= shakaCue.endTime) {
// Edge will throw in this case.
// See issue #501
shaka.log.warning('Invalid cue times: ' + shakaCue.startTime +
' - ' + shakaCue.endTime);
return null;
}
const Cue = shaka.text.Cue;
/** @type {VTTCue} */
const vttCue = new VTTCue(
shakaCue.startTime,
shakaCue.endTime,
shakaCue.payload);
// NOTE: positionAlign and lineAlign settings are not supported by Chrome
// at the moment, so setting them will have no effect.
// The bug on chromium to implement them:
// https://bugs.chromium.org/p/chromium/issues/detail?id=633690
vttCue.lineAlign = shakaCue.lineAlign;
vttCue.positionAlign = shakaCue.positionAlign;
if (shakaCue.size) {
vttCue.size = shakaCue.size;
}
try {
// Safari 10 seems to throw on align='center'.
vttCue.align = shakaCue.textAlign;
} catch (exception) {}
if (shakaCue.textAlign == 'center' && vttCue.align != 'center') {
// We want vttCue.position = 'auto'. By default, |position| is set to
// "auto". If we set it to "auto" safari will throw an exception, so we
// must rely on the default value.
vttCue.align = 'middle';
}
if (shakaCue.writingMode ==
Cue.writingMode.VERTICAL_LEFT_TO_RIGHT) {
vttCue.vertical = 'lr';
} else if (shakaCue.writingMode ==
Cue.writingMode.VERTICAL_RIGHT_TO_LEFT) {
vttCue.vertical = 'rl';
}
// snapToLines flag is true by default
if (shakaCue.lineInterpretation == Cue.lineInterpretation.PERCENTAGE) {
vttCue.snapToLines = false;
}
if (shakaCue.line != null) {
vttCue.line = shakaCue.line;
}
if (shakaCue.position != null) {
vttCue.position = shakaCue.position;
}
return vttCue;
}
/**
* 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;
}
};