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    1   /*
    2    * Copyright (c) 2001, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
   18    * 2 along with this work; if not, write to the Free Software Foundation,
   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   package java.awt;
   26   
   27   import java.awt.event.KeyEvent;
   28   
   29   
   30   /**
   31    * A KeyEventPostProcessor cooperates with the current KeyboardFocusManager
   32    * in the final resolution of all unconsumed KeyEvents. KeyEventPostProcessors
   33    * registered with the current KeyboardFocusManager will receive KeyEvents
   34    * after the KeyEvents have been dispatched to and handled by their targets.
   35    * KeyEvents that would have been otherwise discarded because no Component in
   36    * the application currently owns the focus will also be forwarded to
   37    * registered KeyEventPostProcessors. This will allow applications to implement
   38    * features that require global KeyEvent post-handling, such as menu shortcuts.
   39    * <p>
   40    * Note that the KeyboardFocusManager itself implements KeyEventPostProcessor.
   41    * By default, the current KeyboardFocusManager will be the final
   42    * KeyEventPostProcessor in the chain. The current KeyboardFocusManager cannot
   43    * be completely deregistered as a KeyEventPostProcessor. However, if a
   44    * KeyEventPostProcessor reports that no further post-processing of the
   45    * KeyEvent should take place, the AWT will consider the event fully handled
   46    * and will take no additional action with regard to the event. (While it is
   47    * possible for client code to register the current KeyboardFocusManager as
   48    * a KeyEventPostProcessor one or more times, this is usually unnecessary and
   49    * not recommended.)
   50    *
   51    * @author David Mendenhall
   52    *
   53    * @see KeyboardFocusManager#addKeyEventPostProcessor
   54    * @see KeyboardFocusManager#removeKeyEventPostProcessor
   55    * @since 1.4
   56    */
   57   public interface KeyEventPostProcessor {
   58   
   59       /**
   60        * This method is called by the current KeyboardFocusManager, requesting
   61        * that this KeyEventPostProcessor perform any necessary post-processing
   62        * which should be part of the KeyEvent's final resolution. At the time
   63        * this method is invoked, typically the KeyEvent has already been
   64        * dispatched to and handled by its target. However, if no Component in
   65        * the application currently owns the focus, then the KeyEvent has not
   66        * been dispatched to any Component. Typically, KeyEvent post-processing
   67        * will be used to implement features which require global KeyEvent
   68        * post-handling, such as menu shortcuts. Note that if a
   69        * KeyEventPostProcessor wishes to dispatch the KeyEvent, it must use
   70        * <code>redispatchEvent</code> to prevent the AWT from recursively
   71        * requesting that this KeyEventPostProcessor perform post-processing
   72        * of the event again.
   73        * <p>
   74        * If an implementation of this method returns <code>false</code>, then the
   75        * KeyEvent is passed to the next KeyEventPostProcessor in the chain,
   76        * ending with the current KeyboardFocusManager. If an implementation
   77        * returns <code>true</code>, the KeyEvent is assumed to have been fully
   78        * handled (although this need not be the case), and the AWT will take no
   79        * further action with regard to the KeyEvent. If an implementation
   80        * consumes the KeyEvent but returns <code>false</code>, the consumed
   81        * event will still be passed to the next KeyEventPostProcessor in the
   82        * chain. It is important for developers to check whether the KeyEvent has
   83        * been consumed before performing any post-processing of the KeyEvent. By
   84        * default, the current KeyboardFocusManager will perform no post-
   85        * processing in response to a consumed KeyEvent.
   86        *
   87        * @param e the KeyEvent to post-process
   88        * @return <code>true</code> if the AWT should take no further action with
   89        *         regard to the KeyEvent; <code>false</code> otherwise
   90        * @see KeyboardFocusManager#redispatchEvent
   91        */
   92       boolean postProcessKeyEvent(KeyEvent e);
   93   }

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