/
ttml_text_parser.js
1343 lines (1189 loc) · 42.8 KB
/
ttml_text_parser.js
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/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.text.TtmlTextParser');
goog.require('goog.asserts');
goog.require('shaka.log');
goog.require('shaka.text.Cue');
goog.require('shaka.text.CueRegion');
goog.require('shaka.text.TextEngine');
goog.require('shaka.util.ArrayUtils');
goog.require('shaka.util.Error');
goog.require('shaka.util.StringUtils');
goog.require('shaka.util.XmlUtils');
/**
* @implements {shaka.extern.TextParser}
* @export
*/
shaka.text.TtmlTextParser = class {
/**
* @override
* @export
*/
parseInit(data) {
goog.asserts.assert(false, 'TTML does not have init segments');
}
/**
* @override
* @export
*/
parseMedia(data, time) {
const TtmlTextParser = shaka.text.TtmlTextParser;
const XmlUtils = shaka.util.XmlUtils;
const ttpNs = TtmlTextParser.parameterNs_;
const ttsNs = TtmlTextParser.styleNs_;
const str = shaka.util.StringUtils.fromUTF8(data);
const cues = [];
const parser = new DOMParser();
let xml = null;
// dont try to parse empty string as
// DOMParser will not throw error but return an errored xml
if (str == '') {
return cues;
}
try {
xml = parser.parseFromString(str, 'text/xml');
} catch (exception) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.TEXT,
shaka.util.Error.Code.INVALID_XML,
'Failed to parse TTML.');
}
if (xml) {
const parserError = xml.getElementsByTagName('parsererror')[0];
if (parserError) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.TEXT,
shaka.util.Error.Code.INVALID_XML,
parserError.textContent);
}
const tt = xml.getElementsByTagName('tt')[0];
// TTML should always have tt element.
if (!tt) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.TEXT,
shaka.util.Error.Code.INVALID_XML,
'TTML does not contain <tt> tag.');
}
const body = tt.getElementsByTagName('body')[0];
if (!body) {
return [];
}
// Get the framerate, subFrameRate and frameRateMultiplier if applicable.
const frameRate = XmlUtils.getAttributeNSList(tt, ttpNs, 'frameRate');
const subFrameRate = XmlUtils.getAttributeNSList(
tt, ttpNs, 'subFrameRate');
const frameRateMultiplier =
XmlUtils.getAttributeNSList(tt, ttpNs, 'frameRateMultiplier');
const tickRate = XmlUtils.getAttributeNSList(tt, ttpNs, 'tickRate');
const cellResolution = XmlUtils.getAttributeNSList(
tt, ttpNs, 'cellResolution');
const spaceStyle = tt.getAttribute('xml:space') || 'default';
const extent = XmlUtils.getAttributeNSList(tt, ttsNs, 'extent');
if (spaceStyle != 'default' && spaceStyle != 'preserve') {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.TEXT,
shaka.util.Error.Code.INVALID_XML,
'Invalid xml:space value: ' + spaceStyle);
}
const whitespaceTrim = spaceStyle == 'default';
const rateInfo = new TtmlTextParser.RateInfo_(
frameRate, subFrameRate, frameRateMultiplier, tickRate);
const cellResolutionInfo =
TtmlTextParser.getCellResolution_(cellResolution);
const metadata = tt.getElementsByTagName('metadata')[0];
const metadataElements = metadata ? XmlUtils.getChildren(metadata) : [];
const styles = Array.from(tt.getElementsByTagName('style'));
const regionElements = Array.from(tt.getElementsByTagName('region'));
const cueRegions = [];
for (const region of regionElements) {
const cueRegion =
TtmlTextParser.parseCueRegion_(region, styles, extent);
if (cueRegion) {
cueRegions.push(cueRegion);
}
}
// A <body> element should only contain <div> elements, not <p> or <span>
// elements. We used to allow this, but it is non-compliant, and the
// loose nature of our previous parser made it difficult to implement TTML
// nesting more fully.
