public Image getSystemImage(int id) {
		checkDevice();
		switch (id) {
		case SWT.ICON_ERROR:
			if (errorImage == null) {
				errorImage = createImage("gtk-dialog-error"); //$NON-NLS-1$
			}
			return errorImage;
		case SWT.ICON_INFORMATION:
		case SWT.ICON_WORKING:
			if (infoImage == null) {
				infoImage = createImage("gtk-dialog-info"); //$NON-NLS-1$
			}
			return infoImage;
		case SWT.ICON_QUESTION:
			if (questionImage == null) {
				questionImage = createImage("gtk-dialog-question"); //$NON-NLS-1$
			}
			return questionImage;
		case SWT.ICON_WARNING:
			if (warningImage == null) {
				warningImage = createImage("gtk-dialog-warning"); //$NON-NLS-1$
			}
			return warningImage;
		}
		return null;
	}