358 lines
12 KiB
Plaintext
358 lines
12 KiB
Plaintext
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// The Layout object is the prototype of Substitution objects, and provides
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// utility methods to manipulate common layout tables (GPOS, GSUB, GDEF...)
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import check from './check';
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function searchTag(arr, tag) {
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/* jshint bitwise: false */
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let imin = 0;
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let imax = arr.length - 1;
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while (imin <= imax) {
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const imid = (imin + imax) >>> 1;
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const val = arr[imid].tag;
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if (val === tag) {
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return imid;
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} else if (val < tag) {
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imin = imid + 1;
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} else {
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imax = imid - 1;
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}
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}
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// Not found: return -1-insertion point
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return -imin - 1;
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}
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function binSearch(arr, value) {
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/* jshint bitwise: false */
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let imin = 0;
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let imax = arr.length - 1;
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while (imin <= imax) {
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const imid = (imin + imax) >>> 1;
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const val = arr[imid];
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if (val === value) {
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return imid;
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} else if (val < value) {
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imin = imid + 1;
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} else {
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imax = imid - 1;
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}
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}
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// Not found: return -1-insertion point
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return -imin - 1;
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}
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// binary search in a list of ranges (coverage, class definition)
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function searchRange(ranges, value) {
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// jshint bitwise: false
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let range;
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let imin = 0;
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let imax = ranges.length - 1;
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while (imin <= imax) {
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const imid = (imin + imax) >>> 1;
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range = ranges[imid];
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const start = range.start;
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if (start === value) {
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return range;
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} else if (start < value) {
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imin = imid + 1;
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} else {
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imax = imid - 1;
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}
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}
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if (imin > 0) {
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range = ranges[imin - 1];
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if (value > range.end) return 0;
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return range;
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}
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}
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/**
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* @exports opentype.Layout
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* @class
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*/
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function Layout(font, tableName) {
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this.font = font;
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this.tableName = tableName;
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}
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Layout.prototype = {
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/**
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* Binary search an object by "tag" property
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* @instance
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* @function searchTag
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* @memberof opentype.Layout
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* @param {Array} arr
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* @param {string} tag
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* @return {number}
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*/
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searchTag: searchTag,
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/**
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* Binary search in a list of numbers
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* @instance
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* @function binSearch
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* @memberof opentype.Layout
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* @param {Array} arr
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* @param {number} value
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* @return {number}
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*/
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binSearch: binSearch,
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/**
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* Get or create the Layout table (GSUB, GPOS etc).
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* @param {boolean} create - Whether to create a new one.
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* @return {Object} The GSUB or GPOS table.
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*/
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getTable: function (create) {
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let layout = this.font.tables[this.tableName];
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if (!layout && create) {
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layout = this.font.tables[this.tableName] =
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this.createDefaultTable();
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}
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return layout;
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},
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/**
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* Returns the best bet for a script name.
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* Returns 'DFLT' if it exists.
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* If not, returns 'latn' if it exists.
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* If neither exist, returns undefined.
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*/
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getDefaultScriptName: function () {
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let layout = this.getTable();
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if (!layout) {
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return;
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}
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let hasLatn = false;
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for (let i = 0; i < layout.scripts.length; i++) {
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const name = layout.scripts[i].tag;
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if (name === 'DFLT') return name;
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if (name === 'latn') hasLatn = true;
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}
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if (hasLatn) return 'latn';
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},
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/**
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* Returns all LangSysRecords in the given script.
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* @instance
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* @param {string} [script='DFLT']
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* @param {boolean} create - forces the creation of this script table if it doesn't exist.
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* @return {Object} An object with tag and script properties.
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*/
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getScriptTable: function (script, create) {
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const layout = this.getTable(create);
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if (layout) {
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script = script || 'DFLT';
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const scripts = layout.scripts;
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const pos = searchTag(layout.scripts, script);
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if (pos >= 0) {
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return scripts[pos].script;
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} else if (create) {
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const scr = {
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tag: script,
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script: {
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defaultLangSys: {
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reserved: 0,
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reqFeatureIndex: 0xffff,
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featureIndexes: [],
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},
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langSysRecords: [],
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},
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};
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scripts.splice(-1 - pos, 0, scr);
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return scr.script;
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}
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}
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},
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/**
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* Returns a language system table
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* @instance
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* @param {string} [script='DFLT']
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* @param {string} [language='dlft']
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* @param {boolean} create - forces the creation of this langSysTable if it doesn't exist.
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* @return {Object}
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*/
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getLangSysTable: function (script, language, create) {
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const scriptTable = this.getScriptTable(script, create);
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if (scriptTable) {
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if (!language || language === 'dflt' || language === 'DFLT') {
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return scriptTable.defaultLangSys;
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}
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const pos = searchTag(scriptTable.langSysRecords, language);
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if (pos >= 0) {
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return scriptTable.langSysRecords[pos].langSys;
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} else if (create) {
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const langSysRecord = {
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tag: language,
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langSys: {
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reserved: 0,
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reqFeatureIndex: 0xffff,
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featureIndexes: [],
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},
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};
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scriptTable.langSysRecords.splice(-1 - pos, 0, langSysRecord);
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return langSysRecord.langSys;
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}
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}
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},
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/**
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* Get a specific feature table.
