function tree_toggleNode (nodeID) {
  var objNode = document.getElementById (nodeID);
  
  if (objNode.style.display == "" || objNode.style.display == "block")
    objNode.style.display = "none";
  else
    objNode.style.display = "block";
}

function tree_showNode (nodeID) {
  var objNode = document.getElementById (nodeID);
  objNode.style.display = "block";
}

function tree_hideNode (nodeID) {
  var objNode = document.getElementById (nodeID);
  objNode.style.display = "none";
}