Move font building related files to font-src

font-src/support/monotonic-interpolate.js

@@ -0,0 +1,114 @@
+"use strict";
+
+module.exports = function (xs, ys) {
+	let i,
+		length = xs.length;
+
+	// Deal with length issues
+	if (length != ys.length) {
+		throw "Need an equal count of xs and ys.";
+	}
+	if (length === 0) {
+		return function () {
+			return 0;
+		};
+	}
+	if (length === 1) {
+		// Impl: Precomputing the result prevents problems if ys is mutated later and allows garbage collection of ys
+		// Impl: Unary plus properly converts values to numbers
+		let result = +ys[0];
+		return function () {
+			return result;
+		};
+	}
+
+	// Rearrange xs and ys so that xs is sorted
+	let indexes = [];
+	for (i = 0; i < length; i++) {
+		indexes.push(i);
+	}
+	indexes.sort(function (a, b) {
+		return xs[a] < xs[b] ? -1 : 1;
+	});
+	let oldXs = xs,
+		oldYs = ys;
+	// Impl: Creating new arrays also prevents problems if the input arrays are mutated later
+	xs = [];
+	ys = [];
+	// Impl: Unary plus properly converts values to numbers
+	for (i = 0; i < length; i++) {
+		xs.push(+oldXs[indexes[i]]);
+		ys.push(+oldYs[indexes[i]]);
+	}
+
+	// Get consecutive differences and slopes
+	let dys = [],
+		dxs = [],
+		ms = [];
+	for (i = 0; i < length - 1; i++) {
+		const dx = xs[i + 1] - xs[i],
+			dy = ys[i + 1] - ys[i];
+		dxs.push(dx);
+		dys.push(dy);
+		ms.push(dy / dx);
+	}
+
+	// Get degree-1 coefficients
+	let c1s = [ms[0]];
+	for (i = 0; i < dxs.length - 1; i++) {
+		const m = ms[i],
+			mNext = ms[i + 1];
+		if (m * mNext <= 0) {
+			c1s.push(0);
+		} else {
+			const dx = dxs[i],
+				dxNext = dxs[i + 1],
+				common = dx + dxNext;
+			c1s.push((3 * common) / ((common + dxNext) / m + (common + dx) / mNext));
+		}
+	}
+	c1s.push(ms[ms.length - 1]);
+
+	// Get degree-2 and degree-3 coefficients
+	let c2s = [],
+		c3s = [];
+	for (i = 0; i < c1s.length - 1; i++) {
+		const c1 = c1s[i],
+			m = ms[i],
+			invDx = 1 / dxs[i],
+			common = c1 + c1s[i + 1] - m - m;
+		c2s.push((m - c1 - common) * invDx);
+		c3s.push(common * invDx * invDx);
+	}
+
+	// Return interpolant function
+	return function (x) {
+		// The rightmost point in the dataset should give an exact result
+		let i = xs.length - 1;
+		if (x == xs[i]) {
+			return ys[i];
+		}
+
+		// Search for the interval x is in, returning the corresponding y if x is one of the original xs
+		let low = 0,
+			mid,
+			high = c3s.length - 1;
+		while (low <= high) {
+			mid = Math.floor(0.5 * (low + high));
+			let xHere = xs[mid];
+			if (xHere < x) {
+				low = mid + 1;
+			} else if (xHere > x) {
+				high = mid - 1;
+			} else {
+				return ys[mid];
+			}
+		}
+		i = Math.max(0, high);
+
+		// Interpolate
+		let diff = x - xs[i],
+			diffSq = diff * diff;
+		return ys[i] + c1s[i] * diff + c2s[i] * diffSq + c3s[i] * diff * diffSq;
+	};
+};