code: function(evt) {
          this.fixedRadius = !!(this.radius);
          var maploc = this.layer.getLonLatFromViewPortPx(evt.xy); 
          this.origin = new OpenLayers.Geometry.Point(maploc.lon, maploc.lat);
          // create the new polygon
          if(!this.fixedRadius || this.irregular) {
              // smallest radius should not be less one pixel in map units
              // VML doesn't behave well with smaller
              this.radius = this.map.getResolution();
          }
          if(this.persist) {
              this.clear();
          }
          this.feature = new OpenLayers.Feature.Vector();
          this.createGeometry();
          this.callback("create", [this.origin, this.feature]);
          this.layer.addFeatures([this.feature], {silent: true});
          this.layer.drawFeature(this.feature, this.style);
      }
docs: Method: down
  Start drawing a new feature
  
  Parameters:
  evt - {Event} The drag start event