Further cleanup and optimize spiro expansion.

support/utils.js

@@ -0,0 +1,49 @@
+"use strict";
+
+function mix(a, b, p) {
+	return a + (b - a) * p;
+}
+function ratio(l, r, m) {
+	return l === r ? 0 : (m - l) / (r - l);
+}
+function barmixL(l, r, b, p) {
+	return l > r ? barmixL(r, l, b, p) : l + b + p * (r - l - b * 3);
+}
+function barmixM(l, r, b, p) {
+	return barmixL(l, r, b, p) + b / 2;
+}
+function barMixR(l, r, b, p) {
+	return barMixR(l, r, b, p) + b;
+}
+function linreg(x0, y0, x1, y1, x) {
+	return y0 + ((x - x0) * (y1 - y0)) / (x1 - x0);
+}
+function clamp(l, h, x) {
+	return x < l ? l : x > h ? h : x;
+}
+function fallback(...args) {
+	for (const item of args) if (item !== void 0) return item;
+	return void 0;
+}
+function bez2(a, b, c, t) {
+	return (1 - t) * (1 - t) * a + 2 * (1 - t) * t * b + t * t * c;
+}
+function bez3(a, b, c, d, t) {
+	return (
+		(1 - t) * (1 - t) * (1 - t) * a +
+		3 * (1 - t) * (1 - t) * t * b +
+		3 * t * t * (1 - t) * c +
+		t * t * t * d
+	);
+}
+
+exports.mix = mix;
+exports.ratio = ratio;
+exports.barmixL = barmixL;
+exports.barmixM = barmixM;
+exports.barmixR = barMixR;
+exports.linreg = linreg;
+exports.clamp = clamp;
+exports.fallback = fallback;
+exports.bez2 = bez2;
+exports.bez3 = bez3;