private ModifiableFontPreferences ensureEditableFontPreferences() {
    if (!(fontPreferences instanceof ModifiableFontPreferences)) {
      ModifiableFontPreferences editableFontPreferences = new FontPreferencesImpl();
      fontPreferences.copyTo(editableFontPreferences);
      fontPreferences = editableFontPreferences;
      ((FontPreferencesImpl)fontPreferences).addChangeListener((source) -> initFonts());
    }
    return (ModifiableFontPreferences)fontPreferences;
  }
private ModifiableFontPreferences ensureEditableFontPreferences()