bundles/org.eclipse.ui/Eclipse JFace Text/org/eclipse/jface/text/IUndoManager.java

package org.eclipse.jface.text;

/*
 * (c) Copyright IBM Corp. 2000, 2001.
 * All Rights Reserved.
 */


/**
 * An undo manager is connected to at most one text viewer.
 * It monitors the text viewer and keeps a history of the 
 * changes applied to the viewer. The undo manager groups those
 * changes into user interactions which on an undo request are 
 * rolled back in one atomic change. <p>
 * Clients may implement this interface or use the standard
 * implementation <code>DefaultUndoManager</code>.
 */
public interface IUndoManager {

	/**
	 * Connects this undo manager to the given text viewer.
	 *
	 * @param viewer the viewer the undo manager is connected to
	 */
	void connect(ITextViewer viewer);
	
	/**
	 * Disconnects this undo manager from its text viewer. 
	 * If this undo manager hasn't been connected before this
	 * operation has no effect.
	 */
	void disconnect();
	
	/**
	 * 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 
	 * <code>beginCompoundChange</code> has been finished. All subsequent changes
	 * are considered to be individually undoable.
	 */
	void endCompoundChange();
	
	/**
	 * Resets the history of the undo manager. After that call,
	 * there aren't any undoable or redoable text changes.
	 */
	void reset();
	
	/**
	 * The given parameter determines the maximal length of the history
	 * remembered by the undo manager.
	 *
	 * @param undoLevel the length of this undo manager's history
	 */
	void setMaximalUndoLevel(int undoLevel);
	
	/**
	 * 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.
	 *
	 * @return <code>true</code> if at least on text change can be repeated
	 */
	boolean redoable();
	
	/**
	 * Rolls back the most recently executed text change.
	 */
	void undo();
	
	/**
	 * Repeats the most recently rolled back text change.
	 */
	void redo();

}