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public static interface

AbstractDocument.Content

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
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package javax.swing.text;

import java.util.*;
import java.io.*;
import java.awt.font.TextAttribute;
import java.text.Bidi;

import javax.swing.UIManager;
import javax.swing.undo.*;
import javax.swing.event.ChangeListener;
import javax.swing.event.*;
import javax.swing.tree.TreeNode;

import sun.font.BidiUtils;
import sun.swing.SwingUtilities2;

/**
 * An implementation of the document interface to serve as a
 * basis for implementing various kinds of documents.  At this
 * level there is very little policy, so there is a corresponding
 * increase in difficulty of use.
 * <p>
 * This class implements a locking mechanism for the document.  It
 * allows multiple readers or one writer, and writers must wait until
 * all observers of the document have been notified of a previous
 * change before beginning another mutation to the document.  The
 * read lock is acquired and released using the <code>render</code>
 * method.  A write lock is aquired by the methods that mutate the
 * document, and are held for the duration of the method call.
 * Notification is done on the thread that produced the mutation,
 * and the thread has full read access to the document for the
 * duration of the notification, but other readers are kept out
 * until the notification has finished.  The notification is a
 * beans event notification which does not allow any further
 * mutations until all listeners have been notified.
 * <p>
 * Any models subclassed from this class and used in conjunction
 * with a text component that has a look and feel implementation
 * that is derived from BasicTextUI may be safely updated
 * asynchronously, because all access to the View hierarchy
 * is serialized by BasicTextUI if the document is of type
 * <code>AbstractDocument</code>.  The locking assumes that an
 * independent thread will access the View hierarchy only from
 * the DocumentListener methods, and that there will be only
 * one event thread active at a time.
 * <p>
 * If concurrency support is desired, there are the following
 * additional implications.  The code path for any DocumentListener
 * implementation and any UndoListener implementation must be threadsafe,
 * and not access the component lock if trying to be safe from deadlocks.
 * The <code>repaint</code> and <code>revalidate</code> methods
 * on JComponent are safe.
 * <p>
 * AbstractDocument models an implied break at the end of the document.
 * Among other things this allows you to position the caret after the last
 * character. As a result of this, <code>getLength</code> returns one less
 * than the length of the Content. If you create your own Content, be
 * sure and initialize it to have an additional character. Refer to
 * StringContent and GapContent for examples of this. Another implication
 * of this is that Elements that model the implied end character will have
 * an endOffset == (getLength() + 1). For example, in DefaultStyledDocument
 * <code>getParagraphElement(getLength()).getEndOffset() == getLength() + 1
 * </code>.
 * <p>
 * <strong>Warning:</strong>
 * Serialized objects of this class will not be compatible with
 * future Swing releases. The current serialization support is
 * appropriate for short term storage or RMI between applications running
 * the same version of Swing.  As of 1.4, support for long term storage
 * of all JavaBeans<sup><font size="-2">TM</font></sup>
 * has been added to the <code>java.beans</code> package.
 * Please see {@link java.beans.XMLEncoder}.
 *
 * @author  Timothy Prinzing
 */

public abstract class AbstractDocument implements Document, Serializable {

   
/**
     * Constructs a new <code>AbstractDocument</code>, wrapped around some
     * specified content storage mechanism.
     *
     * @param data the content
     */

   
protected AbstractDocument(Content data) {
       
this(data, StyleContext.getDefaultStyleContext());
   
}

   
/**
     * Constructs a new <code>AbstractDocument</code>, wrapped around some
     * specified content storage mechanism.
     *
     * @param data the content
     * @param context the attribute context
     */

   
protected AbstractDocument(Content data, AttributeContext context) {
       
this.data = data;
       
this.context = context;
        bidiRoot
= new BidiRootElement();

       
if (defaultI18NProperty == null) {
           
// determine default setting for i18n support
           
Object o = java.security.AccessController.doPrivileged(
               
new java.security.PrivilegedAction() {
                   
public Object run() {
                       
return System.getProperty(I18NProperty);
                   
}
               
}
           
);
           
if (o != null) {
                defaultI18NProperty
= Boolean.valueOf((String)o);
           
} else {
                defaultI18NProperty
= Boolean.FALSE;
           
}
       
}
        putProperty
( I18NProperty, defaultI18NProperty);

       
//REMIND(bcb) This creates an initial bidi element to account for
       
//the \n that exists by default in the content.  Doing it this way
       
//seems to expose a little too much knowledge of the content given
       
//to us by the sub-class.  Consider having the sub-class' constructor
       
//make an initial call to insertUpdate.
        writeLock
();
       
try {
           
Element[] p = new Element[1];
            p
[0] = new BidiElement( bidiRoot, 0, 1, 0 );
            bidiRoot
.replace(0,0,p);
       
} finally {
            writeUnlock
();
       
}
   
}

   
/**
     * Supports managing a set of properties. Callers
     * can use the <code>documentProperties</code> dictionary
     * to annotate the document with document-wide properties.
     *
     * @return a non-<code>null</code> <code>Dictionary</code>
     * @see #setDocumentProperties
     */

   
public Dictionary<Object,Object> getDocumentProperties() {
       
if (documentProperties == null) {
            documentProperties
= new Hashtable(2);
       
}
       
return documentProperties;
   
}

   
/**
     * Replaces the document properties dictionary for this document.
     *
     * @param x the new dictionary
     * @see #getDocumentProperties
     */

   
public void setDocumentProperties(Dictionary<Object,Object> x) {
        documentProperties
= x;
   
}

   
/**
     * Notifies all listeners that have registered interest for
     * notification on this event type.  The event instance
     * is lazily created using the parameters passed into
     * the fire method.
     *
     * @param e the event
     * @see EventListenerList
     */

   
protected void fireInsertUpdate(DocumentEvent e) {
        notifyingListeners
= true;
       
try {
           
// Guaranteed to return a non-null array
           
Object[] listeners = listenerList.getListenerList();
           
// Process the listeners last to first, notifying
           
// those that are interested in this event
           
for (int i = listeners.length-2; i>=0; i-=2) {
               
if (listeners[i]==DocumentListener.class) {
                   
// Lazily create the event:
                   
// if (e == null)
                   
// e = new ListSelectionEvent(this, firstIndex, lastIndex);
                   
((DocumentListener)listeners[i+1]).insertUpdate(e);
               
}
           
}
       
} finally {
            notifyingListeners
= false;
       
}
   
}

   
/**
     * Notifies all listeners that have registered interest for
     * notification on this event type.  The event instance
     * is lazily created using the parameters passed into
     * the fire method.
     *
     * @param e the event
     * @see EventListenerList
     */

   
protected void fireChangedUpdate(DocumentEvent e) {
        notifyingListeners
= true;
       
try {
           
// Guaranteed to return a non-null array
           
Object[] listeners = listenerList.getListenerList();
           
// Process the listeners last to first, notifying
           
// those that are interested in this event
           
for (int i = listeners.length-2; i>=0; i-=2) {
               
if (listeners[i]==DocumentListener.class) {
                   
// Lazily create the event:
                   
// if (e == null)
                   
// e = new ListSelectionEvent(this, firstIndex, lastIndex);
                   
((DocumentListener)listeners[i+1]).changedUpdate(e);
               
}
           
}
       
} finally {
            notifyingListeners
= false;
       
}
   
}

   
/**
     * Notifies all listeners that have registered interest for
     * notification on this event type.  The event instance
     * is lazily created using the parameters passed into
     * the fire method.
     *
     * @param e the event
     * @see EventListenerList
     */

   
protected void fireRemoveUpdate(DocumentEvent e) {
        notifyingListeners
= true;
       
try {
           
// Guaranteed to return a non-null array
           
Object[] listeners = listenerList.getListenerList();
           
// Process the listeners last to first, notifying
           
// those that are interested in this event
           
for (int i = listeners.length-2; i>=0; i-=2) {
               
if (listeners[i]==DocumentListener.class) {
                   
// Lazily create the event:
                   
// if (e == null)
                   
// e = new ListSelectionEvent(this, firstIndex, lastIndex);
                   
((DocumentListener)listeners[i+1]).removeUpdate(e);
               
}
           
}
       
} finally {
            notifyingListeners
= false;
       
}
   
}

   
/**
     * Notifies all listeners that have registered interest for
     * notification on this event type.  The event instance
     * is lazily created using the parameters passed into
     * the fire method.
     *
     * @param e the event
     * @see EventListenerList
     */

   
protected void fireUndoableEditUpdate(UndoableEditEvent e) {
       
// Guaranteed to return a non-null array
       
Object[] listeners = listenerList.getListenerList();
       
// Process the listeners last to first, notifying
       
// those that are interested in this event
       
for (int i = listeners.length-2; i>=0; i-=2) {
           
if (listeners[i]==UndoableEditListener.class) {
               
// Lazily create the event:
               
// if (e == null)
               
// e = new ListSelectionEvent(this, firstIndex, lastIndex);
               
((UndoableEditListener)listeners[i+1]).undoableEditHappened(e);
           
}
       
}
   
}

   
/**
     * Returns an array of all the objects currently registered
     * as <code><em>Foo</em>Listener</code>s
     * upon this document.
     * <code><em>Foo</em>Listener</code>s are registered using the
     * <code>add<em>Foo</em>Listener</code> method.
     *
     * <p>
     * You can specify the <code>listenerType</code> argument
     * with a class literal, such as
     * <code><em>Foo</em>Listener.class</code>.
     * For example, you can query a
     * document <code>d</code>
     * for its document listeners with the following code:
     *
     * <pre>DocumentListener[] mls = (DocumentListener[])(d.getListeners(DocumentListener.class));</pre>
     *
     * If no such listeners exist, this method returns an empty array.
     *
     * @param listenerType the type of listeners requested; this parameter
     *          should specify an interface that descends from
     *          <code>java.util.EventListener</code>
     * @return an array of all objects registered as
     *          <code><em>Foo</em>Listener</code>s on this component,
     *          or an empty array if no such
     *          listeners have been added
     * @exception ClassCastException if <code>listenerType</code>
     *          doesn't specify a class or interface that implements
     *          <code>java.util.EventListener</code>
     *
     * @see #getDocumentListeners
     * @see #getUndoableEditListeners
     *
     * @since 1.3
     */

   
public <T extends EventListener> T[] getListeners(Class<T> listenerType) {
       
return listenerList.getListeners(listenerType);
   
}

   
/**
     * Gets the asynchronous loading priority.  If less than zero,
     * the document should not be loaded asynchronously.
     *
     * @return the asynchronous loading priority, or <code>-1</code>
     *   if the document should not be loaded asynchronously
     */

   
public int getAsynchronousLoadPriority() {
       
Integer loadPriority = (Integer)
            getProperty
(AbstractDocument.AsyncLoadPriority);
       
if (loadPriority != null) {
           
return loadPriority.intValue();
       
}
       
return -1;
   
}

   
/**
     * Sets the asynchronous loading priority.
     * @param p the new asynchronous loading priority; a value
     *   less than zero indicates that the document should not be
     *   loaded asynchronously
     */

   
public void setAsynchronousLoadPriority(int p) {
       
Integer loadPriority = (p >= 0) ? new Integer(p) : null;
        putProperty
(AbstractDocument.AsyncLoadPriority, loadPriority);
   
