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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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package com.sun.java.accessibility.util;

import java.util.*;
import java.beans.*;
import java.awt.*;
import java.awt.event.*;
import javax.accessibility.*;


AccessibilityEventMonitor implements a PropertyChange listener on every UI object that implements interface Accessible in the Java Virtual Machine. The events captured by these listeners are made available through listeners supported by AccessibilityEventMonitor. With this, all the individual events on each of the UI object instances are funneled into one set of PropertyChange listeners. 
This class depends upon EventQueueMonitor, which provides the base level support for capturing the top-level containers as they are created. 
/**
 * <P>{@code AccessibilityEventMonitor} implements a PropertyChange listener
 * on every UI object that implements interface {@code Accessible} in the Java
 * Virtual Machine.  The events captured by these listeners are made available
 * through listeners supported by {@code AccessibilityEventMonitor}.
 * With this, all the individual events on each of the UI object
 * instances are funneled into one set of PropertyChange listeners.
 * <p>This class depends upon {@link EventQueueMonitor}, which provides the base
 * level support for capturing the top-level containers as they are created.
 *
 */

public class AccessibilityEventMonitor {

    // listeners
    
The current list of registered 
PropertyChangeListener classes. 
See Also:
/**
     * The current list of registered {@link java.beans.PropertyChangeListener
     * PropertyChangeListener} classes.
     *
     * @see #addPropertyChangeListener
     * @see #removePropertyChangeListener
     */
    static protected final AccessibilityListenerList listenerList =
        new AccessibilityListenerList();


    
The actual listener that is installed on the component instances.
This listener calls the other registered listeners when an event
occurs.  By doing things this way, the actual number of listeners
installed on a component instance is drastically reduced.

/**
     * The actual listener that is installed on the component instances.
     * This listener calls the other registered listeners when an event
     * occurs.  By doing things this way, the actual number of listeners
     * installed on a component instance is drastically reduced.
     */
    static private final AccessibilityEventListener accessibilityListener =
        new AccessibilityEventListener();

    
Adds the specified listener to receive all PropertyChange events on
each UI object instance in the Java Virtual Machine as they occur.

Note: This listener is automatically added to all component
instances created after this method is called.  In addition, it
is only added to UI object instances that support this listener type.

Params:
  • l – the listener to add
See Also:
/**
     * Adds the specified listener to receive all PropertyChange events on
     * each UI object instance in the Java Virtual Machine as they occur.
     * <P>Note: This listener is automatically added to all component
     * instances created after this method is called.  In addition, it
     * is only added to UI object instances that support this listener type.
     *
     * @param l the listener to add
     *
     * @see #removePropertyChangeListener
     */
    static public void addPropertyChangeListener(PropertyChangeListener l) {
        if (listenerList.getListenerCount(PropertyChangeListener.class) == 0) {
            accessibilityListener.installListeners();
        }
        listenerList.add(PropertyChangeListener.class, l);
    }

    
Removes the specified listener so it no longer receives PropertyChange
events when they occur.

Params:
  • l – the listener to remove
See Also:
  • addPropertyChangeListener
/**
     * Removes the specified listener so it no longer receives PropertyChange
     * events when they occur.
     * @see #addPropertyChangeListener
     * @param l the listener to remove
     */
    static public void removePropertyChangeListener(PropertyChangeListener l) {
        listenerList.remove(PropertyChangeListener.class, l);
        if (listenerList.getListenerCount(PropertyChangeListener.class) == 0) {
            accessibilityListener.removeListeners();
        }
    }


    
AccessibilityEventListener is the class that does all the work for
AccessibilityEventMonitor.  It is not intended for use by any other
class except AccessibilityEventMonitor.

/**
     * AccessibilityEventListener is the class that does all the work for
     * AccessibilityEventMonitor.  It is not intended for use by any other
     * class except AccessibilityEventMonitor.
     *
     */

    static class AccessibilityEventListener implements TopLevelWindowListener,
                PropertyChangeListener {

        
Create a new instance of this class and install it on each component
instance in the virtual machine that supports any of the currently
registered listeners in AccessibilityEventMonitor.  Also registers
itself as a TopLevelWindowListener with EventQueueMonitor so it can
automatically add new listeners to new components.

See Also:
/**
         * Create a new instance of this class and install it on each component
         * instance in the virtual machine that supports any of the currently
         * registered listeners in AccessibilityEventMonitor.  Also registers
         * itself as a TopLevelWindowListener with EventQueueMonitor so it can
         * automatically add new listeners to new components.
         * @see EventQueueMonitor
         * @see AccessibilityEventMonitor
         */
        public AccessibilityEventListener() {
            EventQueueMonitor.addTopLevelWindowListener(this);
        }

        
Installs PropertyChange listeners on all Accessible objects based
upon the current topLevelWindows cached by EventQueueMonitor.

