/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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();
}