Text pane problem

Question

Hi guys,
I need a component which acts as a chat screen allowing me to append messages. Each chat message may be a different colour. I also need to set the font of the pane via my look and feel. This font is not included in html.
First I tried using a JEditorPane which worked fine, I could change the colour of the text using html formatting but could not use my own font.
My next option was to use a JTextPane (see code below) but when I append lots of messages the screen flickers and the scroll pane jumps to the top.
public class JLTextPane extends JTextPane {
    public void append(Color c, String s) {
        setEditable(true);
        StyleContext sc = StyleContext.getDefaultStyleContext();
        AttributeSet aset = sc.addAttribute(SimpleAttributeSet.EMPTY,
        StyleConstants.Foreground, c);
        setCaretPosition(getDocument().getLength()); // place caret at the end (with no selection)
        setCharacterAttributes(aset, false);
        replaceSelection(s); // there is no selection, so inserts at caret
        setCaretPosition(getDocument().getLength());
        setEditable(false);
    public void appendLine(Color c, String line) {
        if(getDocument().getLength() == 0) {
            append(c, line);
        } else {
            append(c, "\n" + line);
}I have run out of ideas. Any help?
Thanks

Answer 1

I could not find your alternative approach from your last post. I understand it must be frustrating dealing with people who are new to swing when you are so experienced yourself but after all this is a forum and thats why I'm here.
I have written you a test program which should be runnable.
public class MessagePanel extends JPanel {
    //the size of the panel
    private static final Dimension SIZE = new Dimension(400, 175);
    //the input box
    private JTextField _input;
    //the text pane itself
    private JTextPane _pane;
    public MessagePanel() {       
        initPanel();
        createPanel();
    public void initPanel() {
        setLayout(new GridBagLayout());
        setPreferredSize(SIZE);
    public void createPanel() {
        //create and setup the text pane
        _pane = new JTextPane();
        _pane.setEnabled(false);
        //create and setup the scrollable pane
        JScrollPane scrollable_pane = new JScrollPane(_pane);
        scrollable_pane.setPreferredSize(new Dimension(SIZE.width - 5, SIZE.height - 26));
        scrollable_pane.setVerticalScrollBarPolicy(
                    ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
        //add the components to the main panel
        GridBagConstraints c = new GridBagConstraints();
        c.gridx = 0;
        c.gridy = 0;
        add(scrollable_pane, c);
    private void append(Color colour, String message) {
        if(colour == null) {
            colour = Color.BLACK;
        StyleContext sc = StyleContext.getDefaultStyleContext();
        AttributeSet aset = sc.addAttribute(SimpleAttributeSet.EMPTY,
                StyleConstants.Foreground, colour);
        _pane.setCaretPosition(_pane.getDocument().getLength()); // place caret at the end (with no selection)
        _pane.setCharacterAttributes(aset, false);
        _pane.replaceSelection(message); // there is no selection, so inserts at caret
        _pane.setCaretPosition(_pane.getDocument().getLength());
    private void appendLine(Color c, String line) {
        if(_pane.getDocument().getLength() == 0) {
            append(c, line);
        } else {
            append(c, "\n" + line);
    public static void main(String[] args) {
        MessagePanel panel = new MessagePanel();
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(panel);
        frame.pack();
        frame.setVisible(true);
        Color[] colours = new Color[3];
        colours[0] = Color.RED;
        colours[1] = Color.BLUE;
        colours[2] = Color.ORANGE;
        for(int i = 0; i < 100; i++) {
            panel.appendLine(colours[i % 3], "Line: " + i);
}Could you possibly alter my code so that it can append lines without flicker and prevents the user from editing the JTextPane.
Thanks again.