How to hide the "sub-menu" title of a GtkComboBoxEntry ?

[Lyre <4179e1 gmail com>]

 I created a GtkComboBoxEntry with GtkTreeStore. The problem is, the
"sub-menu" have a title whose value is the same as it's parent. How could I
drop this title?

I notice that a GtkComboBox example in gtk-demo without this title, it's
done by by  gtk_cell_layout_set_cell_data_func () which have a parameter of
GtkCellRenderer * ãBut is there a way to get the renderer from
GtkComboBoxEntry?

Here is an example:

#if 0
gcc -Wall -O2 -o main main.c `pkg-config --libs --cflags gtk+-2.0`
exit
#endif

#include <gtk/gtk.h>

#define ARRAY_SIZE(A)    (sizeof(A) / sizeof (A[0]))

gchar *abc[] =
{
    "title 1",
    "a---",
    "b---",
    "c---",
    NULL,
};

gchar *def[] =
{
    "title 2",
    "d---",
    "e---",
    "f---",
    NULL,
};

gchar **list[] =
{
    abc,
    def,
};

GtkTreeModel *model_new (void)
{
    GtkTreeIter iter, iter2;
    gint i;

    GtkTreeStore *store = gtk_tree_store_new (1, G_TYPE_STRING);
    for (i = 0; i < ARRAY_SIZE(list); i++)
    {
        gtk_tree_store_append (store, &iter, NULL);
        gtk_tree_store_set (store, &iter, 0, list[i][0],-1);

        gchar **str = &(list[i][1]);
        for (; *str != NULL; str++)
        {
            gtk_tree_store_append (store, &iter2, &iter);
            gtk_tree_store_set (store, &iter2, 0, *str, -1);
        }
    }

    return GTK_TREE_MODEL (store);
}

static void is_capital_sensitive (GtkCellLayout   *cell_layout,
        GtkCellRenderer *cell,
        GtkTreeModel    *tree_model,
        GtkTreeIter     *iter,
        gpointer         data)
{
    gboolean sensitive;

    sensitive = !gtk_tree_model_iter_has_child (tree_model, iter);

    g_object_set (cell, "sensitive", sensitive, NULL);
}

int main (int argc, char *argv[])
{
    GtkWidget *window;
    GtkWidget *box;
    GtkWidget *combo;
    GtkCellRenderer *renderer;

    gtk_init (&argc, &argv);

    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
    g_signal_connect (G_OBJECT (window), "destroy", G_CALLBACK
(gtk_main_quit), (gpointer)window);

    box = gtk_vbox_new (FALSE, 2);
    gtk_container_add (GTK_CONTAINER (window), box);

    GtkTreeModel *model = model_new();

    combo = gtk_combo_box_entry_new ();
    gtk_combo_box_set_model (GTK_COMBO_BOX (combo), model);
    gtk_combo_box_entry_set_text_column (GTK_COMBO_BOX_ENTRY (combo), 0);
    gtk_box_pack_start_defaults (GTK_BOX (box), combo);


    GtkWidget *c = gtk_combo_box_new();
    renderer = gtk_cell_renderer_text_new ();
    gtk_cell_layout_pack_start (GTK_CELL_LAYOUT (c), renderer, TRUE);
    gtk_cell_layout_set_attributes (GTK_CELL_LAYOUT (c), renderer, "text",
0, NULL);
    gtk_combo_box_set_model (GTK_COMBO_BOX (c), model);
    gtk_box_pack_start_defaults (GTK_BOX (box), c);
    gtk_cell_layout_set_cell_data_func (GTK_CELL_LAYOUT (c),
            renderer,
            is_capital_sensitive,
            NULL, NULL);

    gtk_widget_show_all (window);

    gtk_main ();

    return 0;
}