javascript - OpenLayers - Draw polygon with exact number of points -

i have ui give user ability draw area on map, , want him draw polygon 4 points, how do ?

this done in example here

the code use draw bow is:

var boxlayer = new openlayers.layer.vector("box layer");              map.addlayer(boxlayer);               drawcontrols = {                 box: new openlayers.control.drawfeature(boxlayer,                     openlayers.handler.regularpolygon, {                         handleroptions: {                             sides: 4,                             irregular: true                         }                     } }