gentoo-overlay/xfce-extra/tumbler/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
  <maintainer type="project">
    <email>xfce@gentoo.org</email>
    <name>XFCE Team</name>
  </maintainer>
  <use>
    <flag name="epub">Enable support for .epub thumbnailer using <pkg>app-text/libgepub</pkg></flag>
    <flag name="odf">Enable support for .odf thumbnailers by using <pkg>gnome-extra/libgsf</pkg></flag>
  </use>
</pkgmetadata>