gifs now restart when their slide container is shown

js/reveal.js

@@ -2580,6 +2580,15 @@
 				currentVideo.play();
 			}
 
+			var backgroundImageURL = currentBackground.style.backgroundImage || '';
+
+			// Restart GIFs (doesn't work in Firefox)
+			if( /\.gif/i.test( backgroundImageURL ) ) {
+				currentBackground.style.backgroundImage = '';
+				window.getComputedStyle( currentBackground ).opacity;
+				currentBackground.style.backgroundImage = backgroundImageURL;
+			}
+
 			// Don't transition between identical backgrounds. This
 			// prevents unwanted flicker.
 			var previousBackgroundHash = previousBackground ? previousBackground.getAttribute( 'data-background-hash' ) : null;
@@ -2826,6 +2835,13 @@
 	function startEmbeddedContent( slide ) {
 
 		if( slide && !isSpeakerNotes() ) {
+			// Restart GIFs
+			toArray( slide.querySelectorAll( 'img[src$=".gif"]' ) ).forEach( function( el ) {
+				// Setting the same unchanged source like this was confirmed
+				// to work in Chrome, FF & Safari
+				el.setAttribute( 'src', el.getAttribute( 'src' ) );
+			} );
+
 			// HTML5 media elements
 			toArray( slide.querySelectorAll( 'video, audio' ) ).forEach( function( el ) {
 				if( el.hasAttribute( 'data-autoplay' ) ) {