Q103788: INFO: Creating a Modeless Dialog Box with MFC Libraries

Article: Q103788
Product(s): Microsoft C Compiler
Version(s): winnt:1.0,2.0,2.1,4.0
Operating System(s): 
Keyword(s): kbDlg kbMFC KbUIDesign kbVC100 kbVC150 kbVC200 kbVC400 kbGrpDSMFCATL
Last Modified: 07-MAY-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++ for Windows, 16-bit edition, versions 1.0, 1.5, 1.51, 1.52 
   - Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 2.1, 4.0 
-------------------------------------------------------------------------------

This article demonstrates how to create a modeless dialog box using a
dialog-box template resource  using MFC.

To build a CModeless dialog box, the following steps should be
followed:

1. Create a dialog class derived from CDialog and override the Create() member
  function of CDialog. For example, you might have code that resembles the
  following:

        class CModeless: public CDialog
             {
               .
               .
               .
               public:
                   CModeless(){ }
                   BOOL Create(UINT nID, CWnd * pWnd)
                        { return CDialog::Create(nID,pWnd);}
               .
               .
               .
             };

  NOTE: You could let ClassWizard generate the dialog class and then simply add
  the Create() function.

2. Write code to construct an object of the dialog class and create the dialog
  box window. For example, if you have a menu item that should display the
  dialog box, you might have code that resembles the following:

        void CMainFrame::OnModeless()
          {
              pdlg = new CModeless;
              pdlg->Create(IDD_DIALOG1,this);
          }

  where CMainFrame::pdlg is defined as:

  CModeless * pdlg;

  NOTE: It is important to allocate the object on the heap rather than the stack
  if you want to prevent the modeless dialog box from being destroyed when the
  function is exited.

3. You must call CWnd::DestroyWindow() in OnCancel, or whenever the modeless
  dialog box needs to be destroyed.

        void CModeless::OnCancel()
        {
            DestroyWindow();
        }

4. Override CWnd::PostNcDestroy() in your dialog class to delete the dialog box
  object:

     virtual void CModeless::PostNcDestroy() {delete this;}

  PostNcDestroy() is a virtual member function of the CWnd class that is called
  by the OnNcDestroy() function.

A modeless dialog class will typically override the OnOK() and
OnCancel() member functions to call DestroyWindow() and should not
call the base class CDialog::OnOK() and CDialog::OnCancel() functions.
The CDialog::OnOK() and CDialog::OnCancel() functions call
EndDialog(). EndDialog() should be called only when using modal dialog
boxes.

If you are using Dialog Data Exchange (DDX) and Dialog Data Validation
(DDV), you're OnOK() handler for your dialog class might resemble the
following:

     void CModeless::OnOK()
     {
             if (!UpdateData(TRUE))
               {
                 TRACE0("UpdateData failed during dialog termination\n");
                 // The UpdateData routine will set focus to correct item
                 return;
               }
             DestroyWindow();
     }

SUMMARY
=======



Additional query words: kbinf 1.00 1.50 2.00 2.10 2.50 2.51 2.52 3.00 3.10 4.00

======================================================================
Keywords          : kbDlg kbMFC KbUIDesign kbVC100 kbVC150 kbVC200 kbVC400 kbGrpDSMFCATL 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:1.0,2.0,2.1,4.0
Issue type        : kbinfo

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.