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

[Tomas Hlavaty]

On Fri 04 Feb 2022 at 23:20, Richard Stallman <rms@gnu.org> wrote:
> How can I tell which font my console uses?

on debian based systems:

dpkg-reconfigure console-setup
ls /usr/share/consolefonts/
setfont /usr/share/consolefonts/Lat2-Terminus24x12.psf.gz

sed -i 's/FONTFACE="Fixed"/FONTFACE="Terminus"/' /etc/default/console-setup
sed -i 's/FONTSIZE="8x16"/FONTSIZE="28x14"/' /etc/default/console-setup
setupcon

on nixos:

i18n.consoleFont = "Lat2-Terminus16";

setfont Lat2-Terminus24x12

> The Lisp function `char-displayable-p' seems to report correctly which
> characters my console can display.  Is it correct for yours too?

Here the cases which I see as boxes:

(char-displayable-p ?ã¯)
=> (invalid-read-syntax "?")
(char-displayable-p ?ã)
=> unicode
(char-displayable-p ?¯)
=> unicode

(char-displayable-p ?ă)
=> unicode

(char-displayable-p ?ã˘)
=> (invalid-read-syntax "?")
(char-displayable-p ?ã)
=> unicode
(char-displayable-p ?˘)
=> unicode

char-displayable-p returns non-nil even though I see boxes.