if (XmlUtils.findChildren(body, 'p').length) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.TEXT,
shaka.util.Error.Code.INVALID_TEXT_CUE,
'<p> can only be inside <div> in TTML');
}
for (const div of XmlUtils.findChildren(body, 'div')) {
// A <div> element should only contain <p>, not <span>.
if (XmlUtils.findChildren(div, 'span').length) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.TEXT,
shaka.util.Error.Code.INVALID_TEXT_CUE,
'<span> can only be inside <p> in TTML');
}
}
const cue = TtmlTextParser.parseCue_(
body, time.periodStart, rateInfo, metadataElements, styles,
regionElements, cueRegions, whitespaceTrim,
cellResolutionInfo, /* parentCueElement= */ null,
/* isContent= */ false);
if (cue) {
cues.push(cue);
}
}
return cues;
}
/**
* Parses a TTML node into a Cue.
*
* @param {!Node} cueNode
* @param {number} offset
* @param {!shaka.text.TtmlTextParser.RateInfo_} rateInfo
* @param {!Array.<!Element>} metadataElements
* @param {!Array.<!Element>} styles
* @param {!Array.<!Element>} regionElements
* @param {!Array.<!shaka.text.CueRegion>} cueRegions
* @param {boolean} whitespaceTrim
* @param {?{columns: number, rows: number}} cellResolution
* @param {?Element} parentCueElement
* @param {boolean} isContent
* @return {shaka.text.Cue}
* @private
*/
static parseCue_(
cueNode, offset, rateInfo, metadataElements, styles, regionElements,
cueRegions, whitespaceTrim, cellResolution, parentCueElement, isContent) {
/** @type {Element} */
let cueElement;
/** @type {Element} */
let parentElement = /** @type {Element} */ (cueNode.parentNode);
if (cueNode.nodeType == Node.COMMENT_NODE) {
// The comments do not contain information that interests us here.
return null;
}
if (cueNode.nodeType == Node.TEXT_NODE) {
if (!isContent) {
// Ignore text elements outside the content. For example, whitespace
// on the same lexical level as the <p> elements, in a document with
// xml:space="preserve", should not be renderer.
return null;
}
// This should generate an "anonymous span" according to the TTML spec.
// So pretend the element was a <span>. parentElement was set above, so
// we should still be able to correctly traverse up for timing
// information later.
const span = document.createElement('span');
span.textContent = cueNode.textContent;
cueElement = span;
} else {
goog.asserts.assert(cueNode.nodeType == Node.ELEMENT_NODE,
'nodeType should be ELEMENT_NODE!');
cueElement = /** @type {!Element} */(cueNode);
}
goog.asserts.assert(cueElement, 'cueElement should be non-null!');
let imageElement = null;
for (const nameSpace of shaka.text.TtmlTextParser.smpteNsList_) {
imageElement = shaka.text.TtmlTextParser.getElementsFromCollection_(
cueElement, 'backgroundImage', metadataElements, '#',
nameSpace)[0];
if (imageElement) {
break;
}
}
const parentIsContent = isContent;
if (cueNode.nodeName == 'p' || imageElement) {
isContent = true;
}
const spaceStyle = cueElement.getAttribute('xml:space') ||
(whitespaceTrim ? 'default' : 'preserve');
const localWhitespaceTrim = spaceStyle == 'default';
// Parse any nested cues first.
const isTextNode = (node) => {
return node.nodeType == Node.TEXT_NODE;
};
const isLeafNode = Array.from(cueElement.childNodes).every(isTextNode);
const nestedCues = [];
if (!isLeafNode) {
// Otherwise, recurse into the children. Text nodes will convert into
// anonymous spans, which will then be leaf nodes.
for (const childNode of cueElement.childNodes) {
const nestedCue = shaka.text.TtmlTextParser.parseCue_(
childNode,
offset,
rateInfo,
metadataElements,
styles,
regionElements,
cueRegions,
localWhitespaceTrim,
cellResolution,
cueElement,
isContent,
);
// This node may or may not generate a nested cue.
