// bw-menu.js

// simple dynamic menu

//

// by Bill Weinman  http://bw.org/

// Copyright (c) 2009 BHG LLC

//

// Version 1.0.2

// 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: 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 timers set

    

    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 25ms increments

    var timer = 0;

    var i;



    state[id] = false;



    for( i = s; i >= 0 ; i-- ) {

        setTimeout( "setOpacity('" + id + "'," + ( i / s ) + ")", timer++ * fadeSpeed / s )

    }

}