JPopupMenuをキー入力で開く場合の表示位置を調整する

class NewspaperStyleList<E extends ListItem> extends JList<E> {
  protected NewspaperStyleList(DefaultListModel<E> model) {
    super(model);
  }

  @Override public void updateUI() {
    setSelectionForeground(null);
    setSelectionBackground(null);
    setCellRenderer(null);
    super.updateUI();
    setLayoutOrientation(JList.HORIZONTAL_WRAP);
    getSelectionModel().setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
    setVisibleRowCount(0);
    setFixedCellWidth(64);
    setFixedCellHeight(64);
    setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
    setCellRenderer(new ListItemListCellRenderer<>());
  }

  @Override public Point getPopupLocation(MouseEvent event) {
    if (event == null) {
      int i = getLeadSelectionIndex();
      Rectangle r = getCellBounds(i, i);
      if (r != null) {
        return new Point((int) r.getCenterX(), (int) r.getCenterY());
      }
    }
    return super.getPopupLocation(event);
  }
}