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* @instance
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* @param {string} [script='DFLT']
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* @param {string} [language='dlft']
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* @param {string} feature - One of the codes listed at https://www.microsoft.com/typography/OTSPEC/featurelist.htm
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* @param {boolean} create - forces the creation of the feature table if it doesn't exist.
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* @return {Object}
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*/
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getFeatureTable: function (script, language, feature, create) {
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const langSysTable = this.getLangSysTable(script, language, create);
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if (langSysTable) {
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let featureRecord;
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const featIndexes = langSysTable.featureIndexes;
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const allFeatures = this.font.tables[this.tableName].features;
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// The FeatureIndex array of indices is in arbitrary order,
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// even if allFeatures is sorted alphabetically by feature tag.
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for (let i = 0; i < featIndexes.length; i++) {
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featureRecord = allFeatures[featIndexes[i]];
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if (featureRecord.tag === feature) {
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return featureRecord.feature;
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}
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}
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if (create) {
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const index = allFeatures.length;
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// Automatic ordering of features would require to shift feature indexes in the script list.
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check.assert(
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index === 0 || feature >= allFeatures[index - 1].tag,
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'Features must be added in alphabetical order.'
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);
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featureRecord = {
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tag: feature,
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feature: { params: 0, lookupListIndexes: [] },
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};
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allFeatures.push(featureRecord);
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featIndexes.push(index);
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return featureRecord.feature;
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}
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}
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},
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/**
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* Get the lookup tables of a given type for a script/language/feature.
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* @instance
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* @param {string} [script='DFLT']
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* @param {string} [language='dlft']
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* @param {string} feature - 4-letter feature code
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* @param {number} lookupType - 1 to 9
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* @param {boolean} create - forces the creation of the lookup table if it doesn't exist, with no subtables.
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* @return {Object[]}
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*/
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getLookupTables: function (script, language, feature, lookupType, create) {
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const featureTable = this.getFeatureTable(
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script,
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language,
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feature,
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create
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);
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const tables = [];
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if (featureTable) {
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let lookupTable;
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const lookupListIndexes = featureTable.lookupListIndexes;
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const allLookups = this.font.tables[this.tableName].lookups;
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// lookupListIndexes are in no particular order, so use naive search.
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for (let i = 0; i < lookupListIndexes.length; i++) {
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lookupTable = allLookups[lookupListIndexes[i]];
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if (lookupTable.lookupType === lookupType) {
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tables.push(lookupTable);
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}
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}
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if (tables.length === 0 && create) {
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lookupTable = {
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lookupType: lookupType,
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lookupFlag: 0,
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subtables: [],
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markFilteringSet: undefined,
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};
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const index = allLookups.length;
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allLookups.push(lookupTable);
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lookupListIndexes.push(index);
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return [lookupTable];
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}
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}
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return tables;
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},
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/**
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* Find a glyph in a class definition table
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* https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#class-definition-table
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* @param {object} classDefTable - an OpenType Layout class definition table
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* @param {number} glyphIndex - the index of the glyph to find
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* @returns {number} -1 if not found
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*/
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getGlyphClass: function (classDefTable, glyphIndex) {
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switch (classDefTable.format) {
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case 1:
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if (
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classDefTable.startGlyph <= glyphIndex &&
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glyphIndex <
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classDefTable.startGlyph + classDefTable.classes.length
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) {
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return classDefTable.classes[
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glyphIndex - classDefTable.startGlyph
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];
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}
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return 0;
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case 2:
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const range = searchRange(classDefTable.ranges, glyphIndex);
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return range ? range.classId : 0;
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}
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},
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/**
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* Find a glyph in a coverage table
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* https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#coverage-table
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* @param {object} coverageTable - an OpenType Layout coverage table
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* @param {number} glyphIndex - the index of the glyph to find
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* @returns {number} -1 if not found
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*/
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getCoverageIndex: function (coverageTable, glyphIndex) {
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switch (coverageTable.format) {
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case 1:
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const index = binSearch(coverageTable.glyphs, glyphIndex);
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return index >= 0 ? index : -1;
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case 2:
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const range = searchRange(coverageTable.ranges, glyphIndex);
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return range ? range.index + glyphIndex - range.start : -1;
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}
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},
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/**
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* Returns the list of glyph indexes of a coverage table.
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* Format 1: the list is stored raw
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* Format 2: compact list as range records.
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* @instance
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* @param {Object} coverageTable
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* @return {Array}
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*/
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expandCoverage: function (coverageTable) {
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if (coverageTable.format === 1) {
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return coverageTable.glyphs;
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} else {
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const glyphs = [];
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const ranges = coverageTable.ranges;
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for (let i = 0; i < ranges.length; i++) {
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const range = ranges[i];
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const start = range.start;
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const end = range.end;
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for (let j = start; j <= end; j++) {
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glyphs.push(j);
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}
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}
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return glyphs;
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}
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},
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};
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export default Layout;
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