if (nestedCue) {
nestedCues.push(nestedCue);
}
}
}
const isNested = /** @type {boolean} */ (parentCueElement != null);
// In this regex, "\S" means "non-whitespace character".
const hasTextContent = /\S/.test(cueElement.textContent);
const hasTimeAttributes =
cueElement.hasAttribute('begin') ||
cueElement.hasAttribute('end') ||
cueElement.hasAttribute('dur');
if (!hasTimeAttributes && !hasTextContent && cueElement.tagName != 'br' &&
nestedCues.length == 0) {
if (!isNested) {
// Disregards empty <p> elements without time attributes nor content.
// <p begin="..." smpte:backgroundImage="..." /> will go through,
// as some information could be held by its attributes.
// <p /> won't, as it would not be displayed.
return null;
} else if (localWhitespaceTrim) {
// Disregards empty anonymous spans when (local) trim is true.
return null;
}
}
// Get local time attributes.
let {start, end} = shaka.text.TtmlTextParser.parseTime_(
cueElement, rateInfo);
// Resolve local time relative to parent elements. Time elements can appear
// all the way up to 'body', but not 'tt'.
while (parentElement && parentElement.nodeType == Node.ELEMENT_NODE &&
parentElement.tagName != 'tt') {
({start, end} = shaka.text.TtmlTextParser.resolveTime_(
parentElement, rateInfo, start, end));
parentElement = /** @type {Element} */(parentElement.parentNode);
}
if (start == null) {
start = 0;
}
start += offset;
// If end is null, that means the duration is effectively infinite.
if (end == null) {
end = Infinity;
} else {
end += offset;
}
if (!hasTimeAttributes && nestedCues.length > 0) {
// If no time is defined for this cue, base the timing information on
// the time of the nested cues. In the case of multiple nested cues with
// different start times, it is the text displayer's responsibility to
// make sure that only the appropriate nested cue is drawn at any given
// time.
start = Infinity;
end = 0;
for (const cue of nestedCues) {
start = Math.min(start, cue.startTime);
end = Math.max(end, cue.endTime);
}
}
if (cueElement.tagName == 'br') {
const cue = new shaka.text.Cue(start, end, '');
cue.lineBreak = true;
return cue;
}
let payload = '';
if (isLeafNode) {
// If the childNodes are all text, this is a leaf node. Get the payload.
payload = cueElement.textContent;
if (localWhitespaceTrim) {
// Trim leading and trailing whitespace.
payload = payload.trim();
// Collapse multiple spaces into one.
payload = payload.replace(/\s+/g, ' ');
}
}
const cue = new shaka.text.Cue(start, end, payload);
cue.nestedCues = nestedCues;
if (!isContent) {
// If this is not a <p> element or a <div> with images, and it has no
// parent that was a <p> element, then it's part of the outer containers
// (e.g. the <body> or a normal <div> element within it).
cue.isContainer = true;
}
if (cellResolution) {
cue.cellResolution = cellResolution;
}
// Get other properties if available.
const regionElement = shaka.text.TtmlTextParser.getElementsFromCollection_(
cueElement, 'region', regionElements, /* prefix= */ '')[0];
// Do not actually apply that region unless it is non-inherited, though.
// This makes it so that, if a parent element has a region, the children
// don't also all independently apply the positioning of that region.
if (cueElement.hasAttribute('region')) {
if (regionElement && regionElement.getAttribute('xml:id')) {
const regionId = regionElement.getAttribute('xml:id');
cue.region = cueRegions.filter((region) => region.id == regionId)[0];
}
}
let regionElementForStyle = regionElement;
if (parentCueElement && isNested && !cueElement.getAttribute('region') &&
!cueElement.getAttribute('style')) {
regionElementForStyle =
shaka.text.TtmlTextParser.getElementsFromCollection_(
parentCueElement, 'region', regionElements, /* prefix= */ '')[0];
}
shaka.text.TtmlTextParser.addStyle_(
cue,
cueElement,
regionElementForStyle,
imageElement,
styles,
/** isNested= */ parentIsContent, // "nested in a <div>" doesn't count.
