Re: Can watermarking Unicode text using invisible differences sneak through Emacs, or can Emacs detect it?

[Eli Zaretskii]

> From: Richard Stallman <rms@gnu.org>
> Cc: psainty@orcon.net.nz, luangruo@yahoo.com, emacs-devel@gnu.org,
>       kevin.legouguec@gmail.com
> Date: Fri, 28 Jan 2022 08:04:49 -0500
> 
>     > The most widely known example is Latin characters with diacritics, such 
> as ç and à.
> 
> Since my terminal handles many of those characters, they work ok for
> me.  But there are some it does not support.  Many Vietnamese
> characters, for instance.
> 
> If this feature is implemented to handle ligatures, it could handle
> the letters with diacritics too.  That would be as easy as populating
> the table of the sequences they stand for.

IIUC what you mean by "this feature", we already have that in
latin1-disp.el.  It just isn't automatic, because most terminals and
terminal emulators don't have a way of reporting which sequences they
are capable of composing.  So we let it to the users to determine
whether they need this kind of "ASCII-fied" display.

I asked whether adding a command that specifically targets ligatures
like "fi" would be useful -- can you answer that?

> The terminfo item for `linux' could indicate which characters are ok
> to display unchanged and which ones need to be displayed as the
> equivalent digraphs (or trigraphs).

Given the enormously large number of such sequences, I doubt that
terminfo is the right means for determining which sequences are
supported.  We have a solution for the Linux console, and for the rest
we allow the user to customize the value of auto-composition-mode to
disable it if the terminal misbehaves with these sequences.