Boolean: Correctly handle open filled paths

Closes #1647

src/path/CurveLocation.js

@@ -424,9 +424,9 @@ var CurveLocation = Base.extend(/** @lends CurveLocation# */{
         //   both values point to the same curve, and the curve-time is to be
         //   handled accordingly further down.
         var c2 = this.getCurve(),
-            c1 = t1 < tMin ? c2.getPrevious() : c2,
+            c1 = c2 && t1 < tMin ? c2.getPrevious() : c2,
             c4 = inter.getCurve(),
-            c3 = t2 < tMin ? c4.getPrevious() : c4;
+            c3 = c4 && t2 < tMin ? c4.getPrevious() : c4;
         // If t1 / t2 are at the end, then step to the next curve.
         if (t1 > tMax)
             c2 = c2.getNext();

src/path/PathItem.Boolean.js

@@ -46,6 +46,10 @@ PathItem.inject(new function() {
             exclude:   { '1': true, '-1': true }
         };
 
+    function getPaths(path) {
+        return path._children || [path];
+    }
+
     /*
      * Creates a clone of the path that we can modify freely, with its matrix
      * applied to its geometry. Calls #reduce() to simplify compound paths and
@@ -53,12 +57,29 @@ PathItem.inject(new function() {
      * make sure all paths have correct winding direction.
      */
     function preparePath(path, resolve) {
-        var res = path.clone(false).reduce({ simplify: true })
+        var res = path
-                .transform(null, true, true);
+            .clone(false)
+            .reduce({ simplify: true })
+            .transform(null, true, true);
+        // For correct results, close open filled paths with straight lines:
+        if (resolve && res.hasFill()) {
+            var paths = getPaths(res);
+            for (var i = 0, l = paths.length; i < l; i++) {
+                var path = paths[i];
+                if (!path._closed) {
+                    // Close with epsilon tolerance, to avoid tiny straight
+                    // that would cause issues with intersection detection.
+                    path.closePath(/*#=*/Numerical.EPSILON);
+                    path.getFirstSegment().setHandleIn(0, 0);
+                    path.getLastSegment().setHandleOut(0, 0);
+                }
+            }
+        }
         return resolve
-                ? res.resolveCrossings().reorient(
+            ? res
-                    res.getFillRule() === 'nonzero', true)
+                .resolveCrossings()
-                : res;
+                .reorient(res.getFillRule() === 'nonzero', true)
+            : res;
     }
 
     function createResult(paths, simplify, path1, path2, options) {
@@ -103,8 +124,8 @@ PathItem.inject(new function() {
         // intersection, path2 is null and getIntersections() handles it.
         var crossings = divideLocations(
                 CurveLocation.expand(_path1.getCrossings(_path2))),
-            paths1 = _path1._children || [_path1],
+            paths1 = getPaths(_path1),
-            paths2 = _path2 && (_path2._children || [_path2]),
+            paths2 = _path2 && getPaths(_path2),
             segments = [],
             curves = [],
             paths;

test/tests/Path_Boolean.js

@@ -1222,3 +1222,11 @@ test('#1351', function() {
     var result = 'M10,10l40,40l50,50';
     compareBoolean(path1.unite(path2), result);
 });
+
+test('#1647', function() {
+    var path1 = PathItem.create("M0,0h60v60h-60z");
+    var path2 = PathItem.create("M60,47c-0.89493,-0.00177 -1.72254,0.47497 -2.17,1.25l-12.12,21c-0.44703,0.77427 -0.44656,1.72831 0.00123,2.50214c0.44779,0.77383 1.27472,1.24963 2.16877,1.24786h24.24c0.89405,0.00177 1.72098,-0.47403 2.16877,-1.24786c0.44779,-0.77383 0.44826,-1.72787 0.00123,-2.50214l-12.12,-21c-0.44746,-0.77503 -1.27507,-1.25177 -2.17,-1.25M64.33,47l12.12,21c0.89315,1.54699 0.89316,3.45295 0.00003,4.99995c-0.89313,1.547 -2.54373,2.50001 -4.33003,2.50005h-24.24c-1.78631,-0.00005 -3.4369,-0.95306 -4.33003,-2.50005c-0.89313,-1.547 -0.89312,-3.45296 0.00003,-4.99995l12.12,-21c0.88236,-1.55771 2.53981,-2.51466 4.33,-2.5c1.79019,-0.01466 3.44764,0.94229 4.33,2.5");
+    path1.fillColor = path2.fillColor = 'black';
+    var result = 'M57.83,48.25l-6.78143,11.75l-2.88143,0l7.50286,-13c0.88236,-1.55771 2.53981,-2.51466 4.33,-2.5v2.5c-0.89493,-0.00177 -1.72254,0.47497 -2.17,1.25z';
+    compareBoolean(path1.intersect(path2), result);
+});