/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package java.applet;

import java.awt.*;

import java.awt.image.ColorModel;

import java.io.IOException;

import java.io.ObjectInputStream;

import java.net.URL;

import java.net.MalformedURLException;

import java.util.Hashtable;

import java.util.Locale;

import javax.accessibility.*;

/**

 * An applet is a small program that is intended not to be run on

 * its own, but rather to be embedded inside another application.

 * <p>

 * The <code>Applet</code> class must be the superclass of any

 * applet that is to be embedded in a Web page or viewed by the Java

 * Applet Viewer. The <code>Applet</code> class provides a standard

 * interface between applets and their environment.

 *

 * @author      Arthur van Hoff

 * @author      Chris Warth

 * @since       JDK1.0

 */

public class Applet extends Panel {

    /**

     * Constructs a new Applet.

     * <p>

     * Note: Many methods in <code>java.applet.Applet</code>

     * may be invoked by the applet only after the applet is

     * fully constructed; applet should avoid calling methods

     * in <code>java.applet.Applet</code> in the constructor.

     *

     * @exception HeadlessException if GraphicsEnvironment.isHeadless()

     * returns true.

     * @see java.awt.GraphicsEnvironment#isHeadless

     * @since 1.4

     */

    public Applet() throws HeadlessException {

        if (GraphicsEnvironment.isHeadless()) {

            throw new HeadlessException();

        }

    }

    /**

     * Applets can be serialized but the following conventions MUST be followed:

     *

     * Before Serialization:

     * An applet must be in STOPPED state.

     *

     * After Deserialization:

     * The applet will be restored in STOPPED state (and most clients will

     * likely move it into RUNNING state).

     * The stub field will be restored by the reader.

     */

    transient private AppletStub stub;

    /* version ID for serialized form. */

    private static final long serialVersionUID = -5836846270535785031L;

    /**

     * Read an applet from an object input stream.

     * @exception HeadlessException if

     * <code>GraphicsEnvironment.isHeadless()</code> returns

     * <code>true</code>

     * @serial

     * @see java.awt.GraphicsEnvironment#isHeadless

     * @since 1.4

     */

    private void readObject(ObjectInputStream s)

        throws ClassNotFoundException, IOException, HeadlessException {

        if (GraphicsEnvironment.isHeadless()) {

            throw new HeadlessException();

        }

        s.defaultReadObject();

    }

    /**

     * Sets this applet's stub. This is done automatically by the system.

     * <p>If there is a security manager, its <code> checkPermission </code>

     * method is called with the

     * <code>AWTPermission("setAppletStub")</code>

     * permission if a stub has already been set.

     * @param   stub   the new stub.

     * @exception SecurityException if the caller cannot set the stub

     */

    public final void setStub(AppletStub stub) {

        if (this.stub != null) {

            SecurityManager s = System.getSecurityManager();

            if (s != null) {

                s.checkPermission(new AWTPermission("setAppletStub"));

            }

        }

        this.stub = stub;

    }

    /**

     * Determines if this applet is active. An applet is marked active

     * just before its <code>start</code> method is called. It becomes

     * inactive just before its <code>stop</code> method is called.

     *

     * @return  <code>true</code> if the applet is active;

     *          <code>false</code> otherwise.

     * @see     java.applet.Applet#start()

     * @see     java.applet.Applet#stop()

     */

    public boolean isActive() {

        if (stub != null) {

            return stub.isActive();

        } else {        // If stub field not filled in, applet never active

            return false;

        }

    }

    /**

     * Gets the URL of the document in which this applet is embedded.

     * For example, suppose an applet is contained

     * within the document:

     * <blockquote><pre>

     *    http://java.sun.com/products/jdk/1.2/index.html

     * </pre></blockquote>

     * The document base is:

     * <blockquote><pre>

     *    http://java.sun.com/products/jdk/1.2/index.html

     * </pre></blockquote>

     *

     * @return  the {@link java.net.URL} of the document that contains this

     *          applet.

     * @see     java.applet.Applet#getCodeBase()

     */

    public URL getDocumentBase() {

        return stub.getDocumentBase();

    }

    /**

     * Gets the base URL. This is the URL of the directory which contains this applet.

     *

     * @return  the base {@link java.net.URL} of

     *          the directory which contains this applet.

     * @see     java.applet.Applet#getDocumentBase()

     */

    public URL getCodeBase() {

        return stub.getCodeBase();

    }

    /**

     * Returns the value of the named parameter in the HTML tag. For

     * example, if this applet is specified as

     * <blockquote><pre>

     * <applet code="Clock" width=50 height=50>

     * <param name=Color value="blue">

     * </applet>

     * </pre></blockquote>

     * <p>

     * then a call to <code>getParameter("Color")</code> returns the

     * value <code>"blue"</code>.

     * <p>

     * The <code>name</code> argument is case insensitive.

     *

     * @param   name   a parameter name.

     * @return  the value of the named parameter,

     *          or <code>null</code> if not set.

