bug#51155: 29.0.50; Incorrect weight used in Cantarell VF

[Utkarsh Singh]

Hi,

On 2021-09-21, Arch Linux updated their Cantarell font package, which
removed classic font with variable fonts.  According to Jan Alexander
Steffens (package maintainer):

> Yeah, we only packaged VF because upstream requested to either package
> the classic fonts *or* the variable font. The VF is more powerful as
> it not just contains all the classic weights but can also interpolate
> between them.

But with these changes Emacs in now unable to distinguish between light
and regular weights.  To reproduce the bug you would have to:

1. Install latest version of font from upstream:
<https://gitlab.gnome.org/GNOME/cantarell-fonts>

2. Evaluate in "emacs -Q" session:
(progn
  (set-face-attribute 'variable-pitch nil :family "Cantarell" :weight 'regular)
  (face-font 'variable-pitch))

Also see bug report on Arch Linux bug tracker:
<https://bugs.archlinux.org/task/72212>

-- 
Utkarsh Singh
https://utkarshsingh.xyz/