bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/ReusableViewerLabel.java

/***************************************************************************************************
 * Copyright (c) 2006 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.ui.internal.navigator;

import org.eclipse.jface.viewers.ViewerLabel;

/**
 * Provides a subclass of ViewerLabel that can be re-used for multiple viewer updates.
 * 
 * @since 3.2
 * 
 */
public class ReusableViewerLabel extends ViewerLabel {

	private ViewerLabel original = null;
	/**
	 * Creates a ViewerLabel with null text and image.
	 *
	 */
	public ReusableViewerLabel() {
		super(null, null);
	}


	/**
	 * Updates the Background, Foreground, and Font to the given ViewerLabel. The 
	 * Text and Image are reset to <b>null</b>.
	 * 
	 * @param theOriginal The ViewerLabel to represent.
	 */
	public void reset(ViewerLabel theOriginal) {
		original = theOriginal;
		setBackground(original.getBackground());
		setFont(original.getFont());
		setForeground(original.getForeground());
		setImage(null);
		setText(null);
	}
	
	/**
	 * 
	 * @param theOriginal The ViewerLabel to fill with my values. 
	 */
	public void fill(ViewerLabel theOriginal) {

		theOriginal.setBackground(getBackground());
		theOriginal.setFont(getFont());
		theOriginal.setForeground(getForeground());
		theOriginal.setImage(getImage());
		theOriginal.setText(getText() != null ? getText() : ""); //$NON-NLS-1$
	}

	/** 
	 * 
	 * @return True if the ReusableViewerLabel has different text or image than the original
	 *         ViewerLabel.
	 */
	public boolean hasChanged() {
		
		boolean changed = false;
		if(original != null) {
			if(original.getText() == null ^ getText() != null)
				changed |= getText() != null;
			if(original.getText() != null && getImage() != null)
				changed |= !getImage().equals(original.getImage());
		}
		return changed;
	}

	/**
	 * @return True if the text is non-null and non-zero in length.
	 */
	public boolean isValid() {
		return getText() != null && getText().length() > 0 && getImage() != null;

	}

}