Martin Wattenberg

import java.awt.*;
import java.applet.*;

public class ConnectApplet extends Applet
       implements Runnable {
   Point current;
   Point[] p=new Point[3];
   Thread animation;
   int w,h;
   Image pictureImage;
   Graphics picture;

   public void init() {
      w=size().width; h=size().height;
      pictureImage=createImage(w,h);
      picture=pictureImage.getGraphics();
      p[0]=new Point(w/2,100);
      p[1]=new Point(w/2+70,170);
      p[2]=new Point(w/2-70,170);
      current=p[0];
   }
   public void start() {
      animation=new Thread(this);
      animation.start();
   }
   public void stop() { animation=null; }
   public void run() {
      while (animation==Thread.currentThread()) {
         updatePicture();
         repaint();
         try {Thread.sleep(20);} catch (Exception e) {}
      }
   }
   public void update(Graphics g) { paint(g); }
   public synchronized void paint(Graphics g) {
      g.drawImage(pictureImage,0,0,null);
   }

   // key: code in gray makes the program run.
   //      code in black draws the picture.

   public boolean mouseDown(Event e, int x, int y) {
      int shortest=Integer.MAX_VALUE;
      for (int i=0; i<p.length; i++) {
         int d2=(p[i].x-x)*(p[i].x-x)+
                (p[i].y-y)*(p[i].y-y);
          if (d2<=shortest) {
             current=p[i];
             shortest=d2;
          }
      }
      return mouseDrag(e,x,y);
   }
   public boolean mouseDrag(Event e, int x, int y) {
      current.x=x; current.y=y; return true;
   }

   synchronized void updatePicture() {
      for (int i=0; i<5000; i++) {
         int x=(int)(w*Math.random());
         int y=(int)(h*Math.random());
         long a1=f(p[0],p[1],x,y),
              a2=f(p[1],p[2],x,y),
              a3=f(p[2],p[0],x,y);
         picture.setColor(
            (int)(a1*a2*a3)>0 ? a1*a2>0 && a2*a3>0 ?
            Color.white : Color.gray : Color.black);
         picture.drawLine(x,y,x,y);
      }
   }
   long f(Point p1, Point p2, int x, int y) {
      return ((p1.x-x)*(p2.y-y)-(p1.y-y)*(p2.x-x))/13;
   }
}