title: How to get the exact mouse down coordinate? Why my code does not work?
body: <p>I would like to show something at the mouse down place, I tried to use :</p>
  
  <pre><code>$('#my-graph').mousedown(function(evt){
  
        // show object at:
        var x= evt.screenX, y=evt.screenY;
  
        //or show object at:
       var x2=evt.pageX, y2=evt.pageY;
  
       //code to render object at (x,y) and (x2,y2)
       ......  
  });
  </code></pre>
  
  <p>But neither of the above (x, y) and (x2,y2) place the rendered object at the mouse clicked place, and show the object some distance away from mouse down place, why?</p>
  
  <p>I render the object with a position attributes, the position is relative to the <strong>#my-graph</strong> div, left up most corner of the div is supposed to be the origin point(0,0)</p>