See Also:
/**
         * Installs PropertyChange listeners on all Accessible objects based
         * upon the current topLevelWindows cached by EventQueueMonitor.
         * @see EventQueueMonitor
         * @see AWTEventMonitor
         */
        protected void installListeners() {
            Window topLevelWindows[] = EventQueueMonitor.getTopLevelWindows();
            if (topLevelWindows != null) {
                for (int i = 0; i < topLevelWindows.length; i++) {
                    if (topLevelWindows[i] instanceof Accessible) {
                        installListeners((Accessible) topLevelWindows[i]);
                    }
                }
            }
        }

        
Installs PropertyChange listeners to the Accessible object, and it's
children (so long as the object isn't of TRANSIENT state).

Params:
  • a – the Accessible object to add listeners to
/**
         * Installs PropertyChange listeners to the Accessible object, and it's
         * children (so long as the object isn't of TRANSIENT state).
         * @param a the Accessible object to add listeners to
         */
        protected void installListeners(Accessible a) {
            installListeners(a.getAccessibleContext());
        }

        
Installs PropertyChange listeners to the AccessibleContext object,
and it's * children (so long as the object isn't of TRANSIENT state).

Params:
  • a – the Accessible object to add listeners to
/**
         * Installs PropertyChange listeners to the AccessibleContext object,
         * and it's * children (so long as the object isn't of TRANSIENT state).
         * @param a the Accessible object to add listeners to
         */
        private void installListeners(AccessibleContext ac) {

            if (ac != null) {
                AccessibleStateSet states = ac.getAccessibleStateSet();
                if (!states.contains(AccessibleState.TRANSIENT)) {
                    ac.addPropertyChangeListener(this);
                    /*
                     * Don't add listeners to transient children. Components
                     * with transient children should return an AccessibleStateSet
                     * containing AccessibleState.MANAGES_DESCENDANTS. Components
                     * may not explicitly return the MANAGES_DESCENDANTS state.
                     * In this case, don't add listeners to the children of
                     * lists, tables and trees.
                     */
                    AccessibleStateSet set = ac.getAccessibleStateSet();
                    if (set.contains(_AccessibleState.MANAGES_DESCENDANTS)) {
                        return;
                    }
                    AccessibleRole role = ac.getAccessibleRole();
                    if (role == AccessibleRole.LIST ||
                        role == AccessibleRole.TREE) {
                        return;
                    }
                    if (role == AccessibleRole.TABLE) {
                        // handle Oracle tables containing tables
                        Accessible child = ac.getAccessibleChild(0);
                        if (child != null) {
                            AccessibleContext ac2 = child.getAccessibleContext();
                            if (ac2 != null) {
                                role = ac2.getAccessibleRole();
                                if (role != null && role != AccessibleRole.TABLE) {
                                    return;
                                }
                            }
                        }
                    }
                    int count = ac.getAccessibleChildrenCount();
                    for (int i = 0; i < count; i++) {
                        Accessible child = ac.getAccessibleChild(i);
                        if (child != null) {
                            installListeners(child);
                        }
                    }
                }
            }
        }

        
Removes PropertyChange listeners on all Accessible objects based
upon the topLevelWindows cached by EventQueueMonitor.

Params:
  • eventID – the event ID
See Also:
/**
         * Removes PropertyChange listeners on all Accessible objects based
         * upon the topLevelWindows cached by EventQueueMonitor.
         * @param eventID the event ID
         * @see EventID
         */
        protected void removeListeners() {
            Window topLevelWindows[] = EventQueueMonitor.getTopLevelWindows();
            if (topLevelWindows != null) {
                for (int i = 0; i < topLevelWindows.length; i++) {
                    if (topLevelWindows[i] instanceof Accessible) {
                        removeListeners((Accessible) topLevelWindows[i]);
                    }
                }
            }
        }

        
Removes PropertyChange listeners for the given Accessible object,
it's children (so long as the object isn't of TRANSIENT state).

Params:
  • a – the Accessible object to remove listeners from
/**
         * Removes PropertyChange listeners for the given Accessible object,
         * it's children (so long as the object isn't of TRANSIENT state).
         * @param a the Accessible object to remove listeners from
         */
        protected void removeListeners(Accessible a) {
            removeListeners(a.getAccessibleContext());
        }

        
Removes PropertyChange listeners for the given AccessibleContext
object, it's children (so long as the object isn't of TRANSIENT
state).

