/*******************************************************************************
 * Copyright (c) 2000, 2005 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.erlide.ui.util;

import java.util.HashMap;

import org.eclipse.core.runtime.Assert;
import org.eclipse.jface.resource.ImageDescriptor;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.widgets.Display;

/**
 * A registry that maps <code>ImageDescriptors</code> to <code>Image</code>.
 */
public class ImageDescriptorRegistry {

	private final HashMap<ImageDescriptor, Image> fRegistry = new HashMap<ImageDescriptor, Image>(
			10);

	private final Display fDisplay;

	/**
	 * Creates a new image descriptor registry for the current or default
	 * display, respectively.
	 */
	public ImageDescriptorRegistry() {
		this(SWTUtil.getStandardDisplay());
	}

	/**
	 * Creates a new image descriptor registry for the given display. All images
	 * managed by this registry will be disposed when the display gets disposed.
	 * 
	 * @param display
	 *            the display the images managed by this registry are allocated
	 *            for
	 */
	public ImageDescriptorRegistry(final Display display) {
		fDisplay = display;
		Assert.isNotNull(fDisplay);
		hookDisplay();
	}

	/**
	 * Returns the image assiciated with the given image descriptor.
	 * 
	 * @param descriptor
	 *            the image descriptor for which the registry manages an image
	 * @return the image associated with the image descriptor or
	 *         <code>null</code> if the image descriptor can't create the
	 *         requested image.
	 */
	public Image get(ImageDescriptor descriptor) {
		if (descriptor == null) {
			descriptor = ImageDescriptor.getMissingImageDescriptor();
		}

		Image result = fRegistry.get(descriptor);
		if (result != null) {
			return result;
		}

		Assert.isTrue(fDisplay == SWTUtil.getStandardDisplay(),
				"Allocating image for wrong display."); //$NON-NLS-1$
		result = descriptor.createImage();
		if (result != null) {
			fRegistry.put(descriptor, result);
		}
		return result;
	}

	/**
	 * Disposes all images managed by this registry.
	 */
	public void dispose() {
		for (final Object element : fRegistry.values()) {
			final Image image = (Image) element;
			image.dispose();
		}
		fRegistry.clear();
	}

	private void hookDisplay() {
		fDisplay.disposeExec(new Runnable() {

			public void run() {
				dispose();
			}
		});
	}
}
