LinearRing.getCentroid: return null if the geometry has no components. r=pgiraud (closes #2530)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@10116 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Geometry/LinearRing.js

@@ -190,7 +190,7 @@ OpenLayers.Geometry.LinearRing = OpenLayers.Class(
      * {<OpenLayers.Geometry.Point>} The centroid of the collection
      */
     getCentroid: function() {
-        if ( this.components && (this.components.length > 2)) {
+        if (this.components && (this.components.length > 2)) {
             var sumX = 0.0;
             var sumY = 0.0;
             for (var i = 0; i < this.components.length - 1; i++) {
@@ -202,8 +202,10 @@ OpenLayers.Geometry.LinearRing = OpenLayers.Class(
             var area = -1 * this.getArea();
             var x = sumX / (6 * area);
             var y = sumY / (6 * area);
+            return new OpenLayers.Geometry.Point(x, y);
+        } else {
+            return null;
         }
-        return new OpenLayers.Geometry.Point(x, y);
     },
 
     /**

tests/Geometry/LinearRing.html

@@ -112,7 +112,24 @@
         var ring = new OpenLayers.Geometry.LinearRing(components);
         t.eq(ring.getLength(), 40, "getLength returns the correct perimiter");
     }
-    
+
+    function test_LinearRing_getCentroid(t) {
+        t.plan(2);
+        var components = [
+            new OpenLayers.Geometry.Point(0,0), 
+            new OpenLayers.Geometry.Point(0,10),
+            new OpenLayers.Geometry.Point(10,10), 
+            new OpenLayers.Geometry.Point(10,0)
+        ];
+        var ring = new OpenLayers.Geometry.LinearRing(components);
+        var centroid = ring.getCentroid();
+        t.ok(centroid.x === 5 && centroid.y === 5, "getCentroid returns the correct centroid");
+        ring.destroy();
+
+        ring = new OpenLayers.Geometry.LinearRing();
+        t.eq(ring.getCentroid(), null, "getCentroid returns null if no components");     
+    }
+
     function test_LinearRing_move(t) {
 
         var nvert = 4,