JInternalFrameのタイトル文字列幅を取得し、その値でJDesktopIconの幅を調整する

JDesktopPane desktop = new JDesktopPane();
desktop.setDesktopManager(new DefaultDesktopManager() {
  @Override public void iconifyFrame(JInternalFrame f) {
    Rectangle r = this.getBoundsForIconOf(f);
    r.width = f.getDesktopIcon().getPreferredSize().width;
    f.getDesktopIcon().setBounds(r);
    super.iconifyFrame(f);
  }
});
desktop.add(createFrame("looooooooooooong title #", 1));
desktop.add(createFrame("#", 0));
// ...
JInternalFrame f = new JInternalFrame(t + i, true, true, true, true);
f.setDesktopIcon(new JInternalFrame.JDesktopIcon(f) {
  @Override public Dimension getPreferredSize() {
    Dimension d = super.getPreferredSize();
    String title = f.getTitle();
    Font font = getFont();
    if (Objects.nonNull(font)) {
      FontMetrics fm = getFontMetrics(font);
      int titleW = SwingUtilities.computeStringWidth(fm, title);

      // @see javax/swing/plaf/basic/BasicInternalFrameTitlePane.java
      // Handler#minimumLayoutSize(Container)
      // Calculate width.
      int buttonsW = 22;
      if (f.isClosable()) {
        buttonsW += 19;
      }
      if (f.isMaximizable()) {
        buttonsW += 19;
      }
      if (f.isIconifiable()) {
        buttonsW += 19;
      }
      Insets i = getInsets();
      // 2: Magic number of gap between icons
      d.width = buttonsW + i.left + i.right + titleW + 2 + 2 + 2;
      // 27: Magic number for NimbusLookAndFeel
      d.height = Math.min(27, d.height);
      System.out.println("BasicInternalFrameTitlePane: " + d.width);
    }
    return d;
  }

  // private void testWidth() {
  //   Dimension dim = getLayout().minimumLayoutSize(this);
  //   System.out.println("minimumLayoutSize: " + dim.width);
  //
  //   int buttonsW = SwingUtils.stream(this)
  //       .filter(AbstractButton.class::isInstance)
  //       .mapToInt(c -> c.getPreferredSize().width)
  //       .sum();
  //   System.out.println("Total width of all buttons: " + buttonsW);
  // }
});