org.eclipse.wst.xml.xpath.ui.internal.util.XPathPluginImageHelper.java Source code

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/*******************************************************************************
 * Copyright (c) 2008 Standards for Technology in Automotive Retail 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:
 *     David Carver - STAR - bug 213849 - initial API and implementation
 *     
 *******************************************************************************/
package org.eclipse.wst.xml.xpath.ui.internal.util;

import java.util.HashMap;

import org.eclipse.jface.resource.ImageDescriptor;
import org.eclipse.jface.resource.ImageRegistry;
import org.eclipse.jface.resource.JFaceResources;
import org.eclipse.swt.graphics.Image;
import org.eclipse.ui.plugin.AbstractUIPlugin;
import org.eclipse.wst.xml.xpath.ui.internal.XPathUIPlugin;

/**
 * Helper class to handle images provided by this plug-in.
 * 
 * NOTE: For internal use only. For images used externally, please use the
 * Shared***ImageHelper class instead.
 * 
 * @author david carver based on work by amywu
 */
public class XPathPluginImageHelper {
    private static XPathPluginImageHelper instance = null;

    /**
     * Gets the instance.
     * 
     * @return Returns a XMLEditorPluginImageHelper
     */
    public synchronized static XPathPluginImageHelper getInstance() {
        if (instance == null) {
            instance = new XPathPluginImageHelper();
        }
        return instance;
    }

    // save a descriptor for each image
    @SuppressWarnings("unchecked")
    private HashMap fImageDescRegistry = null;

    // private final String PLUGINID = XPathUIPlugin.PLUGIN_ID;

    /**
     * Creates an image from the given resource and adds the image to the image
     * registry.
     * 
     * @param resource
     * @return Image
     */
    private Image createImage(String resource) {
        ImageDescriptor desc = getImageDescriptor(resource);
        Image image = null;

        if (desc != null) {
            image = desc.createImage();
            // dont add the missing image descriptor image to the image
            // registry
            if (!desc.equals(ImageDescriptor.getMissingImageDescriptor())) {
                getImageRegistry().put(resource, image);
            }
        }
        return image;
    }

    /**
     * Creates an image descriptor from the given imageFilePath and adds the
     * image descriptor to the image descriptor registry. If an image descriptor
     * could not be created, the default "missing" image descriptor is returned
     * but not added to the image descriptor registry.
     * 
     * @param imageFilePath
     * @return ImageDescriptor image descriptor for imageFilePath or default
     *         "missing" image descriptor if resource could not be found
     */
    @SuppressWarnings("unchecked")
    private ImageDescriptor createImageDescriptor(String imageFilePath) {
        ImageDescriptor imageDescriptor = AbstractUIPlugin.imageDescriptorFromPlugin(XPathUIPlugin.PLUGIN_ID,
                imageFilePath);
        if (imageDescriptor != null) {
            getImageDescriptorRegistry().put(imageFilePath, imageDescriptor);
        } else {
            imageDescriptor = ImageDescriptor.getMissingImageDescriptor();
        }

        return imageDescriptor;
    }

    /**
     * Retrieves the image associated with resource from the image registry. If
     * the image cannot be retrieved, attempt to find and load the image at the
     * location specified in resource.
     * 
     * @param resource
     *            the image to retrieve
     * @return Image the image associated with resource or null if one could not
     *         be found
     */
    public Image getImage(String resource) {
        Image image = getImageRegistry().get(resource);
        if (image == null) {
            // create an image
            image = createImage(resource);
        }
        return image;
    }

    /**
     * Retrieves the image descriptor associated with resource from the image
     * descriptor registry. If the image descriptor cannot be retrieved, attempt
     * to find and load the image descriptor at the location specified in
     * resource.
     * 
     * @param resource
     *            the image descriptor to retrieve
     * @return ImageDescriptor the image descriptor assocated with resource or
     *         the default "missing" image descriptor if one could not be found
     */
    public ImageDescriptor getImageDescriptor(String resource) {
        ImageDescriptor imageDescriptor = null;
        Object o = getImageDescriptorRegistry().get(resource);
        if (o == null) {
            // create a descriptor
            imageDescriptor = createImageDescriptor(resource);
        } else {
            imageDescriptor = (ImageDescriptor) o;
        }
        return imageDescriptor;
    }

    /**
     * Returns the image descriptor registry for this plugin.
     * 
     * @return HashMap - image descriptor registry for this plugin
     */
    @SuppressWarnings("unchecked")
    private HashMap getImageDescriptorRegistry() {
        if (fImageDescRegistry == null) {
            fImageDescRegistry = new HashMap();
        }
        return fImageDescRegistry;
    }

    /**
     * Returns the image registry for this plugin.
     * 
     * @return ImageRegistry - image registry for this plugin
     */
    private ImageRegistry getImageRegistry() {
        return JFaceResources.getImageRegistry();
    }
}