Draw popup on DataView Item click

I need to show popup exactly on the point user click but all x,y properties of event (clientX, screenX,x) does not provide me these coordinates. How I can calculate x,y to show the popup?

myDataView.attachEvent("onItemClick", function (id, ev, html){ myPop.show(ev.x,ev.y,100,100); });


popup will centered near specified rectangle: ev.x,ev.y,100,100
just make it smaller, i.e. myPop.show(ev.x,ev.y,ev.x,ev.y);