Move font building related files to font-src

font-src/support/spiro-expand.js

@@ -0,0 +1,132 @@
+const Transform = require("./transform");
+const { linreg } = require("./utils");
+
+module.exports = class SpiroExpansionContext {
+	constructor() {
+		this.gizmo = Transform.Id();
+		this.controlKnots = [];
+		this.defaultD1 = 0;
+		this.defaultD2 = 0;
+	}
+	beginShape() {}
+	endShape() {}
+	moveTo(x, y, unimportant) {
+		if (unimportant) return;
+		this.controlKnots.push({
+			type: "g4",
+			d1: this.defaultD1,
+			d2: this.defaultD2,
+			...this.gizmo.apply({ x, y })
+		});
+	}
+	arcTo(arc, x, y) {
+		const k0 = this.controlKnots[this.controlKnots.length - 1];
+		if (!k0) throw new Error("Unreachable: lineTo called before moveTo");
+		if (k0.normalAngle == null) {
+			const tfDerive0 = this.gizmo.applyOffset({ x: arc.deriveX0, y: arc.deriveY0 });
+			k0.normalAngle = Math.PI / 2 + Math.atan2(tfDerive0.y, tfDerive0.x);
+		}
+		{
+			const tfDerive1 = this.gizmo.applyOffset({ x: arc.deriveX1, y: arc.deriveY1 });
+			this.controlKnots.push({
+				type: "g4",
+				d1: k0.d1,
+				d2: k0.d2,
+				...this.gizmo.apply({ x, y }),
+				normalAngle: Math.PI / 2 + Math.atan2(tfDerive1.y, tfDerive1.x)
+			});
+		}
+	}
+	setWidth(l, r) {
+		const k0 = this.controlKnots[this.controlKnots.length - 1];
+		if (k0) {
+			(k0.d1 = l), (k0.d2 = r);
+		} else {
+			(this.defaultD1 = l), (this.defaultD2 = r);
+		}
+	}
+	headsTo(direction) {
+		const k0 = this.controlKnots[this.controlKnots.length - 1];
+		if (k0) k0.proposedNormal = direction;
+	}
+	setType(type) {
+		const k0 = this.controlKnots[this.controlKnots.length - 1];
+		if (k0) k0.type = type;
+	}
+	expand(contrast) {
+		if (contrast == null) contrast = 1 / 0.9;
+		const lhs = [],
+			rhs = [];
+
+		// Create important knots
+		for (let j = 0; j < this.controlKnots.length; j++) {
+			const knot = this.controlKnots[j];
+			if (knot.unimportant) continue;
+
+			let dx = 0,
+				dy = 0;
+			if (knot.proposedNormal) {
+				dx = knot.proposedNormal.x - normalX(knot.normalAngle, contrast);
+				dy = knot.proposedNormal.y - normalY(knot.normalAngle, contrast);
+			}
+			lhs[j] = {
+				type: knot.type,
+				x: knot.x + knot.d1 * (dx + normalX(knot.normalAngle, contrast)),
+				y: knot.y + knot.d1 * (dy + normalY(knot.normalAngle, contrast))
+			};
+			rhs[j] = {
+				type: reverseKnotType(knot.type),
+				x: knot.x - knot.d2 * (dx + normalX(knot.normalAngle, contrast)),
+				y: knot.y - knot.d2 * (dy + normalY(knot.normalAngle, contrast))
+			};
+		}
+		this.interpolateUnimportantKnots(lhs, rhs);
+		return { lhs, rhs };
+	}
+	interpolateUnimportantKnots(lhs, rhs) {
+		for (let j = 0; j < this.controlKnots.length; j++) {
+			const knot = this.controlKnots[j];
+			if (!knot.unimportant) continue;
+			let jBefore, jAfter;
+			for (jBefore = j - 1; this.controlKnots[jBefore].unimportant; jBefore--);
+			for (jAfter = j + 1; this.controlKnots[jAfter].unimportant; jAfter++);
+
+			const knotBefore = this.gizmo.unapply(this.controlKnots[jBefore]),
+				knotAfter = this.gizmo.unapply(this.controlKnots[jAfter]),
+				ref = this.gizmo.unapply(knot),
+				lhsBefore = this.gizmo.unapply(lhs[jBefore]),
+				lhsAfter = this.gizmo.unapply(lhs[jAfter]),
+				rhsBefore = this.gizmo.unapply(rhs[jBefore]),
+				rhsAfter = this.gizmo.unapply(rhs[jAfter]);
+
+			lhs[j] = {
+				type: knot.type,
+				...this.gizmo.apply({
+					x: linreg(knotBefore.x, lhsBefore.x, knotAfter.x, lhsAfter.x, ref.x),
+					y: linreg(knotBefore.y, lhsBefore.y, knotAfter.y, lhsAfter.y, ref.y)
+				})
+			};
+			rhs[j] = {
+				type: reverseKnotType(knot.type),
+				...this.gizmo.apply({
+					x: linreg(knotBefore.x, rhsBefore.x, knotAfter.x, rhsAfter.x, ref.x),
+					y: linreg(knotBefore.y, rhsBefore.y, knotAfter.y, rhsAfter.y, ref.y)
+				})
+			};
+		}
+	}
+};
+function zeroes(n) {
+	let a = new Array(n);
+	for (let i = 0; i < n; ++i) a[i] = 0;
+	return a;
+}
+function normalX(angle, contrast) {
+	return Math.cos(angle) * contrast;
+}
+function normalY(angle) {
+	return Math.sin(angle);
+}
+function reverseKnotType(ty) {
+	return ty === "left" ? "right" : ty === "right" ? "left" : ty;
+}