bug#42406: Mouse-wheel scrolling can be flickering

[Eli Zaretskii]

> From: Konrad Podczeck <konrad.podczeck@univie.ac.at>
> Date: Mon, 14 Dec 2020 01:20:39 +0100
> Cc: Eli Zaretskii <eliz@gnu.org>,
>  42406@debbugs.gnu.org
> 
> In view of the comments made by Eli, I made a shoot in the dark, and, in 
> window.c, commented out the occurrences of wset_update_mode_line on lines 
> 1850, 4011, 5630, 5819, 6079, as well as the respective line after the three 
> statements lines where "Bug#15957" is written. With these (actually I have 
> not testes which of these (out-commentings are relevant) the problem has 
> completely gone. I am aware that this is not a real solution, but it shows 
> that there is some room. Which are the risks caused by these changes of the 
> code?

As explained in my other message, avoiding to call
wset_update_mode_line will cause subtle redisplay bugs.