gcc/libjava/javax/swing/DefaultButtonModel.java

/* DefaultButtonModel.java -- 
   Copyright (C) 2002, 2004 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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02111-1307 USA.

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permission to link this library with independent modules to produce an
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package javax.swing;

import java.awt.AWTEvent;
import java.awt.AWTEventMulticaster;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.io.Serializable;
import java.util.EventListener;
import java.util.Vector;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.event.EventListenerList;

/**
 * The purpose of this class is to model the dynamic state of an abstract
 * button. The concrete button type holding this state may be a a "toggle"
 * button (checkbox, radio button) or a "push" button (menu button, button).
 * 
 * If the model is disabled, only the "selected" property can be changed.
 * An attempt to change the "armed", "rollover" or "pressed" properties 
 * while the model is disabled will be blocked.
 *
 * Any successful (non-blocked) change to the model's properties will
 * trigger the firing of a ChangeEvent.
 *
 * Any change to the "selected" property will trigger the firing of an
 * ItemEvent in addition to ChangeEvent. This is true whether the model is
 * enabled or not.
 *
 * One other state change is special: the transition from "enabled, armed
 * and pressd" to "enabled, armed and not-pressed". This is considered the
 * "trailing edge" of a successful mouse click, and therefore fires an 
 * ActionEvent in addition to a ChangeEvent.
 *
 * In all other respects this class is just a container of boolean flags.
 *
 * @author Graydon Hoare (graydon&064;redhat.com)
 */
public class DefaultButtonModel implements ButtonModel, Serializable
{
  static final long serialVersionUID = -5342609566534980231L;

  /** Indicates that the button is <em>partially</em> committed to being
   pressed, but not entirely. This usually happens when a user has pressed
   but not yet released the mouse button. */
  static int ARMED = 1;

  /** State constant indicating that the button is enabled. Buttons cannot
   be pressed or selected unless they are enabled. */
  static int ENABLED = 2;

  /** State constant indicating that the user is holding down the button.
   When this transitions from true to false, an ActionEvent may be fired,
   depending on the value of the "armed" property.*/
  static int PRESSED = 4;

  /** State constant indicating that the mouse is currently positioned over
      the button. */
  static int ROLLOVER = 8;

  /** State constant indicating that the button is selected. This constant
      is only meaningful for toggle-type buttons (radio buttons,
      checkboxes). */
  static int SELECTED = 16;

  /** Represents the "state properties" (armed, enabled, pressed, rollover
      and selected) by a bitwise combination of integer constants. */
  int stateMask;

  /** List of ItemListeners, ChangeListeners, and ActionListeners
      registered on this model. */
  EventListenerList listenerList;

  /** The single ChangeEvent this model (re)uses to call its
      ChangeListeners. */
  ChangeEvent changeEvent;

  /** The group this model belongs to. Only one button in a group may be
      selected at any given time. */
  ButtonGroup group;
  
  /** The key code (one of {@link java.awt.event.KeyEvent} VK_*) used to
      press this button via a keyboard interface. */
  int mnemonic;

  /** The string used as the "command" property of any ActionEvent this
      model sends. */
  String actionCommand;

  public DefaultButtonModel()
  {
    stateMask = ENABLED;
    mnemonic = java.awt.event.KeyEvent.VK_UNDEFINED;
    listenerList = new EventListenerList();    
    changeEvent = new ChangeEvent(this);
  }

  /**
   * Return <code>null</code>. Use {@link AbstractButton} if you wish to
   * interface with a button via an {@link ItemSelectable} interface.
   *
   * @return <code>null</code>
   */
    public Object[] getSelectedObjects()
    {
	return null;
    }

  /**
   * Add an ActionListener to the model. Usually only called to subscribe
   * an AbstractButton's listener to the model.
   *
   * @param l The listener to add
   */
  public void addActionListener(ActionListener l)
  {
    listenerList.add(ActionListener.class, l);
  }
  
