/*******************************************************************************
 * Copyright (c) 2004 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.jface.resource;

import org.eclipse.swt.events.DisposeEvent;
import org.eclipse.swt.events.DisposeListener;
import org.eclipse.swt.graphics.Device;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.widgets.Control;


/**
 * A local registry that shares its resources with some global registry.
 * NestedSWTRegistry is typically used to safeguard against leaks. Clients
 * can use a nested registry to allocate and deallocate resources in the
 * global registry. Calling dispose() on the nested registry will deallocate
 * everything allocated for the nested registry without affecting the rest
 * of the global registry.
 * <p>
 * A nested registry can be used to manage the resources for, say, a dialog
 * box.
 * </p>
 * 
 * @since 3.1
 */
public final class LocalResourceManager extends AbstractResourceManager {

    private ResourceManager parentRegistry;
    
    /**
     * Creates a local registry that delegates to the given global registry
     * for all resource allocation and deallocation. 
     * 
     * @param parentRegistry global registry 
     */
    public LocalResourceManager(ResourceManager parentRegistry) {
        this.parentRegistry = parentRegistry;
    }
    
    /**
     * Creates a local registry that wraps the given global registry. Anything
     * allocated by this registry will be automatically cleaned up with the given
     * control is disposed. Note that registries created in this way should not
     * be used to allocate any resource that must outlive the given control.
     * 
     * @param parentRegistry global registry that handles resource allocation
     * @param owner control whose disposal will trigger cleanup of everything 
     * in the registry.
     */
    public LocalResourceManager(ResourceManager parentRegistry, Control owner) {
        this(parentRegistry);
        
        owner.addDisposeListener(new DisposeListener() {
	        /* (non-Javadoc)
	         * @see org.eclipse.swt.events.DisposeListener#widgetDisposed(org.eclipse.swt.events.DisposeEvent)
	         */
	        public void widgetDisposed(DisposeEvent e) {
	            LocalResourceManager.this.dispose();
	        } 
        });
    }
    
    /* (non-Javadoc)
     * @see org.eclipse.jface.resource.ResourceManager#getDevice()
     */
    public Device getDevice() {
        return parentRegistry.getDevice();
    }
    
    /* (non-Javadoc)
     * @see org.eclipse.jface.resource.AbstractSwtRegistry#allocate(org.eclipse.jface.resource.SwtResourceDescriptor)
     */
    protected Object allocate(DeviceResourceDescriptor descriptor)
            throws DeviceResourceException {
        return parentRegistry.create(descriptor);
    }
    
    /* (non-Javadoc)
     * @see org.eclipse.jface.resource.AbstractSwtRegistry#deallocate(java.lang.Object, org.eclipse.jface.resource.SwtResourceDescriptor)
     */
    protected void deallocate(Object resource,
            DeviceResourceDescriptor descriptor) {
        
        parentRegistry.destroy(descriptor);
    }

    /* (non-Javadoc)
     * @see org.eclipse.jface.resource.ResourceManager#getDefaultImage()
     */
    protected Image getDefaultImage() {
        return parentRegistry.getDefaultImage();
    }
}