bug#61413: [PATCH] Make warnings show a "warning" emoji instead of a stop-sign

[Eli Zaretskii]

> Cc: Robert Pluim <rpluim@gmail.com>, Konstantin Kharlamov 
> <Hi-Angel@yandex.ru>,
>  rms@gnu.org, 61413@debbugs.gnu.org, Stefan Kangas <stefankangas@gmail.com>
> From: Kévin Le Gouguec <kevin.legouguec@gmail.com>
> Date: Sat, 15 Feb 2025 23:50:08 +0100
> 
> In light of all this, how do we feel about the attached patch?  (FTR,
> "×" displays fine in a Linux TTY here;

Beware: the characters supported by a Linux console can be changed
programmatically.  We should use char-displayable-p to find out
whether a given character is or isn't supported.

> I do not have a Windows console handy

With the current way we write characters to the Windows terminal, "×"
shows as "\u00D7" (because it is not part of any windows-125x
encoding), so no.  (We should really work on improving our Windows
console output code, because on most modern Windows installation the
font used by the Windows terminal does support that character, and
even supports color Emoji.)

So my suggestion is to have several potential characters, all the way
down to ASCII, and test their usability using char-displayable-p, not
using system-type or similar indirect evidence.