     */

     public String getParameter(String name) {

         return stub.getParameter(name);

     }

    /**

     * Determines this applet's context, which allows the applet to

     * query and affect the environment in which it runs.

     * <p>

     * This environment of an applet represents the document that

     * contains the applet.

     *

     * @return  the applet's context.

     */

    public AppletContext getAppletContext() {

        return stub.getAppletContext();

    }

    /**

     * Requests that this applet be resized.

     *

     * @param   width    the new requested width for the applet.

     * @param   height   the new requested height for the applet.

     */

    @SuppressWarnings("deprecation")

    public void resize(int width, int height) {

        Dimension d = size();

        if ((d.width != width) || (d.height != height)) {

            super.resize(width, height);

            if (stub != null) {

                stub.appletResize(width, height);

            }

        }

    }

    /**

     * Requests that this applet be resized.

     *

     * @param   d   an object giving the new width and height.

     */

    @SuppressWarnings("deprecation")

    public void resize(Dimension d) {

        resize(d.width, d.height);

    }

    /**

     * Indicates if this container is a validate root.

     * <p>

     * {@code Applet} objects are the validate roots, and, therefore, they

     * override this method to return {@code true}.

     *

     * @return {@code true}

     * @since 1.7

     * @see java.awt.Container#isValidateRoot

     */

    @Override

    public boolean isValidateRoot() {

        return true;

    }

    /**

     * Requests that the argument string be displayed in the

     * "status window". Many browsers and applet viewers

     * provide such a window, where the application can inform users of

     * its current state.

     *

     * @param   msg   a string to display in the status window.

     */

    public void showStatus(String msg) {

        getAppletContext().showStatus(msg);

    }

    /**

     * Returns an <code>Image</code> object that can then be painted on

     * the screen. The <code>url</code> that is passed as an argument

     * must specify an absolute URL.

     * <p>

     * This method always returns immediately, whether or not the image

     * exists. When this applet attempts to draw the image on the screen,

     * the data will be loaded. The graphics primitives that draw the

     * image will incrementally paint on the screen.

     *

     * @param   url   an absolute URL giving the location of the image.

     * @return  the image at the specified URL.

     * @see     java.awt.Image

     */

    public Image getImage(URL url) {

        return getAppletContext().getImage(url);

    }

    /**

     * Returns an <code>Image</code> object that can then be painted on

     * the screen. The <code>url</code> argument must specify an absolute

     * URL. The <code>name</code> argument is a specifier that is

     * relative to the <code>url</code> argument.

     * <p>

     * This method always returns immediately, whether or not the image

     * exists. When this applet attempts to draw the image on the screen,

     * the data will be loaded. The graphics primitives that draw the

     * image will incrementally paint on the screen.

     *

     * @param   url    an absolute URL giving the base location of the image.

     * @param   name   the location of the image, relative to the

     *                 <code>url</code> argument.

     * @return  the image at the specified URL.

     * @see     java.awt.Image

     */

    public Image getImage(URL url, String name) {

        try {

            return getImage(new URL(url, name));

        } catch (MalformedURLException e) {

            return null;

        }

    }

    /**

     * Get an audio clip from the given URL.

     *

     * @param url points to the audio clip

     * @return the audio clip at the specified URL.

     *

     * @since       1.2

     */

    public final static AudioClip newAudioClip(URL url) {

        return new sun.applet.AppletAudioClip(url);

    }

    /**

     * Returns the <code>AudioClip</code> object specified by the

     * <code>URL</code> argument.

     * <p>

     * This method always returns immediately, whether or not the audio

     * clip exists. When this applet attempts to play the audio clip, the

     * data will be loaded.

     *

     * @param   url  an absolute URL giving the location of the audio clip.

     * @return  the audio clip at the specified URL.

     * @see     java.applet.AudioClip

     */

    public AudioClip getAudioClip(URL url) {

        return getAppletContext().getAudioClip(url);

    }

    /**

     * Returns the <code>AudioClip</code> object specified by the

     * <code>URL</code> and <code>name</code> arguments.

     * <p>

     * This method always returns immediately, whether or not the audio

     * clip exists. When this applet attempts to play the audio clip, the

     * data will be loaded.

     *

     * @param   url    an absolute URL giving the base location of the

     *                 audio clip.

     * @param   name   the location of the audio clip, relative to the

     *                 <code>url</code> argument.

     * @return  the audio clip at the specified URL.

     * @see     java.applet.AudioClip

     */

    public AudioClip getAudioClip(URL url, String name) {

        try {

            return getAudioClip(new URL(url, name));

        } catch (MalformedURLException e) {

            return null;

        }

    }

    /**

     * Returns information about this applet. An applet should override

     * this method to return a <code>String</code> containing information

     * about the author, version, and copyright of the applet.

     * <p>

     * The implementation of this method provided by the

     * <code>Applet</code> class returns <code>null</code>.

     *

     * @return  a string containing information about the author, version, and

     *          copyright of the applet.

     */

    public String getAppletInfo() {

        return null;

    }

    /**

     * Gets the locale of the applet. It allows the applet

     * to maintain its own locale separated from the locale

     * of the browser or appletviewer.

