var element      = evt.target;
                var arc = element.shadowTree;
                var path    = arc.getElementById("drawing_arc");
                
                // get attributes from custom tag
		

		var cx = 0, cy = 0, r = 0, start = 0, sweep = 0, orientation = "default", units = "degrees";
		nb_attributes = element.attributes.length
		for (i = 0; i < nb_attributes;i++)
		{
		attribute = element.attributes.item(i)
		switch(attribute.name)
			{case "cx" : cx = attribute.value - 0 ; break;
			 case "cy" : cy = attribute.value - 0 ; break;
			 case "r"  : r = attribute.value - 0 ; break;
			 case "start" : start = attribute.value - 0 ; break;
			 case "sweep" : sweep = attribute.value - 0 ; break;
			 case "orientation" : orientation = attribute.value ; break;
			 case "units" : units = attribute.value ; break;
			}
		}

		if (orientation == "maths")
		{
			start = 0 - start
			sweep = 0 - sweep
		}

		if (units == "degrees")
		{
                start = start * Math.PI / 180;
                sweep = sweep * Math.PI / 180;
		}

                // calculate d attribute for path
                var x_begin = cx + r * Math.cos(start);
		var y_begin = cy + r * Math.sin(start);
                var x_end = cx + r * Math.cos(start + sweep);
		var y_end = cy + r * Math.sin(start + sweep);
		var rotate = 0;
		if (Math.abs(sweep) < Math.PI)
			large_flag = 0
		else
			large_flag = 1
		if (sweep > 0)
			sweep_flag = 1
		else
			sweep_flag = 0


           	var d="M" + x_begin.toString() + " " + y_begin.toString() + "A" + r.toString() + " " + r.toString() + " "
		       + rotate.toString()
		      + " " + large_flag.toString() + " " + sweep_flag.toString() + " " + x_end.toString() + " " + y_end.toString() 


                // apply attributes
                path.setAttributeNS(null, "d", d);