general purpose animator

I got this general purpose animator from sun. I want to know if this could be used to do this:

I want to be able to have 4 items in a row, move one of them into the background getting smaller and moving one item at a time into the background as well, lets say from right to left. Then be able to bring them back to the foregroung one at a time in the opposite direction. If so what would have to be done. I know this is a big question. Answer the first part of the question, and if so I will break the question up into any questions.



import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;
import java.applet.AudioClip;
import java.util.Vector;
import java.util.Hashtable;
import java.util.Enumeration;
import java.net.URL;
import java.net.MalformedURLException;

/**
 * An applet that plays a sequence of images, as a loop or a one-shot.
 * Can have a soundtrack and/or sound effects tied to individual frames.
 * See the <a href="http://java.sun.com/applets/applets/Animator/">Animator
 * home page</a> for details and updates.
 *
 * @author Herb Jellinek
 * @version 1.10, 02/05/97
 */

public class Animator extends Applet
                      implements Runnable,
                         MouseListener {
   
    /**
     * The images, in display order (Images).
     */
    Vector images = null;

    /**
     * A table that maps images to image names - for error messages.
     */
    Hashtable imageNames = new Hashtable(10);

    /**
     * Duration of each image (Integers, in milliseconds).
     */
    Hashtable durations = null;

    /**
     * Sound effects for each image (AudioClips).
     */
    Hashtable sounds = null;

    /**
     * Position of each image (Points).
     */
    Hashtable positions = null;

    /**
     * MediaTracker 'class' ID numbers.
     */
    static final int STARTUP_ID    = 0;
    static final int BACKGROUND_ID = 1;
    static final int ANIMATION_ID  = 2;

    /**
     * Start-up image URL, if any.
     */
    URL startUpImageURL = null;

    /**
     * Start-up image, if any.
     */
    Image startUpImage = null;

    /**
     * Background image URL, if any.
     */
    URL backgroundImageURL = null;

    /**
     * Background image, if any.
     */
    Image backgroundImage = null;

    /**
     * Background color, if any.
     */
    Color backgroundColor = null;
   
    /**
     * The soundtrack's URL.
     */
    URL soundtrackURL = null;

    /**
     * The soundtrack.
     */
    AudioClip soundtrack = null;

    /**
     * URL to link to, if any.
     */
    URL hrefURL = null;

    /**
     * Frame target for that URL, if any.
     */
    String hrefTarget = null;

    /**
     * Our width.
     */
    int appWidth = 0;

    /**
     * Our height.
     */
    int appHeight = 0;

    /**
     * The directory or URL from which the images are loaded
     */
    URL imageSource = null;

    /**
     * The directory or URL from which the sounds are loaded
     */
    URL soundSource = null;

    /**
     * The thread animating the images.
     */
    Thread engine = null;

    /**
     * The current loop slot - index into 'images.'
     */
    int frameNum;

    /**
     * frameNum as an Object - suitable for use as a Hashtable key.
     */
    Integer frameNumKey;
   
    /**
     * The current X position (for painting).
     */
    int xPos = 0;
   
    /**
     * The current Y position (for painting).
     */
    int yPos = 0;
   
    /**
     * The default number of milliseconds to wait between frames.
     */
    public static final int defaultPause = 3900;
   
    /**
     * The global delay between images, which can be overridden by
     * the PAUSE parameter.
     */
    int globalPause = defaultPause;

    /**
     * Whether or not the thread has been paused by the user.
     */
    boolean userPause = false;

    /**
     * Repeat the animation?  If false, just play it once.
     */
    boolean repeat;

    /**
     * The offscreen image, used in double buffering
     */
    Image offScrImage;

    /**
     * The offscreen graphics context, used in double buffering
     */
    Graphics offScrGC;

    /**
     * The MediaTracker we use to load our images.
     */
    MediaTracker tracker;
   
    /**
     * Can we paint yet?
     */
    boolean loaded = false;

    /**
     * Was there an initialization error?
     */
    boolean error = false;

    /**
     * What we call an image file in messages.
     */
    static final String imageLabel = "image";
   