}

   
/**
     * Sets the <code>DocumentFilter</code>. The <code>DocumentFilter</code>
     * is passed <code>insert</code> and <code>remove</code> to conditionally
     * allow inserting/deleting of the text.  A <code>null</code> value
     * indicates that no filtering will occur.
     *
     * @param filter the <code>DocumentFilter</code> used to constrain text
     * @see #getDocumentFilter
     * @since 1.4
     */

   
public void setDocumentFilter(DocumentFilter filter) {
        documentFilter
= filter;
   
}

   
/**
     * Returns the <code>DocumentFilter</code> that is responsible for
     * filtering of insertion/removal. A <code>null</code> return value
     * implies no filtering is to occur.
     *
     * @since 1.4
     * @see #setDocumentFilter
     * @return the DocumentFilter
     */

   
public DocumentFilter getDocumentFilter() {
       
return documentFilter;
   
}

   
// --- Document methods -----------------------------------------

   
/**
     * This allows the model to be safely rendered in the presence
     * of currency, if the model supports being updated asynchronously.
     * The given runnable will be executed in a way that allows it
     * to safely read the model with no changes while the runnable
     * is being executed.  The runnable itself may <em>not</em>
     * make any mutations.
     * <p>
     * This is implemented to aquire a read lock for the duration
     * of the runnables execution.  There may be multiple runnables
     * executing at the same time, and all writers will be blocked
     * while there are active rendering runnables.  If the runnable
     * throws an exception, its lock will be safely released.
     * There is no protection against a runnable that never exits,
     * which will effectively leave the document locked for it's
     * lifetime.
     * <p>
     * If the given runnable attempts to make any mutations in
     * this implementation, a deadlock will occur.  There is
     * no tracking of individual rendering threads to enable
     * detecting this situation, but a subclass could incur
     * the overhead of tracking them and throwing an error.
     * <p>
     * This method is thread safe, although most Swing methods
     * are not. Please see
     * <A HREF="http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html">How
     * to Use Threads</A> for more information.
     *
     * @param r the renderer to execute
     */

   
public void render(Runnable r) {
        readLock
();
       
try {
            r
.run();
       
} finally {
            readUnlock
();
       
}
   
}

   
/**
     * Returns the length of the data.  This is the number of
     * characters of content that represents the users data.
     *
     * @return the length >= 0
     * @see Document#getLength
     */

   
public int getLength() {
       
return data.length() - 1;
   
}

   
/**
     * Adds a document listener for notification of any changes.
     *
     * @param listener the <code>DocumentListener</code> to add
     * @see Document#addDocumentListener
     */

   
public void addDocumentListener(DocumentListener listener) {
        listenerList
.add(DocumentListener.class, listener);
   
}

   
/**
     * Removes a document listener.
     *
     * @param listener the <code>DocumentListener</code> to remove
     * @see Document#removeDocumentListener
     */

   
public void removeDocumentListener(DocumentListener listener) {
        listenerList
.remove(DocumentListener.class, listener);
   
}

   
/**
     * Returns an array of all the document listeners
     * registered on this document.
     *
     * @return all of this document's <code>DocumentListener</code>s
     *         or an empty array if no document listeners are
     *         currently registered
     *
     * @see #addDocumentListener
     * @see #removeDocumentListener
     * @since 1.4
     */

   
public DocumentListener[] getDocumentListeners() {
       
return (DocumentListener[])listenerList.getListeners(
               
DocumentListener.class);
   
}

   
/**
     * Adds an undo listener for notification of any changes.
     * Undo/Redo operations performed on the <code>UndoableEdit</code>
     * will cause the appropriate DocumentEvent to be fired to keep
     * the view(s) in sync with the model.
     *
     * @param listener the <code>UndoableEditListener</code> to add
     * @see Document#addUndoableEditListener
     */

   
public void addUndoableEditListener(UndoableEditListener listener) {
        listenerList
.add(UndoableEditListener.class, listener);
   
}

   
/**
     * Removes an undo listener.
     *
     * @param listener the <code>UndoableEditListener</code> to remove
     * @see Document#removeDocumentListener
     */

   
public void removeUndoableEditListener(UndoableEditListener listener) {
        listenerList
.remove(UndoableEditListener.class, listener);
   
}

   
/**
     * Returns an array of all the undoable edit listeners
     * registered on this document.
     *
     * @return all of this document's <code>UndoableEditListener</code>s
     *         or an empty array if no undoable edit listeners are
     *         currently registered
     *
     * @see #addUndoableEditListener
     * @see #removeUndoableEditListener
     *
     * @since 1.4
     */

   
public UndoableEditListener[] getUndoableEditListeners() {
       
return (UndoableEditListener[])listenerList.getListeners(
               
UndoableEditListener.class);
   
}

   
/**
     * A convenience method for looking up a property value. It is
     * equivalent to:
     * <pre>
     * getDocumentProperties().get(key);
     * </pre>
     *
     * @param key the non-<code>null</code> property key
     * @return the value of this property or <code>null</code>
     * @see #getDocumentProperties
     */

   
public final Object getProperty(Object key) {
       
return getDocumentProperties().get(key);
   
}


   
/**
     * A convenience method for storing up a property value.  It is
     * equivalent to:
     * <pre>
     * getDocumentProperties().put(key, value);
     * </pre>
     * If <code>value</code> is <code>null</code> this method will
     * remove the property.
     *
     * @param key the non-<code>null</code> key
     * @param value the property value
     * @see #getDocumentProperties
     */

   
public final void putProperty(Object key, Object value) {
       
if (value != null) {
            getDocumentProperties
().put(key, value);
       
} else {
            getDocumentProperties
().remove(key);
       
}
       
if( key == TextAttribute.RUN_DIRECTION
           
&& Boolean.TRUE.equals(getProperty(I18NProperty)) )
       
{
           
//REMIND - this needs to flip on the i18n property if run dir
           
//is rtl and the i18n property is not already on.
            writeLock
();
           
try {
               
DefaultDocumentEvent e
                   
= new DefaultDocumentEvent(0, getLength(),
                                               
DocumentEvent.EventType.INSERT);
                updateBidi
( e );
           
} finally {
                writeUnlock
();
           
}
       
}
   
}

   
/**
     * Removes some content from the document.
     * Removing content causes a write lock to be held while the
     * actual changes are taking place.  Observers are notified
     * of the change on the thread that called this method.
     * <p>
     * This method is thread safe, although most Swing methods
     * are not. Please see
     * <A HREF="http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html">How
     * to Use Threads</A> for more information.
     *
     * @param offs the starting offset >= 0
     * @param len the number of characters to remove >= 0
     * @exception BadLocationException  the given remove position is not a valid
     *   position within the document
     * @see Document#remove
     */

   
public void remove(int offs, int len) throws BadLocationException {
       
DocumentFilter filter = getDocumentFilter();

        writeLock
();
       
try {
           
if (filter != null) {
                filter
.remove(getFilterBypass(), offs, len);
           
}
           
else {
                handleRemove
(offs, len);
           
}
       
} finally {
            writeUnlock
();
       
}
   
}

   
/**
     * Performs the actual work of the remove. It is assumed the caller
     * will have obtained a <code>writeLock</code> before invoking this.
     */

   
void handleRemove(int offs, int len) throws BadLocationException {
       
if (len > 0) {
           
if (offs < 0 || (offs + len) > getLength()) {
               
throw new BadLocationException("Invalid remove",
                                               getLength
() + 1);
           
}
           
DefaultDocumentEvent chng =
                   
new DefaultDocumentEvent(offs, len, DocumentEvent.EventType.REMOVE);

           
boolean isComposedTextElement = false;
           
// Check whether the position of interest is the composed text
            isComposedTextElement
= Utilities.isComposedTextElement(this, offs);

            removeUpdate
(chng);
           
UndoableEdit u = data.remove(offs, len);
           
if (u != null) {
                chng
.addEdit(u);
           
}
            postRemoveUpdate
(chng);
           
// Mark the edit as done.
            chng
.end();
            fireRemoveUpdate
(chng);
           
// only fire undo if Content implementation supports it
           
// undo for the composed text is not supported for now
           
if ((u != null) && !isComposedTextElement) {
                fireUndoableEditUpdate
(new UndoableEditEvent(this, chng));
           
}
       
}
   
}

   
/**
     * Deletes the region of text from <code>offset</code> to
     * <code>offset + length</code>, and replaces it with <code>text</code>.
     * It is up to the implementation as to how this is implemented, some
     * implementations may treat this as two distinct operations: a remove
     * followed by an insert, others may treat the replace as one atomic
     * operation.
     *
     * @param offset index of child element
     * @param length length of text to delete, may be 0 indicating don't
     *               delete anything
     * @param text text to insert, <code>null</code> indicates no text to insert
     * @param attrs AttributeSet indicating attributes of inserted text,
     *              <code>null</code>
     *              is legal, and typically treated as an empty attributeset,
     *              but exact interpretation is left to the subclass
     * @exception BadLocationException the given position is not a valid
     *            position within the document
     * @since 1.4
     */

   
public void replace(int offset, int length, String text,
                       
AttributeSet attrs) throws BadLocationException {
       
if (length == 0 && (text == null || text.length() == 0)) {
           
return;
       
}
       
DocumentFilter filter = getDocumentFilter();

        writeLock
();
       
try {
           
if (filter != null) {
                filter
.replace(getFilterBypass(), offset, length, text,
                               attrs
);
           
}
           
else {
               
if (length > 0) {
                    remove
(offset, length);
               
}
               
if (text != null && text.length() > 0) {
                    insertString
(offset, text, attrs);
               
}
           
}
       
} finally {
            writeUnlock
();
       
}
   
}

   
/**
     * Inserts some content into the document.
     * Inserting content causes a write lock to be held while the
     * actual changes are taking place, followed by notification
     * to the observers on the thread that grabbed the write lock.
     * <p>
     * This method is thread safe, although most Swing methods
     * are not. Please see
     * <A HREF="http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html">How
     * to Use Threads</A> for more information.
     *
     * @param offs the starting offset >= 0
     * @param str the string to insert; does nothing with null/empty strings
     * @param a the attributes for the inserted content
     * @exception BadLocationException  the given insert position is not a valid
     *   position within the document
     * @see Document#insertString
     */

   
public void insertString(int offs, String str, AttributeSet a) throws BadLocationException {
       
if ((str == null) || (str.length() == 0)) {
           
return;
       
}
       
DocumentFilter filter = getDocumentFilter();

        writeLock
();
       
try {
           
if (filter != null) {
                filter
.insertString(getFilterBypass(), offs, str, a);
           
}
           
else {
                handleInsertString
(offs, str, a);
           
}
       
} finally {
            writeUnlock
();
       
}
   
}

   
/**
     * Performs the actual work of inserting the text; it is assumed the
     * caller has obtained a write lock before invoking this.
     */

   
void handleInsertString(int offs, String str, AttributeSet a)
                         
throws BadLocationException {
       
if ((str == null) || (str.length() == 0)) {
           
return;
       
}
       
UndoableEdit u = data.insertString(offs, str);
       
DefaultDocumentEvent e =
           
new DefaultDocumentEvent(offs, str.length(), DocumentEvent.EventType.INSERT);
       
if (u != null) {
            e
.addEdit(u);
       
}

       
// see if complex glyph layout support is needed
       
if( getProperty(I18NProperty).equals( Boolean.FALSE ) ) {
           
// if a default direction of right-to-left has been specified,
           
// we want complex layout even if the text is all left to right.
           
