google-droid-fonts/google-droid-fonts-sans-fontconfig.conf

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE fontconfig SYSTEM "../fonts.dtd">
<fontconfig>
  <alias>
    <family>sans-serif</family>
    <prefer>
      <family>Droid Sans</family>
    </prefer>
  </alias>
  <alias>
    <family>Droid Sans</family>
    <default>
      <family>sans-serif</family>
    </default>
  </alias>
  <!-- CJK users should check this actually works for them -->
  <match target="scan">
    <test name="lang">
      <string>ja-jp</string>
    </test>
    <test name="family">
      <string>Droid Sans Japanese</string>
    </test>
    <edit name="family">
      <string>Droid Sans</string>
    </edit>
  </match>
  <match target="scan">
    <test name="lang" compare="not_eq">
      <string>ja-jp</string>
    </test>
    <test name="family">
      <string>Droid Sans Fallback</string>
    </test>
    <edit name="family">
      <string>Droid Sans</string>
    </edit>
  </match>
</fontconfig>