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From: DAVISM@kcgl1.eng.ohio-state.edu (Michael T. Davis)
Newsgroups: comp.windows.x
Subject: Problem with Dwt List Box (callback data)
Message-ID: <3035@quanta.eng.ohio-state.edu>
Date: 14 Sep 89 19:28:53 GMT
Sender: news@quanta.eng.ohio-state.edu
Organization: Ohio State University
Lines: 50


	I am experiencing a problrm with the callback data structure passed
to my callback function for a DECwindows Toolkit (Dwt) List Box widget.  I
am running DECwindows under VMS 5.1-B on a VAXstation 3100.  Here's the
List Box set up code:

    list_box = DwtListBox ( main_window, "Verb List", 18, 38, NULL, 0, 4,
     NULL, NULL, True, False );
    XtAddCallback ( list_box, DwtNsingleCallback, list_callback, NULL );
    XtSetArg ( settings [ 0 ], DwtNsingleSelection, True );
    XtSetValues ( list_box, settings, 1 );

And here's the callback:

void list_callback ( widget, user_data, callback_data )
    Widget * widget;
    caddr_t user_data;
    DwtListBoxCallbackStruct callback_data;
{

#ifdef DEBUG
    printf ( "Item number = %d\nItem Length = %d\n",
     callback_data. item_number, callback_data. item_length );
#endif
    if ( callback_data. reason != DwtCRSingle )
        return;
    else
    {
        DwtListBoxSelectItem ( widget, callback_data. item, False );
        parse_verb ( & callback_data. item_number );
    }
}


The reason member and item_length of the callback data structure always have
bogus values in them and the item_number member is always 0.  All the structure
members stay constant, no matter which item I select with the pointer.  Is
there something really obvious I am forgetting, or what?

							Thanks,
							 Mike

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