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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * 2 along with this work; if not, write to the Free Software Foundation,
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package javax.swing.text;

import javax.swing.event.*;


The Document is a container for text that serves
as the model for swing text components.  The goal for this
interface is to scale from very simple needs (a plain text textfield)
to complex needs (an HTML or XML document, for example).
Content

At the simplest level, text can be
modeled as a linear sequence of characters. To support
internationalization, the Swing text model uses
unicode characters.
The sequence of characters displayed in a text component is
generally referred to as the component's content.

To refer to locations within the sequence, the coordinates
used are the location between two characters.  As the diagram
below shows, a location in a text document can be referred to
as a position, or an offset. This position is zero-based.


In the example, if the content of a document is the
sequence "The quick brown fox," as shown in the preceding diagram,
the location just before the word "The" is 0, and the location after
the word "The" and before the whitespace that follows it is 3.
The entire sequence of characters in the sequence "The" is called a
range.
The following methods give access to the character data
that makes up the content.

getLength() 
getText(int, int) 
getText(int, int, Segment) 
Structure

Text is rarely represented simply as featureless content. Rather,
text typically has some sort of structure associated with it.
Exactly what structure is modeled is up to a particular Document
implementation.  It might be as simple as no structure (i.e. a
simple text field), or it might be something like diagram below.


The unit of structure (i.e. a node of the tree) is referred to
by the Element interface.  Each Element
can be tagged with a set of attributes.  These attributes
(name/value pairs) are defined by the
AttributeSet interface.
The following methods give access to the document structure.

getDefaultRootElement() 
getRootElements() 
Mutations

All documents need to be able to add and remove simple text.
Typically, text is inserted and removed via gestures from
a keyboard or a mouse.  What effect the insertion or removal
has upon the document structure is entirely up to the
implementation of the document.
The following methods are related to mutation of the
document content:

insertString(int, String, AttributeSet) 
remove(int, int) 
createPosition(int) 
Notification

Mutations to the Document must be communicated to
interested observers.  The notification of change follows the event model
guidelines that are specified for JavaBeans.  In the JavaBeans
event model, once an event notification is dispatched, all listeners
must be notified before any further mutations occur to the source
of the event.  Further, order of delivery is not guaranteed.

Notification is provided as two separate events,
DocumentEvent, and
UndoableEditEvent.
If a mutation is made to a Document through its api,
a DocumentEvent will be sent to all of the registered
DocumentListeners.  If the Document
implementation supports undo/redo capabilities, an
UndoableEditEvent will be sent
to all of the registered UndoableEditListeners.
If an undoable edit is undone, a DocumentEvent should be
fired from the Document to indicate it has changed again.
In this case however, there should be no UndoableEditEvent
generated since that edit is actually the source of the change
rather than a mutation to the Document made through its
api.


Referring to the above diagram, suppose that the component shown
on the left mutates the document object represented by the blue
rectangle. The document responds by dispatching a DocumentEvent to
both component views and sends an UndoableEditEvent to the listening
logic, which maintains a history buffer.

Now suppose that the component shown on the right mutates the same
document.  Again, the document dispatches a DocumentEvent to both
component views and sends an UndoableEditEvent to the listening logic
that is maintaining the history buffer.

If the history buffer is then rolled back (i.e. the last UndoableEdit
undone), a DocumentEvent is sent to both views, causing both of them to
reflect the undone mutation to the document (that is, the
removal of the right component's mutation). If the history buffer again
rolls back another change, another DocumentEvent is sent to both views,
causing them to reflect the undone mutation to the document -- that is,
the removal of the left component's mutation.

