001/* A request to redo.
002
003 Copyright (c) 2000-2014 The Regents of the University of California.
004 All rights reserved.
005 Permission is hereby granted, without written agreement and without
006 license or royalty fees, to use, copy, modify, and distribute this
007 software and its documentation for any purpose, provided that the above
008 copyright notice and the following two paragraphs appear in all copies
009 of this software.
010
011 IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
012 FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
013 ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
014 THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
015 SUCH DAMAGE.
016
017 THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
018 INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
019 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
020 PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
021 CALIFORNIA HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
022 ENHANCEMENTS, OR MODIFICATIONS.
023
024 PT_COPYRIGHT_VERSION_2
025 COPYRIGHTENDKEY
026 */
027package ptolemy.kernel.undo;
028
029import ptolemy.kernel.util.ChangeRequest;
030import ptolemy.kernel.util.InternalErrorException;
031import ptolemy.kernel.util.NamedObj;
032
033///////////////////////////////////////////////////////////////////
034////
035
036/**
037 A change request to redo. When executed, this change request will
038 identify the undo stack associated with the specified context,
039 and it will execute the top redo action on that stack, if there is
040 one.
041 <p>
042 @author Edward A. Lee and Neil Smyth
043 @version $Id$
044 @since Ptolemy II 4.0
045 @Pt.ProposedRating Green (eal)
046 @Pt.AcceptedRating Green (hyzheng)
047 */
048public class RedoChangeRequest extends ChangeRequest {
049    /** Construct a change request to be executed in the specified context.
050     *  The redo stack associated with the specified context will be used.
051     *  That stack is the one returned by UndoStackAttribute.getUndoInfo().
052     *  @see UndoStackAttribute
053     *  @param originator The originator of the change request.
054     *  @param context The context in which to execute the MoML.
055     */
056    public RedoChangeRequest(Object originator, NamedObj context) {
057        super(originator, "Request to redo.");
058        _context = context;
059    }
060
061    ///////////////////////////////////////////////////////////////////
062    ////                         public methods                    ////
063
064    /** Return the context specified in the constructor, or null if none
065     *  was specified.
066     *  @return The context.
067     */
068    public NamedObj getContext() {
069        return _context;
070    }
071
072    ///////////////////////////////////////////////////////////////////
073    ////                         protected methods                 ////
074
075    /** Execute the change by invoking redo on the undo stack of
076     *  the context specified in the constructor.
077     *  @exception Exception If an exception is thrown
078     *   while evaluating the request.
079     */
080    @Override
081    protected void _execute() throws Exception {
082        // Check to see whether there is a context...
083        if (_context == null) {
084            throw new InternalErrorException("Context is unexpectedly null.");
085        }
086
087        UndoStackAttribute undoStack = UndoStackAttribute.getUndoInfo(_context);
088
089        // The undo action may involve several subactions.
090        // These may queue further change requests.
091        // Collect these change requests without executing them
092        // until after the whole action is completed.
093        boolean previous = _context.isDeferringChangeRequests();
094
095        try {
096            previous = _context.isDeferringChangeRequests();
097            _context.setDeferringChangeRequests(true);
098            undoStack.redo();
099        } finally {
100            _context.setDeferringChangeRequests(previous);
101        }
102    }
103
104    ///////////////////////////////////////////////////////////////////
105    ////                         private variables                 ////
106    // The context in which to execute the request.
107    private NamedObj _context;
108}