swig : typemaps for value return by ref PViewData

gmshpy/gmshPost.i

 %feature("autodoc", "1");
 %module gmshPost
+%include typemaps.i
 %include std_string.i
 
 %{
   #include "GmshConfig.h"
-
   #include "fullMatrix.h"
   #include "PView.h"
-  #include "PViewData.h"
   #include "PViewFactory.h"
+  #include "PViewData.h"
 %}
 
 %include "GmshConfig.h"
-
 %include "PView.h"
-%include "PViewData.h"
+
 %include "PViewFactory.h"
+
+%apply double &OUTPUT { double &val}
+%include "PViewData.h"
+