private void addPainter(myjava.gui.syntax.Painter painter) {
   EntryListPanel newPanel = new EntryListPanel(painter);
   listPanelSet.add(newPanel);
   centerPanel.add(newPanel, painter.getName());
   painterComboBox.removeItemListener(painterChangeListener);
   painterComboBox.removeAllItems();
   for (EntryListPanel p : listPanelSet) {
     painterComboBox.addItem(p.getPainter());
   }
   removedPainters.remove(painter);
   painterComboBox.addItemListener(painterChangeListener);
 }
  public SyntaxTab() {
    super(new BorderLayout(), "Syntax highlighting");
    /*
     * upper checkboxes
     */
    JPanel upper = new JPanel(new GridLayout(2, 1, 0, 0));
    upper.setOpaque(false);
    upper.add(MyPanel.wrap(highlightSyntax));
    upper.add(MyPanel.wrap(matchBracket));
    highlightSyntax.addActionListener(
        new ActionListener() {
          @Override
          public void actionPerformed(ActionEvent ev) {
            SyntaxTab.this.updateComponentStatus();
          }
        });
    this.add(upper, BorderLayout.PAGE_START);
    /*
     * upper panel (painters)
     */
    painterComboBox.setSelectedItem(myjava.gui.syntax.Painter.getCurrentInstance());
    painterComboBox.setFont(f13);
    if (isMetal) painterComboBox.setBackground(Color.WHITE);
    painterComboBox.addItemListener(this.painterChangeListener);
    JButton addPainter =
        new MyButton("+") {
          {
            if (isMetal) {
              this.setPreferredSize(new Dimension(28, 28));
            }
          }

          @Override
          public void actionPerformed(ActionEvent ev) {
            String name;
            do {
              name =
                  JOptionPane.showInputDialog(
                      SyntaxTab.this, "Enter a name:", "Name", JOptionPane.QUESTION_MESSAGE);
            } while (!myjava.gui.syntax.Painter.isValidPrompt(name, SyntaxTab.this));
            if ((name != null) && (!name.isEmpty())) {
              // name is valid, neither cancelled nor pressed enter directly
              myjava.gui.syntax.Painter newPainter =
                  ((myjava.gui.syntax.Painter) (painterComboBox.getSelectedItem()))
                      .newInstance(name);
              addPainter(newPainter);
              System.out.println("now set, should call listener");
              painterComboBox.setSelectedItem(newPainter); // auto-call ItemListener(s)
            }
          }
        };
    JButton removePainter =
        new MyButton("-") {
          {
            if (isMetal) {
              this.setPreferredSize(new Dimension(28, 28));
            }
          }

          @Override
          public void actionPerformed(ActionEvent ev) {
            myjava.gui.syntax.Painter painter =
                (myjava.gui.syntax.Painter) (painterComboBox.getSelectedItem());
            if (painter.equals(myjava.gui.syntax.Painter.getDefaultInstance())) {
              JOptionPane.showMessageDialog(
                  SyntaxTab.this,
                  "The default painter cannot be removed.",
                  "Error",
                  JOptionPane.ERROR_MESSAGE);
            } else {
              int option =
                  JOptionPane.showConfirmDialog(
                      SyntaxTab.this,
                      "Remove painter \"" + painter.getName() + "\"?",
                      "Confirm",
                      JOptionPane.YES_NO_OPTION);
              if (option == JOptionPane.YES_OPTION) {
                // remove "painter"
                removedPainters.add(painter);
                painterComboBox.removeItemListener(painterChangeListener);
                painterComboBox.setSelectedItem(myjava.gui.syntax.Painter.getDefaultInstance());
                painterComboBox.removeItem(painter);
                for (Iterator<EntryListPanel> it = listPanelSet.iterator(); it.hasNext(); ) {
                  EntryListPanel panel = it.next();
                  if (panel.getPainter().getName().equals(painter.getName())) {
                    System.out.println("removing, then break");
                    it.remove();
                    centerPanel.remove(panel);
                    break;
                  }
                }
                painterComboBox.addItemListener(painterChangeListener);
                cardLayout.show(
                    centerPanel, myjava.gui.syntax.Painter.getDefaultInstance().getName());
              }
            }
          }
        };
    // lower part
    JPanel center = new JPanel(new BorderLayout());
    JLabel selectLabel = new MyLabel("Selected painter:");
    center.add(
        MyPanel.wrap(MyPanel.CENTER, selectLabel, painterComboBox, addPainter, removePainter),
        BorderLayout.PAGE_START);
    componentSet.addAll(Arrays.asList(selectLabel, addPainter, removePainter));
    center.add(centerPanel, BorderLayout.CENTER);
    this.add(center, BorderLayout.CENTER);
    cardLayout.show(centerPanel, myjava.gui.syntax.Painter.getCurrentInstance().getName());
  }