var TimeToFade = 500.0;

/*
function fade(eid, start_opacity, final_opacity)
{
   if(document.getElementById(eid) == null)
   {
      return;
   }

   var nr_steps = Math.ceil(TimeToFade/33);
   var opacity_step = Math.round((final_opacity - start_opacity) / nr_steps * 100)/100;
   var new_opacity = start_opacity + opacity_step;
   
   for(step=0; step<=nr_steps; step++)
   {
      setTimeout("animateFade('" + eid + "', " + new_opacity + ")", 33);
      
      old_content = document.getElementById('debug_div').innerHTML;
      old_opacity = new_opacity
      new_opacity = Math.min(1, Math.max(0, old_opacity + opacity_step));
      document.getElementById('debug_div').innerHTML=old_content + " > " + new_opacity;
   }
}

function animateFade(eid, new_opacity)
{
   var element = document.getElementById(eid);
   element.style.opacity = new_opacity;
   element.style.filter = 'alpha(opacity = ' + (new_opacity*100) + ')';
   //document.getElementById('debug_div').innerHTML=new_opacity;
}
*/

var TimeToFade = 1000.0;

function fade(eid)
{
  var element = document.getElementById(eid);
  if(element == null)
    return;
   
  if(element.FadeState == null)
  {
    if(element.style.opacity == null
        || element.style.opacity == ''
        || element.style.opacity == '1')
    {
      element.FadeState = 2;
    }
    else
    {
      element.FadeState = -2;
    }
  }
   
  if(element.FadeState == 1 || element.FadeState == -1)
  {
    element.FadeState = element.FadeState == 1 ? -1 : 1;
    element.FadeTimeLeft = TimeToFade - element.FadeTimeLeft;
  }
  else
  {
    element.FadeState = element.FadeState == 2 ? 1 : -1;
    element.FadeTimeLeft = TimeToFade;
    setTimeout("animateFade(" + new Date().getTime() + ",'" + eid + "')", 33);
  }  
}

function animateFade(lastTick, eid)
{  
  var curTick = new Date().getTime();
  var elapsedTicks = curTick - lastTick;
 
  var element = document.getElementById(eid);
 
  if(element.FadeTimeLeft <= elapsedTicks)
  {
    element.style.opacity = element.FadeState == 1 ? '1' : '0';
    element.style.filter = 'alpha(opacity = '
        + (element.FadeState == 1 ? '100' : '0') + ')';
    element.FadeState = element.FadeState == 1 ? 2 : -2;
    return;
  }
 
  element.FadeTimeLeft -= elapsedTicks;
  var newOpVal = element.FadeTimeLeft/TimeToFade;
  if(element.FadeState == 1)
    newOpVal = 1 - newOpVal;

  element.style.opacity = newOpVal;
  element.style.filter = 'alpha(opacity = ' + (newOpVal*100) + ')';
 
  setTimeout("animateFade(" + curTick + ",'" + eid + "')", 33);
}