deep-c-rsc/JCGO/sunawt/fix/sun/applet/AppletPanel.java

/*
 * This file is modified by Ivan Maidanski <ivmai@ivmaisoft.com>
 * Project name: JCGO-SUNAWT (http://www.ivmaisoft.com/jcgo/)
 */

/*
 * @(#)AppletPanel.java 1.99 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package sun.applet;

import java.util.*;
import java.io.*;
import java.net.JarURLConnection;
import java.net.URL;
import java.net.MalformedURLException;
import java.net.SocketPermission;
import java.net.UnknownHostException;
import java.net.URLConnection;
import java.net.InetAddress;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.awt.image.MemoryImageSource;
import java.awt.image.ColorModel;
import java.lang.reflect.InvocationTargetException;
import java.security.*;
import java.util.Collections;
import java.util.WeakHashMap;
import java.util.Locale;
import javax.swing.SwingUtilities;
import sun.misc.MessageUtils;
import sun.misc.Queue;
import sun.awt.AppContext;
import sun.security.util.SecurityConstants;
import sun.awt.SunToolkit;
import java.lang.ref.WeakReference;

/**
 * Applet panel class. The panel manages and manipulates the
 * applet as it is being loaded. It forks a separate thread in a new
 * thread group to call the applet's init(), start(), stop(), and
 * destroy() methods.
 *
 * @version     1.98, 12/17/02
 * @author      Arthur van Hoff
 */
public
abstract class AppletPanel extends Panel implements AppletStub, Runnable {

    /**
     * The applet (if loaded).
     */
    Applet applet;

    /**
     * Applet will allow initialization.  Should be
     * set to false if loading a serialized applet
     * that was pickled in the init=true state.
     */
    protected boolean doInit = true;


    /**
     * The classloader for the applet.
     */
    AppletClassLoader loader;

 /* applet event ids */
    public final static int APPLET_DISPOSE = 0;
    public final static int APPLET_LOAD = 1;
    public final static int APPLET_INIT = 2;
    public final static int APPLET_START = 3;
    public final static int APPLET_STOP = 4;
    public final static int APPLET_DESTROY = 5;
    public final static int APPLET_QUIT = 6;
    public final static int APPLET_ERROR = 7;

    /* send to the parent to force relayout */
    public final static int APPLET_RESIZE = 51234;

    /* sent to a (distant) parent to indicate that the applet is being
     * loaded or as completed loading
     */
    public final static int APPLET_LOADING = 51235;
    public final static int APPLET_LOADING_COMPLETED = 51236;

    /**
     * The current status. One of:
     *    APPLET_DISPOSE,
     *    APPLET_LOAD,
     *    APPLET_INIT,
     *    APPLET_START,
     *    APPLET_STOP,
     *    APPLET_DESTROY,
     *    APPLET_ERROR.
     */
    protected int status;

    /**
     * The thread for the applet.
     */
    Thread handler;


    /**
     * The initial applet size.
     */
    Dimension defaultAppletSize = new Dimension(10, 10);

    /**
     * The current applet size.
     */
    Dimension currentAppletSize = new Dimension(10, 10);

    MessageUtils mu = new MessageUtils();

    /**
     * The thread to use during applet loading
     */

    Thread loaderThread = null;

    /**
     * Flag to indicate that a loading has been cancelled
     */
    boolean loadAbortRequest = false;

    /* abstract classes */
    abstract protected String getCode();
    abstract protected String getJarFiles();
    abstract protected String getSerializedObject();

    abstract public int    getWidth();
    abstract public int    getHeight();

    private static int threadGroupNumber = 0;

