static void columns_base_add(GtkContainer *container, GtkWidget *widget);
static void columns_remove(GtkContainer *container, GtkWidget *widget);
static void columns_forall(GtkContainer *container, gboolean include_internals,
GtkCallback callback, gpointer callback_data);
static void columns_base_add(GtkContainer *container, GtkWidget *widget);
static void columns_remove(GtkContainer *container, GtkWidget *widget);
static void columns_forall(GtkContainer *container, gboolean include_internals,
GtkCallback callback, gpointer callback_data);