How to Configure Fonts in Linux

Fonts configuration on linux is handled using fontconfig (https://en.wikipedia.org/wiki/Fontconfig). It can be used to configure fallback font and setting default fonts (Sans, Sans Serif, Monospace).

Location of fonts

Fonts are stored in following locations,

/usr/share/fonts
/usr/local/share/fonts
$XDG_DATA_HOME/fonts
- ~/.local/share/fonts

Configuration of `fontconfig`

fontconfig configuration file is in XML format.

/etc/fonts/fonts.conf
/etc/fonts/conf.d
- directory which can contain multiple configurations, higher number configuration is loaded first
$XDG_CONFIG_HOME/fontconfig/conf.d
- ~/.config/fontconfig/conf.d
$XDG_CONFIG_HOME/fontconfig/fonts.conf
- ~/.config/fontconfig/fonts.conf
~/.fonts.conf.d
~/.fonts.conf

`fontconfig` utilities

fc-list - Lists all fonts fontconfig knows about or all fonts matching a pattern.
fc-match - Matches font-pattern (empty pattern by default) using the normal fontconfig matching rules to find the most appropriate font available.
fc-cache - Creates a cache of all FreeType readable fonts in a specified directory or create a cache of all FreeType readable fonts from all directories specified in the configuration files.
- fc-cache -fv - after copy new font use this command to force re-generation of cache files.
fc-cat - Reads the font information from cache files or related to font directories and emits it in ASCII form.
fc-query - Querys font files and reports resulting pattern(s).
fc-scan - Scans font files and directories and reports resulting pattern(s).
fc-pattern - Lists best font(s) matching the supplied pattern(s).
fc-validate - Validate font file(s) and reports the results.

Sample `fontconfig` configuration

enable antialiasing for all fonts

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
    <!-- Enable antialiasing for all fonts -->
    <match target="font">
        <edit mode="assign" name="antialias"><bool>true</bool></edit>
    </match>
</fontconfig>

setting default Sans, SansSerif, Monospace fonts

<?xml version='1.0'?>
<!DOCTYPE fontconfig SYSTEM 'fonts.dtd'>
<fontconfig>
  <!-- Set preferred serif, sans serif, and monospace fonts. -->
  <alias>
    <family>sans-serif</family>
    <prefer><family>CMU Sans Serif</family></prefer>
  </alias>
  <alias>
    <family>sans</family>
    <prefer><family>CMU Typewriter Text</family></prefer>
  </alias>
  <alias>
    <family>monospace</family>
    <prefer><family>Iosevka Term</family></prefer>
  </alias>
</fontconfig>

for setting up emoji fonts, when some applications are unable to display emoji, in this case I used Noto Color Emoji

<?xml version='1.0'?>
<!DOCTYPE fontconfig SYSTEM 'fonts.dtd'>
<fontconfig>
  <!-- setting up emoji fonts as weak binding -->
  <match>
    <test name="family"><string>sans-serif</string></test>
    <edit name="family" mode="prepend" binding="weak">
      <string>Noto Color Emoji</string>
    </edit>
  </match>
  <match>
    <test name="family"><string>serif</string></test>
    <edit name="family" mode="prepend" binding="weak">
      <string>Noto Color Emoji</string>
    </edit>
  </match>
  <match>
    <test name="family"><string>monospace</string></test>
    <edit name="family" mode="prepend" binding="weak">
      <string>Noto Color Emoji</string>
    </edit>
  </match>
  <match>
    <test name="family"><string>Apple Color Emoji</string></test>
    <edit name="family" mode="prepend" binding="weak">
      <string>Noto Color Emoji</string>
    </edit>
  </match>
</fontconfig>