/* Step variazione del fading (sulla base di un alpha 100)*/
var FADING_SPEED = 5;




function fadeInElement(target,secs,callback)
{
    var msg = document.getElementById(target);
    var millisecs = (secs*1000) / (100/FADING_SPEED);

    if( msg )
    {
        msg.alpha = 0;
        msg.timer = setInterval(function(){fadeElement(target,1,callback)},millisecs);
    }
}

function fadeOutElement(target,secs,callback)
{
    var msg = document.getElementById(target);
    var millisecs = (secs*1000) / (100/FADING_SPEED);
    if( msg )
    {
        msg.alpha = 100;
        msg.timer = setInterval(function(){fadeElement(target,0,callback)},millisecs);
    }
}


function fadeElement(target,fadeDir,callback)
{
    if(fadeDir == null)
    {
        fadeDir = 1;
    }

    var msg = document.getElementById(target);
    var value;

    if(fadeDir == 1)
    {
        /* Fade IN */
        value = msg.alpha + FADING_SPEED;
    }
    else
    {
        /* Fade OUT */
        value = msg.alpha - FADING_SPEED;
    }

    msg.alpha = value;
    msg.style.opacity = (value / 100);
    msg.style.filter = 'alpha(opacity=' + value + ')';

    if(value >= 99)
    {
        clearInterval(msg.timer);
        msg.timer = null;
        if( callback != null)
        {
            callback()
        }
    }
    else if(value <= 1)
    {
        clearInterval(msg.timer);
        if( callback != null)
        {
            callback()
        }
    }
}