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:  * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
  80:  * @see Component#getInputContext()
  81:  * @see Component#enableInputMethods(boolean)
  82:  * @since 1.2
  83:  * @status updated to 1.4, but unverified
  84:  */
  85: public class InputContext
  86: {
  87:   /**
  88:    * The list of installed input method descriptors.
  89:    */
  90:   private static final ArrayList<InputMethodDescriptor> descriptors
  91:     = new ArrayList<InputMethodDescriptor>();
  92: 
  93:   static
  94:   {
  95:     Enumeration e;
  96:     try
  97:       {
  98:         e = ClassLoader.getSystemResources
  99:           ("META_INF/services/java.awt.im.spi.InputMethodDescriptor");
 100:       }
 101:     catch (IOException ex)
 102:       {
 103:         // XXX Should we do something else?
 104:         e = EmptyEnumeration.getInstance();
 105:       }
 106:     while (e.hasMoreElements())
 107:       {
 108:         URL url = (URL) e.nextElement();
 109:         BufferedReader in;
 110:         String line;
 111:         try
 112:           {
 113:             in = new BufferedReader
 114:               (new InputStreamReader(url.openConnection().getInputStream(),
 115:                                      "UTF-8"));
 116:             line = in.readLine().trim();
 117:           }
 118:         catch (IOException ignored)
 119:           {
 120:             continue;
 121:           }
 122:       outer:
 123:         while (line != null)
 124:           {
 125:             try
 126:               {
 127:                 if (line.charAt(0) != '#')
 128:                   {
 129:                     Class<?> c = Class.forName(line);
 130:                     descriptors.add((InputMethodDescriptor) c.newInstance());
 131:                   }
 132:                 line = in.readLine().trim();
 133:               }
 134:             catch (IOException ex)
 135:               {
 136:                 continue outer;
 137:               }
 138:             catch (Exception ignored)
 139:               {
 140:               }
 141:           }
 142:       }
 143:   }
 144: 
 145:   /** The current input method; null if no input methods are installed. */
 146:   private InputMethod im;
 147: 
 148:   /** Map of locales to the most recently selected input method. */
 149:   private final HashMap<Locale,InputMethod> recent 
 150:     = new HashMap<Locale,InputMethod>();
 151: 
 152:   /** The list of acceptable character subsets. */
 153:   private Character.Subset[] subsets;
 154: 
 155:   /**
 156:    * Construct an InputContext. This is protected, so clients must use
 157:    * {@link #getInstance()} instead.
 158:    */
 159:   protected InputContext()
 160:   {
 161:   }
 162: 
 163:   /**
 164:    * Returns a new InputContext.
 165:    *
 166:    * @return a new instance, initialized to the default locale if available
 167:    */
 168:   public static InputContext getInstance()
 169:   {
 170:     InputContext ic = new InputContext();
 171:     ic.selectInputMethod(Locale.getDefault());
 172:     return ic;
 173:   }
 174: 
 175:   /**
 176:    * Attempts to select an input method or keyboard layout which supports the
 177:    * given locale. This returns true if a locale is available and was selected.
 178:    * The following steps are taken in choosing an input method:<ul>
 179:    * <li>If the currently selected input method or keyboard layout supports
 180:    * the requested locale, it remains selected.</li>
 181:    * <li>If there is no input method or keyboard layout available that
 182:    * supports the requested locale, the current input method or keyboard
 183:    * layout remains selected.</li>
 184:    * <li>If the user has previously selected an input method or keyboard
 185:    * layout for the requested locale from the user interface, then the most
 186:    * recently selected such input method or keyboard layout is reselected.</li>
 187:    * <li>Otherwise, an input method or keyboard layout that supports the
 188:    * requested locale is selected in an implementation dependent way. This
 189:    * implementation chooses the first input method which supports the requested
 190:    * locale based on the InputMethodDescriptors loaded from the extensions
 191:    * installed on the CLASSPATH.</li>
 192:    * </ul>
 193:    *
 194:    * <p>Before switching away from an input method, any currently uncommitted
 195:    * text is committed. Not all host operating systems provide API to
 196:    * determine the locale of the currently selected native input method or
 197:    * keyboard layout, and to select a native input method or keyboard layout
 198:    * by locale. For host operating systems that don't provide such API,
 199:    * selectInputMethod assumes that native input methods or keyboard layouts
 200:    * provided by the host operating system support only the system's default
 201:    * locale.
