var ScrollSpy=new Class({Implements:[Options,Events],options:{min:0,mode:'vertical',max:0,container:window,onEnter:$empty,onLeave:$empty,onTick:$empty},initialize:function(options){this.setOptions(options);this.container=$(this.options.container);this.enters=this.leaves=0;this.max=this.options.max;if(this.max==0)
{var ss=this.container.getScrollSize();this.max=this.options.mode=='vertical'?ss.y:ss.x;}
this.addListener();},addListener:function(){this.inside=false;this.container.addEvent('scroll',function(){var position=this.container.getScroll();var xy=this.options.mode=='vertical'?position.y:position.x;if(xy>=this.options.min&&xy<=this.max){if(!this.inside){this.inside=true;this.enters++;this.fireEvent('enter',[position,this.enters]);}
this.fireEvent('tick',[position,this.inside,this.enters,this.leaves]);}
else{if(this.inside)
{this.inside=false;this.leaves++;this.fireEvent('leave',[position,this.leaves]);}}}.bind(this));}});