filter/tex/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  * Moodle - Filter for converting TeX expressions to cached gif images
  19  *
  20  * This Moodle text filter converts TeX expressions delimited
  21  * by either $$...$$ or by <tex...>...</tex> tags to gif images using
  22  * mimetex.cgi obtained from http: *www.forkosh.com/mimetex.html authored by
  23  * John Forkosh john@forkosh.com.  Several binaries of this areincluded with
  24  * this distribution.
  25  * Note that there may be patent restrictions on the production of gif images
  26  * in Canada and some parts of Western Europe and Japan until July 2004.
  27  *
  28  * @package    filter
  29  * @subpackage tex
  30  * @copyright  2004 Zbigniew Fiedorowicz fiedorow@math.ohio-state.edu
  31  *             Originally based on code provided by Bruno Vernier bruno@vsbeducation.ca
  32  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  33  */
  34
  35 defined('MOODLE_INTERNAL') || die;
  36
  37 require_once($CFG->libdir . '/classes/useragent.php');
  38
  39 /**
  40  * Create TeX image link.
  41  *
  42  * @param string $imagefile name of file
  43  * @param string $tex TeX notation (html entities already decoded)
  44  * @param int $height O means automatic
  45  * @param int $width O means automatic
  46  * @param string $align
  47  * @param string $alt
  48  * @return string HTML markup
  49  */
  50 function filter_text_image($imagefile, $tex, $height, $width, $align, $alt) {
  51     global $CFG, $OUTPUT;
  52
  53     if (!$imagefile) {
  54         throw new coding_exception('image file argument empty in filter_text_image()');
  55     }
  56
  57     // Work out any necessary inline style.
  58     $rules = array();
  59     if ($align !== 'middle') {
  60         $rules[] = 'vertical-align:' . $align . ';';
  61     }
  62     if ($height) {
  63         $rules[] = 'height:' . $height . 'px;';
  64     }
  65     if ($width) {
  66         $rules[] = 'width:' . $width . 'px;';
  67     }
  68     if (!empty($rules)) {
  69         $style = ' style="' . implode('', $rules) . '" ';
  70     } else {
  71         $style = '';
  72     }
  73
  74     // Prepare the title attribute.
  75     // Note that we retain the title tag as TeX format rather than using
  76     // the alt text, even if supplied. The alt text is intended for blind
  77     // users (to provide a text equivalent to the equation) while the title
  78     // is there as a convenience for sighted users who want to see the TeX
  79     // code.
  80     $title = 'title="'.s($tex).'"';
  81
  82     if ($alt === '') {
  83         $alt = s($tex);
  84     } else {
  85         $alt = s(html_entity_decode($tex, ENT_QUOTES, 'UTF-8'));
  86     }
  87
  88     // Build the output.
  89     $anchorcontents = "<img class=\"texrender\" $title alt=\"$alt\" src=\"";
  90     if ($CFG->slasharguments) {        // Use this method if possible for better caching
  91         $anchorcontents .= "$CFG->wwwroot/filter/tex/pix.php/$imagefile";
  92     } else {
  93         $anchorcontents .= "$CFG->wwwroot/filter/tex/pix.php?file=$imagefile";
  94     }
  95     $anchorcontents .= "\" $style/>";
  96
  97     if (!file_exists("$CFG->dataroot/filter/tex/$imagefile") && has_capability('moodle/site:config', context_system::instance())) {
  98         $link = '/filter/tex/texdebug.php';
  99         $action = null;
 100     } else {
 101         $link = new moodle_url('/filter/tex/displaytex.php', array('texexp'=>$tex));
 102         $action = new popup_action('click', $link, 'popup', array('width'=>320,'height'=>240));
 103     }
 104     $output = $OUTPUT->action_link($link, $anchorcontents, $action, array('title'=>'TeX')); //TODO: the popups do not work when text caching is enabled!!
 105     $output = "<span class=\"MathJax_Preview\">$output</span><script type=\"math/tex\">$tex</script>";
 106
 107     return $output;
 108 }
 109
 110
 111 /**
 112  * TeX filtering class.
