DefaultBoundedRangeModel.java

/* DefaultBoundedRangeModel.java -- Default implementation
   of BoundedRangeModel.
   Copyright (C) 2002, 2004, 2005, 2006,  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
the Free Software Foundation; either version 2, or (at your option)
any later version.

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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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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
executable, regardless of the license terms of these independent
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this exception to your version of the library, but you are not
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package javax.swing;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.EventListener;

import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.event.EventListenerList;

/**
 * The default implementation of <code>BoundedRangeModel</code>.
 *
 * @author Andrew Selkirk (aselkirk@sympatico.ca)
 * @author Sascha Brawer (brawer@dandelis.ch)
 */
public class DefaultBoundedRangeModel
  implements BoundedRangeModel, Serializable
{
  /**
   * The identifier of this class in object serialization. Verified
   * using the serialver tool of Sun J2SE 1.4.1_01.
   */
  private static final long serialVersionUID = 5034068491295259790L;

  /**
   * An event that is sent to all registered {@link ChangeListener}s
   * when the state of this range model has changed.
   *
   * <p>The event object is created on demand, the first time it
   * is actually needed.</p>
   *
   * @see #fireStateChanged()
   */
  protected transient ChangeEvent changeEvent;

  /**
   * The list of the currently registered EventListeners.
   */
  protected EventListenerList listenerList = new EventListenerList();

  /**
   * The current value of the range model, which is always between
   * {@link #minimum} and ({@link #maximum} - {@link #extent}). In a
   * scroll bar visualization of a {@link BoundedRangeModel}, the
   * <code>value</code> is displayed as the position of the thumb.
   */
  private int value;

  /**
   * The current extent of the range model, which is a number greater
   * than or equal to zero. In a scroll bar visualization of a {@link
   * BoundedRangeModel}, the <code>extent</code> is displayed as the
   * size of the thumb.
   */
  private int extent;

  /**
   * The current minimum value of the range model, which is always
   * less than or equal to {@link #maximum}.
   */
  private int minimum;

  /**
   * The current maximum value of the range model, which is always
   * greater than or equal to {@link #minimum}.
   */
  private int maximum;

  /**
   * A property that indicates whether the value of this {@link
   * BoundedRangeModel} is going to change in the immediate future.
   */
  private boolean isAdjusting;

  /**
   * Constructs a <code>DefaultBoundedRangeModel</code> with default
   * values for the properties. The properties <code>value</code>,
   * <code>extent</code> and <code>minimum</code> will be initialized
   * to zero; <code>maximum</code> will be set to 100; the property
   * <code>valueIsAdjusting</code> will be <code>false</code>.
   */
  public DefaultBoundedRangeModel()
  {
    // The fields value, extent, minimum have the default value 0, and
    // isAdjusting is already false. These fields no not need to be
    // set explicitly.
    maximum = 100;
  }

  /**
   * Constructs a <code>DefaultBoundedRangeModel</code> with the
   * specified values for some properties.
   *
   * @param value the initial value of the range model, which must be
   *     a number between <code>minimum</code> and <code>(maximum -
   *     extent)</code>. In a scroll bar visualization of a {@link
   *     BoundedRangeModel}, the <code>value</code> is displayed as the
   *     position of the thumb.
   * @param extent the initial extent of the range model, which is a
   *     number greater than or equal to zero. In a scroll bar
   *     visualization of a {@link BoundedRangeModel}, the
   *     <code>extent</code> is displayed as the size of the thumb.
   * @param minimum the initial minimal value of the range model.
   * @param maximum the initial maximal value of the range model.
   *
   * @throws IllegalArgumentException if the following condition is
   *     not satisfied: <code>minimum &lt;= value &lt;= value + extent &lt;=
   *     maximum</code>.
   */
  public DefaultBoundedRangeModel(int value, int extent, int minimum,
                                  int maximum)
  {
    if (!(minimum <= value && extent >= 0 && (value + extent) <= maximum))
      throw new IllegalArgumentException();

    this.value = value;
    this.extent = extent;
    this.minimum = minimum;
    this.maximum = maximum;

