Source for java.awt.im.InputContext

   1: /* InputContext.java -- provides the context for text input
   2:    Copyright (C) 2002, 2003, 2004, 2005  Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package java.awt.im;
  40: 
  41: import gnu.java.util.EmptyEnumeration;
  42: 
  43: import java.awt.AWTEvent;
  44: import java.awt.AWTException;
  45: import java.awt.Component;
  46: import java.awt.im.spi.InputMethod;
  47: import java.awt.im.spi.InputMethodDescriptor;
  48: import java.io.BufferedReader;
  49: import java.io.IOException;
  50: import java.io.InputStreamReader;
  51: import java.net.URL;
  52: import java.text.AttributedCharacterIterator.Attribute;
  53: import java.util.ArrayList;
  54: import java.util.Enumeration;
  55: import java.util.HashMap;
  56: import java.util.Locale;
  57: 
  58: /**
  59:  * Provides a context for controlling input methods and keyboard layouts.
  60:  * This class provides the communication layer between the client component,
  61:  * and the various locale-dependent text entry input methods that can be used
  62:  * for the client. By default, there is one instance per Window, shared among
  63:  * all components, but this limits text entry to one component at a time.
  64:  * Thus, text components can create their own instance to allow text entry
  65:  * in multiple components at a time.
  66:  *
  67:  * <p>By using the interfaces of {@link java.awt.im.spi}, you can install
  68:  * extensions which allow additional input methods. Some of these may use
  69:  * platform native input methods, or keyboard layouts provided by the platform.
  70:  * Input methods are unavailable if none have been installed and the platform
  71:  * has no underlying native input methods. Extensions are installed as jar
  72:  * files, usually accessed in the default extension location or specified by
  73:  * the -extdir VM flag. The jar must contain a file named
  74:  * "META_INF/services/java.awt.im.spi.InputMethodDescriptor" which lists,
  75:  * one entry per line in UTF-8 encoding, each class in the jar that implements
  76:  * java.awt.im.spi.InputMethodDescriptor.
  77:  *
  78:  * @author Eric Blake (ebb9@email.byu.edu)
  79:  * @see Component#getInputContext()
  80:  * @see Component#enableInputMethods(boolean)
  81:  * @since 1.2
  82:  * @status updated to 1.4, but unverified
  83:  */
  84: public class InputContext
  85: {
  86:   /**
  87:    * The list of installed input method descriptors.
  88:    */
  89:   private static final ArrayList descriptors = new ArrayList();
  90:   static
  91:   {
  92:     Enumeration e;
  93:     try
  94:       {
  95:         e = ClassLoader.getSystemResources
  96:           ("META_INF/services/java.awt.im.spi.InputMethodDescriptor");
  97:       }
  98:     catch (IOException ex)
  99:       {
 100:         // XXX Should we do something else?
 101:         e = EmptyEnumeration.getInstance();
 102:       }
 103:     while (e.hasMoreElements())
 104:       {
 105:         URL url = (URL) e.nextElement();
 106:         BufferedReader in;
 107:         String line;
 108:         try
 109:           {
 110:             in = new BufferedReader
 111:               (new InputStreamReader(url.openConnection().getInputStream(),
 112:                                      "UTF-8"));
 113:             line = in.readLine().trim();
 114:           }
 115:         catch (IOException ignored)
 116:           {
 117:             continue;
 118:           }
 119:       outer:
 120:         while (line != null)
 121:           {
 122:             try
 123:               {
 124:                 if (line.charAt(0) != '#')
 125:                   {
 126:                     Class c = Class.forName(line);
 127:                     descriptors.add((InputMethodDescriptor) c.newInstance());
 128:                   }
 129:                 line = in.readLine().trim();
 130:               }
 131:             catch (IOException ex)
 132:               {
 133:                 continue outer;
 134:               }
 135:             catch (Exception ignored)
 136:               {
 137:               }
 138:           }
 139:       }
 140:   }
 141: 
 142:   /** The current input method; null if no input methods are installed. */
 143:   private InputMethod im;
 144: 
 145:   /** Map of locales to the most recently selected input method. */
 146:   private final HashMap recent = new HashMap();
 147: 
 148:   /** The list of acceptable character subsets. */
 149:   private Character.Subset[] subsets;
 150: 
 151:   /**
 152:    * Construct an InputContext. This is protected, so clients must use
 153:    * {@link #getInstance()} instead.
 154:    */
 155:   protected InputContext()
 156:   {
 157:   }
 158: 
 159:   /**
 160:    * Returns a new InputContext.
 161:    *
 162:    * @return a new instance, initialized to the default locale if available
 163:    */
 164:   public static InputContext getInstance()
 165:   {
 166:     InputContext ic = new InputContext();
 167:     ic.selectInputMethod(Locale.getDefault());
 168:     return ic;
 169:   }
 170: 
 171:   /**
 172:    * Attempts to select an input method or keyboard layout which supports the
 173:    * given locale. This returns true if a locale is available and was selected.