/** isLeaf= */ (nestedCues.length == 0));
return cue;
}
/**
* Parses an Element into a TextTrackCue or VTTCue.
*
* @param {!Element} regionElement
* @param {!Array.<!Element>} styles Defined in the top of tt element and
* used principally for images.
* @param {?string} globalExtent
* @return {shaka.text.CueRegion}
* @private
*/
static parseCueRegion_(regionElement, styles, globalExtent) {
const TtmlTextParser = shaka.text.TtmlTextParser;
const region = new shaka.text.CueRegion();
const id = regionElement.getAttribute('xml:id');
if (!id) {
shaka.log.warning('TtmlTextParser parser encountered a region with ' +
'no id. Region will be ignored.');
return null;
}
region.id = id;
let globalResults = null;
if (globalExtent) {
globalResults = TtmlTextParser.percentValues_.exec(globalExtent) ||
TtmlTextParser.pixelValues_.exec(globalExtent);
}
const globalWidth = globalResults ? Number(globalResults[1]) : null;
const globalHeight = globalResults ? Number(globalResults[2]) : null;
let results = null;
let percentage = null;
const extent = TtmlTextParser.getStyleAttributeFromRegion_(
regionElement, styles, 'extent');
if (extent) {
percentage = TtmlTextParser.percentValues_.exec(extent);
results = percentage || TtmlTextParser.pixelValues_.exec(extent);
if (results != null) {
region.width = Number(results[1]);
region.height = Number(results[2]);
if (!percentage) {
if (globalWidth != null) {
region.width = region.width * 100 / globalWidth;
}
if (globalHeight != null) {
region.height = region.height * 100 / globalHeight;
}
}
region.widthUnits = percentage || globalWidth != null ?
shaka.text.CueRegion.units.PERCENTAGE :
shaka.text.CueRegion.units.PX;
region.heightUnits = percentage || globalHeight != null ?
shaka.text.CueRegion.units.PERCENTAGE :
shaka.text.CueRegion.units.PX;
}
}
const origin = TtmlTextParser.getStyleAttributeFromRegion_(
regionElement, styles, 'origin');
if (origin) {
percentage = TtmlTextParser.percentValues_.exec(origin);
results = percentage || TtmlTextParser.pixelValues_.exec(origin);
if (results != null) {
region.viewportAnchorX = Number(results[1]);
region.viewportAnchorY = Number(results[2]);
if (!percentage) {
if (globalHeight != null) {
region.viewportAnchorY = region.viewportAnchorY * 100 /
globalHeight;
}
if (globalWidth != null) {
region.viewportAnchorX = region.viewportAnchorX * 100 /
globalWidth;
}
}
region.viewportAnchorUnits = percentage || globalWidth != null ?
shaka.text.CueRegion.units.PERCENTAGE :
shaka.text.CueRegion.units.PX;
}
}
return region;
}
/**
* Adds applicable style properties to a cue.
*
* @param {!shaka.text.Cue} cue
* @param {!Element} cueElement
* @param {Element} region
* @param {Element} imageElement
* @param {!Array.<!Element>} styles
* @param {boolean} isNested
* @param {boolean} isLeaf
* @private
*/
static addStyle_(
cue, cueElement, region, imageElement, styles, isNested, isLeaf) {
const TtmlTextParser = shaka.text.TtmlTextParser;
const Cue = shaka.text.Cue;
// Styles should be inherited from regions, if a style property is not
// associated with a Content element (or an anonymous span).
const shouldInheritRegionStyles = isNested || isLeaf;
const direction = TtmlTextParser.getStyleAttribute_(
cueElement, region, styles, 'direction', shouldInheritRegionStyles);
if (direction == 'rtl') {
cue.direction = Cue.direction.HORIZONTAL_RIGHT_TO_LEFT;
}
// Direction attribute specifies one-dimentional writing direction
// (left to right or right to left). Writing mode specifies that
// plus whether text is vertical or horizontal.
