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 }