Provide Link-Source Formats in Data Transfer

With the addition of the CFSTR_LINKSOURCE and CFSTR_LINKSRCDESCRIPTOR formats to Cosmo's data transfer objects, we enable containers to link to a Figure object. Cosmo registers these formats in the CCosmoDoc constructor and saves them in m_cfLinkSource and m_cfLinkSrcDescriptor. We add these formats to those stored in the transfer object in CCosmoDoc::TransferObjectCreate. This function calls CCosmoDoc::RenderMedium to render the data itself. As mentioned in Chapter 20, CFSTR_LINKSOURCE is a stream containing a serialized moniker; CFSTR_LINKSRCDESCRIPTOR is an OBJECTDESCRIPTOR structure:

BOOL CCosmoDoc::RenderMedium(UINT cf, LPSTGMEDIUM pSTM)
    {
    [Case for CF_EMBEDSOURCE]

    /*
     * CFSTR_OBJECTDESCRIPTOR and CFSTR_LINKSRCDESCRIPTOR are the
     * same formats, but copy link source only if we have a moniker.
     */
    if (cf==m_cfLinkSrcDescriptor && NULL==m_pMoniker)
        return FALSE;

    if (cf==m_cfObjectDescriptor œœ cf==m_cfLinkSrcDescriptor)
        {
        SIZEL   szl, szlT;
        POINTL  ptl;
        RECT    rc;
        LPTSTR  psz=NULL;

        m_pPL->SizeGet(&rc);
        SETSIZEL(szlT, rc.right, rc.bottom);
        XformSizeInPixelsToHimetric(NULL, &szlT, &szl);

        SETPOINTL(ptl, 0, 0);

        //Include moniker display name now if we have one.
        if (m_pMoniker)
            {
            LPBC    pbc;

            CreateBindCtx(0, &pbc);
            m_pMoniker->GetDisplayName(pbc, NULL, &psz);
            pbc->Release();
            }
        CoTaskMemFree((void *)psz);
        pSTM->hGlobal=INOLE_AllocObjectDescriptor
            (CLSID_CosmoFigure, DVASPECT_CONTENT, szl, ptl
            , OLEMISC_RECOMPOSEONRESIZE, PSZ(IDS_OBJECTDESCRIPTION)
            , psz);

        pSTM->tymed=TYMED_HGLOBAL;
        return (NULL!=pSTM->hGlobal);
        }

    if (cf==m_cfLinkSource)
        {
        if (NULL!=m_pMoniker)
            {
            FORMATETC   fe;
            HRESULT     hr;

            pSTM->tymed=TYMED_NULL;
            SETDefFormatEtc(fe, cf, TYMED_ISTREAM);
            hr=INOLE_GetLinkSourceData(m_pMoniker
                , (LPCLSID)&CLSID_CosmoFigure, &fe, pSTM);

            return SUCCEEDED(hr);
            }
        }

    return FALSE;
    }

We don't, of course, copy either link format if we have no moniker. If we have a moniker, we include the moniker's display name in CFSTR_LINKSRCDESCRIPTOR, using our helper function INOLE_AllocObjectDescriptor to create the data. To create CFSTR_LINKSOURCE, we use the helper function INOLE_GetLinkSourceData, which creates a stream in global memory, saves the moniker to the stream with OleSaveToStream, and saves the object's CLSID with a call to WriteClassStm.

As for the placement of the linking formats on the clipboard, they should always be after other formats, even after simple formats such as CF_TEXT. The reason is that linking almost never happens by default when a container pastes. It almost always happens when the user explicitly asks the container to perform a Paste Link operation. Keep the link data at the lowest spot on the totem pole.