HOWTO: Display an MFC Automation Document Automatically

• The Microsoft Foundation Classes (MFC) included with:

      - Microsoft Visual C++ for Windows, versions 1.5, 1.51, 1.52
      - Microsoft Visual C++, 32-bit Edition, versions 2.0, 2.1, 2.2,
        4.0, 4.1, 4.2, 5.0
  

SUMMARY

Some OLE Automation servers, such as Microsoft Excel, automatically display a worksheet when it is created through OLE Automation. OLE Automation servers implemented in MFC do not display the document window by default when the document object is created through OLE Automation. This article explains how to add this behavior to a generic MFC OLE Automation server created using AppWizard.

MORE INFORMATION

The creation process for a document object created through OLE Automation slightly differs from the process involved when the server's File.New menu item is used. The document object is created using a class factory, which is represented by the application object's COleTemplateServer data member (m_server).

When a new document object is created through OLE Automation, COleTemplateServer::OnCreateObject() is called, which calls CDocTemplate::OpenDocumentFile with the last parameter set to FALSE to create an invisible document window. By replacing this call to CDocTemplate::OpenDocumentFile() with the last parameter set to TRUE, a visible document window will be created.

Additionally, the code in the application's InitInstance(), which checks if the server is running embedded or automated, should be removed. The main window of the application will not be displayed if this code isn't removed and the server isn't already running.

Step-by-Step Procedure

The following steps illustrate how to add this behavior to a generic MFC OLE Automation server created using AppWizard:

1. Using AppWizard, create an SDI or MDI application called MyApp with OLE Automation support.

2. Add the following class definition before the project's CWinApp-derived class's definition in the application object's header file (MyApp.h).

      // CMyTemplateServer used to override OnCreateObject.
      class CMyTemplateServer : public COleTemplateServer
      {
         // Constructors / Destructors
         public:
         CMyTemplateServer(){}
         virtual ~CMyTemplateServer(){}
   
         // Overrides
         virtual CCmdTarget* OnCreateObject();
      };
   
   

3. Add the following implementation of OnCreateObject() to the CWinApp- derived class's implementation file (MyApp.cpp).

      // Identical to COleTemplateServer::OnCreateObject() except for
      // the call to OpenDocumentFile() with the last parameter set to
      // TRUE instead of FALSE.
      CCmdTarget* CMyTemplateServer::OnCreateObject()
      {
         ASSERT_VALID(this);
         ASSERT_VALID(m_pDocTemplate);
   
         // Save application user control status
         BOOL bUserCtrl = AfxOleGetUserCtrl();
   
         // Create visible doc/view/frame set
         CDocument* pDoc;
         pDoc = m_pDocTemplate->OpenDocumentFile(NULL, TRUE);
   
         // Restore application's user control status
         AfxOleSetUserCtrl(bUserCtrl);
   
         if (pDoc != NULL)
         {
            ASSERT_VALID(pDoc);
            ASSERT_KINDOF(CDocument, pDoc);
   
            // All new documents created by OLE start out modified
            pDoc->SetModifiedFlag();
         }
         return pDoc;
      }
   
   

4. Change the CWinApp-derived object's m_server member from type COleTemplateServer to CMyTemplateServer. For example:

   class CMyApp : public CWinApp {

          public:
          CMyApp();
   

          // Overrides
          // ClassWizard generated virtual function overrides
          // {{AFX_VIRTUAL(CMyApp)
          public:
          virtual BOOL InitInstance();
          // }}AFX_VIRTUAL
   

          // Implementation
          CMyTemplateServer m_server; // <== change to derived class
          ...
          ...
       };
   

5. Modify the check for running embedded or automated from the application's InitInstance() member function. For example, modify the AppWizard provided code to match the following lines from InitInstance():

         // Check to see if launched as OLE server
         if (cmdInfo.m_bRunEmbedded || cmdInfo.m_bRunAutomated)
         {
            // Register all OLE server (factories) as running. This enables
            // the OLE libraries to create objects from other applications.
         COleTemplateServer::RegisterAll();
   
            // Application was run with /Embedding or /Automation. Don't
            // show the main window in this case.
            //      return TRUE;
         } else {
      
            // When a server application is launched stand-alone, it
            // is a good idea to update the system registry in case
            // it has been damaged.
          m_server.UpdateRegistry(OAT_DISPATCH_OBJECT);
          COleObjectFactory::UpdateRegistryAll();
          }
   
      NOTE: This code is specific to Visual C++ version 4.0; it varies with
      the earlier versions.
   
   

6. Compile the application, and run it stand-alone.

7. Create an OLE Automation client that creates an instance of your document type. Upon creation of the document object, the view should automatically be displayed.

Keywords          : MfcOLE
Technology        : kbMfc kbole
Version           : WINDOWS:1.50,1.51,1.52;Winnet:2.0,2.1,2.2,4.1,4.2,5.0
Platform          : NT WINDOWS
Issue type        : kbhowto