[vtkusers] Catching member events from inside a class instance

[David Doria]

I have a vtkImageTracerWidget as a member variable of a subclass of
vtkInteractorStyle. To catch its events in a way that I still have
access to the class instance data, I have declared a callback function

  public:
    static void KeypressCallbackFunction ( vtkObject* caller,  long
unsigned int eventId,
  void* clientData, void* callData );

and when I set up the vtkCallbackCommand, SetClientData to the address
of my interactor style. This seems like a horribly convoluted way to
catching these events - is there a more OO-friendly way?

Thanks,

David