/*******************************************************************************
* Copyright (c) 2005 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.core.commands.operations;
import org.eclipse.core.runtime.IAdaptable;
import org.eclipse.core.runtime.IStatus;
/**
* <p>
* IOperationApprover defines an interface for approving the undo or redo of a
* particular operation within an operation history. Operations that are
* candidates for undo or redo have already been validated against their current
* state and according to the rules of the history.
* </p>
* <p>
* By the time an IOperationApprover is consulted, the undo has already been
* requested. Approvers should return an <code>IStatus</code> object with
* severity <code>OK</code> if the operation should proceed, and any other
* severity if it should not. When an operation is not approved, it is expected
* that the object not allowing the operation has already consulted the user if
* necessary or otherwise provided any necessary information to the user about
* the fact that the operation is not approved.
* </p>
* <p>
* Operation approvers must be prepared to receive the approval messages from a
* background thread. Any UI access occurring inside the implementation must be
* properly synchronized using the techniques specified by the client's widget
* library.
* </p>
*
* @since 3.1
*/
public interface IOperationApprover {
/**
* Return a status indicating whether the specified operation should be
* redone. Any status that does not have severity <code>IStatus.OK</code>
* will not be approved. Implementers should not assume that the redo will
* be performed when the status is <code>OK</code>, since other operation
* approvers may veto the redo.
*
* @param operation
* the operation to be redone
* @param history
* the history redoing the operation
* @param info
* the IAdaptable (or <code>null</code>) provided by the
* caller in order to supply UI information for prompting the
* user if necessary. When this parameter is not
* <code>null</code>, it should minimally contain an adapter
* for the org.eclipse.swt.widgets.Shell.class. Even if UI
* information is provided, the implementation of this method
* must be prepared for being called from a background thread.
* Any UI access must be properly synchronized using the
* techniques specified by the client's widget library.
* @return the IStatus describing whether the operation is approved. The
* redo will not proceed if the status severity is not
* <code>OK</code>, and the caller requesting the redo will be
* returned the status that caused the rejection. Any other status
* severities will not be interpreted by the history.
*/
IStatus proceedRedoing(IUndoableOperation operation,
IOperationHistory history, IAdaptable info);
/**
* Return a status indicating whether the specified operation should be
* undone. Any status that does not have severity <code>IStatus.OK</code>
* will not be approved. Implementers should not assume that the undo will
* be performed when the status is <code>OK</code>, since other operation
* approvers can veto the undo.
*
* @param operation
* the operation to be undone
* @param history
* the history undoing the operation
* @param info
* the IAdaptable (or <code>null</code>) provided by the
* caller in order to supply UI information for prompting the
* user if necessary. When this parameter is not
* <code>null</code>, it should minimally contain an adapter
* for the org.eclipse.swt.widgets.Shell.class. Even if UI
* information is provided, the implementation of this method
* must be prepared for being called from a background thread.
* Any UI access must be properly synchronized using the
* techniques specified by the client's widget library.
* @return the IStatus describing whether the operation is approved. The
* undo will not proceed if the status severity is not
* <code>OK</code>, and the caller requesting the undo will be
* returned the status that caused the rejection. Any other status
* severities will not be interpreted by the history.
*/
IStatus proceedUndoing(IUndoableOperation operation,
IOperationHistory history, IAdaptable info);
}
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