Reduce memory use and improve perfs when computing the bounding box of a bezier curve (bug 1875547)

It isn't really a fix for the mentioned bug but it slightly improve things.
In reducing the memory use, the time spent in the GC is reduced either.
The algorithm to compute the bounding box is the same as before but it has just
been rewritten to be more efficient.

Author: calixteman

src/core/evaluator.js

@@ -1386,17 +1386,17 @@ class PartialEvaluator {
           const y = args[1] + args[3];
           minMax = [
             Math.min(args[0], x),
-            Math.max(args[0], x),
             Math.min(args[1], y),
+            Math.max(args[0], x),
             Math.max(args[1], y),
           ];
           break;
         case OPS.moveTo:
         case OPS.lineTo:
-          minMax = [args[0], args[0], args[1], args[1]];
+          minMax = [args[0], args[1], args[0], args[1]];
           break;
         default:
-          minMax = [Infinity, -Infinity, Infinity, -Infinity];
+          minMax = [Infinity, Infinity, -Infinity, -Infinity];
           break;
       }
       operatorList.addOp(OPS.constructPath, [[fn], args, minMax]);
@@ -1420,15 +1420,15 @@ class PartialEvaluator {
           const x = args[0] + args[2];
           const y = args[1] + args[3];
           minMax[0] = Math.min(minMax[0], args[0], x);
-          minMax[1] = Math.max(minMax[1], args[0], x);
-          minMax[2] = Math.min(minMax[2], args[1], y);
+          minMax[1] = Math.min(minMax[1], args[1], y);
+          minMax[2] = Math.max(minMax[2], args[0], x);
           minMax[3] = Math.max(minMax[3], args[1], y);
           break;
         case OPS.moveTo:
         case OPS.lineTo:
           minMax[0] = Math.min(minMax[0], args[0]);
-          minMax[1] = Math.max(minMax[1], args[0]);
-          minMax[2] = Math.min(minMax[2], args[1]);
+          minMax[1] = Math.min(minMax[1], args[1]);
+          minMax[2] = Math.max(minMax[2], args[0]);
           minMax[3] = Math.max(minMax[3], args[1]);
           break;
       }

src/display/canvas.js

@@ -529,18 +529,14 @@ class CanvasExtraState {
   updateScalingPathMinMax(transform, minMax) {
     Util.scaleMinMax(transform, minMax);
     this.minX = Math.min(this.minX, minMax[0]);
-    this.maxX = Math.max(this.maxX, minMax[1]);
-    this.minY = Math.min(this.minY, minMax[2]);
+    this.minY = Math.max(this.minY, minMax[1]);
+    this.maxX = Math.min(this.maxX, minMax[2]);
     this.maxY = Math.max(this.maxY, minMax[3]);
   }
 
   updateCurvePathMinMax(transform, x0, y0, x1, y1, x2, y2, x3, y3, minMax) {
-    const box = Util.bezierBoundingBox(x0, y0, x1, y1, x2, y2, x3, y3);
+    const box = Util.bezierBoundingBox(x0, y0, x1, y1, x2, y2, x3, y3, minMax);
     if (minMax) {
-      minMax[0] = Math.min(minMax[0], box[0], box[2]);
-      minMax[1] = Math.max(minMax[1], box[0], box[2]);
-      minMax[2] = Math.min(minMax[2], box[1], box[3]);
-      minMax[3] = Math.max(minMax[3], box[1], box[3]);
       return;
     }
     this.updateRectMinMax(transform, box);

src/shared/util.js

@@ -651,7 +651,7 @@ class Util {
 
   // Apply a scaling matrix to some min/max values.
   // If a scaling factor is negative then min and max must be
-  // swaped.
+  // swapped.
   static scaleMinMax(transform, minMax) {
     let temp;
     if (transform[0]) {
@@ -822,76 +822,116 @@ class Util {
     return [xLow, yLow, xHigh, yHigh];
   }
 
-  // From https://github.com/adobe-webplatform/Snap.svg/blob/b365287722a72526000ac4bfcf0ce4cac2faa015/src/path.js#L852
-  static bezierBoundingBox(x0, y0, x1, y1, x2, y2, x3, y3) {
-    const tvalues = [],
-      bounds = [[], []];
-    let a, b, c, t, t1, t2, b2ac, sqrtb2ac;
-    for (let i = 0; i < 2; ++i) {
-      if (i === 0) {
-        b = 6 * x0 - 12 * x1 + 6 * x2;
-        a = -3 * x0 + 9 * x1 - 9 * x2 + 3 * x3;
-        c = 3 * x1 - 3 * x0;
-      } else {
-        b = 6 * y0 - 12 * y1 + 6 * y2;
-        a = -3 * y0 + 9 * y1 - 9 * y2 + 3 * y3;
-        c = 3 * y1 - 3 * y0;
-      }
-      if (Math.abs(a) < 1e-12) {
-        if (Math.abs(b) < 1e-12) {
-          continue;
-        }
-        t = -c / b;
-        if (0 < t && t < 1) {
-          tvalues.push(t);
-        }
-        continue;
-      }
-      b2ac = b * b - 4 * c * a;
-      sqrtb2ac = Math.sqrt(b2ac);
-      if (b2ac < 0) {
-        continue;
-      }
-      t1 = (-b + sqrtb2ac) / (2 * a);
-      if (0 < t1 && t1 < 1) {
-        tvalues.push(t1);
-      }
-      t2 = (-b - sqrtb2ac) / (2 * a);
-      if (0 < t2 && t2 < 1) {
-        tvalues.push(t2);
-      }
+  static #getExtremumOnCurve(x0, x1, x2, x3, y0, y1, y2, y3, t, minMax) {
+    if (t <= 0 || t >= 1) {
+      return;
     }
+    const mt = 1 - t;
+    const tt = t * t;
+    const ttt = tt * t;
+    const x = mt * (mt * (mt * x0 + 3 * t * x1) + 3 * tt * x2) + ttt * x3;
+    const y = mt * (mt * (mt * y0 + 3 * t * y1) + 3 * tt * y2) + ttt * y3;
+    minMax[0] = Math.min(minMax[0], x);
+    minMax[1] = Math.min(minMax[1], y);
+    minMax[2] = Math.max(minMax[2], x);
+    minMax[3] = Math.max(minMax[3], y);
+  }
 
