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https://github.com/Sendouc/sendou.ink.git
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62 lines
2.2 KiB
TypeScript
62 lines
2.2 KiB
TypeScript
/** biome-ignore-all lint/suspicious/noConsole: CLI script output */
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/**
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* Minimal OpenType cmap reader: which codepoints does a font actually map?
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*
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* @napi-rs/canvas silently falls back to a system font for characters the
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* requested family lacks (the Blitz cuts carry Latin/Greek/Cyrillic/kana
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* but no kanji, hangul or hanzi), which would bake wrong-font glyphs into
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* the atlases. The builder filters every charset through this before
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* rendering. Supports the two subtable formats the game fonts use:
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* format 4 (BMP segments) and format 12 (grouped full-range).
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*/
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import { readFileSync } from "node:fs";
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export function readFontCoverage(path: string): (codepoint: number) => boolean {
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const buf = readFileSync(path);
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const numTables = buf.readUInt16BE(4);
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let cmapOffset = -1;
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for (let i = 0; i < numTables; i++) {
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const rec = 12 + i * 16;
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if (buf.toString("latin1", rec, rec + 4) === "cmap") {
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cmapOffset = buf.readUInt32BE(rec + 8);
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break;
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}
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}
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if (cmapOffset < 0) throw new Error(`${path}: no cmap table`);
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// prefer a full-repertoire format-12 subtable, else the BMP format 4
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const encodingCount = buf.readUInt16BE(cmapOffset + 2);
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let best = -1;
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let bestFormat = -1;
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for (let i = 0; i < encodingCount; i++) {
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const rec = cmapOffset + 4 + i * 8;
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const subtable = cmapOffset + buf.readUInt32BE(rec + 4);
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const format = buf.readUInt16BE(subtable);
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if (format === 12 || (format === 4 && bestFormat !== 12)) {
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best = subtable;
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bestFormat = format;
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}
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}
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if (best < 0) throw new Error(`${path}: no format 4/12 cmap subtable`);
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const ranges: [number, number][] = [];
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if (bestFormat === 12) {
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const nGroups = buf.readUInt32BE(best + 12);
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for (let g = 0; g < nGroups; g++) {
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const rec = best + 16 + g * 12;
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ranges.push([buf.readUInt32BE(rec), buf.readUInt32BE(rec + 4)]);
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}
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} else {
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const segCount = buf.readUInt16BE(best + 6) / 2;
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const endCodes = best + 14;
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const startCodes = endCodes + segCount * 2 + 2;
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for (let s = 0; s < segCount; s++) {
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const start = buf.readUInt16BE(startCodes + s * 2);
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const end = buf.readUInt16BE(endCodes + s * 2);
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if (start !== 0xffff) ranges.push([start, end]);
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}
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}
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return (codepoint) =>
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ranges.some(([start, end]) => codepoint >= start && codepoint <= end);
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}
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