Add ol.geom.Polygon#getLinearRing

src/ol/geom/polygon.exports

@@ -4,6 +4,7 @@
 @exportProperty ol.geom.Polygon.prototype.getArea
 @exportProperty ol.geom.Polygon.prototype.getCoordinates
 @exportProperty ol.geom.Polygon.prototype.getInteriorPoint
+@exportProperty ol.geom.Polygon.prototype.getLinearRing
 @exportProperty ol.geom.Polygon.prototype.getLinearRings
 @exportProperty ol.geom.Polygon.prototype.getType
 @exportProperty ol.geom.Polygon.prototype.setCoordinates

src/ol/geom/polygon.js

@@ -178,6 +178,22 @@ ol.geom.Polygon.prototype.getInteriorPoint = function() {
 };
 
 
+/**
+ * @param {number} index Index.
+ * @return {ol.geom.LinearRing} Linear ring.
+ */
+ol.geom.Polygon.prototype.getLinearRing = function(index) {
+  goog.asserts.assert(0 <= index && index < this.ends_.length);
+  if (index < 0 || this.ends_.length <= index) {
+    return null;
+  }
+  var linearRing = new ol.geom.LinearRing(null);
+  linearRing.setFlatCoordinates(this.layout, this.flatCoordinates.slice(
+      index === 0 ? 0 : this.ends_[index - 1], this.ends_[index]));
+  return linearRing;
+};
+
+
 /**
  * @return {Array.<ol.geom.LinearRing>} Linear rings.
  * @todo stability experimental

test/spec/ol/geom/polygon.test.js

@@ -84,6 +84,11 @@ describe('ol.geom.Polygon', function() {
       expect(polygon.getStride()).to.be(2);
     });
 
+    it('can return individual rings', function() {
+      expect(polygon.getLinearRing(0).getCoordinates()).to.eql(outerRing);
+      expect(polygon.getLinearRing(1).getCoordinates()).to.eql(innerRing);
+    });
+
     it('has the expected rings', function() {
       var linearRings = polygon.getLinearRings();
       expect(linearRings).to.be.an(Array);