Q111768: PRB: Control Bar Not Visible After Calling Create

Article: Q111768
Product(s): Microsoft C Compiler
Version(s): winnt:2.0,2.1,4.0
Operating System(s): 
Keyword(s): kbMFC kbToolbar KbUIDesign kbVC kbGrpDSMFCATL kbMFCCtrlBar
Last Modified: 07-MAY-2001

-------------------------------------------------------------------------------
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 
-------------------------------------------------------------------------------

SYMPTOMS
========

A control bar is not immediately visible after a call to Create. The control bar
becomes visible only when the parent window is resized (or minimized\maximized).
This behavior is true for all the built-in framework classes derived from
CControlBar:

     CDialogBar
     CToolBar
     CStatusBar

CAUSE
=====

A control bar is initially placed at position (0,0) with size (0,0) so that the
parent frame can control the size and position. The size and position are
recomputed when a call is made to RecalcLayout. If a call is made to Create,
then the control bar will not become visible until RecalcLayout is called for
the parent frame window. The control bar becomes visible when the main frame
window is resized, because CFrameWnd has a WM_SIZE handler that calls
RecalcLayout.

RESOLUTION
==========

Use one of the following to resolve this issue:

- If the control bar is ALWAYS going to be attached to the frame window when it
  is created, then create the control bar once in the OnCreate message handler
  for the frame window. This would apply to the main frame window of an SDI
  (CFrameWnd) or MDI (CMDIFrameWnd) application, or to an MDI Child Window
  (CMDIChildWnd).

- If the control is to be created dynamically (for example, a toolbar that
  pops-up only under certain circumstances), make a call to RecalcLayout for
  the parent frame window to cause the control bar to be properly resized and
  drawn.

MORE INFORMATION
================

There are two code segments below that show how to create a CDialogBar attached
to a CMDIChildWnd. The first sample creates a CDialogBar as soon as the child
window is created (that is, the child window always has the dialog bar). The
second sample shows a function that will properly create and display a dialog
bar at any time.

Sample Code
-----------

     /* Compile options needed: None
        Sample 1 - Override OnCreate.
     
        Note that the dialog template is called IDD_CHILDBAR
        and that CMyMDIChild has a member variable declaration:
        CDialogBar m_dlgbar;
     */ 
     int CMyMDIChild::OnCreate(LPCREATESTRUCT lpCreateStruct)
     {
          if (CMDIChildWnd::OnCreate(lpCreateStruct) == -1)
               return -1;
     
         m_dlgbar.Create(this,IDD_CHILDBAR,CBRS_TOP,115);
     
          return 0;
     }
     
     /*
       Sample 2 - Creating a dialog bar at any time.
       Note that the dialog template is called IDD_CHILDBAR
       and that CMyMDIChildWnd has a member variable declaration:
       CDialogBar *m_pdlgbar;
     */ 
     void CMyMDIChild::CreateDialogBar()
     {
         m_pDlgBar = new CDialogBar();
         m_pDlgBar->Create(this,IDD_CHILDBAR,CBRS_TOP,115);
         RecalcLayout();
     }

Because you are allocating a CDialogBar object, you need to call delete m_pDlgBar
when you close the application or there will be a memory leak.

Additional query words: WM_SIZE CRect tool bar status tool-bar status-bar statusbar

======================================================================
Keywords          : kbMFC kbToolbar KbUIDesign kbVC kbGrpDSMFCATL kbMFCCtrlBar 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:2.0,2.1,4.0
Issue type        : kbprb

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.