Q131792: PRB: OnClose() Is Called When Closing Print Preview Dialog Box

Article: Q131792
Product(s): Microsoft C Compiler
Version(s): winnt:
Operating System(s): 
Keyword(s): kbprint kbMFC kbPrinting kbVC150 kbVC200 kbVC400 kbVC410 kbGrpDSMFCATL
Last Modified: 11-SEP-2001

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The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++, versions 1.5, 1.51, 1.52 
   - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, versions 1.0, 2.0, 2.1, 4.0, 4.1 
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SYMPTOMS
========

OnClose() is called when the user closes the Print Preview dialog box.

CAUSE
=====

If your frame window class is CMainFrame, for example, you can override the
OnClose() member to perform special processing (such as putting up a message box
asking users if they really want to quit), but note that CMainFrame::OnClose()
is also called when the user dismisses the Print Preview dialog by pressing
ALT+F4 or by double-clicking the upper left corner of the dialog.

NOTE: OnClose() is not called when the user clicks the Close button in the Print
Preview dialog box.

RESOLUTION
==========

In your OnClose() function, you do not want to do the same processing during a
Print Preview close that you do during an application close. Therefore, you
should make a special case in the OnClose() code to check whether or not it is
being called from Print Preview.

The following code demonstrates how to modify the OnClose() to do nothing during
the Print Preview close.

  void CMainFrame::OnClose()
      {
      if (m_bPreview ||
         (AfxMessageBox(ID_EXIT_PROMPT, MB_YESNO) == IDYES))
          {
          CFrameWnd::OnClose();
          }
      }

In this example, ID_EXIT_PROMPT is a string table resource containing the string
that you want to display in the message box. In addition, m_bPreview is a member
that you need to add to the CMainFrame class; it is initialized to FALSE in the
constructor of the CMainFrame class. Then, the m_bPreview variable is set again
using an override of CFrameWnd::OnSetPreviewMode().

  // In .h file of CMainFrame class:
  class CMainFrame : public CFrameWnd
      {
      BOOL m_bPreview;  // TRUE in print preview mode; FALSE otherwise
      ...
      };

  // In .cpp file of CMainFrame class:
  CMainFrame::CMainFrame()
      {
      m_bPreview = FALSE;
      }

  void CMainFrame::OnSetPreviewMode(
      BOOL bPreview, CPrintPreviewState* pModeStuff)
      {
      m_bPreview = bPreview;
      CFrameWnd::OnSetPreviewMode(bPreview, pModeStuff);
      }

STATUS
======

This behavior is by design.

REFERENCES
==========

For more information on Print Preview, please see MFC Technote 30, "Print
Preview."

Additional query words: 2.50 2.51 2.52 2.10 3.00 3.10 2.00 3.0 3.1 4.00 4.10

======================================================================
Keywords          : kbprint kbMFC kbPrinting kbVC150 kbVC200 kbVC400 kbVC410 kbGrpDSMFCATL 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:
Issue type        : kbprb

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