FIX: Undocking Toolbar May Disappear When Removed from Dockbar

The information in this article applies to:

• The Microsoft Foundation Classes (MFC) included with: Microsoft Visual C++, 32-bit Edition, version 2.0

SYMPTOMS

Attempting to undock or tear off a toolbar window from its dockbar window occasionally causes the toolbar to disappear when the mouse button is released.

CAUSE

This is caused by a bug in the MFC source code for CFrameWnd::CanDock(). Essentially, what happens is that the toolbar is being docked to an invisible dockbar. The CFrameWnd::CanDock() function doesn't check to see if the new docbar window is visible.

When you float a toolbar, and then close it by double-clicking the tiny control menu or icon, the window is not destroyed; it is just hidden. If you happen to drag and release another toolbar over the hidden toolbar, the toolbar being dragged is docked to the hidden toolbar.

RESOLUTION

To work around this problem, rebuild the project with Visual C++ version 2.1. If that is not an option for you, you can work around the problem by modifying the WINFRM2.CPP MFC source file and rebuilding the appropriate MFC library.

NOTE: Microsoft recommends against rebuilding the MFC30(D).DLL (the MFC Shared DLL). MFC30(D).DLL is a common component of many MFC applications. Rebuilding MFC30(D).DLL runs the risk of breaking other applications that rely on this component. If you do rebuild MFC30(D).DLL, please rename the DLL.

Steps to fix WINFRM2.CPP Directly

1. Replace following line of code in CFrameWnd::CanDock():

         if (pDockBar->IsDockBar() &&
            (pDockBar->m_dwStyle & dwDockStyle & CBRS_ALIGN_ANY) &&
            (!pDockBar->m_bFloating ||
         (dwDockStyle & pDockBar->m_dwStyle & CBRS_FLOAT_MULTI)))
   
      with this code:
   
         if (pDockBar->IsDockBar() && pDockBar->IsWindowVisible() &&
            (pDockBar->m_dwStyle & dwDockStyle & CBRS_ALIGN_ANY) &&
            (!pDockBar->m_bFloating ||
            (dwDockStyle & pDockBar->m_dwStyle & CBRS_FLOAT_MULTI)))
   
   

2. Rebuild the MFC library according to the instructions in the ..\MSVC\MFC\SRC\README.TXT file.

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++, 32-bit Edition, version 2.1.