PRB: PreCreateWindow() Not Called for CFormView

WINDOWS             | WINDOWS NT

The information in this article applies to:

• The Microsoft Foundation Classes (MFC) included with:

      - Microsoft Visual C++ for Windows, versions 1.0, 1.5, 1.51, 1.52
      - Microsoft Visual C++, 32-bit Edition, versions 1.0, 2.0, 2.1
  

SYMPTOMS

PreCreateWindow() for a CFormView derived class does not get called by the MFC framework during the creation process of a formview.

CAUSE

This is by design. During the creation of the view, the view's Create() function is called by the framework. This then calls CWnd::Create for all the views except CFormView. The CFormView class has its own Create, which calls ::CreateDialog to create the view. CWnd::Create has a call to PreCreateWindow while CFormView::Create does not. As a result, PreCreateWindow( ) for a CFormView derived class does not get called.

WORKAROUND

To change the initial size and location, override the frame window's PreCreateWindow(). To make other changes, override the virtual function, CFormView::Create().

STATUS

This behavior is by design.

MORE INFORMATION

PreCreateWindow() is generally used to alter the default values of the CREATESTRUCT structure before the window is created. This structure contains fields that determine the initial size, location, style, and class among other properties for the window. For CView derived objects, the size, location, and some of the style bits have no effect when modified. In general, the encapsulating frame window's PreCreateWindow() should be overridden and used instead. However, if you need to change the view's CREATESTRUCT, you can override PreCreateWindow() for the view, except for the CFormView (and CRecordView) class.

CFormView (and CRecordView) uses the dialog template to initialize most of its window properties. As a result, CFormView::Create() calls ::CreateDialog(), passing it the dialog template resource as one of its parameters. CView, CEditView, and CScrollView call CWnd::Create() which calls CWnd::CreateEx() where the CREATESTRUCT structure is filled and PreCreateWindow() is called before ::CreateWindowEx().

Typically, there is very little flexibility in changing the default construction parameters for a CFormView after the creation process has started. Some of the parameters that can be modified by PreCreateWindow for other views, like the class name, are ignored in the case of CFormView. See the implementation of CFormView::Create in the Viewform.cpp file for more details.

NOTE: Starting with MFC version 4.0, included with Visual C++ version 4.0, CFormView::Create() calls its PreCreateWindow() to get the prefered extended style. This is done before the modeless dialog is created.

REFERENCES

For more information, please see the MFC source library and Online Books.