[Glade-users] libglade - Associating a mode with an empty combo_box

[kbulgrien at worldnet.att.net (Kevin R. Bulgrien)]

Regarding the prior thread "(newbie) combobx and model"... found here:

  http://lists.ximian.com/pipermail/glade-users/2007-May/003493.html

I have exactly the same difficulty the original poster spoke of, but do
not have a clue where to go after extensive Googling and reading of
articles.

    $ glade-2 --version
    Gnome glade-2 2.12.1
    $ rpm -q lib64glade2.0_0
    lib64glade2.0_0-2.6.0-1mdv2007.0

Problem:  An empty combo box is created in a window using glade-2.  No
items are placed in the combo box because it will be filled at run-time.
In the glade file a couple combo boxes look like this:

      ...
          <child>
            <widget class="GtkComboBox" id="config_combobox_faceset">
              <property name="width_request">170</property>
              <property name="visible">True</property>
              <property name="items" translatable="yes"></property>
              <property name="add_tearoffs">False</property>
              <property name="focus_on_click">True</property>
            </widget>
            <packing>
              <property name="padding">0</property>
              <property name="expand">False</property>
              <property name="fill">True</property>
            </packing>
          </child>
      ...
          <child>
            <widget class="GtkComboBox" id="config_combobox_theme">
              <property name="width_request">170</property>
              <property name="visible">True</property>
              <property name="add_tearoffs">False</property>
              <property name="focus_on_click">True</property>
            </widget>
            <packing>
              <property name="padding">0</property>
              <property name="expand">False</property>
              <property name="fill">True</property>
            </packing>
          </child>
       ...

When the window is first displayed, the behavior of the two empty combo boxes
is not identical.  Consider:

    model = gtk_combo_box_get_model(GTK_COMBO_BOX(config_combobox_faceset));
    count =  gtk_tree_model_iter_n_children(model, NULL);

model is returned non-null, and the combo_box is filled as expected, and one
might expect the same behavior from exactly the same code later on:

    model = gtk_combo_box_get_model(GTK_COMBO_BOX(config_combobox_theme));
    count =  gtk_tree_model_iter_n_children(model, NULL);

But, in this case, model is NULL:

    575         model = gtk_combo_box_get_model(GTK_COMBO_BOX(config_combobox_theme));
    (gdb) step
    583         count =  gtk_tree_model_iter_n_children(model, NULL);
    (gdb) print model
    $1 = (GtkTreeModel *) 0x0

When line 583 executes, an error is thrown:

    Gtk-CRITICAL **: gtk_tree_model_iter_n_children:
    assertion `GTK_IS_TREE_MODEL (tree_model)' failed

Naturally, any attempt to populate combo box fails with additional errors.

The code may be forced to work by assigning a dummy value to the combo box in
glade-2, and by deleting the dummy entry prior to populating the combo box
with the appropriate data, but this seems a kludge as it appears there is an
inconsistency in how libglade handles empty combo boxes.

I tried applying a fix of the nature that appeared to be portrayed in various
locations, but namely:

    http://scentric.net/tutorial/

Apparently I misunderstand the tutorial, as this does not work:

    model = gtk_combo_box_get_model(GTK_COMBO_BOX(config_combobox_theme));
    if (! model)
    {
      store = gtk_list_store_new(1, G_TYPE_STRING);
      gtk_combo_box_set_model(GTK_COMBO_BOX(config_combobox_theme),
GTK_TREE_MODEL(store));
    }
    count =  gtk_tree_model_iter_n_children(model, NULL);

Any ideas?  The tutorial omits additional steps in this mini-example:

    http://scentric.net/tutorial/sec-treeview.html#sec-treeview-connect-model

Perhaps I must add data to the store before using gtk_combo_box_set_model(),
and perhaps the model is not set up entirely since there is no reference to
a renderer, etc, and so set model ignores the requested operation?

Any help or hints appreciated.  I've been digging on this for a few days,
and am about to just do it by filling a dummy value in via the xml file so
that libglade will have already create a model associated with the combo box
even though that forces me to empty the tree view before I populate it..

Thanks,

Kevin Bulgrien