filter/mathjaxloader/filter.php

   1 <?php
   2 // This file is part of Moodle - http://moodle.org/
   3 //
   4 // Moodle is free software: you can redistribute it and/or modify
   5 // it under the terms of the GNU General Public License as published by
   6 // the Free Software Foundation, either version 3 of the License, or
   7 // (at your option) any later version.
   8 //
   9 // Moodle is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13 //
  14 // You should have received a copy of the GNU General Public License
  15 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 /**
  18  * This filter provides automatic support for MathJax
  19  *
  20  * @package    filter_mathjaxloader
  21  * @copyright  2013 Damyon Wiese (damyon@moodle.com)
  22  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  23  */
  24
  25 defined('MOODLE_INTERNAL') || die();
  26
  27 /**
  28  * Mathjax filtering
  29  */
  30 class filter_mathjaxloader extends moodle_text_filter {
  31
  32     /*
  33      * Perform a mapping of the moodle language code to the equivalent for MathJax.
  34      *
  35      * @param string $moodlelangcode - The moodle language code - e.g. en_pirate
  36      * @return string The MathJax language code.
  37      */
  38     public function map_language_code($moodlelangcode) {
  39
  40         // List of language codes found in the MathJax/localization/ directory.
  41         $mathjaxlangcodes = [
  42             'ar', 'ast', 'bcc', 'bg', 'br', 'ca', 'cdo', 'ce', 'cs', 'cy', 'da', 'de', 'diq', 'en', 'eo', 'es', 'fa',
  43             'fi', 'fr', 'gl', 'he', 'ia', 'it', 'ja', 'kn', 'ko', 'lb', 'lki', 'lt', 'mk', 'nl', 'oc', 'pl', 'pt',
  44             'pt-br', 'qqq', 'ru', 'scn', 'sco', 'sk', 'sl', 'sv', 'th', 'tr', 'uk', 'vi', 'zh-hans', 'zh-hant'
  45         ];
  46
  47         // List of explicit mappings and known exceptions (moodle => mathjax).
  48         $explicit = [
  49             'cz' => 'cs',
  50             'pt_br' => 'pt-br',
  51             'zh_tw' => 'zh-hant',
  52             'zh_cn' => 'zh-hans',
  53         ];
  54
  55         // If defined, explicit mapping takes the highest precedence.
  56         if (isset($explicit[$moodlelangcode])) {
  57             return $explicit[$moodlelangcode];
  58         }
  59
  60         // If there is exact match, it will be probably right.
  61         if (in_array($moodlelangcode, $mathjaxlangcodes)) {
  62             return $moodlelangcode;
  63         }
  64
  65         // Finally try to find the best matching mathjax pack.
  66         $parts = explode('_', $moodlelangcode, 2);
  67         if (in_array($parts[0], $mathjaxlangcodes)) {
  68             return $parts[0];
  69         }
  70
  71         // No more guessing, use English.
  72         return 'en';
  73     }
  74
  75     /*
  76      * Add the javascript to enable mathjax processing on this page.
  77      *
  78      * @param moodle_page $page The current page.
  79      * @param context $context The current context.
  80      */
  81     public function setup($page, $context) {
  82
  83         if ($page->requires->should_create_one_time_item_now('filter_mathjaxloader-scripts')) {
  84             $url = get_config('filter_mathjaxloader', 'httpsurl');
  85             $lang = $this->map_language_code(current_language());
  86             $url = new moodle_url($url, array('delayStartupUntil' => 'configured'));
  87
  88             $moduleconfig = array(
  89                 'name' => 'mathjax',
  90                 'fullpath' => $url
  91             );
  92
  93             $page->requires->js_module($moduleconfig);
  94
  95             $config = get_config('filter_mathjaxloader', 'mathjaxconfig');
  96             $wwwroot = new moodle_url('/');
  97
  98             $config = str_replace('{wwwroot}', $wwwroot->out(true), $config);
  99
 100             $params = array('mathjaxconfig' => $config, 'lang' => $lang);
 101
 102             $page->requires->yui_module('moodle-filter_mathjaxloader-loader', 'M.filter_mathjaxloader.configure', array($params));
 103         }
 104     }
 105
 106     /*
 107      * This function wraps the filtered text in a span, that mathjaxloader is configured to process.
 108      *
 109      * @param string $text The text to filter.
 110      * @param array $options The filter options.
 111      */
 112     public function filter($text, array $options = array()) {
 113         global $PAGE;
 114
 115         $legacy = get_config('filter_mathjaxloader', 'texfiltercompatibility');
 116         $extradelimiters = explode(',', get_config('filter_mathjaxloader', 'additionaldelimiters'));
 117         if ($legacy) {
 118             // This replaces any of the tex filter maths delimiters with the default for inline maths in MathJAX "\( blah \)".
 119             // E.g. "<tex.*> blah </tex>".
 120             $text = preg_replace('|<(/?) *tex( [^>]*)?>|u', '[\1tex]', $text);
 121             // E.g. "[tex.*] blah [/tex]".
 122             $text = str_replace('[tex]', '\\(', $text);
 123             $text = str_replace('[/tex]', '\\)', $text);
 124             // E.g. "$$ blah $$".
