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1 /* |
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2 * Copyright (c) 1999, 2008, Oracle and/or its affiliates. All rights reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. Oracle designates this |
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8 * particular file as subject to the "Classpath" exception as provided |
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9 * by Oracle in the LICENSE file that accompanied this code. |
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10 * |
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11 * This code is distributed in the hope that it will be useful, but WITHOUT |
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12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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14 * version 2 for more details (a copy is included in the LICENSE file that |
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15 * accompanied this code). |
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16 * |
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17 * You should have received a copy of the GNU General Public License version |
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18 * 2 along with this work; if not, write to the Free Software Foundation, |
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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20 * |
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21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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22 * or visit www.oracle.com if you need additional information or have any |
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23 * questions. |
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24 */ |
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25 package javax.swing.text; |
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26 |
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27 import java.util.Vector; |
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28 import sun.awt.AppContext; |
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29 |
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30 /** |
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31 * A queue of text layout tasks. |
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32 * |
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33 * @author Timothy Prinzing |
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34 * @see AsyncBoxView |
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35 * @since 1.3 |
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36 */ |
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37 public class LayoutQueue { |
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38 |
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39 private static final Object DEFAULT_QUEUE = new Object(); |
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40 |
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41 private Vector<Runnable> tasks; |
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42 private Thread worker; |
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43 |
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44 /** |
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45 * Construct a layout queue. |
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46 */ |
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47 public LayoutQueue() { |
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48 tasks = new Vector<Runnable>(); |
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49 } |
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50 |
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51 /** |
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52 * Fetch the default layout queue. |
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53 */ |
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54 public static LayoutQueue getDefaultQueue() { |
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55 AppContext ac = AppContext.getAppContext(); |
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56 synchronized (DEFAULT_QUEUE) { |
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57 LayoutQueue defaultQueue = (LayoutQueue) ac.get(DEFAULT_QUEUE); |
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58 if (defaultQueue == null) { |
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59 defaultQueue = new LayoutQueue(); |
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60 ac.put(DEFAULT_QUEUE, defaultQueue); |
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61 } |
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62 return defaultQueue; |
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63 } |
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64 } |
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65 |
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66 /** |
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67 * Set the default layout queue. |
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68 * |
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69 * @param q the new queue. |
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70 */ |
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71 public static void setDefaultQueue(LayoutQueue q) { |
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72 synchronized (DEFAULT_QUEUE) { |
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73 AppContext.getAppContext().put(DEFAULT_QUEUE, q); |
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74 } |
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75 } |
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76 |
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77 /** |
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78 * Add a task that is not needed immediately because |
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79 * the results are not believed to be visible. |
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80 */ |
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81 public synchronized void addTask(Runnable task) { |
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82 if (worker == null) { |
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83 worker = new LayoutThread(); |
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84 worker.start(); |
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85 } |
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86 tasks.addElement(task); |
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87 notifyAll(); |
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88 } |
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89 |
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90 /** |
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91 * Used by the worker thread to get a new task to execute |
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92 */ |
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93 protected synchronized Runnable waitForWork() { |
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94 while (tasks.size() == 0) { |
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95 try { |
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96 wait(); |
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97 } catch (InterruptedException ie) { |
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98 return null; |
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99 } |
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100 } |
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101 Runnable work = tasks.firstElement(); |
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102 tasks.removeElementAt(0); |
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103 return work; |
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104 } |
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105 |
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106 /** |
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107 * low priority thread to perform layout work forever |
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108 */ |
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109 class LayoutThread extends Thread { |
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110 |
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111 LayoutThread() { |
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112 super("text-layout"); |
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113 setPriority(Thread.MIN_PRIORITY); |
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114 } |
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115 |
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116 public void run() { |
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117 Runnable work; |
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118 do { |
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119 work = waitForWork(); |
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120 if (work != null) { |
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121 work.run(); |
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122 } |
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123 } while (work != null); |
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124 } |
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125 |
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126 |
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127 } |
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128 |
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129 } |