bundles/org.eclipse.gef/src/org/eclipse/gef/ui/properties/ResetValueCommand.java

/*******************************************************************************
 * Copyright (c) 2000, 2010 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.gef.ui.properties;

import org.eclipse.ui.views.properties.IPropertySource;
import org.eclipse.ui.views.properties.IPropertySource2;

import org.eclipse.gef.commands.Command;
import org.eclipse.gef.internal.GEFMessages;

/**
 * A Command used to restore the default value of a property.
 * 
 * @author Pratik Shah
 */
class ResetValueCommand extends Command {

	/** the property that has to be reset */
	protected Object propertyName;
	/** the current non-default value of the property */
	protected Object undoValue;
	/** the property source whose property has to be reset */
	protected IPropertySource target;

	/**
	 * Default Constructor: Sets the label for the Command
	 * 
	 * @since 3.1
	 */
	public ResetValueCommand() {
		super(GEFMessages.RestoreDefaultValueCommand_Label);
	}

	/**
	 * Returns <code>true</code> IFF:<br>
	 * 1) the target and property have been specified<br>
	 * 2) the property has a default value<br>
	 * 3) the value set for that property is not the default
	 * 
	 * @see org.eclipse.gef.commands.Command#canExecute()
	 */
	public boolean canExecute() {
		boolean answer = false;
		if (target != null && propertyName != null) {
			answer = target.isPropertySet(propertyName);
			if (target instanceof IPropertySource2)
				answer = answer
						&& (((IPropertySource2) target)
								.isPropertyResettable(propertyName));
		}
		return answer;
	}

	/**
	 * Caches the undo value and invokes redo()
	 * 
	 * @see org.eclipse.gef.commands.Command#execute()
	 */
	public void execute() {
		undoValue = target.getPropertyValue(propertyName);
		if (undoValue instanceof IPropertySource)
			undoValue = ((IPropertySource) undoValue).getEditableValue();
		redo();
	}

	/**
	 * Sets the IPropertySource.
	 * 
	 * @param propSource
	 *            the IPropertySource whose property has to be reset
	 */
	public void setTarget(IPropertySource propSource) {
		target = propSource;
	}

	/**
	 * Resets the specified property on the specified IPropertySource
	 * 
	 * @see org.eclipse.gef.commands.Command#redo()
	 */
	public void redo() {
		target.resetPropertyValue(propertyName);
	}

	/**
	 * Sets the property that is to be reset.
	 * 
	 * @param pName
	 *            the property to be reset
	 */
	public void setPropertyId(Object pName) {
		propertyName = pName;
	}

	/**
	 * Restores the non-default value that was reset.
	 * 
	 * @see org.eclipse.gef.commands.Command#undo()
	 */
	public void undo() {
		target.setPropertyValue(propertyName, undoValue);
	}

}