    /*
     * Creates a thread to run the applet. This method is called
     * the each time an applet is loaded and reloaded.
     */
    synchronized void createAppletThread() {
        // Create a thread group for the applet, and start a new
        // thread to load the applet.
        String nm = "applet-" + getCode();
        loader = getClassLoader(getCodeBase(), getClassLoaderCacheKey());
        loader.grab(); // Keep this puppy around!
        ThreadGroup appletGroup = loader.getThreadGroup();

        handler = new Thread(appletGroup, this, "thread " + nm);
        // set the context class loader for this thread
        AccessController.doPrivileged(new PrivilegedAction() {
            public Object run() {
            handler.setContextClassLoader(loader);
            return null;
            }
        });
        handler.start();
    }

    void joinAppletThread() throws InterruptedException {
        if (handler != null) {
            handler.join();
            handler = null;
        }
    }

    void release() {
        if (loader != null) {
            loader.release();
            loader = null;
        }
    }

    /**
     * Construct an applet viewer and start the applet.
     */
    public void init() {
        try {
            // Get the width (if any)
            defaultAppletSize.width = getWidth();
            currentAppletSize.width = defaultAppletSize.width;

            // Get the height (if any)
            defaultAppletSize.height = getHeight();
            currentAppletSize.height = defaultAppletSize.height;

        } catch (NumberFormatException e) {
            // Turn on the error flag and let TagAppletPanel
            // do the right thing.
            status = APPLET_ERROR;
            showAppletStatus("badattribute.exception");
            showAppletLog("badattribute.exception");
            showAppletException(e);
        }

        setLayout(new BorderLayout());

        createAppletThread();
    }

    /**
     * Minimum size
     */
    public Dimension minimumSize() {
        return new Dimension(defaultAppletSize.width,
                             defaultAppletSize.height);
    }

    /**
     * Preferred size
     */
    public Dimension preferredSize() {
        return new Dimension(currentAppletSize.width,
                             currentAppletSize.height);
    }

    private AppletListener listeners;
    /**
     * AppletEvent Queue
     */
    private Queue queue = null;


    synchronized public void addAppletListener(AppletListener l) {
        listeners = AppletEventMulticaster.add(listeners, l);
    }

    synchronized public void removeAppletListener(AppletListener l) {
        listeners = AppletEventMulticaster.remove(listeners, l);
    }

    /**
     * Dispatch event to the listeners..
     */
    public void dispatchAppletEvent(int id, Object argument) {
        //System.out.println("SEND= " + id);
        if (listeners != null) {
            AppletEvent evt = new AppletEvent(this, id, argument);
            listeners.appletStateChanged(evt);
        }
    }

    /**
     * Send an event. Queue it for execution by the handler thread.
     */
    public void sendEvent(int id) {
        synchronized(this) {
            if (queue == null) {
                //System.out.println("SEND0= " + id);
                queue = new Queue();
            }
            Integer eventId = new Integer(id);
            queue.enqueue(eventId);
            notifyAll();
        }
        if (id == APPLET_QUIT) {
            try {
                joinAppletThread(); // Let the applet event handler exit
            } catch (InterruptedException e) {
            }

            // AppletClassLoader.release() must be called by a Thread
            // not within the applet's ThreadGroup
            if (loader == null)
                loader = getClassLoader(getCodeBase(), getClassLoaderCacheKey());
            release();
        }
    }

    /**
     * Get an event from the queue.
     */
    synchronized AppletEvent getNextEvent() throws InterruptedException {
        while (queue == null || queue.isEmpty()) {
            wait();
        }
        Integer eventId = (Integer)queue.dequeue();
        return new AppletEvent(this, eventId.intValue(), null);
    }

    boolean emptyEventQueue() {
        if ((queue == null) || (queue.isEmpty()))
            return true;
        else
            return false;
    }

    /**
     * Execute applet events.
     */
    public void run() {

        Thread curThread = Thread.currentThread();
        if (curThread == loaderThread) {
            // if we are in the loader thread, cause
            // loading to occur.  We may exit this with
            // status being APPLET_DISPOSE, APPLET_ERROR,
            // or APPLET_LOAD
            runLoader();
            return;
        }

        boolean disposed = false;
        while (!disposed && !curThread.isInterrupted()) {
            AppletEvent evt;
            try {
                evt = getNextEvent();
            } catch (InterruptedException e) {
                showAppletStatus("bail");
                return;
            }

