Swing/ClearSelection のバックアップ(No.17)

class ClearSelectionListener extends MouseInputAdapter {
  private boolean startOutside;

  private static <E> void clearSelectionAndFocus(JList<E> list) {
    list.clearSelection();
    list.getSelectionModel().setAnchorSelectionIndex(-1);
    list.getSelectionModel().setLeadSelectionIndex(-1);
  }

  private static <E> boolean contains(JList<E> list, Point pt) {
    for (int i = 0; i < list.getModel().getSize(); i++) {
      if (list.getCellBounds(i, i).contains(pt)) {
        return true;
      }
    }
    return false;
  }

  @Override public void mousePressed(MouseEvent e) {
    JList<?> list = (JList<?>) e.getComponent();
    startOutside = !contains(list, e.getPoint());
    if (startOutside) {
      clearSelectionAndFocus(list);
    }
  }

  @Override public void mouseReleased(MouseEvent e) {
    startOutside = false;
  }

  @Override public void mouseDragged(MouseEvent e) {
    JList<?> list = (JList<?>) e.getComponent();
    if (contains(list, e.getPoint())) {
      startOutside = false;
    } else if (startOutside) {
      clearSelectionAndFocus(list);
    }
  }
}