~/.config/fontconfig/fonts.conf

fonts.conf

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
  <alias>
    <family>sans-serif</family>
    <prefer>
      <family>Source Sans Pro</family>
    </prefer>
  </alias>
  <alias>
    <family>serif</family>
    <prefer>
      <family>Source Serif Pro</family>
    </prefer>
  </alias>
  <alias>
    <family>monospace</family>
    <prefer>
      <family>Source Code Pro</family>
    </prefer>
  </alias>
  <match target="font">
    <edit mode="assign" name="antialias">
      <bool>true</bool>
    </edit>
    <edit mode="assign" name="autohint">
      <bool>false</bool>
    </edit>
    <edit mode="assign" name="hinting">
      <bool>true</bool>
    </edit>
    <edit mode="assign" name="hintstyle">
      <const>hintslight</const>
    </edit>
    <edit mode="assign" name="lcdfilter">
      <const>lcdlight</const>
    </edit>
    <edit mode="assign" name="rgba">
      <const>rgb</const>
    </edit>
  </match>
</fontconfig>