Stopping scroll if user or other system scrolls screen mid-smooth scroll

[stephan-nordnes-eriksen]

This fix checks if a user, or some other system, has changed the scroll position during the ongoing scroll, and if so, stops the current smooth scroll.

I am not 100% sure if this is the specified behaviour for the smooth scroll, but it makes sense to me.

[stephan-nordnes-eriksen]

Note;

There are two things I am not sure I did right, so if someone with a bit better understanding of this library could check, that would be great.

1

I am monitoring the document.body's scrollLeft and scrollTop properties. It might be some other element which should be monitored.

2

I am checking context.startX and context.startY against their previous value, which might not be necessary.

[stephan-nordnes-eriksen]

Interesting: I also found that the method findScrollableParent sometimes gives the wrong element. (gives different parent for two li elements of same ul). This particular case makes the code above break, so please don't merge this yet.

[rakusai]

I agree that scrolling should be stopped if scroll function has been called again.
This seems default behavior of Chrome and Firefox.
I'm not sure that this should be stopped by the user action.