bug#42406: Mouse-wheel scrolling can be flickering

[Konrad Podczeck]

> Am 14.12.2020 um 17:17 schrieb Eli Zaretskii <eliz@gnu.org>:
> 
>> 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.
 
Which bug could I encounter, for example?