Re: Question regarding tty special glyphs display defaults

[Gerd Möllmann]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Gerd Möllmann <gerd.moellmann@gmail.com>
>> Date: Wed, 09 Oct 2024 06:24:35 +0200
>> 
>> Problem is that I find the default ASCII chars being used ugly as hell,
>> at least the ones for vertical-border and the new ones for the borders
>> of child frames. The truncation...selective-display glyphs are kind of
>> okay for my personal taste.
>> 
>> I'm pondering if we could change the defaults to Unicode box drawing
>> chars falling back to the ASCII chars if the terminal output coding
>> system isn't Unicode.
>> 
>> Q1: WDYT?
>
> Using Unicode (or non-ASCII in general) on text terminals is
> problematic, because we need to establish whether a character is
> supported before using it, and text terminals differ wildly in that
> aspect.  We have char-displayable-p, but it is not 100% reliable
> (except if you are on the Linux console, for which we have special
> support), so using this by default is not reliable, either.

Ah thanks, that's what I was looking for and couldn't find. 

> Why cannot this be left to user customizations, leaving the ("ugly as
> hell") ASCII characters as the default, since those are reliably
> displayed?

I'm just wondering if one could do better. I think the Unicode box
drawing characters like U+2502 '│' instead of '|' for example are quite
commonly used in terminal programs. And they produce a much nicer
display. On my system I sometimes have to take a second look to see
if I have a GUI version in front of me or not (it's the modeline that
is slightly different).

Hm, don't know, if you don't want that, it's of course okay. I have my
setup already as I like it.

>> Q2: if the answer is positive, how the heck does one write a function
>> like is_unicode (struct coding_system *)?
>
> I don't understand why you need this.  Please tell more (or maybe
> char-displayable-p is the answer you were looking for, without
> actually asking it ;-).

Indeed, char-displayable-p is what I was looking for :-). Thanks.