     *

     * @return  the locale of the applet; if no locale has

     *          been set, the default locale is returned.

     * @since   JDK1.1

     */

    public Locale getLocale() {

      Locale locale = super.getLocale();

      if (locale == null) {

        return Locale.getDefault();

      }

      return locale;

    }

    /**

     * Returns information about the parameters that are understood by

     * this applet. An applet should override this method to return an

     * array of <code>Strings</code> describing these parameters.

     * <p>

     * Each element of the array should be a set of three

     * <code>Strings</code> containing the name, the type, and a

     * description. For example:

     * <p><blockquote><pre>

     * String pinfo[][] = {

     *   {"fps",    "1-10",    "frames per second"},

     *   {"repeat", "boolean", "repeat image loop"},

     *   {"imgs",   "url",     "images directory"}

     * };

     * </pre></blockquote>

     * <p>

     * The implementation of this method provided by the

     * <code>Applet</code> class returns <code>null</code>.

     *

     * @return  an array describing the parameters this applet looks for.

     */

    public String[][] getParameterInfo() {

        return null;

    }

    /**

     * Plays the audio clip at the specified absolute URL. Nothing

     * happens if the audio clip cannot be found.

     *

     * @param   url   an absolute URL giving the location of the audio clip.

     */

    public void play(URL url) {

        AudioClip clip = getAudioClip(url);

        if (clip != null) {

            clip.play();

        }

    }

    /**

     * Plays the audio clip given the URL and a specifier that is

     * relative to it. Nothing happens if the audio clip cannot be found.

     *

     * @param   url    an absolute URL giving the base location of the

     *                 audio clip.

     * @param   name   the location of the audio clip, relative to the

     *                 <code>url</code> argument.

     */

    public void play(URL url, String name) {

        AudioClip clip = getAudioClip(url, name);

        if (clip != null) {

            clip.play();

        }

    }

    /**

     * Called by the browser or applet viewer to inform

     * this applet that it has been loaded into the system. It is always

     * called before the first time that the <code>start</code> method is

     * called.

     * <p>

     * A subclass of <code>Applet</code> should override this method if

     * it has initialization to perform. For example, an applet with

     * threads would use the <code>init</code> method to create the

     * threads and the <code>destroy</code> method to kill them.

     * <p>

     * The implementation of this method provided by the

     * <code>Applet</code> class does nothing.

     *

     * @see     java.applet.Applet#destroy()

     * @see     java.applet.Applet#start()

     * @see     java.applet.Applet#stop()

     */

    public void init() {

    }

    /**

     * Called by the browser or applet viewer to inform

     * this applet that it should start its execution. It is called after

     * the <code>init</code> method and each time the applet is revisited

     * in a Web page.

     * <p>

     * A subclass of <code>Applet</code> should override this method if

     * it has any operation that it wants to perform each time the Web

     * page containing it is visited. For example, an applet with

     * animation might want to use the <code>start</code> method to

     * resume animation, and the <code>stop</code> method to suspend the

     * animation.

     * <p>

     * Note: some methods, such as <code>getLocationOnScreen</code>, can only

     * provide meaningful results if the applet is showing.  Because

     * <code>isShowing</code> returns <code>false</code> when the applet's

     * <code>start</code> is first called, methods requiring

     * <code>isShowing</code> to return <code>true</code> should be called from

     * a <code>ComponentListener</code>.

     * <p>

     * The implementation of this method provided by the

     * <code>Applet</code> class does nothing.

     *

     * @see     java.applet.Applet#destroy()

     * @see     java.applet.Applet#init()

     * @see     java.applet.Applet#stop()

     * @see     java.awt.Component#isShowing()

     * @see     java.awt.event.ComponentListener#componentShown(java.awt.event.ComponentEvent)

     */

    public void start() {

    }

    /**

     * Called by the browser or applet viewer to inform

     * this applet that it should stop its execution. It is called when

     * the Web page that contains this applet has been replaced by

     * another page, and also just before the applet is to be destroyed.

     * <p>

     * A subclass of <code>Applet</code> should override this method if

     * it has any operation that it wants to perform each time the Web

     * page containing it is no longer visible. For example, an applet

     * with animation might want to use the <code>start</code> method to

     * resume animation, and the <code>stop</code> method to suspend the

     * animation.

     * <p>

     * The implementation of this method provided by the

     * <code>Applet</code> class does nothing.

     *

     * @see     java.applet.Applet#destroy()

     * @see     java.applet.Applet#init()

     */

    public void stop() {

    }

    /**

     * Called by the browser or applet viewer to inform

     * this applet that it is being reclaimed and that it should destroy

     * any resources that it has allocated. The <code>stop</code> method

     * will always be called before <code>destroy</code>.

     * <p>

     * A subclass of <code>Applet</code> should override this method if

     * it has any operation that it wants to perform before it is

     * destroyed. For example, an applet with threads would use the

     * <code>init</code> method to create the threads and the

     * <code>destroy</code> method to kill them.