bug#42406: Mouse-wheel scrolling can be flickering

[Eli Zaretskii]

> Cc: konrad.podczeck@univie.ac.at, alan@idiocy.org, 42406@debbugs.gnu.org
> From: martin rudalics <rudalics@gmx.at>
> Date: Wed, 16 Dec 2020 17:53:37 +0100
> 
>  >> I forgot how Emacs precisely handles that.  Maybe Eli can tell.
>  >
>  > See scroll-bar-toolkit-scroll.  Basically, it calls
>  > scroll-up/scroll-down.
> 
> Then something else must come into play here.  I don't see where
> 'scroll-bar-toolkit-scroll' forces a mode line update.

AFAIR, scroll-up does.