// csss-menu.js
// Dynamic menu for csss1970.ca web site
//
// by Bill Weinman | adapted by Richard Mayer
// Copyright (c) 2009 BHG LLC | 2010 as adapted by Richard Mayer
//
// Version 1.0
// Created for csss1970.ca web site
//

// configuration variables
var timeout = 250; // milliseconds
var fadeSpeed = 250; // milliseconds
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 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 DMO)
	
	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 )
	}
}