Q151031: FIX: SetMinHeight Does Not Work Correctly with CStatusBar

Article: Q151031
Product(s): Microsoft C Compiler
Version(s): winnt:
Operating System(s): 
Keyword(s): kbui kbMFC kbStatBar KbUIDesign kbVC400bug kbVC410bug kbVC420bug kbVC500bug kbVC600fix
Last Modified: 30-JUL-2001

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The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, versions 4.0, 4.1, 4.2 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 
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SYMPTOMS
========

Using the SetMinHeight function to change the height of a CStatusBar object has
no effect.

CAUSE
=====

The CStatusBar class maintains the height of the status window control in a
member variable named m_nMinHeight. The m_nMinHeight variable is not updated
correctly when the SetMinHeight function is used to change the height of the
status bar.

RESOLUTION
==========

You can work around this problem by setting m_nMinHeight to the correct value in
response to SetMinHeight. This is accomplished by deriving a class from
CStatusBar and handling the SB_SETMINHEIGHT message. In this handler, call
Default(), and then set m_nMinHeight to the new height.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This problem was corrected in Visual C++ version 6.0.

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

The sample code below illustrates how to work around the problem. Use the
CMyStatusBar class instead of CStatusBar if you want to change the height of the
status bar using SetMinHeight function. Be sure to call RecalcLayout on the
parent of the status bar to see this change in height immediately.

NOTE: The workaround uses the undocumented m_nMinHeight member variable of
CStatusBar. Hence the code in the workaround may not be compatible with future
versions of MFC.

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

     // MyStatusBar.h : header file
     // 

     //////////////////////////////////////////////////////////////////// 
     // CMyStatusBar window

     #ifndef __MYSTATUSBAR_H__
     #define __MYSTATUSBAR_H__

     class CMyStatusBar : public CStatusBar
     {
     // Construction
     public:
          CMyStatusBar() {}

     // Implementation
     public:
          virtual ~CMyStatusBar() {}

          // Generated message map functions
     protected:
          //{{AFX_MSG(CMyStatusBar)
          //NOTE-the ClassWizard will add and remove member functions here.
          //}}AFX_MSG

     #if _MFC_VER == 0x0400 || _MFC_VER == 0x0410 || _MFC_VER == 0x420 ||\ 
     _MFC_VER == 0x421

           afx_msg LRESULT OnSetMinHeight(WPARAM wParam, LPARAM);
     #endif

          DECLARE_MESSAGE_MAP()
     };

     #endif //__MYSTATUSBAR_H__

     //////////////////////////////////////////////////////////////////// 

     // MyStatusBar.cpp : implementation file
     // 

     #include "stdafx.h"
     #include "MyStatusBar.h"

     #ifdef _DEBUG
     #define new DEBUG_NEW
     #undef THIS_FILE
     static char THIS_FILE[] = __FILE__;
     #endif

     //////////////////////////////////////////////////////////////////// 
     // CMyStatusBar

     BEGIN_MESSAGE_MAP(CMyStatusBar, CStatusBar)
          //{{AFX_MSG_MAP(CMyStatusBar)
          //NOTE-the ClassWizard will add and remove mapping macros here.
          //}}AFX_MSG_MAP

     #if _MFC_VER == 0x0400 || _MFC_VER == 0x0410 || _MFC_VER == 0x420 ||\ 
     _MFC_VER == 0x421

          ON_MESSAGE(SB_SETMINHEIGHT, OnSetMinHeight)
     #endif

     END_MESSAGE_MAP()

     ///////////////////////////////////////////////////////////////////// 
     // CMyStatusBar message handlers

     #if _MFC_VER == 0x0400 || _MFC_VER == 0x0410 || _MFC_VER == 0x420 ||\ 
     _MFC_VER == 0x421

     LRESULT CMyStatusBar::OnSetMinHeight(WPARAM wParam, LPARAM)
     {
          LRESULT lResult = Default();
          m_nMinHeight = wParam;
          return lResult;
     }
     #endif

REFERENCES
==========

For more information, please see: Visual C++ Books Online, and the Win32 SDK
documentation.

Additional query words:

======================================================================
Keywords          : kbui kbMFC kbStatBar KbUIDesign kbVC400bug kbVC410bug kbVC420bug kbVC500bug kbVC600fix kbGrpDSMFCATL kbNoUpdate 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:
Issue type        : kbbug
Solution Type     : kbfix

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