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 19:51:39 +0100
> 
>  >> 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.
> 
> 'scroll-up' runs scroll_command and nothing else.

Yes.  And scroll_command calls window_scroll, and that calls
window_scroll_pixel_based, where we have these wset_update_mode_line
calls about which you asked.  Or what am I missing?