/*
* Copyright (c) 1999, 2008, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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*/
package javax.swing.text;
import java.util.Vector;
import sun.awt.AppContext;
/**
* A queue of text layout tasks.
*
* @author Timothy Prinzing
* @see AsyncBoxView
* @since 1.3
*/
public class LayoutQueue {
private static final Object DEFAULT_QUEUE = new Object();
private Vector<Runnable> tasks;
private Thread worker;
/**
* Construct a layout queue.
*/
public LayoutQueue() {
tasks = new Vector<Runnable>();
}
/**
* Fetch the default layout queue.
*/
public static LayoutQueue getDefaultQueue() {
AppContext ac = AppContext.getAppContext();
synchronized (DEFAULT_QUEUE) {
LayoutQueue defaultQueue = (LayoutQueue) ac.get(DEFAULT_QUEUE);
if (defaultQueue == null) {
defaultQueue = new LayoutQueue();
ac.put(DEFAULT_QUEUE, defaultQueue);
}
return defaultQueue;
}
}
/**
* Set the default layout queue.
*
* @param q the new queue.
*/
public static void setDefaultQueue(LayoutQueue q) {
synchronized (DEFAULT_QUEUE) {
AppContext.getAppContext().put(DEFAULT_QUEUE, q);
}
}
/**
* Add a task that is not needed immediately because
* the results are not believed to be visible.
*/
public synchronized void addTask(Runnable task) {
if (worker == null) {
worker = new LayoutThread();
worker.start();
}
tasks.addElement(task);
notifyAll();
}
/**
* Used by the worker thread to get a new task to execute
*/
protected synchronized Runnable waitForWork() {
while (tasks.size() == 0) {
try {
wait();
} catch (InterruptedException ie) {
return null;
}
}
Runnable work = tasks.firstElement();
tasks.removeElementAt(0);
return work;
}
/**
* low priority thread to perform layout work forever
*/
class LayoutThread extends Thread {
LayoutThread() {
super("text-layout");
setPriority(Thread.MIN_PRIORITY);
}
public void run() {
Runnable work;
do {
work = waitForWork();
if (work != null) {
work.run();
}
} while (work != null);
}
}
}