// 2009 createe is Marko Walther

var lastContentMenu = null; // last visible content menu

/**
 * @param contents:string new contents
 */ 
function emptyContentFrame( contents ) {
  var frameElem = document.getElementById( 'content_iframe' );
  frameElem.src = contents;
}
/**
 * Shows or hides (no placeholder) DOM-element with given id.
 * @param id:string id of element to show
 * @param show:boolean  if <code>true</code> the element will be shown, if <code>false</code>
 *                      it will be hidden    
 */ 
function showContentMenu( id, show ) {
  var domElem = document.getElementById( id );
  // nothing to do if domElem already visible
  if( lastContentMenu == domElem )
    return;
  // hide last content menu
  if( lastContentMenu != null ) {
    lastContentMenu.style.display = 'none';
  }
  // show one
  if( show == true ) {
    domElem.style.display = 'block';
    lastContentMenu = domElem;
  }
  // hide one
  else {
    domElem.style.display = 'none';
    lastContentMenu = null;
  }
}