The methods related to observing mutations to the document are:

  
addDocumentListener(DocumentListener) 
removeDocumentListener(DocumentListener) 
addUndoableEditListener(UndoableEditListener) 
removeUndoableEditListener(UndoableEditListener) 
Properties

Document implementations will generally have some set of properties
associated with them at runtime.  Two well known properties are the
StreamDescriptionProperty,
which can be used to describe where the Document came from,
and the TitleProperty, which can be used to
name the Document.  The methods related to the properties are:

getProperty(Object) 
putProperty(Object, Object) 
For more information on the Document class, see
The Swing Connection
and most particularly the article,

The Element Interface.
Author:
 Timothy Prinzing
See Also:
DocumentEvent
DocumentListener
UndoableEditEvent
UndoableEditListener
Element
Position
AttributeSet/**
 * <p>
 * The <code>Document</code> is a container for text that serves
 * as the model for swing text components.  The goal for this
 * interface is to scale from very simple needs (a plain text textfield)
 * to complex needs (an HTML or XML document, for example).
 *
 * <p><b>Content</b>
 * <p>
 * At the simplest level, text can be
 * modeled as a linear sequence of characters. To support
 * internationalization, the Swing text model uses
 * <a href="http://www.unicode.org/">unicode</a> characters.
 * The sequence of characters displayed in a text component is
 * generally referred to as the component's <em>content</em>.
 * <p>
 * To refer to locations within the sequence, the coordinates
 * used are the location between two characters.  As the diagram
 * below shows, a location in a text document can be referred to
 * as a position, or an offset. This position is zero-based.
 * <p style="text-align:center"><img src="doc-files/Document-coord.gif"
 * alt="The following text describes this graphic.">
 * <p>
 * In the example, if the content of a document is the
 * sequence "The quick brown fox," as shown in the preceding diagram,
 * the location just before the word "The" is 0, and the location after
 * the word "The" and before the whitespace that follows it is 3.
 * The entire sequence of characters in the sequence "The" is called a
 * <em>range</em>.
 * <p>The following methods give access to the character data
 * that makes up the content.
 * <ul>
 * <li>{@link #getLength()}
 * <li>{@link #getText(int, int)}
 * <li>{@link #getText(int, int, javax.swing.text.Segment)}
 * </ul>
 * <p><b>Structure</b>
 * <p>
 * Text is rarely represented simply as featureless content. Rather,
 * text typically has some sort of structure associated with it.
 * Exactly what structure is modeled is up to a particular Document
 * implementation.  It might be as simple as no structure (i.e. a
 * simple text field), or it might be something like diagram below.
 * <p style="text-align:center"><img src="doc-files/Document-structure.gif"
 * alt="Diagram shows Book->Chapter->Paragraph">
 * <p>
 * The unit of structure (i.e. a node of the tree) is referred to
 * by the <a href="Element.html">Element</a> interface.  Each Element
 * can be tagged with a set of attributes.  These attributes
 * (name/value pairs) are defined by the
 * <a href="AttributeSet.html">AttributeSet</a> interface.
 * <p>The following methods give access to the document structure.
 * <ul>
 * <li>{@link #getDefaultRootElement()}
 * <li>{@link #getRootElements()}
 * </ul>
 *
 * <p><b>Mutations</b>
 * <p>
 * All documents need to be able to add and remove simple text.
 * Typically, text is inserted and removed via gestures from
 * a keyboard or a mouse.  What effect the insertion or removal
 * has upon the document structure is entirely up to the
 * implementation of the document.
 * <p>The following methods are related to mutation of the
 * document content:
 * <ul>
 * <li>{@link #insertString(int, java.lang.String, javax.swing.text.AttributeSet)}
 * <li>{@link #remove(int, int)}
 * <li>{@link #createPosition(int)}
 * </ul>
 *
 * <p><b>Notification</b>
 * <p>
 * Mutations to the <code>Document</code> must be communicated to
 * interested observers.  The notification of change follows the event model
 * guidelines that are specified for JavaBeans.  In the JavaBeans
 * event model, once an event notification is dispatched, all listeners
 * must be notified before any further mutations occur to the source
 * of the event.  Further, order of delivery is not guaranteed.
 * <p>
 * Notification is provided as two separate events,
 * <a href="../event/DocumentEvent.html">DocumentEvent</a>, and
 * <a href="../event/UndoableEditEvent.html">UndoableEditEvent</a>.
 * If a mutation is made to a <code>Document</code> through its api,
 * a <code>DocumentEvent</code> will be sent to all of the registered
 * <code>DocumentListeners</code>.  If the <code>Document</code>
 * implementation supports undo/redo capabilities, an
 * <code>UndoableEditEvent</code> will be sent
 * to all of the registered <code>UndoableEditListener</code>s.
 * If an undoable edit is undone, a <code>DocumentEvent</code> should be
 * fired from the Document to indicate it has changed again.
 * In this case however, there should be no <code>UndoableEditEvent</code>
 * generated since that edit is actually the source of the change
 * rather than a mutation to the <code>Document</code> made through its
 * api.
 * <p style="text-align:center"><img src="doc-files/Document-notification.gif"
 * alt="The preceding text describes this graphic.">
 * <p>
 * Referring to the above diagram, suppose that the component shown
 * on the left mutates the document object represented by the blue
 * rectangle. The document responds by dispatching a DocumentEvent to
 * both component views and sends an UndoableEditEvent to the listening
 * logic, which maintains a history buffer.
 * <p>
 * Now suppose that the component shown on the right mutates the same
 * document.  Again, the document dispatches a DocumentEvent to both
 * component views and sends an UndoableEditEvent to the listening logic
 * that is maintaining the history buffer.
 * <p>
 * If the history buffer is then rolled back (i.e. the last UndoableEdit
 * undone), a DocumentEvent is sent to both views, causing both of them to
 * reflect the undone mutation to the document (that is, the
 * removal of the right component's mutation). If the history buffer again
 * rolls back another change, another DocumentEvent is sent to both views,
 * causing them to reflect the undone mutation to the document -- that is,
 * the removal of the left component's mutation.
 * <p>
 * The methods related to observing mutations to the document are:
 * <ul>
 *   <li>{@link #addDocumentListener(DocumentListener)}
 *   <li>{@link #removeDocumentListener(DocumentListener)}
 *   <li>{@link #addUndoableEditListener(UndoableEditListener)}
 *   <li>{@link #removeUndoableEditListener(UndoableEditListener)}
 * </ul>
 *
 * <p><b>Properties</b>
 * <p>
 * Document implementations will generally have some set of properties
 * associated with them at runtime.  Two well known properties are the
 * <a href="#StreamDescriptionProperty">StreamDescriptionProperty</a>,
 * which can be used to describe where the <code>Document</code> came from,
 * and the <a href="#TitleProperty">TitleProperty</a>, which can be used to
 * name the <code>Document</code>.  The methods related to the properties are:
 * <ul>
 * <li>{@link #getProperty(java.lang.Object)}
 * <li>{@link #putProperty(java.lang.Object, java.lang.Object)}
 * </ul>
 *
 * <p>For more information on the <code>Document</code> class, see
 * <a href="http://www.oracle.com/technetwork/java/javase/tech/articles-jsp-139072.html">The Swing Connection</a>
 * and most particularly the article,
 * <a href="http://java.sun.com/products/jfc/tsc/articles/text/element_interface">
 * The Element Interface</a>.
 *
 * @author  Timothy Prinzing
 *
 * @see javax.swing.event.DocumentEvent
 * @see javax.swing.event.DocumentListener
 * @see javax.swing.event.UndoableEditEvent
 * @see javax.swing.event.UndoableEditListener
 * @see Element
 * @see Position
 * @see AttributeSet
 */
public interface Document {

