title: CS_DROPSHADOW window style do not work
body: <p>I creating a child window with CS_DROPSHADOW style, but the shadow is not displayed.<br>
  I tried to call <code>SystemParametersInfo(SPI_SETDROPSHADOW, 0, (PVOID) TRUE, 0);</code> but it also not helpful.<br>
  Can someone explain to me what's wrong?</p>
  
  <pre><code>    WNDCLASSEX wcex;
  
      HBRUSH bgBrush = CreateSolidBrush(RGB(171,181,201));
  
      wcex.cbSize = sizeof(WNDCLASSEX);
      wcex.style          = CS_DBLCLKS;
      wcex.lpfnWndProc    = KolmusProc;
      wcex.cbClsExtra     = 0;
      wcex.cbWndExtra     = 0;
      wcex.hInstance      = hInstance;
      wcex.hIcon          = LoadIconW(hInstance, MAKEINTRESOURCE(IDI_APPLICATION));
      wcex.hCursor        = LoadCursor(NULL, IDC_ARROW);
      wcex.hbrBackground  = bgBrush;
      wcex.lpszMenuName   = NULL;
      wcex.lpszClassName  = L"Kolmus";
      wcex.hIconSm        = LoadIconW(hInstance, MAKEINTRESOURCE(IDI_APPLICATION));
  
      RegisterClassEx(&amp;wcex);
  
      wcex.style          = CS_DROPSHADOW;
      wcex.lpfnWndProc    = PageProc;
      wcex.hbrBackground  = (HBRUSH)(COLOR_WINDOW+1);
      wcex.lpszClassName  = L"Page";
  
      RegisterClassEx(&amp;wcex);
  
      HWND hWnd = CreateWindow(L"Kolmus", L"Kolmus", WS_OVERLAPPEDWINDOW | WS_VISIBLE,
          CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInstance, NULL); 
  
      HWND PageWnd = CreateWindow(L"Page", L"", WS_CHILD | WS_VISIBLE, 30, 30, 200, 200, hWnd, NULL, hInstance, NULL);
  
      MSG msg;
      while (GetMessage(&amp;msg, NULL, 0, 0))
      {
          TranslateMessage(&amp;msg); 
          DispatchMessage(&amp;msg);
      }
  
      return (int)msg.wParam;
  </code></pre>