// bw-menu.js
// simple dynamic menu with fades
//
// by Bill Weinman   http://bw.org/
// Copyright (c) 2009 BHG LLC
//
// Version 1.0.1
// Created for Dynamic Menus course at lynda.com
// Used by permission (see course)
//

// configuration variables
var timeout=100; //milliseconds
var fadespeed=400; //milliseconds
var useFade=true;

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

// state array -- by id - 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 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 fades
	
	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, hide 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 )
	}
}
// line 83 sets fadespeed in 25ms increments