/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.text.UITextDisplayer');
goog.require('goog.asserts');
goog.require('shaka.text.Cue');
goog.require('shaka.text.CueRegion');
goog.require('shaka.util.Dom');
goog.require('shaka.util.EventManager');
goog.require('shaka.util.Timer');
/**
* The text displayer plugin for the Shaka Player UI. Can also be used directly
* by providing an appropriate container element.
*
* @implements {shaka.extern.TextDisplayer}
* @final
* @export
*/
shaka.text.UITextDisplayer = class {
/**
* Constructor.
* @param {HTMLMediaElement} video
* @param {HTMLElement} videoContainer
* @param {shaka.extern.TextDisplayerConfiguration} config
*/
constructor(video, videoContainer, config) {
goog.asserts.assert(videoContainer, 'videoContainer should be valid.');
/** @private {boolean} */
this.isTextVisible_ = false;
/** @private {!Array.<!shaka.text.Cue>} */
this.cues_ = [];
/** @private {HTMLMediaElement} */
this.video_ = video;
/** @private {HTMLElement} */
this.videoContainer_ = videoContainer;
/** @private {?number} */
this.aspectRatio_ = null;
/** @type {HTMLElement} */
this.textContainer_ = shaka.util.Dom.createHTMLElement('div');
this.textContainer_.classList.add('shaka-text-container');
// Set the subtitles text-centered by default.
this.textContainer_.style.textAlign = 'center';
// Set the captions in the middle horizontally by default.
this.textContainer_.style.display = 'flex';
this.textContainer_.style.flexDirection = 'column';
this.textContainer_.style.alignItems = 'center';
// Set the captions at the bottom by default.
this.textContainer_.style.justifyContent = 'flex-end';
this.videoContainer_.appendChild(this.textContainer_);
/** @private {shaka.util.Timer} */
this.captionsTimer_ = new shaka.util.Timer(() => {
if (!this.video_.paused) {
this.updateCaptions_();
}
}).tickEvery(config.captionsUpdatePeriod);
/**
* Maps cues to cue elements. Specifically points out the wrapper element of
* the cue (e.g. the HTML element to put nested cues inside).
* @private {Map.<!shaka.text.Cue, !{
* cueElement: !HTMLElement,
* regionElement: HTMLElement,
* wrapper: !HTMLElement
* }>}
*/
this.currentCuesMap_ = new Map();
/** @private {shaka.util.EventManager} */
this.eventManager_ = new shaka.util.EventManager();
this.eventManager_.listen(document, 'fullscreenchange', () => {
this.updateCaptions_(/* forceUpdate= */ true);
});
this.eventManager_.listen(this.video_, 'seeking', () => {
this.updateCaptions_(/* forceUpdate= */ true);
});
// From: https://html.spec.whatwg.org/multipage/media.html#dom-video-videowidth
// Whenever the natural width or natural height of the video changes
// (including, for example, because the selected video track was changed),
// if the element's readyState attribute is not HAVE_NOTHING, the user
// agent must queue a media element task given the media element to fire an
// event named resize at the media element.
this.eventManager_.listen(this.video_, 'resize', () => {
const element = /** @type {!HTMLVideoElement} */ (this.video_);
const width = element.videoWidth;
const height = element.videoHeight;
if (width && height) {
this.aspectRatio_ = width / height;
} else {
this.aspectRatio_ = null;
}
});
/** @private {ResizeObserver} */
this.resizeObserver_ = null;
if ('ResizeObserver' in window) {
this.resizeObserver_ = new ResizeObserver(() => {
this.updateCaptions_(/* forceUpdate= */ true);
});
this.resizeObserver_.observe(this.textContainer_);
}
/** @private {Map.<string, !HTMLElement>} */
this.regionElements_ = new Map();
}
/**
* @override
* @export
*/
configure(config) {
if (this.captionsTimer_) {
this.captionsTimer_.tickEvery(config.captionsUpdatePeriod);
}
}
/**
* @override
* @export
*/
append(cues) {
// Clone the cues list for performace optimization. We can avoid the cues
// list growing during the comparisons for duplicate cues.
