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: Mon, 17 Jul 2023 12:00:02 +0000
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> This does not help the confusion, unfortunately.
> >> Or maybe the terms "redisplay" and "update" should be explained better
> >> somewhere near the top of xdisp.c. They clearly have different meaning,
> >> but not for untrained eye.
> >
> > "Update" is the general name of the 3rd step of "redisplay cycle".  It
> > takes its name from the function which enters this step: update_frame.
> 
> May someone then detail these steps in the top commentary in xdisp.c +
> highlight that redisplay term is generally used when deciding if we need
> to update.

It's already in the large commentary at the beginning of xdisp.c
(search for "update_window" to find the description of "update").  It
just "drowns" in the sea of the information there

> And update is an actual process of putting desired matrix onto the
> glass.

That's a very simplistic description of what "update" does.  Even the
comment in xdisp.c says more.