 125             $text = preg_replace('|\$\$([\S\s]*?)\$\$|u', '\\(\1\\)', $text);
 126             // E.g. "\[ blah \]".
 127             $text = str_replace('\\[', '\\(', $text);
 128             $text = str_replace('\\]', '\\)', $text);
 129         }
 130
 131         $hasextra = false;
 132         foreach ($extradelimiters as $extra) {
 133             if ($extra && strpos($text, $extra) !== false) {
 134                 $hasextra = true;
 135                 break;
 136             }
 137         }
 138
 139         $hasdisplayorinline = false;
 140         if ($hasextra) {
 141             // If custom dilimeters are used, wrap whole text to prevent autolinking.
 142             $text = '<span class="nolink">' . $text . '</span>';
 143         } else if (preg_match('/\\\\[[(]/', $text) || preg_match('/\$\$/', $text)) {
 144             // Only parse the text if there are mathjax symbols in it. The recognized
 145             // math environments are \[ \] and $$ $$ for display mathematics and \( \)
 146             // for inline mathematics.
 147             // Note: 2 separate regexes seems to perform better here than using a single
 148             // regex with groupings.
 149
 150             // Wrap display and inline math environments in nolink spans.
 151             // Do not wrap nested environments, i.e., if inline math is nested
 152             // inside display math, only the outer display math is wrapped in
 153             // a span. The span HTML inside a LaTex math environment would break
 154             // MathJax. See MDL-61981.
 155             list($text, $hasdisplayorinline) = $this->wrap_math_in_nolink($text);
 156         }
 157
 158         if ($hasdisplayorinline || $hasextra) {
 159             $PAGE->requires->yui_module('moodle-filter_mathjaxloader-loader', 'M.filter_mathjaxloader.typeset');
 160             return '<span class="filter_mathjaxloader_equation">' . $text . '</span>';
 161         }
 162         return $text;
 163     }
 164
 165     /**
 166      * Find math environments in the $text and wrap them in no link spans
 167      * (<span class="nolink"></span>). If math environments are nested, only
 168      * the outer environment is wrapped in the span.
 169      *
 170      * The recognized math environments are \[ \] and $$ $$ for display
 171      * mathematics and \( \) for inline mathematics.
 172      *
 173      * @param string $text The text to filter.
 174      * @return array An array containing the potentially modified text and
 175      * a boolean that is true if any changes were made to the text.
 176      */
 177     protected function wrap_math_in_nolink($text) {
 178         $i = 1;
 179         $len = strlen($text);
 180         $displaystart = -1;
 181         $displaybracket = false;
 182         $displaydollar = false;
 183         $inlinestart = -1;
 184         $changesdone = false;
 185         // Loop over the $text once.
 186         while ($i < $len) {
 187             if ($displaystart === -1) {
 188                 // No display math has started yet.
 189                 if ($text[$i - 1] === '\\' && $text[$i] === '[') {
 190                     // Display mode \[ begins.
 191                     $displaystart = $i - 1;
 192                     $displaybracket = true;
 193                 } else if ($text[$i - 1] === '$' && $text[$i] === '$') {
 194                     // Display mode $$ begins.
 195                     $displaystart = $i - 1;
 196                     $displaydollar = true;
 197                 } else if ($text[$i - 1] === '\\' && $text[$i] === '(') {
 198                     // Inline math \( begins, not nested inside display math.
 199                     $inlinestart = $i - 1;
 200                 } else if ($text[$i - 1] === '\\' && $text[$i] === ')' && $inlinestart > -1) {
 201                     // Inline math ends, not nested inside display math.
 202                     // Wrap the span around it.
 203                     $text = $this->insert_span($text, $inlinestart, $i);
 204
 205                     $inlinestart = -1; // Reset.
 206                     $i += 28; // The $text length changed due to the <span>.
 207                     $len += 28;
 208                     $changesdone = true;
 209                 }
 210             } else {
 211                 // Display math open.
 212                 if (($text[$i - 1] === '\\' && $text[$i] === ']' && $displaybracket) ||
 213                         ($text[$i - 1] === '$' && $text[$i] === '$' && $displaydollar)) {
 214                     // Display math ends, wrap the span around it.
 215                     $text = $this->insert_span($text, $displaystart, $i);
 216
 217                     $displaystart = -1; // Reset.
 218                     $displaybracket = false;
 219                     $displaydollar = false;
 220                     $i += 28; // The $text length changed due to the <span>.
 221                     $len += 28;
 222                     $changesdone = true;
 223                 }
 224             }
 225
 226             ++$i;
 227         }
 228         return array($text, $changesdone);
 229     }
 230
 231     /**
 232      * Wrap a portion of the $text inside a no link span
 233      * (<span class="nolink"></span>). The whole text is then returned.
 234      *
 235      * @param string $text The text to modify.
 236      * @param int $start The start index of the substring in $text that should
 237      * be wrapped in the span.
 238      * @param int $end The end index of the substring in $text that should be
 239      * wrapped in the span.
 240      * @return string The whole $text with the span inserted around
 241      * the defined substring.
 242      */
 243     protected function insert_span($text, $start, $end) {
 244         return substr_replace($text,
 245                 '<span class="nolink">'. substr($text, $start, $end - $start + 1) .'</span>',
 246                 $start,
 247                 $end - $start + 1);
 248     }
 249 }