// JavaScript Document
// simple dynamic menu
//
// by Bill Weinman http://bw.org/
// Copyright (c) 2009 BHG LLC
//
// Version 1.0.1
// Created for Dynamic Menus course at lynda.com
//

// configuration variables
var timeout = 250; // milliseconds
var fadeSpeed = 500; // milliseconds
var useFade = true;

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

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

//lastOpacity: use 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 the 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 its 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 by a timer
// 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(msie) e.style.filter = 'alpha(opacity-' + value * 100 + ')';  // MS INternet Explorer
	else e.style.opacity = (value);  // Everyone else (standard DOM)
	
	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 25 ms increments
	var timer = 0;
	var i;
	
	state[id] = false;
	
	for( i = s; i >= 0 ; i-- ) {
		setTimeout( "setOpacity('" + id + "'," + ( i / s ) + ")", timer++ * fadeSpeed / s )
	}
}