// Dynamic Menu Javascript 
// Orignally written by Bill Weinman http:/www.bw.org/
// Copyright (C) 2009 BHG LLC
//
// Version 1.01
// Use Authorised as part of Lynda Dymanic Menus Course
//

// Configuration Variables
var timeout = 250;  // ms
var fadeSpeed = 500; //ms
var useFade = true;

// timers array
var timers = new Array();

// state array -- by id, value = active false = inactive
var state = new Array();

// lastOpacity: used to prevent multiple timers from making the fade flicker
var lastOpacity = new Array();

// MSIE has its own way of setting opacity, so we have to detect it
// All other major browsers support the standard DOM opacity property
var MSIE = false;
if ( navigator.appName == "Microsoft Internet Explorer") msie = true;

// entry point - set element to visible and clear timers
function setMenu( id )
{
	var e = document.getElementById(id);
	e.style.visibility = "visible";
	state[id] = true;
	setOpacity( id, 1 );
	if(timers[id]) {
		clearTimeout(timers[id]);
		timers[id] = "undefined";
	}
}
// set element to hidden and reset its opacity
// typically called as a time
// may be used as an entry point to bypass timers and fades
function hideMenu( id )
{
	var e = document.getElementById(id);
	state[id] = false;
	e.style.visibility = "hidden";
	if(useFade) setOpacity( id, 1 );
}
// entry point: hide the menu using fade if enabled
function clearMenu( id )
{
	if(useFade) timers[id] = setTimeout( 'fadeMenu( "' + id + '")', timeout );
	else timers[id] = setTimeout( 'hideMenu( "' + id + '")', timeout );
}
// set the opacity
// special support for MSIE
function setOpacity( id, value )
{
	var e = document.getElementById(id);
	
	if(state[id]) value = 1;      // menu fade was interrupted
	else if(lastOpacity[id] && (lastOpacity[id] < value)) value = lastOpacity[id]; // prevents flicker if multiple timers
																			   
	if(msie) e.style.filter = 'alpha(opacity=' + value * 100 + ')';
	else e.style.opacity = (value);
	
	if(value == 0) hideMenu( id );    // when all faded, reset the menu state
	lastOpacity[id] = value;
}
// fade a menu
// typically called by a timer
function fadeMenu( id )
{
	var start = 0;
	var end = 0;
	var s = Math.round ( fadeSpeed / 25 );   //fade in 25ms increments
	var timer = 0;
	var i;
	
	state[id] = false;
	
	for ( i = s;  i >= 0 ; i-- ) {
		setTimeout( "setOpacity('" + id + "'," + (i / s) + ")", timer++ * fadeSpeed / s )
	}
}