I think this is fine, but doing this check on initializing the arrows isn't great because if you resize the window, things will be messed up.

Perhaps you could you try:
(a) Putting an event listener on `mousedown` that does this check and calls `draggie.disable()` (or whatever it is) if `false` -- not sure if that would work.
(b) Do the check, but always make sure the arrows always show up if you're never going to apply draggable