org.eclipse.swt.graphics.Resource Maven / Gradle / Ivy

/*******************************************************************************
 * Copyright (c) 2000, 2010 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.swt.graphics;

import org.eclipse.swt.*;

/**
 * This class is the abstract superclass of all graphics resource objects.
 * Resources created by the application must be disposed.
 * 
 * IMPORTANT: This class is intended to be subclassed only
 * within the SWT implementation. However, it has not been marked
 * final to allow those outside of the SWT development team to implement
 * patched versions of the class in order to get around specific
 * limitations in advance of when those limitations can be addressed
 * by the team.  Any class built using subclassing to access the internals
 * of this class will likely fail to compile or run between releases and
 * may be strongly platform specific. Subclassing should not be attempted
 * without an intimate and detailed understanding of the workings of the
 * hierarchy. No support is provided for user-written classes which are
 * implemented as subclasses of this class.
 * 
 *
 * @see #dispose
 * @see #isDisposed
 * @see Sample code and further information
 *
 * @since 3.1
 */
public abstract class Resource {

	/**
	 * the device where this resource was created
	 */
	Device device;

public Resource() {
}

Resource(Device device) {
	if (device == null) device = Device.getDevice();
	if (device == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
	this.device = device;
}

void destroy() {
}

/**
 * Disposes of the operating system resources associated with
 * this resource. Applications must dispose of all resources
 * which they allocate.
 * This method does nothing if the resource is already disposed.
 */
public void dispose() {
	if (device == null) return;
	if (device.isDisposed()) return;
	destroy();
	if (device.tracking) device.dispose_Object(this);
	device = null;
}

/**
 * Returns the Device where this resource was
 * created.
 *
 * @return Device the device of the receiver
 *
 * @since 3.2
 */
public Device getDevice() {
	Device device = this.device;
	if (device == null || isDisposed ()) SWT.error (SWT.ERROR_GRAPHIC_DISPOSED);
	return device;
}

void init() {
	if (device.tracking) device.new_Object(this);
}

/**
 * Returns true if the resource has been disposed,
 * and false otherwise.
 * 
 * This method gets the dispose state for the resource.
 * When a resource has been disposed, it is an error to
 * invoke any other method (except {@link #dispose()}) using the resource.
 *
 * @return true when the resource is disposed and false otherwise
 */
public abstract boolean isDisposed();

}