Object d = getProperty(TextAttribute.RUN_DIRECTION);
           
if ((d != null) && (d.equals(TextAttribute.RUN_DIRECTION_RTL))) {
                putProperty
( I18NProperty, Boolean.TRUE);
           
} else {
               
char[] chars = str.toCharArray();
               
if (SwingUtilities2.isComplexLayout(chars, 0, chars.length)) {
                    putProperty
( I18NProperty, Boolean.TRUE);
               
}
           
}
       
}

        insertUpdate
(e, a);
       
// Mark the edit as done.
        e
.end();
        fireInsertUpdate
(e);
       
// only fire undo if Content implementation supports it
       
// undo for the composed text is not supported for now
       
if (u != null &&
           
(a == null || !a.isDefined(StyleConstants.ComposedTextAttribute))) {
            fireUndoableEditUpdate
(new UndoableEditEvent(this, e));
       
}
   
}

   
/**
     * Gets a sequence of text from the document.
     *
     * @param offset the starting offset >= 0
     * @param length the number of characters to retrieve >= 0
     * @return the text
     * @exception BadLocationException  the range given includes a position
     *   that is not a valid position within the document
     * @see Document#getText
     */

   
public String getText(int offset, int length) throws BadLocationException {
       
if (length < 0) {
           
throw new BadLocationException("Length must be positive", length);
       
}
       
String str = data.getString(offset, length);
       
return str;
   
}

   
/**
     * Fetches the text contained within the given portion
     * of the document.
     * <p>
     * If the partialReturn property on the txt parameter is false, the
     * data returned in the Segment will be the entire length requested and
     * may or may not be a copy depending upon how the data was stored.
     * If the partialReturn property is true, only the amount of text that
     * can be returned without creating a copy is returned.  Using partial
     * returns will give better performance for situations where large
     * parts of the document are being scanned.  The following is an example
     * of using the partial return to access the entire document:
     * <p>
     * <pre>
     *   int nleft = doc.getDocumentLength();
     *   Segment text = new Segment();
     *   int offs = 0;
     *   text.setPartialReturn(true);
     *   while (nleft > 0) {
     *       doc.getText(offs, nleft, text);
     *       // do something with text
     *       nleft -= text.count;
     *       offs += text.count;
     *   }
     * </pre>
     *
     * @param offset the starting offset >= 0
     * @param length the number of characters to retrieve >= 0
     * @param txt the Segment object to retrieve the text into
     * @exception BadLocationException  the range given includes a position
     *   that is not a valid position within the document
     */

   
public void getText(int offset, int length, Segment txt) throws BadLocationException {
       
if (length < 0) {
           
throw new BadLocationException("Length must be positive", length);
       
}
        data
.getChars(offset, length, txt);
   
}

   
/**
     * Returns a position that will track change as the document
     * is altered.
     * <p>
     * This method is thread safe, although most Swing methods
     * are not. Please see
     * <A HREF="http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html">How
     * to Use Threads</A> for more information.
     *
     * @param offs the position in the model >= 0
     * @return the position
     * @exception BadLocationException  if the given position does not
     *   represent a valid location in the associated document
     * @see Document#createPosition
     */

   
public synchronized Position createPosition(int offs) throws BadLocationException {
       
return data.createPosition(offs);
   
}

   
/**
     * Returns a position that represents the start of the document.  The
     * position returned can be counted on to track change and stay
     * located at the beginning of the document.
     *
     * @return the position
     */

   
public final Position getStartPosition() {
       
Position p;
       
try {
            p
= createPosition(0);
       
} catch (BadLocationException bl) {
            p
= null;
       
}
       
return p;
   
}

   
/**
     * Returns a position that represents the end of the document.  The
     * position returned can be counted on to track change and stay
     * located at the end of the document.
     *
     * @return the position
     */

   
public final Position getEndPosition() {
       
Position p;
       
try {
            p
= createPosition(data.length());
       
} catch (BadLocationException bl) {
            p
= null;
       
}
       
return p;
   
}

   
/**
     * Gets all root elements defined.  Typically, there
     * will only be one so the default implementation
     * is to return the default root element.
     *
     * @return the root element
     */

   
public Element[] getRootElements() {
       
Element[] elems = new Element[2];
        elems
[0] = getDefaultRootElement();
        elems
[1] = getBidiRootElement();
       
return elems;
   
}

   
/**
     * Returns the root element that views should be based upon
     * unless some other mechanism for assigning views to element
     * structures is provided.
     *
     * @return the root element
     * @see Document#getDefaultRootElement
     */

   
public abstract Element getDefaultRootElement();

   
// ---- local methods -----------------------------------------

   
/**
     * Returns the <code>FilterBypass</code>. This will create one if one
     * does not yet exist.
     */

   
private DocumentFilter.FilterBypass getFilterBypass() {
       
if (filterBypass == null) {
            filterBypass
= new DefaultFilterBypass();
       
}
       
return filterBypass;
   
}

   
/**
     * Returns the root element of the bidirectional structure for this
     * document.  Its children represent character runs with a given
     * Unicode bidi level.
     */

   
public Element getBidiRootElement() {
       
return bidiRoot;
   
}

   
/**
     * Returns true if the text in the range <code>p0</code> to
     * <code>p1</code> is left to right.
     */

   
boolean isLeftToRight(int p0, int p1) {
       
if(!getProperty(I18NProperty).equals(Boolean.TRUE)) {
           
return true;
       
}
       
Element bidiRoot = getBidiRootElement();
       
int index = bidiRoot.getElementIndex(p0);
       
Element bidiElem = bidiRoot.getElement(index);
       
if(bidiElem.getEndOffset() >= p1) {
           
AttributeSet bidiAttrs = bidiElem.getAttributes();
           
return ((StyleConstants.getBidiLevel(bidiAttrs) % 2) == 0);
       
}
       
return true;
   
}

   
/**
     * Get the paragraph element containing the given position.  Sub-classes
     * must define for themselves what exactly constitutes a paragraph.  They
     * should keep in mind however that a paragraph should at least be the
     * unit of text over which to run the Unicode bidirectional algorithm.
     *
     * @param pos the starting offset >= 0
     * @return the element */

   
public abstract Element getParagraphElement(int pos);


   
/**
     * Fetches the context for managing attributes.  This
     * method effectively establishes the strategy used
     * for compressing AttributeSet information.
     *
     * @return the context
     */

   
protected final AttributeContext getAttributeContext() {
       
return context;
   
}

   
/**
     * Updates document structure as a result of text insertion.  This
     * will happen within a write lock.  If a subclass of
     * this class reimplements this method, it should delegate to the
     * superclass as well.
     *
     * @param chng a description of the change
     * @param attr the attributes for the change
     */

   
protected void insertUpdate(DefaultDocumentEvent chng, AttributeSet attr) {
       
if( getProperty(I18NProperty).equals( Boolean.TRUE ) )
            updateBidi
( chng );

       
// Check if a multi byte is encountered in the inserted text.
       
if (chng.type == DocumentEvent.EventType.INSERT &&
                        chng
.getLength() > 0 &&
                       
!Boolean.TRUE.equals(getProperty(MultiByteProperty))) {
           
Segment segment = SegmentCache.getSharedSegment();
           
try {
                getText
(chng.getOffset(), chng.getLength(), segment);
                segment
.first();
               
do {
                   
if ((int)segment.current() > 255) {
                        putProperty
(MultiByteProperty, Boolean.TRUE);
                       
break;
                   
}
               
} while (segment.next() != Segment.DONE);
           
} catch (BadLocationException ble) {
               
// Should never happen
           
}
           
SegmentCache.releaseSharedSegment(segment);
       
}
   
}

   
/**
     * Updates any document structure as a result of text removal.  This
     * method is called before the text is actually removed from the Content.
     * This will happen within a write lock. If a subclass
     * of this class reimplements this method, it should delegate to the
     * superclass as well.
     *
     * @param chng a description of the change
     */

   
protected void removeUpdate(DefaultDocumentEvent chng) {
   
}

   
/**
     * Updates any document structure as a result of text removal.  This
     * method is called after the text has been removed from the Content.
     * This will happen within a write lock. If a subclass
     * of this class reimplements this method, it should delegate to the
     * superclass as well.
     *
     * @param chng a description of the change
     */

   
protected void postRemoveUpdate(DefaultDocumentEvent chng) {
       
if( getProperty(I18NProperty).equals( Boolean.TRUE ) )
            updateBidi
( chng );
   
}


   
/**
     * Update the bidi element structure as a result of the given change
     * to the document.  The given change will be updated to reflect the
     * changes made to the bidi structure.
     *
     * This method assumes that every offset in the model is contained in
     * exactly one paragraph.  This method also assumes that it is called
     * after the change is made to the default element structure.
     */

   
void updateBidi( DefaultDocumentEvent chng ) {

       
// Calculate the range of paragraphs affected by the change.
       
int firstPStart;
       
int lastPEnd;
       
if( chng.type == DocumentEvent.EventType.INSERT
           
|| chng.type == DocumentEvent.EventType.CHANGE )
       
{
           
int chngStart = chng.getOffset();
           
int chngEnd =  chngStart + chng.getLength();
            firstPStart
= getParagraphElement(chngStart).getStartOffset();
            lastPEnd
= getParagraphElement(chngEnd).getEndOffset();
       
} else if( chng.type == DocumentEvent.EventType.REMOVE ) {
           
Element paragraph = getParagraphElement( chng.getOffset() );
            firstPStart
= paragraph.getStartOffset();
            lastPEnd
= paragraph.getEndOffset();
       
} else {
           
throw new Error("Internal error: unknown event type.");
       
}
       
//System.out.println("updateBidi: firstPStart = " + firstPStart + " lastPEnd = " + lastPEnd );


       
// Calculate the bidi levels for the affected range of paragraphs.  The
       
// levels array will contain a bidi level for each character in the
       
// affected text.
       
byte levels[] = calculateBidiLevels( firstPStart, lastPEnd );


       
Vector newElements = new Vector();

       
// Calculate the first span of characters in the affected range with
       
// the same bidi level.  If this level is the same as the level of the
       
// previous bidi element (the existing bidi element containing
       
// firstPStart-1), then merge in the previous element.  If not, but
       
// the previous element overlaps the affected range, truncate the
       
// previous element at firstPStart.
       
int firstSpanStart = firstPStart;
       
int removeFromIndex = 0;
       
if( firstSpanStart > 0 ) {
           
int prevElemIndex = bidiRoot.getElementIndex(firstPStart-1);
            removeFromIndex
= prevElemIndex;
           
Element prevElem = bidiRoot.getElement(prevElemIndex);
           
int prevLevel=StyleConstants.getBidiLevel(prevElem.getAttributes());
           
//System.out.println("createbidiElements: prevElem= " + prevElem  + " prevLevel= " + prevLevel + "level[0] = " + levels[0]);
           
if( prevLevel==levels[0] ) {
                firstSpanStart
= prevElem.getStartOffset();
           
} else if( prevElem.getEndOffset() > firstPStart ) {
                newElements
.addElement(new BidiElement(bidiRoot,
                                                       prevElem
.getStartOffset(),
                                                       firstPStart
, prevLevel));
           
} else {
                removeFromIndex
++;
           
}
       
}

       
int firstSpanEnd = 0;
       
while((firstSpanEnd<levels.length) && (levels[firstSpanEnd]==levels[0]))
            firstSpanEnd
++;


       
// Calculate the last span of characters in the affected range with
       
// the same bidi level.  If this level is the same as the level of the
       
// next bidi element (the existing bidi element containing lastPEnd),
       
// then merge in the next element.  If not, but the next element
       
// overlaps the affected range, adjust the next element to start at
       
// lastPEnd.
       
int lastSpanEnd = lastPEnd;
       
Element newNextElem = null;
       
int removeToIndex = bidiRoot.getElementCount() - 1;
       
if( lastSpanEnd <= getLength() ) {
           
int nextElemIndex = bidiRoot.getElementIndex( lastPEnd );
            removeToIndex
= nextElemIndex;
           
Element nextElem = bidiRoot.getElement( nextElemIndex );
           
int nextLevel = StyleConstants.getBidiLevel(nextElem.getAttributes());
           
if( nextLevel == levels[levels.length-1] ) {
                lastSpanEnd
= nextElem.getEndOffset();
           
} else if( nextElem.getStartOffset() < lastPEnd ) {
                newNextElem
= new BidiElement(bidiRoot, lastPEnd,
                                              nextElem
.getEndOffset(),
                                              nextLevel
);
           
} else {
                removeToIndex
--;
           
}
       
}

       
int lastSpanStart = levels.length;
       
while( (lastSpanStart>firstSpanEnd)
               
&& (levels[lastSpanStart-1]==levels[levels.length-1]) )
            lastSpanStart
--;


       
// If the first and last spans are contiguous and have the same level,
       
// merge them and create a single new element for the entire span.
       
