Paint Dock Frame

procedure TDockTree.PaintDockFrame(Canvas: TCanvas; Control: TControl; const ARect: TRect);

  procedure DrawCloseButton(Left, Top: Integer);
  begin
    DrawFrameControl(Canvas.Handle, Rect(Left, Top, Left+FGrabberSize-2,
      Top+FGrabberSize-2), DFC_CAPTION, DFCS_CAPTIONCLOSE);
  end;

  procedure DrawGrabberLine(Left, Top, Right, Bottom: Integer);
  begin
    with Canvas do
    begin
      Pen.Color := clBtnHighlight;
      MoveTo(Right, Top);
      LineTo(Left, Top);
      LineTo(Left, Bottom);
      Pen.Color := clBtnShadow;
      LineTo(Right, Bottom);
      LineTo(Right, Top-1);
    end;
  end;

begin
  with ARect do
    if FDockSite.Align in [alTop, alBottom] then
    begin
      DrawCloseButton(Left+1, Top+1);
      DrawGrabberLine(Left+3, Top+FGrabberSize+1, Left+5, Bottom-2);
      DrawGrabberLine(Left+6, Top+FGrabberSize+1, Left+8, Bottom-2);
    end
    else
    begin
      DrawCloseButton(Right-FGrabberSize+1, Top+1);
      DrawGrabberLine(Left+2, Top+3, Right-FGrabberSize-2, Top+5);
      DrawGrabberLine(Left+2, Top+6, Right-FGrabberSize-2, Top+8);
    end;
end;