Type six, format two

[RoelN]

An attempt to kickstart type 6, format 2 parsing by looking at what's missing and peeking from existing code on how to solve this :P

Currently simply attempting to get the info we see in the TTX dump here: #153 (comment)

Code to test Bangers with this PR (so far), our test font with confirmed 6.2 lookup. EDIT: or use the gsub.test.js test!

import fs from "node:fs";
import { Font } from "./lib-font.js";

const font = new Font("Bangers");
const fontBuffer = await fs.promises.readFile("./fonts/Bangers-Regular.ttf");
font.fromDataBuffer(Uint8Array.from(fontBuffer).buffer, "Bangers-Regular.ttf");

font.onload = () => {
  const { GSUB, post } = font.opentype.tables;

  // Get Bangers' 6.2 lookup
  const lookup = GSUB.getLookup(3);
  const subtable = lookup.getSubTable(0);

  // Get defenition, use `getInputClassDef`, `getLookaheadClassDef` or `getLookaheadClassDef`
  const inputClassDef = subtable.getInputClassDef();

  // Show what chars we got
  for (const record of inputClassDef.classRangeRecords) {
    for (let gid = record.startGlyphID; gid <= record.endGlyphID; gid++) {
      const char = post.getGlyphName(gid);
      console.log(char);
    }
  }
};

[RoelN]

@Pomax This was basically copied of off existing code, to get to the Bangers chars as detailed in #153 I would love a pair of extra eyes on this, as even though I seem to be getting the data I want, I might be oversimplifying. I'll be testing this tomorrow with more fonts, and seeing if and how this works together with Wakamai Fondue.

[RoelN]

I tested some more fonts from the Google Fonts repo, these all seem to be working nicely! Pretty thrilled this seems to be all there is to it. But waiting for you to confirm, @Pomax!