/**
* Copyright 2010 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package org.waveprotocol.wave.model.undo;
import org.waveprotocol.wave.model.util.Pair;
/**
* An <code>UndoManager</code> that provides versions of the undo and redo
* methods which return more information.
*
*
* @param <T> The type of operations.
*/
public interface UndoManagerPlus<T> extends UndoManager<T> {
/**
* Effects an undo. Returns null if there are no operations to undo.
*
* NOTE(user): Warning. This interface method may change.
*
* @return a pair containing the operation that will effect an undo and the
* relevant transformed non-undoable operation (which may be null if
* no such operation exists)
*
* NOTE(user): Returning null is probably slightly harder to use than
* returning an operation that does nothing.
*/
Pair<T, T> undoPlus();
/**
* Effects a redo. Returns null if there are no operations to redo.
*
* NOTE(user): Warning. This interface method may change.
*
* @return a pair containing the operation that will effect a redo and the
* relevant transformed non-undoable operation (which may be null if
* no such operation exists)
*
* NOTE(user): Returning null is probably slightly harder to use than
* returning an operation that does nothing.
*/
Pair<T, T> redoPlus();
}