Fontconfig problem with one of the fonts

[Ken Moffat]

On Tue, Jan 12, 2021 at 05:35:47PM +0100, franek.wiertara at onet.eu wrote:
> Hello,
> This is my first post in this group.
> I have installed TexLive in Dec last year; that is the ver. "tlmgr revision 57119 (2020-12-13 00:40:00 +0100)". I also run Ubuntu 20.04.
> According to "3.4.4 System font configuration for XeTeX and LuaTeX" on "The TeX Live Guide—2020", we are supposed to add a font file "texlive/2020/texmf-var/fonts/conf/texlive-fontconfig.conf" to "/etc/fonts/conf.d/" and rename it as "09-texlive.conf". I simply the file to its source.
> It turns out after doing so, I have started having issues with `snap` and `fontconfig`. I have currently snap 2.48.2 and snapd 2.48.2 installed. The errors are following:
>  
> error: cannot perform the following tasks:
> - Run configure hook of "zoom-client" snap if present (run hook "configure":
> -----
> Fontconfig warning: "/etc/fonts/fonts.conf", line 5: unknown element "its:rules"
> Fontconfig warning: "/etc/fonts/fonts.conf", line 6: unknown element "its:translateRule"
> Fontconfig error: "/etc/fonts/fonts.conf", line 6: invalid attribute 'translate'
> Fontconfig error: "/etc/fonts/fonts.conf", line 6: invalid attribute 'selector'
> Fontconfig error: "/etc/fonts/fonts.conf", line 7: invalid attribute 'xmlns:its'
> Fontconfig error: "/etc/fonts/fonts.conf", line 7: invalid attribute 'version'
> Fontconfig warning: "/etc/fonts/fonts.conf", line 9: unknown element "description"
> -----)
>  
> This is only one application but errors are caused by any application which need to be installed or refreshed by snap. If I remove "09-texlive.conf" and re-cache all fonts:
> rm -f ~/.cache/fontconfig/*
> sudo rm -f /var/cache/fontconfig/*
> sudo fc-cache -rv
>  
> snap gets working again.
>  
> Is it possible that the font I have mentioned is not compatible with the new version of fontconfig? Ubuntu 20.04 has updated the library to the following:
>  

I don't think you've mentioned the font by name ?

I'll also note that I don't usually install the binary, and I do not
usually make the fonts available to the system for two reasons:

(i.) I do a full install.  Selecting a font in e.g. libreoffice or
gucharmap when hundreds are present from TL, often with odd names,
is impractical.

(ii.) When I last checked, some of the TL versions were older than
what I have installed on my system - in that case, it is unclear
which version would be used.

However, for specific fonts I do occasionally write a conf file so I
can use them outside xetex, but limiting what I want (and I don't
normally see any reason to use Type1 fonts, but I guess YMMV).  for
example: (in 09-texlive.conf in the past, but updated for 2020
usage):

<?xml version='1.0'?>
<!DOCTYPE fontconfig SYSTEM 'fonts.dtd'>
<fontconfig>
  <dir>/opt/texlive/2020/texmf-dist/fonts/opentype/arkandis/berenisadf</dir>
  <dir>/opt/texlive/2020/texmf-dist/fonts/truetype/paratype</dir>
</fontconfig>

But for the specific fontconfig errors, google found e.g.
https://bbs.archlinux.org/viewtopic.php?id=235643 from 2018
(see post #6 et. seq and particularly #15 for an addition to
fonts.dtd which might fix this.)

I guess the problem is in snap.  Googling for snap Fontconfig
warning: unknown element "its:rules" produces a lot of results.
Maybe whoever created one or other of the snap packages you are
using was using an old version of fontconfig.

One of the reports was
https://emacs.stackexchange.com/questions/52700/fontconfig-error-in-snap-version-of-emacs

which was also on ubuntu 20.04 and apparently caused by snap using
old versions - see
https://github.com/alexmurray/emacs-snap/issues/10

That says (near the end) that the emacs snap was changed to use
core20 (ubuntu) as its base, and that fixed it.  so I guess you need
to identify which snaps are involved (starting with zoom client) and
update them in case already fixed, or else raise an issue on the
specific snap.

ĸen
-- 
Lu-Tze had long considered that everything happens for a reason,
except possibly football.      -- The Thief Of Time