From 656af726155c7f7f74dc7334c5d866040046e1d2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Harrtell?= <bjorn@wololo.org>
Date: Sat, 5 Nov 2016 14:34:09 +0100
Subject: [PATCH] Use winding number algorithm for linearRingContainsXY

---
 src/ol/geom/flat/contains.js            | 22 +++++++++++++++-------
 test/spec/ol/geom/flat/contains.test.js |  2 +-
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/src/ol/geom/flat/contains.js b/src/ol/geom/flat/contains.js
index 3e7cfea7a0..e771be89eb 100644
--- a/src/ol/geom/flat/contains.js
+++ b/src/ol/geom/flat/contains.js
@@ -36,22 +36,30 @@ ol.geom.flat.contains.linearRingContainsExtent = function(flatCoordinates, offse
  * @return {boolean} Contains (x, y).
  */
 ol.geom.flat.contains.linearRingContainsXY = function(flatCoordinates, offset, end, stride, x, y) {
-  // http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html
-  var contains = false;
+  // http://geomalgorithms.com/a03-_inclusion.html
+  // Copyright 2000 softSurfer, 2012 Dan Sunday
+  // This code may be freely used and modified for any purpose
+  // providing that this copyright notice is included with it.
+  // SoftSurfer makes no warranty for this code, and cannot be held
+  // liable for any real or imagined damage resulting from its use.
+  // Users of this code must verify correctness for their application.
+  var wn = 0;
   var x1 = flatCoordinates[end - stride];
   var y1 = flatCoordinates[end - stride + 1];
   for (; offset < end; offset += stride) {
     var x2 = flatCoordinates[offset];
     var y2 = flatCoordinates[offset + 1];
-    var intersect = ((y1 > y) != (y2 > y)) &&
-        (x < (x2 - x1) * (y - y1) / (y2 - y1) + x1);
-    if (intersect) {
-      contains = !contains;
+    if (y1 <= y) {
+      if (y2 > y && ((x2 - x1) * (y - y1)) - ((x - x1) * (y2 - y1)) > 0) {
+        wn++;
+      }
+    } else if (y2 <= y && ((x2 - x1) * (y - y1)) - ((x - x1) * (y2 - y1)) < 0) {
+      wn--;
     }
     x1 = x2;
     y1 = y2;
   }
-  return contains;
+  return wn !== 0;
 };
 
 
diff --git a/test/spec/ol/geom/flat/contains.test.js b/test/spec/ol/geom/flat/contains.test.js
index 68f4e1b0dc..3a35a8d5e8 100644
--- a/test/spec/ol/geom/flat/contains.test.js
+++ b/test/spec/ol/geom/flat/contains.test.js
@@ -10,7 +10,7 @@ describe('ol.geom.flat.contains', function() {
     var flatCoordinatesSimple = [0, 0, 1, 0, 1, 1, 0, 1];
     var flatCoordinatesNonSimple = [0, 0, 4, 0, 4, 3, 1, 3, 1, 2, 3, 2, 3, 1, 2, 1, 2, 4, 0, 4];
 
-    describe('ol.geom.flat.closest.getMaxSquaredDelta', function() {
+    describe('ol.geom.flat.contains.linearRingContainsXY', function() {
 
       it('returns true for point inside a simple polygon', function() {
         expect(ol.geom.flat.contains.linearRingContainsXY(