//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("pw_content").offsetHeight;	
    scroller.contH = document.getElementById("pw_container").offsetHeight;	
    scroller.scrollAreaH = document.getElementById("pw_scrollArea").offsetHeight;      

    //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;

    document.getElementById("scroller").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("scroller"),null,0,0,-1,scroller.scrollDist);   

    //add ondrag function

    document.getElementById("scroller").onDrag = function (x,y) {
      var scrollY = parseInt(document.getElementById("scroller").style.top);
      var docY = 0 - (scrollY * (scroller.docH - scroller.contH) / scroller.scrollDist);
      document.getElementById("pw_content").style.top = docY + "px";
    }
  }
}

var nowOnload = window.onload; 
    window.onload = function () {
        scroller.init();
        if(nowOnload != null && typeof(nowOnload) == 'function') {
            nowOnload();
        }
    }