// From text by Cay Horstmann: Java Concepts, 2005.

import java.applet.Applet;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Line2D;

public class TicTacToe extends Applet {
    private static final int XMIN = 0, XMAX = 3, YMIN = 0, YMAX = 3;

    // converts user-coordinates to pixels for x (horizontal) scale - p. 175
    private double xpixel(double xuser) {
        return (xuser - XMIN) * (getWidth() - 1) / (XMAX - XMIN);
                        // note: getWidth() is an Applet method
    }
    
    // same for y (vertical) scale, assuming y increases upwards - p. 176
    private double ypixel(double yuser) {
        return (yuser - YMAX) * (getHeight() - 1) / (XMIN - XMAX);
             // note: accounts for pixels that actually increase downwards
    }
    
    /**
      Draws a tic-tac-toe board. The board consists of 2 horizonal lines
      and 2 vertical lines, and it always fills the window.
     */
    public void paint(Graphics g) {
        Graphics2D g2 = (Graphics2D)g;

        g2.draw(new Line2D.Double( // bottom horizontal line
            xpixel(0), ypixel(1), xpixel(3), ypixel(1)));
            
        g2.draw(new Line2D.Double( // top horizontal line
            xpixel(0), ypixel(2), xpixel(3), ypixel(2)));
            
        g2.draw(new Line2D.Double( // left vertical line
            xpixel(1), ypixel(0), xpixel(1), ypixel(3))); //note error in text
            
        g2.draw(new Line2D.Double( // right vertical line
            xpixel(2), ypixel(0), xpixel(2), ypixel(3)));
    }
}