使用 Tiny Scrollbar 自动滚动到 div 底部

我正在编写一个shoutbox 并使其尽可能用户友好。它使用微型滚动条插件 http://plugins.jquery.com/project/tinyscrollbar对于 jQuery，我想合并一个额外的函数，让我可以让它到达底部div。它应该自动滚动（可能具有平滑的动画效果）到底部。

这是实际的小滚动条代码：

(function($){
$.tiny = $.tiny || { };

$.tiny.scrollbar = {
    options: {  
        axis: 'y', // vertical or horizontal scrollbar? ( x || y ).
        wheel: 40,  //how many pixels must the mouswheel scroll at a time.
        scroll: true, //enable or disable the mousewheel;
        size: 'auto', //set the size of the scrollbar to auto or a fixed number.
        sizethumb: 'auto' //set the size of the thumb to auto or a fixed number.
    }
};  

$.fn.tinyscrollbar = function(options) { 
    var oElement = null;
    var options = $.extend({}, $.tiny.scrollbar.options, options); 

    this.each(function() {  
        oElement = new Scrollbar($(this), options);
    });
    return $.extend(this, oElement);
};

function Scrollbar(root, options){
    var oSelf = this;
    var oWrapper = root;
    var oViewport = { obj: $('.viewport', root) };
    var oContent = { obj: $('.overview', root) };
    var oScrollbar = { obj: $('.scrollbar', root) };
    var oTrack = { obj: $('.track', oScrollbar.obj) };
    var oThumb = { obj: $('.thumb', oScrollbar.obj) };
    var sAxis = options.axis == 'x', sDirection = sAxis ? 'left' : 'top', sSize = sAxis ? 'Width' : 'Height';
    var iScroll, iPosition = { start: 0, now: 0 }, iMouse = {};

    function initialize() { 
        oSelf.update();
        setEvents();
        return oSelf;
    }
    this.update = function(bKeepScroll){            
        oViewport[options.axis] = oViewport.obj[0]['offset'+ sSize];
        oContent[options.axis] = oContent.obj[0]['scroll'+ sSize];
        oContent.ratio = oViewport[options.axis] / oContent[options.axis];
        oScrollbar.obj.toggleClass('disable', oContent.ratio >= 1);
        oTrack[options.axis] = options.size == 'auto' ? oViewport[options.axis] : options.size;
        oThumb[options.axis] = Math.min(oTrack[options.axis], Math.max(0, ( options.sizethumb == 'auto' ? (oTrack[options.axis] * oContent.ratio) : options.sizethumb )));
        oScrollbar.ratio = options.sizethumb == 'auto' ? (oContent[options.axis] / oTrack[options.axis]) : (oContent[options.axis] - oViewport[options.axis]) / (oTrack[options.axis] - oThumb[options.axis]);
        iScroll = (bKeepScroll && oContent.ratio <= 1) ? Math.min((oContent[options.axis] - oViewport[options.axis]), Math.max(0, iScroll)) : 0;
        setSize();
    }
    function setSize(){
        oThumb.obj.css(sDirection, iScroll / oScrollbar.ratio);
        oContent.obj.css(sDirection, -iScroll);
        iMouse['start'] = oThumb.obj.offset()[sDirection];
        var sCssSize = sSize.toLowerCase(); 
        oScrollbar.obj.css(sCssSize, oTrack[options.axis]);
        oTrack.obj.css(sCssSize, oTrack[options.axis]);
        oThumb.obj.css(sCssSize, oThumb[options.axis]);     
    };      
    function setEvents(){
        oThumb.obj.bind('mousedown', start);
        oThumb.obj[0].ontouchstart = function(oEvent){
            oEvent.preventDefault();
            oThumb.obj.unbind('mousedown');
            start(oEvent.touches[0]);
            return false;
        }           
        oTrack.obj.bind('mouseup', drag);
        if(options.scroll && this.addEventListener){
            oWrapper[0].addEventListener('DOMMouseScroll', wheel, false);
            oWrapper[0].addEventListener('mousewheel', wheel, false );
        }
        else if(options.scroll){oWrapper[0].onmousewheel = wheel;}
    };
    function start(oEvent){
        iMouse.start = sAxis ? oEvent.pageX : oEvent.pageY;
        var oThumbDir = parseInt(oThumb.obj.css(sDirection));
        iPosition.start = oThumbDir == 'auto' ? 0 : oThumbDir;
        $(document).bind('mousemove', drag);
        document.ontouchmove = function(oEvent){
            $(document).unbind('mousemove');
            drag(oEvent.touches[0]);
        };
        $(document).bind('mouseup', end);
        oThumb.obj.bind('mouseup', end);
        oThumb.obj[0].ontouchend = document.ontouchend = function(oEvent){
            $(document).unbind('mouseup');
            oThumb.obj.unbind('mouseup');
            end(oEvent.touches[0]);
        }
        return false;
    };      
    function wheel(oEvent){
        if(!(oContent.ratio >= 1)){
            oEvent = $.event.fix(oEvent || window.event);
            var iDelta = oEvent.wheelDelta ? oEvent.wheelDelta/120 : -oEvent.detail/3;
            iScroll -= iDelta * options.wheel;
            iScroll = Math.min((oContent[options.axis] - oViewport[options.axis]), Math.max(0, iScroll));
            oThumb.obj.css(sDirection, iScroll / oScrollbar.ratio);
            oContent.obj.css(sDirection, -iScroll);
            oEvent.preventDefault();
        };
    };
    function end(oEvent){
        $(document).unbind('mousemove', drag);
        $(document).unbind('mouseup', end);
        oThumb.obj.unbind('mouseup', end);
        document.ontouchmove = oThumb.obj[0].ontouchend = document.ontouchend = null;
        return false;
    };
    function drag(oEvent){
        if(!(oContent.ratio >= 1)){
            iPosition.now = Math.min((oTrack[options.axis] - oThumb[options.axis]), Math.max(0, (iPosition.start + ((sAxis ? oEvent.pageX : oEvent.pageY) - iMouse.start))));
            iScroll = iPosition.now * oScrollbar.ratio;
            oContent.obj.css(sDirection, -iScroll);
            oThumb.obj.css(sDirection, iPosition.now);;
        }
        return false;
    };

    return initialize();
};
 })(jQuery);

如果你能修改它来做到这一点，我将永远感激不已！

$('.overview:first').css({top: (($('.overview:first').height() - $('.viewport:first').height()) * (-1)) });
$('.thumb:first').css({top: $('.track:first').height() - $('.thumb:first').height()});