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From: mojemj@unidhp.uni-c.dk (Mogens Jensen)
Newsgroups: comp.windows.x.motif,comp.lang.c++,comp.std.c++
Subject: Re: accessing private members in motif callback
Followup-To: comp.windows.x.motif,comp.lang.c++,comp.std.c++
Date: 9 Dec 1994 01:48:49 GMT
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Jeffrey Morgan (jeff@cee.hw.ac.uk) wrote:

: Dear All,

: Does anyone know how to use a private member function (C++) as a callback
: for a Motif (C) Widget?

:     static
:     void
:     articles_scrolled_list_callback(Widget scrolled_list,
:                                     XtPointer client_data,
:                                     XmListCallbackStruct *cbs)


: The (XtPointer) this in the callback allows me to access the object of which
: the scrolled list is part. However, I cannot get access to the private
: data/members in that object (if you know how - let me know)

: What I would prefer to do would be to use a private memeber function as the
: callback function e.g.

:    void
:    ArticleViewer::articles_scrolled_list_callback(Widget scrolled_list,
:                                                   XtPointer client_data,
:                                                   XmListCallbackStruct *cbs)

: to give me access to the private members. Any ideas?


What about merging the two:

class ArticleViewer : ... {
   static void articles_scrolled_list_callback( Widget, XtPointer, 
                                                XmListCallbackStruct* );
public:
   ...
   };

void
ArticleViewer::articles_scrolled_list_callback( Widget list, XtPointer data,
                                                XmListCallbackStruct *myThis )
{
   ArticleViewer &that = *(ArticleViewer*)myThis;
   ...
   float that.foo = that.fooBar();
   ...
}

I think that will do it ... ?


: Thanks.

I hope it works...


Greetings from Jens Jakob Jensen, Denmark  (using my fathers account)