FIX: LoadBarState and SaveBarState Increase .Ini File Size

• The Microsoft Foundation Classes (MFC), included with:
  • Microsoft Visual C++, 32-bit Editions, versions 2.0, 2.1

SYMPTOMS

The size of the .ini file associated with an application keeps increasing when CFrameWnd::LoadBarState and CFrameWnd::SaveBarState functions are used. The docktool sample can be used to reproduce the behavior. Open and close the sample application without modifying the toolbars. The .ini file size increases every time the application is closed.

CAUSE

This behavior is due to a bug in one of the helper functions of CControlBar. CFrameWnd::LoadBarState calls this function to set the state of a control bar. This function adds a trailing NULL element to the internal structure maintaining state information, without checking if one is already present. CFrameWnd::SaveBarState stores this extra element in the .ini file. The next time CFrameWnd::LoadBarState is called, another NULL element is added to the state information and the cycle continues.

RESOLUTION

To prevent the .ini file from growing, remove the extra element from file. This can be done after the information has been saved. The "Sample Code to Resolve Problem" section in this article shows how to implement this. It reads the information stored in the .ini file, strips extra trailing NULL elements, and saves the information back to the file. The code uses classes private to MFC, and the preprocessor directives ensure that the code is compatible with future versions of MFC.

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 the MFC libraries included with Microsoft Visual C++, 32-bit Edition, version 2.2.

MORE INFORMATION

The following code has been placed in the context of the DockTool sample. The modified code is between the

#if _MFC_VER < 0x0320
...
#endif 

Sample Code to Resolve Problem

// mainfrm.cpp : implementation of the CMainFrame class
// 
#include "stdafx.h"
#if _MFC_VER < 0x0320
// IMPORTANT : Conditional compilation directives are
// necessary to maintain compatibility with future versions of MFC
#include <afxpriv.h>
#endif
...
#if _MFC_VER < 0x0320
// IMPORTANT : Conditional compilation directives are
// necessary to maintain compatibility with future versions of MFC
/////////////////////////////////////////////////////////////////////////// 
// 
// _AFX_BARINFO - used for docking serialization
class _AFX_BARINFO : public CObject
{
public:
// Implementation
   _AFX_BARINFO();
// Attributes
   UINT m_nBarID;
   BOOL m_bVisible;
   BOOL m_bFloating;
   BOOL m_bHorz;
   BOOL m_bDockBar;
   CPoint m_pointPos;
   CPtrArray m_arrBarID;
   CControlBar* m_pBar;
   virtual void Serialize(CArchive& ar);
   BOOL LoadState(LPCTSTR lpszProfileName, int nIndex);
   BOOL SaveState(LPCTSTR lpszProfileName, int nIndex);
};
#endif
void CMainFrame::OnClose()
{
   // SaveBarState saves everything but the number of Columns in the
   // Palette; you need to do that yourself.
   SaveBarState(_T("General"));
#if _MFC_VER < 0x0320
// IMPORTANT : Conditional compilation directives are
// necessary to maintain compatibility with future versions of MFC
   CDockState state;
   state.LoadState(_T("General"));
      for (int i = 0; i < state.m_arrBarInfo.GetSize(); i++)
   {
      _AFX_BARINFO* pInfo = (_AFX_BARINFO*)state.m_arrBarInfo[i];
      int nSize = pInfo->m_arrBarID.GetSize();
      while ((nSize!=0) && (pInfo->m_arrBarID[nSize-1]==NULL))
      {
         nSize--;
         pInfo->m_arrBarID.RemoveAt(nSize);
      }
      if (nSize)
         pInfo->m_arrBarID.InsertAt(nSize, (void*)NULL);
   }
   state.SaveState(_T("General"));
#endif 

Additional query words: 2.00 2.10 3.0 3.1 3.00 3.10

Keywords : kbcode kbMFC KbUIDesign kbVC
Version : 2.00 2.10
Platform : NT WINDOWS
Issue type :