function layout()

in js/reveal.js [2203:2313]
73 lines of code
15 McCabe index (conditional complexity)

	function layout() {

		if( dom.wrapper && !isPrintingPDF() ) {

			if( !config.disableLayout ) {

				// On some mobile devices '100vh' is taller than the visible
				// viewport which leads to part of the presentation being
				// cut off. To work around this we define our own '--vh' custom
				// property where 100x adds up to the correct height.
				//
				// https://css-tricks.com/the-trick-to-viewport-units-on-mobile/
				if( isMobileDevice ) {
					document.documentElement.style.setProperty( '--vh', ( window.innerHeight * 0.01 ) + 'px' );
				}

				var size = getComputedSlideSize();

				var oldScale = scale;

				// Layout the contents of the slides
				layoutSlideContents( config.width, config.height );

				dom.slides.style.width = size.width + 'px';
				dom.slides.style.height = size.height + 'px';

				// Determine scale of content to fit within available space
				scale = Math.min( size.presentationWidth / size.width, size.presentationHeight / size.height );

				// Respect max/min scale settings
				scale = Math.max( scale, config.minScale );
				scale = Math.min( scale, config.maxScale );

				// Don't apply any scaling styles if scale is 1
				if( scale === 1 ) {
					dom.slides.style.zoom = '';
					dom.slides.style.left = '';
					dom.slides.style.top = '';
					dom.slides.style.bottom = '';
					dom.slides.style.right = '';
					transformSlides( { layout: '' } );
				}
				else {
					// Prefer zoom for scaling up so that content remains crisp.
					// Don't use zoom to scale down since that can lead to shifts
					// in text layout/line breaks.
					if( scale > 1 && features.zoom ) {
						dom.slides.style.zoom = scale;
						dom.slides.style.left = '';
						dom.slides.style.top = '';
						dom.slides.style.bottom = '';
						dom.slides.style.right = '';
						transformSlides( { layout: '' } );
					}
					// Apply scale transform as a fallback
					else {
						dom.slides.style.zoom = '';
						dom.slides.style.left = '50%';
						dom.slides.style.top = '50%';
						dom.slides.style.bottom = 'auto';
						dom.slides.style.right = 'auto';
						transformSlides( { layout: 'translate(-50%, -50%) scale('+ scale +')' } );
					}
				}

				// Select all slides, vertical and horizontal
				var slides = toArray( dom.wrapper.querySelectorAll( SLIDES_SELECTOR ) );

				for( var i = 0, len = slides.length; i < len; i++ ) {
					var slide = slides[ i ];

					// Don't bother updating invisible slides
					if( slide.style.display === 'none' ) {
						continue;
					}

					if( config.center || slide.classList.contains( 'center' ) ) {
						// Vertical stacks are not centred since their section
						// children will be
						if( slide.classList.contains( 'stack' ) ) {
							slide.style.top = 0;
						}
						else {
							slide.style.top = Math.max( ( size.height - slide.scrollHeight ) / 2, 0 ) + 'px';
						}
					}
					else {
						slide.style.top = '';
					}

				}

				if( oldScale !== scale ) {
					dispatchEvent( 'resize', {
						'oldScale': oldScale,
						'scale': scale,
						'size': size
					} );
				}
			}

			updateProgress();
			updateParallax();

			if( isOverview() ) {
				updateOverview();
			}

		}

	}