// See: https://github.com/shaka-project/shaka-player/issues/3018
const cuesList = [...this.cues_];
for (const cue of cues) {
// When a VTT cue spans a segment boundary, the cue will be duplicated
// into two segments.
// To avoid displaying duplicate cues, if the current cue list already
// contains the cue, skip it.
const containsCue = cuesList.some(
(cueInList) => shaka.text.Cue.equal(cueInList, cue));
if (!containsCue) {
this.cues_.push(cue);
}
}
this.updateCaptions_();
}
/**
* @override
* @export
*/
destroy() {
// Return resolved promise if destroy() has been called.
if (!this.textContainer_) {
return Promise.resolve();
}
// Remove the text container element from the UI.
this.videoContainer_.removeChild(this.textContainer_);
this.textContainer_ = null;
this.isTextVisible_ = false;
this.cues_ = [];
if (this.captionsTimer_) {
this.captionsTimer_.stop();
}
this.currentCuesMap_.clear();
// Tear-down the event manager to ensure messages stop moving around.
if (this.eventManager_) {
this.eventManager_.release();
this.eventManager_ = null;
}
if (this.resizeObserver_) {
this.resizeObserver_.disconnect();
this.resizeObserver_ = null;
}
return Promise.resolve();
}
/**
* @override
* @export
*/
remove(start, end) {
// Return false if destroy() has been called.
if (!this.textContainer_) {
return false;
}
// Remove the cues out of the time range.
const oldNumCues = this.cues_.length;
this.cues_ = this.cues_.filter(
(cue) => cue.startTime < start || cue.endTime >= end);
// If anything was actually removed in this process, force the captions to
// update. This makes sure that the currently-displayed cues will stop
// displaying if removed (say, due to the user changing languages).
const forceUpdate = oldNumCues > this.cues_.length;
this.updateCaptions_(forceUpdate);
return true;
}
/**
* @override
* @export
*/
isTextVisible() {
return this.isTextVisible_;
}
/**
* @override
* @export
*/
setTextVisibility(on) {
this.isTextVisible_ = on;
}
/**
* @private
*/
isElementUnderTextContainer_(elemToCheck) {
while (elemToCheck != null) {
if (elemToCheck == this.textContainer_) {
return true;
}
elemToCheck = elemToCheck.parentElement;
}
return false;
}
/**
* @param {!Array.<!shaka.text.Cue>} cues
* @param {!HTMLElement} container
* @param {number} currentTime
* @param {!Array.<!shaka.text.Cue>} parents
* @private
*/
updateCuesRecursive_(cues, container, currentTime, parents) {
// Set to true if the cues have changed in some way, which will require
// DOM changes. E.g. if a cue was added or removed.
let updateDOM = false;
/**
* The elements to remove from the DOM.
* Some of these elements may be added back again, if their corresponding
* cue is in toPlant.
* These elements are only removed if updateDOM is true.
* @type {!Array.<!HTMLElement>}
*/
const toUproot = [];
/**
* The cues whose corresponding elements should be in the DOM.
* Some of these might be new, some might have been displayed beforehand.
* These will only be added if updateDOM is true.
* @type {!Array.<!shaka.text.Cue>}
*/
const toPlant = [];
for (const cue of cues) {
parents.push(cue);
let cueRegistry = this.currentCuesMap_.get(cue);
const shouldBeDisplayed =
cue.startTime <= currentTime && cue.endTime > currentTime;
let wrapper = cueRegistry ? cueRegistry.wrapper : null;
if (cueRegistry) {
// If the cues are replanted, all existing cues should be uprooted,
// even ones which are going to be planted again.
toUproot.push(cueRegistry.cueElement);
// Also uproot all displayed region elements.
if (cueRegistry.regionElement) {
toUproot.push(cueRegistry.regionElement);
}
// If the cue should not be displayed, remove it entirely.
if (!shouldBeDisplayed) {
// Since something has to be removed, we will need to update the DOM.
updateDOM = true;
this.currentCuesMap_.delete(cue);
cueRegistry = null;
}
}
if (shouldBeDisplayed) {
toPlant.push(cue);
if (!cueRegistry) {
// The cue has to be made!
this.createCue_(cue, parents);
cueRegistry = this.currentCuesMap_.get(cue);
wrapper = cueRegistry.wrapper;
updateDOM = true;
} else if (!this.isElementUnderTextContainer_(wrapper)) {
// We found that the wrapper needs to be in the DOM
updateDOM = true;
}
}
// Recursively check the nested cues, to see if they need to be added or
// removed.
