HOWTO: Change Window Attributes in an MFC Application

ID: Q99847

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 2.0, 2.1, 4.0

SUMMARY

To change the default window attributes used by a framework application created in AppWizard, override the window's PreCreateWindow() virtual member function. PreCreateWindow() allows an application to access the creation process normally processed internally by the CDocTemplate class. The framework calls PreCreateWindow() just prior to creating the window. By modifying the CREATESTRUCT structure parameter to PreCreateWindow(), your application can change the attributes used to create the window.

MORE INFORMATION

The CTRLBARS sample application, provided with the Microsoft Foundation Class Library, demonstrates this technique to change window attributes. Note that depending on what your application changes in PreCreateWindow(), it may be necessary to call the base class implementation.

In a single document interface (SDI) application, the default window style in the framework is a combination of the WS_OVERLAPPEDWINDOW and FWS_ADDTOTITLE styles. FWS_ADDTOTITLE is a framework-specific style that instructs the framework to add the document title to the window's caption. To change the window attributes in an SDI application, override the PreCreateWindow() function in your class derived form CFrameWnd. For example:


   BOOL CMainFrame::PreCreateWindow(CREATESTRUCT& cs)
   {
      // Create a window without min/max buttons or sizable border
      cs.style = WS_OVERLAPPED | WS_SYSMENU | WS_BORDER;

      // Size the window to 1/3 screen size and center it
      cs.cy = ::GetSystemMetrics(SM_CYSCREEN) / 3;
      cs.cx = ::GetSystemMetrics(SM_CXSCREEN) / 3;
      cs.y = ((cs.cy * 3) - cs.cy) / 2;
      cs.x = ((cs.cx * 3) - cs.cx) / 2;

      return CFrameWnd::PreCreateWindow(cs);
   }

A little more work is required to change the window style of a child window in a multiple document interface (MDI) application. By default, an MDI application generated in AppWizard uses the default CMDIChildWnd class defined in the Microsoft Foundation Class Library. To change the window style of an MDI child window, your application must derive a new class from CMDIChildWnd and replace all references to CMDIChildWnd in your project with references to the new class. Most likely, the only reference to CMDIChildWnd in the application is located in your application's InitInstance() member function.

The default window style used in an MDI application is a combination of the WS_CHILD, WS_OVERLAPPEDWINDOW, and FWS_ADDTOTITLE styles. To change the window attributes of an MDI application's child windows, override the PreCreateWindow() function in your class derived from CMDIChildWnd. For example:


   BOOL CMyChildWnd::PreCreateWindow(CREATESTRUCT& cs)
   {
      // Create a child window without the maximize button
      cs.style &= ~WS_MAXIMIZEBOX;
      return CMDIChildWnd::PreCreateWindow(cs);
   }

For more information about the PreCreateWindow() function, please refer to the Microsoft Visual C++ "Class Library Reference, Volume 1," or to the Visual C++ online help files and Visual C++ 4.0 Books Online.

Additional query words:

Keywords : kbMDI kbMFC KbUIDesign kbVC100 kbVC150 kbVC200 kbVC400 kbVC500 kbVC600 kbWndwClass kbGrpMFCATL kbArchitecture
Version : winnt:2.0,2.1,4.0
Platform : winnt
Issue type : kbhowto