    
Returns number of characters of content currently
in the document.
Returns:
number of characters >= 0/**
     * Returns number of characters of content currently
     * in the document.
     *
     * @return number of characters &gt;= 0
     */
    public int getLength();

    
Registers the given observer to begin receiving notifications
when changes are made to the document.
Params:
listener – the observer to register
See Also:
removeDocumentListener/**
     * Registers the given observer to begin receiving notifications
     * when changes are made to the document.
     *
     * @param listener the observer to register
     * @see Document#removeDocumentListener
     */
    public void addDocumentListener(DocumentListener listener);

    
Unregisters the given observer from the notification list
so it will no longer receive change updates.
Params:
listener – the observer to register
See Also:
addDocumentListener/**
     * Unregisters the given observer from the notification list
     * so it will no longer receive change updates.
     *
     * @param listener the observer to register
     * @see Document#addDocumentListener
     */
    public void removeDocumentListener(DocumentListener listener);

    
Registers the given observer to begin receiving notifications
when undoable edits are made to the document.
Params:
listener – the observer to register
See Also:
UndoableEditEvent/**
     * Registers the given observer to begin receiving notifications
     * when undoable edits are made to the document.
     *
     * @param listener the observer to register
     * @see javax.swing.event.UndoableEditEvent
     */
    public void addUndoableEditListener(UndoableEditListener listener);