-    let j = tvalues.length,
-      mt;
-    const jlen = j;
-    while (j--) {
-      t = tvalues[j];
-      mt = 1 - t;
-      bounds[0][j] =
-        mt * mt * mt * x0 +
-        3 * mt * mt * t * x1 +
-        3 * mt * t * t * x2 +
-        t * t * t * x3;
-      bounds[1][j] =
-        mt * mt * mt * y0 +
-        3 * mt * mt * t * y1 +
-        3 * mt * t * t * y2 +
-        t * t * t * y3;
+  static #getExtremum(x0, x1, x2, x3, y0, y1, y2, y3, a, b, c, minMax) {
+    if (Math.abs(a) < 1e-12) {
+      if (Math.abs(b) >= 1e-12) {
+        this.#getExtremumOnCurve(
+          x0,
+          x1,
+          x2,
+          x3,
+          y0,
+          y1,
+          y2,
+          y3,
+          -c / b,
+          minMax
+        );
+      }
+      return;
     }
 
-    bounds[0][jlen] = x0;
-    bounds[1][jlen] = y0;
-    bounds[0][jlen + 1] = x3;
-    bounds[1][jlen + 1] = y3;
-    bounds[0].length = bounds[1].length = jlen + 2;
+    const delta = b ** 2 - 4 * c * a;
+    if (delta < 0) {
+      return;
+    }
+    const sqrtDelta = Math.sqrt(delta);
+    const a2 = 2 * a;
+    this.#getExtremumOnCurve(
+      x0,
+      x1,
+      x2,
+      x3,
+      y0,
+      y1,
+      y2,
+      y3,
+      (-b + sqrtDelta) / a2,
+      minMax
+    );
+    this.#getExtremumOnCurve(
+      x0,
+      x1,
+      x2,
+      x3,
+      y0,
+      y1,
+      y2,
+      y3,
+      (-b - sqrtDelta) / a2,
+      minMax
+    );
+  }
 
-    return [
-      Math.min(...bounds[0]),
-      Math.min(...bounds[1]),
-      Math.max(...bounds[0]),
-      Math.max(...bounds[1]),
-    ];
+  // From https://github.com/adobe-webplatform/Snap.svg/blob/b365287722a72526000ac4bfcf0ce4cac2faa015/src/path.js#L852
+  static bezierBoundingBox(x0, y0, x1, y1, x2, y2, x3, y3, minMax) {
+    if (minMax) {
+      minMax[0] = Math.min(minMax[0], x0, x3);
+      minMax[1] = Math.min(minMax[1], y0, y3);
+      minMax[2] = Math.max(minMax[2], x0, x3);
+      minMax[3] = Math.max(minMax[3], y0, y3);
+    } else {
+      minMax = [
+        Math.min(x0, x3),
+        Math.min(y0, y3),
+        Math.max(x0, x3),
+        Math.max(y0, y3),
+      ];
+    }
+    this.#getExtremum(
+      x0,
+      x1,
+      x2,
+      x3,
+      y0,
+      y1,
+      y2,
+      y3,
+      3 * (-x0 + 3 * (x1 - x2) + x3),
+      6 * (x0 - 2 * x1 + x2),
+      3 * (x1 - x0),
+      minMax
+    );
+    this.#getExtremum(
+      x0,
+      x1,
+      x2,
+      x3,
+      y0,
+      y1,
+      y2,
+      y3,
+      3 * (-y0 + 3 * (y1 - y2) + y3),
+      6 * (y0 - 2 * y1 + y2),
+      3 * (y1 - y0),
+      minMax
+    );
+    return minMax;
   }
 }
 

test/unit/annotation_spec.js

@@ -4548,7 +4548,7 @@ describe("annotation", function () {
       expect(opList.argsArray[5][0]).toEqual([OPS.moveTo, OPS.curveTo]);
       expect(opList.argsArray[5][1]).toEqual([1, 2, 3, 4, 5, 6, 7, 8]);
       // Min-max.
-      expect(opList.argsArray[5][2]).toEqual([1, 1, 2, 2]);
+      expect(opList.argsArray[5][2]).toEqual([1, 2, 1, 2]);
     });
   });
 

test/unit/api_spec.js

@@ -771,7 +771,7 @@ describe("api", function () {
         [
           [OPS.moveTo, OPS.lineTo],
           [0, 9.75, 0.5, 9.75],
-          [0, 0.5, 9.75, 9.75],
+          [0, 9.75, 0.5, 9.75],
         ],
         null,
       ]);