/**
 * @author Alexander Farkas
 * @modified by Nicolas DOUILLET
 * v. 1.02-modified
 */
(function($) {
	$.extend($.fx.step,{
	    backgroundPosition: function(fx) {
	    

           function toArray(strg){
               strg = strg.replace(/left|top/g,'0px');
               strg = strg.replace(/right|bottom/g,'100%');
               strg = strg.replace(/([0-9\.]+)(\s|\)|$)/g,"$1px$2");
               var res = strg.match(/(-?[0-9\.,]+)(px|\%|em|pt)\s(-?[0-9\.,]+)(px|\%|em|pt)/);
               return [parseFloat(res[1],10),res[2],parseFloat(res[3],10),res[4]];
           }
            if (fx.state === 0 && typeof fx.end == 'string') {

                var start = $(fx.elem).backgroundPosition();
                start = toArray(start);
                fx.start = [start[0],start[2]];
                var end = toArray(fx.end);
                fx.end = [end[0],end[2]];
                fx.unit = [end[1],end[3]];
			}
            var nowPosX = [];
            nowPosX[0] = ((fx.end[0] - fx.start[0]) * fx.pos) + fx.start[0] + fx.unit[0];
            nowPosX[1] = ((fx.end[1] - fx.start[1]) * fx.pos) + fx.start[1] + fx.unit[1];
            fx.elem.style.backgroundPosition = nowPosX[0]+' '+nowPosX[1];
        }
	});
    
	$.fn.backgroundPosition = function()
	{
	    var t = $(this);
	    var p = t.css("background-position");
	    if ( typeof(p) == "undefined" )
	    {
		p = t.css("background-position-x") + " " + t.css("background-position-y");
	    }

	    return p;
	};

})(jQuery);