    
Unregisters the given observer from the notification list
so it will no longer receive updates.
Params:
listener – the observer to register
See Also:
UndoableEditEvent/**
     * Unregisters the given observer from the notification list
     * so it will no longer receive updates.
     *
     * @param listener the observer to register
     * @see javax.swing.event.UndoableEditEvent
     */
    public void removeUndoableEditListener(UndoableEditListener listener);

    
Gets the properties associated with the document.
Params:
key – a non-null property key
See Also:
putProperty(Object, Object)
Returns:
the properties/**
     * Gets the properties associated with the document.
     *
     * @param key a non-<code>null</code> property key
     * @return the properties
     * @see #putProperty(Object, Object)
     */
    public Object getProperty(Object key);

    
Associates a property with the document.  Two standard
property keys provided are: 
StreamDescriptionProperty and
TitleProperty.
Other properties, such as author, may also be defined.
Params:
key – the non-null property key
value – the property value
See Also:
getProperty(Object)/**
     * Associates a property with the document.  Two standard
     * property keys provided are: <a href="#StreamDescriptionProperty">
     * <code>StreamDescriptionProperty</code></a> and
     * <a href="#TitleProperty"><code>TitleProperty</code></a>.
     * Other properties, such as author, may also be defined.
     *
     * @param key the non-<code>null</code> property key
     * @param value the property value
     * @see #getProperty(Object)
     */
    public void putProperty(Object key, Object value);

    
Removes a portion of the content of the document.
This will cause a DocumentEvent of type
DocumentEvent.EventType.REMOVE to be sent to the
registered DocumentListeners, unless an exception
is thrown.  The notification will be sent to the
listeners by calling the removeUpdate method on the
DocumentListeners.

To ensure reasonable behavior in the face
of concurrency, the event is dispatched after the
mutation has occurred. This means that by the time a
notification of removal is dispatched, the document
has already been updated and any marks created by
createPosition have already changed.
For a removal, the end of the removal range is collapsed
down to the start of the range, and any marks in the removal
range are collapsed down to the start of the range.


If the Document structure changed as result of the removal,
the details of what Elements were inserted and removed in
response to the change will also be contained in the generated
DocumentEvent. It is up to the implementation of a Document
to decide how the structure should change in response to a
remove.

If the Document supports undo/redo, an UndoableEditEvent will
also be generated.
Params:
offs –  the offset from the beginning >= 0
len –   the number of characters to remove >= 0
Throws:
BadLocationException –  some portion of the removal range
  was not a valid part of the document.  The location in the exception
  is the first bad position encountered.
See Also:
DocumentEvent
DocumentListener
UndoableEditEvent
UndoableEditListener/**
     * Removes a portion of the content of the document.
     * This will cause a DocumentEvent of type
     * DocumentEvent.EventType.REMOVE to be sent to the
     * registered DocumentListeners, unless an exception
     * is thrown.  The notification will be sent to the
     * listeners by calling the removeUpdate method on the
     * DocumentListeners.
     * <p>
     * To ensure reasonable behavior in the face
     * of concurrency, the event is dispatched after the
     * mutation has occurred. This means that by the time a
     * notification of removal is dispatched, the document
     * has already been updated and any marks created by
     * <code>createPosition</code> have already changed.
     * For a removal, the end of the removal range is collapsed
     * down to the start of the range, and any marks in the removal
     * range are collapsed down to the start of the range.
     * <p style="text-align:center"><img src="doc-files/Document-remove.gif"
     *  alt="Diagram shows removal of 'quick' from 'The quick brown fox.'">
     * <p>
     * If the Document structure changed as result of the removal,
     * the details of what Elements were inserted and removed in
     * response to the change will also be contained in the generated
     * DocumentEvent. It is up to the implementation of a Document
     * to decide how the structure should change in response to a
     * remove.
     * <p>
     * If the Document supports undo/redo, an UndoableEditEvent will
     * also be generated.
     *
     * @param offs  the offset from the beginning &gt;= 0
     * @param len   the number of characters to remove &gt;= 0
     * @exception BadLocationException  some portion of the removal range
     *   was not a valid part of the document.  The location in the exception
     *   is the first bad position encountered.
     * @see javax.swing.event.DocumentEvent
     * @see javax.swing.event.DocumentListener
     * @see javax.swing.event.UndoableEditEvent
     * @see javax.swing.event.UndoableEditListener
     */
    public void remove(int offs, int len) throws BadLocationException;

