/filter/tex/filter.php

<?PHP

/////////////////////////////////////////////////////////////////////////////

//                                                                         //

// NOTICE OF COPYRIGHT                                                     //

//                                                                         //

// Moodle - Filter for converting TeX expressions to cached gif images     //

//                                                                         //

// Copyright (C) 2004 Zbigniew Fiedorowicz fiedorow@math.ohio-state.edu    //

// Originally based on code provided by Bruno Vernier bruno@vsbeducation.ca//

// This program 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 2 of the License, or       //

// (at your option) any later version.                                     //

//                                                                         //

// This program 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:                            //

//                                                                         //

//          http://www.gnu.org/copyleft/gpl.html                           //

//                                                                         //

/////////////////////////////////////////////////////////////////////////////

//-------------------------------------------------------------------------

// NOTE: 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.

//-------------------------------------------------------------------------

/////////////////////////////////////////////////////////////////////////////

//  To activate this filter, add a line like this to your                  //

//  list of filters in your Filter configuration:                          //

//                                                                         //

//       filter/tex/filter.php                                             //

/////////////////////////////////////////////////////////////////////////////



function string_file_picture_tex($imagefile, $tex= "", $height="", $width="", $align="middle", $alt='') {

    global $CFG;



    if ($alt==='') {

        $alt = s($tex);

    }



    // 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.

    if ($tex) {

        $tex = str_replace('&','&amp;',$tex);

        $tex = str_replace('<','&lt;',$tex);

        $tex = str_replace('>','&gt;',$tex);

        $tex = str_replace('"','&quot;',$tex);

        $tex = str_replace("\'",'&#39;',$tex);

        // 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. 

        $title = "title=\"$tex\"";

    }



    // Build the output.

    $output = "";

    if ($imagefile) {

        if (!file_exists("$CFG->dataroot/filter/tex/$imagefile") && has_capability('moodle/site:config', get_context_instance(CONTEXT_SYSTEM))) {

          $output .= "<a href=\"$CFG->wwwroot/filter/tex/texdebug.php\">";

        } else {

          $output .= "<a target=\"popup\" title=\"TeX\" href=";

          $output .= "\"$CFG->wwwroot/filter/tex/displaytex.php?";

          $output .= urlencode($tex) . "\" onclick=\"return openpopup('/filter/tex/displaytex.php?";

          $output .= urlencode($tex) . "', 'popup', 'menubar=0,location=0,scrollbars,";

          $output .= "resizable,width=300,height=240', 0);\">";

        }

        $output .= "<img class=\"texrender\" $title alt=\"$alt\" src=\"";

        if ($CFG->slasharguments) {        // Use this method if possible for better caching

            $output .= "$CFG->wwwroot/filter/tex/pix.php/$imagefile";

        } else {

            $output .= "$CFG->wwwroot/filter/tex/pix.php?file=$imagefile";

        }

        $output .= "\" $style/>";

        $output .= "</a>";

    } else {

        $output .= "Error: must pass URL or course";

    }

    return $output;

}



function tex_filter ($courseid, $text) {



    global $CFG;



    /// 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']);

#        $discussion = get_record("forum_discussions","id",$parent->discussion);

#    } else if (strstr($scriptname,'discuss.php')) {

#        $discussion = get_record("forum_discussions","id",$_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 = eregi_replace("<br[[:space:]]*\/?>", '', $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);

        }

        $md5 = md5($texexp);

        if (! $texcache = get_record("cache_filters","filter","tex", "md5key", $md5)) {

            $texcache->filter = 'tex';

            $texcache->version = 1;

            $texcache->md5key = $md5;

            $texcache->rawtext = addslashes($texexp);

            $texcache->timemodified = time();

            insert_record("cache_filters",$texcache, false);

        }

        $filename = $md5 . ".{$CFG->filter_tex_convertformat}";

        $text = str_replace( $matches[0][$i], string_file_picture_tex($filename, $texexp, '', '', $align, $alt), $text);

    }

    return $text;

}



?>