// They should not contradict each other. If they do, we give
// preference to writing mode.
const writingMode = TtmlTextParser.getStyleAttribute_(
cueElement, region, styles, 'writingMode', shouldInheritRegionStyles);
// Set cue's direction if the text is horizontal, and cue's writingMode if
// it's vertical.
if (writingMode == 'tb' || writingMode == 'tblr') {
cue.writingMode = Cue.writingMode.VERTICAL_LEFT_TO_RIGHT;
} else if (writingMode == 'tbrl') {
cue.writingMode = Cue.writingMode.VERTICAL_RIGHT_TO_LEFT;
} else if (writingMode == 'rltb' || writingMode == 'rl') {
cue.direction = Cue.direction.HORIZONTAL_RIGHT_TO_LEFT;
} else if (writingMode) {
cue.direction = Cue.direction.HORIZONTAL_LEFT_TO_RIGHT;
}
const align = TtmlTextParser.getStyleAttribute_(
cueElement, region, styles, 'textAlign', shouldInheritRegionStyles);
if (align) {
cue.positionAlign = TtmlTextParser.textAlignToPositionAlign_[align];
cue.lineAlign = TtmlTextParser.textAlignToLineAlign_[align];
goog.asserts.assert(align.toUpperCase() in Cue.textAlign,
align.toUpperCase() +
' Should be in Cue.textAlign values!');
cue.textAlign = Cue.textAlign[align.toUpperCase()];
} else {
// Default value is START: https://bit.ly/32OGmvo
cue.textAlign = Cue.textAlign.START;
}
const displayAlign = TtmlTextParser.getStyleAttribute_(
cueElement, region, styles, 'displayAlign', shouldInheritRegionStyles);
if (displayAlign) {
goog.asserts.assert(displayAlign.toUpperCase() in Cue.displayAlign,
displayAlign.toUpperCase() +
' Should be in Cue.displayAlign values!');
cue.displayAlign = Cue.displayAlign[displayAlign.toUpperCase()];
}
const color = TtmlTextParser.getStyleAttribute_(
cueElement, region, styles, 'color', shouldInheritRegionStyles);
if (color) {
cue.color = color;
}
// Background color should not be set on a container. If this is a nested
// cue, you can set the background. If it's a top-level that happens to
// also be a leaf, you can set the background.
// See https://github.com/google/shaka-player/issues/2623
// This used to be handled in the displayer, but that is confusing. The Cue
// structure should reflect what you want to happen in the displayer, and
// the displayer shouldn't have to know about TTML.
const backgroundColor = TtmlTextParser.getStyleAttribute_(
cueElement, region, styles, 'backgroundColor',
shouldInheritRegionStyles);
if (backgroundColor) {
cue.backgroundColor = backgroundColor;
}
const border = TtmlTextParser.getStyleAttribute_(
cueElement, region, styles, 'border', shouldInheritRegionStyles);
if (border) {
cue.border = border;
}
const fontFamily = TtmlTextParser.getStyleAttribute_(
cueElement, region, styles, 'fontFamily', shouldInheritRegionStyles);
if (fontFamily) {
cue.fontFamily = fontFamily;
}
const fontWeight = TtmlTextParser.getStyleAttribute_(
cueElement, region, styles, 'fontWeight', shouldInheritRegionStyles);
if (fontWeight && fontWeight == 'bold') {
cue.fontWeight = Cue.fontWeight.BOLD;
}
const wrapOption = TtmlTextParser.getStyleAttribute_(
cueElement, region, styles, 'wrapOption', shouldInheritRegionStyles);
if (wrapOption && wrapOption == 'noWrap') {
cue.wrapLine = false;
} else {
cue.wrapLine = true;
}
const lineHeight = TtmlTextParser.getStyleAttribute_(
cueElement, region, styles, 'lineHeight', shouldInheritRegionStyles);
if (lineHeight && lineHeight.match(TtmlTextParser.unitValues_)) {
cue.lineHeight = lineHeight;
}
const fontSize = TtmlTextParser.getStyleAttribute_(
cueElement, region, styles, 'fontSize', shouldInheritRegionStyles);
if (fontSize) {
const isValidFontSizeUnit =
fontSize.match(TtmlTextParser.unitValues_) ||
fontSize.match(TtmlTextParser.percentValue_);
if (isValidFontSizeUnit) {
cue.fontSize = fontSize;
}
}
const fontStyle = TtmlTextParser.getStyleAttribute_(
cueElement, region, styles, 'fontStyle', shouldInheritRegionStyles);
if (fontStyle) {
goog.asserts.assert(fontStyle.toUpperCase() in Cue.fontStyle,
fontStyle.toUpperCase() +
' Should be in Cue.fontStyle values!');
cue.fontStyle = Cue.fontStyle[fontStyle.toUpperCase()];
}
if (imageElement) {
// According to the spec, we should use imageType (camelCase), but
// historically we have checked for imagetype (lowercase).
