How to Use OLE in Rich Edit Controls

This section contains information about using object linking and embedding (OLE) in rich edit controls.

What You Need to Know

Technologies

• Windows Controls

Prerequisites

• C/C++
• Windows User Interface Programming

Instructions

Use a Rich Edit Interface

Rich edit controls expose some of their functionality through Component Object Model (COM) interfaces. By obtaining an interface from a control, you gain the ability to work with other objects within the control. You can obtain this interface by sending theEM_GETOLEINTERFACEmessage. From theIRichEditOleinterface, you can then obtain interfaces used in theText Object Model.

Another interface,IRichEditOleCallback, is implemented by applications to define the behavior of the control when it interacts with objects.

Insert an Object into a Rich Edit Control

The following code example inserts a file object into a rich edit control. If a program is associated with the file type on the user's machine (for example, Microsoft Excel for an .xls file), the contents of the file display in the control; otherwise, an icon appears.

1. Get theIRichEditOleinterface.

   BOOL InsertObject(HWND hRichEdit, LPCTSTR pszFileName)
   {
       HRESULT hr;
   
       LPRICHEDITOLE pRichEditOle;
       SendMessage(hRichEdit, EM_GETOLEINTERFACE, 0, (LPARAM)&pRichEditOle);
       
       ...
   
   

2. Create structured storage.

       LPLOCKBYTES pLockBytes = NULL;
       hr = CreateILockBytesOnHGlobal(NULL, TRUE, &pLockBytes);
       
       LPSTORAGE pStorage;
       hr = StgCreateDocfileOnILockBytes(pLockBytes, 
                                         STGM_SHARE_EXCLUSIVE | STGM_CREATE | STGM_READWRITE, 
                                         0, &pStorage);
       ...
   
   

3. Set up the data format.

       FORMATETC formatEtc;
       
       formatEtc.cfFormat = 0;
       formatEtc.ptd      = NULL;
       formatEtc.dwAspect = DVASPECT_CONTENT;
       formatEtc.lindex   = -1;
       formatEtc.tymed    = TYMED_NULL;
       
       ...
   
   

4. Get a pointer to the display site.

       LPOLECLIENTSITE	pClientSite;
       hr = pRichEditOle->GetClientSite(&pClientSite);
       
       ...
   
   

5. Create the object and retrieve itsIUnknowninterface.

       LPUNKNOWN pUnk;
       CLSID clsid = CLSID_NULL;
       
       hr = OleCreateFromFile(clsid, 
                              pszFileName, 
                              IID_IUnknown, 
                              OLERENDER_DRAW, 
                              &formatEtc, 
                              pClientSite, 
                              pStorage, 
                              (void**)&pUnk);
       
       pClientSite->Release();
                 
       ...
   
   

6. Get the IOleObject interface to the object.

       LPOLEOBJECT pObject;
       
       hr = pUnk->QueryInterface(IID_IOleObject, (void**)&pObject);
       
       pUnk->Release();
   
       ...
   
   

7. To ensure that references are counted correctly, notify the object that it is contained.

       OleSetContainedObject(pObject, TRUE);
   
       ...
   
   

8. Set up object info.

       REOBJECT reobject = { sizeof(REOBJECT)};
       
       hr = pObject->GetUserClassID(&clsid);
       
       reobject.clsid    = clsid;
       reobject.cp       = REO_CP_SELECTION;
       reobject.dvaspect = DVASPECT_CONTENT;
       reobject.dwFlags  = REO_RESIZABLE | REO_BELOWBASELINE;
       reobject.dwUser   = 0;
       reobject.poleobj  = pObject;
       reobject.polesite = pClientSite;
       reobject.pstg     = pStorage;
       
       SIZEL sizel       = { 0 };
       reobject.sizel    = sizel;
   
       ...
   
   

9. Move the caret to the end of the text and add a carriage return.

       SendMessage(hRichEdit, EM_SETSEL, 0, -1);
       
       DWORD dwStart, dwEnd;
       
       SendMessage(hRichEdit, EM_GETSEL, (WPARAM)&dwStart, (LPARAM)&dwEnd);
       SendMessage(hRichEdit, EM_SETSEL, dwEnd+1, dwEnd+1);
       SendMessage(hRichEdit, EM_REPLACESEL, TRUE, (WPARAM)L"/n"); 
   
       ...
   
