Добавление JPanel в JScrollPane

У меня есть JPanel, в котором отрисовывается дерево и, очевидно, размер дерева может превышать размер экрана. Поэтому мне нужно добавить JPanel в JScrollPane, но скролл наотрез отказывается работать (даже глупое копирование рабочего кода для моей конкретной задачи не помог спасти ситуацию).

Класс App, в котором реализовано все окно

import javax.swing.*;
import java.awt.*;

public class App {
    private JFrame frame;
    private JTextField heightTextFiled;
    private PaintPanel graphicPanel;

    public App() {
        createFrame();
        initElements();
    }

    private void createFrame() {
        frame = new JFrame("Моё страдание");
        frame.setSize(1280, 720);
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setResizable(false);
    }

    public void show() {
        frame.setVisible(true);
    }

    private void initElements() {
        frame.setLayout(new BorderLayout());
        Box leftPanel = createLeftPanel();
        frame.add(leftPanel, BorderLayout.WEST);

        graphicPanel = new PaintPanel();
        JScrollPane scrollPanel = new JScrollPane(graphicPanel,
               JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
               JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
        frame.add(scrollPanel);

    }

    private Box createLeftPanel() {
        Box panel = Box.createVerticalBox();

        JLabel title = new JLabel("Раскраска дерева");
        Font font = new Font(Font.SANS_SERIF, Font.BOLD, 20);
        title.setFont(font); 
        panel.add(title);

        panel.add(Box.createVerticalStrut(40));

        JLabel inputLabel = new JLabel("Введите высоту дерева");
        inputLabel.setFont(font);
        panel.add(inputLabel);

        panel.add(Box.createVerticalStrut(10));
        heightTextFiled = new JTextField();
        heightTextFiled.setMaximumSize(new Dimension(500, 30));
        heightTextFiled.setFont(new Font(Font.DIALOG_INPUT, Font.PLAIN, 20));
        panel.add(heightTextFiled);

        panel.add(Box.createVerticalStrut(10));

        JButton buttonPaint = new JButton("Нарисовать");
        buttonPaint.setMaximumSize(new Dimension(400, 50));
        buttonPaint.setFont(font);
        panel.add(buttonPaint);

        buttonPaint.addActionListener(e -> {
            if (!heightTextFiled.getText().equals("")) {
                try {
                    int height = Integer.parseInt(heightTextFiled.getText());
                    if (height <= 0) {
                        throw new NumberFormatException();
                    }
                    graphicPanel.paintTree(height);
                } catch (NumberFormatException ex) {
                    JOptionPane.showMessageDialog(null, "Invalid input", "Error", JOptionPane.ERROR_MESSAGE);
                }
            }
        });
        panel.add(Box.createVerticalGlue());

        return panel;

    }
}

Класс PaintPanel

import javax.swing.*;
import java.awt.*;

public class PaintPanel extends JPanel {

    private ColoredBinaryTree tree = new ColoredBinaryTree(1);

    public void paint(Graphics g) {
        tree.colorize();
        g.setColor(Color.lightGray);
        g.fillRect(0, 0, getWidth(), getHeight());
        PaintTree.point(tree, g);
    }

    public void paintTree(int height){
        this.tree = new ColoredBinaryTree(height);
        repaint();
    }
}

Клас PaintTRee - отрисовка дерева

import java.awt.*;

class PaintTree {
    private static final int TREE_NODE_WIDTH = 70,
            TREE_NODE_HEIGHT = 30,
            HORIZONTAL_INDENT = 10,
            VERTICAL_INDENT = 50;

    private static class NodeDrawResult {

        int center;
         int maxX;
        int maxY;

        NodeDrawResult(int center, int maxX, int maxY) {
            this.center = center;
            this.maxX = maxX;
            this.maxY = maxY;
        }
    }

    private static NodeDrawResult paint(ColoredBinaryTree.Node node, Graphics2D g2d, int x, int y) {
        if (node == null) {
            return null;
        }

        NodeDrawResult leftResult = paint(node.getLeft(), g2d, x, y + (TREE_NODE_HEIGHT + VERTICAL_INDENT));
        int rightX = (leftResult != null) ? leftResult.maxX : x + (TREE_NODE_WIDTH + HORIZONTAL_INDENT) / 2;
        NodeDrawResult rightResult = paint(node.getRight(), g2d, rightX, y + (TREE_NODE_HEIGHT + VERTICAL_INDENT));
        int thisX;
        if (leftResult == null) {
            thisX = x;
        } else if (rightResult == null) {
            thisX = Math.max(x + (TREE_NODE_WIDTH + HORIZONTAL_INDENT) / 2, leftResult.center + HORIZONTAL_INDENT / 2);
        } else {
            thisX = (leftResult.center + rightResult.center) / 2 - TREE_NODE_WIDTH / 2;
        }


        g2d.setColor(node.getColor());
        g2d.fillRect(thisX, y, TREE_NODE_WIDTH, TREE_NODE_HEIGHT);
        g2d.setColor(Color.BLACK);
        if (leftResult != null) {
            g2d.drawLine(thisX + TREE_NODE_WIDTH / 2, y + TREE_NODE_HEIGHT, leftResult.center, y + TREE_NODE_HEIGHT + VERTICAL_INDENT);
        }
        if (rightResult != null) {
            g2d.drawLine(thisX + TREE_NODE_WIDTH / 2, y + TREE_NODE_HEIGHT, rightResult.center, y + TREE_NODE_HEIGHT + VERTICAL_INDENT);
        }
        g2d.drawRect(thisX, y, TREE_NODE_WIDTH, TREE_NODE_HEIGHT);

        int maxX = Math.max((leftResult == null) ? 0 : leftResult.maxX, (rightResult == null) ? 0 : rightResult.maxX);
        int maxY = Math.max((leftResult == null) ? 0 : leftResult.maxY, (rightResult == null) ? 0 : rightResult.maxY);
        return new NodeDrawResult(
                thisX + TREE_NODE_WIDTH / 2,
                Math.max(thisX + TREE_NODE_WIDTH + HORIZONTAL_INDENT, maxX),
                Math.max(y + TREE_NODE_HEIGHT, maxY)
        );
    }

    static void point(ColoredBinaryTree tree, Graphics gr) {
        Graphics2D g2d = (Graphics2D) gr;
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        NodeDrawResult rootResult = paint(tree.getRoot(), g2d, HORIZONTAL_INDENT, HORIZONTAL_INDENT);
        new Point((rootResult == null) ? 0 : rootResult.maxX, (rootResult == null) ? 0 : rootResult.maxY + HORIZONTAL_INDENT);
    }
}

Вот что творится на экране