Swing/DisableComboPopupByVerifier のバックアップ(No.1)

class BasicComboPopup2 extends BasicComboPopup {
  private transient MouseListener handler2;

  @Override public void uninstallingUI() {
    super.uninstallingUI();
    handler2 = null;
  }

  // Java 9: protected BasicComboPopup2(JComboBox<Object> combo) {
  protected BasicComboPopup2(JComboBox<?> combo) {
    super(combo);
  }

  @Override protected MouseListener createMouseListener() {
    if (Objects.isNull(handler2)) {
      handler2 = new Handler2();
    }
    return handler2;
  }

  private class Handler2 extends MouseAdapter {
    @Override public void mousePressed(MouseEvent e) {
      if (!SwingUtilities.isLeftMouseButton(e) || !comboBox.isEnabled()) {
        return;
      }
      boolean hasFocus = true;
      if (comboBox.isEditable()) {
        Component comp = comboBox.getEditor().getEditorComponent();
        if (!(comp instanceof JComponent) || ((JComponent) comp).isRequestFocusEnabled()) {
          hasFocus = comp.hasFocus() || comp.requestFocusInWindow();
        }
      } else if (comboBox.isRequestFocusEnabled()) {
        hasFocus = comboBox.hasFocus() || comboBox.requestFocusInWindow();
      }
      Component c = e.getComponent();
      if (!hasFocus && c instanceof AbstractButton) {
        ((AbstractButton) c).getModel().setPressed(false);
      }
      if (hasFocus) {
        togglePopup();
      }
    }

    @Override public void mouseReleased(MouseEvent e) {
      Component source = (Component) e.getSource();
      Dimension size = source.getSize();
      Rectangle bounds = new Rectangle(0, 0, size.width - 1, size.height - 1);
      if (!bounds.contains(e.getPoint())) {
        MouseEvent newEvent = SwingUtilities.convertMouseEvent(e.getComponent(), e, list);
        Point location = newEvent.getPoint();
        Rectangle r = new Rectangle();
        list.computeVisibleRect(r);
        if (r.contains(location)) {
          if (comboBox.getSelectedIndex() == list.getSelectedIndex()) {
            comboBox.getEditor().setItem(list.getSelectedValue());
          }
          comboBox.setSelectedIndex(list.getSelectedIndex());
        }
        comboBox.setPopupVisible(false);
      }
      hasEntered = false;
      stopAutoScrolling();
    }
  }
}