/*******************************************************************************
 * Copyright (c) 2000, 2003 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.viewers;

import java.util.ArrayList;
/**
 * A viewer filter is used by a structured viewer to
 * extract a subset of elements provided by its content provider.
 * <p>
 * Subclasses must implement the <code>select</code> method
 * and may implement the <code>isFilterProperty</code> method.
 * </p>
 * @see IStructuredContentProvider
 * @see StructuredViewer
 */
public abstract class ViewerFilter {
/**
 * Creates a new viewer filter.
 */
protected ViewerFilter() {
}
/**
 * Filters the given elements for the given viewer.
 * The input array is not modified.
 * <p>
 * The default implementation of this method calls 
 * <code>select</code> on each element in the array, 
 * and returns only those elements for which <code>select</code>
 * returns <code>true</code>.
 * </p>
 * @param viewer the viewer
 * @param parent the parent element
 * @param elements the elements to filter
 * @return the filtered elements
 */
public Object[] filter(Viewer viewer, Object parent, Object[] elements) {
	int size = elements.length;
	ArrayList out = new ArrayList(size);
	for (int i = 0; i < size; ++i) {
		Object element = elements[i];
		if (select(viewer, parent, element))
			out.add(element);
	}
	return out.toArray();
}
/**
 * Returns whether this viewer filter would be affected 
 * by a change to the given property of the given element.
 * <p>
 * The default implementation of this method returns <code>false</code>.
 * Subclasses should reimplement.
 * </p>
 *
 * @param element the element
 * @param property the property
 * @return <code>true</code> if the filtering would be affected,
 *    and <code>false</code> if it would be unaffected
 */
public boolean isFilterProperty(Object element, String property) {
	return false;
}
/**
 * Returns whether the given element makes it through this filter.
 *
 * @param viewer the viewer
 * @param parentElement the parent element
 * @param element the element
 * @return <code>true</code> if element is included in the
 *   filtered set, and <code>false</code> if excluded
 */
public abstract boolean select(Viewer viewer, Object parentElement, Object element);
}
