var elementHeight;
var elementHeightTotal;
var elementHeightInvisible;
var elementScrollTop;
var elementScrollBottom;

var timer;

checkPageLoaded("updateScrollStatus('scrollText')");

function scroll(id,direction)
{
  if (direction == "up")
  {
    timer = setInterval("scrollUp('" + id + "')", 15);
  }
  
  if (direction == "down")
  {
    timer = setInterval("scrollDown('" + id + "')", 15); 
  }
}

function scrollDown(id)
{
  document.getElementById(id).scrollTop += 4;
  updateScrollStatus(id);
}

function scrollUp(id)
{
  document.getElementById(id).scrollTop -= 4;
  updateScrollStatus(id);
}

function scrollStop()
{
  clearInterval(timer);
}

function updateScrollStatus(id)
{
  if (document.getElementById(id))
  {
    upArrow = document.getElementById("scrollup");
    downArrow = document.getElementById("scrolldown");
    textelement = document.getElementById(id);
    
    elementHeight = textelement.offsetHeight;
    elementTotalHeight = textelement.scrollHeight;
    elementOffsetTop = textelement.scrollTop;
    elementoffsetBottom = (elementTotalHeight - (elementHeight + elementOffsetTop));
    
  //  alert("Element Height: " + elementHeight + "\nElement Total: " + elementTotalHeight + "\nElement ScrollTop: " + elementOffsetTop + "\nElement ScrollBottom: " + elementoffsetBottom);
    
    if (elementOffsetTop < 1)
    {
      upArrow.style.visibility = "hidden";
    }
    else
    {
      upArrow.style.visibility = "visible";
    }
    
    if (elementoffsetBottom < 1)
    {
      downArrow.style.visibility = "hidden";
    }
    else
    {
      downArrow.style.visibility = "visible";
    }
  }
}

function getValues()
{
  if (document.getElementById("scrollText"))
  {
    element = document.getElementById("scrollText");
    
    if (element.innerHeight && element.scrollMaxY) {// Firefox
      alert("Firefox");
		  elementHeightTotal = element.innerHeight + element.scrollMaxY;
	  } else if (element.scrollHeight > element.offsetHeight){ // all but Explorer Mac
      alert("Optie 2");
		  elementHeightTotal = element.scrollHeight;
	  } else { // works in Explorer 6 Strict, Mozilla (not FF) and Safari
      alert("Optie 3");
		  elementHeightTotal = element.offsetHeight;
    }

    elementHeight = element.offsetHeight;
    elementScrollTop = element.scrollTop;
    elementScrollBottom = (elementHeightTotal - (elementHeight + elementScrollTop));
    elementScrollBottom = (elementHeightTotal - (elementHeight + elementScrollTop));
    
    alert("Element Height: " + elementHeight + "\nElement Total: " + elementHeightTotal + "\nElement ScrollTop: " + elementScrollTop + "\nElement ScrollBottom: " + elementScrollBottom);
  } else {
    alert("Fout");
  }
}