JToolTipにJTextAreaを配置して自動的に行折返しする

class LineWrapToolTip extends JToolTip {
  private final JTextArea textArea = new JTextArea(0, 20);
  private final JLabel label = new JLabel(" ");

  protected LineWrapToolTip() {
    super();
    textArea.setLineWrap(true);
    textArea.setWrapStyleWord(true);
    // textArea.setColumns(20);
    textArea.setOpaque(true);
    LookAndFeel.installColorsAndFont(
        textArea, "ToolTip.background", "ToolTip.foreground", "ToolTip.font");
    setLayout(new BorderLayout());
    add(textArea);
  }

  @Override public final void setLayout(LayoutManager mgr) {
    super.setLayout(mgr);
  }

  @Override public final Component add(Component comp) {
    return super.add(comp);
  }

  @Override public Dimension getPreferredSize() {
    // return getLayout().preferredLayoutSize(this);
    Dimension d = getLayout().preferredLayoutSize(this);
    label.setText(textArea.getText());
    // @see BasicTextUI.java
    // margin required to show caret in the rightmost position
    int caretMargin = -1;
    Object property = UIManager.get("Caret.width");
    if (property instanceof Number) {
      caretMargin = ((Number) property).intValue();
    }
    property = textArea.getClientProperty("caretWidth");
    if (property instanceof Number) {
      caretMargin = ((Number) property).intValue();
    }
    if (caretMargin < 0) {
      caretMargin = 1;
    }
    Insets i = getInsets();
    Insets ti = textArea.getInsets();
    int pad = i.left + i.right + ti.left + ti.right + caretMargin;
    // Insets tm = textArea.getMargin();
    // int pad = i.left + i.right + ti.left + ti.right + tm.left + tm.right;
    d.width = Math.min(d.width, label.getPreferredSize().width + pad);
    return d;
  }

  @Override public void setTipText(String tipText) {
    String oldValue = textArea.getText();
    if (!Objects.equals(oldValue, tipText)) {
      textArea.setText(tipText);
      firePropertyChange("tiptext", oldValue, tipText);
      revalidate();
      repaint();
    }
  }

  @Override public String getTipText() {
    return Optional.ofNullable(textArea).map(JTextArea::getText).orElse(null);
  }
}