[Fontconfig] Difficulty finding a font file through the libraries

[Lawrence D'Oliveiro]

On Thu, 28 Oct 2021 23:55:38 -0500, Michael Brennen wrote:

> apache has a nologin shell, so sudo -i does not work.

Also add -s to run the shell of your choice. I think it’s important to
try to recreate as faithfully as possible the environment in which
Ghostscript is running.

> The client’s font directory path is in /etc/fonts/local.conf as a
> <dir>…</dir> parameter within <fontconfig>. That is how gs finds the
> mass of fonts they have.

Besides font directories, it is possible to include user-specific
config files. On my Debian system, /etc/fonts/conf.d/50-user.conf has
these lines:

    <include ignore_missing="yes" prefix="xdg">fontconfig/conf.d</include>
    <include ignore_missing="yes" prefix="xdg">fontconfig/fonts.conf</include>
    <!-- the following elements will be removed in the future -->
    <include ignore_missing="yes" deprecated="yes">~/.fonts.conf.d</include>
    <include ignore_missing="yes" deprecated="yes">~/.fonts.conf</include>

So there’s a whole lot more options where config settings can come from.
And this can be overridden via environment variables, too (see the page
linked below).

> How does fc relate the file name of the font to the font’s internal
> name?

It builds a cache of information from each font file found, including
its file name and various 'name' entries found in the .ttf/.otf files.

> The linked config files in /etc/fonts/conf.d don’t make much sense to
> me ...

It’s all XML, documented here:
<https://www.freedesktop.org/software/fontconfig/fontconfig-user.html>.