Re: Display of undisplayable characters: \U01F3A8 instead of diamond

[Alan Mackenzie <acm@muc.de>]

Hello, Eli.

On Fri, Sep 02, 2022 at 14:29:12 +0300, Eli Zaretskii wrote:
> > Date: Fri, 2 Sep 2022 11:12:32 +0000
> > Cc: Richard Stallman <rms@gnu.org>, eliz@gnu.org, emacs-devel@gnu.org
> > From: Alan Mackenzie <acm@muc.de>

[ .... ]

> > I agree with Richard that there should be an option for displaying
> > characters outside of the current font as "�" rather than "\u2022".

> I already explained how to set that up, so what exactly does the
> "should be" part here want to say?

The way you explained involves hacking Lisp and finding out precise
character ranges.  That's a lot different from being able just to set an
option.

> There is already such a way in Emacs.  Just use it, if that's what you
> want.

There appears to be no easy way to get the old behaviour back, where
characters undisplayable on the console got displayed with \ufffd
instead.  You've characterised this old behaviour as a bug, but in the
preferences of two actual Linux console users (Richard and myself), the
solution is not better than the bug.

> > It is a feature of the Linux console that all such characters are
> > displayed that way.

> That feature provides no way of using it via standard terminfo
> interfaces.  Heck, even the way to ask the console which characters it
> supports is a kludge specific to that console!

Yes, I remember looking into that to try to find a way.  Somebody
brighter than me clearly managed it.  :-)

> > There is no possibility of any character causing an undefined
> > action.

> Famous last words.  (And we don't send characters to the console, we
> send bytes.)

OK, bytes.  Have there been any untoward effects reported, by sending
valid Unicode strings of bytes to the Linux console?

-- 
Alan Mackenzie (Nuremberg, Germany).