    // The isAdjusting field already has a false value by default.
  }

  /**
   * Returns a string with all relevant properties of this range
   * model.
   *
   * @return a string representing the object
   */
  public String toString()
  {
    return getClass().getName()
      + "[value=" + value
      + ", extent=" + extent
      + ", min=" + minimum
      + ", max=" + maximum
      + ", adj=" + isAdjusting
      + ']';
  }

  /**
   * Returns the current value of this bounded range model.  In a
   * scroll bar visualization of a {@link BoundedRangeModel}, the
   * <code>value</code> is displayed as the position of the thumb.
   *
   * @return the value
   */
  public int getValue()
  {
    return value;
  }

  /**
   * Changes the current value of this bounded range model. In a
   * scroll bar visualization of a {@link BoundedRangeModel}, the
   * <code>value</code> is displayed as the position of the thumb;
   * changing the <code>value</code> of a scroll bar's model
   * thus moves the thumb to a different position.
   *
   * @param value the value
   */
  public void setValue(int value)
  {
    value = Math.max(minimum, value);
    if (value + extent > maximum)
      value = maximum - extent;

    if (value != this.value)
      {
        this.value = value;
        fireStateChanged();
      }
  }

  /**
   * Returns the current extent of this bounded range model, which is
   * a number greater than or equal to zero. In a scroll bar
   * visualization of a {@link BoundedRangeModel}, the
   * <code>extent</code> is displayed as the size of the thumb.
   *
   * @return the extent
   */
  public int getExtent()
  {
    return extent;
  }

  /**
   * Changes the current extent of this bounded range model. In a
   * scroll bar visualization of a {@link BoundedRangeModel}, the
   * <code>extent</code> is displayed as the size of the thumb.
   *
   * @param extent the new extent of the range model, which is a
   *     number greater than or equal to zero.
   */
  public void setExtent(int extent)
  {
    extent = Math.max(extent, 0);
    if (value + extent > maximum)
      extent = maximum - value;

    if (extent != this.extent)
      {
        this.extent = extent;
        fireStateChanged();
      }
  }

  /**
   * Returns the current minimal value of this bounded range model.
   */
  public int getMinimum()
  {
    return minimum;
  }

  /**
   * Changes the current minimal value of this bounded range model.
   *
   * @param minimum the new minimal value.
   */
  public void setMinimum(int minimum)
  {
    int value, maximum;

    maximum = Math.max(minimum, this.maximum);
    value = Math.max(minimum, this.value);

    setRangeProperties(value, extent, minimum, maximum, isAdjusting);
  }

  /**
   * Returns the current maximal value of this bounded range model.
   *
   * @return the maximum
   */
  public int getMaximum()
  {
    return maximum;
  }

  /**
   * Changes the current maximal value of this bounded range model.
   *
   * @param maximum the new maximal value.
   */
  public void setMaximum(int maximum)
  {
    int value, extent, minimum;

    minimum = Math.min(this.minimum, maximum);
    extent = Math.min(this.extent, maximum - minimum);
    value = Math.min(this.value, maximum - extent);

    setRangeProperties(value, extent, minimum, maximum, isAdjusting);
  }

  /**
   * Returns whether or not the value of this bounded range model is
   * going to change in the immediate future. Scroll bars set this
   * property to <code>true</code> while the thumb is being dragged
   * around; when the mouse is relased, they set the property to
   * <code>false</code> and post a final {@link ChangeEvent}.
   *
   * @return <code>true</code> if the value will change soon again;
   *     <code>false</code> if the value will probably not change soon.
   */
  public boolean getValueIsAdjusting()
  {
    return isAdjusting;
  }