            //showAppletStatus("EVENT = " + evt.getID());
            try {
                switch (evt.getID()) {
                    case APPLET_LOAD:
                    if (!okToLoad()) {
                        break;
                    }
                    // This complexity allows laoding of applets to be
                    // interruptable.  The actual thread loading runs
                    // in a separate thread, so it can be interrupted
                    // without harming the applet thread.
                    // So that we don't have to worry about
                    // concurrency issues, the main applet thread waits
                    // until the loader thread terminates.
                    // (one way or another).
                    if (loaderThread == null) {
                        // REMIND: do we want a name?
                        //System.out.println("------------------- loading applet");
                        setLoaderThread(new Thread(this));
                        loaderThread.start();
                        // we get to go to sleep while this runs
                        loaderThread.join();
                        setLoaderThread(null);
                    } else {
                        // REMIND: issue an error -- this case should never
                        // occur.
                    }
                    break;


                  case APPLET_INIT:
                    if (status != APPLET_LOAD) {
                        showAppletStatus("notloaded");
                        break;
                    }
                    applet.resize(defaultAppletSize);
                    if (doInit) {
                        applet.init();
                    }

                    //Need the default(fallback) font to be created in this AppContext
                    Font f = getFont();
                    if (f == null ||
                        "dialog".equals(f.getFamily().toLowerCase(Locale.ENGLISH)) &&
                        f.getSize() == 12 && f.getStyle() == Font.PLAIN) {
                        setFont(new Font("Dialog", Font.PLAIN, 12));
                    }

                    doInit = true;      // allow restarts
                    validate();
                    status = APPLET_INIT;
                    showAppletStatus("inited");
                    break;

                  case APPLET_START:
                  {
                    if (status != APPLET_INIT) {
                        showAppletStatus("notinited");
                        break;
                    }
                    applet.resize(currentAppletSize);
                    applet.start();
                    validate();

                    // Show the applet in event dispatch thread
                    // to avoid deadlock.
                    try
                    {
                        final Applet a = applet;

                        SwingUtilities.invokeAndWait(new Runnable()
                        {
                            public void run()
                            {
                                a.show();

                                /*
                                 * Fix for BugTraq ID 4041703.
                                 * Set the default focus for an applet.
                                 */
                                if (hasInitialFocus())
                                    setDefaultFocus();
                            }
                        });
                    }
                    catch(InterruptedException ie)
                    {
                    }
                    catch(InvocationTargetException ite)
                    {
                    }

                    status = APPLET_START;
                    showAppletStatus("started");
                    break;
                  }

                  case APPLET_STOP:
                    if (status != APPLET_START) {
                        showAppletStatus("notstarted");
                        break;
                    }
                    status = APPLET_INIT;

                    // Show the applet in event dispatch thread
                    // to avoid deadlock.
                    try
                    {
                        final Applet a = applet;

                        SwingUtilities.invokeAndWait(new Runnable()
                        {
                            public void run()
                            {
                                a.hide();
                            }
                        });
                    }
                    catch(InterruptedException ie)
                    {
                    }
                    catch(InvocationTargetException ite)
                    {
                    }

                    applet.stop();
                    showAppletStatus("stopped");
                    break;

                  case APPLET_DESTROY:
                    if (status != APPLET_INIT) {
                        showAppletStatus("notstopped");
                        break;
                    }
                    status = APPLET_LOAD;
                    applet.destroy();
                    showAppletStatus("destroyed");
                    break;

                  case APPLET_DISPOSE:
                    if (status != APPLET_LOAD) {
                        showAppletStatus("notdestroyed");
                        break;
                    }
                    status = APPLET_DISPOSE;
                    remove(applet);
                    applet = null;
                    showAppletStatus("disposed");
                    disposed = true;
                    break;

