How can I differentiate a manual scroll (via mousewheel/scrollbar) from a Javascript/jQuery scroll?

Question

UPDATE:

Here is a jsbin example demonstrating the problem.

UPDATE 2:
And here is the fixed version thanks to fudgey.

---

Bas

Answer 1

I had your same issue some a few days ago.You shouldn't be using jquery's animate function if you want to obtain that result, you have to simulate the animation using a polling function.

I made this class which is supposed to provide a smooth scrolldown when ScrollDown.slow() is called.

ScrollDown.current=$(window).scrollTop();
ScrollDown.lastValue;
ScrollDown.lastType;
ScrollDown.enabled=true;
ScrollDown.custom=function(value,rate){  //let's say value==='bottom' and rate=10
    if(value==='bottom'){
        value=$(document).height()-$(window).height();
    }
    ScrollDown.current=$(window).scrollTop();
    ScrollDown.lastValue=value;
    (function poll(){
        setTimeout(function(){
            var prev=$(window).scrollTop();  //This is the critical part
            /*I'm saving again the scroll position of the window, remember
            10 ms have passed since the polling has started
            At this rate, if the user will scroll up for down pre!==ScrollDown.current
            And that means I have to stop scrolling.*/
            ScrollDown.current++; //increasing the scroll variable so that it keeps scrolling
            $(window).scrollTop(ScrollDown.current);
            if(ScrollDown.currentScrollDown.current-1 
                and at the next poll() the scrolling will stop 
                because ScrollDown.enabled will bet set to false by ScrollDown.stop()*/
                    ScrollDown.stop();
                }
                poll();
            }
        },rate);
    })();
};

ScrollDown.stop=function(){
    ScrollDown.enabled=false;
};

ScrollDown.continue=function(){
    ScrollDown.enabled=true;
    switch (ScrollDown.lastType){
        case "fast":
            ScrollDown.fast(ScrollDown.lastValue);
            break;
        case "normal":
            ScrollDown.normal(ScrollDown.lastValue);
            break;
        case "slow":
            ScrollDown.slow(ScrollDown.lastValue);
            break;
    }
};

ScrollDown.fast=function(value){
    if(!ScrollDown.enabled){
        ScrollDown.continue();
    }else{
        ScrollDown.lastType='fast';
        ScrollDown.custom(value,1);
    }
};
ScrollDown.normal=function(value){
    if(!ScrollDown.enabled){
        ScrollDown.continue();
    }else{
        ScrollDown.lastType='normal';
        ScrollDown.custom(value,10);
    }
};
ScrollDown.slow=function(value){
    if(!ScrollDown.enabled){
        ScrollDown.continue();
    }else{
        ScrollDown.lastType='slow';
        ScrollDown.custom(value,50);
    }
};
function ScrollDown(){}

So if you were to call ScrollDown.slow('bottom') it would start scrolling slowly till it reaches the bottom of your page unless you scroll up or down manually, then it stops.