    
Inserts a string of content.  This will cause a DocumentEvent
of type DocumentEvent.EventType.INSERT to be sent to the
registered DocumentListers, unless an exception is thrown.
The DocumentEvent will be delivered by calling the
insertUpdate method on the DocumentListener.
The offset and length of the generated DocumentEvent
will indicate what change was actually made to the Document.


If the Document structure changed as result of the insertion,
the details of what Elements were inserted and removed in
response to the change will also be contained in the generated
DocumentEvent.  It is up to the implementation of a Document
to decide how the structure should change in response to an
insertion.

If the Document supports undo/redo, an UndoableEditEvent will
also be generated.
Params:
offset –  the offset into the document to insert the content >= 0.
   All positions that track change at or after the given location
   will move.
str –    the string to insert
a –      the attributes to associate with the inserted
  content.  This may be null if there are no attributes.
Throws:
BadLocationException –  the given insert position is not a valid
position within the document
See Also:
DocumentEvent
DocumentListener
UndoableEditEvent
UndoableEditListener/**
     * Inserts a string of content.  This will cause a DocumentEvent
     * of type DocumentEvent.EventType.INSERT to be sent to the
     * registered DocumentListers, unless an exception is thrown.
     * The DocumentEvent will be delivered by calling the
     * insertUpdate method on the DocumentListener.
     * The offset and length of the generated DocumentEvent
     * will indicate what change was actually made to the Document.
     * <p style="text-align:center"><img src="doc-files/Document-insert.gif"
     *  alt="Diagram shows insertion of 'quick' in 'The quick brown fox'">
     * <p>
     * If the Document structure changed as result of the insertion,
     * the details of what Elements were inserted and removed in
     * response to the change will also be contained in the generated
     * DocumentEvent.  It is up to the implementation of a Document
     * to decide how the structure should change in response to an
     * insertion.
     * <p>
     * If the Document supports undo/redo, an UndoableEditEvent will
     * also be generated.
     *
     * @param offset  the offset into the document to insert the content &gt;= 0.
     *    All positions that track change at or after the given location
     *    will move.
     * @param str    the string to insert
     * @param a      the attributes to associate with the inserted
     *   content.  This may be null if there are no attributes.
     * @exception BadLocationException  the given insert position is not a valid
     * position within the document
     * @see javax.swing.event.DocumentEvent
     * @see javax.swing.event.DocumentListener
     * @see javax.swing.event.UndoableEditEvent
     * @see javax.swing.event.UndoableEditListener
     */
    public void insertString(int offset, String str, AttributeSet a) throws BadLocationException;

    
Fetches the text contained within the given portion
of the document.
Params:
offset –  the offset into the document representing the desired
  start of the text >= 0
length –  the length of the desired string >= 0
Throws:
BadLocationException –  some portion of the given range
  was not a valid part of the document.  The location in the exception
  is the first bad position encountered.
Returns:
the text, in a String of length >= 0/**
     * Fetches the text contained within the given portion
     * of the document.
     *
     * @param offset  the offset into the document representing the desired
     *   start of the text &gt;= 0
     * @param length  the length of the desired string &gt;= 0
     * @return the text, in a String of length &gt;= 0
     * @exception BadLocationException  some portion of the given range
     *   was not a valid part of the document.  The location in the exception
     *   is the first bad position encountered.
     */
    public String getText(int offset, int length) throws BadLocationException;

    
Fetches the text contained within the given portion
of the document.