  /**
   * Remove an ActionListener to the model. Usually only called to
   * unsubscribe an AbstractButton's listener to the model.
   *
   * @param l The listener to remove
   */
  public void removeActionListener(ActionListener l)
  {
    listenerList.remove(ActionListener.class, l);
  }

  /**
   * Add an ItemListener to the model. Usually only called to subscribe
   * an AbstractButton's listener to the model.
   *
   * @param l The listener to add
   */
  public void addItemListener(ItemListener l)
  {
    listenerList.add(ItemListener.class, l);
  }

  /**
   * Remove an ItemListener to the model. Usually only called to
   * unsubscribe an AbstractButton's listener to the model.
   *
   * @param l The listener to remove
   */
  public void removeItemListener(ItemListener l)
  {
    listenerList.remove(ItemListener.class, l);
  }

  /**
   * Add a ChangeListener to the model. Usually only called to subscribe
   * an AbstractButton's listener to the model.
   *
   * @param l The listener to add
   */
  public void addChangeListener(ChangeListener l)
  {
    listenerList.add(ChangeListener.class, l);
  }

  /**
   * Remove a ChangeListener to the model. Usually only called to
   * unsubscribe an AbstractButton's listener to the model.
   *
   * @param l The listener to remove
   */
  public void removeChangeListener(ChangeListener l)
  {
    listenerList.remove(ChangeListener.class, l);
  }

  /**
   * Inform each ItemListener in the {@link listenerList} that an ItemEvent
   * has occurred. This happens in response to any change to the {@link
   * stateMask} field.
   *
   * @param e The ItemEvent to fire
   */
  public void fireItemStateChanged(ItemEvent e)
  {
    EventListener[] ll = listenerList.getListeners(ItemListener.class);
    for (int i = 0; i < ll.length; i++)
      ((ItemListener)ll[i]).itemStateChanged(e);
  }

  /**
   * Inform each ActionListener in the {@link listenerList} that an
   * ActionEvent has occurred. This happens in response to the any change
   * to the {@link stateMask} field which makes the enabled, armed and
   * pressed properties all simultaneously <code>true</code>.
   *
   * @param e The ActionEvent to fire
   */
  public void fireActionPerformed(ActionEvent e)
  {
    EventListener[] ll = listenerList.getListeners(ActionListener.class);
    for (int i = 0; i < ll.length; i++)
      ((ActionListener)ll[i]).actionPerformed(e);
  }

  /**
   * Inform each ChangeListener in the {@link listenerList} that a
   * ChangeEvent has occurred. This happens in response to the any change
   * to a property of the model.
   *
   * @param event The ChangeEvent to fire
   */
  public void fireStateChanged(ChangeEvent e)
  {
    EventListener[] ll = listenerList.getListeners(ChangeListener.class);
    for (int i = 0; i < ll.length; i++)
      ((ChangeListener)ll[i]).stateChanged(e);
  }

  /**
   * Helper method to fire a ChangeEvent with the model as the event's
   * source.
   */
  protected void changeState(int stateflag, boolean b)
    {
    int oldstate = stateMask;
    int newstate;

    if (b)
      newstate = oldstate | stateflag;
    else
      newstate = oldstate & ~stateflag;

    if (oldstate == newstate)
      return;

    if ((stateflag != SELECTED) 
        && (stateflag != ENABLED)
        && (stateMask & ENABLED) == 0)
      return;

    stateMask = newstate;

    fireStateChanged(changeEvent);

    if ((oldstate & SELECTED) == 0
        && (newstate & SELECTED) == SELECTED)
      fireItemStateChanged(new ItemEvent(this, ItemEvent.ITEM_STATE_CHANGED, 
                                         null, ItemEvent.SELECTED));

    else if ((oldstate & SELECTED) == SELECTED
             && (newstate & SELECTED) == 0)
      fireItemStateChanged(new ItemEvent(this, ItemEvent.ITEM_STATE_CHANGED, 
                                         null, ItemEvent.DESELECTED));
    
    else if (((oldstate & ARMED) == ARMED && (oldstate & PRESSED) == PRESSED)
             &&
             ((newstate & ARMED) == ARMED && (newstate & PRESSED) == 0))
      {
        fireActionPerformed(new ActionEvent(this, ActionEvent.ACTION_PERFORMED,
                                            actionCommand));
      }
    }
  