    /**
     * What we call a sound file in messages.
     */
    static final String soundLabel = "sound";
   
    /**
     * Print silly debugging info?
     */
    static final boolean debug = false;

    /**
     * Where to find the source code and documentation - for informational
     * purposes.
     */
    static final String sourceLocation =
                   "http://java.sun.com/applets/applets/Animator/";

    /**
     * Instructions to the user: how to produce the popup.
     */
    static final String userInstructions = "shift-click for errors, info";

    /**
     * Applet info.
     */
    public String getAppletInfo() {
      return "Animator v1.10 (02/05/97), by Herb Jellinek";
    }

    /**
     * Parameter info.
     */
    public String[][] getParameterInfo() {
      String[][] info = {
          {"imagesource",       "URL",             "a directory"},
          {"startup",       "URL",             "image displayed at start-up"},
          {"backgroundcolor", "int",          "color (24-bit RGB number) displayed as background"},
          {"background",       "URL",             "image displayed as background"},
          {"startimage",       "int",             "index of first image"},
          {"endimage",       "int",             "index of last image"},
          {"namepattern",     "URL",          "generates indexed names"},
          {"images",          "URLs",         "list of image indices"},
          {"href",            "URL",            "page to visit on mouse-click"},
          {"target",            "name",            "frame to put that page in"},
          {"pause",               "int",             "global pause, milliseconds"},
          {"pauses",               "ints",       "individual pauses, milliseconds"},
          {"repeat",               "boolean",       "repeat? true or false"},
          {"positions",      "coordinates",       "path images will follow"},
          {"soundsource",      "URL",             "audio directory"},
          {"soundtrack",      "URL",             "background music"},
          {"sounds",            "URLs",            "list of audio samples"},
      };
      return info;
    }

    /**
     * Show a crude "About" box.  Displays credits, errors (if any), and
     * parameter values and documentation.
     */
    void showDescription() {
      DescriptionFrame description = new DescriptionFrame();
          
      description.tell("\t\t"+getAppletInfo()+"\n");
      description.tell("Updates, documentation at "+sourceLocation+"\n\n");
      description.tell("Document base: "+getDocumentBase()+"\n");
      description.tell("Code base: "+getCodeBase()+"\n\n");
      
      Object errors[] = tracker.getErrorsAny();
      if (errors != null) {
          description.tell("Applet image errors:\n");
          for (int i = 0; i < errors.length; i++) {
            if (errors[i] instanceof Image) {
                URL url = (URL)imageNames.get((Image)errors[i]);
                if (url != null) {
                  description.tell(" "+url+" not loaded\n");
                }
            }
          }
          description.tell("\n");
      }
      
      if (images == null || images.size() == 0) {
          description.tell("\n** No images loaded **\n\n");
      }

      description.tell("Applet parameters:\n");
      description.tell(" width = "+getParameter("WIDTH")+"\n");
      description.tell(" height = "+getParameter("HEIGHT")+"\n");
      
      String params[][] = getParameterInfo();
      for (int i = 0; i < params.length; i++) {
          String name = params[i][0];
          description.tell(" "+name+" = "+getParameter(name)+
                       "\t ["+params[i][2]+"]\n");
      }
      
      description.show();
    }

    /**
     * Print silly debugging info to the standard output.
     */
    void dbg(String s) {
      if (debug) {
          System.out.println("> "+s);
      }
    }

    /**
     * Local version of getParameter for debugging purposes.
     */
    public String getParam(String key) {
      String result = getParameter(key);
      dbg("getParameter("+key+") = "+result);
      return result;
    }

    final int setFrameNum(int newFrameNum) {
      frameNumKey = new Integer(frameNum = newFrameNum);
      return frameNum;
    }
   
    /**
     * Parse the IMAGES parameter.  It looks like
     * 1|2|3|4|5, etc., where each number (item) names a source image.
     *
     * @return a Vector of (URL) image file names.
     */
    Vector parseImages(String attr, String pattern)
    throws MalformedURLException {
      if (pattern == null) {
          pattern = "T%N.gif";
      }
      Vector result = new Vector(10);
      for (int i = 0; i < attr.length(); ) {
          int next = attr.indexOf('|', i);
          if (next == -1) next = attr.length();
          String file = attr.substring(i, next);
          result.addElement(new URL(imageSource, doSubst(pattern, file)));
          i = next + 1;
      }
      return result;
    }

