001 /* LayoutQueue.java --
002 Copyright (C) 2005 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
016 You should have received a copy of the GNU General Public License
017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038
039 package javax.swing.text;
040
041 import java.util.LinkedList;
042
043 /**
044 * This is a queue which holds {@link Runnable} objects. It is
045 * intended for deferring layout operations.
046 */
047 public class LayoutQueue
048 {
049 // The default layout queue.
050 private static LayoutQueue defaultQueue = new LayoutQueue();
051
052 // The queue of tasks.
053 private LinkedList list = new LinkedList();
054
055 /**
056 * Create a new layout queue.
057 */
058 public LayoutQueue()
059 {
060 // Nothing to do here.
061 }
062
063 /**
064 * Add a layout task to the queue.
065 */
066 public void addTask(Runnable task)
067 {
068 synchronized (list)
069 {
070 list.addLast(task);
071 list.notify();
072 }
073 }
074
075 /**
076 * Called by a worker thread to retrieve the next layout task. This
077 * will block until a new task is available. This method will
078 * return null if the thread is interrupted while waiting.
079 */
080 protected Runnable waitForWork()
081 {
082 synchronized (list)
083 {
084 while (list.size() == 0)
085 {
086 try
087 {
088 list.wait();
089 }
090 catch (InterruptedException _)
091 {
092 // This seemed like a good idea, but it has not been
093 // tested on the JDK.
094 return null;
095 }
096 }
097 return (Runnable) list.removeFirst();
098 }
099 }
100
101 /**
102 * Return the default layout queue.
103 */
104 public static synchronized LayoutQueue getDefaultQueue()
105 {
106 return defaultQueue;
107 }
108
109 /**
110 * Set the default layout queue.
111 */
112 public static synchronized void setDefaultQueue(LayoutQueue q)
113 {
114 defaultQueue = q;
115 }
116 }