bug#21640: 25.0.50; Fontset-font is never scaled

[Artur Malabarba <arturmalabarba@gmail.com>]

2015-10-07 20:20 GMT+01:00 Eli Zaretskii <eliz@gnu.org>:
> Could it be that the version of Symbola is different between the two
> systems, and one of them cannot be scaled like you want?

It's possible, I don't know how to look up font versions. The version
of the package that I installed for this font is 8.0.0 on Arch, but I
can't even find out where the font comes from on Ubuntu (probably
pre-installed).

Anyway, the matter is more complicated then I initially thought. Even
on Ubuntu it doesn't work on every Symbola character.
For instance, I can get it to work with the "MATHEMATICAL
DOUBLE-STRUCK DIGIT ____" family. If I inspect the char I get this
description:
    xft:-unknown-Symbola-normal-normal-semicondensed-*-50-*-*-*-*-0-iso10646-1
(#x14CD)

But it doesn't seem to work with anything from the "SMILING FACE WITH
___" family.
    xft:-unknown-Symbola-normal-normal-semicondensed-*-16-*-*-*-*-0-iso10646-1
(#x18FA)

Note how one is correctly using the size 50 (which I had previously
set via `(font-spec :size 50 :name "Symbola")'), and the other is
using size 16.
Does anyone know where is the code responsible for figuring out this
number when the char is inserted? (so I can investigate)

Anyway, I'm pretty sure most characters worked on a previous Arch
installation I had. I'll test it on a previous Emacs version to figure
out if the regression is in Emacs or in my system.