import java.awt.*;
/** 
 Program: 	EssentialRunner application
 Purpose: 	simple demonstration of a runnable applet 
 @author 	john@december.com 
 @version	1.61; 21 Nov 95 
 Note:          working on conversion to beta 1.00
 */

public class EssentialRunner extends java.applet.Applet implements Runnable {

    private Thread flow;
    boolean done, pause;
    int sizewidth = 400;
    int interval = 10;   
    int x, y, cycle;

    public void init() {
	resize(sizewidth, sizewidth);
    }

    public void start() {
        done = false;
        pause = false;
        x = 0;
        y = 0;
        cycle = 0;
        flow = new Thread(this);
        flow.start();
    }

    public void run() {
        try {
            while (!done) {
               Thread.sleep(interval); 
               if (!pause) repaint();
            }
        }
        catch (InterruptedException e){};
    }

    public void update(Graphics context) {
	context.setColor(Color.green);
	context.drawLine(sizewidth/2, sizewidth/2, x, y);
        y = y + interval;
        if (y > sizewidth) {
            y = 0; 
            cycle++;
            if ((cycle%2) == 0)
               x = cycle*interval;
            else 
               x = sizewidth - cycle*interval;
        }
    }

    public boolean mouseDown(java.awt.Event evt, int x, int y) { 
       pause = !pause;
       return (true);
    }

    public void stop() {
       done = true;
       flow.stop();
    }
     
}