    /**
     * Fetch an image and wait for it to come in.  Used to enforce a load
     * order for background and startup images.
     * Places URL and image in imageNames table.
     */
    Image fetchImageAndWait(URL imageURL, int trackerClass)
    throws InterruptedException {
      Image image = getImage(imageURL);
      tracker.addImage(image, trackerClass);
      imageNames.put(image, imageURL);
      tracker.waitForID(trackerClass);
      return image;
    }

    /**
     * Fetch the images named in the argument.  Is restartable.
     *
     * @param images a Vector of URLs
     * @return true if all went well, false otherwise.
     */
    boolean fetchImages(Vector images) {
      if (images == null) {
          return true;
      }

      int size = images.size();
      for (int i = 0; i < size; i++) {
          Object o = images.elementAt(i);
          if (o instanceof URL) {
            URL url = (URL)o;
            tellLoadingMsg(url, imageLabel);
            Image im = getImage(url);
            tracker.addImage(im, ANIMATION_ID);
            images.setElementAt(im, i);
            imageNames.put(im, url);
          }
      }

      try {
          tracker.waitForID(ANIMATION_ID);
      } catch (InterruptedException e) {}
      if (tracker.isErrorID(ANIMATION_ID)) {
          return false;
      }

      return true;
    }

    /**
     * Parse the SOUNDS parameter.  It looks like
     * train.au||hello.au||stop.au, etc., where each item refers to a
     * source image.  Empty items mean that the corresponding image
     * has no associated sound.
     *
     * @return a Hashtable of SoundClips keyed to Integer frame numbers.
     */
    Hashtable parseSounds(String attr, Vector images)
    throws MalformedURLException {
      Hashtable result = new Hashtable();

      int imageNum = 0;
      int numImages = images.size();
      for (int i = 0; i < attr.length(); ) {
          if (imageNum >= numImages) break;
          
          int next = attr.indexOf('|', i);
          if (next == -1) next = attr.length();
          
          String sound = attr.substring(i, next);
          if (sound.length() != 0) {
            result.put(new Integer(imageNum),
                     new URL(soundSource, sound));
          }
          i = next + 1;
          imageNum++;
      }

      return result;
    }

    /**
     * Fetch the sounds named in the argument.
     * Is restartable.
     *
     * @return URL of the first bogus file we hit, null if OK.
     */
    URL fetchSounds(Hashtable sounds) {
      for (Enumeration e = sounds.keys() ; e.hasMoreElements() ;) {
          Integer num = (Integer)e.nextElement();
          Object o = sounds.get(num);
          if (o instanceof URL) {
            URL file = (URL)o;
            tellLoadingMsg(file, soundLabel);
            try {
                sounds.put(num, getAudioClip(file));
            } catch (Exception ex) {
                return file;
            }
          }
      }
      return null;
    }

    /**
     * Parse the PAUSES parameter.  It looks like
     * 1000|500|||750, etc., where each item corresponds to a
     * source image.  Empty items mean that the corresponding image
     * has no special duration, and should use the global one.
     *
     * @return a Hashtable of Integer pauses keyed to Integer
     * frame numbers.
     */
    Hashtable parseDurations(String attr, Vector images) {
      Hashtable result = new Hashtable();

      int imageNum = 0;
      int numImages = images.size();
      for (int i = 0; i < attr.length(); ) {
          if (imageNum >= numImages) break;
          
          int next = attr.indexOf('|', i);
          if (next == -1) next = attr.length();

          if (i != next) {
            int duration = Integer.parseInt(attr.substring(i, next));
            result.put(new Integer(imageNum), new Integer(duration));
          } else {
            result.put(new Integer(imageNum),
                     new Integer(globalPause));
          }
          i = next + 1;
          imageNum++;
      }

      return result;
    }

    /**
     * Parse a String of form xxx@yyy and return a Point.
     */
    Point parsePoint(String s) throws ParseException {
      int atPos = s.indexOf('@');
      if (atPos == -1) throw new ParseException("Illegal position: "+s);
      return new Point(Integer.parseInt(s.substring(0, atPos)),
                   Integer.parseInt(s.substring(atPos + 1)));
    }