// If wrapper is null, that means that the cue is not only not being
// displayed currently, it also was not removed this tick. So it's
// guaranteed that the children will neither need to be added nor removed.
if (cue.nestedCues.length > 0 && wrapper) {
this.updateCuesRecursive_(
cue.nestedCues, wrapper, currentTime, parents);
}
const topCue = parents.pop();
goog.asserts.assert(topCue == cue, 'Parent cues should be kept in order');
}
if (updateDOM) {
for (const element of toUproot) {
// NOTE: Because we uproot shared region elements, too, we might hit an
// element here that has no parent because we've already processed it.
if (element.parentElement) {
element.parentElement.removeChild(element);
}
}
toPlant.sort((a, b) => {
if (a.startTime != b.startTime) {
return a.startTime - b.startTime;
} else {
return a.endTime - b.endTime;
}
});
for (const cue of toPlant) {
const cueRegistry = this.currentCuesMap_.get(cue);
goog.asserts.assert(cueRegistry, 'cueRegistry should exist.');
if (cueRegistry.regionElement) {
if (cueRegistry.regionElement.contains(container)) {
cueRegistry.regionElement.removeChild(container);
}
container.appendChild(cueRegistry.regionElement);
cueRegistry.regionElement.appendChild(cueRegistry.cueElement);
} else {
container.appendChild(cueRegistry.cueElement);
}
}
}
}
/**
* Display the current captions.
* @param {boolean=} forceUpdate
* @private
*/
updateCaptions_(forceUpdate = false) {
if (!this.textContainer_) {
return;
}
const currentTime = this.video_.currentTime;
if (!this.isTextVisible_ || forceUpdate) {
// Remove child elements from all regions.
for (const regionElement of this.regionElements_.values()) {
shaka.util.Dom.removeAllChildren(regionElement);
}
// Remove all top-level elements in the text container.
shaka.util.Dom.removeAllChildren(this.textContainer_);
// Clear the element maps.
this.currentCuesMap_.clear();
this.regionElements_.clear();
}
if (this.isTextVisible_) {
// Log currently attached cue elements for verification, later.
const previousCuesMap = new Map();
if (goog.DEBUG) {
for (const cue of this.currentCuesMap_.keys()) {
previousCuesMap.set(cue, this.currentCuesMap_.get(cue));
}
}
// Update the cues.
this.updateCuesRecursive_(
this.cues_, this.textContainer_, currentTime, /* parents= */ []);
if (goog.DEBUG) {
// Previously, we had an issue (#2076) where cues sometimes were not
// properly removed from the DOM. It is not clear if this issue still
// happens, so the previous fix for it has been changed to an assert.
for (const cue of previousCuesMap.keys()) {
if (!this.currentCuesMap_.has(cue)) {
// TODO: If the problem does not appear again, then we should remove
// this assert (and the previousCuesMap code) in Shaka v4.
const cueElement = previousCuesMap.get(cue).cueElement;
goog.asserts.assert(
!cueElement.parentNode, 'Cue was not properly removed!');
}
}
}
}
}
/**
* Compute a unique internal id:
* Regions can reuse the id but have different dimensions, we need to
* consider those differences
* @param {shaka.text.CueRegion} region
* @private
*/
generateRegionId_(region) {
const percentageUnit = shaka.text.CueRegion.units.PERCENTAGE;
const heightUnit = region.heightUnits == percentageUnit ? '%' : 'px';
const viewportAnchorUnit =
region.viewportAnchorUnits == percentageUnit ? '%' : 'px';
const uniqueRegionId = `${region.id}_${
region.width}x${region.height}${heightUnit}-${
region.viewportAnchorX}x${region.viewportAnchorY}${viewportAnchorUnit}`;
return uniqueRegionId;
}
/**
* Get or create a region element corresponding to the cue region. These are
* cached by ID.
