Buttons are centered in the box. Since 2.12.
Buttons are placed at the edges of the box.
Buttons are grouped towards the end of the box, (on the right for a HBox, or the bottom for a VBox).
Buttons expand to fill the box. This entails giving buttons a "linked" appearance, making button sizes homogeneous, and setting spacing to 0 (same as calling gtk_box_set_homogeneous() and gtk_box_set_spacing() manually). Since 3.12.
Buttons are evenly spread across the box.
Buttons are grouped towards the start of the box, (on the left for a HBox, or the top for a VBox).
Used to dictate the style that a #GtkButtonBox uses to layout the buttons it contains.