title: window with transparent client area
body: <p>I register the window class like this:</p>
  
  <pre><code>WNDCLASSEX wctt;
  wctt.cbSize        = sizeof(WNDCLASSEX);
  wctt.style         = CS_DBLCLKS;
  wctt.lpfnWndProc   = WndProcTooltip;
  wctt.cbClsExtra    = 0;
  wctt.cbWndExtra    = 0;
  wctt.hInstance     = m_hAppInstance;
  wctt.hIcon         = NULL;
  wctt.hCursor       = LoadCursor(NULL, IDC_SIZE);
  wctt.hbrBackground = NULL;
  wctt.lpszMenuName  = NULL;
  wctt.lpszClassName = _T("myWindow");
  wctt.hIconSm       = NULL;
  RegisterClassEx(&amp;wctt)
  </code></pre>
  
  <p>As you can see I use <code>wctt.hbrBackground = NULL</code>; so it will have no background.</p>
  
  <p>The window is created like this:</p>
  
  <pre><code>::CreateWindowEx(WS_EX_TOPMOST | WS_EX_TOOLWINDOW,
  _T("myWindow"),
  NULL,
  WS_VISIBLE | WS_POPUP,
  50,
  50,
  150,
  100,
  NULL,
  NULL,
  m_hAppInstance,
  NULL);
  </code></pre>
  
  <p>In the paint section I draw icon on the window:</p>
  
  <pre><code>PAINTSTRUCT     ps;
  HDC             hdc;
  BITMAP          bitmap;
  ICONINFO        iconinfo;
  hdc = ::BeginPaint(hWnd, &amp;ps);
  ::SetBkMode(hdc,TRANSPARENT);
  ::GetIconInfo(localIcon, &amp;iconinfo);
  ::GetObject(iconinfo.hbmColor, sizeof(bitmap), &amp;bitmap);
  ::DeleteObject(iconinfo.hbmColor);
  ::DeleteObject(iconinfo.hbmMask);
  ::DrawIconEx(hdc, 0,0, localIcon, bitmap.bmWidth, bitmap.bmHeight, 0, NULL, DI_NORMAL);
  </code></pre>
  
  <p>The icon size is smaller than the window size and I get on the background the current view on the window below the popup.</p>
  
  <p>But now when I move the window (or minimize the window below the popup) the background is not changing.</p>
  
  <p>I was trying to make a timer that each time do the flowing:</p>
  
  <pre><code>RECT rcClient;
  GetClientRect(hWnd, &amp;rcClient);
  InvalidateRect(hWnd,&amp;rcClient,TRUE);
  </code></pre>
  
  <p>This makes the print function run again but the background of the icon is not changing.</p>
  
  <p>Should I do anything in <code>WM_ERASEBKGND</code>?<br>
  Does Anyone have any idea how to make it work?</p>
  
  <p>thanks,
  guy</p>