Allow textinputdynamath to specify its Mathjax preprocessor per-problem

common/lib/capa/capa/inputtypes.py

@@ -326,8 +326,16 @@ def textline_dynamath(element, value, status, render_template, msg=''):
     count = int(eid.split('_')[-2]) - 1  # HACK
     size = element.get('size')
     hidden = element.get('hidden', '')	 # if specified, then textline is hidden and id is stored in div of name given by hidden
+
+    # Preprocessor to insert between raw input and Mathjax
+    preprocessor = {'class_name': element.get('preprocessorClassName',''),
+                    'script_src': element.get('preprocessorSrc','')}
+    if '' in preprocessor.values():
+        preprocessor = None
+
     context = {'id': eid, 'value': value, 'state': status, 'count': count, 'size': size,
                'msg': msg, 'hidden': hidden,
+               'preprocessor': preprocessor,
                }
     html = render_template("textinput_dynamath.html", context)
     return etree.XML(html)

common/lib/capa/capa/templates/textinput_dynamath.html

@@ -3,8 +3,10 @@
 ###
 <section class="text-input-dynamath textinputdynamath capa_inputtype" id="inputtype_${id}">
 
-    <div class="textinputdynamath_data" data-preprocessor="MathjaxPreprocessorFor6002x"/>
-    <div class="script_placeholder" data-src="/static/js/mathjax_preprocessor_for_6002x.js"/>
+    % if preprocessor is not None:
+    <div class="textinputdynamath_data" data-preprocessor="${preprocessor['class_name']}"/>
+    <div class="script_placeholder" data-src="${preprocessor['script_src']}"/>
+    % endif
 
     % if state == 'unsubmitted':
     <div class="unanswered" id="status_${id}">

common/lib/xmodule/xmodule/js/src/capa/display.coffee

@@ -6,7 +6,6 @@ class @Problem
     @element_id = @el.attr('id')
     @url = @el.data('url')
     @render()
-    @mathjax_preprocessor = false
 
   $: (selector) ->
     $(selector, @el)
@@ -301,6 +300,7 @@ class @Problem
 
     target = "display_" + elid
 
+    # MathJax preprocessor is loaded by 'setupInputTypes'
     preprocessor_tag = "inputtype_" + elid
     mathjax_preprocessor = @inputtypeDisplays[preprocessor_tag]
 
@@ -308,7 +308,6 @@ class @Problem
       eqn = $(element).val()
       if mathjax_preprocessor
         eqn = mathjax_preprocessor(eqn)
-
       MathJax.Hub.Queue ['Text', jax, eqn],
         [@updateMathML, jax, element]
 
@@ -329,13 +328,19 @@ class @Problem
   inputtypeSetupMethods:
 
     textinputdynamath: (element) =>
+      ###
+      Return: function (eqn) -> eqn that preprocesses the user formula input before
+                it is fed into MathJax. Return 'false' if no preprocessor specified
+      ###
       data = $(element).find('.textinputdynamath_data')
 
       preprocessorClassName = data.data('preprocessor')
       preprocessorClass = window[preprocessorClassName]
-
-      preprocessor = new preprocessorClass()
-      return preprocessor.fn
+      if typeof(preprocessorClass) == 'undefined' 
+        return false
+      else
+        preprocessor = new preprocessorClass()
+        return preprocessor.fn
 
     javascriptinput: (element) =>