Автор: http://www.swissdelphicenter.ch

{
  Capturing a CLX form is easy, once you know.
  It took me a little time to find out, so I'm giving the knowledge to help others :
}

type
  TFormCapturable = class(TForm)
  public
    procedure PrintOne;
  end;

var
  FormCapturable: TFormCapturable;

implementation

uses
  Qt;

procedure TFormCapturable.PrintOne;
var
  aBitmap: TBitmap;
  aWinHandle: QWidgetH;
  aWinId: Cardinal;
  x, y, w, h: integer;
begin
  // create a new bitmap to hold the captured screen
  aBitMap := TBitmap.Create;
  try
    // get a handle on the desktop
    aWinHandle := QApplication_desktop;
    // get the Id from the desktop handle
    aWinId := QWidget_winId(aWinHandle);
    // get the position and size of the windows
    x := Self.Left;
    y := Self.Top;
    w := Self.Width;
    h := Self.Height;
    // capture the window into the bitmap's pixmap
    QPixmap_grabWindow(aBitmap.Handle, aWinId, x, y, w, h);
    // save the bitmap
    aBitMap.SaveToFile('c:\temp\test.bmp');
  finally
    // don't forget to kill the bitmap after use.
    FreeAndNil(aBitMap);
  end;
end;