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Use disjoint set to further avoid rounding errors (#1100)

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This commit is contained in:
be5invis 2021-06-05 19:14:19 -07:00
parent 1babc986cd
commit 4bf94aba27
2 changed files with 57 additions and 9 deletions
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64
font-src/gen/finalize/glyphs.js
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@ -158,22 +158,24 @@ class FairizedShapeSink {
// Contour cleaning code
alignHVKnots(c0) {
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++) {
const zPrev = c[i],
zCurr = c[(i + 1) % c.length];
if (zPrev.type === Point.Type.Corner) {
if (occurrentPrecisionEqual(zPrev.x, zCurr.x)) zCurr.x = zPrev.x;
if (occurrentPrecisionEqual(zPrev.y, zCurr.y)) zCurr.y = zPrev.y;
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];
if (zCurr.type === Point.Type.Quadratic && zNext.type === Point.Type.Corner) {
if (occurrentPrecisionEqual(zCurr.x, zNext.x)) zCurr.x = zNext.x;
if (occurrentPrecisionEqual(zCurr.y, zNext.y)) zCurr.y = zNext.y;
alignX.tryAlign(i, (i + 1) % c.length);
alignY.tryAlign(i, (i + 1) % c.length);
}
}
alignX.apply();
alignY.apply();
return c;
}
cleanupOccurrentKnots1(c0) {
@ -227,6 +229,52 @@ class FairizedShapeSink {
return c;
}
}
// Disjoint set for coordinate alignment
class CoordinateAligner {
constructor(c, lens, lensSet) {
this.c = c;
this.lens = lens;
this.lensSet = lensSet;
this.rank = [];
this.up = [];
for (let i = 0; i < c.length; i++) {
const x = lens(c[i]);
this.up[i] = i;
this.rank[i] = Math.abs(x - Math.round(x));
}
}
find(i) {
if (this.up[i] !== i) {
this.up[i] = this.find(this.up[i]);
return this.up[i];
} else {
return i;
}
}
tryAlign(i, j) {
if (occurrentPrecisionEqual(this.lens(this.c[i]), this.lens(this.c[j]))) {
this.align(i, j);
}
}
align(i, j) {
i = this.find(i);
j = this.find(j);
if (this.rank[i] > this.rank[j]) [i, j] = [j, i];
this.up[j] = i;
}
apply() {
for (let i = 0; i < this.c.length; i++) {
this.lensSet(this.c[i], this.lens(this.c[this.find(i)]));
}
}
}
const GetX = z => z.x;
const SetX = (z, x) => (z.x = x);
const GetY = z => z.y;
const SetY = (z, y) => (z.y = y);
function isOccurrent(zFirst, zLast) {
return (
zFirst.type === Point.Type.Corner &&
@ -239,7 +287,7 @@ function occurrentPrecisionEqual(a, b) {
return Math.abs(a - b) < CurveUtil.OCCURRENT_PRECISION;
}
function aligned(a, b, c) {
return occurrentPrecisionEqual(a, b) && occurrentPrecisionEqual(b, c);
return a === b && b === c;
}
function between(a, b, c) {
return (a <= b && b <= c) || (a >= b && b >= c);