Here is where most of the features of the plugin will be
        implemented. To work with the dockable window API, the top level window
        will be a JPanel. The visible components reflect
        a simple layout. Inside the top-level panel we will place a scroll pane
        with a text area. Above the scroll pane we will place a panel containing
        a small tool bar and a label displaying the path of the current notepad
        file.
We have identified three user actions that need implementation
        here: chooseFile(),
        saveFile(), and
        copyToBuffer(). As noted earlier, we also want the
        text area to change its appearance in immediate response to a change in
        user options settings. In order to do that, the window class must
        respond to a PropertiesChanged message from the
        EditBus.
Unlike the EBPlugin class, the
        EBComponent interface does not deal with the
        component's actual subscribing and unsubscribing to the EditBus. To
        accomplish this, we use a pair of methods inherited from the Java
        platform's JComponent class that are called when
        the window is made visible, and when it is hidden. These two methods,
        addNotify() and
        removeNotify(), are overridden to add and remove
        the visible window from the list of EditBus subscribers.
We will provide for two minor features when the notepad is
        displayed in the floating window. First, when a floating plugin window
        is created, we will give the notepad text area input focus. Second, when
        the notepad if floating and has input focus, we will have the
        Escape key dismiss the notepad window. An
        AncestorListener and a
        KeyListener will implement these details.
Here is the listing for the data members, the constructor, and the
        implementation of the EBComponent
        interface:
public class QuickNotepad extends JPanel
    implements EBComponent
{
    private String filename;
    private String defaultFilename;
    private View view;
    private boolean floating;
    private QuickNotepadTextArea textArea;
    private QuickNotepadToolPanel toolPanel;
    //
    // Constructor
    //
    public QuickNotepad(View view, String position)
    {
        super(new BorderLayout());
        this.view = view;
        this.floating = position.equals(
            DockableWindowManager.FLOATING);
        this.filename = jEdit.getProperty(
            QuickNotepadPlugin.OPTION_PREFIX
            + "filepath");
        if(this.filename == null || this.filename.length() == 0)
        {
            this.filename = new String(jEdit.getSettingsDirectory()
                + File.separator + "qn.txt");
            jEdit.setProperty(QuickNotepadPlugin.OPTION_PREFIX
                + "filepath",this.filename);
        }
        this.defaultFilename = new String(this.filename);
        this.toolPanel = new QuickNotepadToolPanel(this);
        add(BorderLayout.NORTH, this.toolPanel);
        if(floating)
            this.setPreferredSize(new Dimension(500, 250));
        textArea = new QuickNotepadTextArea();
        textArea.setFont(QuickNotepadOptionPane.makeFont());
        textArea.addKeyListener(new KeyHandler());
        textArea.addAncestorListener(new AncestorHandler());
        JScrollPane pane = new JScrollPane(textArea);
        add(BorderLayout.CENTER, pane);
        readFile();
    }
    //
    // Attribute methods
    //
    // for toolBar display
    public String getFilename()
    {
        return filename;
    }
    //
    // EBComponent implementation
    //
    public void handleMessage(EBMessage message)
    {
        if (message instanceof PropertiesChanged)
        {
            propertiesChanged();
        }
    }
    private void propertiesChanged()
    {
        String propertyFilename = jEdit.getProperty(
            QuickNotepadPlugin.OPTION_PREFIX + "filepath");
        if(!defaultFilename.equals(propertyFilename))
        {
            saveFile();
            toolPanel.propertiesChanged();
            defaultFilename = propertyFilename.clone();
            filename = defaultFilename.clone();
            readFile();
        }
        Font newFont = QuickNotepadOptionPane.makeFont();
        if(!newFont.equals(textArea.getFont()))
        {
            textArea.setFont(newFont);
            textArea.invalidate();
        }
    }
    // These JComponent methods provide the appropriate points
    // to subscribe and unsubscribe this object to the EditBus
    public void addNotify()
    {
        super.addNotify();
        EditBus.addToBus(this);
    }
    public void removeNotify()
    {
        saveFile();
        super.removeNotify();
        EditBus.removeFromBus(this);
    }
    ...
}This listing refers to a
        QuickNotebookTextArea object. It is currently
        implemented as a JTextArea with word wrap and tab
        sizes hard-coded. Placing the object in a separate class will simply
        future modifications.