Supporting Visual Styles in MFC Snap-ins

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To support visual themes in a snap-in built on the Microsoft Foundation Classes (MFC) framework, the snap-in must create and reference a manifest (as described in Supporting Visual Styles in Snap-ins), as well as provide code to theme property sheets and other UI elements. This section describes example code changes. For brevity, error-checking is minimized in the example code.

The following sections provide details.

Supporting visual styles in property sheets

During the creation of your property sheets, you will need to change your code to use the PROPSHEETPAGE_LATEST structure. For example, your snap-in's property pages may be created by code similar to the following.

HRESULT CExtendPropertySheet::CreatePropertyPages(
    LPPROPERTYSHEETCALLBACK pCallback,
    LONG_PTR handle,
    LPDATAOBJECT lpIDataObject )
{

    // m_MyPage derives from the MFC CPropertyPage class.
    HPROPSHEETPAGE hPage = ::CreatePropertySheetPage(&m_MyPage.m_psp);
    pCallback->AddPage(hPage);
    return S_OK;
}

The code should be modified to use the latest property sheet structure. For example, the following code example shows the use of a helper function, MyCreatePropertySheetPage, which is called from the modified implementation of CExtendPropertySheet::CreatePropertyPages.

HRESULT CExtendPropertySheet::CreatePropertyPages(
    LPPROPERTYSHEETCALLBACK pCallback,
    LONG_PTR handle,
    LPDATAOBJECT lpIDataObject )
{
    // m_MyPage derives from the MFC CPropertyPage class.
    HPROPSHEETPAGE hPage = MyCreatePropertySheetPage(&m_MyPage.m_psp);
    pCallback->AddPage(hPage);
    return S_OK;
}

#ifndef PROPSHEETPAGE_LATEST
    #ifdef UNICODE
        #define PROPSHEETPAGE_LATEST PROPSHEETPAGEW_LATEST
    #else
        #define PROPSHEETPAGE_LATEST PROPSHEETPAGEA_LATEST
    #endif
#endif
 
HPROPSHEETPAGE MyCreatePropertySheetPage(AFX_OLDPROPSHEETPAGE* ppsp)
{
    PROPSHEETPAGE_LATEST pspLatest = {0};
    CopyMemory (&pspLatest, ppsp, ppsp->dwSize);
    pspLatest.dwSize = sizeof(pspLatest);
 
    return (::CreatePropertySheetPage (&pspLatest));
}

Supporting visual styles in other UI elements

Before that displays other snap-in UI elements through calls to functions such as CreateWindow or DialogBox, set an activation context so that the UI element will support the active visual theme. A helper class can assist you in setting the activation context, and an instance of the helper class can be created when your CApp object is created. The following is an example of the implementation for the CAppFusionInit helper class (the class can be named to whatever you like). The helper class relies on CreateActCtx and ReleaseActCtx, which are activation context functions provided by Windows.

class CAppFusionInit{
   HANDLE  m_hActCtx;
   HMODULE m_hModule;
   int     m_resourceID;
public:
    CAppFusionInit(HMODULE hMod, int id) : m_hActCtx(INVALID_HANDLE_VALUE), m_hModule(hMod), m_resourceID(id)
       {InitializeFromModuleID(hMod,id);}
    ~CAppFusionInit()
       {FusionUninitialize();}

private:
    // The following is deliberately not implemented.
    CAppFusionInit(const CAppFusionInit&); 
    // The following is deliberately not implemented.
    void operator=(const CAppFusionInit&);
private:
    void InitializeFromModuleID(HMODULE hMod, int id)
    {
      TCHAR szPath[MAX_PATH];
      if (0 == GetModuleFileName(hMod, szPath, countof(szPath)))
          return;
      ACTCTX act = {0};
      act.dwFlags = ACTCTX_FLAG_RESOURCE_NAME_VALID;
      act.lpResourceName = MAKEINTRESOURCE(id);
      if (INVALID_HANDLE_VALUE == m_hActCtx)
      {
         act.cbSize = sizeof(act);
         act.lpSource = szPath;

#ifdef UNICODE
         m_hActCtx = CreateActCtxW(&act);
#else
         m_hActCtx = CreateActCtxA(&act);
#endif // !UNICODE
      }
    }
    void FusionUninitialize()
    {
      if (INVALID_HANDLE_VALUE != m_hActCtx)
      {
         ReleaseActCtx(m_hActCtx);
         m_hActCtx = INVALID_HANDLE_VALUE;
      }
    }
public:
     HANDLE GetThemeContextHandle()
    {
        return m_hActCtx;
    }
};

Implement a function in your CApp class to get the activation context handle.

HANDLE CMyApp::GetFusionInitHandle()
{
    if (m_pfusionInit)
       return m_pfusionInit->GetThemeContextHandle();
    return NULL;
}

Provide code to create an instance of the CAppFusionInit class in your implementation of CApp::InitInstance. The constant SXS_MANIFEST_RESOURCE_ID is the snap-in's identifier for the snap-in provided manifest.

m_pfusionInit = new CAppFusionInit(NULL,
  static_cast<int>(
    reinterpret_cast<ULONG_PTR>(SXS_MANIFEST_RESOURCE_ID)));

Provide code to delete the instance of the CAppFusionInit class in your implementation of CApp::ExitInstance.

if (m_pfusionInit)
    delete m_pfusionInit;

Create a helper class to manage the activation context. The helper class relies on ActivateActCtx and DeactivateActCtx, which are activation context functions provided by Windows.

class CThemeContextActivator {
public:
    CThemeContextActivator(HANDLE hActCtx) : m_ulActivationCookie(0)
        { ActivateActCtx(hActCtx, &amp;m_ulActivationCookie); }

    ~CThemeContextActivator()
     { 
       if (m_ulActivationCookie != 0)
          DeactivateActCtx(0, m_ulActivationCookie);
     }
private:
     ULONG_PTR m_ulActivationCookie;
};

Create an instance of the CThemeContextActivator class before calling any UI-creating functions, such as CreateWindow or DialogBox.

CThemeContextActivator activator(GetMyApp()->GetFusionInitHandle());
// Make the call to CreateWindow, DialogBox, and so on.
// ...