improve rendering accuracy of overview

css/reveal.css

@@ -1055,6 +1055,11 @@ body {
  *********************************************/
 
 .reveal.overview .slides {
+	-webkit-perspective-origin: 0% 0%;
+	   -moz-perspective-origin: 0% 0%;
+	    -ms-perspective-origin: 0% 0%;
+	        perspective-origin: 0% 0%;
+
 	-webkit-perspective: 700px;
 	   -moz-perspective: 700px;
 	    -ms-perspective: 700px;

js/reveal.js

@@ -575,6 +575,11 @@ var Reveal = (function(){
 
 			dom.wrapper.classList.add( 'overview' );
 
+			// Not the pretties solution, but need to let the overview 
+			// class apply first so that slides are measured accurately 
+			// before we can positon them
+			setTimeout( function(){
+
 				var horizontalSlides = document.querySelectorAll( HORIZONTAL_SLIDES_SELECTOR );
 
 				for( var i = 0, len1 = horizontalSlides.length; i < len1; i++ ) {
@@ -623,6 +628,8 @@ var Reveal = (function(){
 
 				layout();
 
+			}, 10 );
+
 		}
 
 	}