How To Set Default Values for ActiveX Control Stock Properties

MORE INFORMATION

Using AppWizard to generate an MFC ActiveX control project creates a COleControl-derived class with an overridden DoPropExchange() member function. By default, the overridden DoPropExchange() calls COleControl::DoPropExchange(). This in turn calls COleControl::ExchangeStockProps(), which contains the MFC code for serializing stock properties.

Within this function, MFC (pre version 4.2) uses the COleControl::m_dwStockPropMask protected member variable to determine which stock properties you have added with Class Wizard. This mask can be modified in your DoPropExchange() to force MFC to ignore existing stock properties and therefore allow you to add your own code. Ideally, you should copy the relevant code already present in COleControl::ExchangeStockProps(), and then modify it as necessary.

In MFC version 4.2 and later, a different variable is used as the Stock Property mask. In the following code, GetStockPropMask and SetStockPropMask hide these differences.

The following sample code shows how to accomplish this for the Caption stock property by modifying step three of the Circ OLE Control tutorial.

Sample Code

   class CCirc3Ctrl : public COleControl
   {
   ...
   public:
       void SetStockPropMask(DWORD dwStockPropMask);
       DWORD GetStockPropMask();
   ...
   }

   // MANUAL CONTROL OF MAKING Caption PERSISTANT.
   // To test the initialization of the caption stock property
   // replace the circle3 samples DoPropExchange function with the
   // following version.

   // These #defines can be found in the Ctlprop.cpp file and are given
   // here to remove the need to continually track them down. In the
   // code, only STOCKPROP_CAPTION is used.
   #define STOCKPROP_BACKCOLOR     0x00000001
   #define STOCKPROP_CAPTION       0x00000002
   #define STOCKPROP_FONT          0x00000004
   #define STOCKPROP_FORECOLOR     0x00000008
   #define STOCKPROP_TEXT          0x00000010
   #define STOCKPROP_BORDERSTYLE   0x00000020
   #define STOCKPROP_ENABLED       0x00000040
   //**************************************************************
   #define STOCKPROP_APPEARANCE    0x00000080   // New in VC 5.0
   //**************************************************************

   // Helper method for setting the Stock property mask.
   void CCirc3Ctrl::SetStockPropMask(DWORD dwStockPropMask)
   {
   #if _MFC_VER >= 0x0420   // MFC version >= v4.2
       *GetDispatchMap()->lpStockPropMask = dwStockPropMask;
   #else                    // MFC version < v4.2
       m_dwStockPropMask = dwStockPropMask;
   #endif
   }

   // Helper method to Get the Stock property mask.
   DWORD CCirc3Ctrl::GetStockPropMask()
   {
   #if _MFC_VER >= 0x0420   // MFC version >= v4.2
       return COleControl::GetStockPropMask();
   #else                    // MFC version < v4.2
       return m_dwStockPropMask;
   #endif
   }

   void CCirc3Ctrl::DoPropExchange(CPropExchange* pPX)
   {
       ExchangeVersion(pPX, MAKELONG(_wVerMinor, _wVerMajor));
   // Need to comment out the following line since it will be <BR/>
   // called later.
   // COleControl::DoPropExchange(pPX);

    // Handle Property Exchange of the Stock Property Caption ourselves.
    BOOL bLoading = pPX->IsLoading();
    CString strText;

    if (!bLoading)
        strText = InternalGetText();

    PX_String(pPX,_T("Caption"),strText,_T("Caption"));
    if (bLoading) {
        TRY
        SetText(strText);
        END_TRY
    }

    // Bypass MFC's Property Exchange of the Stock Property Caption.
    DWORD dwStockPropMask = GetStockPropMask();
    DWORD tempMask = dwStockPropMask;

    // Remove all stock property flags we are handling from tempMask.
    tempMask &= ~STOCKPROP_CAPTION;
    SetStockPropMask(tempMask);

    // Let MFC handle any stock properties that we aren't.
    COleControl::DoPropExchange(pPX);

    // Reset the Stock Property Mask.
    SetStockPropMask(dwStockPropMask);

    if (pPX->GetVersion() == (DWORD)MAKELONG(_wVerMinor, _wVerMajor))
    {
        PX_Bool(pPX, _T("CircleShape"), m_circleShape, TRUE);
        PX_Short(pPX, _T("CircleOffset"), m_circleOffset, 0);
        PX_Long(pPX, _T("FlashColor"), (long &)m_flashColor,
        RGB(0xFF, 0x00, 0x00));
        PX_String(pPX, _T("Note"), m_note, _T(""));
    }
    else if (pPX->IsLoading())
    {
        // Skip over persistent data.
        BOOL bDummy;
        short sDummy;
        long lDummy;
        CString strDummy;
        PX_Bool(pPX, _T("CircleShape"), bDummy, FALSE);
        PX_Short(pPX, _T("CircleOffset"), sDummy, 0);
        PX_Long(pPX, _T("FlashColor"), lDummy, 0);
        PX_String(pPX, _T("Note"), strDummy, _T(""));

        // Force property values to these defaults.
        m_circleShape = TRUE;
        m_circleOffset = 0;
        m_flashColor = RGB(0xFF, 0x00, 0x00);
        m_note = _T("");
    }
   }