TYPEMAP
TObject*    O_TObject
TView*      O_TView
TButton*    O_TButton

INPUT
O_TObject
  $var= tvision_info_from_magic($arg, OR_DIE)->tobj;

O_TView
  $var= dynamic_cast<TView*>(tvision_info_from_magic($arg, OR_DIE)->tobj);
  if (!$var) croak("Not an instance of TView");

O_TButton
  $var= dynamic_cast<TButton*>(tvision_info_from_magic($arg, OR_DIE)->tobj);
  if (!$var) croak("Not an instance of TButton");