 113  */
 114 class filter_tex extends moodle_text_filter {
 115     function filter($text, array $options = array()) {
 116
 117         global $CFG, $DB;
 118
 119         /// Do a quick check using stripos to avoid unnecessary work
 120         if ((!preg_match('/<tex/i', $text)) &&
 121                 (strpos($text,'$$') === false) &&
 122                 (strpos($text,'\\[') === false) &&
 123                 (strpos($text, '\\(') === false) &&
 124                 (!preg_match('/\[tex/i',$text))) {
 125             return $text;
 126         }
 127
 128 #    //restrict filtering to forum 130 (Maths Tools on moodle.org)
 129 #    $scriptname = $_SERVER['SCRIPT_NAME'];
 130 #    if (!strstr($scriptname,'/forum/')) {
 131 #        return $text;
 132 #    }
 133 #    if (strstr($scriptname,'post.php')) {
 134 #        $parent = forum_get_post_full($_GET['reply']);
 135 #        $discussion = $DB->get_record("forum_discussions", array("id"=>$parent->discussion));
 136 #    } else if (strstr($scriptname,'discuss.php')) {
 137 #        $discussion = $DB->get_record("forum_discussions", array("id"=>$_GET['d']));
 138 #    } else {
 139 #        return $text;
 140 #    }
 141 #    if ($discussion->forum != 130) {
 142 #        return $text;
 143 #    }
 144         $text .= ' ';
 145         preg_match_all('/\$(\$\$+?)([^\$])/s',$text,$matches);
 146         for ($i=0; $i<count($matches[0]); $i++) {
 147             $replacement = str_replace('$','&#x00024;', $matches[1][$i]).$matches[2][$i];
 148             $text = str_replace($matches[0][$i], $replacement, $text);
 149         }
 150
 151         // <tex> TeX expression </tex>
 152         // or <tex alt="My alternative text to be used instead of the TeX form"> TeX expression </tex>
 153         // or $$ TeX expression $$
 154         // or \[ TeX expression \]          // original tag of MathType and TeXaide (dlnsk)
 155         // or [tex] TeX expression [/tex]   // somtime it's more comfortable than <tex> (dlnsk)
 156         $rules = array(
 157             '<tex(?:\s+alt=["\'](.*?)["\'])?>(.+?)<\/tex>',
 158             '\$\$(.+?)\$\$',
 159             '\\\\\[(.+?)\\\\\]',
 160             '\\\\\((.+?)\\\\\)',
 161             '\\[tex\\](.+?)\\[\/tex\\]'
 162         );
 163         $megarule = '/' . implode($rules, '|') . '/is';
 164         preg_match_all($megarule, $text, $matches);
 165         for ($i=0; $i<count($matches[0]); $i++) {
 166             $texexp = '';
 167             for ($j = 0; $j < count($rules); $j++) {
 168                 $texexp .= $matches[$j + 2][$i];
 169             }
 170             $alt = $matches[1][$i];
 171             $texexp = str_replace('<nolink>','',$texexp);
 172             $texexp = str_replace('</nolink>','',$texexp);
 173             $texexp = str_replace('<span class="nolink">','',$texexp);
 174             $texexp = str_replace('</span>','',$texexp);
 175             $texexp = preg_replace("/<br[[:space:]]*\/?>/i", '', $texexp);  //dlnsk
 176             $align = "middle";
 177             if (preg_match('/^align=bottom /',$texexp)) {
 178               $align = "text-bottom";
 179               $texexp = preg_replace('/^align=bottom /','',$texexp);
 180             } else if (preg_match('/^align=top /',$texexp)) {
 181               $align = "text-top";
 182               $texexp = preg_replace('/^align=top /','',$texexp);
 183             }
 184
 185             // decode entities encoded by editor, luckily there is very little chance of double decoding
 186             $texexp = html_entity_decode($texexp, ENT_QUOTES, 'UTF-8');
 187
 188             if ($texexp === '') {
 189                 continue;
 190             }
 191
 192             $md5 = md5($texexp);
 193             if (!$DB->record_exists("cache_filters", array("filter"=>"tex", "md5key"=>$md5))) {
 194                 $texcache = new stdClass();
 195                 $texcache->filter = 'tex';
 196                 $texcache->version = 1;
 197                 $texcache->md5key = $md5;
 198                 $texcache->rawtext = $texexp;
 199                 $texcache->timemodified = time();
 200                 $DB->insert_record("cache_filters", $texcache, false);
 201             }
 202             $convertformat = get_config('filter_tex', 'convertformat');
 203             if ($convertformat == 'svg' && !core_useragent::supports_svg()) {
 204                 $convertformat = 'png';
 205             }
 206             $filename = $md5.".{$convertformat}";
 207             $text = str_replace( $matches[0][$i], filter_text_image($filename, $texexp, 0, 0, $align, $alt), $text);
 208         }
 209         return $text;
 210     }
 211 }
 212
 213