Accessing OLE 2.0 Embedded Object Dirties OLE 1.0 Client

ID: Q118613

1.50 1.51 1.52 | 2.00 2.10 4.00 4.10

WINDOWS        | WINDOWS NT

kbprg

The information in this article applies to:

The Microsoft Foundation Classes (MFC) included with:

    - Microsoft Visual C++ for Windows, versions 1.5, 1.51, and 1.52
    - Microsoft Visual C++ 32-bit Edition, versions 2.0, 2.1,
      4.0, and 4.1

SUMMARY

When an OLE 2.0 embedded object is opened and closed in an OLE 1.0 client without being modified, the client document needs to be updated (that is, marked as "dirty"). This causes the client to ask whether the user wants to save the document.

To prevent the client from marking its document as dirty, you must modify the implementations of IOleObject and IDataObject in your OLE 2.0 server. In an MFC-based server application, this is most conveniently done by deriving a new class from COleServerDoc and changing the application's server document class so that it is derived from the new class.

MORE INFORMATION

This behavior can be observed using the Windows Write applet with any of the MFC sample servers. To observe this behavior, perform the following steps:

1. Open a document in Write.

2. Embed a new object in the document.

3. Save the document.

4. Open the embedded object.

5. Immediately close the object to return to Write.

6. Exit Write. (You will be asked whether you want to save the updated

   document.)

When an OLE 2.0 embedded object is closed, the object calls IAdviseSink::OnClose() to notify its container. The OLE translation layer simply translates this into a client callback of OLE_CLOSE, which causes the client to receive an update of the embedded object's metafile. This in turn causes the client to think its document is dirty and needs to be saved.

To avoid this behavior, perform the following steps:

1. Add a flag to the OLE 2.0 object that supports IDataObject,

   IPersistStorage, and IOleObject.

2. During IOleObject::OnClose, set the flag to TRUE before the call to

   IAdviseHolder::SendOnClose() and reset it after the call returns.

3. Modify the implementations of IDataObject::GetData() and

   IDataObject::GetDataHere() to return E_FAIL when m_bDontSave is TRUE.

To implement the above steps using MFC, perform the following steps:

1. Create a new class, COleServerDocEx, derived from COleServerDoc.

2. Add a member variable, m_bDontSave, to COleServerDocEx.

3. Override OnCloseDocument() in COleServerDocEx. Set m_bDontSave to TRUE,

   call the base class function, then reset m_bDontSave. This effectively
   brackets the call to IAdviseHolder::OnClose().

4. Reimplement the IDataObject interface in COleServerDocEx. For all

   functions except GetData() and GetDataHere(), simply delegate to the
   COleServerDoc implementation of IDataObject.

5. In the implementations of GetData() and GetDataHere(), return E_FAIL if

   m_bDontSave is TRUE.

6. Modify your application's document class so it is derived from

   COleServerDocEx rather than COleServerDoc.

Sample Code

The following code implements the COleServerDocEx class mentioned above:

   //////////////////////////////////////////////////////////////// 
   // olesvrex.h : interface of the COleServerDocEx class
   // 

   class COleServerDocEx : public COleServerDoc
   {
      DECLARE_DYNAMIC(COleServerDocEx)

   // Constructors and Destructors
   public:
      COleServerDocEx();

   // Implementation
   public:
      virtual ~COleServerDocEx();
   #ifdef _DEBUG
      virtual void AssertValid() const;
      virtual void Dump(CDumpContext& dc) const;
   #endif

      // overridables for implementation
      virtual void OnCloseDocument();

   protected:
      BOOL m_bDontSave;

   // Message Maps
   protected:
      //{{AFX_MSG(COleServerDocEx)
      //}}AFX_MSG
      DECLARE_MESSAGE_MAP()

