fix cases of bad diagonals in the split routine

mapbox · Mar 17, 2016 · d13c8dc · d13c8dc
1 parent 7bd7a0b
commit d13c8dc
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Showing 3 changed files with 6 additions and 2 deletions.
diff --git a/src/earcut.js b/src/earcut.js
@@ -460,7 +460,7 @@ function pointInTriangle(ax, ay, bx, by, cx, cy, px, py) {
 
 // check if a diagonal between two polygon nodes is valid (lies in polygon interior)
 function isValidDiagonal(a, b) {
-    return equals(a, b) || a.next.i !== b.i && a.prev.i !== b.i && !intersectsPolygon(a, b) &&
+    return a.next.i !== b.i && a.prev.i !== b.i && !intersectsPolygon(a, b) &&
            locallyInside(a, b) && locallyInside(b, a) && middleInside(a, b);
 }
 
@@ -476,6 +476,8 @@ function equals(p1, p2) {
 
 // check if two segments intersect
 function intersects(p1, q1, p2, q2) {
+    if ((equals(p1, q1) && equals(p2, q2)) ||
+        (equals(p1, q2) && equals(p2, q1))) return true;
     return area(p1, q1, p2) > 0 !== area(p1, q1, q2) > 0 &&
            area(p2, q2, p1) > 0 !== area(p2, q2, q1) > 0;
 }

diff --git a/test/fixtures/bad-diagonals.json b/test/fixtures/bad-diagonals.json
@@ -0,0 +1 @@
+[[[440,4152],[440,4208],[296,4192],[368,4192],[400,4200],[400,4176],[368,4192],[296,4192],[264,4200],[288,4160],[296,4192]]]
diff --git a/test/test.js b/test/test.js
@@ -12,7 +12,7 @@ areaTest('water2', 1212);
 areaTest('water3', 197);
 areaTest('water3b', 25);
 areaTest('water4', 705);
-areaTest('water-huge', 5173, 0.0011);
+areaTest('water-huge', 5174, 0.0011);
 areaTest('water-huge2', 4461, 0.0028);
 areaTest('degenerate', 0);
 areaTest('bad-hole', 42, 0.019);
@@ -34,6 +34,7 @@ areaTest('eberly-3', 73);
 areaTest('eberly-6', 1429);
 areaTest('issue52', 109);
 areaTest('shared-points', 4);
+areaTest('bad-diagonals', 7);
 
 test('indices-2d', function (t) {
     var indices = earcut([10, 0, 0, 50, 60, 60, 70, 10]);