// Otherwise, create elements for the first and last spans as well as
       
// any spans in between.
       
if((firstSpanEnd==lastSpanStart)&&(levels[0]==levels[levels.length-1])){
            newElements
.addElement(new BidiElement(bidiRoot, firstSpanStart,
                                                   lastSpanEnd
, levels[0]));
       
} else {
           
// Create an element for the first span.
            newElements
.addElement(new BidiElement(bidiRoot, firstSpanStart,
                                                   firstSpanEnd
+firstPStart,
                                                   levels
[0]));
           
// Create elements for the spans in between the first and last
           
for( int i=firstSpanEnd; i<lastSpanStart; ) {
               
//System.out.println("executed line 872");
               
int j;
               
for( j=i;  (j<levels.length) && (levels[j] == levels[i]); j++ );
                newElements
.addElement(new BidiElement(bidiRoot, firstPStart+i,
                                                       firstPStart
+j,
                                                       
(int)levels[i]));
                i
=j;
           
}
           
// Create an element for the last span.
            newElements
.addElement(new BidiElement(bidiRoot,
                                                   lastSpanStart
+firstPStart,
                                                   lastSpanEnd
,
                                                   levels
[levels.length-1]));
       
}

       
if( newNextElem != null )
            newElements
.addElement( newNextElem );


       
// Calculate the set of existing bidi elements which must be
       
// removed.
       
int removedElemCount = 0;
       
if( bidiRoot.getElementCount() > 0 ) {
            removedElemCount
= removeToIndex - removeFromIndex + 1;
       
}
       
Element[] removedElems = new Element[removedElemCount];
       
for( int i=0; i<removedElemCount; i++ ) {
            removedElems
[i] = bidiRoot.getElement(removeFromIndex+i);
       
}

       
Element[] addedElems = new Element[ newElements.size() ];
        newElements
.copyInto( addedElems );

       
// Update the change record.
       
ElementEdit ee = new ElementEdit( bidiRoot, removeFromIndex,
                                          removedElems
, addedElems );
        chng
.addEdit( ee );

       
// Update the bidi element structure.
        bidiRoot
.replace( removeFromIndex, removedElems.length, addedElems );
   
}


   
/**
     * Calculate the levels array for a range of paragraphs.
     */

   
private byte[] calculateBidiLevels( int firstPStart, int lastPEnd ) {

       
byte levels[] = new byte[ lastPEnd - firstPStart ];
       
int  levelsEnd = 0;
       
Boolean defaultDirection = null;
       
Object d = getProperty(TextAttribute.RUN_DIRECTION);
       
if (d instanceof Boolean) {
            defaultDirection
= (Boolean) d;
       
}

       
// For each paragraph in the given range of paragraphs, get its
       
// levels array and add it to the levels array for the entire span.
       
for(int o=firstPStart; o<lastPEnd; ) {
           
Element p = getParagraphElement( o );
           
int pStart = p.getStartOffset();
           
int pEnd = p.getEndOffset();

           
// default run direction for the paragraph.  This will be
           
// null if there is no direction override specified (i.e.
           
// the direction will be determined from the content).
           
Boolean direction = defaultDirection;
            d
= p.getAttributes().getAttribute(TextAttribute.RUN_DIRECTION);
           
if (d instanceof Boolean) {
                direction
= (Boolean) d;
           
}

           
//System.out.println("updateBidi: paragraph start = " + pStart + " paragraph end = " + pEnd);

           
// Create a Bidi over this paragraph then get the level
           
// array.
           
Segment seg = SegmentCache.getSharedSegment();
           
try {
                getText
(pStart, pEnd-pStart, seg);
           
} catch (BadLocationException e ) {
               
throw new Error("Internal error: " + e.toString());
           
}
           
// REMIND(bcb) we should really be using a Segment here.
           
Bidi bidiAnalyzer;
           
int bidiflag = Bidi.DIRECTION_DEFAULT_LEFT_TO_RIGHT;
           
if (direction != null) {
               
if (TextAttribute.RUN_DIRECTION_LTR.equals(direction)) {
                    bidiflag
= Bidi.DIRECTION_LEFT_TO_RIGHT;
               
} else {
                    bidiflag
= Bidi.DIRECTION_RIGHT_TO_LEFT;
               
}
           
}
            bidiAnalyzer
= new Bidi(seg.array, seg.offset, null, 0, seg.count,
                    bidiflag
);
           
BidiUtils.getLevels(bidiAnalyzer, levels, levelsEnd);
            levelsEnd
+= bidiAnalyzer.getLength();

            o
=  p.getEndOffset();
           
SegmentCache.releaseSharedSegment(seg);
       
}

       
// REMIND(bcb) remove this code when debugging is done.
       
if( levelsEnd != levels.length )
           
throw new Error("levelsEnd assertion failed.");

       
return levels;
   
}

   
/**
     * Gives a diagnostic dump.
     *
     * @param out the output stream
     */

   
public void dump(PrintStream out) {
       
Element root = getDefaultRootElement();
       
if (root instanceof AbstractElement) {
           
((AbstractElement)root).dump(out, 0);
       
}
        bidiRoot
.dump(out,0);
   
}

   
/**
     * Gets the content for the document.
     *
     * @return the content
     */

   
protected final Content getContent() {
       
return data;
   
}

   
/**
     * Creates a document leaf element.
     * Hook through which elements are created to represent the
     * document structure.  Because this implementation keeps
     * structure and content separate, elements grow automatically
     * when content is extended so splits of existing elements
     * follow.  The document itself gets to decide how to generate
     * elements to give flexibility in the type of elements used.
     *
     * @param parent the parent element
     * @param a the attributes for the element
     * @param p0 the beginning of the range >= 0
     * @param p1 the end of the range >= p0
     * @return the new element
     */

   
protected Element createLeafElement(Element parent, AttributeSet a, int p0, int p1) {
       
return new LeafElement(parent, a, p0, p1);
   
}

   
/**
     * Creates a document branch element, that can contain other elements.
     *
     * @param parent the parent element
     * @param a the attributes
     * @return the element
     */

   
protected Element createBranchElement(Element parent, AttributeSet a) {
       
return new BranchElement(parent, a);
   
}

   
// --- Document locking ----------------------------------

   
/**
     * Fetches the current writing thread if there is one.
     * This can be used to distinguish whether a method is
     * being called as part of an existing modification or
     * if a lock needs to be acquired and a new transaction
     * started.
     *
     * @return the thread actively modifying the document
     *  or <code>null</code> if there are no modifications in progress
     */

   
protected synchronized final Thread getCurrentWriter() {
       
return currWriter;
   
}

   
/**
     * Acquires a lock to begin mutating the document this lock
     * protects.  There can be no writing, notification of changes, or
     * reading going on in order to gain the lock.  Additionally a thread is
     * allowed to gain more than one <code>writeLock</code>,
     * as long as it doesn't attempt to gain additional <code>writeLock</code>s
     * from within document notification.  Attempting to gain a
     * <code>writeLock</code> from within a DocumentListener notification will
     * result in an <code>IllegalStateException</code>.  The ability
     * to obtain more than one <code>writeLock</code> per thread allows
     * subclasses to gain a writeLock, perform a number of operations, then
     * release the lock.
     * <p>
     * Calls to <code>writeLock</code>
     * must be balanced with calls to <code>writeUnlock</code>, else the
     * <code>Document</code> will be left in a locked state so that no
     * reading or writing can be done.
     *
     * @exception IllegalStateException thrown on illegal lock
     *  attempt.  If the document is implemented properly, this can
     *  only happen if a document listener attempts to mutate the
     *  document.  This situation violates the bean event model
     *  where order of delivery is not guaranteed and all listeners
     *  should be notified before further mutations are allowed.
     */

   
protected synchronized final void writeLock() {
       
try {
           
while ((numReaders > 0) || (currWriter != null)) {
               
if (Thread.currentThread() == currWriter) {
                   
if (notifyingListeners) {
                       
// Assuming one doesn't do something wrong in a
                       
// subclass this should only happen if a
                       
// DocumentListener tries to mutate the document.
                       
throw new IllegalStateException(
                                     
"Attempt to mutate in notification");
                   
}
                    numWriters
++;
                   
return;
               
}
                wait
();
           
}
            currWriter
= Thread.currentThread();
            numWriters
= 1;
       
} catch (InterruptedException e) {
           
throw new Error("Interrupted attempt to aquire write lock");
       
}
   
}

   
/**
     * Releases a write lock previously obtained via <code>writeLock</code>.
     * After decrementing the lock count if there are no oustanding locks
     * this will allow a new writer, or readers.
     *
     * @see #writeLock
     */

   
protected synchronized final void writeUnlock() {
       
if (--numWriters <= 0) {
            numWriters
= 0;
            currWriter
= null;
            notifyAll
();
       
}
   
}

   
/**
     * Acquires a lock to begin reading some state from the
     * document.  There can be multiple readers at the same time.
     * Writing blocks the readers until notification of the change
     * to the listeners has been completed.  This method should
     * be used very carefully to avoid unintended compromise
     * of the document.  It should always be balanced with a
     * <code>readUnlock</code>.
     *
     * @see #readUnlock
     */

   
public synchronized final void readLock() {
       
try {
           
while (currWriter != null) {
               
if (currWriter == Thread.currentThread()) {
                   
// writer has full read access.... may try to acquire
                   
// lock in notification
                   
return;
               
}
                wait
();
           
}
            numReaders
+= 1;
       
} catch (InterruptedException e) {
           
throw new Error("Interrupted attempt to aquire read lock");
       