   // Interface Maps
   protected:
      BEGIN_INTERFACE_PART(DataObjectEx, IDataObject)
         STDMETHOD(GetData)(LPFORMATETC, LPSTGMEDIUM);
         STDMETHOD(GetDataHere)(LPFORMATETC, LPSTGMEDIUM);
         STDMETHOD(QueryGetData)(LPFORMATETC);
         STDMETHOD(GetCanonicalFormatEtc)(LPFORMATETC, LPFORMATETC);
         STDMETHOD(SetData)(LPFORMATETC, LPSTGMEDIUM, BOOL);
         STDMETHOD(EnumFormatEtc)(DWORD, LPENUMFORMATETC FAR*);
         STDMETHOD(DAdvise)(LPFORMATETC, DWORD, LPADVISESINK, LPDWORD);
         STDMETHOD(DUnadvise)(DWORD);
         STDMETHOD(EnumDAdvise)(LPENUMSTATDATA FAR*);
      END_INTERFACE_PART(DataObjectEx)

      DECLARE_INTERFACE_MAP()

   };

   // 
   // End of olesvrex.h
   //////////////////////////////////////////////////////////////// 

   //////////////////////////////////////////////////////////////// 
   // 
   // olesvrex.cpp : implementation of the COleServerDocEx class

   #include "stdafx.h"
   #include "olesvrex.h"

   #ifdef _DEBUG
      #undef THIS_FILE
      static char BASED_CODE THIS_FILE[] = __FILE__;
   #endif

   /////////////////////////////////////////////////////////////// 
   // COleServerDocEx

   IMPLEMENT_DYNAMIC(COleServerDocEx, COleServerDoc)

   BEGIN_MESSAGE_MAP(COleServerDocEx, COleServerDoc)
      //{{AFX_MSG_MAP(COleServerDocEx)
      //}}AFX_MSG_MAP
   END_MESSAGE_MAP()

   /////////////////////////////////////////////////////////////// 
   // COleServerDocEx construction/destruction

   COleServerDocEx::COleServerDocEx()
   {
      m_bDontSave = FALSE;
   }

   COleServerDocEx::~COleServerDocEx()
   {
   }

   //////////////////////////////////////////////////////////////// 
   // COleServerDocEx default command handling

   void COleServerDocEx::OnCloseDocument()
   {
      m_bDontSave = TRUE;
      COleServerDoc::OnCloseDocument();
      m_bDontSave = FALSE;
   }

   //////////////////////////////////////////////////////////////// 
   // COleServerDocEx OLE interface implementation

   BEGIN_INTERFACE_MAP(COleServerDocEx, COleServerDoc)
      INTERFACE_PART(COleServerDocEx, IID_IDataObject, DataObjectEx)
   END_INTERFACE_MAP()

   //////////////////////////////////////////////////////////////// 
   // COleServerDocEx::XDataObjectEx

   STDMETHODIMP_(ULONG) COleServerDocEx::XDataObjectEx::AddRef()
   {
      METHOD_PROLOGUE(COleServerDocEx, DataObjectEx)
      return (ULONG)pThis->ExternalAddRef();
   }

   STDMETHODIMP_(ULONG) COleServerDocEx::XDataObjectEx::Release()
   {
      METHOD_PROLOGUE(COleServerDocEx, DataObjectEx)
      return (ULONG)pThis->ExternalRelease();
   }

   STDMETHODIMP COleServerDocEx::XDataObjectEx::QueryInterface(
      REFIID iid, LPVOID far* ppvObj)
   {
      METHOD_PROLOGUE(COleServerDocEx, DataObjectEx)
      return (HRESULT)pThis->ExternalQueryInterface(&iid, ppvObj);
   }

   STDMETHODIMP COleServerDocEx::XDataObjectEx::GetData(
      LPFORMATETC lpFormatEtc, LPSTGMEDIUM lpStgMedium)
   {
      METHOD_PROLOGUE(COleServerDocEx, DataObjectEx)
      ASSERT_VALID(pThis);

      if (pThis->m_bDontSave)
         return ResultFromScode(E_FAIL);

      return pThis->m_xDataObject.GetData(lpFormatEtc, lpStgMedium);
   }

   STDMETHODIMP COleServerDocEx::XDataObjectEx::GetDataHere(
      LPFORMATETC lpFormatEtc, LPSTGMEDIUM lpStgMedium)
   {
      METHOD_PROLOGUE(COleServerDocEx, DataObjectEx)
      ASSERT_VALID(pThis);

