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

//configuration variables
var timeout   = 100; //milliseconds
var fadeSpeed = 250; //milliseconds
var useFade   = false;

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

//state array -- by id, value = active, falce = 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 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 multiple t
	
	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 );
	var timer = 0;
	var i;
	
	state[id] = false;
	
	for( i = s; i >= 0 ; i-- ) {
		setTimeout( "setOpacity('" + id + "'," + ( i / s ) + ")", timer++ * fadeSpeed / s )
	}
}