}
   
}

   
/**
     * Does a read unlock.  This signals that one
     * of the readers is done.  If there are no more readers
     * then writing can begin again.  This should be balanced
     * with a readLock, and should occur in a finally statement
     * so that the balance is guaranteed.  The following is an
     * example.
     * <pre><code>
     *     readLock();
     *     try {
     *         // do something
     *     } finally {
     *         readUnlock();
     *     }
     * </code></pre>
     *
     * @see #readLock
     */

   
public synchronized final void readUnlock() {
       
if (currWriter == Thread.currentThread()) {
           
// writer has full read access.... may try to acquire
           
// lock in notification
           
return;
       
}
       
if (numReaders <= 0) {
           
throw new StateInvariantError(BAD_LOCK_STATE);
       
}
        numReaders
-= 1;
        notify
();
   
}

   
// --- serialization ---------------------------------------------

   
private void readObject(ObjectInputStream s)
     
throws ClassNotFoundException, IOException
   
{
        s
.defaultReadObject();
        listenerList
= new EventListenerList();

       
// Restore bidi structure
       
//REMIND(bcb) This creates an initial bidi element to account for
       
//the \n that exists by default in the content.
        bidiRoot
= new BidiRootElement();
       
try {
            writeLock
();
           
Element[] p = new Element[1];
            p
[0] = new BidiElement( bidiRoot, 0, 1, 0 );
            bidiRoot
.replace(0,0,p);
       
} finally {
            writeUnlock
();
       
}
       
// At this point bidi root is only partially correct. To fully
       
// restore it we need access to getDefaultRootElement. But, this
       
// is created by the subclass and at this point will be null. We
       
// thus use registerValidation.
        s
.registerValidation(new ObjectInputValidation() {
           
public void validateObject() {
               
try {
                    writeLock
();
                   
DefaultDocumentEvent e = new DefaultDocumentEvent
                                   
(0, getLength(),
                                   
DocumentEvent.EventType.INSERT);
                    updateBidi
( e );
               
}
               
finally {
                    writeUnlock
();
               
}
           
}
       
}, 0);
   
}

   
// ----- member variables ------------------------------------------

   
private transient int numReaders;
   
private transient Thread currWriter;
   
/**
     * The number of writers, all obtained from <code>currWriter</code>.
     */

   
private transient int numWriters;
   
/**
     * True will notifying listeners.
     */

   
private transient boolean notifyingListeners;

   
private static Boolean defaultI18NProperty;

   
/**
     * Storage for document-wide properties.
     */

   
private Dictionary<Object,Object> documentProperties = null;

   
/**
     * The event listener list for the document.
     */

   
protected EventListenerList listenerList = new EventListenerList();

   
/**
     * Where the text is actually stored, and a set of marks
     * that track change as the document is edited are managed.
     */

   
private Content data;

   
/**
     * Factory for the attributes.  This is the strategy for
     * attribute compression and control of the lifetime of
     * a set of attributes as a collection.  This may be shared
     * with other documents.
     */

   
private AttributeContext context;

   
/**
     * The root of the bidirectional structure for this document.  Its children
     * represent character runs with the same Unicode bidi level.
     */

   
private transient BranchElement bidiRoot;

   
/**
     * Filter for inserting/removing of text.
     */

   
private DocumentFilter documentFilter;

   
/**
     * Used by DocumentFilter to do actual insert/remove.
     */

   
private transient DocumentFilter.FilterBypass filterBypass;

   
private static final String BAD_LOCK_STATE = "document lock failure";

   
/**
     * Error message to indicate a bad location.
     */

   
protected static final String BAD_LOCATION = "document location failure";

   
/**
     * Name of elements used to represent paragraphs
     */

   
public static final String ParagraphElementName = "paragraph";

   
/**
     * Name of elements used to represent content
     */

   
public static final String ContentElementName = "content";

   
/**
     * Name of elements used to hold sections (lines/paragraphs).
     */

   
public static final String SectionElementName = "section";

   
/**
     * Name of elements used to hold a unidirectional run
     */

   
public static final String BidiElementName = "bidi level";

   
/**
     * Name of the attribute used to specify element
     * names.
     */

   
public static final String ElementNameAttribute = "$ename";

   
/**
     * Document property that indicates whether internationalization
     * functions such as text reordering or reshaping should be
     * performed. This property should not be publicly exposed,
     * since it is used for implementation convenience only.  As a
     * side effect, copies of this property may be in its subclasses
     * that live in different packages (e.g. HTMLDocument as of now),
     * so those copies should also be taken care of when this property
     * needs to be modified.
     */

   
static final String I18NProperty = "i18n";

   
/**
     * Document property that indicates if a character has been inserted
     * into the document that is more than one byte long.  GlyphView uses
     * this to determine if it should use BreakIterator.
     */

   
static final Object MultiByteProperty = "multiByte";

   
/**
     * Document property that indicates asynchronous loading is
     * desired, with the thread priority given as the value.
     */

   
static final String AsyncLoadPriority = "load priority";

   
/**
     * Interface to describe a sequence of character content that
     * can be edited.  Implementations may or may not support a
     * history mechanism which will be reflected by whether or not
     * mutations return an UndoableEdit implementation.
     * @see AbstractDocument
     */

   
public interface Content {

       
/**
         * Creates a position within the content that will
         * track change as the content is mutated.
         *
         * @param offset the offset in the content >= 0
         * @return a Position
         * @exception BadLocationException for an invalid offset
         */

       
public Position createPosition(int offset) throws BadLocationException;

       
/**
         * Current length of the sequence of character content.
         *
         * @return the length >= 0
         */

       
public int length();

       
/**
         * Inserts a string of characters into the sequence.
         *
         * @param where   offset into the sequence to make the insertion >= 0
         * @param str     string to insert
         * @return  if the implementation supports a history mechanism,
         *    a reference to an <code>Edit</code> implementation will be returned,
         *    otherwise returns <code>null</code>
         * @exception BadLocationException  thrown if the area covered by
         *   the arguments is not contained in the character sequence
         */

       
public UndoableEdit insertString(int where, String str) throws BadLocationException;

       
/**
         * Removes some portion of the sequence.
         *
         * @param where   The offset into the sequence to make the
         *   insertion >= 0.
         * @param nitems  The number of items in the sequence to remove >= 0.
         * @return  If the implementation supports a history mechansim,
         *    a reference to an Edit implementation will be returned,
         *    otherwise null.
         * @exception BadLocationException  Thrown if the area covered by
         *   the arguments is not contained in the character sequence.
         */

       
public UndoableEdit remove(int where, int nitems) throws BadLocationException;

       
/**
         * Fetches a string of characters contained in the sequence.
         *
         * @param where   Offset into the sequence to fetch >= 0.
         * @param len     number of characters to copy >= 0.
         * @return the string
         * @exception BadLocationException  Thrown if the area covered by
         *   the arguments is not contained in the character sequence.
         */

       
public String getString(int where, int len) throws BadLocationException;

       
/**
         * Gets a sequence of characters and copies them into a Segment.
         *
         * @param where the starting offset >= 0
         * @param len the number of characters >= 0
         * @param txt the target location to copy into
         * @exception BadLocationException  Thrown if the area covered by
         *   the arguments is not contained in the character sequence.
         */

       
public void getChars(int where, int len, Segment txt) throws BadLocationException;
   
}

   
/**
     * An interface that can be used to allow MutableAttributeSet
     * implementations to use pluggable attribute compression
     * techniques.  Each mutation of the attribute set can be
     * used to exchange a previous AttributeSet instance with
     * another, preserving the possibility of the AttributeSet
     * remaining immutable.  An implementation is provided by
     * the StyleContext class.
     *
     * The Element implementations provided by this class use
     * this interface to provide their MutableAttributeSet
     * implementations, so that different AttributeSet compression
     * techniques can be employed.  The method
     * <code>getAttributeContext</code> should be implemented to
     * return the object responsible for implementing the desired
     * compression technique.
     *
     * @see StyleContext
     */

   
public interface AttributeContext {

       
/**
         * Adds an attribute to the given set, and returns
         * the new representative set.
         *
         * @param old the old attribute set
         * @param name the non-null attribute name
         * @param value the attribute value
         * @return the updated attribute set
         * @see MutableAttributeSet#addAttribute
         */

       
public AttributeSet addAttribute(AttributeSet old, Object name, Object value);

       
/**
         * Adds a set of attributes to the element.
         *
         * @param old the old attribute set
         * @param attr the attributes to add
         * @return the updated attribute set
         * @see MutableAttributeSet#addAttribute
         */

       
public AttributeSet addAttributes(AttributeSet old, AttributeSet attr);

       
/**
         * Removes an attribute from the set.
         *
         * @param old the old attribute set
         * @param name the non-null attribute name
         * @return the updated attribute set
         * @see MutableAttributeSet#removeAttribute
         */

       
public AttributeSet removeAttribute(AttributeSet old, Object name);

       
/**
         * Removes a set of attributes for the element.
         *
         * @param old the old attribute set
         * @param names the attribute names
         * @return the updated attribute set
         * @see MutableAttributeSet#removeAttributes
         */

       
public AttributeSet removeAttributes(AttributeSet old, Enumeration<?> names);

       
/**
         * Removes a set of attributes for the element.
         *
         * @param old the old attribute set
         * @param attrs the attributes
         * @return the updated attribute set
         * @see MutableAttributeSet#removeAttributes
         */

       
public AttributeSet removeAttributes(AttributeSet old, AttributeSet attrs);

       
/**
         * Fetches an empty AttributeSet.
         *
         * @return the attribute set
         */

       
public AttributeSet getEmptySet();

       
/**
         * Reclaims an attribute set.
         * This is a way for a MutableAttributeSet to mark that it no
         * longer need a particular immutable set.  This is only necessary
         * in 1.1 where there are no weak references.  A 1.1 implementation
         * would call this in its finalize method.
         *
         * @param a the attribute set to reclaim
         */

       
public void reclaim(AttributeSet a);
   
}

   
/**
     * Implements the abstract part of an element.  By default elements
     * support attributes by having a field that represents the immutable
     * part of the current attribute set for the element.  The element itself
     * implements MutableAttributeSet which can be used to modify the set
     * by fetching a new immutable set.  The immutable sets are provided
     * by the AttributeContext associated with the document.
     * <p>
     * <strong>Warning:</strong>
     * Serialized objects of this class will not be compatible with
     * future Swing releases. The current serialization support is
     * appropriate for short term storage or RMI between applications running
     * the same version of Swing.  As of 1.4, support for long term storage
     * of all JavaBeans<sup><font size="-2">TM</font></sup>
     * has been added to the <code>java.beans</code> package.
     * Please see {@link java.beans.XMLEncoder}.
     */

   
public abstract class AbstractElement implements Element, MutableAttributeSet, Serializable, TreeNode {

       
/**
         * Creates a new AbstractElement.
         *
         * @param parent the parent element
         * @param a the attributes for the element
         * @since 1.4
         */

       
public AbstractElement(Element parent, AttributeSet a) {
           
this.parent = parent;
            attributes
= getAttributeContext().getEmptySet();
           
if (a != null) {
                addAttributes
(a);
           
}
       
}

       
private final void indent(PrintWriter out, int n) {
           
for (int i = 0; i < n; i++) {
               
out.print("  ");
           
}
       
}

       
/**
         * Dumps a debugging representation of the element hierarchy.
         *
         * @param psOut the output stream
         * @param indentAmount the indentation level >= 0
         */

       
public void dump(PrintStream psOut, int indentAmount) {
           
PrintWriter out;
           
try {
               
out = new PrintWriter(new OutputStreamWriter(psOut,"JavaEsc"),
                                     
true);
           
