PRB: Modal Property Sheet Not Modal in Propdlg Sample

The information in this article applies to:

• The Microsoft Foundation Classes (MFC) included with: Microsoft Visual C++ for Windows, version 1.52

SYMPTOMS

A modal property sheet brougt up by running the PROPDLG sample allows you to switch to other windows (such as the view window) in the application, and choose menu items. This is not proper behavior for a modal property sheet.

This problem occurs only with the Propdlg sample included with Visual C++ version 1.52. It does not occur in the Propdlg sample included with the 32-bit versions of Visual C++.

CAUSE

This problem results from passing "this" to the constructor for the CModalShapePropSheet making the view the parent of the property sheet:

   void CShapesView::OnPropertySheetWithPreview()
   ...
       m_pModalShapePropSheet = new CModalShapePropSheet(this);

   // find parent HWND
   HWND hWndTopLevel;
   CWnd* pParentWnd = CWnd::FromHandle(
       AfxGetSafeOwner(m_pParentWnd, &hWndTopLevel));
   if (hWndTopLevel != NULL)
       ::EnableWindow(hWndTopLevel, FALSE);

    // find parent HWND
    CWnd* pParentWnd = CWnd::FromHandle(AfxGetSafeOwner(m_pParentWnd));

RESOLUTION

Pass NULL or a pointer to the application's main frame window as the parent to the property sheet to correct this behavior. This works because AfxGetSafeOwner() returns the top level window in either of these cases as the main frame window. Later, in the CPropertySheet::DoModal() function, a call to pParentWnd->EnableWindow(FALSE) causes the top level window to be disabled.

MORE INFORMATION

Steps to Reproduce Behavior

1. Run the PROPDLG sample included with Visual C++ version 1.52.

2. Select a shape.

3. On the Object menu, click Property Sheet with Preview. This brings up a modal property sheet.

4. Observe that you are able to move to other windows.