code: function() {
          var geometry = this.feature.geometry;
          var bounds = geometry.getBounds();
          var center = bounds.getCenterLonLat();
          var originGeometry = new OpenLayers.Geometry.Point(
              center.lon, center.lat
          );
          var radiusGeometry = new OpenLayers.Geometry.Point(
              bounds.right, bounds.bottom
          );
          var radius = new OpenLayers.Feature.Vector(radiusGeometry);
          var resize = (this.mode & OpenLayers.Control.ModifyFeature.RESIZE);
          var reshape = (this.mode & OpenLayers.Control.ModifyFeature.RESHAPE);
          var rotate = (this.mode & OpenLayers.Control.ModifyFeature.ROTATE);
  
          radiusGeometry.move = function(x, y) {
              OpenLayers.Geometry.Point.prototype.move.call(this, x, y);
              var dx1 = this.x - originGeometry.x;
              var dy1 = this.y - originGeometry.y;
              var dx0 = dx1 - x;
              var dy0 = dy1 - y;
              if(rotate) {
                  var a0 = Math.atan2(dy0, dx0);
                  var a1 = Math.atan2(dy1, dx1);
                  var angle = a1 - a0;
                  angle *= 180 / Math.PI;
                  geometry.rotate(angle, originGeometry);
              }
              if(resize) {
                  var scale, ratio;
                  // 'resize' together with 'reshape' implies that the aspect 
                  // ratio of the geometry will not be preserved whilst resizing 
                  if (reshape) {
                      scale = dy1 / dy0;
                      ratio = (dx1 / dx0) / scale;
                  } else {
                      var l0 = Math.sqrt((dx0 * dx0) + (dy0 * dy0));
                      var l1 = Math.sqrt((dx1 * dx1) + (dy1 * dy1));
                      scale = l1 / l0;
                  }
                  geometry.resize(scale, originGeometry, ratio);
              }
          };
          radius._sketch = true;
          this.radiusHandle = radius;
          this.radiusHandle.renderIntent = this.vertexRenderIntent;
          this.layer.addFeatures([this.radiusHandle], {silent: true});
      }
docs: Method: collectRadiusHandle
  Collect the radius handle for the selected geometry.