Unable to get all child widgets

["Dugas, Alan" <alan dugas analog com>]

I am trying to retrieve the pointer of each widget contained within a window.
The wigets are packed as follows: the window contains a gtkvbox, the gtkvbox
contains a gtkhbox, gtktable, & gtkcombo, the gtkhbox contains 2 gtklabels and 2
gtkcombos.  So far I get all but those which are contained within an hbox using
the code snippet below.  It is failing the GTK_IS_COMBO test in the for loop
which sets "histogram_bins_combo".  I know this because I get the following
error when I later try to use "histogram_bins_combo" as I discovered while using
ddd/gdb:

	Gtk-WARNING **: invalid cast from (NULL) pointer to 'GtkCombo'
	segmentation fault

Can anyone see where I've gone wrong?  Is it possible to retrieve widgets
contained within a container that are themselves within a container (i.e.
retrieve a gtkcombo contained within a gtkhbox, which in turn is contained
within a gtkvbox, which in turn is contained within a gtkwindow)?  If so, is
there a limit to the depth of the hierarchy?  Any and all help would be
appreciated.


GtkWidget	*vbox = (GtkWidget *) NULL,
		*hbox = (GtkWidget *) NULL,
		*table = (GtkWidget *) NULL,
		*drawing_area = (GtkWidget *) NULL,
		*test_list_combo = (GtkWidget *) NULL,
		*histogram_bins_combo = (GtkWidget *) NULL,
		*vruler = (GtkWidget *) NULL,
		*hruler = (GtkWidget *) NULL;

GList		*widget_list;



/* Setting widget address' to local variable names */
for ( widget_list = gtk_container_children(GTK_CONTAINER(histogram_window)) ;
widget_list != NULL ; widget_list = widget_list->next )
{
	if ( GTK_IS_VBOX(GTK_OBJECT(widget_list->data)) )
		vbox = GTK_WIDGET(widget_list->data);
}
g_free(widget_list);
for ( widget_list = gtk_container_children(GTK_CONTAINER(vbox)) ; widget_list !=
NULL ; widget_list = widget_list->next )
{
	if ( GTK_IS_HBOX(GTK_OBJECT(widget_list->data)) )
		hbox = GTK_WIDGET(widget_list->data);
	if ( GTK_IS_TABLE(GTK_OBJECT(widget_list->data)) )
		table = GTK_WIDGET(widget_list->data);
	if ( GTK_IS_COMBO(GTK_OBJECT(widget_list->data)) )
		test_list_combo = GTK_WIDGET(widget_list->data);
}
g_free(widget_list);
for ( widget_list = gtk_container_children(GTK_CONTAINER(hbox)) ; widget_list !=
NULL ; widget_list = widget_list->next )
{
	if ( GTK_IS_COMBO(GTK_OBJECT(widget_list->data)) )
		histogram_bins_combo = GTK_WIDGET(widget_list->data);
}
g_free(widget_list);
for ( widget_list = gtk_container_children(GTK_CONTAINER(table)) ; widget_list
!= NULL ; widget_list = widget_list->next )
{
	if ( GTK_IS_DRAWING_AREA(GTK_OBJECT(widget_list->data)) )
		drawing_area = GTK_WIDGET(widget_list->data);
	if ( GTK_IS_HRULER(GTK_OBJECT(widget_list->data)) )
		hruler = GTK_WIDGET(widget_list->data);
	if ( GTK_IS_VRULER(GTK_OBJECT(widget_list->data)) )
		vruler = GTK_WIDGET(widget_list->data);
}
g_free(widget_list);