There is an explicit check to see if the return value is Py_None on a virtual method marked return-type "none". This is fine and expected, except when the virtual method has parameters with outbound values.

The following in gtk-base.defs:

(define-virtual toggle_size_request
  (of-object "GtkMenuItem")
  (return-type "none")
  (parameters
    '("gint*" "requisition" (direction "out"))
  )
)


produces a _wrap_GtkMenuItem__proxy_do_toggle_size_request function in gtk.c with the following sequence of code:

py_retval = PyObject_CallObject(py_method, NULL);
...
if (py_retval != Py_None) {
...
}
py_retval = Py_BuildValue("(N)", py_retval);

The problem here is that the Python method implementing do_toggle_size_request must return the integer value to be stored in the requisition outbound parameter. However, the explicit check to see if py_retval is Py_None gets in the way in this case.

This causes problems for many of the functions in atk too.