support for data-markdown (#15)

index.html

@@ -259,9 +259,23 @@ function linkify( selector ) {
 		<script src="lib/js/head.min.js"></script>
 
 		<script>
-			// Load reveal.js as well as a classList polyfill if needed
-			head.js( !document.body.classList ? 'lib/js/classList.js' : null )
-				.js( 'js/reveal.js', function() {
+			// All scripts that should be loaded before initializing
+			var scripts = [];
+
+			// If the browser doesn't support classList, load a polyfill
+			if( !document.body.classList ) {
+				scripts.push( 'lib/js/classList.js' );
+			}
+
+			// Load markdown parser if there are slides defined using markdown
+			if( document.querySelector( '[data-markdown]' ) ) {
+				scripts.push( 'lib/js/showdown.js' );
+				scripts.push( 'lib/js/data-markdown.js' );
+			}
+
+			scripts.push( 'js/reveal.js' );
+
+			head.js.apply( null, scripts.concat([ function() {
 
 				// Parse the query string into a key/value object
 				var query = {};
@@ -290,7 +304,7 @@ function linkify( selector ) {
 					transition: query.transition || 'default' // default/cube/page/concave/linear(2d)
 				});
 
-			} );
+			}]));
 			
 			// Load highlight.js for syntax highlighting of code samples
 			head.js( 'lib/js/highlight.js', function() { 

js/reveal.js

@@ -1,5 +1,5 @@
 /*!
- * reveal.js 1.5 r3
+ * reveal.js 1.5 r4
  * http://lab.hakim.se/reveal-js
  * MIT licensed
  * 

lib/js/data-markdown.js

@@ -0,0 +1,19 @@
+// From https://gist.github.com/1343518, modified to not load showdown
+(function boom(){
+
+  [].forEach.call( document.querySelectorAll('[data-markdown]'), function  fn(elem){
+      
+    // strip leading whitespace so it isn't evaluated as code
+    var text      = elem.innerHTML.replace(/\n\s*\n/g,'\n'),
+        // set indentation level so your markdown can be indented within your HTML
+        leadingws = text.match(/^\n?(\s*)/)[1].length,
+        regex     = new RegExp('\\n?\\s{' + leadingws + '}','g'),
+        md        = text.replace(regex,'\n'),
+        html      = (new Showdown.converter()).makeHtml(md);
+
+    // here, have sum HTML
+    elem.innerHTML = html;
+
+  });
+
+}());