(defclass g-boxed-opaque ()
       ((pointer :initarg :pointer
                 :initform nil
                 :accessor g-boxed-opaque-pointer)))
   A class that is the base class for wrappers of opaque structures. Contains a pointer to the wrapped opaque structure.
Accessor function g-boxed-opaque-pointer is used to access the pointer. Pointer should not be modified directly, only read.