001/* Applet.java -- Java base applet class
002   Copyright (C) 1999, 2002, 2004, 2005  Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package java.applet;
040
041import java.awt.Component;
042import java.awt.Dimension;
043import java.awt.GraphicsEnvironment;
044import java.awt.HeadlessException;
045import java.awt.Image;
046import java.awt.Panel;
047import java.io.IOException;
048import java.io.ObjectInputStream;
049import java.net.MalformedURLException;
050import java.net.URL;
051import java.util.Locale;
052
053import javax.accessibility.AccessibleContext;
054import javax.accessibility.AccessibleRole;
055import javax.accessibility.AccessibleState;
056import javax.accessibility.AccessibleStateSet;
057import javax.sound.sampled.AudioSystem;
058import javax.sound.sampled.Clip;
059import javax.sound.sampled.LineUnavailableException;
060import javax.sound.sampled.UnsupportedAudioFileException;
061
062/**
063 * This is the base applet class.  An applet is a Java program that
064 * runs inside a web browser or other applet viewer in a restricted
065 * environment.
066 *
067 * <p>To be useful, a subclass should override at least start(). Also useful
068 * are init, stop, and destroy for control purposes, and getAppletInfo and
069 * getParameterInfo for descriptive purposes.
070 *
071 * @author Aaron M. Renn (arenn@urbanophile.com)
072 * @author Eric Blake (ebb9@email.byu.edu)
073 * @since 1.0
074 * @status updated to 1.4
075 */
076public class Applet extends Panel
077{
078  /**
079   * Compatible with JDK 1.0+.
080   */
081  private static final long serialVersionUID = -5836846270535785031L;
082
083  /** The applet stub for this applet. */
084  private transient AppletStub stub;
085
086  /** Some applets call setSize in their constructors.  In that case,
087      these fields are used to store width and height values until a
088      stub is set. */
089  private transient int width;
090  private transient int height;
091
092  /**
093   * The accessibility context for this applet.
094   *
095   * @serial the accessibleContext for this
096   * @since 1.2
097   */
098  private AccessibleContext accessibleContext;
099
100  /**
101   * Default constructor for subclasses.
102   *
103   * @throws HeadlessException if in a headless environment
104   */
105  public Applet()
106  {
107    if (GraphicsEnvironment.isHeadless())
108      throw new HeadlessException();
109  }
110
111  /**
112   * The browser calls this method to set the applet's stub, which is the
113   * low level interface to the browser. Manually setting this to null is
114   * asking for problems down the road.
115   *
116   * @param stub the applet stub for this applet
117   */
118  public final void setStub(AppletStub stub)
119  {
120    this.stub = stub;
121
122    if (width != 0 && height != 0)
123      stub.appletResize (width, height);
124  }
125
126  /**
127   * Tests whether or not this applet is currently active. An applet is active
128   * just before the browser invokes start(), and becomes inactive just
129   * before the browser invokes stop().
130   *
131   * @return <code>true</code> if this applet is active
132   */
133  public boolean isActive()
134  {
135    return stub.isActive();
136  }
137
138  /**
139   * Returns the basename URL of the document this applet is embedded in. This
140   * is everything up to the final '/'.
141   *
142   * @return the URL of the document this applet is embedded in
143   * @see #getCodeBase()
144   */
145  public URL getDocumentBase()
146  {
147    return stub.getDocumentBase();
148  }
149
150  /**
151   * Returns the URL of the code base for this applet.
152   *
153   * @return the URL of the code base for this applet
154   */
155  public URL getCodeBase()
156  {
157    return stub.getCodeBase();
158  }
159
160  /**
161   * Returns the value of the specified parameter that was specified in
162   * the <code>&lt;APPLET&gt;</code> tag for this applet.
163   *
164   * @param name the parameter name
165   * @return the parameter value, or null if the parameter does not exist
166   * @throws NullPointerException if name is null
167   */
168  public String getParameter(String name)
169  {
170    return stub.getParameter(name);
171  }
172
173  /**
174   * Returns the applet context for this applet.
175   *
176   * @return the applet context for this applet
177   */
178  public AppletContext getAppletContext()
179  {
180    return stub.getAppletContext();
181  }
182
183  /**
184   * Requests that the applet window for this applet be resized.
185   *
186   * @param width the new width in pixels
187   * @param height the new height in pixels
188   */
189  public void resize(int width, int height)
190  {
191    if (stub == null)
192      {
193        this.width = width;
194        this.height = height;
195      }
196    else
197      stub.appletResize(width, height);
198  }
199
200  /**
201   * Requests that the applet window for this applet be resized.
202   *
203   * @param dim the requested dimensions
204   * @throws NullPointerException if dim is null
205   */
206  public void resize(Dimension dim)
207  {
208    resize(dim.width, dim.height);
209  }
210
211  /**
212   * Displays the specified message in the status window if that window
213   * exists.