 202:    *
 203:    * <p>An example of where this may be called is in a multi-language document,
 204:    * when moving the insertion point between sections of different locale, so
 205:    * that the user may use the input method appropriate to that section of the
 206:    * document.
 207:    *
 208:    * @param locale the desired new locale
 209:    * @return true if the new locale is active
 210:    * @throws NullPointerException if locale is null
 211:    */
 212:   public boolean selectInputMethod(Locale locale)
 213:   {
 214:     if (im != null && im.setLocale(locale))
 215:       {
 216:         recent.put(locale, im);
 217:         return true;
 218:       }
 219:     InputMethod next = (InputMethod) recent.get(locale);
 220:   outer:
 221:     if (next != null)
 222:       for (int i = 0, limit = descriptors.size(); i < limit; i++)
 223:         {
 224:           InputMethodDescriptor d = (InputMethodDescriptor) descriptors.get(i);
 225:           Locale[] list;
 226:           try
 227:             {
 228:               list = d.getAvailableLocales();
 229:             }
 230:           catch (AWTException ignored)
 231:             {
 232:               continue;
 233:             }
 234:           for (int j = list.length; --j >= 0; )
 235:             if (locale.equals(list[j]))
 236:               {
 237:                 try
 238:                   {
 239:                     next = d.createInputMethod();
 240:                     recent.put(locale, next);
 241:                   }
 242:                 catch (Exception ignored)
 243:                   {
 244:                     continue;
 245:                   }
 246:               }
 247:         }
 248:     if (next == null)
 249:       return false;
 250:     // XXX I'm not sure if this does all the necessary steps in the switch.
 251:     if (im != null)
 252:       {
 253:         try
 254:           {
 255:             next.setCompositionEnabled(im.isCompositionEnabled());
 256:           }
 257:         catch (UnsupportedOperationException ignored)
 258:           {
 259:           }
 260:         im.endComposition();
 261:         im.deactivate(false);
 262:         im.hideWindows();
 263:       }
 264:     im = next;
 265:     im.setLocale(locale);
 266:     im.setCharacterSubsets(subsets);
 267:     return true;
 268:   }
 269: 
 270:   /**
 271:    * Returns the current locale of the current input method or keyboard
 272:    * layout. Returns null if the input context does not have a current input
 273:    * method or keyboard layout or if the current input method's
 274:    * {@link InputMethod#getLocale()} method returns null. Not all host
 275:    * operating systems provide API to determine the locale of the currently
 276:    * selected native input method or keyboard layout. For host operating
 277:    * systems that don't provide such API, getLocale assumes that the current
 278:    * locale of all native input methods or keyboard layouts provided by the
 279:    * host operating system is the system's default locale.
 280:    *
 281:    * @return the locale of the current input method, or null
 282:    * @since 1.3
 283:    */
 284:   public Locale getLocale()
 285:   {
 286:     return im == null ? null : im.getLocale();
 287:   }
 288: 
 289:   /**
 290:    * Sets the subsets of Unicode characters allowed to be input by the current
 291:    * input method, as well as subsequent input methods. The value of null
 292:    * implies all characters are legal. Applications should not rely on this
 293:    * behavior, since native host input methods may not allow restrictions.
 294:    * If no current input method is available, this has no immediate effect.
 295:    *
 296:    * @param subsets the set of Unicode subsets to accept, or null
 297:    */
 298:   public void setCharacterSubsets(Character.Subset[] subsets)
 299:   {
 300:     this.subsets = subsets;
 301:     if (im != null)
 302:       im.setCharacterSubsets(subsets);
 303:   }
 304: 
 305:   /**
 306:    * Changes the enabled status of the current input method. An input method
 307:    * that is enabled for composition interprets incoming events for both
 308:    * composition and control purposes, while a disabled input method only
 309:    * interprets control commands (including commands to enable itself).
