Generate TTFAutohint control files for better glyph display for variant glyphs (#1963).

font-src/gen/ttfa-controls/index.mjs

@@ -0,0 +1,56 @@
+import ttfaRanges from "../../generated/ttfa-ranges.mjs";
+import * as Gr from "../../support/gr.mjs";
+import { ArrayUtil } from "../../support/utils.mjs";
+
+export async function generateTtfaControls(gsOrig, gs) {
+	let ttfaControls = [];
+
+	for (const alignment of ttfaRanges) {
+		ttfaControls.push(generateTTFAAlignments(alignment, gsOrig, gs));
+	}
+
+	return ttfaControls;
+}
+
+function generateTTFAAlignments(alignment, gsOrig, gsTtf) {
+	let collectedGlyphs = new Map();
+	for (const [lo, hi] of alignment.ranges) {
+		for (let lch = lo; lch <= hi; lch++) {
+			const go = gsOrig.queryByUnicode(lch);
+			if (!go) continue;
+			const gd = gsTtf.queryBySourceGlyph(go);
+			if (!gd) continue;
+			collectedGlyphs.set(go, gd);
+		}
+	}
+
+	for (;;) {
+		let sizeBefore = collectedGlyphs.size;
+
+		for (const [go, gd] of collectedGlyphs) {
+			const cvs = Gr.AnyCv.query(go);
+			for (const gr of cvs) {
+				const gnLinked = gr.get(go);
+				if (!gnLinked) continue;
+				const goLinked = gsOrig.queryByName(gnLinked);
+				if (!goLinked) continue;
+				const gdLinked = gsTtf.queryBySourceGlyph(goLinked);
+				if (!gdLinked) continue;
+				collectedGlyphs.set(goLinked, gdLinked);
+			}
+		}
+
+		let sizeAfter = collectedGlyphs.size;
+		if (sizeAfter <= sizeBefore) break;
+	}
+
+	const gOrd = gsTtf.decideOrder();
+	const glyphIndices = Array.from(collectedGlyphs.values()).map(gd => gOrd.reverse(gd));
+	const glyphIndicesRangesStr = ArrayUtil.toRanges(glyphIndices)
+		.map(([lo, hi]) => (lo === hi ? `${lo}` : `${lo}-${hi}`))
+		.join(", ");
+
+	const styleAdjustLine = `${alignment.scriptTag} ${alignment.featureTag} @ ${glyphIndicesRangesStr}`;
+
+	return styleAdjustLine;
+}