 174:    * The following steps are taken in choosing an input method:<ul>
 175:    * <li>If the currently selected input method or keyboard layout supports
 176:    * the requested locale, it remains selected.</li>
 177:    * <li>If there is no input method or keyboard layout available that
 178:    * supports the requested locale, the current input method or keyboard
 179:    * layout remains selected.</li>
 180:    * <li>If the user has previously selected an input method or keyboard
 181:    * layout for the requested locale from the user interface, then the most
 182:    * recently selected such input method or keyboard layout is reselected.</li>
 183:    * <li>Otherwise, an input method or keyboard layout that supports the
 184:    * requested locale is selected in an implementation dependent way. This
 185:    * implementation chooses the first input method which supports the requested
 186:    * locale based on the InputMethodDescriptors loaded from the extensions
 187:    * installed on the CLASSPATH.</li>
 188:    * </ul>
 189:    *
 190:    * <p>Before switching away from an input method, any currently uncommitted
 191:    * text is committed. Not all host operating systems provide API to
 192:    * determine the locale of the currently selected native input method or
 193:    * keyboard layout, and to select a native input method or keyboard layout
 194:    * by locale. For host operating systems that don't provide such API,
 195:    * selectInputMethod assumes that native input methods or keyboard layouts
 196:    * provided by the host operating system support only the system's default
 197:    * locale.
 198:    *
 199:    * <p>An example of where this may be called is in a multi-language document,
 200:    * when moving the insertion point between sections of different locale, so
 201:    * that the user may use the input method appropriate to that section of the
 202:    * document.
 203:    *
 204:    * @param locale the desired new locale
 205:    * @return true if the new locale is active
 206:    * @throws NullPointerException if locale is null
 207:    */
 208:   public boolean selectInputMethod(Locale locale)
 209:   {
 210:     if (im != null && im.setLocale(locale))
 211:       {
 212:         recent.put(locale, im);
 213:         return true;
 214:       }
 215:     InputMethod next = (InputMethod) recent.get(locale);
 216:   outer:
 217:     if (next != null)
 218:       for (int i = 0, limit = descriptors.size(); i < limit; i++)
 219:         {
 220:           InputMethodDescriptor d = (InputMethodDescriptor) descriptors.get(i);
 221:           Locale[] list;
 222:           try
 223:             {
 224:               list = d.getAvailableLocales();
 225:             }
 226:           catch (AWTException ignored)
 227:             {
 228:               continue;
 229:             }
 230:           for (int j = list.length; --j >= 0; )
 231:             if (locale.equals(list[j]))
 232:               {
 233:                 try
 234:                   {
 235:                     next = d.createInputMethod();
 236:                     recent.put(locale, next);
 237:                   }
 238:                 catch (Exception ignored)
 239:                   {
 240:                     continue;
 241:                   }
 242:               }
 243:         }
 244:     if (next == null)
 245:       return false;
 246:     // XXX I'm not sure if this does all the necessary steps in the switch.
 247:     if (im != null)
 248:       {
 249:         try
 250:           {
 251:             next.setCompositionEnabled(im.isCompositionEnabled());
 252:           }
 253:         catch (UnsupportedOperationException ignored)
 254:           {
 255:           }
 256:         im.endComposition();
 257:         im.deactivate(false);
 258:         im.hideWindows();
 259:       }
 260:     im = next;
 261:     im.setLocale(locale);
 262:     im.setCharacterSubsets(subsets);
 263:     return true;
 264:   }
 265: 
 266:   /**
 267:    * Returns the current locale of the current input method or keyboard
 268:    * layout. Returns null if the input context does not have a current input
 269:    * method or keyboard layout or if the current input method's
 270:    * {@link InputMethod#getLocale()} method returns null. Not all host
 271:    * operating systems provide API to determine the locale of the currently
 272:    * selected native input method or keyboard layout. For host operating
 273:    * systems that don't provide such API, getLocale assumes that the current
 274:    * locale of all native input methods or keyboard layouts provided by the
 275:    * host operating system is the system's default locale.
 276:    *
 277:    * @return the locale of the current input method, or null
 278:    * @since 1.3
 279:    */
 280:   public Locale getLocale()
 281:   {
 282:     return im == null ? null : im.getLocale();
 283:   }
 284: 
 285:   /**
 286:    * Sets the subsets of Unicode characters allowed to be input by the current
 287:    * input method, as well as subsequent input methods. The value of null
 288:    * implies all characters are legal. Applications should not rely on this
 289:    * behavior, since native host input methods may not allow restrictions.
 290:    * If no current input method is available, this has no immediate effect.
