HOWTO: Use CFormView in SDI and MDI Applications

ID: Q98598

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 4.2, 5.0, 6.0

SUMMARY

The CFormView class provides a convenient method to place controls into a view that is based on a dialog box template. The general procedure to use a CFormView is described in the documentation for the class and is illustrated in the VIEWEX and CHKBOOK sample applications provided with Microsoft Foundation Classes (MFC) versions 2.x and above. However, these applications do not demonstrate making the initial size of the frame window to be the same as the initial size of the form.

The following section lists the steps required to support creating a single document interface (SDI) or multiple document interface (MDI) application based on a CFormView, sizing the initial frame window around the form, changing the style of the frame, and closing an MDI document using a button in the form.

MORE INFORMATION

The following steps describe how to create an AppWizard generated application using the CFormView as the default view.

Use the AppWizard to generate an SDI or MDI application skeleton, stopping at step six of the AppWizard.

At step 6 of the AppWizard, select the view class and specify CformView as the base class using the Base class combo box. This will insert a dialog template with the proper styles set for your project's resource file.

Override the OnUpdate() member function and call UpdateData() as documented in the CFormView documentation to update the member variables with the current document data and to perform dialog data exchange (DDX). NOTE: UpdateData is not virtual and calling the base class ensures that the derived class DoDataExchange is called through standard polymorphism. The CFormView documentation states to call, not override UpdateData.

If you would like to set the initial size of the form view, override the OnInitialUpdate() function. The text below provides additional information about this step, which is slightly different in an SDI or MDI application.

Changing the Size of an SDI Main Frame Around a CFormView

To change the size of the main frame of an SDI application (that uses CFormView as its view class) to be the appropriate size for the form you designed in App Studio, override the OnInitialUpdate() function in your class derived from CFormView, as follows:


      void CMyFormView::OnInitialUpdate()
      {
         CFormView::OnInitialUpdate();
         GetParentFrame()->RecalcLayout();
         ResizeParentToFit(); // default argument is TRUE
      }

The ResizeParentToFit() function does not prevent the form from changing size when the user changes the size of the application main frame (scroll bars are added automatically if needed). To modify the style of the frame window that is the parent of a form view, you can override the PreCreateWindow() function in the CMainFrame class generated by AppWizard. For example, to remove the WS_THICKFRAME style and prevent the user from changing the size of the window, declare PreCreateWindow() in MAINFRM.H and add the following code to MAINFRM.CPP:


      BOOL CMainFrame::PreCreateWindow(CREATESTRUCT &cs)
      {
         cs.style &= ~WS_THICKFRAME;
         return CFrameWnd::PreCreateWindow(cs);
      }

Changing the Size of an MDI Child Frame Around a CFormView

The process of changing the size of an MDI child frame is similar to changing the size of a main frame for an SDI application, as explained above. However, the RecalcLayout() call is not required.

To change the size of an MDI child frame around a form view, override the OnInitialUpdate() function in your class derived from CFormView as follows:


      void CMDIFormView::OnInitialUpdate()
      {
         CFormView::OnInitialUpdate();
         ResizeParentToFit(); // Default argument is TRUE.
      }

If the application overrides the default argument to the ResizeParentToFit() function, essentially the same consequences occur as for an SDI application, as explained above. In addition, the child window may be too large for the enclosing MDI main frame or for the entire screen.

To change the style of the MDI child frame (for example, to remove the WS_THICKFRAME style so the user cannot change the size of the window), derive an MDI child window class and override the PreCreateWindow function as demonstrated in the SDI example above.

Closing an MDI Form with a Button

To create a button on a form that closes the document, use ClassWizard to add a message handler for the BN_CLICKED message to the CFormView class. Make sure that the buttons in CFormView do not have the default IDOK or IDCANCEL identifiers. If they do, ClassWizard creates incorrect entries in the message map and incorrect functions for the buttons.

Once the message handler is in place, you can simulate the Close command on the File menu with the following code:


      void CMyForm::OnClickedButton1()
      {
         PostMessage(WM_COMMAND, ID_FILE_CLOSE);
      }

This method to close a form prompts the user to save the file if the IsModified() member function associated with the document returns TRUE.

Additional query words: kbfasttips

Keywords : kbDocView kbMDI kbMFC KbUIDesign kbVC100 kbVC150 kbVC200 kbVC400 kbVC500 kbVC600 kbGrpMFCATL
Version : winnt:1.0,2.0,2.1,4.0 4.2,5.0,6.0
Platform : winnt
Issue type : kbhowto