/**
     @param obj
     @param state if -1: toggle, 0: hide, 1: visible
   */
  function toggleVisibility( obj, state )
  {
      if (document.layers)
      {
        if (state!=0 && (obj.display=='none' || state==1))
          obj.display='';
        else
          obj.display='none';
    }
    else
    {
        if (state!=0 && (obj.style.display=='none' || state==1))
          obj.style.display='';
        else
          obj.style.display='none';
      }
  }

  function toggleRowsVisibility( obj, state )
  {
    obj = obj.firstChild; //td
    obj = obj.firstChild; //table
    if (obj.tagName == 'TBODY') obj = obj.firstChild;

    for (var i=0; i<obj.rows.length; i++)
    {
      toggleVisibility(obj.rows[i], state);
    }
  }
  
  function categoryToggle( catid, save )
  {
  	var state=1;
  	if (save)
  	{
        c = readCookie('typotex_bookshelf');
		if (c != null && c[0]!=' ') c = ' '+c;
        if (c==null)
        {
            c = ' '+catid+',';
        }
        else if (c.match(new RegExp(' '+catid+','))!=null)
        {
            c = c.replace(new RegExp(' '+catid+',', 'g'), '');
            state = 0;
        }
        else
        {
            c = c + ' '+catid+',';
        }
        createCookie('typotex_bookshelf', c, 7);
	}
	
    var obj = document.getElementById( 'cattree-'+catid );
    if (obj)
    {
      toggleRowsVisibility( obj, state );
    }
    obj = document.getElementById( 'booktree-'+catid );
    if (obj)
    {
      toggleVisibility( obj, state );
    }
	
  }

  function initCategories(c)
  {
	if (c==undefined || c.length==0) return;
  	s = c.split(',');
  	for (var i=0; i<s.length; i++)
  	{
  		catid=parseInt(s[i]);
  		categoryToggle(catid, false);
  	}
  	createCookie('typotex_bookshelf', c, 7);
  }