org.eclipse.swt.graphics.Resource Maven / Gradle / Ivy
/*******************************************************************************
* Copyright (c) 2002, 2011 Innoopract Informationssysteme GmbH.
* 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:
* Innoopract Informationssysteme GmbH - initial API and implementation
* EclipseSource - ongoing development
******************************************************************************/
package org.eclipse.swt.graphics;
import org.eclipse.swt.SWT;
import org.eclipse.swt.internal.SerializableCompatibility;
import org.eclipse.swt.widgets.Display;
/**
* This class is the abstract superclass of all graphics resource objects.
* Resources created by the application are shared across all sessions of the
* application.
*
*
* IMPORTANT: This class is intended to be subclassed only
* within the RWT implementation. However, it has not been marked
* final to allow those outside of the RWT 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.
*
*
* @since 1.0
*/
public abstract class Resource implements SerializableCompatibility {
final Device device;
private boolean disposed;
Resource( Device device ) {
this.device = device;
}
/**
* Returns the Device where this resource was
* created.
*
* @return Device the device of the receiver
*
* @since 1.3
*/
public Device getDevice() {
if( disposed ) {
SWT.error( SWT.ERROR_GRAPHIC_DISPOSED );
}
Device result = device;
// Currently, factory-managed resources (device == null) return the current
// display. This is done under the assumption that resource methods are
// only called from the UI thread. This way also shared resources appear to
// belong to the current session.
// Note that this is still under investigation.
if( result == null ) {
result = Display.getCurrent();
}
return result;
}
/**
* Disposes of the resource. Applications must dispose of all resources
* which they allocate.
* This method does nothing if the resource is already disposed.
*
* @since 1.3
*/
public void dispose() {
if( device == null ) {
throw new IllegalStateException( "A factory-created resource cannot be disposed." );
}
destroy();
disposed = true;
}
void destroy() {
}
/**
* 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
*
* @since 1.3
*/
public boolean isDisposed() {
return disposed;
}
static Device checkDevice( Device device ) {
Device result = device;
if( result == null ) {
result = Display.getCurrent();
}
if( result == null ) {
SWT.error( SWT.ERROR_NULL_ARGUMENT );
}
return result;
}
}