core/plugins/org.eclipse.dltk.ui/src/org/eclipse/dltk/ui/viewsupport/ImagesOnFileSystemRegistry.java

/*******************************************************************************
 * Copyright (c) 2008, 2017 IBM Corporation and others.
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 * 
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.dltk.ui.viewsupport;

import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.HashMap;

import org.eclipse.dltk.ui.DLTKUIPlugin;
import org.eclipse.jface.resource.ImageDescriptor;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.ImageData;
import org.eclipse.swt.graphics.ImageLoader;

/**
 * Image registry that keeps its images on the local file system.
 *
 * @since 4.0
 */
public class ImagesOnFileSystemRegistry {

	private static final String IMAGE_DIR = "dltk-images"; //$NON-NLS-1$

	private HashMap<ImageDescriptor, URL> fURLMap;
	private final File fTempDir;
	private int fImageCount;

	public ImagesOnFileSystemRegistry() {
		fURLMap = new HashMap<>();
		fTempDir = getTempDir();
		fImageCount = 0;
	}

	private File getTempDir() {
		try {
			File imageDir = DLTKUIPlugin.getDefault().getStateLocation()
					.append(IMAGE_DIR).toFile();
			if (imageDir.exists()) {
				// has not been deleted on previous shutdown
				delete(imageDir);
			}
			if (!imageDir.exists()) {
				imageDir.mkdir();
			}
			if (!imageDir.isDirectory()) {
				DLTKUIPlugin.logErrorMessage("Failed to create image directory " //$NON-NLS-1$
						+ imageDir.toString());
				return null;
			}
			return imageDir;
		} catch (IllegalStateException e) {
			// no state location
			return null;
		}
	}

	private void delete(File file) {
		if (file.isDirectory()) {
			File[] listFiles = file.listFiles();
			for (int i = 0; i < listFiles.length; i++) {
				delete(listFiles[i]);
			}
		}
		file.delete();
	}

	public URL getImageURL(ImageDescriptor descriptor) {
		if (fTempDir == null)
			return null;

		URL url = fURLMap.get(descriptor);
		if (url != null)
			return url;

		File imageFile = getNewFile();
		ImageData imageData = descriptor.getImageData();
		if (imageData == null) {
			return null;
		}

		ImageLoader loader = new ImageLoader();
		loader.data = new ImageData[] { imageData };
		loader.save(imageFile.getAbsolutePath(), SWT.IMAGE_PNG);

		try {
			url = imageFile.toURI().toURL();
			fURLMap.put(descriptor, url);
			return url;
		} catch (MalformedURLException e) {
			DLTKUIPlugin.log(e);
		}
		return null;
	}

	private File getNewFile() {
		File file;
		do {
			file = new File(fTempDir, String.valueOf(getImageCount()) + ".png"); //$NON-NLS-1$
		} while (file.exists());
		return file;
	}

	private synchronized int getImageCount() {
		return fImageCount++;
	}

	public void dispose() {
		if (fTempDir != null) {
			delete(fTempDir);
		}
		fURLMap = null;
	}
}