function setViewport() {

		// Embedded decks use the reveal element as their viewport
		if( config.embedded === true ) {
			dom.viewport = Util.closest( revealElement, '.reveal-viewport' ) || revealElement;
		}
		// Full-page decks use the body as their viewport
		else {
			dom.viewport = document.body;
			document.documentElement.classList.add( 'reveal-full-page' );
		}

		dom.viewport.classList.add( 'reveal-viewport' );

	}
Encase the presentation in a reveal.js viewport. The
extent of the viewport differs based on configuration.