fonts.conf.xml

<?xml version='1.0'?>
<!DOCTYPE fontconfig SYSTEM 'fonts.dtd'>
<fontconfig>

 <match target="font">
    <test name="family" compare="eq">
        <string>Roboto</string>
    </test>
    <edit name="family" mode="assign_replace">
      <string>Roboto</string>
    </edit>
    <edit name="family" mode="append_last">
      <string>serif</string>
    </edit>
  </match>

  <!-- TODO: replace Roboto with my UI fonts -->
  <match>
    <test qual="any" name="family">
        <string>serif</string>
    </test>
    <edit name="family" mode="prepend_first">
      <string>Roboto</string>
    </edit>
    <edit name="family" mode="prepend_first">
      <string>Noto Color Emoji</string>
    </edit>
  </match>

  <match target="font">
    <test name="family" compare="eq">
        <string>Roboto</string>
    </test>
    <edit name="family" mode="assign_replace">
      <string>Roboto</string>
    </edit>
    <edit name="family" mode="append_last">
      <string>sans-serif</string>
    </edit>
  </match>

  <match target="pattern">
    <test qual="any" name="family">
        <string>sans-serif</string>
    </test>
    <edit name="family" mode="prepend_first">
      <string>Roboto</string>
    </edit>
    <edit name="family" mode="prepend_first">
      <string>Noto Color Emoji</string>
    </edit>
  </match>

  <match target="font">
    <test name="family" compare="eq">
        <string>Iosevka Custom Extended</string>
    </test>
    <edit name="family" mode="assign_replace">
      <string>Iosevka Custom Extended</string>
    </edit>
    <edit name="family" mode="append_last">
      <string>monospace</string>
    </edit>
  </match>

  <match target="pattern">
    <test qual="any" name="family">
        <string>monospace</string>
    </test>
    <edit name="family" mode="prepend_first">
      <string>Iosevka Custom Extended</string>
    </edit>
    <edit name="family" mode="prepend_first">
      <string>Noto Color Emoji</string>
    </edit>
  </match>

  <alias binding="strong">
    <family>emoji</family>
    <default><family>Noto Color Emoji</family></default>
  </alias>

  <alias binding="strong">
    <family>Apple Color Emoji</family>
    <prefer><family>Noto Color Emoji</family></prefer>
    <default><family>sans-serif</family></default>
  </alias>
  <alias binding="strong">
    <family>Segoe UI Emoji</family>
    <prefer><family>Noto Color Emoji</family></prefer>
    <default><family>sans-serif</family></default>
  </alias>
  <alias binding="strong">
    <family>Twitter Color Emoji</family>
    <prefer><family>Noto Color Emoji</family></prefer>
    <default><family>sans-serif</family></default>
</alias>
</fontconfig>