bug#64596: 30.0.50; On FIXME: in src/buffer.c:1481 (force-mode-line-update)

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: yantar92@posteo.net,  64596@debbugs.gnu.org
> Date: Fri, 14 Jul 2023 13:38:11 -0400
> 
> > No, one variable is not enough -- it will never tell us which of the
> > potential flags or settings of the flag requires to be reinstated.  We
> > need to be able to investigate this at a finer granularity.
> 
> I doubt it.
> 
> What we need in order to investigate is a somewhat reproducible test
> case and for that we need the bug to be exposed to as many users as
> possible to increase the chance that one of them bumps into
> a good recipe.
> 
> The variable is not used to investigate, but to make it ethical to
> expose users to those potential bugs because they can set the var to
> recover the old behavior as soon as they're tired of playing the
> guinea pig.

That's not what I had in mind when I proposed this approach.

What I had in mind was to investigate the need for every one of the
variables we use to disable redisplay optimizations in the various
cases: the prevent_redisplay_optimizations_p flag, the
update_mode_lines variable, the windows_or_buffers_changed variable,
etc. -- in the places in xdisp.c where these are heeded.  The purpose
was to understand better which ones should be used where and why.
This cannot be done with a single variable.

So if you want a single variable for some "ethical"
pseudo-investigation, I guess we deeply disagree here.  I'm not
interested in such "investigation".