28) How can tell I if the user has selected the "Close" item on the

system menu attached to the top-level shell?  I need to do some clean up
before exiting.

[Last modified: May 93]

Answer:          This works with R4 Intrinsics

        #include <Xm/Protocols.h>

        void FinalCleanupCB(w, client_data, call_data)
        Widget   w;
        caddr_t  client_data, call_data;
        {
                /* tidy up stuff here */
                ...
                /* exit if you want to */
                exit (0);
        }

        main()
        {
                Atom wm_delete_window;

                ...
                XtRealizeWidget(toplevel);
                ...
                wm_delete_window =
                        XmInternAtom(XtDisplay(toplevel),
                                "WM_DELETE_WINDOW", False);
                XmAddWMProtocolCallback(toplevel, wm_delete_window,
                        FinalCleanupCB, NULL);
                XtMainLoop();
        }

This will still kill the application.  To turn this behaviour off so that the
application is not killed, set the shell resource XmNdeleteResponse to
XmDO_NOTHING.  This means that users cannot kill your application via the
system menu, and may be a bad thing.

If you are running R3, Bob Hays (bobhays@spss.com) has suggested this:
"Trapping on the delete window atom does not work as I cannot force my action
routine to the top of the action list for the activity desired, so the window
manager kills my window anyway BEFORE I can do anything about it.  And, to
make matters worse, the window manager (Motif in this case) tacks its atoms
and handlers onto the window at some unknown point down the line after the
creation of the shell widget as far as I can tell.  So....

I have a procedure as an action routine for ClientMessage.  Then, if I get a
property change event on the window manager protocols, I then tack on
WM_SAVE_YOURSELF.  If I get this request, I clean up (it seems to happen on
WM_DELETE_WINDOW, BTW, if you remove WM_DELETE_WINDOW from the WM protocols
atom) and exit.  Works great and is less filling overall:-)."