MDL-53572 mathjax: always load mathjax using https

It's considered an anti-pattern now to use protocol relative urls and
reduces a setting.

(Also fixed an incorrectly placed 3.1.0 upgrade marker)

filter/mathjaxloader/db/upgrade.php

@@ -111,9 +111,6 @@ function xmldb_filter_mathjaxloader_upgrade($oldversion) {
     // Moodle v3.0.0 release upgrade line.
     // Put any upgrade step following this.
 
-    // Moodle v3.1.0 release upgrade line.
-    // Put any upgrade step following this.
-
     if ($oldversion < 2016032200) {
 
         $httpurl = get_config('filter_mathjaxloader', 'httpurl');
@@ -131,5 +128,25 @@ function xmldb_filter_mathjaxloader_upgrade($oldversion) {
         upgrade_plugin_savepoint(true, 2016032200, 'filter', 'mathjaxloader');
     }
 
+    // Moodle v3.1.0 release upgrade line.
+    // Put any upgrade step following this.
+
+    if ($oldversion < 2016080200) {
+        // We are consolodating the two settings for http and https url into only the https
+        // setting. Since it is preferably to always load the secure resource.
+
+        $httpurl = get_config('filter_mathjaxloader', 'httpurl');
+        if ($httpurl !== 'http://cdn.mathjax.org/mathjax/2.6-latest/MathJax.js') {
+            // If the http setting has been changed, we make the admin choose the https setting because
+            // it indicates some sort of custom setup. This will be supported by the release notes.
+            unset_config('httpsurl', 'filter_mathjaxloader');
+        }
+
+        // The seperate http setting has been removed. We always use the secure resource.
+        unset_config('httpurl', 'filter_mathjaxloader');
+
+        upgrade_plugin_savepoint(true, 2016080200, 'filter', 'mathjaxloader');
+    }
+
     return true;
 }

filter/mathjaxloader/filter.php

@@ -99,11 +99,7 @@ public function setup($page, $context) {
         static $jsinitialised = false;
 
         if (empty($jsinitialised)) {
-            if (is_https()) {
-                $url = get_config('filter_mathjaxloader', 'httpsurl');
-            } else {
-                $url = get_config('filter_mathjaxloader', 'httpurl');
-            }
+            $url = get_config('filter_mathjaxloader', 'httpsurl');
             $lang = $this->map_language_code(current_language());
             $url = new moodle_url($url, array('delayStartupUntil' => 'configured'));
 

filter/mathjaxloader/lang/en/filter_mathjaxloader.php

@@ -27,10 +27,8 @@
 $string['additionaldelimiters_help'] = 'MathJax filter parses text for equations contained within delimiter characters.
 
 The list of recognised delimiter characters can be added to here (e.g. AsciiMath uses `). Delimiters can contain multiple characters and multiple delimiters can be separated with commas.';
-$string['httpurl'] = 'HTTP MathJax URL';
-$string['httpurl_help'] = 'Full URL to MathJax library. Used when the page is loaded via http.';
-$string['httpsurl'] = 'HTTPS MathJax URL';
-$string['httpsurl_help'] = 'Full URL to MathJax library. Used when the page is loaded via https (secure). ';
+$string['httpsurl'] = 'MathJax URL';
+$string['httpsurl_help'] = 'Full URL to MathJax library.';
 $string['texfiltercompatibility'] = 'TeX filter compatibility';
 $string['texfiltercompatibility_help'] = 'The MathJax filter can be used as a replacement for the TeX notation filter.
 

filter/mathjaxloader/settings.php

@@ -30,13 +30,6 @@
                                       new lang_string('localinstall_help', 'filter_mathjaxloader'));
     $settings->add($item);
 
-    $item = new admin_setting_configtext('filter_mathjaxloader/httpurl',
-                                         new lang_string('httpurl', 'filter_mathjaxloader'),
-                                         new lang_string('httpurl_help', 'filter_mathjaxloader'),
-                                         'http://cdn.mathjax.org/mathjax/2.6-latest/MathJax.js',
-                                         PARAM_RAW);
-    $settings->add($item);
-
     $item = new admin_setting_configtext('filter_mathjaxloader/httpsurl',
                                          new lang_string('httpsurl', 'filter_mathjaxloader'),
                                          new lang_string('httpsurl_help', 'filter_mathjaxloader'),

filter/mathjaxloader/version.php

@@ -24,6 +24,6 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$plugin->version  = 2016052300;
+$plugin->version  = 2016080200;
 $plugin->requires = 2016051900;  // Requires this Moodle version.
 $plugin->component= 'filter_mathjaxloader';