/*******************************************************************************
 * Copyright (c) 2000, 2004 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.jface.viewers;

/**
 * A cell modifier is used to access the data model from a cell
 * editor in an abstract way. It offers methods to:
 * <ul>
 *	<li>to check if a a model element's property can be edited or not</li>
 *	<li>retrieve a value a model element's property</li>
 *	<li>to store a cell editor's value back into the model 
 *    element's property</li>
 * </ul>
 * <p>
 * This interface should be implemented by classes that wish to
 * act as cell modifiers.
 * </p>
 */
public interface ICellModifier {
    /**
     * Checks whether the given property of the given element can be 
     * modified.
     *
     * @param element the element
     * @param property the property
     * @return <code>true</code> if the property can be modified,
     *   and <code>false</code> if it is not modifiable
     */
    public boolean canModify(Object element, String property);

    /**
     * Returns the value for the given property of the given element.
     * Returns <code>null</code> if the element does not have the given property.
     *
     * @param element the element
     * @param property the property
     * @return the property value
     */
    public Object getValue(Object element, String property);

    /**
     * Modifies the value for the given property of the given element.
     * Has no effect if the element does not have the given property,
     * or if the property cannot be modified.
     * <p>
     * Note that it is possible for an SWT Item to be passed instead of 
     * the model element. To handle this case in a safe way, use: 
     * <pre>
     *     if (element instanceof Item) {
     *         element = ((Item) element).getData();
     *     }
     *     // modify the element's property here
     * </pre>
     * </p>
     * 
     * @param element the model element or SWT Item (see above)
     * @param property the property
     * @param value the new property value
     * 
     * @see org.eclipse.swt.widgets.Item
     */
    public void modify(Object element, String property, Object value);
}