} catch (UnsupportedEncodingException e){
               
out = new PrintWriter(psOut,true);
           
}
            indent
(out, indentAmount);
           
if (getName() == null) {
               
out.print("<??");
           
} else {
               
out.print("<" + getName());
           
}
           
if (getAttributeCount() > 0) {
               
out.println("");
               
// dump the attributes
               
Enumeration names = attributes.getAttributeNames();
               
while (names.hasMoreElements()) {
                   
Object name = names.nextElement();
                    indent
(out, indentAmount + 1);
                   
out.println(name + "=" + getAttribute(name));
               
}
                indent
(out, indentAmount);
           
}
           
out.println(">");

           
if (isLeaf()) {
                indent
(out, indentAmount+1);
               
out.print("[" + getStartOffset() + "," + getEndOffset() + "]");
               
Content c = getContent();
               
try {
                   
String contentStr = c.getString(getStartOffset(),
                                                    getEndOffset
() - getStartOffset())/*.trim()*/;
                   
if (contentStr.length() > 40) {
                        contentStr
= contentStr.substring(0, 40) + "...";
                   
}
                   
out.println("["+contentStr+"]");
               
} catch (BadLocationException e) {
                       
;
               
}

           
} else {
               
int n = getElementCount();
               
for (int i = 0; i < n; i++) {
                   
AbstractElement e = (AbstractElement) getElement(i);
                    e
.dump(psOut, indentAmount+1);
               
}
           
}
       
}

       
// --- AttributeSet ----------------------------
       
// delegated to the immutable field "attributes"

       
/**
         * Gets the number of attributes that are defined.
         *
         * @return the number of attributes >= 0
         * @see AttributeSet#getAttributeCount
         */

       
public int getAttributeCount() {
           
return attributes.getAttributeCount();
       
}

       
/**
         * Checks whether a given attribute is defined.
         *
         * @param attrName the non-null attribute name
         * @return true if the attribute is defined
         * @see AttributeSet#isDefined
         */

       
public boolean isDefined(Object attrName) {
           
return attributes.isDefined(attrName);
       
}

       
/**
         * Checks whether two attribute sets are equal.
         *
         * @param attr the attribute set to check against
         * @return true if the same
         * @see AttributeSet#isEqual
         */

       
public boolean isEqual(AttributeSet attr) {
           
return attributes.isEqual(attr);
       
}

       
/**
         * Copies a set of attributes.
         *
         * @return the copy
         * @see AttributeSet#copyAttributes
         */

       
public AttributeSet copyAttributes() {
           
return attributes.copyAttributes();
       
}

       
/**
         * Gets the value of an attribute.
         *
         * @param attrName the non-null attribute name
         * @return the attribute value
         * @see AttributeSet#getAttribute
         */

       
public Object getAttribute(Object attrName) {
           
Object value = attributes.getAttribute(attrName);
           
if (value == null) {
               
// The delegate nor it's resolvers had a match,
               
// so we'll try to resolve through the parent
               
// element.
               
AttributeSet a = (parent != null) ? parent.getAttributes() : null;
               
if (a != null) {
                    value
= a.getAttribute(attrName);
               
}
           
}
           
return value;
       
}

       
/**
         * Gets the names of all attributes.
         *
         * @return the attribute names as an enumeration
         * @see AttributeSet#getAttributeNames
         */

       
public Enumeration<?> getAttributeNames() {
           
return attributes.getAttributeNames();
       
}

       
/**
         * Checks whether a given attribute name/value is defined.
         *
         * @param name the non-null attribute name
         * @param value the attribute value
         * @return true if the name/value is defined
         * @see AttributeSet#containsAttribute
         */

       
public boolean containsAttribute(Object name, Object value) {
           
return attributes.containsAttribute(name, value);
       
}


       
/**
         * Checks whether the element contains all the attributes.
         *
         * @param attrs the attributes to check
         * @return true if the element contains all the attributes
         * @see AttributeSet#containsAttributes
         */

       
public boolean containsAttributes(AttributeSet attrs) {
           
return attributes.containsAttributes(attrs);
       
}

       
/**
         * Gets the resolving parent.
         * If not overridden, the resolving parent defaults to
         * the parent element.
         *
         * @return the attributes from the parent, <code>null</code> if none
         * @see AttributeSet#getResolveParent
         */

       
public AttributeSet getResolveParent() {
           
AttributeSet a = attributes.getResolveParent();
           
if ((a == null) && (parent != null)) {
                a
= parent.getAttributes();
           
}
           
return a;
       
}

       
// --- MutableAttributeSet ----------------------------------
       
// should fetch a new immutable record for the field
       
// "attributes".

       
/**
         * Adds an attribute to the element.
         *
         * @param name the non-null attribute name
         * @param value the attribute value
         * @see MutableAttributeSet#addAttribute
         */

       
public void addAttribute(Object name, Object value) {
            checkForIllegalCast
();
           
AttributeContext context = getAttributeContext();
            attributes
= context.addAttribute(attributes, name, value);
       
}

       
/**
         * Adds a set of attributes to the element.
         *
         * @param attr the attributes to add
         * @see MutableAttributeSet#addAttribute
         */

       
public void addAttributes(AttributeSet attr) {
            checkForIllegalCast
();
           
AttributeContext context = getAttributeContext();
            attributes
= context.addAttributes(attributes, attr);
       
}

       
/**
         * Removes an attribute from the set.
         *
         * @param name the non-null attribute name
         * @see MutableAttributeSet#removeAttribute
         */

       
public void removeAttribute(Object name) {
            checkForIllegalCast
();
           
AttributeContext context = getAttributeContext();
            attributes
= context.removeAttribute(attributes, name);
       
}

       
/**
         * Removes a set of attributes for the element.
         *
         * @param names the attribute names
         * @see MutableAttributeSet#removeAttributes
         */

       
public void removeAttributes(Enumeration<?> names) {
            checkForIllegalCast
();
           
AttributeContext context = getAttributeContext();
            attributes
= context.removeAttributes(attributes, names);
       
}

       
/**
         * Removes a set of attributes for the element.
         *
         * @param attrs the attributes
         * @see MutableAttributeSet#removeAttributes
         */

       
public void removeAttributes(AttributeSet attrs) {
            checkForIllegalCast
();
           
AttributeContext context = getAttributeContext();
           
if (attrs == this) {
                attributes
= context.getEmptySet();
           
} else {
                attributes
= context.removeAttributes(attributes, attrs);
           
}
       
}

       
/**
         * Sets the resolving parent.
         *
         * @param parent the parent, null if none
         * @see MutableAttributeSet#setResolveParent
         */

       
public void setResolveParent(AttributeSet parent) {
            checkForIllegalCast
();
           
AttributeContext context = getAttributeContext();
           
if (parent != null) {
                attributes
=
                    context
.addAttribute(attributes, StyleConstants.ResolveAttribute,
                                         parent
);
           
} else {
                attributes
=
                    context
.removeAttribute(attributes, StyleConstants.ResolveAttribute);
           
}
       
}

       
private final void checkForIllegalCast() {
           
Thread t = getCurrentWriter();
           
if ((t == null) || (t != Thread.currentThread())) {
               
throw new StateInvariantError("Illegal cast to MutableAttributeSet");
           
}
       
}

       
// --- Element methods -------------------------------------

       
/**
         * Retrieves the underlying model.
         *
         * @return the model
         */

       
public Document getDocument() {
           
return AbstractDocument.this;
       
}

       
/**
         * Gets the parent of the element.
         *
         * @return the parent
         */

       
public Element getParentElement() {
           
return parent;
       
}

       
/**
         * Gets the attributes for the element.
         *
         * @return the attribute set
         */

       
public AttributeSet getAttributes() {
           
return this;
       
}

       
/**
         * Gets the name of the element.
         *
         * @return the name, null if none
         */

       
public String getName() {
           
if (attributes.isDefined(ElementNameAttribute)) {
               
return (String) attributes.getAttribute(ElementNameAttribute);
           
}
           
return null;
       
}

       
/**
         * Gets the starting offset in the model for the element.
         *
         * @return the offset >= 0
         */

       
public abstract int getStartOffset();

       
/**
         * Gets the ending offset in the model for the element.
         *
         * @return the offset >= 0
         */

       
public abstract int getEndOffset();

       
/**
         * Gets a child element.
         *
         * @param index the child index, >= 0 && < getElementCount()
         * @return the child element
         */

       
public abstract Element getElement(int index);

       
/**
         * Gets the number of children for the element.
         *
         * @return the number of children >= 0
         */

       
public abstract int getElementCount();

       
/**
         * Gets the child element index closest to the given model offset.
         *
         * @param offset the offset >= 0
         * @return the element index >= 0
         */

       
public abstract int getElementIndex(int offset);

       
/**
         * Checks whether the element is a leaf.
         *
         * @return true if a leaf
         */

       
public abstract boolean isLeaf();

       
// --- TreeNode methods -------------------------------------

       
/**
         * Returns the child <code>TreeNode</code> at index
         * <code>childIndex</code>.
         */

       
public TreeNode getChildAt(int childIndex) {
           
return (TreeNode)getElement(childIndex);
       
}

       
/**
         * Returns the number of children <code>TreeNode</code>'s
         * receiver contains.
         * @return the number of children <code>TreeNodews</code>'s
         * receiver contains
         */

       
public int getChildCount() {
           
return getElementCount();
       
}

       
/**
         * Returns the parent <code>TreeNode</code> of the receiver.
         * @return the parent <code>TreeNode</code> of the receiver
         */

       
public TreeNode getParent() {
           
return (TreeNode)getParentElement();
       
}

       
/**
         * Returns the index of <code>node</code> in the receivers children.
         * If the receiver does not contain <code>node</code>, -1 will be
         * returned.
         * @param node the location of interest
         * @return the index of <code>node</code> in the receiver's
         * children, or -1 if absent
         */

       
public int getIndex(TreeNode node) {
           
for(int counter = getChildCount() - 1; counter >= 0; counter--)
               
if(getChildAt(counter) == node)
                   
return counter;
           
return -1;
       
}

       
/**
         * Returns true if the receiver allows children.
         * @return true if the receiver allows children, otherwise false
         */

       
public abstract boolean getAllowsChildren();


       
/**
         * Returns the children of the receiver as an
         * <code>Enumeration</code>.
         * @return the children of the receiver as an <code>Enumeration</code>
         */

       
public abstract Enumeration children();


       
// --- serialization ---------------------------------------------

       
private void writeObject(ObjectOutputStream s) throws IOException {
            s
.defaultWriteObject();
           
StyleContext.writeAttributeSet(s, attributes);
       
}

       
private void readObject(ObjectInputStream s)
           
throws ClassNotFoundException, IOException
       
{
            s
.defaultReadObject();
           
MutableAttributeSet attr = new SimpleAttributeSet();
           
StyleContext.readAttributeSet(s, attr);
           
AttributeContext context = getAttributeContext();
            attributes
= context.addAttributes(SimpleAttributeSet.EMPTY, attr);
       
}

       
// ---- variables -----------------------------------------------------

       
private Element parent;
       
private transient AttributeSet attributes;

