Source for javax.swing.text.LayoutQueue

   1: /* LayoutQueue.java --
   2:    Copyright (C) 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 javax.swing.text;
  40: 
  41: import java.util.LinkedList;
  42: 
  43: /**
  44:  * This is a queue which holds {@link Runnable} objects.  It is
  45:  * intended for deferring layout operations.
  46:  */
  47: public class LayoutQueue
  48: {
  49:   // The default layout queue.
  50:   private static LayoutQueue defaultQueue = new LayoutQueue();
  51: 
  52:   // The queue of tasks.
  53:   private LinkedList list = new LinkedList();
  54: 
  55:   /**
  56:    * Create a new layout queue.
  57:    */
  58:   public LayoutQueue()
  59:   {
  60:     // Nothing to do here.
  61:   }
  62: 
  63:   /**
  64:    * Add a layout task to the queue.
  65:    */
  66:   public void addTask(Runnable task)
  67:   {
  68:     synchronized (list)
  69:       {
  70:         list.addLast(task);
  71:         list.notify();
  72:       }
  73:   }
  74: 
  75:   /**
  76:    * Called by a worker thread to retrieve the next layout task.  This
  77:    * will block until a new task is available.  This method will
  78:    * return null if the thread is interrupted while waiting.
  79:    */
  80:   protected Runnable waitForWork()
  81:   {
  82:     synchronized (list)
  83:       {
  84:         while (list.size() == 0)
  85:           {
  86:             try
  87:               {
  88:                 list.wait();
  89:               }
  90:             catch (InterruptedException _)
  91:               {
  92:                 // This seemed like a good idea, but it has not been
  93:                 // tested on the JDK.
  94:                 return null;
  95:               }
  96:           }
  97:         return (Runnable) list.removeFirst();
  98:       }
  99:   }
 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: }