...make a window borderless while dragging?

procedure TForm1.PanelTopMouseDown(Sender: TObject;
  Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
const
  SC_DRAGMOVE = $F012;
begin
  if (Button = mbLeft) then
  begin
    ReleaseCapture;
    (Self as TControl).Perform(WM_SYSCOMMAND, SC_DRAGMOVE, 0);
  end;
end;