lib-font/src/opentype/tables/createTable.js

A JS based OpenType font inspector

// Step 1: set up a namespace for all our table classes.
const tableClasses = {};
let tableClassesLoaded = false;

// Step 2: load all the table classes. While the imports
// all resolve asynchronously, Promise.all won't "exit"
// until every class definition has been loaded.
Promise.all([
  // opentype tables
  import("./simple/cmap.js"),
  import("./simple/head.js"),
  import("./simple/hhea.js"),
  import("./simple/hmtx.js"),
  import("./simple/maxp.js"),
  import("./simple/name.js"),
  import("./simple/OS2.js"),
  import("./simple/post.js"),

  // opentype tables that rely on the "common layout tables" data structures
  import("./advanced/BASE.js"),
  import("./advanced/GDEF.js"),
  import("./advanced/GSUB.js"),
  import("./advanced/GPOS.js"),

  // SVG tables... err... table
  import("./simple/SVG.js"),

  // Variable fonts
  import("./simple/variation/fvar.js"),

  // TTF tables
  import("./simple/ttf/cvt.js"),
  import("./simple/ttf/fpgm.js"),
  import("./simple/ttf/gasp.js"),
  import("./simple/ttf/glyf.js"),
  import("./simple/ttf/loca.js"),
  import("./simple/ttf/prep.js"),

  // CFF
  import("./simple/cff/CFF.js"),
  import("./simple/cff/CFF2.js"),
  import("./simple/cff/VORG.js"),

  // bitmap
  import("./simple/bitmap/EBLC.js"),
  import("./simple/bitmap/EBDT.js"),
  import("./simple/bitmap/EBSC.js"),
  import("./simple/bitmap/CBLC.js"),
  import("./simple/bitmap/CBDT.js"),
  import("./simple/bitmap/sbix.js"),

  // color
  import("./simple/color/COLR.js"),
  import("./simple/color/CPAL.js"),

  // "other" tables
  import("./simple/other/DSIG.js"),
  import("./simple/other/hdmx.js"),
  import("./simple/other/kern.js"),
  import("./simple/other/LTSH.js"),
  import("./simple/other/MERG.js"),
  import("./simple/other/meta.js"),
  import("./simple/other/PCLT.js"),
  import("./simple/other/VDMX.js"),
  import("./simple/other/vhea.js"),
  import("./simple/other/vmtx.js"),
])

  // Step 3: rebind all the class imports so that
  // we can fetch constructors given table names.
  .then((data) => {
    data.forEach((e) => {
      let name = Object.keys(e)[0];
      tableClasses[name] = e[name];
    });
    tableClassesLoaded = true;
  });

/**
 * Step 4: set up a table factory that can build tables given a name tag.
 * @param {*} tables the object containing actual table instances.
 * @param {*} dict an object of the form: { tag: "string", offset: <number>, [length: <number>]}
 * @param {*} dataview a DataView object over an ArrayBuffer of Uint8Array
 */
function createTable(tables, dict, dataview) {
  let name = dict.tag.replace(/[^\w\d]/g, ``);
  let Type = tableClasses[name];
  if (Type) return new Type(dict, dataview, tables);
  console.warn(
    `lib-font has no definition for ${name}. The table was skipped.`
  );
  return {};
}

function loadTableClasses() {
  let count = 0;
  function checkLoaded(resolve, reject) {
    if (!tableClassesLoaded) {
      if (count > 10) {
        return reject(new Error(`loading took too long`));
      }
      count++;
      return setTimeout(() => checkLoaded(resolve), 250);
    }
    resolve(createTable);
  }
  return new Promise((resolve, reject) => checkLoaded(resolve));
}

export { loadTableClasses };