font-ligatures
Version:
Find ligature replacements for any system font
48 lines • 2.3 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
const coverage_1 = require("./coverage");
const helper_1 = require("./helper");
/**
* Build lookup tree for GSUB lookup table 6, format 3.
* https://docs.microsoft.com/en-us/typography/opentype/spec/gsub#63-chaining-context-substitution-format-3-coverage-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 result = {
individual: {},
range: []
};
const firstGlyphs = coverage_1.listGlyphsByIndex(table.inputCoverage[0]);
for (const { glyphId } of firstGlyphs) {
let currentEntries = helper_1.getInputTree(result, table.lookupRecords, lookups, 0, glyphId).map(({ entry, substitution }) => ({ entry, substitutions: [substitution] }));
for (const [index, coverage] of table.inputCoverage.slice(1).entries()) {
currentEntries = helper_1.processInputPosition(coverage_1.listGlyphsByIndex(coverage).map(glyph => glyph.glyphId), index + 1, currentEntries, table.lookupRecords, lookups);
}
for (const coverage of table.lookaheadCoverage) {
currentEntries = helper_1.processLookaheadPosition(coverage_1.listGlyphsByIndex(coverage).map(glyph => glyph.glyphId), currentEntries);
}
for (const coverage of table.backtrackCoverage) {
currentEntries = helper_1.processBacktrackPosition(coverage_1.listGlyphsByIndex(coverage).map(glyph => glyph.glyphId), 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: 0,
length: table.inputCoverage.length,
contextRange: [
-1 * table.backtrackCoverage.length,
table.inputCoverage.length + table.lookaheadCoverage.length
]
};
}
}
return result;
}
exports.default = buildTree;
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