Copyright (c) 2006, 2008 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2006, 2008 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.text.undo;

import org.eclipse.core.commands.ExecutionException;
import org.eclipse.core.commands.operations.IUndoContext;

Interface for a document undo manager. Tracks changes in a document and
builds a history of text commands that describe the undoable changes to the
document.

Clients must explicitly connect to the undo manager to express their interest
in the undo history. Clients should disconnect from the undo manager when
they are no longer interested in tracking the undo history. If there are no
clients connected to the undo manager, it will not track the document's
changes and will dispose of any history that was previously kept.

Clients may also listen to the undo manager for notifications before and
after undo or redo events are performed. Clients must connect to the undo
manager in addition to registering listeners.

Clients may implement this interface.

See Also:
DocumentUndoManagerRegistry
IDocumentUndoListener
IDocument
Since:
3.2/**
 * Interface for a document undo manager. Tracks changes in a document and
 * builds a history of text commands that describe the undoable changes to the
 * document.
 * <p>
 * Clients must explicitly connect to the undo manager to express their interest
 * in the undo history. Clients should disconnect from the undo manager when
 * they are no longer interested in tracking the undo history. If there are no
 * clients connected to the undo manager, it will not track the document's
 * changes and will dispose of any history that was previously kept.</p>
 * <p>
 * Clients may also listen to the undo manager for notifications before and
 * after undo or redo events are performed. Clients must connect to the undo
 * manager in addition to registering listeners.</p>
 * <p>
 * Clients may implement this interface.
 * </p>
 *
 * @see DocumentUndoManagerRegistry
 * @see IDocumentUndoListener
 * @see org.eclipse.jface.text.IDocument
 * @since 3.2
 */
public interface IDocumentUndoManager {

	
Adds the specified listener to the list of document undo listeners that
are notified before and after changes are undone or redone in the
document. This method has no effect if the instance being added is
already in the list.

Notifications will not be received if there are no clients connected to
the receiver. Registering a document undo listener does not implicitly
connect the listener to the receiver.

Document undo listeners must be prepared to receive notifications from a
background thread. Any UI access occurring inside the implementation must
be properly synchronized using the techniques specified by the client's
widget library.
Params:
listener – the document undo listener to be added as a listener/**
	 * Adds the specified listener to the list of document undo listeners that
	 * are notified before and after changes are undone or redone in the
	 * document. This method has no effect if the instance being added is
	 * already in the list.
	 * <p>
	 * Notifications will not be received if there are no clients connected to
	 * the receiver. Registering a document undo listener does not implicitly
	 * connect the listener to the receiver.</p>
	 * <p>
	 * Document undo listeners must be prepared to receive notifications from a
	 * background thread. Any UI access occurring inside the implementation must
	 * be properly synchronized using the techniques specified by the client's
	 * widget library.</p>
	 *
	 * @param listener the document undo listener to be added as a listener
	 */
	void addDocumentUndoListener(IDocumentUndoListener listener);

	
Removes the specified listener from the list of document undo listeners.

Removing a listener which is not registered has no effect

Params:
listener – the document undo listener to be removed/**
	 * Removes the specified listener from the list of document undo listeners.
	 * <p>
	 * Removing a listener which is not registered has no effect
	 * </p>
	 *
	 * @param listener the document undo listener to be removed
	 */
	void removeDocumentUndoListener(IDocumentUndoListener listener);

	
Returns the undo context registered for this document
Returns:
the undo context registered for this document/**
	 * Returns the undo context registered for this document
	 *
	 * @return the undo context registered for this document
	 */
	IUndoContext getUndoContext();

	
Closes the currently open text edit and open a new one.
/**
	 * Closes the currently open text edit and open a new one.
	 */
	void commit();

	
Connects to the undo manager. Used to signify that a client is monitoring
the history kept by the undo manager. This message has no effect if the
client is already connected.
Params:
client – the object connecting to the undo manager/**
	 * Connects to the undo manager. Used to signify that a client is monitoring
	 * the history kept by the undo manager. This message has no effect if the
	 * client is already connected.
	 *
	 * @param client the object connecting to the undo manager
	 */
	void connect(Object client);