                  case APPLET_QUIT:
                    return;
                }
            } catch (Exception e) {
                if (e.getMessage() != null) {
                    showAppletStatus("exception2", e.getClass().getName(),
                                     e.getMessage());
                } else {
                    showAppletStatus("exception", e.getClass().getName());
                }
                showAppletException(e);
            } catch (ThreadDeath e) {
                showAppletStatus("death");
                return;
            } catch (Error e) {
                if (e.getMessage() != null) {
                    showAppletStatus("error2", e.getClass().getName(),
                                     e.getMessage());
                } else {
                    showAppletStatus("error", e.getClass().getName());
                }
                showAppletException(e);
            }
            clearLoadAbortRequest();
        }
    }

    /*
     * Fix for BugTraq ID 4041703.
     * Set the focus to a reasonable default for an Applet.
     */
    private void setDefaultFocus() {
        Component toFocus = null;
        Container parent = getParent();
        if(parent != null) {
            if (parent instanceof Window) {
                toFocus = ((Window)parent).getMostRecentFocusOwner();
                if (toFocus == parent || toFocus == null) {
                    toFocus = parent.getFocusTraversalPolicy().
                        getInitialComponent((Window)parent);
                }
            } else if (parent.isFocusCycleRoot()) {
                toFocus = parent.getFocusTraversalPolicy().
                    getDefaultComponent(parent);
            }
        }
        if (toFocus != null) {
            toFocus.requestFocusInWindow();
        }
    }

    /**
     * Load the applet into memory.
     * Runs in a seperate (and interruptible) thread from the rest of the
     * applet event processing so that it can be gracefully interrupted from
     * things like HotJava.
     */
    private void runLoader() {
        if (status != APPLET_DISPOSE) {
            showAppletStatus("notdisposed");
            return;
        }

        dispatchAppletEvent(APPLET_LOADING, null);


        // REMIND -- might be cool to visually indicate loading here --
        // maybe do animation?
        status = APPLET_LOAD;

        // Create a class loader
        loader = getClassLoader(getCodeBase(), getClassLoaderCacheKey());

        // Load the archives if present.
        // REMIND - this probably should be done in a separate thread,
        // or at least the additional archives (epll).

        String code = getCode();
        try {
          loadJarFiles(loader);
          applet = createApplet(loader);
        } catch (ClassNotFoundException e) {
            status = APPLET_ERROR;
            showAppletStatus("notfound", code);
            showAppletLog("notfound", code);
            showAppletException(e);
            return;
        } catch (InstantiationException e) {
            status = APPLET_ERROR;
            showAppletStatus("nocreate", code);
            showAppletLog("nocreate", code);
            showAppletException(e);
            return;
        } catch (IllegalAccessException e) {
            status = APPLET_ERROR;
            showAppletStatus("noconstruct", code);
            showAppletLog("noconstruct", code);
            showAppletException(e);
            // sbb -- I added a return here
            return;
        } catch (Exception e) {
            status = APPLET_ERROR;
            showAppletStatus("exception", e.getMessage());
            showAppletException(e);
            return;
        } catch (ThreadDeath e) {
            status = APPLET_ERROR;
            showAppletStatus("death");
            return;
        } catch (Error e) {
            status = APPLET_ERROR;
            showAppletStatus("error", e.getMessage());
            showAppletException(e);
            return;
        } finally {
            // notify that loading is no longer going on
            dispatchAppletEvent(APPLET_LOADING_COMPLETED, null);
        }