      if (pThis->m_bDontSave)
         return ResultFromScode(E_FAIL);

      return pThis->m_xDataObject.GetDataHere(lpFormatEtc, lpStgMedium);
   }

   STDMETHODIMP COleServerDocEx::XDataObjectEx::QueryGetData(
      LPFORMATETC lpFormatEtc)
   {
      METHOD_PROLOGUE(COleServerDocEx, DataObjectEx)
      ASSERT_VALID(pThis);

      return pThis->m_xDataObject.QueryGetData(lpFormatEtc);
   }

   STDMETHODIMP COleServerDocEx::XDataObjectEx::GetCanonicalFormatEtc(
      LPFORMATETC lpFormatEtcIn, LPFORMATETC lpFormatEtcOut)
   {
      METHOD_PROLOGUE(COleServerDocEx, DataObjectEx)
      ASSERT_VALID(pThis);

      return pThis->m_xDataObject.GetCanonicalFormatEtc(lpFormatEtcIn,
                                                        lpFormatEtcOut);
   }

   STDMETHODIMP COleServerDocEx::XDataObjectEx::SetData(
      LPFORMATETC lpFormatEtc, LPSTGMEDIUM lpStgMedium, BOOL fRelease)
   {
      METHOD_PROLOGUE(COleServerDocEx, DataObjectEx)
      ASSERT_VALID(pThis);

      return pThis->m_xDataObject.SetData(lpFormatEtc, lpStgMedium,
                                          fRelease);
   }

   STDMETHODIMP COleServerDocEx::XDataObjectEx::EnumFormatEtc(
      DWORD dwDirection, LPENUMFORMATETC FAR* ppenumFormatEtc)
   {
      METHOD_PROLOGUE(COleServerDocEx, DataObjectEx)
      ASSERT_VALID(pThis);

      return pThis->m_xDataObject.EnumFormatEtc(dwDirection,
                                                ppenumFormatEtc);
   }

   STDMETHODIMP COleServerDocEx::XDataObjectEx::DAdvise(
      FORMATETC FAR* pFormatetc, DWORD advf,
      LPADVISESINK pAdvSink, DWORD FAR* pdwConnection)
   {
      METHOD_PROLOGUE(COleServerDocEx, DataObjectEx)
      ASSERT_VALID(pThis);

      return pThis->m_xDataObject.DAdvise(pFormatetc, advf, pAdvSink,
                                          pdwConnection);
   }

   STDMETHODIMP COleServerDocEx::XDataObjectEx::DUnadvise(DWORD dwConn)
   {
      METHOD_PROLOGUE(COleServerDocEx, DataObjectEx)
      ASSERT_VALID(pThis);

      return pThis->m_xDataObject.DUnadvise(dwConn);
   }

   STDMETHODIMP COleServerDocEx::XDataObjectEx::EnumDAdvise(
      LPENUMSTATDATA FAR* ppenumAdvise)
   {
      METHOD_PROLOGUE(COleServerDocEx, DataObjectEx)
      ASSERT_VALID(pThis);

      return pThis->m_xDataObject.EnumDAdvise(ppenumAdvise);
   }

   //////////////////////////////////////////////////////////////// 
   // COleServerDocEx diagnostics

   #ifdef _DEBUG
   void COleServerDocEx::AssertValid() const
   {
      COleServerDoc::AssertValid();
   }

   void COleServerDocEx::Dump(CDumpContext& dc) const
   {
      COleServerDoc::Dump(dc);
      AFX_DUMP1(dc, "\nm_bDontSave = ", m_bDontSave);
   }
   #endif //_DEBUG

   // 
   // End of olesvrex.cpp
   ////////////////////////////////////////////////////////////////

Additional reference words: kbinf 1.50 2.00 2.10 2.50 2.51 2.52 3.00 3.10 4.00 4.10 KBCategory: kbprg KBSubcategory: MfcOLE

Keywords          : kbole kbMFC kbVC 
Version           : 1.50 1.51 1.52 | 2.00 2.10 4.00
Platform          : NT WINDOWS

Last Reviewed: October 11, 1997