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