GtkDialog — Create popup windows
GtkInvisible — A widget which is not displayed
GtkMessageDialog — A convenient message window
GtkWindow — Toplevel which can contain other widgets
GtkWindowGroup — Limit the effect of grabs
GtkAboutDialog — Display information about an application
GtkAssistant — A widget used to guide users through multi-step operations
GtkOffscreenWindow — A toplevel container widget used to manage offscreen rendering of child widgets.