path: root/libjava/classpath/javax/swing/Timer.java

/* Timer.java --
   Copyright (C) 2002, 2004, 2005  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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02110-1301 USA.

Linking this library statically or dynamically with other modules is
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
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package javax.swing;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.Serializable;
import java.util.EventListener;

import javax.swing.event.EventListenerList;

/**
 * Fires one or more action events after the specified delay.  This is
 * a specialised version of <code>java.util.Timer</code> just for
 * firing <code>ActionEvent</code>s. All Timers share one (daemon)
 * Thread (or java.util.Timer). All events are fired from the event
 * queue.
 * 
 * @author Ronald Veldema
 * @author Audrius Meskauskas (audriusa@Bionformatics.org) - bug fixes
 * and documentation comments
 */
public class Timer
  implements Serializable
{
  /**
   * Given to the shared java.util.Timer to (possibly repeatedly) call
   * queueEvent().
   */
  private class Task extends java.util.TimerTask
  {
    public void run()
    {
      if (logTimers)
	System.out.println("javax.swing.Timer -> queueEvent()");
      queueEvent();

      if (!repeats)
	task = null;
    }
  }

  /**
   * Use serialVersionUID for interoperability.
   */
  private static final long serialVersionUID = -1116180831621385484L;

  /**
   * The encloding class, used with {@link SwingUtilities#invokeLater}
   * to invoke the {@link #drainEvents()}.
   */
  private Runnable drainer = new Runnable()
    {
      public void run()
      {
        drainEvents();
      }
    };

  /**
   * The static java.util.Timer daemon which will be used to schedule
   * all javax.swing.Timer.Task objects. The daemon will always be
   * running, even if there's no task scheduled in it.
   */
  private static java.util.Timer timer = new java.util.Timer("swing.Timer",
							     true);

  /**
   * If <code>true</code>, the timer prints a message to
   * {@link System#out} when firing each event.
   */
  static boolean logTimers;

  /**
   * A field to store all listeners who are listening to this timer.
   */
  protected EventListenerList listenerList = new EventListenerList();

  /**
   * <code>true</code> if the timer coalesces events.
   */
  boolean coalesce = true;

  /**
   * <code>true</code> if the timer is firing repetetive events.
   */
  boolean repeats = true;

  /**
   * The delay between subsequent repetetive events.
   */
  int delay;

  /**
   * The initial delay before the first event.
   */
  int initialDelay;

  /**
   * The number of events that have been already fired by this timer.
   * This is used as a numeric identifier for the next event that would
   * be fired.
   */
  int ticks;

  /**
   * The task that calls queueEvent(). When null this Timer is stopped.
   */
  private Task task;

  /**
   * This object manages a "queue" of virtual actionEvents, maintained as a
   * simple long counter. When the timer expires, a new event is queued,
   * and a dispatcher object is pushed into the system event queue. When
   * the system thread runs the dispatcher, it will fire as many
   * ActionEvents as have been queued, unless the timer is set to
   * coalescing mode, in which case it will fire only one ActionEvent.
   */
  private long queue;

  /**
   * <code>synchronized(queueLock)</code> replaces
   * <code>synchronized(queue)</code> that is not supported by this language.
   */
  private Object queueLock = new Object();

  /**
   * Creates a new Timer object.
   *
   * @param d the default value for both initial and between event delay, in
   * milliseconds.
   * @param listener the first action listener, can be <code>null</code>.
   */
  public Timer(int d, ActionListener listener)
  {
    delay = d;
    initialDelay = d;

    if (listener != null)
      addActionListener(listener);
  }

  /**
   * Get the array of action listeners.
   *
   * @return the array of action listeners that are listening for the events,
   * fired by this timer
   *
   * @since 1.4
   */
  public ActionListener[] getActionListeners()
  {
    return (ActionListener[]) listenerList.getListeners(ActionListener.class);
  }

  /**
   * Sets whether the Timer coalesces multiple pending event firings.
   * If the coalescing is enabled, the multiple events that have not been
   * fired on time are replaced by the single event. The events may not
   * be fired on time if the application is busy.
   *
   * @param c <code>true</code> (default) to enable the event coalescing,
   * <code>false</code> otherwise
   */
  public void setCoalesce(boolean c)
  {
    coalesce = c;
  }

  /**
   * Checks if the Timer coalesces multiple pending event firings.
   * If the coalescing is enabled, the multiple events that have not been
   * fired on time are replaced by the single event. The events may not
   * be fired on time if the application is busy.
   *
   * @return <code>true</code> if the coalescing is enabled,
   * <code>false</code> otherwise
   */
  public boolean isCoalesce()
  {
    return coalesce;
  }

  /**
   * Get the event listeners of the given type that are listening for the
   * events, fired by this timer.
   *
   * @param listenerType the listener type (for example, ActionListener.class)
   *
   * @return the array of event listeners that are listening for the events,
   * fired by this timer
   * @since 1.3
   */
  public EventListener[] getListeners(Class listenerType)
  {
    return listenerList.getListeners(listenerType);
  }

