/* slouzi k rozklikavani menu v levem sloupci */

function swap_image(id)
{
    image_menu=document.getElementById(id);
    var old_src=image_menu.src;
    var match_string_minus=/minus/;
    var match_string_plus=/plus/;
    if(old_src.search(match_string_minus)!=-1)
    {
        var temp=old_src;
        new_src=temp.replace(match_string_minus,"plus");
    }
    if(old_src.search(match_string_plus)!=-1)
    {
        var temp=old_src;
        new_src=temp.replace(match_string_plus,"minus");
    }	 
    image_menu.src=new_src;
}
  
function switch_menu(id)
{   
    var layer_id="tree_layer"+id;
    var tree_item_id="tree_item"+id;
    var kat_layer=document.getElementById(layer_id);
    if(kat_layer.style.display=="inline")
    {
        kat_layer.style.display="none";
        swap_image(tree_item_id);	 
    }
    else
    {
        kat_layer.style.display="inline";
        swap_image(tree_item_id);	 
    }   
}