lib-font/src/opentype/tables/simple/ttf/loca.js

A JS based OpenType font inspector

import { SimpleTable } from "../../simple-table.js";
import lazy from "../../../../lazy.js";

/**
 * The OpenType `loca` table.
 *
 * See https://docs.microsoft.com/en-us/typography/opentype/spec/loca
 */
class loca extends SimpleTable {
  constructor(dict, dataview, tables) {
    const { p } = super(dict, dataview);

    const n = tables.maxp.numGlyphs + 1; // "plus one" because the offset list needs one extra element to determine the block length for the last supported glyph.

    if (tables.head.indexToLocFormat === 0) {
      this.x2 = true;
      lazy(this, `offsets`, () => [...new Array(n)].map((_) => p.Offset16));
    } else {
      lazy(this, `offsets`, () => [...new Array(n)].map((_) => p.Offset32));
    }
  }

  getGlyphDataOffsetAndLength(glyphID) {
    let offset = this.offsets[glyphID] * this.x2 ? 2 : 1;
    let nextOffset = this.offsets[glyphID + 1] * this.x2 ? 2 : 1;
    return { offset, length: nextOffset - offset };
  }
}

export { loca };