Re: Have to run redraw-display manually

[Eli Zaretskii]

> From: Cos Chan <rosettas@gmail.com>
> Date: Tue, 21 Sep 2021 13:33:40 +0200
> 
> > My suggestion is not to do "tabs 4", it changes how the terminal
> > behaves regarding cursor motion.
> >
> >
> Clear and I will not do it. May I suggest adding this warning to the Emacs
> documents?

I would instead suggest that you report this as a bug, using the
"M-x report-emacs-bug" command.  It is possible that Emacs should be
able to automatically detect this situation somehow; currently it
doesn't, and I'm not an expert in this area to know if it could and
how.  Be sure to mention the "tabs 4" command in your report, as that
is the root cause.

> And I am pretty sure before I upgraded the Emacs there was no such issue.
> But I don't remember the version number of the Emacs I had.

It doesn't have to do anything with the Emacs version.  Emacs employs
a complicated algorithm to determine the least expensive sequence of
terminal commands to send to the terminal, given some cursor
movement.  The output depends on many factors, such as your terminal
screen dimensions etc.  So it could be that you never saw this before
due to factors other than the Emacs version.

It is also possible that this is related to the fact that we nowadays
use terminfo for finding out the terminal capabilities, whereas we
used termcap in older versions.

Reporting a bug will allow us to investigate this thoroughly and see
what can be done.

Thanks.