gobject:type-interface-peek (class itype)

class -- a g:type-class instance
itype -- a g:type-t interface type ID which this class conforms to

The g:type-interface instance of itype if implemented by class, nil otherwise.

Returns the interface structure of an interface to which the passed in class conforms.

(g:type-interface-peek (g:type-class-ref "GtkBox") "GtkOrientable")
=> #.(SB-SYS:INT-SAP #X080C6858)
(g:type-from-interface *)
=> #S(GTYPE :NAME "GtkOrientable" :%ID 134887472)