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/*******************************************************************************
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* Copyright (c) 2000, 2010 IBM Corporation and others.
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* All rights reserved. This program and the accompanying materials
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* are made available under the terms of the Eclipse Public License v1.0
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* which accompanies this distribution, and is available at
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* http://www.eclipse.org/legal/epl-v10.html
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*
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* Contributors:
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* IBM Corporation - initial API and implementation
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*******************************************************************************/
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package org.eclipse.gef.commands;
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/**
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* An Abstract implementation of {@link Command}.
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*
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* @author hudsonr
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* @since 2.0
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*/
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public abstract class Command {
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private String label;
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private String debugLabel;
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/**
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* Constructs a Command with no label.
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*/
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public Command() {
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}
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/**
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* Constructs a Command with the specified label.
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*
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* @param label
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* the Command's label
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*/
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public Command(String label) {
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setLabel(label);
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}
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/**
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* @return <code>true</code> if the command can be executed
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*/
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public boolean canExecute() {
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return true;
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}
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/**
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* @return <code>true</code> if the command can be undone. This method
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* should only be called after <code>execute()</code> or
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* <code>redo()</code> has been called.
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*/
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public boolean canUndo() {
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return true;
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}
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/**
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* Returns a Command that represents the chaining of a specified Command to
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* this Command. The Command being chained will <code>execute()</code> after
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* this command has executed, and it will <code>undo()</code> before this
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* Command is undone.
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*
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* @param command
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* <code>null</code> or the Command being chained
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* @return a Command representing the union
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*/
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public Command chain(Command command) {
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if (command == null)
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return this;
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class ChainedCompoundCommand extends CompoundCommand {
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public Command chain(Command c) {
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add(c);
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return this;
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}
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}
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CompoundCommand result = new ChainedCompoundCommand();
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result.setDebugLabel("Chained Commands"); //$NON-NLS-1$
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result.add(this);
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result.add(command);
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return result;
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}
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/**
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* This is called to indicate that the <code>Command</code> will not be used
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* again. The Command may be in any state (executed, undone or redone) when
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* dispose is called. The Command should not be referenced in any way after
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* it has been disposed.
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*/
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public void dispose() {
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}
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/**
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* executes the Command. This method should not be called if the Command is
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* not executable.
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*/
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public void execute() {
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}
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/**
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* @return an untranslated String used for debug purposes only
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*/
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public String getDebugLabel() {
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return debugLabel + ' ' + getLabel();
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}
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/**
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* @return a String used to describe this command to the User
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*/
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public String getLabel() {
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return label;
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}
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/**
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* Re-executes the Command. This method should only be called after
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* <code>undo()</code> has been called.
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*/
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public void redo() {
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execute();
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}
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/**
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* Sets the debug label for this command
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*
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* @param label
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* a description used for debugging only
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*/
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public void setDebugLabel(String label) {
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debugLabel = label;
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}
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/**
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* Sets the label used to describe this command to the User.
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*
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* @param label
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* the label
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*/
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public void setLabel(String label) {
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this.label = label;
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}
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/**
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* Undoes the changes performed during <code>execute()</code>. This method
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* should only be called after <code>execute</code> has been called, and
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* only when <code>canUndo()</code> returns <code>true</code>.
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*
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* @see #canUndo()
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*/
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public void undo() {
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}
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}
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