  /**
   * Specifies whether or not the value of this bounded range model is
   * going to change in the immediate future. Scroll bars set this
   * property to <code>true</code> while the thumb is being dragged
   * around; when the mouse is relased, they set the property to
   * <code>false</code>.
   *
   * @param isAdjusting <code>true</code> if the value will change
   *     soon again; <code>false</code> if the value will probably not
   *     change soon.
   */
  public void setValueIsAdjusting(boolean isAdjusting)
  {
    if (isAdjusting == this.isAdjusting)
      return;

    this.isAdjusting = isAdjusting;
    fireStateChanged();
  }

  /**
   * Sets all properties.
   *
   * @param value the new value of the range model.  In a scroll bar
   *     visualization of a {@link BoundedRangeModel}, the
   *     <code>value</code> is displayed as the position of the thumb.
   * @param extent the new extent of the range model, which is a
   *     number greater than or equal to zero. In a scroll bar
   *     visualization of a {@link BoundedRangeModel}, the
   *     <code>extent</code> is displayed as the size of the thumb.
   * @param minimum the new minimal value of the range model.
   * @param maximum the new maximal value of the range model.
   * @param isAdjusting whether or not the value of this bounded range
   *     model is going to change in the immediate future. Scroll bars set
   *     this property to <code>true</code> while the thumb is being
   *     dragged around; when the mouse is relased, they set the property
   *     to <code>false</code>.
   */
  public void setRangeProperties(int value, int extent, int minimum,
                                 int maximum, boolean isAdjusting)
  {
    minimum = Math.min(Math.min(minimum, maximum), value);
    maximum = Math.max(value, maximum);
    if (extent + value > maximum)
      extent = maximum - value;
    extent = Math.max(0, extent);

    if ((value == this.value)
        && (extent == this.extent)
        && (minimum == this.minimum)
        && (maximum == this.maximum)
        && (isAdjusting == this.isAdjusting))
      return;

    this.value = value;
    this.extent = extent;
    this.minimum = minimum;
    this.maximum = maximum;
    this.isAdjusting = isAdjusting;
		
    fireStateChanged();
  }

  /**
   * Subscribes a ChangeListener to state changes.
   *
   * @param listener the listener to be subscribed.
   */
  public void addChangeListener(ChangeListener listener)
  {
    listenerList.add(ChangeListener.class, listener);
  }

  /**
   * Cancels the subscription of a ChangeListener.
   *
   * @param listener the listener to be unsubscribed.
   */
  public void removeChangeListener(ChangeListener listener)
  {
    listenerList.remove(ChangeListener.class, listener);
  }

  /**
   * Sends a {@link ChangeEvent} to any registered {@link
   * ChangeListener}s.
   *
   * @see #addChangeListener(ChangeListener)
   * @see #removeChangeListener(ChangeListener)
   */
  protected void fireStateChanged()
  {
    ChangeListener[] listeners = getChangeListeners();
    
    if (changeEvent == null)
      changeEvent = new ChangeEvent(this);

    for (int i = listeners.length - 1; i >= 0; --i)
      listeners[i].stateChanged(changeEvent);
  }

  /**
   * Retrieves the current listeners of the specified class.
   *
   * @param listenerType the class of listeners; usually {@link
   *     ChangeListener}<code>.class</code>.
   *
   * @return an array with the currently subscribed listeners, or
   *     an empty array if there are currently no listeners.
   *
   * @since 1.3
   */
  public <T extends EventListener> T[] getListeners(Class<T> listenerType)
  {
    return listenerList.getListeners(listenerType);
  }

  /**
   * Returns all <code>ChangeListeners</code> that are currently
   * subscribed for changes to this
   * <code>DefaultBoundedRangeModel</code>.
   *
   * @return an array with the currently subscribed listeners, or
   *     an empty array if there are currently no listeners.
   *
   * @since 1.4
   */
  public ChangeListener[] getChangeListeners()
  {
    return (ChangeListener[]) getListeners(ChangeListener.class);
  }
  
  /**
   * Provides serialization support.
   *
   * @param stream  the output stream (<code>null</code> not permitted).
   *
   * @throws IOException  if there is an I/O error.
   */
  private void writeObject(ObjectOutputStream stream) 
    throws IOException 
  {
    stream.defaultWriteObject();
  }

  /**
   * Provides serialization support.
   *
   * @param stream  the input stream (<code>null</code> not permitted).
   *
   * @throws IOException  if there is an I/O error.
   * @throws ClassNotFoundException  if there is a classpath problem.
   */
  private void readObject(ObjectInputStream stream)
    throws ClassNotFoundException, IOException
  {
    stream.defaultReadObject();
    listenerList = new EventListenerList();
  }

}