*
* @param {!shaka.text.Cue} cue
* @return {!HTMLElement}
* @private
*/
getRegionElement_(cue) {
const region = cue.region;
// from https://dvcs.w3.org/hg/text-tracks/raw-file/default/608toVTT/608toVTT.html#caption-window-size
// if aspect ratio is 4/3, use that value, otherwise, use the 16:9 value
const lineWidthMultiple = this.aspectRatio_ === 4/3 ? 2.5 : 1.9;
const lineHeightMultiple = 5.33;
const regionId = this.generateRegionId_(region);
if (this.regionElements_.has(regionId)) {
return this.regionElements_.get(regionId);
}
const regionElement = shaka.util.Dom.createHTMLElement('span');
const percentageUnit = shaka.text.CueRegion.units.PERCENTAGE;
const heightUnit = region.heightUnits == percentageUnit ? '%' : 'px';
const widthUnit = region.widthUnits == percentageUnit ? '%' : 'px';
const viewportAnchorUnit =
region.viewportAnchorUnits == percentageUnit ? '%' : 'px';
regionElement.id = 'shaka-text-region---' + regionId;
regionElement.classList.add('shaka-text-region');
regionElement.style.position = 'absolute';
const linesUnit = shaka.text.CueRegion.units.LINES;
if (region.heightUnits === linesUnit && region.widthUnits === linesUnit) {
regionElement.style.height = region.height * lineHeightMultiple + '%';
regionElement.style.width = region.width * lineWidthMultiple + '%';
} else {
regionElement.style.height = region.height + heightUnit;
regionElement.style.width = region.width + widthUnit;
}
if (region.viewportAnchorUnits === linesUnit) {
// from https://dvcs.w3.org/hg/text-tracks/raw-file/default/608toVTT/608toVTT.html#positioning-in-cea-708
let top = region.viewportAnchorY / 75 * 100;
const windowWidth = this.aspectRatio_ === 4/3 ? 160 : 210;
let left = region.viewportAnchorX / windowWidth * 100;
// adjust top and left values based on the region anchor and window size
top -= region.regionAnchorY * region.height * lineHeightMultiple / 100;
left -= region.regionAnchorX * region.width * lineWidthMultiple / 100;
regionElement.style.top = top + '%';
regionElement.style.left = left + '%';
} else {
regionElement.style.top = region.viewportAnchorY -
region.regionAnchorY * region.height / 100 + viewportAnchorUnit;
regionElement.style.left = region.viewportAnchorX -
region.regionAnchorX * region.width / 100 + viewportAnchorUnit;
}
regionElement.style.display = 'flex';
regionElement.style.flexDirection = 'column';
regionElement.style.alignItems = 'center';
if (cue.displayAlign == shaka.text.Cue.displayAlign.BEFORE) {
regionElement.style.justifyContent = 'flex-start';
} else if (cue.displayAlign == shaka.text.Cue.displayAlign.CENTER) {
regionElement.style.justifyContent = 'center';
} else {
regionElement.style.justifyContent = 'flex-end';
}
this.regionElements_.set(regionId, regionElement);
return regionElement;
}
/**
* Creates the object for a cue.
*
* @param {!shaka.text.Cue} cue
* @param {!Array.<!shaka.text.Cue>} parents
* @private
*/
createCue_(cue, parents) {
const isNested = parents.length > 1;
let type = isNested ? 'span' : 'div';
if (cue.lineBreak) {
type = 'br';
}
if (cue.rubyTag) {
type = cue.rubyTag;
}
const needWrapper = !isNested && cue.nestedCues.length > 0;
// Nested cues are inline elements. Top-level cues are block elements.
const cueElement = shaka.util.Dom.createHTMLElement(type);
if (type != 'br') {
this.setCaptionStyles_(cueElement, cue, parents, needWrapper);
}
let regionElement = null;
if (cue.region && cue.region.id) {
regionElement = this.getRegionElement_(cue);
}
let wrapper = cueElement;
if (needWrapper) {
// Create a wrapper element which will serve to contain all children into
// a single item. This ensures that nested span elements appear
// horizontally and br elements occupy no vertical space.
