Update slide rendering to reduce DOM wrap and avoid duplicate rendering slides

Author: jackycute

public/js/reveal-markdown.js

@@ -355,7 +355,7 @@
                 var rendered = md.render(markdown);
 				rendered = preventXSS(rendered);
 				var result = postProcess(rendered);
-				section.innerHTML = result[0].outerHTML;
+				section.innerHTML = result[0].innerHTML;
 				addAttributes( 	section, section, null, section.getAttribute( 'data-element-attributes' ) ||
 								section.parentNode.getAttribute( 'data-element-attributes' ) ||
 								DEFAULT_ELEMENT_ATTRIBUTES_SEPARATOR,

public/js/slide.js

@@ -55,10 +55,14 @@ viewAjaxCallback = function () {
 };
 
 function renderSlide(event) {
-    var title = document.title;
-    finishView($(event.currentSlide));
-    document.title = title;
-    Reveal.layout();
+    var markdown = $(event.currentSlide);
+    if (!markdown.attr('data-rendered')) {
+        var title = document.title;
+        finishView(markdown);
+        markdown.attr('data-rendered', 'true');
+        document.title = title;
+        Reveal.layout();
+    }
 }
 
 Reveal.addEventListener('ready', renderSlide);