var DDSPEED = 10;
var DDTIMER = 15;

// main function to handle the mouse events //
function rolloverImage(id, image, z){
  var m = document.getElementById(id); // get the element that is passed in by 'id' -- the menu item div
  var x = "url(" + image + ")";
  m.style.backgroundImage = x;
  var s = 'sub' + id;
  var sb = document.getElementById(s);
  clearInterval(sb.timer);
  if (z == 1){
    sb.style.visibility = "visible";
  } else {
    sb.style.visibility = "hidden";
  }
}

function menuDropdown(id, z){
   var s = 'sub' + id;
   var sb = document.getElementById(s);
   clearInterval(sb.timer);
   if (z == 1){
      sb.style.visibility = "visible";
   } else {
      sb.style.visibility = "hidden";
   }
}

function rolloverImageOnly(id, image){
  var m = document.getElementById(id);
  var x = "url(" + image + ")";
  m.style.backgroundImage = x;
}

// collapse the menu //
function ddCollapse(c){
  c.timer = setInterval(function(){ddSlide(c,-1)},DDTIMER);
}

// cancel the collapse if a user rolls over the dropdown //
function cancelHide(id){
  var h = document.getElementById(id + '-ddheader');
  var c = document.getElementById(id + '-ddcontent');
  clearTimeout(h.timer);
  clearInterval(c.timer);
  if(c.offsetHeight < c.maxh){
    c.timer = setInterval(function(){ddSlide(c,1)},DDTIMER);
  }
}

// incrementally expand/contract the dropdown and change the opacity //
function ddSlide(c,d){
  var currh = c.offsetHeight;
  var dist;
  if(d == 1){
    dist = (Math.round((c.maxh - currh) / DDSPEED));
  }else{
    dist = (Math.round(currh / DDSPEED));
  }
  if(dist <= 1 && d == 1){
    dist = 1;
  }
  c.style.height = currh + (dist * d) + 'px';
  c.style.opacity = currh / c.maxh;
  c.style.filter = 'alpha(opacity=' + (currh * 100 / c.maxh) + ')';
  if((currh < 2 && d != 1) || (currh > (c.maxh - 2) && d == 1)){
    clearInterval(c.timer);
  }
}