Boolean: Bring back on-path winding handling.

Relates to #1281

src/path/Curve.js

@@ -634,8 +634,8 @@ statics: /** @lends Curve */{
      *
      * @param {Number[]} v the curve values, as returned by
      *     {@link Curve#getValues()}
-     * @param {Number} [dir=0] the direction in which the curves should be
-     *     monotone, `0`: monotone in x-direction, `1`: monotone in y-direction
+     * @param {Boolean} [dir=false] the direction in which the curves should be
+     *     monotone, `false`: in x-direction, `true`: in y-direction
      * @return {Number[][]} an array of curve value arrays of the resulting
      *     monotone curve. If the original curve was already monotone, an array
      *     only containing its values are returned.

src/path/PathItem.Boolean.js

@@ -452,8 +452,8 @@ PathItem.inject(new function() {
      * @param {Curve[]} curves the curves that describe the shape against which
      *     to check, as returned by {@link Path#getCurves()} or
      *     {@link CompoundPath#getCurves()}
-     * @param {Number} [dir=0] the direction in which to determine the
-     *     winding contribution, `0`: in x-direction, `1`: in y-direction
+     * @param {Boolean} [dir=false] the direction in which to determine the
+     *     winding contribution, `false`: in x-direction, `true`: in y-direction
      * @param {Boolean} [closed=false] determines how areas should be closed
      *     when a curve is part of an open path, `false`: area is closed with a
      *     straight line, `true`: area is closed taking the handles of the first
@@ -479,7 +479,10 @@ PathItem.inject(new function() {
             paR = pa + windingEpsilon,
             windingL = 0,
             windingR = 0,
+            pathWindingL = 0,
+            pathWindingR = 0,
             onPath = false,
+            onAnyPath = false,
             quality = 1,
             roots = [],
             vPrev,
@@ -532,9 +535,9 @@ PathItem.inject(new function() {
             if (po !== o0) {
                 // Standard case, curve is not crossed at its starting point.
                 if (a < paL) {
-                    windingL += winding;
+                    pathWindingL += winding;
                 } else if (a > paR) {
-                    windingR += winding;
+                    pathWindingR += winding;
                 } else {
                     onPath = true;
                 }
@@ -549,21 +552,21 @@ PathItem.inject(new function() {
                 if (winding !== windingPrev) {
                     // Winding changes from previous curve, cancel its winding.
                     if (a0 < paL) {
-                        windingL += winding;
+                        pathWindingL += winding;
                     } else if (a0 > paR) {
-                        windingR += winding;
+                        pathWindingR += winding;
                     }
                 } else if (a0 != a3Prev) {
                     // Handle a horizontal curve between the current and
                     // previous non-horizontal curve. See
                     // #1261#issuecomment-282726147 for a detailed explanation:
                     if (a3Prev < paR && a > paR) {
                         // Right winding was not added before, so add it now.
-                        windingR += winding;
+                        pathWindingR += winding;
                         onPath = true;
                     } else if (a3Prev > paL && a < paL) {
                         // Left winding was not added before, so add it now.
-                        windingL += winding;
+                        pathWindingL += winding;
                         onPath = true;
                     }
                 }
@@ -578,7 +581,7 @@ PathItem.inject(new function() {
             // again with flipped direction and return that result instead.
             return !dontFlip && a > paL && a < paR
                     && Curve.getTangent(v, t)[dir ? 'x' : 'y'] === 0
-                    && getWinding(point, curves, dir ? 0 : 1, closed, true);
+                    && getWinding(point, curves, !dir, closed, true);
         }
 
         function handleCurve(v) {
@@ -664,6 +667,23 @@ PathItem.inject(new function() {
                 // it now to treat the path as closed:
                 if (vClose && (res = handleCurve(vClose)))
                     return res;
+                if (onPath && !pathWindingL && !pathWindingR) {
+                    // If the point is on the path and the windings canceled
+                    // each other, we treat the point as if it was inside the
+                    // path. A point inside a path has a winding of [+1,-1]
+                    // for clockwise and [-1,+1] for counter-clockwise paths.
+                    // If the ray is cast in y direction (dir == true), the
+                    // windings always have opposite sign.
+                    pathWindingL = pathWindingR = path.isClockwise(closed) ^ dir
+                            ? 1 : -1;
+                }
+                windingL += pathWindingL;
+                windingR += pathWindingR;
+                pathWindingL = pathWindingR = 0;
+                if (onPath) {
+                    onAnyPath = true;
+                    onPath = false;
+                }
                 vClose = null;
             }
         }
@@ -678,7 +698,7 @@ PathItem.inject(new function() {
             windingL: windingL,
             windingR: windingR,
             quality: quality,
-            onPath: onPath
+            onPath: onAnyPath
         };
     }
 
@@ -721,8 +741,7 @@ PathItem.inject(new function() {
                         // from the point (horizontal or vertical), based on the
                         // curve's direction at that point. If tangent is less
                         // than 45°, cast the ray vertically, else horizontally.
-                        dir = abs(curve.getTangentAtTime(t).y) < Math.SQRT1_2
-                            ? 1 : 0;
+                        dir = abs(curve.getTangentAtTime(t).y) < Math.SQRT1_2;
                     // While subtracting, we need to omit this curve if it is
                     // contributing to the second operand and is outside the
                     // first operand.