Is it possible to have event.offsetX always relative to the element with the listener?

gistfile1.js

/*
 * +--------------------+
 * |      element1      |
 * |    +----------+    |
 * |    | element2 |    |
 * |    +----------+    |
 * +--------------------+
 *
 * (element2 is a child of element1)
 * 
 * Is it possible to have event.offsetX
 * always relative to element1 regardless of
 * whether element1 or element2 is clicked?
 *
 */

element1.addEventListener( 'click', function ( event ) {

	console.log( event.offsetX );

}, false );

// I would like to stop using this workaround...

element1.addEventListener( 'click', function ( event ) {

	var offsetX = event.offsetX;
	var node = event.target;

	while ( node !== this ) {

		offsetX += node.offsetLeft;
		node = node.parentNode;

	}

	console.log( offsetX );

}, false );

Meh... event.x is undefined in Firefox :(

what about something like:

console.log( (event.clientX + document.documentElement.scrollLeft) || (event.x + this.scrollLeft) );