bug#56695: A new and old font problem with Arabic

[Eli Zaretskii]

> Date: Sun, 24 Jul 2022 09:24:45 +0200 (CEST)
> From: "fr_ml@t-online.de" <fr_ml@t-online.de>
> Cc: "56695@debbugs.gnu.org" <56695@debbugs.gnu.org>
> 
> (set-fontset-font "fontset-default" 'arabic "DejaVu Sans Mono") das scheint 
> zu gehen!
> 
> I tested it with:
> --
> (set-fontset-font "fontset-default" 'arabic "DejaVu Sans Mono")
> --
> in the init file. (I hope this is right way?)

Yes, this is the right way.

> It works, Emacs uses the font correctly.
> And it seems that the positioning is then much better. The old problem is 
> still there but not so often.

Does this mean we can close this bug?

> What I also noticed:
> When I change the font with the same function 'set-fontset-font' but without 
> restarting Emacs I get the old positioning problem immediately or after some 
> typing and testing.

This is expected: Emacs caches the results of previous text-shaping.
You should invoke

  M-: (clear-composition-cache) RET

to force Emacs to forget the old text-shaping results.