WM_PAINT:
  DC := WinApi.GetDC(0);
  HDC := WinApi.CreateCompatibleDC(DC);
  bmp := WinApi.CreateCompatibleBitmap(HDC, 100, 100);
  WinApi.SelectObject(HDC, bmp);
  WinApi.BitBlt(hDC, 0, 0, 100, 100, Comp, 0, 0, WinApi.SRCCOPY);
  WinApi.DeleteObject(bmp);
  WinApi.DeleteDC(HDC);
.........

hdc := WinApi.GetDC(wnd);
hdcMem := WinApi.CreateCompatibleDC(hdc);
hBitmap := WinApi.CreateCompatibleBitmap(hdc,100,100);
res := WinApi.SelectObject(hdcMem, hBitmap);
res := WinApi.BitBlt(hdc, 0, 300, 100, 100, hdcMem, 100, 100, WinApi.WHITENESS);
res := WinApi.MoveToEx(hdc,10,19,pt);
res := WinApi.LineTo(hdc,30,300);