/*
* @(#)LayoutQueue.java 1.6 03/12/19
*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package javax.swing.text;
import java.util.Vector;
/**
* A queue of text layout tasks.
*
* @author Timothy Prinzing
* @version 1.6 12/19/03
* @see AsyncBoxView
* @since 1.3
*/
public class LayoutQueue {
Vector tasks;
Thread worker;
static LayoutQueue defaultQueue;
/**
* Construct a layout queue.
*/
public LayoutQueue() {
tasks = new Vector();
}
/**
* Fetch the default layout queue.
*/
public static LayoutQueue getDefaultQueue() {
if (defaultQueue == null) {
defaultQueue = new LayoutQueue();
}
return defaultQueue;
}
/**
* Set the default layout queue.
*
* @param q the new queue.
*/
public static void setDefaultQueue(LayoutQueue q) {
defaultQueue = 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 = (Runnable) 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);
}
}
}
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