gtk:single-selection-can-unselect (object)

object -- a gtk:single-selection object
setting -- true to allow unselecting

The accessor for the can-unselect slot gets or sets whether unselecting the selected item is allowed. If true, unselecting the current item is supported. Note that setting autoselect will cause the unselecting to not work, so it practically makes no sense to set both at the same time the same time.