Adding a RegularPolygon handler for drawing squares, triangles, circles, etc. Demo in the regular-polygon.html example. Also adding a createRegularPolygon class method to the Polygon geometry class. Thanks to crschmidt for all the tests and help getting this in (closes #828).

git-svn-id: http://svn.openlayers.org/trunk/openlayers@4205 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Geometry/Polygon.js

@@ -59,3 +59,31 @@ OpenLayers.Geometry.Polygon = OpenLayers.Class(
 
     CLASS_NAME: "OpenLayers.Geometry.Polygon"
 });
+
+/**
+ * APIMethod: createRegularPolygon
+ * Create a regular polygon around a radius. Useful for creating circles 
+ * and the like.
+ *
+ * Parameters:
+ * origin - {<OpenLayers.Geometry.Point>} center of polygon.
+ * radius - {Float} distance to vertex, in map units.
+ * sides - {Integer} Number of sides. 20 approximates a circle.
+ * rotation - {Float} original angle of rotation, in degrees.
+ */
+OpenLayers.Geometry.Polygon.createRegularPolygon = function(origin, radius, sides, rotation) {  
+    var angle = Math.PI * ((1/sides) - (1/2));
+    if(rotation) {
+        angle += (rotation / 180) * Math.PI;
+    }
+    var rotateAngle, x, y;
+    var points = [];
+    for(var i=0; i<sides; ++i) {
+        rotatedAngle = angle + (i * 2 * Math.PI / sides);
+        x = origin.x + (radius * Math.cos(rotatedAngle));
+        y = origin.y + (radius * Math.sin(rotatedAngle));
+        points.push(new OpenLayers.Geometry.Point(x, y));
+    }
+    var ring = new OpenLayers.Geometry.LinearRing(points);
+    return new OpenLayers.Geometry.Polygon([ring]);
+}