  /**
   * Get the value of the model's "armed" property.
   * 
   * @return The current "armed" property 
   */
  public boolean isArmed()
  {
    return (stateMask & ARMED) == ARMED;
  }
  
  /**
   * Set the value of the model's "armed" property.
   *
   * @param a The new "armed" property
   */
  public void setArmed(boolean a)
  {
    changeState(ARMED, a);
  }

  /**
   * Get the value of the model's "enabled" property.
   *
   * @return The current "enabled" property.
   */
  public boolean isEnabled()
    {
    return (stateMask & ENABLED) == ENABLED;
    }

  /**
   * Set the value of the model's "enabled" property.
   *
   * @param e The new "enabled" property
   */
  public void setEnabled(boolean e)
  {
    changeState(ENABLED, e);
  }

  /**
   * Set the value of the model's "pressed" property.
   *
   * @param p The new "pressed" property
   */
  public void setPressed(boolean p)
    {	
    changeState(PRESSED, p);
    }

  /**
   * Get the value of the model's "pressed" property.
   *
   * @return The current "pressed" property
   */
  public boolean isPressed()
  {
    return (stateMask & PRESSED) == PRESSED;
  }

  /**
   * Set the value of the model's "rollover" property.
   *
   * @param r The new "rollover" property
   */
  public void setRollover(boolean r)
  {
    changeState(ROLLOVER, r);
  }


  /**
   * Set the value of the model's "selected" property.
   *
   * @param s The new "selected" property
   */
  public void setSelected(boolean s)
  {
    changeState(SELECTED, s);
  }

  /**
   * Get the value of the model's "selected" property.
   *
   * @return The current "selected" property
   */
  public boolean isSelected()
  {
    return (stateMask & SELECTED) == SELECTED;
  }

  /**
   * Get the value of the model's "rollover" property.
   *
   * @return The current "rollover" property
   */
  public boolean isRollover()
    {
    return (stateMask & ROLLOVER) == ROLLOVER;
    }

  /**
   * Get the value of the model's "mnemonic" property.
   *
   * @return The current "mnemonic" property
   */
  public int getMnemonic()
  { 
    return mnemonic;
  }

  /**
   * Set the value of the model's "mnemonic" property.
   *
   * @param key The new "mnemonic" property
   */
  public void setMnemonic(int key)
  {
    if (mnemonic != key)
      {
        mnemonic = key;
        fireStateChanged(changeEvent);
      }
  }
  
  /**
   * Set the value of the model's "actionCommand" property. This property
   * is used as the "command" property of the {@link ActionEvent} fired
   * from the model.
   *
   * @param s The new "actionCommand" property.
   */
  public void setActionCommand(String s)
  {
    if (actionCommand != s)
      {
        actionCommand = s;
        fireStateChanged(changeEvent);
      }
  } 
  
  /**
   * Set the value of the model's "actionCommand" property. This property
   * is used as the "command" property of the {@link ActionEvent} fired
   * from the model.
   *
   * @return The current "actionCommand" property
   */
  public String getActionCommand()
  {
    return actionCommand;
  }

  /**
   * Set the value of the model's "group" property. The model is said to be
   * a member of the {@link ButtonGroup} held in its "group" property, and
   * only one models in a given group can have their "selected" property be
   * <code>true</code> at a time.
   *
   * @param g The new "group" property
   */
  public void setGroup(ButtonGroup g)
  {
    if (group != g)
      {
        group = g;
        fireStateChanged(changeEvent);
      }
  }
}