You need to pass the coordinates of the element to the mouseDown, mouseUp and click events in order to properly trigger the event on the canvas.
Again, you're reinventing a lot of what has already been done so might be best for you to hold off till the code hits SVN. Don't have an exact date but expect it soon.
Code:
var clientX = isc.Element.getElementRect(element)[0]; var clientY = isc.Element.getElementRect(element)[1];
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