bug#21682: 25.0.50; display bug

[Eli Zaretskii]

> From: Andreas Schwab <schwab@suse.de>
> Date: Thu, 15 Oct 2015 09:04:24 +0200
> Cc: 21682@debbugs.gnu.org
> 
> Richard Stallman <rms@gnu.org> writes:
> 
> > Emacs needs to cope with it, unless we can get it fixed.
> 
> Emacs cannot know how characters are drawn on a tty.

Does that mean you understood what causes Richard's problem?  If so,
can you explain?

I thought asking Richard for dribble files in both cases, but if you
already understand what's going on, there would be no need.

I actually don't understand why we have auto-composition-mode turned
on for TTY frames, and where do we take the data for composing
characters there (there's no font back-end).  Kenichi, can you
explain, please?

Thanks.