	
Disconnects from the undo manager. Used to signify that a client is no
longer monitoring the history kept by the undo manager. If all clients
have disconnected from the undo manager, the undo history will be
deleted.
Params:
client – the object disconnecting from the undo manager/**
	 * Disconnects from the undo manager. Used to signify that a client is no
	 * longer monitoring the history kept by the undo manager. If all clients
	 * have disconnected from the undo manager, the undo history will be
	 * deleted.
	 *
	 * @param client the object disconnecting from the undo manager
	 */
	void disconnect(Object client);

	
Signals the undo manager that all subsequent changes until
endCompoundChange is called are to be undone in one piece.
/**
	 * Signals the undo manager that all subsequent changes until
	 * <code>endCompoundChange</code> is called are to be undone in one piece.
	 */
	void beginCompoundChange();

	
Signals the undo manager that the sequence of changes which started with
beginCompoundChange has been finished. All subsequent
changes are considered to be individually undo-able.
/**
	 * Signals the undo manager that the sequence of changes which started with
	 * <code>beginCompoundChange</code> has been finished. All subsequent
	 * changes are considered to be individually undo-able.
	 */
	void endCompoundChange();

	
Sets the limit of the undo history to the specified value. The provided
limit will supersede any previously set limit.
Params:
undoLimit – the length of this undo manager's history/**
	 * Sets the limit of the undo history to the specified value. The provided
	 * limit will supersede any previously set limit.
	 *
	 * @param undoLimit the length of this undo manager's history
	 */
	void setMaximalUndoLevel(int undoLimit);

	
Resets the history of the undo manager. After that call,
there aren't any undo-able or redo-able text changes.
/**
	 * Resets the history of the undo manager. After that call,
	 * there aren't any undo-able or redo-able text changes.
	 */
	void reset();

	
Returns whether at least one text change can be rolled back.
Returns:
true if at least one text change can be rolled back/**
	 * Returns whether at least one text change can be rolled back.
	 *
	 * @return <code>true</code> if at least one text change can be rolled back
	 */
	boolean undoable();

	
Returns whether at least one text change can be repeated. A text change
can be repeated only if it was executed and rolled back.
Returns:
true if at least on text change can be repeated/**
	 * Returns whether at least one text change can be repeated. A text change
	 * can be repeated only if it was executed and rolled back.
	 *
	 * @return <code>true</code> if at least on text change can be repeated
	 */
	boolean redoable();

	
Rolls back the most recently executed text change.
Throws:
ExecutionException – if an exception occurred during undo/**
	 * Rolls back the most recently executed text change.
	 *
	 * @throws ExecutionException if an exception occurred during undo
	 */
	void undo() throws ExecutionException;

	
Repeats the most recently rolled back text change.
Throws:
ExecutionException – if an exception occurred during redo/**
	 * Repeats the most recently rolled back text change.
	 *
	 * @throws ExecutionException if an exception occurred during redo
	 */
	void redo() throws ExecutionException;

	
Transfers the undo history from the specified document undo manager to
this undo manager.  This message should only be used when it is known
that the content of the document of the original undo manager when the
last undo operation was recorded is the same as this undo manager's
current document content, since the undo history is based on document
indexes.  It is the responsibility of the caller
to ensure that this call is used correctly.
Params:
manager – the document undo manger whose history is to be transferred to the receiver/**
	 * Transfers the undo history from the specified document undo manager to
	 * this undo manager.  This message should only be used when it is known
	 * that the content of the document of the original undo manager when the
	 * last undo operation was recorded is the same as this undo manager's
	 * current document content, since the undo history is based on document
	 * indexes.  It is the responsibility of the caller
	 * to ensure that this call is used correctly.
	 *
	 * @param manager the document undo manger whose history is to be transferred to the receiver
	 */
	public void transferUndoHistory(IDocumentUndoManager manager);

}