// This was the case since background image support was first introduced
// in PR #1859, in April 2019, and first released in v2.5.0.
// Now we check for both, although only imageType (camelCase) is to spec.
const backgroundImageType =
imageElement.getAttribute('imageType') ||
imageElement.getAttribute('imagetype');
const backgroundImageEncoding = imageElement.getAttribute('encoding');
const backgroundImageData = imageElement.textContent.trim();
if (backgroundImageType == 'PNG' &&
backgroundImageEncoding == 'Base64' &&
backgroundImageData) {
cue.backgroundImage = 'data:image/png;base64,' + backgroundImageData;
}
}
const letterSpacing = TtmlTextParser.getStyleAttribute_(
cueElement, region, styles, 'letterSpacing', shouldInheritRegionStyles);
if (letterSpacing && letterSpacing.match(TtmlTextParser.unitValues_)) {
cue.letterSpacing = letterSpacing;
}
const linePadding = TtmlTextParser.getStyleAttribute_(
cueElement, region, styles, 'linePadding', shouldInheritRegionStyles);
if (linePadding && linePadding.match(TtmlTextParser.unitValues_)) {
cue.linePadding = linePadding;
}
const opacity = TtmlTextParser.getStyleAttribute_(
cueElement, region, styles, 'opacity', shouldInheritRegionStyles);
if (opacity) {
cue.opacity = parseFloat(opacity);
}
// Text decoration is an array of values which can come both from the
// element's style or be inherited from elements' parent nodes. All of those
// values should be applied as long as they don't contradict each other. If
// they do, elements' own style gets preference.
const textDecorationRegion = TtmlTextParser.getStyleAttributeFromRegion_(
region, styles, 'textDecoration');
if (textDecorationRegion) {
TtmlTextParser.addTextDecoration_(cue, textDecorationRegion);
}
const textDecorationElement = TtmlTextParser.getStyleAttributeFromElement_(
cueElement, styles, 'textDecoration');
if (textDecorationElement) {
TtmlTextParser.addTextDecoration_(cue, textDecorationElement);
}
}
/**
* Parses text decoration values and adds/removes them to/from the cue.
