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Java > Open Source Codes > org > eclipse > core > commands > operations > IOperationApprover2


1 /*******************************************************************************
2  * Copyright (c) 2006 IBM Corporation and others.
3  * All rights reserved. This program and the accompanying materials
4  * are made available under the terms of the Eclipse Public License v1.0
5  * which accompanies this distribution, and is available at
6  * http://www.eclipse.org/legal/epl-v10.html
7  *
8  * Contributors:
9  * IBM Corporation - initial API and implementation
10  *******************************************************************************/
11 package org.eclipse.core.commands.operations;
12
13 import org.eclipse.core.runtime.IAdaptable;
14 import org.eclipse.core.runtime.IStatus;
15
16 /**
17  * Extends {@link IOperationApprover} to approve the execution of a particular
18  * operation within an operation history. Operations that are candidates for
19  * execution have already been validated against their current state and
20  * according to the rules of the history. Prior to 3.2, an operation approver
21  * was only consulted for undo and redo of an operation, not its initial
22  * execution.
23  * <p>
24  * By the time an IOperationApprover2 is consulted, the execution has already
25  * been requested and it has been determined that the operation is valid.
26  * Approvers should return an <code>IStatus</code> object with severity
27  * <code>OK</code> if the operation should proceed, and any other severity if
28  * it should not. When an operation is not approved, it is expected that the
29  * object not allowing the operation has already consulted the user if necessary
30  * or otherwise provided any necessary information to the user about the fact
31  * that the operation is not approved.
32  * </p>
33  * <p>
34  * Like {@link IOperationApprover}, implementers of this extension must be
35  * prepared to receive the approval messages from a background thread. Any UI
36  * access occurring inside the implementation must be properly synchronized
37  * using the techniques specified by the client's widget library.
38  * </p>
39  *
40  * @since 3.2
41  */
42 public interface IOperationApprover2 extends IOperationApprover {
43     /**
44      * Return a status indicating whether the specified operation should be
45      * executed. Any status that does not have severity <code>IStatus.OK</code>
46      * will not be approved. Implementers should not assume that the execution
47      * will be performed when the status is <code>OK</code>, since other
48      * operation approvers may veto the execution.
49      *
50      * @param operation
51      * the operation to be executed
52      * @param history
53      * the history performing the execution of the operation
54      * @param info
55      * the IAdaptable (or <code>null</code>) provided by the
56      * caller in order to supply UI information for prompting the
57      * user if necessary. When this parameter is not
58      * <code>null</code>, it should minimally contain an adapter
59      * for the org.eclipse.swt.widgets.Shell.class. Even if UI
60      * information is provided, the implementation of this method
61      * must be prepared for being called from a background thread.
62      * Any UI access must be properly synchronized using the
63      * techniques specified by the client's widget library.
64      * @return the IStatus describing whether the operation is approved. The
65      * execution will not proceed if the status severity is not
66      * <code>OK</code>, and the caller requesting the execution will
67      * be returned the status that caused the rejection. Any other
68      * status severities will not be interpreted by the history.
69      */
70     IStatus proceedExecuting(IUndoableOperation operation,
71             IOperationHistory history, IAdaptable info);
72 }
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