/*******************************************************************************
 * Copyright (c) 2000, 2005 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;

import org.eclipse.swt.internal.*;

/**
 * This error is thrown whenever an unrecoverable error
 * occurs internally in SWT. The message text and error code 
 * provide a further description of the problem. The exception
 * has a <code>throwable</code> field which holds the underlying
 * throwable that caused the problem (if this information is
 * available (i.e. it may be null)).
 * <p>
 * SWTErrors are thrown when something fails internally which
 * either leaves SWT in an unknown state (eg. the o/s call to
 * remove an item from a list returns an error code) or when SWT
 * is left in a known-to-be-unrecoverable state (eg. it runs out
 * of callback resources). SWTErrors should not occur in typical
 * programs, although "high reliability" applications should
 * still catch them.
 * </p><p>
 * This class also provides support methods used by SWT to match
 * error codes to the appropriate exception class (SWTError, 
 * SWTException, or IllegalArgumentException) and to provide
 * human readable strings for SWT error codes.
 * </p>
 *
 * @see SWTException
 * @see SWT#error(int)
 */

public class SWTError extends Error {
    /**
     * The SWT error code, one of SWT.ERROR_*.
     */
	public int code;

	/**
	 * The underlying throwable that caused the problem,
	 * or null if this information is not available.
	 */
	public Throwable throwable;

    static final long serialVersionUID = 3833467327105808433L;
    
/**
 * Constructs a new instance of this class with its 
 * stack trace filled in. The error code is set to an
 * unspecified value.
 */
public SWTError () {
	this (SWT.ERROR_UNSPECIFIED);
}

/**
 * Constructs a new instance of this class with its 
 * stack trace and message filled in. The error code is
 * set to an unspecified value.  Specifying <code>null</code>
 * as the message is equivalent to specifying an empty string.
 *
 * @param message the detail message for the exception
 */
public SWTError (String message) {
	this (SWT.ERROR_UNSPECIFIED, message);
}

/**
 * Constructs a new instance of this class with its 
 * stack trace and error code filled in.
 *
 * @param code the SWT error code
 */
public SWTError (int code) {
	this (code, SWT.findErrorText (code));
}

/**
 * Constructs a new instance of this class with its 
 * stack trace, error code and message filled in.
 * Specifying <code>null</code> as the message is
 * equivalent to specifying an empty string.
 * 
 * @param code the SWT error code
 * @param message the detail message for the exception
 */
public SWTError (int code, String message) {
	super (message);
	this.code = code;
}

/**
 * Returns the underlying throwable that caused the problem,
 * or null if this information is not available.
 * <p>
 * NOTE: This method overrides Throwable.getCause() that was
 * added to JDK1.4. It is necessary to override this method
 * in order for inherited printStackTrace() methods to work.
 * </p>
 * @return the underlying throwable
 * 
 * @since 3.1
 */
public Throwable getCause() {
	return throwable;
}

/**
 *  Returns the string describing this SWTError object.
 *  <p>
 *  It is combined with the message string of the Throwable
 *  which caused this SWTError (if this information is available).
 *  </p>
 *  @return the error message string of this SWTError object
 */
public String getMessage () {
	if (throwable == null) return super.getMessage ();
	return super.getMessage () + " (" + throwable.toString () + ")"; //$NON-NLS-1$ //$NON-NLS-2$
}

/**
 * Outputs a printable representation of this error's
 * stack trace on the standard error stream.
 * <p>
 * Note: printStackTrace(PrintStream) and printStackTrace(PrintWriter)
 * are not provided in order to maintain compatibility with CLDC.
 * </p>
 */
public void printStackTrace () {
	super.printStackTrace ();
	if (Library.JAVA_VERSION < Library.JAVA_VERSION(1, 4, 0) && throwable != null) {
		System.err.println ("*** Stack trace of contained error ***"); //$NON-NLS-1$
		throwable.printStackTrace ();
	}
}

}
