Re: Debouncing slow mode line constructs (was: Emacs design and architecture. How about copy-on-write?)

[Eli Zaretskii]

> From: Ihor Radchenko <yantar92@posteo.net>
> Cc: dmitry@gutov.dev, luangruo@yahoo.com, acm@muc.de, incal@dataswamp.org,
>  emacs-devel@gnu.org
> Date: Fri, 22 Sep 2023 13:19:42 +0000
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> redisplay optimizations may decide to not refresh the mode-line when
> >> typing.
> >
> > If they do, it's a bug.
> 
> You are right. Typing appears to trigger mode-line redisplay.
> What I thought is a redisplay optimization is different - `vc-mode'
> variable used to display VC status is not updated on every redisplay.
> Instead, it is modified when visiting a file and when saving a file.
> The end result is the same - VC status is not always up-to-date.
> 
> Similar approach is often used by other well-optimized mode-line
> constructs, leading to sometimes-outdated mode-line.

These are not problems with display, these are problems with the modes
which define and calculate the respective mode-line variables.