*
* @param {!shaka.text.Cue} cue
* @param {string} decoration
* @private
*/
static addTextDecoration_(cue, decoration) {
const Cue = shaka.text.Cue;
for (const value of decoration.split(' ')) {
switch (value) {
case 'underline':
if (!cue.textDecoration.includes(Cue.textDecoration.UNDERLINE)) {
cue.textDecoration.push(Cue.textDecoration.UNDERLINE);
}
break;
case 'noUnderline':
if (cue.textDecoration.includes(Cue.textDecoration.UNDERLINE)) {
shaka.util.ArrayUtils.remove(cue.textDecoration,
Cue.textDecoration.UNDERLINE);
}
break;
case 'lineThrough':
if (!cue.textDecoration.includes(Cue.textDecoration.LINE_THROUGH)) {
cue.textDecoration.push(Cue.textDecoration.LINE_THROUGH);
}
break;
case 'noLineThrough':
if (cue.textDecoration.includes(Cue.textDecoration.LINE_THROUGH)) {
shaka.util.ArrayUtils.remove(cue.textDecoration,
Cue.textDecoration.LINE_THROUGH);
}
break;
case 'overline':
if (!cue.textDecoration.includes(Cue.textDecoration.OVERLINE)) {
cue.textDecoration.push(Cue.textDecoration.OVERLINE);
}
break;
case 'noOverline':
if (cue.textDecoration.includes(Cue.textDecoration.OVERLINE)) {
shaka.util.ArrayUtils.remove(cue.textDecoration,
Cue.textDecoration.OVERLINE);
}
break;
}
}
}
/**
* Finds a specified attribute on either the original cue element or its
* associated region and returns the value if the attribute was found.
*
* @param {!Element} cueElement
* @param {Element} region
* @param {!Array.<!Element>} styles
* @param {string} attribute
* @param {boolean=} shouldInheritRegionStyles
* @return {?string}
* @private
*/
static getStyleAttribute_(cueElement, region, styles, attribute,
shouldInheritRegionStyles=true) {
// An attribute can be specified on region level or in a styling block
// associated with the region or original element.
const TtmlTextParser = shaka.text.TtmlTextParser;
const attr = TtmlTextParser.getStyleAttributeFromElement_(
cueElement, styles, attribute);
if (attr) {
return attr;
}
if (shouldInheritRegionStyles) {
return TtmlTextParser.getStyleAttributeFromRegion_(
region, styles, attribute);
}
return null;
}
/**
* Finds a specified attribute on the element's associated region
* and returns the value if the attribute was found.
*
* @param {Element} region
* @param {!Array.<!Element>} styles
* @param {string} attribute
* @return {?string}
* @private
*/
static getStyleAttributeFromRegion_(region, styles, attribute) {
const XmlUtils = shaka.util.XmlUtils;
const ttsNs = shaka.text.TtmlTextParser.styleNs_;
if (!region) {
return null;
}
const attr = XmlUtils.getAttributeNSList(region, ttsNs, attribute);
if (attr) {
return attr;
}
return shaka.text.TtmlTextParser.getInheritedStyleAttribute_(
region, styles, attribute);
}
/**
* Finds a specified attribute on the cue element and returns the value
* if the attribute was found.
*
* @param {!Element} cueElement
* @param {!Array.<!Element>} styles
* @param {string} attribute
* @return {?string}
* @private
*/
static getStyleAttributeFromElement_(cueElement, styles, attribute) {
const XmlUtils = shaka.util.XmlUtils;
const ttsNs = shaka.text.TtmlTextParser.styleNs_;
// Styling on elements should take precedence
// over the main styling attributes
const elementAttribute = XmlUtils.getAttributeNSList(
cueElement,
ttsNs,
attribute);
if (elementAttribute) {
return elementAttribute;
}
return shaka.text.TtmlTextParser.getInheritedStyleAttribute_(
cueElement, styles, attribute);
}
/**
* Finds a specified attribute on an element's styles and the styles those
* styles inherit from.
*
* @param {!Element} element
* @param {!Array.<!Element>} styles
* @param {string} attribute
* @return {?string}
* @private
*/
static getInheritedStyleAttribute_(element, styles, attribute) {
const XmlUtils = shaka.util.XmlUtils;
const ttsNs = shaka.text.TtmlTextParser.styleNs_;
const ebuttsNs = shaka.text.TtmlTextParser.styleEbuttsNs_;
const inheritedStyles =
shaka.text.TtmlTextParser.getElementsFromCollection_(
element, 'style', styles, /* prefix= */ '');
let styleValue = null;
// The last value in our styles stack takes the precedence over the others
for (let i = 0; i < inheritedStyles.length; i++) {
// Check ebu namespace first.
let styleAttributeValue = XmlUtils.getAttributeNS(
inheritedStyles[i],
ebuttsNs,
attribute);
if (!styleAttributeValue) {
// Fall back to tts namespace.
styleAttributeValue = XmlUtils.getAttributeNSList(
inheritedStyles[i],
ttsNs,
attribute);
}
if (!styleAttributeValue) {
// Next, check inheritance.
