gentoo-overlay/xfce-base/xfce4-settings/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="libinput">Enable libinput Xorg driver (<pkg>x11-drivers/xf86-input-libinput</pkg>) support</flag>
    <flag name="libcanberra">Enable sound event support using <pkg>media-libs/libcanberra</pkg></flag>
    <flag name="xklavier">Enable keyboard layout selection support using <pkg>x11-libs/libxklavier</pkg></flag>
  </use>
</pkgmetadata>