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

[Gregory Heytings]

> > 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.

Hmmm... here at least it does.  With Fixedsys500c.ttf in 
http://www.ler.is.edu.ro/~ema/proiecte/soft/2005/apm/+predesign/fonts/fixedsys500c.zip 
(which has no variants) and (set-face-attribute 'default nil :font 
"FixedSysTTF"), the bold, italic and bold-italic faces are identical.

> > 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.

It's only my opinion, indeed.  I don't think it's a completely 
unreasonable request, but it's not what Emacs has been doing so far, and I 
do think that it's not what Emacs should do by default.  It is better to 
preserve a visual coherence / uniformity.  Also note that allowing that 
would mean that Emacs would need to consider all fonts when realizing a 
face, instead of what it does now, namely to relax the family/... 
attributes only when necessary, that is, to consider more fonts only when 
necessary.

And also note that, should a user really want a specific ultra-bold font 
for a certain face, that is already possible with the existing 
infrastructure, by making that choice explicit, e.g. (set-face-attribute 
'bold nil :font "Desired Font" :weight 'ultra-bold).  And it is also 
possible, with the existing infrastructure, to list the available fonts 
with given attribute values, e.g. with (list-fonts (font-spec :weight 
'ultra-bold)), and to select the best one in that list with an appropriate 
fourth argument to list-fonts.