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

[Eli Zaretskii]

> From: Ihor Radchenko <yantar92@posteo.net>
> Cc: monnier@iro.umontreal.ca, 64596@debbugs.gnu.org
> Date: Sun, 16 Jul 2023 07:28:09 +0000
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> BTW, is there any particular reason why windows_or_buffers_changed is
> >> not a queue of windows/buffer to be re-displayed?
> >
> > Why do we need such a queue, when the redisplay flags of buffers and
> > windows are supposed to tell us that already?
> 
> To not loop over all the existing windows and frames in xdisp.c:506
> redisplay branch.

Someone will have to demonstrate that this is worth our while.
Testing a single boolean flag is not an expensive operation, while
maintaining that queue also takes CPU.  Also, some changes in a window
can affect other windows on the same frame, for example if the window
is resized.

IOW, maybe it's a good idea and maybe it isn't, but it definitely
doesn't affect the most expensive parts of redisplay.