Used to change the appearance of an outline typically provided by a GtkFrame or a GtkScrolledWindow. GtkArrows also use the shadow type.
|1||Gtk::SHADOW_IN||The outline is bevelled inwards.|
|2||Gtk::SHADOW_OUT||The outline is bevelled outwards like a button.|
|3||Gtk::SHADOW_ETCHED_IN||The outline itself is an inward bevel, but the frame does.|