1 /*
   2  * Copyright (c) 1999, 2015, 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 import sun.misc.ManagedLocalsThread;
  30 
  31 /**
  32  * A queue of text layout tasks.
  33  *
  34  * @author  Timothy Prinzing
  35  * @see     AsyncBoxView
  36  * @since   1.3
  37  */
  38 public class LayoutQueue {
  39 
  40     private static final Object DEFAULT_QUEUE = new Object();
  41 
  42     private Vector<Runnable> tasks;
  43     private Thread worker;
  44 
  45     /**
  46      * Construct a layout queue.
  47      */
  48     public LayoutQueue() {
  49         tasks = new Vector<Runnable>();
  50     }
  51 
  52     /**
  53      * Fetch the default layout queue.
  54      * @return the default layout queue
  55      */
  56     public static LayoutQueue getDefaultQueue() {
  57         AppContext ac = AppContext.getAppContext();
  58         synchronized (DEFAULT_QUEUE) {
  59             LayoutQueue defaultQueue = (LayoutQueue) ac.get(DEFAULT_QUEUE);
  60             if (defaultQueue == null) {
  61                 defaultQueue = new LayoutQueue();
  62                 ac.put(DEFAULT_QUEUE, defaultQueue);
  63             }
  64             return defaultQueue;
  65         }
  66     }
  67 
  68     /**
  69      * Set the default layout queue.
  70      *
  71      * @param q the new queue.
  72      */
  73     public static void setDefaultQueue(LayoutQueue q) {
  74         synchronized (DEFAULT_QUEUE) {
  75             AppContext.getAppContext().put(DEFAULT_QUEUE, q);
  76         }
  77     }
  78 
  79     /**
  80      * Add a task that is not needed immediately because
  81      * the results are not believed to be visible.
  82      * @param task the task to add to the queue
  83      */
  84     public synchronized void addTask(Runnable task) {
  85         if (worker == null) {
  86             Runnable workerRunnable = () -> {
  87                 Runnable work;
  88                 do {
  89                     work = waitForWork();
  90                     if (work != null) {
  91                         work.run();
  92                     }
  93                 } while (work != null);
  94             };
  95             worker = new ManagedLocalsThread(workerRunnable, "text-layout");
  96             worker.setPriority(Thread.MIN_PRIORITY);
  97             worker.start();
  98         }
  99         tasks.addElement(task);
 100         notifyAll();
 101     }
 102 
 103     /**
 104      * Used by the worker thread to get a new task to execute.
 105      * @return a task from the queue
 106      */
 107     protected synchronized Runnable waitForWork() {
 108         while (tasks.size() == 0) {
 109             try {
 110                 wait();
 111             } catch (InterruptedException ie) {
 112                 return null;
 113             }
 114         }
 115         Runnable work = tasks.firstElement();
 116         tasks.removeElementAt(0);
 117         return work;
 118     }
 119 }