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Using screensavers inside the Windows Media Player

Sample Image - SheepWMP.jpg

Introduction

A few days ago, I downloaded and installed the electricsheep screensaver. This is such a cool screensaver, I wanted to watch it while I worked, and I found the SheepWatcher.

So I started thinking: "that's cool, how did they do that, run the screen saver in a window?" Good old Microsoft had the anwser.

So being a Windows developer, I decided I could do better, a Windows Media Player plug-in to run ElectricSheep.scr. The first step was to get the WMP SDK:

It did not work with VS.NET 2005:

Test

OK, create a C++ project for a Windows Media Player Visualization Plug-in, we will call it SheepWMP. Actually, I wrote a quick test dialog application like so:

A small helper function to wrap CreateProcess:

static HANDLE LaunchProcess ( LPTSTR aProcessName, LPTSTR aArgs )
{
    STARTUPINFO lStartupInfo;            
    PROCESS_INFORMATION lProcessInfo;

    memset ( &lProcessInfo, 0, sizeof ( lProcessInfo ) );
    memset ( &lStartupInfo, 0, sizeof ( lStartupInfo ) );

    lStartupInfo.cb = sizeof ( lStartupInfo );
    lStartupInfo.dwFlags = STARTF_USESHOWWINDOW;
    lStartupInfo.wShowWindow = SW_SHOWNORMAL;

    // Create target process
    CreateProcess ( aProcessName, aArgs, NULL, NULL, FALSE, 0, 
                    NULL, NULL, & lStartupInfo, & lProcessInfo );

    WaitForInputIdle ( lProcessInfo.hProcess, INFINITE ) ;

    return lProcessInfo.hProcess ;
}
BOOL CSheepTestDlg::OnInitDialog()
{
    CDialog::OnInitDialog();

    // Set the icon for this dialog.
    // The framework does this automatically
    //  when the application's main window is not a dialog
    SetIcon(m_hIcon, TRUE);   // Set big icon
    SetIcon(m_hIcon, FALSE);  // Set small icon

    TCHAR lCommand [ 1024 ] ;
    _stprintf_s ( lCommand, 1024, _T(" /p %u"), 
                  (DWORD) GetSafeHwnd () ) ;

    TCHAR lExe [ 1024 ] ;
    _stprintf_s ( lExe, 1024, 
       _T("c:\\windows\\system32\\electricsheep.scr") ) ;

    TRACE ( lCommand ) ;
    LaunchProcess ( lExe, lCommand ) ;
    return TRUE;  // return TRUE  unless you set the focus to a control
}

Code

Right, let's get to the Media Player plug-in. VS2005, with the WMPSDK, will create a basic visualization plug-in. The first steps are to remove all the rendering code and simply attach the screensaver to the desired HWND:

STDMETHODIMP CSheepWMP::RenderWindowed(TimedLevel *pLevels, 
                                       BOOL fRequiredRender )
{
....

    TCHAR lCommand [ 1024 ] ;
    _stprintf_s ( lCommand, 1024, _T(" /p %u"), 
                  (DWORD) m_hwndParent ) ;

    TCHAR lExe [ 1024 ] ;
    _stprintf_s ( lExe, 1024, 
                  _T("c:\\windows\\system32\\electricsheep.scr") ) ;

    TRACE ( lCommand ) ;
    LaunchProcess ( lExe, lCommand ) ;
....
}

But what happens when Windows Media Player changes size:

// Has the window changed dimensions
RECT lRect ;
GetClientRect ( gWnd, &lRect ) ;
if ( memcmp ( &gRect, &lRect, sizeof ( RECT ) ) != 0 )
{
    ATLTRACE ( DEFAULT_TRACE_PREFIX 
               _T("Window size changed...\n") ) ;
    memcpy ( &gRect, &lRect, sizeof ( RECT ) ) ;

    // Try to update the exinsing window
    HWND lWnd = FindWindowEx ( gWnd, NULL, 
                _T("WindowsScreenSaverClass"), NULL ) ;
    if ( lWnd ) 
    {
        ATLTRACE ( DEFAULT_TRACE_PREFIX 
                   _T("Moving screensaver window...\n") ) ;
        SetWindowPos ( lWnd, NULL, lRect . left, lRect . top, 
                       lRect . right - lRect . left, 
                       lRect . bottom - lRect . top, 
                       SWP_SHOWWINDOW ) ;
    }
}

So now, we have the basics working. If you examine my source, you will see that it locates all the Windows screensavers and can run them all inside the Window Media Player. It's done like so:

CAtlString lPath ;
SHGetFolderPath ( NULL, CSIDL_SYSTEM, NULL, 0, 
                  lPath . GetBufferSetLength ( MAX_PATH ) ) ;
lPath . ReleaseBuffer () ;

ATLTRACE ( DEFAULT_TRACE_PREFIX _T("Finding all scrs in %s\n"), lPath ) ;


CAtlString lSearch = lPath ;
PathAppend ( lSearch . GetBufferSetLength ( MAX_PATH ), DEFAULT_SCR_EXT ) ;
lSearch . ReleaseBuffer () ;

WIN32_FIND_DATA lFindFileData;
HANDLE lFind = FindFirstFile ( lSearch, &lFindFileData ) ;
if ( lFind != INVALID_HANDLE_VALUE )
{
    do
    {
        CAtlString lScr = lPath ;
        PathAppend ( lScr .GetBufferSetLength ( MAX_PATH ), 
                           lFindFileData . cFileName  ) ;
        lScr . ReleaseBuffer () ;
    
        ATLTRACE ( DEFAULT_TRACE_PREFIX _T("Adding scr, %s\n"), lScr ) ;

        m_Scrs . push_back ( lScr ) ;
    }
    while ( FindNextFile ( lFind, &lFindFileData ) ) ;

    FindClose ( lFind ) ;
}

Now, inside the Windows Media Player, we list all the screensavers using nice names. You have to get the names from the screensaver .scr files, which can be loaded like resource DLLs:

CAtlString CSheepWMP::GetScrName ( CAtlString aScr ) 
{
    // Initially get the filename and remove extension
    CAtlString lName = PathFindFileName ( aScr ) ;
    PathRemoveExtension ( lName . GetBufferSetLength ( MAX_PATH ) ) ;
    lName . ReleaseBuffer () ;

    // Load the DLL as a data file, and do not resolve any references
    ATLTRACE ( DEFAULT_TRACE_PREFIX _T("Loading library %s\n"), aScr ) ;
    HINSTANCE lInstance = LoadLibraryEx ( aScr, NULL, 
              DONT_RESOLVE_DLL_REFERENCES | LOAD_LIBRARY_AS_DATAFILE ) ;
    if ( lInstance )
    {
        // Examining all SCR, string 1 is the description
        // used by the display properties
        CAtlString lDesc ;
        LoadString ( lInstance, 1, 
                     lDesc.GetBufferSetLength(MAX_PATH), MAX_PATH ) ;
        lDesc . ReleaseBuffer () ;

        // Clean up
        FreeLibrary ( lInstance ) ;

        // If we have a valid description use it
        if ( lDesc . IsEmpty () == FALSE )
        {
            ATLTRACE ( DEFAULT_TRACE_PREFIX 
                       _T("Set scr name to description, %s\n"), lDesc ) ;
            lName = lDesc ;
        }
    }
    return lName ;
}

That's all!

History

  • 15 July, 2011: Updated source for new version of Electric Sheep. Also included the C# .NET implementation and the Microsoft Windows setup script.

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