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

WINDOWS        | WINDOWS NT

The information in this article applies to:

• The Microsoft Foundation Classes (MFC) included with:

      - Microsoft Visual C++ for Windows, versions 1.5, 1.51, 1.52
      - Microsoft Visual C++, 32-bit Edition, versions 2.0, 2.1, 4.0, 4.1
  

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 probably don't want to do the same processing during a Print Preview close that you want to 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 .h file of CMainFrame class:

    {
    BOOL m_bPreview;  // TRUE in print preview mode; FALSE otherwise
    ...
    };

// In .cpp file of CMainFrame class:

    {
    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."