wrapper = shaka.util.Dom.createHTMLElement('span');
wrapper.classList.add('shaka-text-wrapper');
wrapper.style.backgroundColor = cue.backgroundColor;
wrapper.style.lineHeight = 'normal';
cueElement.appendChild(wrapper);
}
this.currentCuesMap_.set(cue, {cueElement, wrapper, regionElement});
}
/**
* Compute cue position alignment
* See https://www.w3.org/TR/webvtt1/#webvtt-cue-position-alignment
*
* @param {!shaka.text.Cue} cue
* @private
*/
computeCuePositionAlignment_(cue) {
const Cue = shaka.text.Cue;
const {direction, positionAlign, textAlign} = cue;
if (positionAlign !== Cue.positionAlign.AUTO) {
// Position align is not AUTO: use it
return positionAlign;
}
// Position align is AUTO: use text align to compute its value
if (textAlign === Cue.textAlign.LEFT ||
(textAlign === Cue.textAlign.START &&
direction === Cue.direction.HORIZONTAL_LEFT_TO_RIGHT) ||
(textAlign === Cue.textAlign.END &&
direction === Cue.direction.HORIZONTAL_RIGHT_TO_LEFT)) {
return Cue.positionAlign.LEFT;
}
if (textAlign === Cue.textAlign.RIGHT ||
(textAlign === Cue.textAlign.START &&
direction === Cue.direction.HORIZONTAL_RIGHT_TO_LEFT) ||
(textAlign === Cue.textAlign.END &&
direction === Cue.direction.HORIZONTAL_LEFT_TO_RIGHT)) {
return Cue.positionAlign.RIGHT;
}
return Cue.positionAlign.CENTER;
}
/**
* @param {!HTMLElement} cueElement
* @param {!shaka.text.Cue} cue
* @param {!Array.<!shaka.text.Cue>} parents
* @param {boolean} hasWrapper
* @private
*/
setCaptionStyles_(cueElement, cue, parents, hasWrapper) {
const Cue = shaka.text.Cue;
const inherit =
(cb) => shaka.text.UITextDisplayer.inheritProperty_(parents, cb);
const style = cueElement.style;
const isLeaf = cue.nestedCues.length == 0;
const isNested = parents.length > 1;
// TODO: wrapLine is not yet supported. Lines always wrap.
// White space should be preserved if emitted by the text parser. It's the
// job of the parser to omit any whitespace that should not be displayed.
// Using 'pre-wrap' means that whitespace is preserved even at the end of
// the text, but that lines which overflow can still be broken.
style.whiteSpace = 'pre-wrap';
// Using 'break-spaces' would be better, as it would preserve even trailing
// spaces, but that only shipped in Chrome 76. As of July 2020, Safari
// still has not implemented break-spaces, and the original Chromecast will
// never have this feature since it no longer gets firmware updates.
// So we need to replace trailing spaces with non-breaking spaces.
const text = cue.payload.replace(/\s+$/g, (match) => {
const nonBreakingSpace = '\xa0';
return nonBreakingSpace.repeat(match.length);
});
style.webkitTextStrokeColor = cue.textStrokeColor;
style.webkitTextStrokeWidth = cue.textStrokeWidth;
style.color = cue.color;
style.direction = cue.direction;
style.opacity = cue.opacity;
style.paddingLeft = shaka.text.UITextDisplayer.convertLengthValue_(
cue.linePadding, cue, this.videoContainer_);
style.paddingRight =
shaka.text.UITextDisplayer.convertLengthValue_(
cue.linePadding, cue, this.videoContainer_);
style.textCombineUpright = cue.textCombineUpright;
style.textShadow = cue.textShadow;
if (cue.backgroundImage) {
style.backgroundImage = 'url(\'' + cue.backgroundImage + '\')';
style.backgroundRepeat = 'no-repeat';
style.backgroundSize = 'contain';
style.backgroundPosition = 'center';
// Quoting https://www.w3.org/TR/ttml-imsc1.2/:
// "The width and height (in pixels) of the image resource referenced by
// smpte:backgroundImage SHALL be equal to the width and height expressed
// by the tts:extent attribute of the region in which the div element is
// presented".
style.width = '100%';
style.height = '100%';
} else {
// If we have both text and nested cues, then style everything; otherwise
// place the text in its own <span> so the background doesn't fill the
// whole region.
let elem;
if (cue.nestedCues.length) {
elem = cueElement;
} else {
elem = shaka.util.Dom.createHTMLElement('span');
cueElement.appendChild(elem);
}
if (cue.border) {
elem.style.border = cue.border;
}
if (!hasWrapper) {
const bgColor = inherit((c) => c.backgroundColor);
if (bgColor) {
elem.style.backgroundColor = bgColor;
} else if (text) {
// If there is no background, default to a semi-transparent black.
