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

[Kévin Le Gouguec]

Eli Zaretskii <eliz@gnu.org> writes:

>> Date: Thu, 27 Jan 2022 11:55:25 +0200
>> From: Eli Zaretskii <eliz@gnu.org>
>> Cc: psainty@orcon.net.nz, luangruo@yahoo.com, schwab@linux-m68k.org,
>>  rms@gnu.org, emacs-devel@gnu.org
>> 
>> > Reading the documentation of the various glyphless-* knobs, I wonder if
>> > it would make sense to provide another group for
>> > glyphless-char-display-control?  'no-font is not helpful on my TTY, IIUC
>> > because terminal-coding-system says "utf-8-unix"?).
>> > 
>> > Maybe 'no-display, meaning (null (char-displayable-p CHAR))?
>> 
>> Isn't that what glyphless-char-display-control already does on a TTY
>> for no-font?  We just need to set up the table for such characters.
>
> Or maybe we should install the below?

Ah, yes, that does improve the situation quite a bit here (if that
matters: Linux 5.16.1 on openSUSE Tumbleweed; 5.10.92 on Debian 11): all
the characters that we discussed here and showed up as diamonds (ffi, ⚀)
now show up as \uHHHH escape sequences.

(I just noticed that there seem to be a TTY glyph for fi on Tumbleweed,
but not on Debian 11 🤔)

>> But I don't think that displaying the hex code is the best alternative
>> for this particular use case, as displaying the ASCII equivalents is
>> much better.

Right, wholehearted agreement.  I only mentioned the hex codes because
they seemed (1) more informative than the infamous diamonds, (2) less
effort to implement than displaying the ASCII equivalent, (3) also
applicable to other characters (e.g. symbols & emojis).

With your patch, none of these points remain relevant.  Thanks!