procedure TForm1.Memo1MouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var
  ClientPoint, ScreenPoint: TPoint;
begin
  if Memo1.SelLength > 0 then
  begin
    ClientPoint.X := X;
    ClientPoint.Y := Y;
    ScreenPoint := ClientToScreen(ClientPoint);
    PopupMenu1.Popup(ScreenPoint.X, ScreenPoint.Y);
  end;
end;