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<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
/**
* Moodle - Filter for converting TeX expressions to cached gif images
*
* This Moodle text filter converts TeX expressions delimited
* by either $$...$$ or by <tex...>...</tex> tags to gif images using
* mimetex.cgi obtained from http: *www.forkosh.com/mimetex.html authored by
* John Forkosh john@forkosh.com. Several binaries of this areincluded with
* this distribution.
* Note that there may be patent restrictions on the production of gif images
* in Canada and some parts of Western Europe and Japan until July 2004.
*
* @package filter
* @subpackage tex
* @copyright 2004 Zbigniew Fiedorowicz fiedorow@math.ohio-state.edu
* Originally based on code provided by Bruno Vernier bruno@vsbeducation.ca
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
defined('MOODLE_INTERNAL') || die;
/**
* Create TeX image link.
*
* @param string $imagefile name of file
* @param string $tex TeX notation (html entities already decoded)
* @param int $height O means automatic
* @param int $width O means automatic
* @param string $align
* @param string $alt
* @return string HTML markup
*/
function filter_text_image($imagefile, $tex, $height, $width, $align, $alt) {
global $CFG, $OUTPUT;
if (!$imagefile) {
throw new coding_exception('image file argument empty in filter_text_image()');
}
// Work out any necessary inline style.
$rules = array();
if ($align !== 'middle') {
$rules[] = 'vertical-align:' . $align . ';';
}
if ($height) {
$rules[] = 'height:' . $height . 'px;';
}
if ($width) {
$rules[] = 'width:' . $width . 'px;';
}
if (!empty($rules)) {
$style = ' style="' . implode('', $rules) . '" ';
} else {
$style = '';
}
// Prepare the title attribute.
// Note that we retain the title tag as TeX format rather than using
// the alt text, even if supplied. The alt text is intended for blind
// users (to provide a text equivalent to the equation) while the title
// is there as a convenience for sighted users who want to see the TeX
// code.
$title = 'title="'.s($tex).'"';
if ($alt === '') {
$alt = s($tex);
} else {
$alt = s(html_entity_decode($tex, ENT_QUOTES, 'UTF-8'));
}
// Build the output.
$anchorcontents = "<img class=\"texrender\" $title alt=\"$alt\" src=\"";
if ($CFG->slasharguments) { // Use this method if possible for better caching
$anchorcontents .= "$CFG->wwwroot/filter/tex/pix.php/$imagefile";
} else {
$anchorcontents .= "$CFG->wwwroot/filter/tex/pix.php?file=$imagefile";
}
$anchorcontents .= "\" $style/>";
if (!file_exists("$CFG->dataroot/filter/tex/$imagefile") && has_capability('moodle/site:config', get_context_instance(CONTEXT_SYSTEM))) {
$link = '/filter/tex/texdebug.php';
$action = null;
} else {
$link = new moodle_url('/filter/tex/displaytex.php', array('texexp'=>$tex));
$action = new popup_action('click', $link, 'popup', array('width'=>320,'height'=>240));
}
$output = $OUTPUT->action_link($link, $anchorcontents, $action, array('title'=>'TeX')); //TODO: the popups do not work when text caching is enabled!!
return $output;
}
/**
* TeX filtering class.
*/
class filter_tex extends moodle_text_filter {
function filter($text, array $options = array()) {
global $CFG, $DB;
/// Do a quick check using stripos to avoid unnecessary work
if (!preg_match('/<tex/i',$text) and !strstr($text,'$$') and !strstr($text,'\\[') and !preg_match('/\[tex/i',$text)) { //added one more tag (dlnsk)
return $text;
}
# //restrict filtering to forum 130 (Maths Tools on moodle.org)
# $scriptname = $_SERVER['SCRIPT_NAME'];
# if (!strstr($scriptname,'/forum/')) {
# return $text;
# }
# if (strstr($scriptname,'post.php')) {
# $parent = forum_get_post_full($_GET['reply']);
# $discussion = $DB->get_record("forum_discussions", array("id"=>$parent->discussion));
# } else if (strstr($scriptname,'discuss.php')) {
# $discussion = $DB->get_record("forum_discussions", array("id"=>$_GET['d']));
# } else {
# return $text;
# }
# if ($discussion->forum != 130) {
# return $text;
# }
$text .= ' ';
preg_match_all('/\$(\$\$+?)([^\$])/s',$text,$matches);
for ($i=0; $i<count($matches[0]); $i++) {
$replacement = str_replace('$','&#x00024;', $matches[1][$i]).$matches[2][$i];
$text = str_replace($matches[0][$i], $replacement, $text);
}
// <tex> TeX expression </tex>
// or <tex alt="My alternative text to be used instead of the TeX form"> TeX expression </tex>
// or $$ TeX expression $$
// or \[ TeX expression \] // original tag of MathType and TeXaide (dlnsk)
// or [tex] TeX expression [/tex] // somtime it's more comfortable than <tex> (dlnsk)
preg_match_all('/<tex(?:\s+alt=["\'](.*?)["\'])?>(.+?)<\/tex>|\$\$(.+?)\$\$|\\\\\[(.+?)\\\\\]|\\[tex\\](.+?)\\[\/tex\\]/is', $text, $matches);
for ($i=0; $i<count($matches[0]); $i++) {
$texexp = $matches[2][$i] . $matches[3][$i] . $matches[4][$i] . $matches[5][$i];
$alt = $matches[1][$i];
$texexp = str_replace('<nolink>','',$texexp);
$texexp = str_replace('</nolink>','',$texexp);
$texexp = str_replace('<span class="nolink">','',$texexp);
$texexp = str_replace('</span>','',$texexp);
$texexp = preg_replace("/<br[[:space:]]*\/?>/i", '', $texexp); //dlnsk
$align = "middle";
if (preg_match('/^align=bottom /',$texexp)) {
$align = "text-bottom";
$texexp = preg_replace('/^align=bottom /','',$texexp);
} else if (preg_match('/^align=top /',$texexp)) {
$align = "text-top";
$texexp = preg_replace('/^align=top /','',$texexp);
}
// decode entities encoded by editor, luckily there is very little chance of double decoding
$texexp = html_entity_decode($texexp, ENT_QUOTES, 'UTF-8');
if ($texexp === '') {
continue;
}
$md5 = md5($texexp);
if (!$DB->record_exists("cache_filters", array("filter"=>"tex", "md5key"=>$md5))) {
$texcache = new stdClass();
$texcache->filter = 'tex';
$texcache->version = 1;
$texcache->md5key = $md5;
$texcache->rawtext = $texexp;
$texcache->timemodified = time();
$DB->insert_record("cache_filters", $texcache, false);
}
$filename = $md5 . ".{$CFG->filter_tex_convertformat}";
$text = str_replace( $matches[0][$i], filter_text_image($filename, $texexp, 0, 0, $align, $alt), $text);
}
return $text;
}
}
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