More outline cleanup changes (#1562)

changes/19.0.2.md

@@ -6,4 +6,4 @@
   - MODIFIER LETTER CYRILLIC SMALL STRAIGHT U WITH STROKE (`U+1E06D`).
   - COMBINING CYRILLIC SMALL LETTER BYELORUSSIAN-UKRAINIAN I (`U+1E08F`).
 * Add variants for partial differential symbol (#1503).
-* Prevent pathological geometry produced in phonetic ligatures (#1565, #1566).
+* Prevent pathological geometry produced in phonetic ligatures (#1562, #1565, #1566).

font-src/gen/caching/index.mjs

@@ -3,7 +3,7 @@ import zlib from "zlib";
 
 import { encode, decode } from "@msgpack/msgpack";
 
-const Edition = 23;
+const Edition = 24;
 const MAX_AGE = 16;
 class GfEntry {
 	constructor(age, value) {

font-src/gen/finalize/glyphs.mjs

@@ -4,6 +4,7 @@ import * as CurveUtil from "../../support/geometry/curve-util.mjs";
 import * as Geom from "../../support/geometry/index.mjs";
 import { Point } from "../../support/geometry/point.mjs";
 import { Transform } from "../../support/geometry/transform.mjs";
+import { mix } from "../../support/utils.mjs";
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 
@@ -144,8 +145,12 @@ class QuadifySink {
 		if (this.lastContour.length > 2) {
 			let c = this.lastContour;
 			c = this.alignHVKnots(c);
+			c = this.dropDuplicateFirstLast(c);
+			c = this.cleanupOccurrentKnots2(c);
+			c = this.cleanupOccurrentKnots1(c);
+			c = this.removeColinearArc(c);
+			c = this.removeColinearCorners(c);
 			c = this.cleanupOccurrentKnots1(c);
-			c = this.removeColinearKnots(c);
 			if (c.length > 2) this.contours.push(c);
 		}
 		this.lastContour = [];
@@ -170,25 +175,43 @@ class QuadifySink {
 		const c = c0.slice(0);
 		const alignX = new CoordinateAligner(c, GetX, SetX);
 		const alignY = new CoordinateAligner(c, GetY, SetY);
+
 		for (let i = 0; i < c.length; i++) {
-			if (c[i].type === Point.Type.Corner) {
-				alignX.tryAlign(i, (i + 1) % c.length);
-				alignY.tryAlign(i, (i + 1) % c.length);
-			}
-		}
-		for (let i = 0; i < c.length; i++) {
-			const zCurr = c[i],
-				zNext = c[(i + 1) % c.length];
+			const iNext = (i + 1) % c.length,
+				zCurr = c[i],
+				zNext = c[iNext];
 			if (zCurr.type === Point.Type.Quadratic && zNext.type === Point.Type.Corner) {
-				alignX.tryAlign(i, (i + 1) % c.length);
-				alignY.tryAlign(i, (i + 1) % c.length);
+				alignX.tryAlign(i, iNext);
+				alignY.tryAlign(i, iNext);
+			} else {
+				alignX.tryAlign(iNext, i);
+				alignY.tryAlign(iNext, i);
 			}
 		}
+
 		alignX.apply();
 		alignY.apply();
 		return c;
 	}
 
+	// Drop the duplicate point (first-last)
+	dropDuplicateFirstLast(c) {
+		while (c.length > 1) {
+			const first = c[0],
+				last = c[c.length - 1];
+			if (
+				first.type === Point.Type.Corner &&
+				last.type === Point.Type.Corner &&
+				isOccurrent(first, last)
+			) {
+				c.pop();
+			} else {
+				break;
+			}
+		}
+		return c;
+	}
+
 	// Occurrent cleanup -- corner-corner
 	cleanupOccurrentKnots1(c0) {
 		let drops = [];
@@ -198,6 +221,7 @@ class QuadifySink {
 			const pre = c0[i],
 				post = c0[iPost];
 			if (
+				iPost > 0 &&
 				pre.type === Point.Type.Corner &&
 				post.type === Point.Type.Corner &&
 				isOccurrent(pre, post)
@@ -209,7 +233,43 @@ class QuadifySink {
 		return dropBy(c0, drops);
 	}
 