// Only do this for the text itself.
elem.style.backgroundColor = 'rgba(0, 0, 0, 0.8)';
}
const fontFamily = inherit((c) => c.fontFamily);
if (fontFamily) {
elem.style.fontFamily = fontFamily;
}
}
if (text) {
elem.textContent = text;
}
}
// The displayAlign attribute specifies the vertical alignment of the
// captions inside the text container. Before means at the top of the
// text container, and after means at the bottom.
if (isNested && !parents[parents.length - 1].isContainer) {
style.display = 'inline';
} else {
style.display = 'flex';
style.flexDirection = 'column';
style.alignItems = 'center';
if (cue.displayAlign == Cue.displayAlign.BEFORE) {
style.justifyContent = 'flex-start';
} else if (cue.displayAlign == Cue.displayAlign.CENTER) {
style.justifyContent = 'center';
} else {
style.justifyContent = 'flex-end';
}
}
if (!isLeaf) {
style.margin = '0';
}
style.fontFamily = cue.fontFamily;
style.fontWeight = cue.fontWeight.toString();
style.fontStyle = cue.fontStyle;
style.letterSpacing = cue.letterSpacing;
style.fontSize = shaka.text.UITextDisplayer.convertLengthValue_(
cue.fontSize, cue, this.videoContainer_);
// The line attribute defines the positioning of the text container inside
// the video container.
// - The line offsets the text container from the top, the right or left of
// the video viewport as defined by the writing direction.
// - The value of the line is either as a number of lines, or a percentage
// of the video viewport height or width.
// The lineAlign is an alignment for the text container's line.
// - The Start alignment means the text container’s top side (for horizontal
// cues), left side (for vertical growing right), or right side (for
// vertical growing left) is aligned at the line.
// - The Center alignment means the text container is centered at the line
// (to be implemented).
// - The End Alignment means The text container’s bottom side (for
// horizontal cues), right side (for vertical growing right), or left side
// (for vertical growing left) is aligned at the line.
// TODO: Implement line alignment with line number.
// TODO: Implement lineAlignment of 'CENTER'.
let line = cue.line;
if (line != null) {
let lineInterpretation = cue.lineInterpretation;
// HACK: the current implementation of UITextDisplayer only handled
// PERCENTAGE, so we need convert LINE_NUMBER to PERCENTAGE
if (lineInterpretation == Cue.lineInterpretation.LINE_NUMBER) {
lineInterpretation = Cue.lineInterpretation.PERCENTAGE;
let maxLines = 16;
// The maximum number of lines is different if it is a vertical video.
if (this.aspectRatio_ && this.aspectRatio_ < 1) {
maxLines = 32;
}
if (line < 0) {
line = 100 + line / maxLines * 100;
} else {
line = line / maxLines * 100;
}
}
if (lineInterpretation == Cue.lineInterpretation.PERCENTAGE) {
style.position = 'absolute';
if (cue.writingMode == Cue.writingMode.HORIZONTAL_TOP_TO_BOTTOM) {
style.width = '100%';
if (cue.lineAlign == Cue.lineAlign.START) {
style.top = line + '%';
} else if (cue.lineAlign == Cue.lineAlign.END) {
style.bottom = (100 - line) + '%';
}
} else if (cue.writingMode == Cue.writingMode.VERTICAL_LEFT_TO_RIGHT) {
style.height = '100%';
if (cue.lineAlign == Cue.lineAlign.START) {
style.left = line + '%';
} else if (cue.lineAlign == Cue.lineAlign.END) {
style.right = (100 - line) + '%';
}
} else {
style.height = '100%';
if (cue.lineAlign == Cue.lineAlign.START) {
style.right = line + '%';
} else if (cue.lineAlign == Cue.lineAlign.END) {
style.left = (100 - line) + '%';
}
}
}
}
style.lineHeight = cue.lineHeight;
// The position defines the indent of the text container in the
// direction defined by the writing direction.
