单实例

#pragma once

#define UM_ACTIVATE (WM_USER + 0x2001)
#define SINGLE_STRING (TEXT( "0x13cc6a4e, 0x2e3a, 0x46fa, 0x9d, 0x60, 0x43, 0x85, 0x71, 0x64, 0xd0, 0x28" ))

class CSingleSign
{
    HANDLE m_hMutex;
public:
    CSingleSign()
    {
        HWND hWndPrevious;

        m_hMutex = ::CreateMutex( NULL, FALSE, SINGLE_STRING );
        if ( GetLastError() == ERROR_ALREADY_EXISTS )
        {
            hWndPrevious = ::GetWindow( ::GetDesktopWindow(), GW_CHILD );
            while ( ::IsWindow( hWndPrevious ) )
            {
                if ( ::GetProp( hWndPrevious, SINGLE_STRING ) )
                {
                    ::PostMessage( hWndPrevious, UM_ACTIVATE, ( WPARAM )0, ( LPARAM )0 );
                    break;
                }

                hWndPrevious = ::GetWindow( hWndPrevious, GW_HWNDNEXT );
            }

            exit( 0 );
        }

        if ( m_hMutex == NULL )
        {
            exit( 0 );
        }
    }

    ~CSingleSign()
    {
        ::CloseHandle( m_hMutex );
    }
};


template <typename T>
class ATL_NO_VTABLE CSingleApp
{
    static CSingleSign _m_SingleSign;
public:
    CSingleApp(){_m_SingleSign;}

    BEGIN_MSG_MAP( CSingleApp<T> )
        MESSAGE_HANDLER( WM_CREATE, OnInitializeIt )
        MESSAGE_HANDLER( WM_INITDIALOG, OnInitializeIt )
        MESSAGE_HANDLER( WM_DESTROY, OnDestroy )
        MESSAGE_HANDLER( UM_ACTIVATE, OnActive )
    END_MSG_MAP()

    
    LRESULT OnInitializeIt( UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled )
    {
        LRESULT lRet;
        T* pT = static_cast<T*>( this );

        lRet = pT->InitializeIt( uMsg, wParam, lParam, bHandled );

        ::SetProp( pT->m_hWnd, SINGLE_STRING, ( HANDLE )1 );

        return lRet;
    }

    LRESULT OnDestroy( UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled )
    {
        T* pT = static_cast<T*>( this );

        ::RemoveProp( pT->m_hWnd, SINGLE_STRING );

        return pT->DestroyIt( uMsg, wParam, lParam, bHandled );
    }


    LRESULT OnActive( UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL& bHandled )
    {
        T* pT = static_cast<T*>( this );

        if ( pT->IsIconic() )
        {
            pT->ShowWindow( SW_RESTORE );
        }
        else
        {
            if ( !pT->IsWindowVisible() )
            {
                pT->ShowWindow( SW_SHOW );
                ::BringWindowToTop( pT->m_hWnd );
            }

            ::SetForegroundWindow( pT->m_hWnd );
        }

        bHandled = TRUE;
        return 0;
    }
};


template<typename T>
CSingleSign CSingleApp<T>::_m_SingleSign;