// Styles can inherit from other styles, so traverse up that chain.
styleAttributeValue =
shaka.text.TtmlTextParser.getStyleAttributeFromElement_(
inheritedStyles[i], styles, attribute);
}
if (styleAttributeValue) {
styleValue = styleAttributeValue;
}
}
return styleValue;
}
/**
* Selects items from |collection| whose id matches |attributeName|
* from |element|.
*
* @param {Element} element
* @param {string} attributeName
* @param {!Array.<Element>} collection
* @param {string} prefixName
* @param {string=} nsName
* @return {!Array.<!Element>}
* @private
*/
static getElementsFromCollection_(
element, attributeName, collection, prefixName, nsName) {
const items = [];
if (!element || collection.length < 1) {
return items;
}
const attributeValue = shaka.text.TtmlTextParser.getInheritedAttribute_(
element, attributeName, nsName);
if (attributeValue) {
// There could be multiple items in one attribute
// <span style="style1 style2">A cue</span>
const itemNames = attributeValue.split(' ');
for (const name of itemNames) {
for (const item of collection) {
if ((prefixName + item.getAttribute('xml:id')) == name) {
items.push(item);
break;
}
}
}
}
return items;
}
/**
* Traverses upwards from a given node until a given attribute is found.
*
* @param {!Element} element
* @param {string} attributeName
* @param {string=} nsName
* @return {?string}
* @private
*/
static getInheritedAttribute_(element, attributeName, nsName) {
let ret = null;
const XmlUtils = shaka.util.XmlUtils;
while (element) {
ret = nsName ? XmlUtils.getAttributeNS(element, nsName, attributeName)
: element.getAttribute(attributeName);
if (ret) {
break;
}
// Element.parentNode can lead to XMLDocument, which is not an Element and
// has no getAttribute().
const parentNode = element.parentNode;
if (parentNode instanceof Element) {
element = parentNode;
} else {
break;
}
}
return ret;
}
/**
* Factor parent/ancestor time attributes into the parsed time of a
* child/descendent.
*
* @param {!Element} parentElement
* @param {!shaka.text.TtmlTextParser.RateInfo_} rateInfo
* @param {?number} start The child's start time
* @param {?number} end The child's end time
* @return {{start: ?number, end: ?number}}
* @private
*/
static resolveTime_(parentElement, rateInfo, start, end) {
const parentTime = shaka.text.TtmlTextParser.parseTime_(
parentElement, rateInfo);
if (start == null) {
// No start time of your own? Inherit from the parent.
start = parentTime.start;
} else {
// Otherwise, the start time is relative to the parent's start time.
if (parentTime.start != null) {
start += parentTime.start;
}
}
if (end == null) {
// No end time of your own? Inherit from the parent.
end = parentTime.end;
} else {
// Otherwise, the end time is relative to the parent's _start_ time.
// This is not a typo. Both times are relative to the parent's _start_.
if (parentTime.start != null) {
end += parentTime.start;
}
}
return {start, end};
}
/**
* Parse TTML time attributes from the given element.
*
* @param {!Element} element
* @param {!shaka.text.TtmlTextParser.RateInfo_} rateInfo
* @return {{start: ?number, end: ?number}}
* @private
*/
static parseTime_(element, rateInfo) {
const start = shaka.text.TtmlTextParser.parseTimeAttribute_(
element.getAttribute('begin'), rateInfo);
let end = shaka.text.TtmlTextParser.parseTimeAttribute_(
element.getAttribute('end'), rateInfo);
const duration = shaka.text.TtmlTextParser.parseTimeAttribute_(
element.getAttribute('dur'), rateInfo);
if (end == null && duration != null) {
end = start + duration;
}
return {start, end};
}