    /**
     * Parse the POSITIONS parameter.  It looks like
     * 10@30|11@31|||12@20, etc., where each item is an X@Y coordinate
     * corresponding to a source image.  Empty items mean that the
     * corresponding image has the same position as the preceding one.
     *
     * @return a Hashtable of Points keyed to Integer frame numbers.
     */
    Hashtable parsePositions(String param, Vector images)
    throws ParseException {
      Hashtable result = new Hashtable();

      int imageNum = 0;
      int numImages = images.size();
      for (int i = 0; i < param.length(); ) {
          if (imageNum >= numImages) break;
          
          int next = param.indexOf('|', i);
          if (next == -1) next = param.length();

          if (i != next) {
            result.put(new Integer(imageNum),
                     parsePoint(param.substring(i, next)));
          }
          i = next + 1;
          imageNum++;
      }

      return result;
    }
   
    /**
     * Get the dimensions of an image.
     * @return the image's dimensions.
     */
    Dimension getImageDimensions(Image im) {
      return new Dimension(im.getWidth(null), im.getHeight(null));
    }

    /**
     * Substitute an integer some number of times in a string, subject to
     * parameter strings embedded in the string.
     * Parameter strings:
     *   %N - substitute the integer as is, with no padding.
     *   %<digit>, for example %5 - substitute the integer left-padded with
     *        zeros to <digits> digits wide.
     *   %% - substitute a '%' here.
     * @param inStr the String to substitute within
     * @param theInt the int to substitute, as a String.
     */
    String doSubst(String inStr, String theInt) {
      String padStr = "0000000000";
      int length = inStr.length();
      StringBuffer result = new StringBuffer(length);
      
      for (int i = 0; i < length;) {
          char ch = inStr.charAt(i);
          if (ch == '%') {
            i++;
            if (i == length) {
                result.append(ch);
            } else {
                ch = inStr.charAt(i);
                if (ch == 'N' || ch == 'n') {
                  // just stick in the number, unmolested
                  result.append(theInt);
                  i++;
                } else {
                  int pad;
                  if ((pad = Character.digit(ch, 10)) != -1) {
                      // we've got a width value
                      String numStr = theInt;
                      String scr = padStr+numStr;
                      result.append(scr.substring(scr.length() - pad));
                      i++;
                  } else {
                      result.append(ch);
                      i++;
                  }
                }
            }
          } else {
            result.append(ch);
            i++;
          }
      }
      return result.toString();
    }      

    /**
     * Stuff a range of image names into a Vector.
     *
     * @return a Vector of image URLs.
     */
    Vector prepareImageRange(int startImage, int endImage, String pattern)
    throws MalformedURLException {
      Vector result = new Vector(Math.abs(endImage - startImage) + 1);
      if (pattern == null) {
          pattern = "T%N.gif";
      }
      if (startImage > endImage) {
          for (int i = startImage; i >= endImage; i--) {
            result.addElement(new URL(imageSource, doSubst(pattern, i+"")));
          }
      } else {
          for (int i = startImage; i <= endImage; i++) {
            result.addElement(new URL(imageSource, doSubst(pattern, i+"")));
          }
      }

      return result;
    }

   
    /**
     * Initialize the applet.  Get parameters.
     */
    public void init() {


      tracker = new MediaTracker(this);

      appWidth = getSize().width;
      appHeight = getSize().height;

      try {
          String param = getParam("IMAGESOURCE");      
          imageSource = (param == null) ? getDocumentBase() : new URL(getDocumentBase(), param + "/");
      
