FIX: ResizeParentToFit Won't Work w/ CScrollView on Windows 95

The information in this article applies to:

• The Microsoft Foundation Classes (MFC) included with: Microsoft Visual C++, 32-bit Edition, version 2.2

SYMPTOMS

A CScrollView that uses ResizeParentToFit to force its parent to resize itself such that the client area is the same size as the CScrollView doesn't work properly. The parent frame window will be very nearly the correct size, but it will still have vertical and horizontal scroll bars.

CFormView, which is derived from CScrollView, will have the same problem.

CAUSE

The bug is in the ResizeParentToFit function. The ResizeParentToFit function does not properly account for cases where the child window is not located at location (0,0).

The version of Visual C++ listed at the top of this article has been modified. MFC was changed so that a CFormView will have the properly sunken-edge (or 3D) look that a client window should have under Windows 95. This change was done by adding the WS_EX_CLIENTEDGE style to all CFormView objects when they are created. Because of this change the client area of the CFormView is no longer at position (0,0), so ResizeParentToFit fails to work correctly.

RESOLUTION

Override the ResizeParentToFit function, and modify it to do the proper calculations for your CFormView-derived class. The code for ResizeParentToFit can be found in the \MSVC20\MFC\SRC directory in the Viewscrl.cpp file. Implement this code in your application by first declaring it in your class, as in this example:

protected:

   void ResizeParentToFit(BOOL bShrinkOnly = TRUE);

1. Change the assert that uses MM_NONE to use 0. MM_NONE is a special mapping mode defined for the CScrollView class. It is defined in Viewscrl.cpp as 0; therefore, it will not be available for your derived class.

   Change this:

         ASSERT( m_nMapMode != MM_NONE);
   

   To this:

         ASSERT( m_nMapMode != 0);
   

2. Account for the offset of the client area.

   Change this:

         ...
         CalcWindowRect(rectView, CWnd::adjustOutside);
         if (bShrinkOnly)
         ...
   

   To this:

         ...
         CalcWindowRect(rectView, CWnd::adjustOutside);
         rectView.OffsetRect(-rectView.left, -rectView.top);
         ASSERT(rectView.left == 0 && rectView.top == 0);
         if (bShrinkOnly)
         ...
   

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 version of MFC that ships with Microsoft Visual C++, 32-bit Edition, version 4.0.