 291:    *
 292:    * @param subsets the set of Unicode subsets to accept, or null
 293:    */
 294:   public void setCharacterSubsets(Character.Subset[] subsets)
 295:   {
 296:     this.subsets = subsets;
 297:     if (im != null)
 298:       im.setCharacterSubsets(subsets);
 299:   }
 300: 
 301:   /**
 302:    * Changes the enabled status of the current input method. An input method
 303:    * that is enabled for composition interprets incoming events for both
 304:    * composition and control purposes, while a disabled input method only
 305:    * interprets control commands (including commands to enable itself).
 306:    *
 307:    * @param enable whether to enable the input method
 308:    * @throws UnsupportedOperationException if there is no current input method,
 309:    *         or the input method does not support enabling
 310:    * @see #isCompositionEnabled()
 311:    * @since 1.3
 312:    */
 313:   public void setCompositionEnabled(boolean enable)
 314:   {
 315:     if (im == null)
 316:       throw new UnsupportedOperationException();
 317:     im.setCompositionEnabled(enable);
 318:   }
 319: 
 320:   /**
 321:    * Find out if the current input method is enabled.
 322:    *
 323:    * @return true if the current input method is enabled
 324:    * @throws UnsupportedOperationException if there is no current input method,
 325:    *         or the input method does not support enabling
 326:    * @see #setCompositionEnabled(boolean)
 327:    * @since 1.3
 328:    */
 329:   public boolean isCompositionEnabled()
 330:   {
 331:     if (im == null)
 332:       throw new UnsupportedOperationException();
 333:     return im.isCompositionEnabled();
 334:   }
 335: 
 336:   /**
 337:    * Starts a reconversion operation in the current input method. The input
 338:    * method gets the text to reconvert from the client component, using
 339:    * {@link InputMethodRequests#getSelectedText(Attribute[])}. Then the
 340:    * composed and committed text produced by the operation is sent back to
 341:    * the client using a sequence of InputMethodRequests.
 342:    *
 343:    * @throws UnsupportedOperationException if there is no current input method,
 344:    *         or the input method does not support reconversion
 345:    * @since 1.3
 346:    */
 347:   public void reconvert()
 348:   {
 349:     if (im == null)
 350:       throw new UnsupportedOperationException();
 351:     im.reconvert();
 352:   }
 353: 
 354:   /**
 355:    * Dispatches an event to the current input method. This is called
 356:    * automatically by AWT. If no input method is available, then the event
 357:    * will never be consumed.
 358:    *
 359:    * @param event the event to dispatch
 360:    * @throws NullPointerException if event is null
 361:    */
 362:   public void dispatchEvent(AWTEvent event)
 363:   {
 364:     if (im != null)
 365:       im.dispatchEvent(event);
 366:   }
 367: 
 368:   /**
 369:    * Notifies the input context that a client component has been removed from
 370:    * its containment hierarchy, or that input method support has been disabled
 371:    * for the component. This method is usually called from the client
 372:    * component's {@link Component#removeNotify()} method. Potentially pending
 373:    * input from input methods for this component is discarded. If no input
 374:    * methods are available, then this method has no effect.
 375:    *
 376:    * @param client the client component
 377:    * @throws NullPointerException if client is null
 378:    */
 379:   public void removeNotify(Component client)
 380:   {
 381:     // XXX What to do with client information?
 382:     if (im != null)
 383:       {
 384:         im.deactivate(false);
 385:         im.removeNotify();
 386:       }
 387:   }
 388: 
 389:   /**
 390:    * Ends any input composition that may currently be going on in this
 391:    * context. Depending on the platform and possibly user preferences, this
 392:    * may commit or delete uncommitted text. Any changes to the text are
 393:    * communicated to the active component using an input method event. If no
 394:    * input methods are available, then this method has no effect. This may
 395:    * be called for a variety of reasons, such as when the user moves the
 396:    * insertion point in the client text outside the range of the composed text,
 397:    * or when text is saved to file.
 398:    */
 399:   public void endComposition()
 400:   {
 401:     if (im != null)
 402:       im.endComposition();
 403:   }
 404: 
 405:   /**
 406:    * Disposes of the input context and release the resources used by it.
 407:    * Called automatically by AWT for the default input context of each
 408:    * Window. If no input methods are available, then this method has no
 409:    * effect.
 410:    */
 411:   public void dispose()
 412:   {
 413:     if (im != null)
 414:       {
 415:         im.deactivate(false);
 416:         im.dispose();
 417:       }
 418:   }
 419: 
 420:   /**
 421:    * Returns a control object from the current input method, or null. A
 422:    * control object provides implementation-dependent methods that control
 423:    * the behavior of the input method or obtain information from the input
 424:    * method. Clients have to compare the result against known input method
 425:    * control object types. If no input methods are available or the current
 426:    * input method does not provide an input method control object, then null
 427:    * is returned. 
 428:    *
 429:    * @return the control object, or null
 430:    */
 431:   public Object getInputMethodControlObject()
 432:   {
 433:     return im == null ? null : im.getControlObject();
 434:   }
 435: } // class InputContext