  /**
   * Set the timer logging state. If it is set to <code>true</code>, the
   * timer prints a message to {@link System#out} when firing each
   * action event.
   *
   * @param lt <code>true</code> if logging is enabled, <code>false</code>
   * (default value) otherwise
   */
  public static void setLogTimers(boolean lt)
  {
    logTimers = lt;
  }

  /**
   * Return the logging state.
   *
   * @return <code>true</code> if the timer is printing a message to
   * {@link System#out}
   * when firing each action event
   */
  public static boolean getLogTimers()
  {
    return logTimers;
  }

  /**
   * Set the delay between firing the subsequent events.
   * This parameter does not change the value of the initial delay before
   * firing the first event.
   *
   * @param d The time gap between the subsequent events, in milliseconds
   */
  public void setDelay(int d)
  {
    delay = d;
  }

  /**
   * Get the delay between firing the subsequent events.
   *
   * @return The delay between subsequent events, in milliseconds
   */
  public int getDelay()
  {
    return delay;
  }

  /**
   * Set the intial delay before firing the first event since calling
   * the {@link #start()} method. If the initial delay has not been
   * set, it is assumed having the same value as the delay between the
   * subsequent events.
   *
   * @param i the initial delay, in milliseconds
   */
  public void setInitialDelay(int i)
  {
    initialDelay = i;
  }

  /**
   * Get the intial delay before firing the first event since calling
   * the {@link #start()} method. If the initial delay has not been
   * set, returns the same value as {@link #getDelay()}.
   *
   * @return the initial delay before firing the first action event.
   */
  public int getInitialDelay()
  {
    return initialDelay;
  }

  /**
   * Enable firing the repetetive events.
   *
   * @param r <code>true</code> (default value) to fire repetetive events.
   * <code>false</code> to fire
   * only one event after the initial delay
   */
  public void setRepeats(boolean r)
  {
    repeats = r;
  }

  /**
   * Check is this timer fires repetetive events.
   *
   * @return <code>true</code> if the timer fires repetetive events,
   * <code>false</code> if it fires
   * only one event after the initial delay
   */
  public boolean isRepeats()
  {
    return repeats;
  }

  /**
   * Get the timer state.
   *
   * @return <code>true</code> if the timer has been started and is firing
   * the action events as scheduled. <code>false</code>
   * if the timer is inactive.
   */
  public boolean isRunning()
  {
    return task != null;
  }

  /**
   * Add the action listener
   *
   * @param listener the action listener to add
   */
  public void addActionListener(ActionListener listener)
  {
    listenerList.add(ActionListener.class, listener);
  }

  /**
   * Remove the action listener.
   *
   * @param listener the action listener to remove
   */
  public void removeActionListener(ActionListener listener)
  {
    listenerList.remove(ActionListener.class, listener);
  }

  /**
   * Cancel all pending tasks and fire the first event after the initial
   * delay.
   */
  public void restart()
  {
    stop();
    start();
  }

  /**
   * Start firing the action events.
   */
  public void start()
  {
    Task t = task;
    if (t == null)
      {
	t = new Task();
	if (isRepeats())
	  timer.schedule(t, getInitialDelay(), getDelay());
	else
	  timer.schedule(t, getInitialDelay());
	task = t;
      }
  }

  /**
   * Stop firing the action events.
   */
  public void stop()
  {
    Task t = task;
    if (t != null)
      {
	t.cancel();
	task = null;
      }
  }

  /**
   * Fire the given action event to the action listeners.
   *
   * @param event the event to fire
   */
  protected void fireActionPerformed(ActionEvent event)
  {
    ActionListener[] listeners = getActionListeners();

    for (int i = 0; i < listeners.length; i++)
      listeners [ i ].actionPerformed(event);
  }

  /**
   * Fire the action event, named "Timer" and having the numeric
   * identifier, equal to the numer of events that have been
   * already fired before.
   */
  void fireActionPerformed()
  {
    fireActionPerformed(new ActionEvent(this, ticks++, "Timer"));
  }

  /**
   * Fire the queued action events.
   * In the coalescing mode, a single event is fired as a replacement
   * for all queued events. In non coalescing mode, a series of
   * all queued events is fired.
   * This is package-private to avoid an accessor method.
   */
  void drainEvents()
  {
    synchronized (queueLock)
      {
        if (isCoalesce())
          {
            if (queue > 0)
              fireActionPerformed();
          }
        else
          {
            while (queue > 0)
              {
                fireActionPerformed();
                queue--;
              }
          }
        queue = 0;
      }
  }

  /**
  * Post a scheduled event to the event queue.
  * Package-private to avoid an accessor method.
  */
  void queueEvent()
  {
    synchronized(queueLock)
      {
	queue++;
	if (queue == 1)
	  SwingUtilities.invokeLater(drainer);
      }
  }
}