          String href = getParam("HREF");
          if (href != null) {
            try {
                hrefURL = new URL(getDocumentBase(), href);
            } catch (MalformedURLException e) {
                showParseError(e);
            }
          }

          hrefTarget = getParam("TARGET");
          if (hrefTarget == null) {
            hrefTarget = "_top";
          }

          param = getParam("PAUSE");
          globalPause =
            (param != null) ? Integer.parseInt(param) : defaultPause;

          param = getParam("REPEAT");
          repeat = (param == null) ? true : (param.equalsIgnoreCase("yes") ||
                                     param.equalsIgnoreCase("true"));

          int startImage = 1;
          int endImage = 1;
          param = getParam("ENDIMAGE");
          if (param != null) {
            endImage = Integer.parseInt(param);
            param = getParam("STARTIMAGE");
            if (param != null) {
                startImage = Integer.parseInt(param);
            }
            param = getParam("NAMEPATTERN");
            images = prepareImageRange(startImage, endImage, param);
          } else {
            param = getParam("STARTIMAGE");
            if (param != null) {
                startImage = Integer.parseInt(param);
                param = getParam("NAMEPATTERN");
                images = prepareImageRange(startImage, endImage, param);
            } else {
                param = getParam("IMAGES");
                if (param == null) {
                  showStatus("No legal IMAGES, STARTIMAGE, or ENDIMAGE "+
                           "specified.");
                  error = true;
                  return;
                } else {
                  images = parseImages(param, getParam("NAMEPATTERN"));
                }
            }
          }

          param = getParam("BACKGROUND");
          if (param != null) {
            backgroundImageURL = new URL(imageSource, param);
          }

          param = getParam("BACKGROUNDCOLOR");
          if (param != null) {
            backgroundColor = decodeColor(param);
          }

          param = getParam("STARTUP");
          if (param != null) {
            startUpImageURL = new URL(imageSource, param);
          }

          param = getParam("SOUNDSOURCE");
          soundSource = (param == null) ? imageSource : new URL(getDocumentBase(), param + "/");
      
          param = getParam("SOUNDS");
          if (param != null) {
            sounds = parseSounds(param, images);
          }

          param = getParam("PAUSES");
          if (param != null) {
            durations = parseDurations(param, images);
          }

          param = getParam("POSITIONS");
          if (param != null) {
            positions = parsePositions(param, images);
          }

          param = getParam("SOUNDTRACK");
          if (param != null) {
            soundtrackURL = new URL(soundSource, param);
          }
      } catch (MalformedURLException e) {
          showParseError(e);
      } catch (ParseException e) {
          showParseError(e);
      }

      setFrameNum(0);
      addMouseListener(this);
    }

    Color decodeColor(String s) {
      int val = 0;
      try {
          if (s.startsWith("0x")) {
            val = Integer.parseInt(s.substring(2), 16);
          } else if (s.startsWith("#")) {
            val = Integer.parseInt(s.substring(1), 16);
          } else if (s.startsWith("0") && s.length() > 1) {
            val = Integer.parseInt(s.substring(1), 8);
          } else {
            val = Integer.parseInt(s, 10);
          }
          return new Color(val);
      } catch (NumberFormatException e) {
          return null;
      }
    }

    void tellLoadingMsg(String file, String fileType) {
      showStatus("Animator: loading "+fileType+" "+file);
    }

    void tellLoadingMsg(URL url, String fileType) {
      tellLoadingMsg(url.toExternalForm(), fileType);
    }

    void clearLoadingMessage() {
      showStatus("");
    }
   
    void loadError(String fileName, String fileType) {
      String errorMsg = "Animator: Couldn't load "+fileType+" "+
          fileName;
      showStatus(errorMsg);
      System.err.println(errorMsg);
      error = true;
      repaint();
    }

    void loadError(URL badURL, String fileType) {
      loadError(badURL.toExternalForm(), fileType);
    }

    void loadErrors(Object errors[], String fileType) {
      for (int i = 0; i < errors.length; i++) {
          if (errors[i] instanceof Image) {
            URL url = (URL)imageNames.get((Image)errors[i]);
            if (url != null) {
                loadError(url, fileType);
            }
          }
      }
    }

    void showParseError(Exception e) {
      String errorMsg = "Animator: Parse error: "+e;
      showStatus(errorMsg);
      System.err.println(errorMsg);
      error = true;
      repaint();
    }

    void startPlaying() {
      if (soundtrack != null) {
          soundtrack.loop();
      }
    }

    void stopPlaying() {
      if (soundtrack != null) {
          soundtrack.stop();
      }
    }