214   *
215   * @param message the status message, may be null
216   */
217  public void showStatus(String message)
218  {
219    getAppletContext().showStatus(message);
220  }
221
222  /**
223   * Returns an image from the specified URL.  Note that the image is not
224   * actually retrieved until the applet attempts to display it, so this
225   * method returns immediately.
226   *
227   * @param url the URL of the image
228   * @return the retrieved image
229   * @throws NullPointerException if url is null
230   */
231  public Image getImage(URL url)
232  {
233    return getAppletContext().getImage(url);
234  }
235
236  /**
237   * Returns an image from the specified absolute URL, and relative path
238   * from that URL.  Note that the image is not actually retrieved until the
239   * applet attempts to display it, so this method returns immediately.
240   * This calls <code>getImage(new URL(url, name))</code>, but if building
241   * the new URL fails, this returns null.
242   *
243   * @param url the base URL of the image
244   * @param name the name of the image relative to the URL
245   * @return the retrieved image, or null on failure
246   * @see #getImage(URL)
247   */
248  public Image getImage(URL url, String name)
249  {
250    try
251      {
252        return getImage(new URL(url, name));
253      }
254    catch (MalformedURLException e)
255      {
256        return null;
257      }
258  }
259
260  /**
261   * Returns an audio clip from the specified URL. This clip is not tied to
262   * any particular applet.
263   *
264   * @param url the URL of the audio clip
265   * @return the retrieved audio clip
266   * @throws NullPointerException if url is null
267   * @see #getAudioClip(URL)
268   * @since 1.2
269   */
270  public static final AudioClip newAudioClip(URL url)
271  {
272    return new URLAudioClip(url);
273  }
274
275  /**
276   * Returns an audio clip from the specified URL. Note that the clip is not
277   * actually retrieved until the applet attempts to play it, so this method
278   * returns immediately.
279   *
280   * @param url the URL of the audio clip
281   * @return the retrieved audio clip
282   * @throws NullPointerException if url is null
283   */
284  public AudioClip getAudioClip(URL url)
285  {
286    return getAppletContext().getAudioClip(url);
287  }
288
289  /**
290   * Returns an audio clip from the specified absolute URL, and relative path
291   * from that URL.  Note that the clip is not actually retrieved until the
292   * applet attempts to play it, so this method returns immediately. This
293   * calls <code>getAudioClip(new URL(url, name))</code>, but if building
294   * the new URL fails, this returns null.
295   *
296   * @param url the base URL of the audio clip
297   * @param name the name of the clip relative to the URL
298   * @return the retrieved audio clip, or null on failure
299   * @see #getAudioClip(URL)
300   */
301  public AudioClip getAudioClip(URL url, String name)
302  {
303    try
304      {
305        return getAudioClip(new URL(url, name));
306      }
307    catch (MalformedURLException e)
308      {
309        return null;
310      }
311  }
312
313  /**
314   * Returns a descriptive string with applet defined information.  The
315   * implementation in this class returns <code>null</code>, so subclasses
316   * must override to return information.
317   *
318   * @return a string describing the author, version, and applet copyright
319   */
320  public String getAppletInfo()
321  {
322    return null;
323  }
324
325  /**
326   * Returns the locale for this applet, if it has been set.  If no applet
327   * specific locale has been set, the default locale is returned.
328   *
329   * @return the locale for this applet
330   * @see Component#setLocale(Locale)
331   * @since 1.1
332   */
333  public Locale getLocale()
334  {
335    return super.getLocale();
336  }
337
338  /**
339   * Returns a list of parameters this applet supports.  Each element of
340   * the outer array is an array of three strings with the name of the
341   * parameter, the data type or valid values, and a description.  This
342   * method is optional and the default implementation returns null.
343   *
344   * @return the list of parameters supported by this applet
345   */
346  public String[][] getParameterInfo()
347  {
348    return null;
349  }
350
351  /**
352   * Loads and plays the audio clip pointed to by the specified URL. This does
353   * nothing if the URL does not point to a valid audio clip.
354   *
355   * @param url the URL of the audio clip
356   * @throws NullPointerException if url is null
357   * @see #getAudioClip(URL)
358   */
359  public void play(URL url)
360  {
361    AudioClip ac = getAudioClip(url);
362    try
363      {
364        ac.play();
365      }
366    catch (Exception ignored)
367      {
368      }
369  }
370
371  /**
372   * Loads and plays the audio clip pointed to by the specified absolute URL,
373   * and relative path from that URL. This does nothing if the URL cannot be
374   * constructed, or if it does not point to a valid audio clip.
375   *
376   * @param url the base URL of the audio clip
377   * @param name the name of the audio clip relative to the URL
378   * @see #getAudioClip(URL, String)
379   * @see #play(URL)
380   */
381  public void play(URL url, String name)
382  {
383    try
384      {
385        getAudioClip(url, name).play();
386      }
387    catch (Exception ignored)
388      {
389      }
390  }
391
392  /**
393   * This method is called when the applet is first loaded, before start().
394   * The default implementation does nothing; override to do any one-time
395   * initialization.