   

10. Insert the object.

        hr = pRichEditOle->InsertObject(&reobject);
    
        ...
    
    

11. Clean up.

        pObject->Release();
        
        pRichEditOle->Release();
    
        return TRUE;
        
    }
    
    

Using IRichEditOleCallback

Applications implement theIRichEditOleCallbackinterface to respond to OLE-related queries or actions that are performed by a rich edit control. You associate your implementation of the interface with the control by sending anEM_SETOLECALLBACKmessage. The control then calls methods on your implementation of the interface as appropriate.

For example,QueryAcceptDatais called when the user attempts to drag or paste an object into the control. If your application can accept the data, your implementation of the method returns S_OK; otherwise, it returns an error code. The method might also take some other action, such as warning the user that files of that type cannot be placed in the control.

Complete InsertObject Example Function

The following code example demonstrates the previous code snippets combined into one complete function that includes error handling.

BOOL InsertObject(HWND hRichEdit, LPCTSTR pszFileName)
{
    HRESULT hr;

    LPRICHEDITOLE pRichEditOle;
    SendMessage(hRichEdit, EM_GETOLEINTERFACE, 0, (LPARAM)&pRichEditOle);

    if (pRichEditOle == NULL)
    {
        return FALSE;
    }

    LPLOCKBYTES pLockBytes = NULL;
    hr = CreateILockBytesOnHGlobal(NULL, TRUE, &pLockBytes);

    if (FAILED(hr))
    {
        return FALSE;
    }

    LPSTORAGE pStorage;
    hr = StgCreateDocfileOnILockBytes(pLockBytes, 
           STGM_SHARE_EXCLUSIVE | STGM_CREATE | STGM_READWRITE, 
           0, &pStorage);

    if (FAILED(hr))
    {
        return FALSE;
    }

    FORMATETC formatEtc;
    formatEtc.cfFormat = 0;
    formatEtc.ptd = NULL;
    formatEtc.dwAspect = DVASPECT_CONTENT;
    formatEtc.lindex = -1;
    formatEtc.tymed = TYMED_NULL;

    LPOLECLIENTSITE	pClientSite;
    hr = pRichEditOle->GetClientSite(&pClientSite);

    if (FAILED(hr))
    {
        return FALSE;
    }

    LPUNKNOWN pUnk;
    CLSID clsid = CLSID_NULL;

    hr = OleCreateFromFile(clsid, pszFileName, IID_IUnknown, OLERENDER_DRAW, 
           &formatEtc, pClientSite, pStorage, (void**)&pUnk);

    pClientSite->Release();

    if (FAILED(hr))
    {
        return FALSE;
    }

    LPOLEOBJECT pObject;
    hr = pUnk->QueryInterface(IID_IOleObject, (void**)&pObject);
    pUnk->Release();

    if (FAILED(hr))
    {
        return FALSE;
    }

    OleSetContainedObject(pObject, TRUE);
    REOBJECT reobject = { sizeof(REOBJECT)};
    hr = pObject->GetUserClassID(&clsid);

    if (FAILED(hr))
    {
        pObject->Release();
        return FALSE;
    }

    reobject.clsid = clsid;
    reobject.cp = REO_CP_SELECTION;
    reobject.dvaspect = DVASPECT_CONTENT;
    reobject.dwFlags = REO_RESIZABLE | REO_BELOWBASELINE;
    reobject.dwUser = 0;
    reobject.poleobj = pObject;
    reobject.polesite = pClientSite;
    reobject.pstg = pStorage;
    SIZEL sizel = { 0 };
    reobject.sizel = sizel;

    SendMessage(hRichEdit, EM_SETSEL, 0, -1);
    DWORD dwStart, dwEnd;
    SendMessage(hRichEdit, EM_GETSEL, (WPARAM)&dwStart, (LPARAM)&dwEnd);
    SendMessage(hRichEdit, EM_SETSEL, dwEnd+1, dwEnd+1);
    SendMessage(hRichEdit, EM_REPLACESEL, TRUE, (WPARAM)L"/n"); 

    hr = pRichEditOle->InsertObject(&reobject);
    pObject->Release();
    pRichEditOle->Release();

    if (FAILED(hr))
    {
        return FALSE;
    }
    
    return TRUE;
}