-	removeColinearKnots(c0) {
+	// Occurrent cleanup -- off points
+	// This function actually **INSERTS** points for occurrent off knots.
+	cleanupOccurrentKnots2(c0) {
+		let insertAfter = [];
+		for (let i = 0; i < c0.length; i++) insertAfter[i] = false;
+		for (let i = 0; i < c0.length; i++) {
+			const cur = c0[i];
+			if (cur.type !== Point.Type.Quadratic) continue;
+
+			const iPre = (i - 1 + c0.length) % c0.length;
+			const iPost = (i + 1) % c0.length;
+			const pre = c0[iPre];
+			const post = c0[iPost];
+
+			if (isOccurrent(pre, cur) && post.type === Point.Type.Quadratic) {
+				insertAfter[i] = true;
+			}
+			if (isOccurrent(cur, post) && pre.type === Point.Type.Quadratic) {
+				insertAfter[iPre] = true;
+			}
+		}
+
+		let c1 = [];
+		for (let i = 0; i < c0.length; i++) {
+			const cur = c0[i];
+			c1.push(cur);
+			if (insertAfter[i]) {
+				const iPost = (i + 1) % c0.length;
+				const post = c0[iPost];
+				c1.push(Point.mix(Point.Type.Corner, cur, post, 0.5));
+			}
+		}
+
+		return c1;
+	}
+
+	removeColinearCorners(c0) {
 		const c = c0.slice(0);
 		let lengthBefore = c.length,
 			lengthAfter = c.length;
@@ -220,22 +280,47 @@ class QuadifySink {
 				const zPrev = c[(i - 1 + c.length) % c.length],
 					zCurr = c[i],
 					zNext = c[(i + 1) % c.length];
-				if (zPrev.type === Point.Type.Corner && zNext.type === Point.Type.Corner) {
-					if (aligned(zPrev.x, zCurr.x, zNext.x) && between(zPrev.y, zCurr.y, zNext.y))
-						shouldRemove[i] = true;
-					if (aligned(zPrev.y, zCurr.y, zNext.y) && between(zPrev.x, zCurr.x, zNext.x))
+				if (
+					zPrev.type === Point.Type.Corner &&
+					zNext.type === Point.Type.Corner &&
+					pointsColinear(zPrev, zCurr, zNext)
+				) {
 					shouldRemove[i] = true;
 				}
 			}
-			let n = 0;
-			for (let i = 0; i < c.length; i++) {
-				if (!shouldRemove[i]) c[n++] = c[i];
-			}
-			c.length = n;
+
+			dropBy(c, shouldRemove);
 			lengthAfter = c.length;
 		} while (lengthAfter < lengthBefore);
 		return c;
 	}
+
+	removeColinearArc(c) {
+		if (c[0].type !== Point.Type.Corner) throw new Error("Unreachable");
+
+		let front = 0,
+			shouldRemove = [],
+			middlePoints = [];
+		for (let rear = 1; rear <= c.length; rear++) {
+			let zFront = c[front],
+				zRear = c[rear % c.length];
+			if (zRear.type === Point.Type.Corner) {
+				let allColinear = true;
+				for (const z of middlePoints) {
+					if (!pointsColinear(zFront, z, zRear)) allColinear = false;
+				}
+
+				if (allColinear) for (let i = front + 1; i < rear; i++) shouldRemove[i] = true;
+
+				front = rear;
+				middlePoints.length = 0;
+			} else {
+				middlePoints.push(zRear);
+			}
+		}
+
+		return dropBy(c, shouldRemove);
+	}
 }
 
 // Disjoint set for coordinate alignment
@@ -297,10 +382,18 @@ function aligned(a, b, c) {
 function between(a, b, c) {
 	return (a <= b && b <= c) || (a >= b && b >= c);
 }
+function pointsColinear(zPrev, zCurr, zNext) {
+	if (aligned(zPrev.x, zCurr.x, zNext.x) && between(zPrev.y, zCurr.y, zNext.y)) return true;
+	if (aligned(zPrev.y, zCurr.y, zNext.y) && between(zPrev.x, zCurr.x, zNext.x)) return true;
+	return false;
+}
 
 // Dropping helper
-function dropBy(a, d) {
-	let r = [];
-	for (let i = 0; i < a.length; i++) if (!d[i]) r.push(a[i]);
-	return r;
+function dropBy(c, shouldRemove) {
+	let n = 0;
+	for (let i = 0; i < c.length; i++) {
+		if (!shouldRemove[i]) c[n++] = c[i];
+	}
+	c.length = n;
+	return c;
 }

font-src/support/geometry/point.mjs

@@ -1,3 +1,5 @@
+import { mix } from "../utils.mjs";
+
 export class Point {
 	constructor(type, x, y) {
 		this.type = type;
@@ -57,6 +59,9 @@ export class Point {
 	static translated(z, dx, dy) {
 		return new Point(z.type, z.x + dx || 0, z.y + dy || 0);
 	}
+	static mix(type, a, b, p) {
+		return new Point(type, mix(a.x, b.x, p), mix(a.y, b.y, p));
+	}
 }
 Point.Type = {
 	Corner: 0,