How to distinguish scrolling by mouse from scrolling programmatically in JavaScript?

You could use the .hover(): function to stop the scrolling when the mouse is over the scrollbox element:

http://jsfiddle.net/bGHAH/1/

setInterval(function(){
    if(!mouseover)
    {
       $('#scrollbox').scrollLeft($('#scrollbox').scrollLeft()+1);
    }
}, 50);

var mouseover = false;
$('#scrollbox').hover(function(){
    mouseover = true;
},function(){
    mouseover = false;    
});

---

Edit

Based on your comments I managed to find a jquery plugin from the following site: special scroll events for jquery.

This plugin contains an event which attempts to determine whether scrolling has stopped based on the period of time that has elapsed between the last scroll step and the time the check was made.

To get this to work I needed to slow your interval to just over the latency used by the plugin which worked out to be 310 milliseconds. Doing this meant I had to increase the scroll step to keep it visibly moving.

Here is the link:

http://jsfiddle.net/EWACn/1/

and here is the code:

var stopAutoScroll = false;

$(document).ready(function(){

setInterval(function(){
    if(!stopAutoScroll)
    {
       $('#status').html('scrolling');
       $('#scrollbox').scrollLeft($('#scrollbox').scrollLeft()+10);
    }else{
       $('#status').html('not scrolling');
    }
}, 310);

$('#scrollbox').bind('scrollstart', function(e){
    stopAutoScroll = true;
});

$('#scrollbox').bind('scrollstop', function(e){
    stopAutoScroll = false;
});

});

Hope this helps.

For FF (Mozilla):

document.addEventListener('DOMMouseScroll', handler, false);

For IE, Opera and Chrome:

document.onmousewheel = handler;