 310:    *
 311:    * @param enable whether to enable the input method
 312:    * @throws UnsupportedOperationException if there is no current input method,
 313:    *         or the input method does not support enabling
 314:    * @see #isCompositionEnabled()
 315:    * @since 1.3
 316:    */
 317:   public void setCompositionEnabled(boolean enable)
 318:   {
 319:     if (im == null)
 320:       throw new UnsupportedOperationException();
 321:     im.setCompositionEnabled(enable);
 322:   }
 323: 
 324:   /**
 325:    * Find out if the current input method is enabled.
 326:    *
 327:    * @return true if the current input method is enabled
 328:    * @throws UnsupportedOperationException if there is no current input method,
 329:    *         or the input method does not support enabling
 330:    * @see #setCompositionEnabled(boolean)
 331:    * @since 1.3
 332:    */
 333:   public boolean isCompositionEnabled()
 334:   {
 335:     if (im == null)
 336:       throw new UnsupportedOperationException();
 337:     return im.isCompositionEnabled();
 338:   }
 339: 
 340:   /**
 341:    * Starts a reconversion operation in the current input method. The input
 342:    * method gets the text to reconvert from the client component, using
 343:    * {@link InputMethodRequests#getSelectedText(Attribute[])}. Then the
 344:    * composed and committed text produced by the operation is sent back to
 345:    * the client using a sequence of InputMethodRequests.
 346:    *
 347:    * @throws UnsupportedOperationException if there is no current input method,
 348:    *         or the input method does not support reconversion
 349:    * @since 1.3
 350:    */
 351:   public void reconvert()
 352:   {
 353:     if (im == null)
 354:       throw new UnsupportedOperationException();
 355:     im.reconvert();
 356:   }
 357: 
 358:   /**
 359:    * Dispatches an event to the current input method. This is called
 360:    * automatically by AWT. If no input method is available, then the event
 361:    * will never be consumed.
 362:    *
 363:    * @param event the event to dispatch
 364:    * @throws NullPointerException if event is null
 365:    */
 366:   public void dispatchEvent(AWTEvent event)
 367:   {
 368:     if (im != null)
 369:       im.dispatchEvent(event);
 370:   }
 371: 
 372:   /**
 373:    * Notifies the input context that a client component has been removed from
 374:    * its containment hierarchy, or that input method support has been disabled
 375:    * for the component. This method is usually called from the client
 376:    * component's {@link Component#removeNotify()} method. Potentially pending
 377:    * input from input methods for this component is discarded. If no input
 378:    * methods are available, then this method has no effect.
 379:    *
 380:    * @param client the client component
 381:    * @throws NullPointerException if client is null
 382:    */
 383:   public void removeNotify(Component client)
 384:   {
 385:     // XXX What to do with client information?
 386:     if (im != null)
 387:       {
 388:         im.deactivate(false);
 389:         im.removeNotify();
 390:       }
 391:   }
 392: 
 393:   /**
 394:    * Ends any input composition that may currently be going on in this
 395:    * context. Depending on the platform and possibly user preferences, this
 396:    * may commit or delete uncommitted text. Any changes to the text are
 397:    * communicated to the active component using an input method event. If no
 398:    * input methods are available, then this method has no effect. This may
 399:    * be called for a variety of reasons, such as when the user moves the
 400:    * insertion point in the client text outside the range of the composed text,
 401:    * or when text is saved to file.
 402:    */
 403:   public void endComposition()
 404:   {
 405:     if (im != null)
 406:       im.endComposition();
 407:   }
 408: 
 409:   /**
 410:    * Disposes of the input context and release the resources used by it.
 411:    * Called automatically by AWT for the default input context of each
 412:    * Window. If no input methods are available, then this method has no
 413:    * effect.
 414:    */
 415:   public void dispose()
 416:   {
 417:     if (im != null)
 418:       {
 419:         im.deactivate(false);
 420:         im.dispose();
 421:       }
 422:   }
 423: 
 424:   /**
 425:    * Returns a control object from the current input method, or null. A
 426:    * control object provides implementation-dependent methods that control
 427:    * the behavior of the input method or obtain information from the input
 428:    * method. Clients have to compare the result against known input method
 429:    * control object types. If no input methods are available or the current
 430:    * input method does not provide an input method control object, then null
 431:    * is returned. 
 432:    *
 433:    * @return the control object, or null
 434:    */
 435:   public Object getInputMethodControlObject()
 436:   {
 437:     return im == null ? null : im.getControlObject();
 438:   }
 439: } // class InputContext