procedure TForm1.HideTitlebar;
var
  Save: Longint;
begin
  if BorderStyle=bsNone then
    Exit;
  Save:=GetWindowLong(Handle, GWL_STYLE);
  if (Save and WS_CAPTION)=WS_CAPTION then
  begin
    case BorderStyle of
      bsSingle, bsSizeable:
        SetWindowLong(Handle, GWL_STYLE, Save and (not WS_CAPTION) or WS_BORDER);
      bsDialog:
        SetWindowLong(Handle, GWL_STYLE, Save and
        (not WS_CAPTION) or DS_MODALFRAME or WS_DLGFRAME);
    end;
    Height:=Height-GetSystemMetrics(SM_CYCAPTION);
    Refresh;
  end;
end;

procedure TForm1.ShowTitlebar;
var
  Save: Longint;
begin
  if BorderStyle=bsNone then
    Exit;
  Save:=GetWindowLong(Handle, GWL_STYLE);
  if (Save and WS_CAPTION)<>WS_CAPTION then
  begin
    case BorderStyle of
      bsSingle, bsSizeable:
        SetWindowLong(Handle, GWL_STYLE, Save or WS_CAPTION or WS_BORDER);
      bsDialog:
        SetWindowLong(Handle, GWL_STYLE, Save or WS_CAPTION or
        DS_MODALFRAME or WS_DLGFRAME);
    end;
    Height:=Height+getSystemMetrics(SM_CYCAPTION);
    Refresh;
  end;
end;