   
}

   
/**
     * Implements a composite element that contains other elements.
     * <p>
     * <strong>Warning:</strong>
     * Serialized objects of this class will not be compatible with
     * future Swing releases. The current serialization support is
     * appropriate for short term storage or RMI between applications running
     * the same version of Swing.  As of 1.4, support for long term storage
     * of all JavaBeans<sup><font size="-2">TM</font></sup>
     * has been added to the <code>java.beans</code> package.
     * Please see {@link java.beans.XMLEncoder}.
     */

   
public class BranchElement extends AbstractElement {

       
/**
         * Constructs a composite element that initially contains
         * no children.
         *
         * @param parent  The parent element
         * @param a the attributes for the element
         * @since 1.4
         */

       
public BranchElement(Element parent, AttributeSet a) {
           
super(parent, a);
            children
= new AbstractElement[1];
            nchildren
= 0;
            lastIndex
= -1;
       
}

       
/**
         * Gets the child element that contains
         * the given model position.
         *
         * @param pos the position >= 0
         * @return the element, null if none
         */

       
public Element positionToElement(int pos) {
           
int index = getElementIndex(pos);
           
Element child = children[index];
           
int p0 = child.getStartOffset();
           
int p1 = child.getEndOffset();
           
if ((pos >= p0) && (pos < p1)) {
               
return child;
           
}
           
return null;
       
}

       
/**
         * Replaces content with a new set of elements.
         *
         * @param offset the starting offset >= 0
         * @param length the length to replace >= 0
         * @param elems the new elements
         */

       
public void replace(int offset, int length, Element[] elems) {
           
int delta = elems.length - length;
           
int src = offset + length;
           
int nmove = nchildren - src;
           
int dest = src + delta;
           
if ((nchildren + delta) >= children.length) {
               
// need to grow the array
               
int newLength = Math.max(2*children.length, nchildren + delta);
               
AbstractElement[] newChildren = new AbstractElement[newLength];
               
System.arraycopy(children, 0, newChildren, 0, offset);
               
System.arraycopy(elems, 0, newChildren, offset, elems.length);
               
System.arraycopy(children, src, newChildren, dest, nmove);
                children
= newChildren;
           
} else {
               
// patch the existing array
               
System.arraycopy(children, src, children, dest, nmove);
               
System.arraycopy(elems, 0, children, offset, elems.length);
           
}
            nchildren
= nchildren + delta;
       
}

       
/**
         * Converts the element to a string.
         *
         * @return the string
         */

       
public String toString() {
           
return "BranchElement(" + getName() + ") " + getStartOffset() + "," +
                getEndOffset
() + "\n";
       
}

       
// --- Element methods -----------------------------------

       
/**
         * Gets the element name.
         *
         * @return the element name
         */

       
public String getName() {
           
String nm = super.getName();
           
if (nm == null) {
                nm
= ParagraphElementName;
           
}
           
return nm;
       
}

       
/**
         * Gets the starting offset in the model for the element.
         *
         * @return the offset >= 0
         */

       
public int getStartOffset() {
           
return children[0].getStartOffset();
       
}

       
/**
         * Gets the ending offset in the model for the element.
         * @throws NullPointerException if this element has no children
         *
         * @return the offset >= 0
         */

       
public int getEndOffset() {
           
Element child =
               
(nchildren > 0) ? children[nchildren - 1] : children[0];
           
return child.getEndOffset();
       
}

       
/**
         * Gets a child element.
         *
         * @param index the child index, >= 0 && < getElementCount()
         * @return the child element, null if none
         */

       
public Element getElement(int index) {
           
if (index < nchildren) {
               
return children[index];
           
}
           
return null;
       
}

       
/**
         * Gets the number of children for the element.
         *
         * @return the number of children >= 0
         */

       
public int getElementCount()  {
           
return nchildren;
       
}

       
/**
         * Gets the child element index closest to the given model offset.
         *
         * @param offset the offset >= 0
         * @return the element index >= 0
         */

       
public int getElementIndex(int offset) {
           
int index;
           
int lower = 0;
           
int upper = nchildren - 1;
           
int mid = 0;
           
int p0 = getStartOffset();
           
int p1;

           
if (nchildren == 0) {
               
return 0;
           
}
           
if (offset >= getEndOffset()) {
               
return nchildren - 1;
           
}

           
// see if the last index can be used.
           
if ((lastIndex >= lower) && (lastIndex <= upper)) {
               
Element lastHit = children[lastIndex];
                p0
= lastHit.getStartOffset();
                p1
= lastHit.getEndOffset();
               
if ((offset >= p0) && (offset < p1)) {
                   
return lastIndex;
               
}

               
// last index wasn't a hit, but it does give useful info about
               
// where a hit (if any) would be.
               
if (offset < p0) {
                    upper
= lastIndex;
               
} else  {
                    lower
= lastIndex;
               
}
           
}

           
while (lower <= upper) {
                mid
= lower + ((upper - lower) / 2);
               
Element elem = children[mid];
                p0
= elem.getStartOffset();
                p1
= elem.getEndOffset();
               
if ((offset >= p0) && (offset < p1)) {
                   
// found the location
                    index
= mid;
                    lastIndex
= index;
                   
return index;
               
} else if (offset < p0) {
                    upper
= mid - 1;
               
} else {
                    lower
= mid + 1;
               
}
           
}

           
// didn't find it, but we indicate the index of where it would belong
           
if (offset < p0) {
                index
= mid;
           
} else {
                index
= mid + 1;
           
}
            lastIndex
= index;
           
return index;
       
}

       
/**
         * Checks whether the element is a leaf.
         *
         * @return true if a leaf
         */

       
public boolean isLeaf() {
           
return false;
       
}


       
// ------ TreeNode ----------------------------------------------

       
/**
         * Returns true if the receiver allows children.
         * @return true if the receiver allows children, otherwise false
         */

       
public boolean getAllowsChildren() {
           
return true;
       
}


       
/**
         * Returns the children of the receiver as an
         * <code>Enumeration</code>.
         * @return the children of the receiver
         */

       
public Enumeration children() {
           
if(nchildren == 0)
               
return null;

           
Vector tempVector = new Vector(nchildren);

           
for(int counter = 0; counter < nchildren; counter++)
                tempVector
.addElement(children[counter]);
           
return tempVector.elements();
       
}

       
// ------ members ----------------------------------------------

       
private AbstractElement[] children;
       
private int nchildren;
       
private int lastIndex;
   
}

   
/**
     * Implements an element that directly represents content of
     * some kind.
     * <p>
     * <strong>Warning:</strong>
     * Serialized objects of this class will not be compatible with
     * future Swing releases. The current serialization support is
     * appropriate for short term storage or RMI between applications running
     * the same version of Swing.  As of 1.4, support for long term storage
     * of all JavaBeans<sup><font size="-2">TM</font></sup>
     * has been added to the <code>java.beans</code> package.
     * Please see {@link java.beans.XMLEncoder}.
     *
     * @see     Element
     */

   
public class LeafElement extends AbstractElement {

       
/**
         * Constructs an element that represents content within the
         * document (has no children).
         *
         * @param parent  The parent element
         * @param a       The element attributes
         * @param offs0   The start offset >= 0
         * @param offs1   The end offset >= offs0
         * @since 1.4
         */

       
public LeafElement(Element parent, AttributeSet a, int offs0, int offs1) {
           
super(parent, a);
           
try {
                p0
= createPosition(offs0);
                p1
= createPosition(offs1);
           
} catch (BadLocationException e) {
                p0
= null;
                p1
= null;
               
throw new StateInvariantError("Can't create Position references");
           
}
       
}

       
/**
         * Converts the element to a string.
         *
         * @return the string
         */

       
public String toString() {
           
return "LeafElement(" + getName() + ") " + p0 + "," + p1 + "\n";
       
}

       
// --- Element methods ---------------------------------------------

       
/**
         * Gets the starting offset in the model for the element.
         *
         * @return the offset >= 0
         */

       
public int getStartOffset() {
           
return p0.getOffset();
       
}

       
/**
         * Gets the ending offset in the model for the element.
         *
         * @return the offset >= 0
         */

       
public int getEndOffset() {
           
return p1.getOffset();
       
}

       
/**
         * Gets the element name.
         *
         * @return the name
         */

       
public String getName() {
           
String nm = super.getName();
           
if (nm == null) {
                nm
= ContentElementName;
           
}
           
return nm;
       
}

       
/**
         * Gets the child element index closest to the given model offset.
         *
         * @param pos the offset >= 0
         * @return the element index >= 0
         */

       
public int getElementIndex(int pos) {
           
return -1;
       
}

       
/**
         * Gets a child element.
         *
         * @param index the child index, >= 0 && < getElementCount()
         * @return the child element
         */

       
public Element getElement(int index) {
           
return null;
       
}

       
/**
         * Returns the number of child elements.
         *
         * @return the number of children >= 0
         */

       
public int getElementCount()  {
           
return 0;
       
}

       
/**
         * Checks whether the element is a leaf.
         *
         * @return true if a leaf
         */

       
public boolean isLeaf() {
           
return true;
       
}

       
// ------ TreeNode ----------------------------------------------

       
/**
         * Returns true if the receiver allows children.
         * @return true if the receiver allows children, otherwise false
         */

       
public boolean getAllowsChildren() {
           
return false;
       
}


       
/**
         * Returns the children of the receiver as an
         * <code>Enumeration</code>.
         * @return the children of the receiver
         */

       
public Enumeration children() {
           
return null;
       
}

       
// --- serialization ---------------------------------------------

       
private void writeObject(ObjectOutputStream s) throws IOException {
            s
.defaultWriteObject();
            s
.writeInt(p0.getOffset());
            s
.writeInt(p1.getOffset());
       
}

       
private void readObject(ObjectInputStream s)
           
throws ClassNotFoundException, IOException
       
{
            s
.defaultReadObject();

           
// set the range with positions that track change
           
int off0 = s.readInt();
           
int off1 = s.readInt();
           
try {
                p0
= createPosition(off0);
                p1
= createPosition(off1);
           
} catch (BadLocationException e) {
                p0
= null;
                p1
= null;
               
throw new IOException("Can't restore Position references");
           
}
       
}

       
// ---- members -----------------------------------------------------

       
private transient Position p0;
       
private transient Position p1;
   
}

   
/**
     * Represents the root element of the bidirectional element structure.
     * The root element is the only element in the bidi element structure
     * which contains children.
     */

   
class BidiRootElement extends BranchElement {

       
BidiRootElement() {
           
super( null, null );
       
}

       
/**
         * Gets the name of the element.
         * @return the name
         */

       
public String getName() {
           
return "bidi root";
       
}
   
}

   
/**
     * Represents an element of the bidirectional element structure.
     */

   
class BidiElement extends LeafElement {

       
/**
         * Creates a new BidiElement.
         */

       
BidiElement(Element parent, int start, int end, int level) {
           
super(parent, new SimpleAttributeSet(), start, end);
            addAttribute
(StyleConstants.BidiLevel, new Integer(level));
           
//System.out.println("BidiElement: start = " + start
           
//                   + " end = " + end + " level = " + level );
       
}

       
/**
         * Gets the name of the element.
         * @return the name
         */

       
public String getName() {
           
return BidiElementName;
       
}

       
int getLevel() {
           
Integer o = (Integer) getAttribute(StyleConstants.BidiLevel);
           
if (o != null) {
               
return o.intValue();
           
