The decoration layout for buttons.
If this property is not set, the
GtkSettings:gtk-decoration-layout setting is used.
The format of the string is button names, separated by commas. A colon separates the buttons that should appear at the start from those at the end. Recognized button names are minimize, maximize, close and icon (the window icon).
For example, “icon:minimize,maximize,close” specifies an icon at the start, and minimize, maximize and close buttons at the end.