    /**
     * Run the animation. This method is called by class Thread.
     * @see java.lang.Thread
     */
    public void run() {
      Thread me = Thread.currentThread();
      URL badURL;
      
      me.setPriority(Thread.MIN_PRIORITY);

      if (! loaded) {
          try {
            // ... to do a bunch of loading.
            if (startUpImageURL != null) {
                tellLoadingMsg(startUpImageURL, imageLabel);
                startUpImage = fetchImageAndWait(startUpImageURL,
                                         STARTUP_ID);
                if (tracker.isErrorID(STARTUP_ID)) {
                  loadError(startUpImageURL, "start-up image");
                }
                repaint();
            }
          
            if (backgroundImageURL != null) {
                tellLoadingMsg(backgroundImageURL, imageLabel);
                backgroundImage = fetchImageAndWait(backgroundImageURL,
                                          BACKGROUND_ID);
                if (tracker.isErrorID(BACKGROUND_ID)) {
                  loadError(backgroundImageURL, "background image");
                }
                repaint();
            }

            // Fetch the animation frames
            if (!fetchImages(images)) {
                // get images in error, tell user about first of them
                Object errors[] = tracker.getErrorsAny();
                loadErrors(errors, imageLabel);
                return;
            }

            if (soundtrackURL != null && soundtrack == null) {
                tellLoadingMsg(soundtrackURL, imageLabel);
                soundtrack = getAudioClip(soundtrackURL);
                if (soundtrack == null) {
                  loadError(soundtrackURL, "soundtrack");
                  return;
                }
            }

            if (sounds != null) {
                badURL = fetchSounds(sounds);
                if (badURL != null) {
                  loadError(badURL, soundLabel);
                  return;
                }
            }

            clearLoadingMessage();

            offScrImage = createImage(appWidth, appHeight);
            offScrGC = offScrImage.getGraphics();
            offScrGC.setColor(Color.lightGray);

            loaded = true;
            error = false;
          } catch (Exception e) {
            error = true;
            e.printStackTrace();
          }
      }

      if (userPause) {
          return;
      }

      if (repeat || frameNum < images.size()) {
          startPlaying();
      }

      try {
          if (images != null && images.size() > 1) {
            while (appWidth > 0 && appHeight > 0 && engine == me) {
                if (frameNum >= images.size()) {
                  if (!repeat) {
                      return;
                  }
                  setFrameNum(0);
                }
                repaint();

                if (sounds != null) {
                  AudioClip clip =
                      (AudioClip)sounds.get(frameNumKey);
                  if (clip != null) {
                      clip.play();
                  }
                }

                try {
                  Integer pause = null;
                  if (durations != null) {
                      pause = (Integer)durations.get(frameNumKey);
                  }
                  if (pause == null) {
                      Thread.sleep(globalPause);
                  } else {
                      Thread.sleep(pause.intValue());
                  }
                } catch (InterruptedException e) {
                  // Should we do anything?
                }
                setFrameNum(frameNum+1);
            }
          }
      } finally {
          stopPlaying();
      }
    }

    /**
     * No need to clear anything; just paint.
     */
    public void update(Graphics g) {
      paint(g);
    }

    /**
     * Paint the current frame.
     */
    public void paint(Graphics g) {
      if (error || !loaded) {
          if (startUpImage != null) {
            if (tracker.checkID(STARTUP_ID)) {
                if (backgroundColor != null) {
                  g.setColor(backgroundColor);
                  g.fillRect(0, 0, appWidth, appHeight);
                }
                g.drawImage(startUpImage, 0, 0, this);
            }
          } else {
            if (backgroundImage != null) {
                if (tracker.checkID(BACKGROUND_ID)) {
                  g.drawImage(backgroundImage, 0, 0, this);
                }
            } else {
                g.clearRect(0, 0, appWidth, appHeight);
            }
          }
      } else {
          if ((images != null) && (images.size() > 0) &&
            tracker.checkID(ANIMATION_ID)) {
            if (frameNum < images.size()) {
                if (backgroundImage == null) {
                  offScrGC.clearRect(0, 0, appWidth, appHeight);
                } else {
                  offScrGC.drawImage(backgroundImage, 0, 0, this);
                }