        // Fixed #4508194: NullPointerException thrown during
        // quick page switch
        //
        if (applet != null)
        {
            // Stick it in the frame
            applet.setStub(this);
            applet.hide();
            add("Center", applet);
            showAppletStatus("loaded");
            validate();
        }
    }

    protected Applet createApplet(final AppletClassLoader loader) throws ClassNotFoundException,
    IllegalAccessException, IOException, InstantiationException, InterruptedException {
        final String serName = getSerializedObject();
        String code = getCode();

        if (code != null && serName != null) {
            System.err.println(amh.getMessage("runloader.err"));
//          return null;
            throw new InstantiationException("Either \"code\" or \"object\" should be specified, but not both.");
        }
        if (code == null && serName == null) {
            String msg = "nocode";
            status = APPLET_ERROR;
            showAppletStatus(msg);
            showAppletLog(msg);
            repaint();
        }
        if (code != null) {
            applet = (Applet)loader.loadCode(code).newInstance();
            doInit = true;
        } else {
            // serName is not null;
            InputStream is = (InputStream)
                java.security.AccessController.doPrivileged(
                new java.security.PrivilegedAction() {
                    public Object run() {
                        return loader.getResourceAsStream(serName);
                    }
            });
            ObjectInputStream ois =
                new AppletObjectInputStream(is, loader);
            Object serObject = ois.readObject();
            applet = (Applet) serObject;
            doInit = false; // skip over the first init
        }
        if (Thread.interrupted()) {
            try {
                status = APPLET_DISPOSE; // APPLET_ERROR?
                applet = null;
                // REMIND: This may not be exactly the right thing: the
                // status is set by the stop button and not necessarily
                // here.
                showAppletStatus("death");
            } finally {
                Thread.currentThread().interrupt(); // resignal interrupt
            }
            return null;
        }
        return applet;
    }

    protected void loadJarFiles(AppletClassLoader loader) throws IOException,
    InterruptedException {
        // Load the archives if present.
        // REMIND - this probably should be done in a separate thread,
        // or at least the additional archives (epll).
        String jarFiles = getJarFiles();

        if (jarFiles != null) {
            StringTokenizer st = new StringTokenizer(jarFiles, ",", false);
            while(st.hasMoreTokens()) {
                String tok = st.nextToken().trim();
                try {
                    loader.addJar(tok);
                } catch (IllegalArgumentException e) {
                    // bad archive name
                    continue;
                }
            }
        }
    }

    /**
     * Request that the loading of the applet be stopped.
     */
    protected synchronized void stopLoading() {
        // REMIND: fill in the body
        if (loaderThread != null) {
            //System.out.println("Interrupting applet loader thread: " + loaderThread);
            loaderThread.interrupt();
        } else {
            setLoadAbortRequest();
        }
    }


    protected synchronized boolean okToLoad() {
        return !loadAbortRequest;
    }

    protected synchronized void clearLoadAbortRequest() {
        loadAbortRequest = false;
    }

    protected synchronized void setLoadAbortRequest() {
        loadAbortRequest = true;
    }


    private synchronized void setLoaderThread(Thread loaderThread) {
        this.loaderThread = loaderThread;
    }

    public abstract boolean hasInitialFocus();

    protected abstract void updateHostIPFile(String host);

    /**
     * Return true when the applet has been started.
     */
    public boolean isActive() {
        return status == APPLET_START;
    }


    private EventQueue appEvtQ = null;
    /**
     * Is called when the applet wants to be resized.
     */
    public void appletResize(int width, int height) {
        currentAppletSize.width = width;
        currentAppletSize.height = height;
        final Dimension currentSize = new Dimension(currentAppletSize.width,
                                              currentAppletSize.height);

        if(loader != null) {
            AppContext appCtxt = loader.getAppContext();
            if(appCtxt != null)
               appEvtQ = (java.awt.EventQueue)appCtxt.get(AppContext.EVENT_QUEUE_KEY);
        }

        final AppletPanel ap = this;
        if (appEvtQ != null){
            appEvtQ.postEvent(new InvocationEvent(Toolkit.getDefaultToolkit(),
                              new Runnable(){
                              public void run(){
                                  if(ap != null)
                                  {
                                      ap.dispatchAppletEvent(APPLET_RESIZE, currentSize);
                                  }
                              }
            }));
        }
    }

