Java terminal - development

Question

Looking at the DragonConsole source code, there are two modes it supports: inline and not inline. You're first picture where the scrollbar extends to the bottom is DragonConsole in inline mode.

In this mode it is just a single JTextPane which is then added to aJScrollPane. This is why the scrollbar extends to the bottom. It then adds a KeyListener (keyPressed method) and a CaretListener (caretUpdate function) to the JTextPane. Finally it uses a custom DocumentFilter implemented in the InputController class to get the console behavior you see.

So in summary:

Create JTextPane. Look at initializeConsole() in DragonConsole.java
Add CaretListener and KeyListener to that text pane. Look at caretUpdate() and keyPressed() in DragonConsole.java
Set custom DocumentFilter. Look at InputController.java (Actually setting the document style is done in the inializeConsole method.)

The way you did it is virtually the same as the way DragonConsole did it when NOT in inline mode. In this case, it uses a JTextPane for the output area, and a JTextArea for the input area and should look the same in regards to the scrollbar.

Edit: Here's a super simple example of an inline console.

public class Console extends JPanel implements KeyListener, CaretListener {

    private static final String PROMPT = ">>";

    private JScrollPane scrollPane;
    private JTextArea consoleTextPane;

    private int startIndex;

    public Console() {
        super();

        // Create a text area
        consoleTextPane = new JTextArea();
        consoleTextPane.setText(PROMPT);
        consoleTextPane.setBorder(null);
        // Wraps the text if it goes longer than a line, but NOT on word boundary
        // like a normal console
        consoleTextPane.setLineWrap(true);
        consoleTextPane.setWrapStyleWord(false);

        // Set the initial caret position
        startIndex = consoleTextPane.getText().length();
        consoleTextPane.setCaretPosition(startIndex);

        // Add the caret and key listeners
        consoleTextPane.addCaretListener(this);
        consoleTextPane.addKeyListener(this);

        // Scrollbar, always show the vertical one
        scrollPane = new JScrollPane(consoleTextPane);
        scrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
        scrollPane.setBorder(null);

        JPanel panelCenter = new JPanel(new BorderLayout());
        panelCenter.setPreferredSize(new Dimension(400, 200));
        panelCenter.add(scrollPane, BorderLayout.CENTER);

        add(panelCenter, BorderLayout.CENTER);
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Console");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        frame.add(new Console());
        frame.pack();
        frame.setVisible(true);
    }

    @Override
    public void keyTyped(KeyEvent e) {
        // All processing in keyPressed
    }

    @Override
    public void keyReleased(KeyEvent e) {
        // All processing in keyPressed
    }

    @Override
    public void keyPressed(KeyEvent e) {
        switch(e.getKeyCode()) {
            case KeyEvent.VK_ENTER:
                // ENTER key was pressed
                // Get the "Command"
                String command = consoleTextPane.getText().substring(startIndex);

                if (!command.isEmpty()) {
                    // TODO: do something with the command
                    consoleTextPane.append(System.lineSeparator() 
                            + "Command Entered: " + command);
                }

                // Update the start index and append a new prompt
                consoleTextPane.append(System.lineSeparator() + PROMPT);
                startIndex = consoleTextPane.getText().length();

                // Consume the ENTER key event so further processing is not
                // performed
                e.consume();
                break;
            case KeyEvent.VK_BACK_SPACE:
                // Make sure this is a valid delete
                if (consoleTextPane.getCaretPosition() <= startIndex) {
                    e.consume();
                    Toolkit.getDefaultToolkit().beep();
                }

                break;
            // TODO: add key presses here as desired
            default:
                //System.out.println("Unhandled: " + e.getKeyCode());
                break;
        }
    }

    @Override
    public void caretUpdate(CaretEvent e) {
        // Ensure that the caret position can only be a valid location
        if (e.getDot() < startIndex) {
            consoleTextPane.setCaretPosition(startIndex);
            Toolkit.getDefaultToolkit().beep();
        }
    }
}