title: GUI Components in Gio and not in Gtk?
body: <p>Why some GUI components are in <code>Gio</code> not in <code>Gtk</code>? E.g:
  <code>GMenu</code>, <code>GMenuItem</code>.
  I always thought that <code>GTK</code> is the place of the GUI components and <code>Gio</code> for in/out libraries.</p>