BUG: SetMinHeight Does Not Work Correctly with CStatusBar

• The Microsoft Foundation Classes (MFC), included with:

      - Microsoft Visual C++, 32-bit Edition, versions 4.0, 4.1, 4.2, 5.0
  

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. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

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.

Keywords          : MfcUI vcbuglist500 kbui
Technology        : kbMfc
Version           : 4.0 4.1 4.2 5.0
Platform          : NT WINDOWS
Issue type        : kbbug