title: openlayers polygon displays difference not union
body: <p>In OpenLayers, I create a polygon consisting of two LinearRing objects, using code of the form (this is in Java+GWT, but the same principle applies to JS):</p>
  
  <pre><code>List&lt;LinearRing&gt; linearRingList = new ArrayList&lt;LinearRing&gt;();
  
  List&lt;Point&gt; points1 = new ArrayList&lt;Point&gt;();
  ... populate points1 ...;
  linearRingList.add(new LinearRing(points1.toArray(new Point[points.size()])));
  
  List&lt;Point&gt; points2 = new ArrayList&lt;Point&gt;();
  ... populate points2 ...;
  linearRingList.add(new LinearRing(points2.toArray(new Point[points.size()])));
  
  Polygon poly = new Polygon(linearRingList.toArray(new LinearRing[linearRingList.size()]));
  VectorFeature feature = new VectorFeature(poly);
  myLayer.addFeature(feature);
  </code></pre>
  
  <p>When I view this layer on a map, if the polygons defined by points1 and points2 overlap, I see a hole:</p>
  
  <p><a href="http://www.jackhollow.co.uk/misc/polygon.png" rel="nofollow noreferrer">polygon hole http://www.jackhollow.co.uk/misc/polygon.png</a></p>
  
  <p>I'm seeing the "xor" of the two polygons, where I want to see the "or" of them instead, ie with that hole in the middle filled in green.</p>
  
  <p>How do I do this?  I'm sure it's just a display issue in Openlayers, but I can't find a flag to control it anywhere.</p>
  
  <p>The original two polygons are as:</p>
  
  <p><a href="http://www.jackhollow.co.uk/misc/polygon2.png" rel="nofollow noreferrer">polygon hole http://www.jackhollow.co.uk/misc/polygon2.png</a></p>
  
  <p>if displayed together on a single layer they overlap, but Openlayers is not filling in the intersecting parts.</p>