JTextAreaとJFrameで幅固定、文字列の折り返し、親枠外まで高さ拡大可能なセルエディタを作成する

// private final Container glassPane = new EditorGlassPane();
// private final JPopupMenu popup = new JPopupMenu();
private final JFrame window = new JFrame();
// private final JTextField editor = new JTextField();
private final JTextArea editor = new JTextArea();
// ...
window.setUndecorated(true);
window.setAlwaysOnTop(true);
window.addWindowListener(new WindowAdapter() {
  @Override public void windowDeactivated(WindowEvent e) {
    if (editor.isEditable()) {
      renameTitle.actionPerformed(new ActionEvent(editor, ActionEvent.ACTION_PERFORMED, ""));
    }
  }
});
window.add(editor);
editor.setBorder(BorderFactory.createLineBorder(Color.BLACK));
editor.setLineWrap(true);
editor.setFont(UIManager.getFont("TextField.font"));
editor.setComponentPopupMenu(new TextComponentPopupMenu());
editor.getDocument().addDocumentListener(new DocumentListener() {
  private int prev = -1;
  private void update() {
    EventQueue.invokeLater(() -> {
      int h = editor.getPreferredSize().height;
      if (prev != h) {
        Rectangle rect = editor.getBounds();
        rect.height = h;
        editor.setBounds(rect);
        window.pack(); // popup.pack();
        editor.requestFocusInWindow();
      }
      prev = h;
    });
  }

  @Override public void insertUpdate(DocumentEvent e) {
    update();
  }

  @Override public void removeUpdate(DocumentEvent e) {
    update();
  }

  @Override public void changedUpdate(DocumentEvent e) {
    update();
  }
});