//These functions collectively make the cascading menu work

/*'oldWhich' stores the value of the most recent menu
heading to make the function call 'show_hide_sub'
for the sake of the next menu heading which will call the
function so that the function essentially knows which
sub-menu to hide and which to show.
'timerId' is an integer variable which serves as an identifier
for the window.setTimeout method. Upon mouse out of either the
main menu or sub menu, a timer is set so that it expires
after 'expireTime' milliseconds, at which point it will hide the 
most recently shown sub menu (which is determined 
by 'oldWhich.' On mouse over of either a sub menu or main menu, the
timer is cleared and the sub menu indicated by oldWhich remains visible
*/

var oldWhich;
var oldSubMenu;
var timerId;
var expireTime = 500;

/*function to show or hide the sub-menu of the respective menu heading determined by 'which,' the argument passed by
and that corresponds to the menu heading making the function call. The argument 'level' determines which level of the menu is
making the call, either the main level, which we shall call the 'first' level, or the first sub menu level which we shall call 
the 'second' level (note: the second sub menu level will be denoted as the 'third' level for descriptive purposes although that 
level is not so pertinent to this function). The function first clears the timeout function which would otherwise hide the sub 
level menus. It then determines which menu level is making the call and sets the global variable 'secLevel' accordingly. If the 
level making the call is the second level then the function checks the existence of 'secOldWhich' which represents the previous 
third level menu displayed and upon verification of its existence it is hidden. It then checks to see if 'which' is null. Some 
elements of the second level call this function with a value of null. Any element that calls with 'which' as null does not have
a third level menu and therefore should only hide the previously displayed third level menu (this is of course taken care of by
the previous 'if' statement described above). So if 'which' is not null, then the third level menu <div> represented by which
is set to visible and the global variable 'secOldWhich' is set to 'which', effectively storing a reference to the third level menu 
<div> which was just displayed for the sake of the next time this function is called. If the menu level that is making the call('level')
is the first level, then the existence of 'secOldWhich' and 'oldWhich' are verified and the elements they represent 
are hidden. Then the <div> element respresented by 'which' is set to visible and 'oldWhich' is set to 'which' for the sake of the next 
time the function is called.
*/

function show_hide_sub(which)
{
	clearTimeout(timerId);
	
	var subMenu = which + "Menu";
		
	if(oldWhich)
	{
		document.getElementById(oldWhich).style.backgroundColor = "#6699cc";
		document.getElementById(oldSubMenu).style.visibility = "hidden";
	}
		
	navTwo(which);
	
	if( subMenu )
		document.getElementById(subMenu).style.visibility = "visible";
	
	oldWhich = which;
	oldSubMenu = subMenu;
}

/*function determines whether the mouse is over any menu
element and calls or clears the timeout function accordingly
first level menu items call this function on mouse out
second level menu items do not call this function
third level menu items call this on over and out.
AS A GENERAL RULE (not that this has not been tested and proven, it is only conjecture), IT SEEMS THAT
FOR ANY CASCADING MENU SYSTEM WITH 'N' LEVELS, ONLY LEVEL ONE AND LEVEL 'N' SHOULD CALL THIS FUNCTION.
LEVEL ONE SHOULD CALL IT ON MOUSE OUT AND LEVEL 'N' SHOULD CALL IT ON MOUSE OVER AND OUT. ALL OTHER
MENU LEVELS SHOULD ONLY CALL THE ABOVE FUNCTION ON MOUSE OVER (also note that this rule only applies to
cascading menus built on this methodology).
*/

function over_sub_menu(what)
{
	if(what == "over")
		clearTimeout(timerId);
	if(what == "out")
		timerId = setTimeout("do_timeout()",expireTime);
}

/*function handles the timeout of the menu system which basically
is set so that all sub level menu items disappear after a time of
'timerId' milliseconds unless the timeout function is cleared by one of the functions above. The conditions for clearing
the timeout are noted in the function descriptions above.
*/

function do_timeout()
{
	document.getElementById(oldWhich).style.backgroundColor = "#6699cc";
	document.getElementById(oldSubMenu).style.visibility = "hidden";
}

/*function sets the background color of the first level nav item which calls it*/

function navTwo(which)
{
	document.getElementById(which).style.backgroundColor = "#84875f";
}