bug#42406: Mouse-wheel scrolling can be flickering

[Eli Zaretskii]

> From: Konrad Podczeck <konrad.podczeck@univie.ac.at>
> Date: Tue, 15 Dec 2020 20:31:19 +0100
> Cc: Alan Third <alan@idiocy.org>, 42406@debbugs.gnu.org
> 
> Performance does not degrade when only the two calls of wset_update_mode_line 
> you mentioned are commented out. However, with just commenting out these two 
> instances, I still have a scroll performance problem when scrolling by using 
> the scroll-bars. Could you also identify the instance concerning this?

Please be more specific: how do you scroll with the scroll bars, and
what kind of performance problem you experience as result of that?