1 /* 2 * Copyright (c) 1999, 2008, 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 javax.swing.text; 26 27 import java.util.Vector; 28 import sun.awt.AppContext; 29 30 /** 31 * A queue of text layout tasks. 32 * 33 * @author Timothy Prinzing 34 * @see AsyncBoxView 35 * @since 1.3 36 */ 37 public class LayoutQueue { 38 39 private static final Object DEFAULT_QUEUE = new Object(); 40 41 private Vector<Runnable> tasks; 42 private Thread worker; 43 44 /** 45 * Construct a layout queue. 46 */ 47 public LayoutQueue() { 48 tasks = new Vector<Runnable>(); 49 } 50 51 /** 52 * Fetch the default layout queue. 53 * @return the default layout queue 54 */ 55 public static LayoutQueue getDefaultQueue() { 56 AppContext ac = AppContext.getAppContext(); 57 synchronized (DEFAULT_QUEUE) { 58 LayoutQueue defaultQueue = (LayoutQueue) ac.get(DEFAULT_QUEUE); 59 if (defaultQueue == null) { 60 defaultQueue = new LayoutQueue(); 61 ac.put(DEFAULT_QUEUE, defaultQueue); 62 } 63 return defaultQueue; 64 } 65 } 66 67 /** 68 * Set the default layout queue. 69 * 70 * @param q the new queue. 71 */ 72 public static void setDefaultQueue(LayoutQueue q) { 73 synchronized (DEFAULT_QUEUE) { 74 AppContext.getAppContext().put(DEFAULT_QUEUE, q); 75 } 76 } 77 78 /** 79 * Add a task that is not needed immediately because 80 * the results are not believed to be visible. 81 * @param task the task to add to the queue 82 */ 83 public synchronized void addTask(Runnable task) { 84 if (worker == null) { 85 worker = new LayoutThread(); 86 worker.start(); 87 } 88 tasks.addElement(task); 89 notifyAll(); 90 } 91 92 /** 93 * Used by the worker thread to get a new task to execute. 94 * @return a task from the queue 95 */ 96 protected synchronized Runnable waitForWork() { 97 while (tasks.size() == 0) { 98 try { 99 wait(); 100 } catch (InterruptedException ie) { 101 return null; 102 } 103 } 104 Runnable work = tasks.firstElement(); 105 tasks.removeElementAt(0); 106 return work; 107 } 108 109 /** 110 * low priority thread to perform layout work forever 111 */ 112 class LayoutThread extends Thread { 113 114 LayoutThread() { 115 super("text-layout"); 116 setPriority(Thread.MIN_PRIORITY); 117 } 118 119 public void run() { 120 Runnable work; 121 do { 122 work = waitForWork(); 123 if (work != null) { 124 work.run(); 125 } 126 } while (work != null); 127 } 128 129 130 } 131 132 }