enable mathjax in live preview

lib/gollum/app.rb

@@ -148,7 +148,7 @@ module Precious
       @allow_uploads = wiki.allow_uploads
       if page = wikip.page
         if wiki.live_preview && page.format.to_s.include?('markdown') && supported_useragent?(request.user_agent)
-          live_preview_url = '/livepreview/index.html?page=' + encodeURIComponent(@name)
+          live_preview_url = '/livepreview/?page=' + encodeURIComponent(@name)
           if @path
             live_preview_url << '&path=' + encodeURIComponent(@path)
           end
@@ -362,6 +362,12 @@ module Precious
       mustache :page
     end
 
+    get '/livepreview/' do
+      wiki = wiki_new
+      @mathjax = wiki.mathjax
+      mustache :livepreview, { :layout => false }
+    end
+
     get '/history/*' do
       @page     = wiki_page(params[:splat].first).page
       @page_num = [params[:page].to_i, 1].max

lib/gollum/public/gollum/livepreview/js/livepreview.js

@@ -311,6 +311,10 @@ var makePreviewHtml = function () {
   // preview.innerHTML = text; // this doesn't work on IE.
   previewSet( text );
 
+  if (win.MathJax) {
+    win.MathJax.Hub.Queue(['Typeset', win.MathJax.Hub, 'contentframe']);
+  }
+
   // highlight code blocks.
   var codeElements = preview.getElementsByTagName( 'pre' );
   var codeElementsLength = codeElements.length;

lib/gollum/templates/livepreview.mustache

@@ -40,5 +40,27 @@ var require = {
 <script src='js/sundown.js'></script>
 <script src='js/md_sundown.js'></script>
 <script src='js/livepreview.js'></script>
+{{#mathjax}}
+{{^mathjax_config}}
+<script type="text/javascript">
+window.MathJax = {
+tex2jax: {
+  inlineMath:  [ ['\\(','\\)'] ],
+  displayMath: [ ['$$','$$'], ['\\[','\\]'] ],
+  processEscapes: true
+},
+TeX: { extensions: ["autoload-all.js"] }
+};
+</script>
+{{/mathjax_config}}
+{{#mathjax_config}}
+<script type="text/javascript" src="{{base_url}}/{{mathjax_config}}"></script>
+{{/mathjax_config}}
+<script>(function(d,j){
+j = d.createElement('script');
+j.src = '//cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML';
+(d.head || d.getElementsByTagName('head')[0]).appendChild(j);
+}(document));
+</script>{{/mathjax}}
 </body>
 </html>

lib/gollum/views/livepreview.rb

@@ -0,0 +1,13 @@
+module Precious
+  module Views
+    class Livepreview < Layout
+      def mathjax
+        @mathjax
+      end
+
+      def mathjax_config
+        @mathjax_config
+      end
+    end
+  end
+end