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"Alex Sarafian" <demelene_gr@yahoo.gr> wrote in message
news:409a0030$1@newsgroups.borland.com...

> Since the handle of the parent window is passed in every dll instance,

No, it is not.  It is only set for the instance of the DLL that is loaded
into the application that is actually calling setHook().  Which means only
the instances attached to your own application will have a valid HWND handle
available.  No other DLL instance will have their HWND handle set, unless
you put the HWND into shared memory like I explained to you earlier.

> I read about CreateFileMapping and MapViewOfFile but I'm
> having some trouble, so if you can help?
> Where is the file mapping must be created??

Create and destroy it in your DLLEntryPoint() function, so that the memory
is always available as soon as the DLL is loaded.

    typedef struct
    {
        HWND hWnd;
        HHOOK hHook;
    }  TMyHookInfo, *PMyHookInfo;

    HANDLE hMapping = NULL;
    PMyHookInfo pHookInfo = NULL;

    HINSTANCE hInst = NULL;
    UINT UWM_MOUSEMOVE = 0;

    bool CreateSharedHookInfo()
    {
        hMapping = CreateFileMapping(INVALID_HANDLE_VALUE, NULL,
PAGE_READWRITE, 0, sizeof(TMyHookInfo), "MySharedHookInfo");
        if( hMapping == NULL )
            return false;

        bool bIsNewMapping = (GetLastError() != ERROR_ALREADY_EXISTS);

        pHookInfo = (PMyHookInfo) MapViewOfFile(hMapping, FILE_MAP_WRITE, 0,
0, 0);
        if( pHookInfo == NULL )
        {
            CloseHandle(hMapping);
            hMapping = NULL;
            return false;
        }

        if( bIsNewMapping )
        {
            pHookInfo->hWnd = NULL;
            pHookInfo->hHook = NULL;
        }

        return true;
    }

                }
                return FALSE;

    #pragma argsused
    int WINAPI DllEntryPoint(HINSTANCE hinst, unsigned long reason, void*
lpReserved)
    {
        switch( reason )
        {
            case DLL_PROCESS_ATTACH:
                hInst = hinst;

                UWM_MOUSEMOVE = RegisterWindowMessage(UWM_MOUSEMOVE_MSG);
                if( UWM_MOUSEMOVE == 0 )
                    return FALSE;

                if( !CreateSharedHookInfo() )
                    return FALSE;

                break;

            case DLL_PROCESS_DETACH:
                if( pHookInfo != NULL ) UnmapViewOfFile(pHookInfo);
                if( hMapping != NULL ) CloseHandle(hMapping);
                break;
        }

        return TRUE;
    }

    extern "C" __EXPORT_TYPE BOOL __stdcall setMyHook(HWND hWnd)
    {
        if( (pHookInfo) && (pHookInfo->hHook == NULL) )
        {
            pHookInfo->hHook = SetWindowsHookEx(WH_MOUSE,
(HOOKPROC)MessageHook, hInst, 0);
            if( pHookInfo->hHook != NULL )
            {
                pHookInfo->hWnd = hWnd;
                return TRUE;
            }
        }
        return FALSE;
    }

    extern "C" __EXPORT_TYPE BOOL __stdcall clearMyHook(HWND hWnd)
    {
        if( (pHookInfo) && ((pHookInfo->hWnd == hWnd) || (hWnd == NULL)) )
        {
            if( UnhookWindowsHookEx(pHookInfo->hHook) )
            {
                pInfo->hWnd = NULL;
                pInfo->hHook = NULL;
                return TRUE;
            }
        }
        return FALSE;
    }

    extern "C" LRESULT CALLBACK MessageHook(int nCode, WPARAM wParam, LPARAM
lParam)
    {
        if( pHookInfo )
        {
            if( nCode >= 0 )
                PostMessage(pHookInfo->hWnd, UWM_MOUSEMOVE, 0, 0);

            return CallNextHookEx(pHookInfo->hHook, nCode, wParam, lParam);
        }
        return 0;
    }


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