                Image image = (Image)images.elementAt(frameNum);
               
                Point pos = null;
                if (positions != null) {
                  pos = (Point)positions.get(frameNumKey);
                }
                if (pos != null) {
                  xPos = pos.x;
                  yPos = pos.y;
                }
                if (backgroundColor != null) {
                  offScrGC.setColor(backgroundColor);
                  offScrGC.fillRect(0, 0, appWidth, appHeight);
                  offScrGC.drawImage(image, xPos, yPos, backgroundColor,
                                 this);
                } else {
                  offScrGC.drawImage(image, xPos, yPos, this);
                }
                g.drawImage(offScrImage, 0, 0, this);
            } else {
                // no more animation, but need to draw something
                dbg("No more animation; drawing last image.");
                if (backgroundImage == null) {
                  g.fillRect(0, 0, appWidth, appHeight);
                } else {
                  g.drawImage(backgroundImage, 0, 0, this);
                }
                g.drawImage((Image)images.lastElement(), 0, 0, this);
            }
          }
      }
    }

    /**
     * Start the applet by forking an animation thread.
     */
    public void start() {
      if (engine == null) {
          engine = new Thread(this);
          engine.start();
      }
      showStatus(getAppletInfo());
    }

    /**
     * Stop the insanity, um, applet.
     */
    public void stop() {
      if (engine != null && engine.isAlive()) {
          engine.stop();
      }
      engine = null;
    }

    /**
     * Pause the thread when the user clicks the mouse in the applet.
     * If the thread has stopped (as in a non-repeat performance),
     * restart it.
     */
    public void mousePressed(MouseEvent event) {
      if ((event.getModifiers() & InputEvent.SHIFT_MASK) != 0) {
          showDescription();
          return;
      } else if (hrefURL != null) {
          //Let mouseClicked handle this.
          return;
        } else if (loaded) {
          if (engine != null && engine.isAlive()) {
            if (userPause) {
                engine.resume();
                startPlaying();
              } else {
                    engine.suspend();
                    stopPlaying();
              }
              userPause = !userPause;
          } else {
              userPause = false;
              setFrameNum(0);
              engine = new Thread(this);
              engine.start();
          }
      }
    }

    public void mouseClicked(MouseEvent event) {
      if ((hrefURL != null) &&
              ((event.getModifiers() & InputEvent.SHIFT_MASK) == 0)) {
          getAppletContext().showDocument(hrefURL, hrefTarget);
      }
    }

    public void mouseReleased(MouseEvent event) {
    }

    public void mouseEntered(MouseEvent event) {
      showStatus(getAppletInfo()+" -- "+userInstructions);
    }

    public void mouseExited(MouseEvent event) {
        showStatus("");
    }
   
}


/**
 * ParseException: signals a parameter parsing problem.
 */
class ParseException extends Exception {
    ParseException(String s) {
      super(s);
    }
}


/**
 * DescriptionFrame: implements a pop-up "About" box.
 */
class DescriptionFrame extends Frame
                   implements ActionListener {

    static final int rows = 27;
    static final int cols = 70;
   
    TextArea info;
    Button cancel;

    DescriptionFrame() {
      super("Animator v1.10");
      add("Center", info = new TextArea(rows, cols));
      info.setEditable(false);
      info.setBackground(Color.white);
      Panel buttons = new Panel();
      add("South", buttons);
      buttons.add(cancel = new Button("Cancel"));
      cancel.addActionListener(this);
      
      pack();
    }

    public void show() {
      info.select(0,0);
      super.show();
    }

    void tell(String s) {
      info.append(s);
    }

    public void actionPerformed(ActionEvent e) {
      setVisible(false);
    }
}