    public void setBounds(int x, int y, int width, int height) {
        super.setBounds(x, y, width, height);
        currentAppletSize.width = width;
        currentAppletSize.height = height;
    }

    public Applet getApplet() {
        return applet;
    }

    /**
     * Status line. Called by the AppletPanel to provide
     * feedback on the Applet's state.
     */
    protected void showAppletStatus(String status) {
        getAppletContext().showStatus(amh.getMessage(status));
    }

    protected void showAppletStatus(String status, Object arg) {
        getAppletContext().showStatus(amh.getMessage(status, arg));
    }
    protected void showAppletStatus(String status, Object arg1, Object arg2) {
        getAppletContext().showStatus(amh.getMessage(status, arg1, arg2));
    }

    /**
     * Called by the AppletPanel to print to the log.
     */
    protected void showAppletLog(String msg) {
        System.out.println(amh.getMessage(msg));
    }

    protected void showAppletLog(String msg, Object arg) {
        System.out.println(amh.getMessage(msg, arg));
    }

    /**
     * Called by the AppletPanel to provide
     * feedback when an exception has happened.
     */
    protected void showAppletException(Throwable t) {
        t.printStackTrace();
        repaint();
    }

    /**
     * Get caching key for classloader cache
     */
    public String getClassLoaderCacheKey()
    {
        /**
         * Fixed #4501142: Classlaoder sharing policy doesn't
         * take "archive" into account. This will be overridden
         * by Java Plug-in.                     [stanleyh]
         */
        return getCodeBase().toString();
    }

    /**
     * The class loaders
    */
    private static HashMap classloaders = new HashMap();

    /**
     * Flush a class loader.
     */
    public static synchronized void flushClassLoader(String key) {
        classloaders.remove(key);
    }

    /**
     * Flush all class loaders.
     */
    public static synchronized void flushClassLoaders() {
        classloaders = new HashMap();
    }

    /**
     * This method actually creates an AppletClassLoader.
     *
     * It can be override by subclasses (such as the Plug-in)
     * to provide different classloaders.
     */
    protected AppletClassLoader createClassLoader(final URL codebase) {
        return new AppletClassLoader(codebase);
    }

    /**
     * Get a class loader. Create in a restricted context
     */
    synchronized AppletClassLoader getClassLoader(final URL codebase, final String key) {
        AppletClassLoader c = (AppletClassLoader)classloaders.get(key);
        if (c == null) {
            AccessControlContext acc =
                getAccessControlContext(codebase);
            c = (AppletClassLoader)
                AccessController.doPrivileged(new PrivilegedAction() {
                    public Object run() {
                        AppletClassLoader ac = createClassLoader(codebase);
                        /* Should the creation of the classloader be
                         * within the class synchronized block?  Since
                         * this class is used by the plugin, take care
                         * to avoid deadlocks, or specialize
                         * AppletPanel within the plugin.  It may take
                         * an arbitrary amount of time to create a
                         * class loader (involving getting Jar files
                         * etc.) and may block unrelated applets from
                         * finishing createAppletThread (due to the
                         * class synchronization). If
                         * createAppletThread does not finish quickly,
                         * the applet cannot process other messages,
                         * particularly messages such as destroy
                         * (which timeout when called from the browser).
                         */
                        synchronized (getClass()) {
                            AppletClassLoader res =
                                (AppletClassLoader)classloaders.get(key);
                            if (res == null) {
                                classloaders.put(key, ac);
                                return ac;
                            } else {
                                return res;
                            }
                        }
                    }
            },acc);
        }
        return c;
    }

    /**
     * get the context for the AppletClassLoader we are creating.
     * the context is granted permission to create the class loader,
     * connnect to the codebase, and whatever else the policy grants
     * to all codebases.
     */
    private AccessControlContext getAccessControlContext(final URL codebase) {

