use skipStartupTypeset: true for MathJax config, and call MathJax.Hub.Typeset() later

setTimeout() is necessary for uiOutput(); we need to wait for a short while before typesetting math, otherwise two bad things can happen:

1. a math expression may be rendered twice (static output)
2. it is not rendered at all (dynamic ui output)

so the compromise is to typeset math after a short while when the document is ready; 200 ms is an arbitrary choice here

R/shinyui.R

@@ -153,9 +153,14 @@ includeScript <- function(path, ...) {
 withMathJax <- function(...) {
   path <- 'https://c328740.ssl.cf1.rackcdn.com/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML'
   tagList(
-    tags$head(singleton(tags$script(src = path, type = 'text/javascript'))),
+    tags$head(
+      singleton(tags$script(HTML('window.MathJax = {skipStartupTypeset: true};'))),
+      singleton(tags$script(src = path, type = 'text/javascript'))
+    ),
     ...,
-    tags$script(HTML('MathJax.Hub.Typeset();'))
+    tags$script(HTML('$(function() {
+                        setTimeout(function() {MathJax.Hub.Typeset();}, 200);
+                      });'))
   )
 }