Params:
  • a – the Accessible object to remove listeners from
/**
         * Removes PropertyChange listeners for the given AccessibleContext
         * object, it's children (so long as the object isn't of TRANSIENT
         * state).
         * @param a the Accessible object to remove listeners from
         */
        private void removeListeners(AccessibleContext ac) {


            if (ac != null) {
                // Listeners are not added to transient components.
                AccessibleStateSet states = ac.getAccessibleStateSet();
                if (!states.contains(AccessibleState.TRANSIENT)) {
                    ac.removePropertyChangeListener(this);
                    /*
                     * Listeners are not added to transient children. Components
                     * with transient children should return an AccessibleStateSet
                     * containing AccessibleState.MANAGES_DESCENDANTS. Components
                     * may not explicitly return the MANAGES_DESCENDANTS state.
                     * In this case, don't remove listeners from the children of
                     * lists, tables and trees.
                     */
                    if (states.contains(_AccessibleState.MANAGES_DESCENDANTS)) {
                        return;
                    }
                    AccessibleRole role = ac.getAccessibleRole();
                    if (role == AccessibleRole.LIST ||
                        role == AccessibleRole.TABLE ||
                        role == AccessibleRole.TREE) {
                        return;
                    }
                    int count = ac.getAccessibleChildrenCount();
                    for (int i = 0; i < count; i++) {
                        Accessible child = ac.getAccessibleChild(i);
                        if (child != null) {
                            removeListeners(child);
                        }
                    }
                }
            }
        }

        /********************************************************************/
        /*                                                                  */
        /* Listener Interface Methods                                       */
        /*                                                                  */
        /********************************************************************/

        /* TopLevelWindow Methods ***************************************/

        
Called when top level window is created.

See Also:
/**
         * Called when top level window is created.
         * @see EventQueueMonitor
         * @see EventQueueMonitor#addTopLevelWindowListener
         */
        public void topLevelWindowCreated(Window w) {
            if (w instanceof Accessible) {
                installListeners((Accessible) w);
            }
        }

        
Called when top level window is destroyed.

See Also:
/**
         * Called when top level window is destroyed.
         * @see EventQueueMonitor
         * @see EventQueueMonitor#addTopLevelWindowListener
         */
        public void topLevelWindowDestroyed(Window w) {
            if (w instanceof Accessible) {
                removeListeners((Accessible) w);
            }
        }


        /* PropertyChangeListener Methods **************************************/

        public void propertyChange(PropertyChangeEvent e) {
            // propogate the event
            Object[] listeners =
                    AccessibilityEventMonitor.listenerList.getListenerList();
            for (int i = listeners.length-2; i>=0; i-=2) {
                if (listeners[i]==PropertyChangeListener.class) {
                    ((PropertyChangeListener)listeners[i+1]).propertyChange(e);
                }
            }

            // handle childbirth/death
            String name = e.getPropertyName();
            if (name.compareTo(AccessibleContext.ACCESSIBLE_CHILD_PROPERTY) == 0) {
                Object oldValue = e.getOldValue();
                Object newValue = e.getNewValue();

                if ((oldValue == null) ^ (newValue == null)) { // one null, not both
                    if (oldValue != null) {
                        // this Accessible is a child that's going away
                        if (oldValue instanceof Accessible) {
                            Accessible a = (Accessible) oldValue;
                            removeListeners(a.getAccessibleContext());
                        } else if (oldValue instanceof AccessibleContext) {
                            removeListeners((AccessibleContext) oldValue);
                        }
                    } else if (newValue != null) {
                        // this Accessible is a child was just born
                        if (newValue instanceof Accessible) {
                            Accessible a = (Accessible) newValue;
                            installListeners(a.getAccessibleContext());
                        } else if (newValue instanceof AccessibleContext) {
                            installListeners((AccessibleContext) newValue);
                        }
                    }
                } else {
                    System.out.println("ERROR in usage of PropertyChangeEvents for: " + e.toString());
                }
            }
        }
    }
}

/*
 * workaround for no public AccessibleState constructor
 */
class _AccessibleState extends AccessibleState {
    
Indicates this object is responsible for managing its
subcomponents.  This is typically used for trees and tables
that have a large number of subcomponents and where the
objects are created only when needed and otherwise remain virtual.
The application should not manage the subcomponents directly.

/**
     * Indicates this object is responsible for managing its
     * subcomponents.  This is typically used for trees and tables
     * that have a large number of subcomponents and where the
     * objects are created only when needed and otherwise remain virtual.
     * The application should not manage the subcomponents directly.
     */
    public static final _AccessibleState MANAGES_DESCENDANTS
        = new _AccessibleState ("managesDescendants");

    
Creates a new AccessibleState using the given locale independent key.
This should not be a public method.  Instead, it is used to create
the constants in this file to make it a strongly typed enumeration.
Subclasses of this class should enforce similar policy.


The key String should be a locale independent key for the state.
It is not intended to be used as the actual String to display
to the user.  To get the localized string, use toDisplayString.

Params:
  • key – the locale independent name of the state.
See Also:
/**
     * Creates a new AccessibleState using the given locale independent key.
     * This should not be a public method.  Instead, it is used to create
     * the constants in this file to make it a strongly typed enumeration.
     * Subclasses of this class should enforce similar policy.
     * <p>
     * The key String should be a locale independent key for the state.
     * It is not intended to be used as the actual String to display
     * to the user.  To get the localized string, use toDisplayString.
     *
     * @param key the locale independent name of the state.
     * @see AccessibleBundle#toDisplayString
     */
    protected _AccessibleState(String key) {
        super(key);
    }
}