bug#59347: 29.0.50; `:family` face setting ignored

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 08 Dec 2022 01:07:25 +0000
> From: Gregory Heytings <gregory@heytings.org>
> cc: Eli Zaretskii <eliz@gnu.org>, 59347@debbugs.gnu.org
> 
> Do you mean that if a user chooses a font for the default face that has a 
> single variant (say 'regular'), then the 'bold' face (which does not 
> specify any family) should be realized with another font which has a bold 
> variant?  And that the 'italic' face should likewise be realized with 
> another font which has an italic variant?

I don't think these situations are possible, at least not all of them,
because Emacs will not use a font for the default face if that font
doesn't have at least the bold or italic variant.

> FWIW, I don't think either of these options are reasonable.

You keep saying that, but you don't explain why this must be the
truth.  A user or a Lisp program can reasonably want an ultra-bold
font and consider that more important than keeping the family.  You
never explained why you thought this to be an unreasonable request.

> IMO in the first case the user should just use a font which has more
> variants for the default face (there are plenty of excellent fonts),
> and in the second case it is fine to approximate the weight with the
> weights that are available in the default font.

The questions is what should Emacs do in this case, not what the user
should do.

When I want Emacs to render text in some script, I would naturally
prefer _any_ font that is capable of supporting that script, even if
it doesn't belong to the family from which the default font is taken.
Why should width or slant or weight be treated differently?