}
           
return 0;  // Level 0 is base level (non-embedded) left-to-right
       
}

       
boolean isLeftToRight() {
           
return ((getLevel() % 2) == 0);
       
}
   
}

   
/**
     * Stores document changes as the document is being
     * modified.  Can subsequently be used for change notification
     * when done with the document modification transaction.
     * This is used by the AbstractDocument class and its extensions
     * for broadcasting change information to the document listeners.
     */

   
public class DefaultDocumentEvent extends CompoundEdit implements DocumentEvent {

       
/**
         * Constructs a change record.
         *
         * @param offs the offset into the document of the change >= 0
         * @param len  the length of the change >= 0
         * @param type the type of event (DocumentEvent.EventType)
         * @since 1.4
         */

       
public DefaultDocumentEvent(int offs, int len, DocumentEvent.EventType type) {
           
super();
            offset
= offs;
            length
= len;
           
this.type = type;
       
}

       
/**
         * Returns a string description of the change event.
         *
         * @return a string
         */

       
public String toString() {
           
return edits.toString();
       
}

       
// --- CompoundEdit methods --------------------------

       
/**
         * Adds a document edit.  If the number of edits crosses
         * a threshold, this switches on a hashtable lookup for
         * ElementChange implementations since access of these
         * needs to be relatively quick.
         *
         * @param anEdit a document edit record
         * @return true if the edit was added
         */

       
public boolean addEdit(UndoableEdit anEdit) {
           
// if the number of changes gets too great, start using
           
// a hashtable for to locate the change for a given element.
           
if ((changeLookup == null) && (edits.size() > 10)) {
                changeLookup
= new Hashtable();
               
int n = edits.size();
               
for (int i = 0; i < n; i++) {
                   
Object o = edits.elementAt(i);
                   
if (o instanceof DocumentEvent.ElementChange) {
                       
DocumentEvent.ElementChange ec = (DocumentEvent.ElementChange) o;
                        changeLookup
.put(ec.getElement(), ec);
                   
}
               
}
           
}

           
// if we have a hashtable... add the entry if it's
           
// an ElementChange.
           
if ((changeLookup != null) && (anEdit instanceof DocumentEvent.ElementChange)) {
               
DocumentEvent.ElementChange ec = (DocumentEvent.ElementChange) anEdit;
                changeLookup
.put(ec.getElement(), ec);
           
}
           
return super.addEdit(anEdit);
       
}

       
/**
         * Redoes a change.
         *
         * @exception CannotRedoException if the change cannot be redone
         */

       
public void redo() throws CannotRedoException {
            writeLock
();
           
try {
               
// change the state
               
super.redo();
               
// fire a DocumentEvent to notify the view(s)
               
UndoRedoDocumentEvent ev = new UndoRedoDocumentEvent(this, false);
               
if (type == DocumentEvent.EventType.INSERT) {
                    fireInsertUpdate
(ev);
               
} else if (type == DocumentEvent.EventType.REMOVE) {
                    fireRemoveUpdate
(ev);
               
} else {
                    fireChangedUpdate
(ev);
               
}
           
} finally {
                writeUnlock
();
           
}
       
}

       
/**
         * Undoes a change.
         *
         * @exception CannotUndoException if the change cannot be undone
         */

       
public void undo() throws CannotUndoException {
            writeLock
();
           
try {
               
// change the state
               
super.undo();
               
// fire a DocumentEvent to notify the view(s)
               
UndoRedoDocumentEvent ev = new UndoRedoDocumentEvent(this, true);
               
if (type == DocumentEvent.EventType.REMOVE) {
                    fireInsertUpdate
(ev);
               
} else if (type == DocumentEvent.EventType.INSERT) {
                    fireRemoveUpdate
(ev);
               
} else {
                    fireChangedUpdate
(ev);
               
}
           
} finally {
                writeUnlock
();
           
}
       
}

       
/**
         * DefaultDocument events are significant.  If you wish to aggregate
         * DefaultDocumentEvents to present them as a single edit to the user
         * place them into a CompoundEdit.
         *
         * @return whether the event is significant for edit undo purposes
         */

       
public boolean isSignificant() {
           
return true;
       
}


       
/**
         * Provides a localized, human readable description of this edit
         * suitable for use in, say, a change log.
         *
         * @return the description
         */

       
public String getPresentationName() {
           
DocumentEvent.EventType type = getType();
           
if(type == DocumentEvent.EventType.INSERT)
               
return UIManager.getString("AbstractDocument.additionText");
           
if(type == DocumentEvent.EventType.REMOVE)
               
return UIManager.getString("AbstractDocument.deletionText");
           
return UIManager.getString("AbstractDocument.styleChangeText");
       
}

       
/**
         * Provides a localized, human readable description of the undoable
         * form of this edit, e.g. for use as an Undo menu item. Typically
         * derived from getDescription();
         *
         * @return the description
         */

       
public String getUndoPresentationName() {
           
return UIManager.getString("AbstractDocument.undoText") + " " +
                getPresentationName
();
       
}

       
/**
         * Provides a localized, human readable description of the redoable
         * form of this edit, e.g. for use as a Redo menu item. Typically
         * derived from getPresentationName();
         *
         * @return the description
         */

       
public String getRedoPresentationName() {
           
return UIManager.getString("AbstractDocument.redoText") + " " +
                getPresentationName
();
       
}

       
// --- DocumentEvent methods --------------------------

       
/**
         * Returns the type of event.
         *
         * @return the event type as a DocumentEvent.EventType
         * @see DocumentEvent#getType
         */

       
public DocumentEvent.EventType getType() {
           
return type;
       
}

       
/**
         * Returns the offset within the document of the start of the change.
         *
         * @return the offset >= 0
         * @see DocumentEvent#getOffset
         */

       
public int getOffset() {
           
return offset;
       
}

       
/**
         * Returns the length of the change.
         *
         * @return the length >= 0
         * @see DocumentEvent#getLength
         */

       
public int getLength() {
           
return length;
       
}

       
/**
         * Gets the document that sourced the change event.
         *
         * @return the document
         * @see DocumentEvent#getDocument
         */

       
public Document getDocument() {
           
return AbstractDocument.this;
       
}

       
/**
         * Gets the changes for an element.
         *
         * @param elem the element
         * @return the changes
         */

       
public DocumentEvent.ElementChange getChange(Element elem) {
           
if (changeLookup != null) {
               
return (DocumentEvent.ElementChange) changeLookup.get(elem);
           
}
           
int n = edits.size();
           
for (int i = 0; i < n; i++) {
               
Object o = edits.elementAt(i);
               
if (o instanceof DocumentEvent.ElementChange) {
                   
DocumentEvent.ElementChange c = (DocumentEvent.ElementChange) o;
                   
if (elem.equals(c.getElement())) {
                       
return c;
                   
}
               
}
           
}
           
return null;
       
}

       
// --- member variables ------------------------------------

       
private int offset;
       
private int length;
       
private Hashtable changeLookup;
       
private DocumentEvent.EventType type;

   
}

   
/**
     * This event used when firing document changes while Undo/Redo
     * operations. It just wraps DefaultDocumentEvent and delegates
     * all calls to it except getType() which depends on operation
     * (Undo or Redo).
     */

   
class UndoRedoDocumentEvent implements DocumentEvent {
       
private DefaultDocumentEvent src = null;
       
private boolean isUndo;
       
private EventType type = null;

       
public UndoRedoDocumentEvent(DefaultDocumentEvent src, boolean isUndo) {
           
this.src = src;
           
this.isUndo = isUndo;
           
if(isUndo) {
               
if(src.getType().equals(EventType.INSERT)) {
                    type
= EventType.REMOVE;
               
} else if(src.getType().equals(EventType.REMOVE)) {
                    type
= EventType.INSERT;
               
} else {
                    type
= src.getType();
               
}
           
} else {
                type
= src.getType();
           
}
       
}

       
public DefaultDocumentEvent getSource() {
           
return src;
       
}

       
// DocumentEvent methods delegated to DefaultDocumentEvent source
       
// except getType() which depends on operation (Undo or Redo).
       
public int getOffset() {
           
return src.getOffset();
       
}

       
public int getLength() {
           
return src.getLength();
       
}

       
public Document getDocument() {
           
return src.getDocument();
       
}

       
public DocumentEvent.EventType getType() {
           
return type;
       
}

       
public DocumentEvent.ElementChange getChange(Element elem) {
           
return src.getChange(elem);
       
}
   
}

   
/**
     * An implementation of ElementChange that can be added to the document
     * event.
     */

   
public static class ElementEdit extends AbstractUndoableEdit implements DocumentEvent.ElementChange {

       
/**
         * Constructs an edit record.  This does not modify the element
         * so it can safely be used to <em>catch up</em> a view to the
         * current model state for views that just attached to a model.
         *
         * @param e the element
         * @param index the index into the model >= 0
         * @param removed a set of elements that were removed
         * @param added a set of elements that were added
         */

       
public ElementEdit(Element e, int index, Element[] removed, Element[] added) {
           
super();
           
this.e = e;
           
this.index = index;
           
this.removed = removed;
           
this.added = added;
       
}

       
/**
         * Returns the underlying element.
         *
         * @return the element
         */

       
public Element getElement() {
           
return e;
       
}

       
/**
         * Returns the index into the list of elements.
         *
         * @return the index >= 0
         */

       
public int getIndex() {
           
return index;
       
}

       
/**
         * Gets a list of children that were removed.
         *
         * @return the list
         */

       
public Element[] getChildrenRemoved() {
           
return removed;
       
}

       
/**
         * Gets a list of children that were added.
         *
         * @return the list
         */

       
public Element[] getChildrenAdded() {
           
return added;
       
}

       
/**
         * Redoes a change.
         *
         * @exception CannotRedoException if the change cannot be redone
         */

       
public void redo() throws CannotRedoException {
           
super.redo();

           
// Since this event will be reused, switch around added/removed.
           
Element[] tmp = removed;
            removed
= added;
            added
= tmp;

           
// PENDING(prinz) need MutableElement interface, canRedo() should check
           
((AbstractDocument.BranchElement)e).replace(index, removed.length, added);
       
}

       
/**
         * Undoes a change.
         *
         * @exception CannotUndoException if the change cannot be undone
         */

       
public void undo() throws CannotUndoException {
           
super.undo();
           
// PENDING(prinz) need MutableElement interface, canUndo() should check
           
((AbstractDocument.BranchElement)e).replace(index, added.length, removed);

           
// Since this event will be reused, switch around added/removed.
           
Element[] tmp = removed;
            removed
= added;
            added
= tmp;
       
}

       
private Element e;
       
private int index;
       
private Element[] removed;
       
private Element[] added;
   
}


   
private class DefaultFilterBypass extends DocumentFilter.FilterBypass {
       
public Document getDocument() {
           
return AbstractDocument.this;
       
}

       
public void remove(int offset, int length) throws
           
BadLocationException {
            handleRemove
(offset, length);
       
}

       
public void insertString(int offset, String string,
                                 
AttributeSet attr) throws
                                       
BadLocationException {
            handleInsertString
(offset, string, attr);
       
}

       
public void replace(int offset, int length, String text,
                           
AttributeSet attrs) throws BadLocationException {
            handleRemove
(offset, length);
            handleInsertString
(offset, text, attrs);
       
}
   
}
}