Using Existing Dialogs with QMotifDialog

Modality with QDialog is different from Motif. The QDialog::exec() function does not return until the dialog is finished. In Motif, modality is simply a property of the shell, and the application programmer must write QDialog::exec() style functionality if they want that behavior.

Since we will be using QMotifDialog (which is a QDialog subclass), we will need to have an accept and a reject callback for each dialog we integrate with QMotifDialog. The predefined Motif dialogs have these already: the XmNokCallback and XmNcancelCallback callbacks. However, the Print dialog only has an accept callback (the XmdNprintCallback), but it does not have a reject callback. We need to add this.

This is easily done. We add an XtCallbackList for the XmNcancelCallback callback in Xmd/PrintP.h:

            XtCallbackList          print_callback;
            XtCallbackList          cancel_callback;

We add the XmNcancelCallback callback to the list of resources for the XmdPrint widget class in Xmd/Print.c:

      { XmdNprintCallback, XmCCallback, XmRCallback,
          sizeof(XtCallbackList),
          XtOffsetOf( XmdPrintRec, print.print_callback ),
          XmRPointer, (XtPointer) NULL },
      { XmNcancelCallback, XmCCallback, XmRCallback,
          sizeof(XtCallbackList),
          XtOffsetOf( XmdPrintRec, print.cancel_callback ),
          XmRPointer, (XtPointer) NULL }

We need to activate this callback whenever we unmanage the widget and do not activate the print callback, which is in the do_help_cb() function:

    do_help_cb(Widget button, Widget pw, XtPointer ignore)
    {
      XmdPrintWidget print = (XmdPrintWidget) pw;
      XmAnyCallbackStruct cb;

      cb.reason = XmCR_HELP;
      cb.event = NULL;

      XtCallCallbackList(pw, print -> manager.help_callback, (XtPointer) &cb);

      cb.reason = XmCR_CANCEL;
      XtCallCallbackList( pw, print->print.cancel_callback, (XtPointer) &cb );

      XtUnmanageChild(pw);
    }

... and in the unmanage_cb() function:

    unmanage_cb(Widget button, Widget pw, XtPointer ignore)
    {
      XmdPrintWidget print = (XmdPrintWidget) pw;

      XmAnyCallbackStruct cb;
      cb.reason = XmCR_CANCEL;
      cb.event = NULL;
      XtCallCallbackList( pw, print->print.cancel_callback, (XtPointer) &cb );

      XtUnmanageChild(pw);
    }

Integrating the Print Dialog

    #include <qmotifdialog.h>

        void ShowPrintDialog(Widget, XtPointer, XmPushButtonCallbackStruct *);

      XtAddCallback(file_menu[FILE_PRINT], XmNactivateCallback,
                    (XtCallbackProc) ShowPrintDialog, (XtPointer) &toplevel);

    void ShowPrintDialog(Widget, XtPointer client_data,
                         XmPushButtonCallbackStruct *)
    {
        QMotifDialog dialog( (QWidget *) client_data );
        (void) XtCreateWidget( "print dialog", xmdPrintWidgetClass,
                               dialog.shell(), NULL, 0 );

        // the print callback calls QMotifDialog::acceptCallback()
        XtAddCallback( dialog.dialog(), XmdNprintCallback,
                       (XtCallbackProc) QMotifDialog::acceptCallback, &dialog );
        // the cancel callback calls QMotifDialog::rejectCallback()
        XtAddCallback( dialog.dialog(), XmNcancelCallback,
                       (XtCallbackProc) QMotifDialog::rejectCallback, &dialog );

        // the print callback also calls the original Print() function
        XtAddCallback( dialog.dialog(), XmdNprintCallback,
                       (XtCallbackProc) Print, NULL );

        dialog.exec();
    }