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

/** 
 * This application demonstrates how XOR and Paint mode work in Java.
 * The application draws a black and a yellow rectangle side-by-side.
 * Next it sets the XOR mode to the background color and draws 2 red
 * rectangles, one inside the black and yellow rectangles and one outside
 * the two rectangles. Finally it resets the mode to Paint mode and draws
 * another red rectangle within the black and yellow rectangles.
 *
 * USER INTERACTION
 *
 * If you repeatedly click on the window you can observe how the XOR mode 
 * toggles the first two red rectangles but not the third. You can also see how
 * the XOR mode correctly draws the red rectangle on the background but produces
 * weird colors on the black and yellow rectangles.
 **/
public class xor extends JFrame {
    boolean first = true;

    public xor() {
	getContentPane().add(new myPanel());
    }

    static void createGUI() {
	xor xorObject = new xor();
	xorObject.pack();
	xorObject.setVisible(true);
    }

    static public void main(String args[]) {
	//Execute a job on the event-dispatching thread:
	//creating this applet's GUI.
	try {
	    javax.swing.SwingUtilities.invokeAndWait(new Runnable() {
		    public void run() {
			createGUI();
		    }
		});
	    } catch (Exception e) {
		System.err.println("createGUI didn't successfully complete");
	    }
    }

    class myPanel extends JPanel {
        public myPanel() {
	    addMouseListener(new MouseAdapter() {
		public void mouseClicked(MouseEvent me) {
		    repaint();
		}
	    });
	}

	public Dimension getPreferredSize() {
	    return new Dimension(200,200);
	}

	public void paintComponent(Graphics gr) {
	    Graphics g = gr.create();

	    // only draw the background graphics the first time paintComponent
	    // is called. If we always redraw the background graphics then
	    // xor will have no effect. The point with XOR is that the 
	    // background graphics do not have to be redrawn.
	    if (first) {
		g.setColor(Color.black);
		g.fillRect(0,0,100,100);
		g.setColor(Color.yellow);
		g.fillRect(100,0,100,100);
		first = false;
	    }

	    // draw the two red xor rectangles. One will be drawn over the
	    // black and yellow rectangles and the other will be drawn over
	    // a clear area of the panel
	    g.setColor(getBackground());
	    g.setXORMode(Color.red);
	    g.drawRect(50,20,100,60);
	    g.drawRect(50,120,100,60);
	    
	    // revert to paint mode in order to draw the last red rectangle.
	    // This rectangle appears over the black and yellow rectangles.
	    g.setPaintMode();
	    g.setColor(Color.red);
	    g.drawRect(70, 40, 60, 20);
	}
    }
}