MathJax: added the MathJax addon to the repository

mathjax/README

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+Addon for Friendika to include MathJax (LaTeX math syntax)
+
+This addon lets your users use LaTeX to type mathematical formulas
+within their posts. MathJax takes care about the best method for the
+browser to display the formula and provides compatibility to 99%
+of the modern browsers.
+
+You can either use the MathJax CDN online, thus loading the required javascript
+libraries from the MathJax cloud, or use a local installation of MathJax.
+Please see the plugin settings in the admin panel for configuration possibles.
+If you don't set up a local MathJax instance, leave the configuration untouched
+it will fall back to the MathJax cloud as default value.
+
+If you don't use the admin panel add mathjax to the list of active addons
+
+$a->config['system']['addon'] = [..., mathjax, ...]
+
+To select the source of the included javascript libraries add a line
+
+$a->config['mathjax']['baseurl'] = 'the URL to your MathJax installation';
+
+to your .htconfig.php file. If this line is not there, the addon assumes that
+you want to use the MathJax cloud (CDN).
+
+Please note that your usage of the CDN is governed by the "MathJax CDN Terms of
+Service" see http://www.mathjax.org/download/mathjax-cdn-terms-of-service/
+
+Author:  Tobias Diekershoff
+         http://diekershoff.homeunix.net/friendika/profile/tobias
+         email: tobias.diekershoff@gmx.net
+

mathjax/admin.tpl

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+{{ inc field_input.tpl with $field=$baseurl }}{{endinc }}
+<div class="submit"><input type="submit" name="page_site" value="$submit" /></div>

mathjax/mathjax.php

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+<?php
+
+/**
+ * Name: MathJax
+ * Description: Addon for Friendika to include MathJax (LaTeX math syntax)
+ * Version: 1.0
+ * Author: Tobias Diekershoff <http://diekershoff.homeunix.net/friendika/profile/tobias>
+ * License: 3-clause BSD license
+ */
+
+function mathjax_install() {
+    register_hook('page_header', 'addon/mathjax/mathjax.php', 'mathjax_page_header');
+    register_hook('plugin_settings', 'addon/mathjax/mathjax.php', 'mathjax_settings'); 
+    register_hook('plugin_settings_post', 'addon/mathjax/mathjax.php', 'mathjax_settings_post');
+    logger('installed js_math plugin');
+}
+function mathjax_uninstall() {
+    unregister_hook('page_header', 'addon/mathjax/mathjax.php', 'mathjax_page_header');
+    unregister_hook('plugin_settings', 'addon/mathjax/mathjax.php', 'mathjax_settings'); 
+    unregister_hook('plugin_settings_post', 'addon/mathjax/mathjax.php', 'mathjax_settings_post');
+}
+function mathjax_settings_post ($a, $post) {
+    if (! local_user())
+        return;
+    // don't check statusnet settings if statusnet submit button is not clicked
+    if (!x($_POST,'mathjax-submit'))
+        return;
+    set_pconfig(local_user(),'mathjax','use',intval($_POST['mathjax_use']));
+}
+function mathjax_settings (&$a, &$s) {
+    if (! local_user())
+        return;
+    $use = get_pconfig(local_user(),'mathjax','use');
+    $usetext = (($use) ? ' checked="checked" ' : '');
+    $s .= '<div class="settings-block">';
+    $s .= '<h3>MathJax '.t('Settings').'</h3>';
+    $s .= '<p>'.t('The MathJax addon renders mathematical formulae written using the LaTeX syntax surrounded by the usual $$ or an eqnarray block in the postings of your wall,network tab and private mail.').'</p>';
+    $s .= '<label id="mathjax_label" for="mathjax_use">'.t('Use the MathJax renderer').'</label>';
+    $s .= '<input id="mathjax_use" type="checkbox" name="mathjax_use" value="1"'. $usetext .' />';
+    $s .= '<div class="clear"></div>';
+
+    $s .= '<div class="settings-submit-wrapper" ><input type="submit" id="mathjax-submit" name="mathjax-submit" class="settings-submit" value="' . t('Submit') . '" /></div>';
+    $s .= '</div>';
+}
+/*  we need to add one JavaScript include command to the html output
+ *  note that you have to check the jsmath/easy/load.js too.
+ */
+function mathjax_page_header($a, &$b) {
+    //  if the visitor of the page is not a local_user, use MathJax
+    //  otherwise check the users settings.
+    $url = get_config ('mathjax','baseurl','http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML');
+    if (! local_user()) {
+        $b .= '<script type="text/javascript" src="'.$url.'"></script>';
+    } else {
+        $use = get_pconfig(local_user(),'mathjax','use');
+        if ($use) { 
+            $b .= '<script type="text/javascript" src="'.$url.'"></script>';
+        }
+    }
+}
+function mathjax_plugin_admin_post (&$a) {
+    $baseurl = ((x($_POST, 'baseurl')) ? trim($_POST['baseurl']) : 'http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML');
+    set_config('mathjax','baseurl',$baseurl);
+    info( t('Settings updated.'). EOL);
+}
+function mathjax_plugin_admin (&$a, &$o) {
+	$t = file_get_contents( dirname(__file__)."/admin.tpl");
+        if (get_config('mathjax','baseurl','') == '') {
+            set_config('mathjax','baseurl','http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML');
+        }
+        $o = replace_macros( $t, array(
+		'$baseurl' => array('baseurl', t('MathJax Base URL'), get_config('mathjax','baseurl' ), t('The URL for the javascript file that should be included to use MathJax. Can be either the MathJax CDN or another installation of MathJax.')),
+            ));
+}