396   *
397   * @see #start()
398   * @see #stop()
399   * @see #destroy()
400   */
401  public void init()
402  {
403  }
404
405  /**
406   * This method is called when the applet should start running.  This is
407   * normally each time a web page containing it is loaded.  The default
408   * implemention does nothing; override for your applet to be useful.
409   *
410   * @see #init()
411   * @see #stop()
412   * @see #destroy()
413   */
414  public void start()
415  {
416  }
417
418  /**
419   * This method is called when the applet should stop running.  This is
420   * normally when the next web page is loaded.  The default implementation
421   * does nothing; override for your applet to stop using resources when
422   * it is no longer visible, but may be restarted soon.
423   *
424   * @see #init()
425   * @see #start()
426   * @see #destroy()
427   */
428  public void stop()
429  {
430  }
431
432  /**
433   * This method is called when the applet is being unloaded.  The default
434   * implementation does nothing; override for your applet to clean up
435   * resources on exit.
436   *
437   * @see #init()
438   * @see #start()
439   * @see #stop()
440   */
441  public void destroy()
442  {
443  }
444
445  /**
446   * Gets the AccessibleContext associated with this applet, creating one if
447   * necessary. This always returns an instance of {@link AccessibleApplet}.
448   *
449   * @return the accessibility context of this applet
450   * @since 1.3
451   */
452  public AccessibleContext getAccessibleContext()
453  {
454    if (accessibleContext == null)
455      accessibleContext = new AccessibleApplet();
456    return accessibleContext;
457  }
458
459  /**
460   * Read an applet from an object stream. This checks for a headless
461   * environment, then does the normal read.
462   *
463   * @param s the stream to read from
464   * @throws ClassNotFoundException if a class is not found
465   * @throws IOException if deserialization fails
466   * @throws HeadlessException if this is a headless environment
467   * @see GraphicsEnvironment#isHeadless()
468   * @since 1.4
469   */
470  private void readObject(ObjectInputStream s)
471    throws ClassNotFoundException, IOException
472  {
473    if (GraphicsEnvironment.isHeadless())
474      throw new HeadlessException();
475    s.defaultReadObject();
476  }
477
478  /**
479   * This class provides accessibility support for Applets, and is the
480   * runtime type returned by {@link #getAccessibleContext()}.
481   *
482   * @author Eric Blake (ebb9@email.byu.edu)
483   * @since 1.3
484   */
485  protected class AccessibleApplet extends AccessibleAWTPanel
486  {
487    /**
488     * Compatible with JDK 1.4+.
489     */
490    private static final long serialVersionUID = 8127374778187708896L;
491
492    /**
493     * The default constructor.
494     */
495    protected AccessibleApplet()
496    {
497    }
498
499    /**
500     * Get the role of this accessible object, a frame.
501     *
502     * @return the role of the object
503     * @see AccessibleRole#FRAME
504     */
505    public AccessibleRole getAccessibleRole()
506    {
507      return AccessibleRole.FRAME;
508    }
509
510    /**
511     * Get the state set of this accessible object. In addition to the default
512     * states of a Component, the applet can also be active.
513     *
514     * @return the role of the object
515     * @see AccessibleState
516     */
517    public AccessibleStateSet getAccessibleStateSet()
518    {
519      AccessibleStateSet s = super.getAccessibleStateSet();
520      if (isActive())
521        s.add(AccessibleState.ACTIVE);
522      return s;
523    }
524  } // class AccessibleApplet
525
526  private static class URLAudioClip implements AudioClip
527  {
528    // The URL we will try to play.
529    // This is null if we have already tried to create an
530    // audio input stream from this URL.
531    private URL url;
532
533    // The real audio clip.  This is null before the URL is read,
534    // and might be null afterward if we were unable to read the URL
535    // for some reason.
536    private Clip clip;
537    
538    public URLAudioClip(URL url)
539    {
540      this.url = url;
541    }
542
543    private synchronized Clip getClip()
544    {
545      if (url == null)
546        return clip;
547      try
548        {
549          clip = AudioSystem.getClip();
550          clip.open(AudioSystem.getAudioInputStream(url));
551        }
552      catch (LineUnavailableException _)
553        {
554          // Ignore.
555        }
556      catch (IOException _)
557        {
558          // Ignore.
559        }
560      catch (UnsupportedAudioFileException _)
561        {
562          // Ignore.
563        }
564      url = null;
565      return clip;
566    }
567
568    public void loop()
569    {
570      Clip myclip = getClip();
571      if (myclip != null)
572        myclip.loop(Clip.LOOP_CONTINUOUSLY);
573    }
574
575    public void play()
576    {
577      Clip myclip = getClip();
578      if (myclip != null)
579        myclip.start();
580    }
581
582    public void stop()
583    {
584      Clip myclip = getClip();
585      if (myclip != null)
586        {
587          myclip.stop();
588          myclip.setFramePosition(0);
589        }
590    }
591  }
592} // class Applet