The class
radio-button-panel
inherits all of its behavior from button-panel, which itself inherits most of its behavior from choice. Thus, the radio button panel can accept items, callbacks, and so forth.
(capi:contain (make-instance
'capi:radio-button-panel
:title "Select a color:"
:items '(:red :green :blue)
:print-function 'string-capitalize))
(setq buttons (capi:contain
(make-instance
'capi:radio-button-panel
:title "Select a color:"
:items '(:red :green :blue)
:print-function 'string-capitalize
:layout-class 'capi:column-layout)))
(capi:choice-selected-item buttons)
There is a further example in the file
examples/capi/buttons/buttons.lisp
.