Why isn't my custom widget getting mapped?

[Braden McDaniel <braden endoframe com>]

I have the following GtkBuilder XML:

        <object class="GtkVBox" id="vbox1">
          <property name="visible">True</property>
          <child>
            <object class="GtkMenuBar" constructor="uimanager1" id="menubar1">
              <property name="visible">True</property>
            </object>
            <packing>
              <property name="expand">False</property>
            </packing>
          </child>
          <child>
            <object class="GtkHBox" id="hbox1">
              <property name="visible">True</property>
              <child>
                <object class="GtkEntry" id="locationentry">
                  <property name="visible">True</property>
                  <signal handler="openvrml_player_on_locationentry_activated" name="activate"/>
                  <signal handler="locationentry_map_event" name="map-event"/>
                </object>
              </child>
            </object>
            <packing>
              <property name="expand">False</property>
              <property name="position">1</property>
            </packing>
          </child>
          <child>
            <object class="VrmlControlHost" id="controlhost">
              <property name="visible">True</property>
              <property name="can-focus">True</property>
              <property name="has-focus">True</property>
              <signal handler="controlhost_map_event" name="map-event"/>
            </object>
            <packing>
              <property name="expand">True</property>
              <property name="position">2</property>
            </packing>
          </child>
          <child>
            <object class="GtkStatusbar" id="statusbar1">
              <property name="visible">True</property>
            </object>
            <packing>
              <property name="expand">False</property>
              <property name="position">3</property>
            </packing>
          </child>
        </object>
        
VrmlControlHost is a custom widget that is derived from GtkBin. For some
reason, it doesn't seem to get mapped. It does get created and realized.
But I don't see it. And while the locationentry_map_event function
attached to the locationentry widget does get called, the
controlhost_map_event function similarly attached to controlhost never
gets called.

What might I have neglected to do (or unwittingly done) that would
result in this?

-- 
Braden McDaniel                           e-mail: <braden endoframe com>
<http://endoframe.com>                    Jabber: <braden jabber org>