protected void AddButton(Gdk.Pixbuf pixbuf, string label_text, Gtk.ResponseType response, bool is_default)
{
Gtk.Button button = new Gtk.Button ();
Gtk.Image image = new Gtk.Image (pixbuf);
// NOTE: This property is new to GTK+ 2.10, but we don't
// really need the line because we're just setting
// it to the default value anyway.
//button.ImagePosition = Gtk.PositionType.Left;
button.Image = image;
button.Label = label_text;
button.UseUnderline = true;
button.CanDefault = true;
AddButton (button, response, is_default);
}