import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.util.*;
/**
 * Ex2 -- a JFrame with a canvas
 * 
 * @author rpj 
 * @version 29xii06
 */
public class Ex2 extends JFrame
{
    // constants
    private static final int SIZE = 400;
    private int lastX, lastY;
    private JButton clear;
    private ScribbleCanvas c;
    private Graphics g;
    
    /**
     * Constructor for objects of class Ex2
     */
    public Ex2()
    {
        setTitle("Scribble frame");
        setSize(SIZE,SIZE);
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Container pane = getContentPane();
        pane.setLayout(new BorderLayout());
        clear = new JButton("clear");
        clear.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                    c.reset();
                }
            });
        pane.add(clear, BorderLayout.SOUTH);
        c = new ScribbleCanvas();
        c.addMouseListener(new MouseAdapter() {
                public void mousePressed(MouseEvent e) {
                    lastX = e.getX();
                    lastY = e.getY();
                }
            });
        
        // Define, instantiate and register a MouseMotionListener object.
        c.addMouseMotionListener(new MouseMotionAdapter() {
                public void mouseDragged(MouseEvent e) {    
                    int x = e.getX(), y = e.getY();
                    c.add(new Segment(lastX, lastY, x, y));
                    lastX = x; lastY = y;
                }
            });
        pane.add(c, BorderLayout.CENTER);
        validate();
    }
    
    /**
     * main
     * 
     * @param  args   the commandline arguments
     */
    public static void main(String[] args)
    {
        Ex2 foo = new Ex2();
    }
}

class Segment {
    private int x1, y1, x2, y2;
    public Segment(int a, int b, int c, int d) {
        x1 = a; y1 = b; x2 = c; y2 = d;
    }
    public void draw(Graphics g) {
        g.drawLine(x1, y1, x2, y2);
    }
}

class ScribbleCanvas extends Canvas {
    private Vector<Segment> segments;
    public ScribbleCanvas() {
        segments = new Vector<Segment>();
    }
    public void reset() {
        segments.removeAllElements();
        repaint();
    }
    public void add (Segment s) {
        segments.add(s);
        repaint();
    }
    public void paint(Graphics g) {
        for (Segment s : segments) {
            s.draw(g);
        }
    }
}