// Stuart Reges
// 10/10/04
//
// The DrawingPanel class provides a simple interface for drawing persistent
// images using a Graphics object.  An internal BufferedImage object is used
// to keep track of what has been drawn.  A client of the class simply
// constructs a DrawingPanel of a particular size and then draws on it with
// the Graphics object, setting the background color if they so choose.
//
// To ensure that the image is always displayed, a timer calls repaint at
// regular intervals.

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

public class DrawingPanel implements ActionListener {
    private JPanel myPanel;         // overall drawing panel
    private BufferedImage myImage;  // remembers drawing commands

    public static final int DELAY = 250;  // delay between repaints in millis

    // construct a drawing panel of given width and height enclosed in a frame
    public DrawingPanel(int width, int height) {
        JFrame frame = new JFrame("CSE142 Drawing Panel");
        frame.setResizable(false);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        myImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
        myPanel = new JPanel(new FlowLayout(FlowLayout.CENTER, 0, 0));
        myPanel.add(new JLabel(new ImageIcon(myImage)));
        frame.getContentPane().add(myPanel);
        myPanel.setPreferredSize(new Dimension(width, height));
        frame.pack();
        frame.setVisible(true);
        new Timer(DELAY, this).start();
    }

    // obtain the Graphics object to draw on the panel
    public Graphics getGraphics() {
        Graphics2D g2 = (Graphics2D)myImage.getGraphics();
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        return g2;
    }

    // set the background color of the drawing panel
    public void setBackground(Color c) {
        myPanel.setBackground(c);
    }

    // used for an internal timer that keeps repainting
    public void actionPerformed(ActionEvent e) {
        myPanel.repaint();
    }
}