/* swap image */

var imgObjs = new Array();
var ii, jj, nn;

for(ii = 0; ii < imgNames.length; ii++)
  for(jj = 0; jj < imgStates.length; jj++){
    nn = imgNames[ii] + imgStates[jj];
    imgObjs[nn] = new Image();
    imgObjs[nn].src = imgPrefix + nn + imgSuffix;
  }

function swap(img, state){
  if(!document.images || !document.images[img]) return;
  document.images[img].src = imgObjs[img + state].src;
}

/* show/hide layers */

var old_menu = null, hide = null;
function hide_menu(id){
  if(id == null) return;
  obj = document.getElementById('dropnav_' + id);
  if(obj) obj.style.visibility = 'hidden';
  swap('gnav_' + id, '');
  clear_timeout();
}

function show_menu(id){
  if(old_menu) hide_menu(old_menu);
  obj = document.getElementById('dropnav_' + id);
  if(obj) obj.style.visibility = 'visible';
  swap('gnav_' + id, '_on');
  old_menu = id;
  clear_timeout();
}

function set_timeout(){
  hide = setTimeout("hide_menu('" + old_menu + "')",700);
}

function clear_timeout(){
  clearTimeout(hide);
}