001/* LayoutQueue.java -- 002 Copyright (C) 2005 Free Software Foundation, Inc. 003 004This file is part of GNU Classpath. 005 006GNU Classpath is free software; you can redistribute it and/or modify 007it under the terms of the GNU General Public License as published by 008the Free Software Foundation; either version 2, or (at your option) 009any later version. 010 011GNU Classpath is distributed in the hope that it will be useful, but 012WITHOUT ANY WARRANTY; without even the implied warranty of 013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014General Public License for more details. 015 016You should have received a copy of the GNU General Public License 017along with GNU Classpath; see the file COPYING. If not, write to the 018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 01902110-1301 USA. 020 021Linking this library statically or dynamically with other modules is 022making a combined work based on this library. Thus, the terms and 023conditions of the GNU General Public License cover the whole 024combination. 025 026As a special exception, the copyright holders of this library give you 027permission to link this library with independent modules to produce an 028executable, regardless of the license terms of these independent 029modules, and to copy and distribute the resulting executable under 030terms of your choice, provided that you also meet, for each linked 031independent module, the terms and conditions of the license of that 032module. An independent module is a module which is not derived from 033or based on this library. If you modify this library, you may extend 034this exception to your version of the library, but you are not 035obligated to do so. If you do not wish to do so, delete this 036exception statement from your version. */ 037 038 039package javax.swing.text; 040 041import java.util.LinkedList; 042 043/** 044 * This is a queue which holds {@link Runnable} objects. It is 045 * intended for deferring layout operations. 046 */ 047public 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}