Using IDispEventImpl

When using IDispEventImpl to handle events, you will need to:

• Derive your class from IDispEventImpl.

• Add an event sink map to your class.

• Add entries to the event sink map using the SINK_ENTRY or SINK_ENTRY_EX macro.

• Implement the methods that you're interested in handling.

• Advise and unadvise the event source.

Example

The example below shows how to handle the DocumentChange event fired by Word's Application object. This event is defined as a method on the ApplicationEvents dispinterface.

The example is from the ATLEventHandling sample.

[ uuid(000209F7-0000-0000-C000-000000000046), hidden ]
dispinterface ApplicationEvents {
properties:
methods:
    [id(0x00000001), restricted, hidden]
    void Startup();

    [id(0x00000002)]
    void Quit();

    [id(0x00000003)]
    void DocumentChange();
};

The example uses #import to generate the required header files from Word's type library. If you want to use this example with other versions of Word, you must specify the correct mso dll file. For example, Office 2000 provides mso9.dll and OfficeXP provides mso.dll. This code is simplified from pch.h (stdafx.h in Visual Studio 2017 and earlier):

#pragma warning (disable : 4146)

// Paths to required MS OFFICE files (replace "MSO.DLL" and "MSWORD.OLB" with the actual paths to those files...)
#define _MSDLL_PATH "MSO.DLL"
// Delete the *.tlh files when changing import qualifiers
#import _MSDLL_PATH rename("RGB", "MSRGB") rename("DocumentProperties", "WordDocumentProperties") raw_interfaces_only

#import "C:\Program Files\Common Files\Microsoft Shared\VBA\VBA6\VBE6EXT.OLB" raw_interfaces_only

#define _MSWORDOLB_PATH "MSWORD.OLB"
#import _MSWORDOLB_PATH rename("ExitWindows", "WordExitWindows") rename("FindText", "WordFindText") raw_interfaces_only

#pragma warning (default : 4146)

The following code appears in NotSoSimple.h. The relevant code is noted by comments:

// Note #import doesn't generate a LIBID (because we don't use 'named_guids')
// so we have to do it manually
namespace Word
{
   struct __declspec(uuid("00020905-0000-0000-C000-000000000046"))
      /* library */ Library;
};

class ATL_NO_VTABLE CNotSoSimple : 
   public CComObjectRootEx<CComSingleThreadModel>,
   public CComCoClass<CNotSoSimple, &CLSID_NotSoSimple>,
   public IDispatchImpl<ISwitch, &IID_ISwitch, &LIBID_ATLEVENTHANDLINGLib>,
   // Note inheritance from IDispEventImpl
   public IDispEventImpl</*nID*/ 1, CNotSoSimple,
            &__uuidof(Word::ApplicationEvents2),
            &__uuidof(Word::Library), /*wMajor*/ 8, /*wMinor*/ 1>

{
public:
   CNotSoSimple()
   {
   }

DECLARE_REGISTRY_RESOURCEID(IDR_NOTSOSIMPLE)

DECLARE_PROTECT_FINAL_CONSTRUCT()

BEGIN_COM_MAP(CNotSoSimple)
   COM_INTERFACE_ENTRY(ISwitch)
   COM_INTERFACE_ENTRY(IDispatch)
END_COM_MAP()

   CComPtr<Word::_Application> m_pApp;

   // Event handlers
   // Note the __stdcall calling convention and 
   // dispinterface-style signature   
   void __stdcall OnQuit()
   {
      Stop();
   }

   void __stdcall OnDocChange()
   {
     ATLASSERT(m_pApp != NULL);

      // Get a pointer to the _Document interface on the active document
      CComPtr<Word::_Document> pDoc;
      m_pApp->get_ActiveDocument(&pDoc);

      // Get the name from the active document
      CComBSTR bstrName;
      if (pDoc)
        pDoc->get_Name(&bstrName);

      // Create a display string
      CComBSTR bstrDisplay(_T("New document title:\n"));
      bstrDisplay += bstrName;

      // Display the name to the user
      USES_CONVERSION;
      MessageBox(NULL, W2CT(bstrDisplay), _T("IDispEventImpl : Active Document Changed"), MB_OK);
   }

// Note the mapping from Word events to our event handler functions.
BEGIN_SINK_MAP(CNotSoSimple)
   SINK_ENTRY_EX(/*nID =*/ 1, __uuidof(Word::ApplicationEvents2), /*dispid =*/ 3, OnDocChange)
   SINK_ENTRY_EX(/*nID =*/ 1, __uuidof(Word::ApplicationEvents2), /*dispid =*/ 2, OnQuit)
END_SINK_MAP()

// ISwitch
public:

   STDMETHOD(Start)()
   {
      // If we already have an object, just return
      if (m_pApp)
         return S_OK;

      // Create an instance of Word's Application object
      HRESULT hr = m_pApp.CoCreateInstance(__uuidof(Word::Application), NULL, CLSCTX_SERVER);
     if (FAILED(hr))
        return hr;

     ATLASSERT(m_pApp != NULL);

      // Make the Word user interface visible
      m_pApp->put_Visible(true);

      // Note call to advise
      // Forge a connection to enable us to receive events
      DispEventAdvise(m_pApp);

      return S_OK;
   }

   STDMETHOD(Stop)()
   {
      // Check we have an object to unadvise on
      if (!m_pApp)
         return S_OK;

      // Note call to unadvise
      // Break the connection with the event source
      DispEventUnadvise(m_pApp);

      // Release the Word application
      m_pApp.Release();

      return S_OK;
   }
};

See also

Event Handling
ATLEventHandling Sample