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:

  int nleft = doc.getDocumentLength();
  Segment text = new Segment();
  int offs = 0;
  text.setPartialReturn(true);
  while (nleft > 0) {
      doc.getText(offs, nleft, text);
      // do someting with text
      nleft -= text.count;
      offs += text.count;
  }

Params:
offset –  the offset into the document representing the desired
  start of the text >= 0
length –  the length of the desired string >= 0
txt – the Segment object to return the text in
Throws:
BadLocationException –  Some portion of the given range
  was not a valid part of the document.  The location in the exception
  is the first bad position encountered./**
     * 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:
     *
     * <pre><code>
     *
     * &nbsp; int nleft = doc.getDocumentLength();
     * &nbsp; Segment text = new Segment();
     * &nbsp; int offs = 0;
     * &nbsp; text.setPartialReturn(true);
     * &nbsp; while (nleft &gt; 0) {
     * &nbsp;     doc.getText(offs, nleft, text);
     * &nbsp;     // do someting with text
     * &nbsp;     nleft -= text.count;
     * &nbsp;     offs += text.count;
     * &nbsp; }
     *
     * </code></pre>
     *
     * @param offset  the offset into the document representing the desired
     *   start of the text &gt;= 0
     * @param length  the length of the desired string &gt;= 0
     * @param txt the Segment object to return the text in
     *
     * @exception BadLocationException  Some portion of the given range
     *   was not a valid part of the document.  The location in the exception
     *   is the first bad position encountered.
     */
    public void getText(int offset, int length, Segment txt) throws BadLocationException;

    
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.
Returns:
the position/**
     * 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 Position getStartPosition();

    
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.
Returns:
the position/**
     * 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 Position getEndPosition();

    
This method allows an application to mark a place in
a sequence of character content. This mark can then be
used to tracks change as insertions and removals are made
in the content. The policy is that insertions always
occur prior to the current position (the most common case)
unless the insertion location is zero, in which case the
insertion is forced to a position that follows the
original position.
Params:
offs –  the offset from the start of the document >= 0
Throws:
BadLocationException –  if the given position does not
  represent a valid location in the associated document
Returns:
the position/**
     * This method allows an application to mark a place in
     * a sequence of character content. This mark can then be
     * used to tracks change as insertions and removals are made
     * in the content. The policy is that insertions always
     * occur prior to the current position (the most common case)
     * unless the insertion location is zero, in which case the
     * insertion is forced to a position that follows the
     * original position.
     *
     * @param offs  the offset from the start of the document &gt;= 0
     * @return the position
     * @exception BadLocationException  if the given position does not
     *   represent a valid location in the associated document
     */
    public Position createPosition(int offs) throws BadLocationException;

    
Returns all of the root elements that are defined.

Typically there will be only one document structure, but the interface
supports building an arbitrary number of structural projections over the
text data. The document can have multiple root elements to support
multiple document structures.  Some examples might be:


Text direction.
Lexical token streams.
Parse trees.
Conversions to formats other than the native format.
Modification specifications.
Annotations.

Returns:
the root element/**
     * Returns all of the root elements that are defined.
     * <p>
     * Typically there will be only one document structure, but the interface
     * supports building an arbitrary number of structural projections over the
     * text data. The document can have multiple root elements to support
     * multiple document structures.  Some examples might be:
     * </p>
     * <ul>
     * <li>Text direction.
     * <li>Lexical token streams.
     * <li>Parse trees.
     * <li>Conversions to formats other than the native format.
     * <li>Modification specifications.
     * <li>Annotations.
     * </ul>
     *
     * @return the root element
     */
    public Element[] getRootElements();

    
Returns the root element that views should be based upon,
unless some other mechanism for assigning views to element
structures is provided.
Returns:
the root element/**
     * 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
     */
    public Element getDefaultRootElement();

    
Allows the model to be safely rendered in the presence
of concurrency, 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 not
make any mutations.
Params:
r – a Runnable used to render the model/**
     * Allows the model to be safely rendered in the presence
     * of concurrency, 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.
     *
     * @param r a <code>Runnable</code> used to render the model
     */
    public void render(Runnable r);

    
The property name for the description of the stream
used to initialize the document.  This should be used
if the document was initialized from a stream and
anything is known about the stream.
/**
     * The property name for the description of the stream
     * used to initialize the document.  This should be used
     * if the document was initialized from a stream and
     * anything is known about the stream.
     */
    public static final String StreamDescriptionProperty = "stream";

    
The property name for the title of the document, if
there is one.
/**
     * The property name for the title of the document, if
     * there is one.
     */
    public static final String TitleProperty = "title";


}