/* * jQuery.appear * https://github.com/bas2k/jquery.appear/ * http://code.google.com/p/jquery-appear/ * http://bas2k.ru/ * * Copyright (c) 2009 Michael Hixson * Copyright (c) 2012-2014 Alexander Brovikov * Licensed under the MIT license (http://www.opensource.org/licenses/mit-license.php) */(function($) {    $.fn.appear = function(fn, options) {
        var settings = $.extend({
            //arbitrary data to pass to fn            data: undefined,
            //call fn only on the first appear?            one: true,
            // X & Y accuracy            accX: 0,            accY: 0
        }, options);
        return this.each(function() {
            var t = $(this);
            //whether the element is currently visible            t.appeared = false;
            if (!fn) {
                //trigger the custom event                t.trigger('appear', settings.data);                return;            }
            var w = $(window);
            //fires the appear event when appropriate            var check = function() {
                //is the element hidden?                if (!t.is(':visible')) {
                    //it became hidden                    t.appeared = false;                    return;                }
                //is the element inside the visible window?                var a = w.scrollLeft();                var b = w.scrollTop();                var o = t.offset();                var x = o.left;                var y = o.top;
                var ax = settings.accX;                var ay = settings.accY;                var th = t.height();                var wh = w.height();                var tw = t.width();                var ww = w.width();
                if (y + th + ay >= b &&                    y <= b + wh + ay &&                    x + tw + ax >= a &&                    x <= a + ww + ax) {
                    //trigger the custom event                    if (!t.appeared) t.trigger('appear', settings.data);
                } else {
                    //it scrolled out of view                    t.appeared = false;                }            };
            //create a modified fn with some additional logic            var modifiedFn = function() {
                //mark the element as visible                t.appeared = true;
                //is this supposed to happen only once?                if (settings.one) {
                    //remove the check                    w.unbind('scroll', check);                    var i = $.inArray(check, $.fn.appear.checks);                    if (i >= 0) $.fn.appear.checks.splice(i, 1);                }
                //trigger the original fn                fn.apply(this, arguments);            };
            //bind the modified fn to the element            if (settings.one) t.one('appear', settings.data, modifiedFn);            else t.bind('appear', settings.data, modifiedFn);
            //check whenever the window scrolls            w.scroll(check);
            //check whenever the dom changes            $.fn.appear.checks.push(check);
            //check now            (check)();        });    };
    //keep a queue of appearance checks    $.extend($.fn.appear, {
        checks: [],        timeout: null,
        //process the queue        checkAll: function() {            var length = $.fn.appear.checks.length;            if (length > 0) while (length--) ($.fn.appear.checks[length])();        },
        //check the queue asynchronously        run: function() {            if ($.fn.appear.timeout) clearTimeout($.fn.appear.timeout);            $.fn.appear.timeout = setTimeout($.fn.appear.checkAll, 20);        }    });
    //run checks when these methods are called    $.each(['append', 'prepend', 'after', 'before', 'attr',        'removeAttr', 'addClass', 'removeClass', 'toggleClass',        'remove', 'css', 'show', 'hide'], function(i, n) {        var old = $.fn[n];        if (old) {            $.fn[n] = function() {                var r = old.apply(this, arguments);                $.fn.appear.run();                return r;            }        }    });
})(jQuery);