implementation can typically pass <code class="literal">NULL</code> to
80
<code class="function">G_IMPLEMENT_INTERFACE()</code> as the interface
79
implementation can typically pass <a href="http://library.gnome.org/devel/glib/unstable/glib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a> to
80
<a href="http://library.gnome.org/devel/gobject/unstable/gobject-Type-Information.html#G-IMPLEMENT-INTERFACE:CAPS"><code class="function">G_IMPLEMENT_INTERFACE()</code></a> as the interface