//We wrap all the code in an object so that it doesn't interfere with any other code
var scroller = {
  init:   function() {

    //collect the variables
    scroller.docH = document.getElementById("mainContent").offsetHeight;
    scroller.contH = document.getElementById("mainContentContainer").offsetHeight;
    scroller.scrollAreaH = document.getElementById("scrollerBase").offsetHeight;
      

	//se o texto não precisa de scroll,
	//escondo a scrollbar: 
	if(scroller.docH < scroller.contH) {
		document.getElementById("scrollerBase").style.visibility = 'hidden';		
	} else {
		document.getElementById("scrollerBase").style.visibility = 'visible';

    //calculate height of scroller and resize the scroller div
    //(however, we make sure that it isn't to small for long pages)
    //scroller.scrollH = (scroller.contH * scroller.scrollAreaH) / scroller.docH;
    //if(scroller.scrollH < 15) scroller.scrollH = 15;
	scroller.scrollH = 40;
    document.getElementById("scrollerBar").style.height = Math.round(scroller.scrollH) + "px";

    
    //what is the effective scroll distance once the scoller's height has been taken into account
    scroller.scrollDist = Math.round(scroller.scrollAreaH-scroller.scrollH);
    
    //make the scroller div draggable
    Drag.init(document.getElementById("scrollerBar"),null,0,0,-1,scroller.scrollDist);
    
    //add ondrag function
    document.getElementById("scrollerBar").onDrag = function (x,y) {
      var scrollY = parseInt(document.getElementById("scrollerBar").style.top);
      var docY = 0 - (scrollY * (scroller.docH - scroller.contH) / scroller.scrollDist);
      document.getElementById("mainContent").style.top = docY + "px";
   		 }
 	 }
  }
}