font-ligatures
Version:
Find ligature replacements for any system font
66 lines • 3.22 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
const merge_1 = require("../merge");
const coverage_1 = require("./coverage");
const classDef_1 = require("./classDef");
const helper_1 = require("./helper");
/**
* Build lookup tree for GSUB lookup table 6, format 2.
* https://docs.microsoft.com/en-us/typography/opentype/spec/gsub#62-chaining-context-substitution-format-2-class-based-glyph-contexts
*
* @param table JSON representation of the table
* @param lookups List of lookup tables
* @param tableIndex Index of this table in the overall lookup
*/
function buildTree(table, lookups, tableIndex) {
const results = [];
const firstGlyphs = coverage_1.listGlyphsByIndex(table.coverage);
for (const { glyphId } of firstGlyphs) {
const firstInputClass = classDef_1.default(table.inputClassDef, glyphId);
for (const [glyphId, inputClass] of firstInputClass.entries()) {
// istanbul ignore next - invalid font
if (inputClass === null) {
continue;
}
const classSet = table.chainClassSet[inputClass];
// If the class set is null there's nothing to do with this table.
if (!classSet) {
continue;
}
for (const [subIndex, subTable] of classSet.entries()) {
const result = {
individual: {},
range: []
};
let currentEntries = helper_1.getInputTree(result, subTable.lookupRecords, lookups, 0, glyphId).map(({ entry, substitution }) => ({ entry, substitutions: [substitution] }));
for (const [index, classNum] of subTable.input.entries()) {
currentEntries = helper_1.processInputPosition(classDef_1.listClassGlyphs(table.inputClassDef, classNum), index + 1, currentEntries, subTable.lookupRecords, lookups);
}
for (const classNum of subTable.lookahead) {
currentEntries = helper_1.processLookaheadPosition(classDef_1.listClassGlyphs(table.lookaheadClassDef, classNum), currentEntries);
}
for (const classNum of subTable.backtrack) {
currentEntries = helper_1.processBacktrackPosition(classDef_1.listClassGlyphs(table.backtrackClassDef, classNum), currentEntries);
}
// When we get to the end, all of the entries we've accumulated
// should have a lookup defined
for (const { entry, substitutions } of currentEntries) {
entry.lookup = {
substitutions,
index: tableIndex,
subIndex,
length: subTable.input.length + 1,
contextRange: [
-1 * subTable.backtrack.length,
1 + subTable.input.length + subTable.lookahead.length
]
};
}
results.push(result);
}
}
}
return merge_1.default(results);
}
exports.default = buildTree;
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