        PermissionCollection perms = (PermissionCollection)
            AccessController.doPrivileged(new PrivilegedAction() {
                public Object run() {
                    Policy p = java.security.Policy.getPolicy();
                    if (p != null) {
                        return p.getPermissions(new CodeSource(null, null));
                    } else {
                        return null;
                    }
                }
            });

        if (perms == null)
            perms = new Permissions();

        //XXX: this is needed to be able to create the classloader itself!

        perms.add(SecurityConstants.CREATE_CLASSLOADER_PERMISSION);

        URLConnection uc = null;
        Permission p;
        try {
            uc = codebase.openConnection();
            p = uc.getPermission();
        } catch (java.io.IOException ioe) {
            p = null;
        }

        if (p != null) {
            perms.add(p);
        }

        if (p instanceof FilePermission) {

            String path = p.getName();

            int endIndex = path.lastIndexOf(File.separatorChar);
            if (endIndex != -1) {
                path = path.substring(0, endIndex + 1);

                if (path.endsWith(File.separator)) {
                    path += "-";
                }
                perms.add(new FilePermission(path,
                        SecurityConstants.FILE_READ_ACTION));
            }
        } else {
            URL url = codebase;
            if (uc instanceof JarURLConnection) {
                url = ((JarURLConnection)uc).getJarFileURL();
            }
            String host = url.getHost();
            if (host != null && host.length() > 0) {
                updateHostIPFile(host);
                perms.add(new SocketPermission(host,
                        SecurityConstants.SOCKET_CONNECT_ACCEPT_ACTION));
            }
        }

        ProtectionDomain domain =
            new ProtectionDomain(new CodeSource(codebase, null), perms);
        AccessControlContext acc =
            new AccessControlContext(new ProtectionDomain[] { domain });

        return acc;
    }

    public Thread getAppletHandlerThread() {
        return handler;
    }

    public int getAppletWidth() {
        return currentAppletSize.width;
    }

    public int getAppletHeight() {
        return currentAppletSize.height;
    }

    public static void changeFrameAppContext(Frame frame, AppContext newAppContext)
    {
        // Fixed #4754451: Applet can have methods running on main
        // thread event queue.
        //
        // The cause of this bug is that the frame of the applet
        // is created in main thread group. Thus, when certain
        // AWT/Swing events are generated, the events will be
        // dispatched through the wrong event dispatch thread.
        //
        // To fix this, we rearrange the AppContext with the frame,
        // so the proper event queue will be looked up.
        //
        // Swing also maintains a Frame list for the AppContext,
        // so we will have to rearrange it as well.
        //

        // Check if frame's AppContext has already been set properly
        AppContext oldAppContext = SunToolkit.targetToAppContext(frame);

        if (oldAppContext == newAppContext)
            return;


        // Synchronization on Frame.class is needed for locking the
        // critical section of the frame list in AppContext.
        //
        synchronized (Frame.class)
        {
            // Remove frame from the FrameList in wrong AppContext
            //
            {
                WeakReference weakRef = null;

                // Lookup current frame's AppContext
                //
                Vector frameList = (Vector)oldAppContext.get(Frame.class);
                if (frameList != null) {
                    for (Enumeration e = frameList.elements() ; e.hasMoreElements() ;) {
                        WeakReference ref = (WeakReference) e.nextElement();

                        if (ref.get() == frame)
                        {
                            weakRef = ref;
                            break;
                        }

                    }

                    // Remove frame from wrong AppContext
                    //
                    if (weakRef != null)
                        frameList.removeElement(weakRef);
                }
            }


            // Put the frame into the applet's AppContext map
            //
            SunToolkit.insertTargetMapping(frame, newAppContext);


            // Insert frame into the FrameList in the applet's AppContext map
            //
            {
                Vector frameList = (Vector)newAppContext.get(Frame.class);
                if (frameList == null) {
                    frameList = new Vector();
                    newAppContext.put(Frame.class, frameList);
                }
                frameList.addElement(new WeakReference(frame));
            }
        }
    }

    private static AppletMessageHandler amh = new AppletMessageHandler("appletpanel");
}