-// Deals with function returning a C++ string.
-%typemap(python, in) (gdcm::Method *,void * =NULL,gdcm::Method * =NULL) {
+// Multi-argument typemap designed for wrapping the progress related methods
+// in order to control from an external application the computation of
+// a DicomDir object (see DicomDir::SetStartMethod*,
+// DicomDir::SetProgressMethod* and DicomDir::SetEndMethod*).
+// Motivation: since DicomDir parsing can be quite long, a GUI application
+// needs to display the avancement and potentially offer a
+// cancel method to the user (when this one feels things are
+// longer than expected).
+// Example of usage: refer to demo/DicomDirProgressMethod.py
+// Note: Uses gdcmPythonVoidFunc and gdcmPythonVoidFuncArgDelete defined
+// in the Swig verbatim section of this gdcm.i i.e. in the above section
+// enclosed within the %{ ... %} scope operator ).
+%typemap(python, in) ( gdcm::DicomDir::Method *,
+ void * = NULL,
+ gdcm::DicomDir::Method * = NULL )
+{