jQuery scrolly special event

jquery.scrolly.js

/* 
 * Changes by Zach Leatherman (@zachleat)
 *     from James Padolsey Special Scroll Events
 *     http://james.padolsey.com/javascript/special-scroll-events-for-jquery/
 * -------------------------------------------------------
 * Dual licensed under the MIT and GPL licenses.
 *     http://www.opensource.org/licenses/mit-license.php
 *     http://www.gnu.org/copyleft/gpl.html
 */

(function($){

    var special = $.event.special;

    special.scrolly = {
        latency: 30,
        setup: function()
        {
            var timer,
                scrolly = -1,
                scrollx = -1;

            $(this).bind('scroll.scrolly', function(event)
            {
                var _self = this,
                    _args = arguments,
                    $t = $(this);

                if (timer) {
                    clearTimeout(timer);
                } else {
                    scrolly = $t.scrollTop();
                    scrollx = $t.scrollLeft();
                }

                timer = setTimeout(function()
                {
                    timer = null;
                    if(scrolly >= 0 && (scrolly !== $t.scrollTop() || scrollx == $t.scrollLeft())) {
                        event.type = 'scrolly';
                        jQuery.event.handle.apply(_self, _args);
                    }
                }, special.scrolly.latency);
            });
        },
        teardown: function() {
            $(this).unbind('scroll.scrolly');
        }
    };

})(jQuery);