if (cue.position != null) {
if (cue.writingMode == Cue.writingMode.HORIZONTAL_TOP_TO_BOTTOM) {
style.paddingLeft = cue.position;
} else {
style.paddingTop = cue.position;
}
}
// The positionAlign attribute is an alignment for the text container in
// the dimension of the writing direction.
const computedPositionAlign = this.computeCuePositionAlignment_(cue);
if (computedPositionAlign == Cue.positionAlign.LEFT) {
style.cssFloat = 'left';
} else if (computedPositionAlign == Cue.positionAlign.RIGHT) {
style.cssFloat = 'right';
}
style.textAlign = cue.textAlign;
style.textDecoration = cue.textDecoration.join(' ');
style.writingMode = cue.writingMode;
// Old versions of Chromium, which may be found in certain versions of Tizen
// and WebOS, may require the prefixed version: webkitWritingMode.
// https://caniuse.com/css-writing-mode
// However, testing shows that Tizen 3, at least, has a 'writingMode'
// property, but the setter for it does nothing. Therefore we need to
// detect that and fall back to the prefixed version in this case, too.
if (!('writingMode' in document.documentElement.style) ||
style.writingMode != cue.writingMode) {
// Note that here we do not bother to check for webkitWritingMode support
// explicitly. We try the unprefixed version, then fall back to the
// prefixed version unconditionally.
style.webkitWritingMode = cue.writingMode;
}
// The size is a number giving the size of the text container, to be
// interpreted as a percentage of the video, as defined by the writing
// direction.
if (cue.size) {
if (cue.writingMode == Cue.writingMode.HORIZONTAL_TOP_TO_BOTTOM) {
style.width = cue.size + '%';
} else {
style.height = cue.size + '%';
}
}
}
/**
* Returns info about provided lengthValue
* @example 100px => { value: 100, unit: 'px' }
* @param {?string} lengthValue
*
* @return {?{ value: number, unit: string }}
* @private
*/
static getLengthValueInfo_(lengthValue) {
const matches = new RegExp(/(\d*\.?\d+)([a-z]+|%+)/).exec(lengthValue);
if (!matches) {
return null;
}
return {
value: Number(matches[1]),
unit: matches[2],
};
}
/**
* Converts length value to an absolute value in pixels.
* If lengthValue is already an absolute value it will not
* be modified. Relative lengthValue will be converted to an
* absolute value in pixels based on Computed Cell Size
*
* @param {string} lengthValue
* @param {!shaka.text.Cue} cue
* @param {HTMLElement} videoContainer
* @return {string}
* @private
*/
static convertLengthValue_(lengthValue, cue, videoContainer) {
const lengthValueInfo =
shaka.text.UITextDisplayer.getLengthValueInfo_(lengthValue);
if (!lengthValueInfo) {
return lengthValue;
}
const {unit, value} = lengthValueInfo;
switch (unit) {
case '%':
return shaka.text.UITextDisplayer.getAbsoluteLengthInPixels_(
value / 100, cue, videoContainer);
case 'c':
return shaka.text.UITextDisplayer.getAbsoluteLengthInPixels_(
value, cue, videoContainer);
default:
return lengthValue;
}
}
/**
* Returns computed absolute length value in pixels based on cell
* and a video container size
* @param {number} value
* @param {!shaka.text.Cue} cue
* @param {HTMLElement} videoContainer
* @return {string}
*
* @private
* */
static getAbsoluteLengthInPixels_(value, cue, videoContainer) {
const containerHeight = videoContainer.clientHeight;
return (containerHeight * value / cue.cellResolution.rows) + 'px';
}
/**
* Inherits a property from the parent Cue elements. If the value is falsy,
* it is assumed to be inherited from the parent. This returns null if the
* value isn't found.
*
* @param {!Array.<!shaka.text.Cue>} parents
* @param {function(!shaka.text.Cue):?T} cb
* @return {?T}
* @template T
* @private
*/
static inheritProperty_(parents, cb) {
for (let i = parents.length - 1; i >= 0; i--) {
const val = cb(parents[i]);
if (val || val === 0) {
return val;
}
}
return null;
}
};