feat: add a new template: parallel pages

user/plugins/m3-p2/m3-p2.php

 <?php
 namespace Grav\Plugin;
 
+use Grav\Common\Grav;
 use Grav\Common\Page\Page;
 use Grav\Common\Page\Pages;
 use Grav\Common\Plugin;
@@ -44,9 +45,8 @@ class M3P2Plugin extends Plugin
      */
     public function onPluginsInitialized()
     {
-        // Don't proceed if we are in the admin plugin
         if ($this->isAdmin()) {
-            return;
+            return;  // Don't proceed if we are in the admin backend
         }
 
         $uri = $this->grav['uri'];
@@ -60,10 +60,15 @@ class M3P2Plugin extends Plugin
             ]);
         }
 
+        $this->enable([
+            'onTwigInitialized' => ['setupTwigGoodies', 0],
+        ]);
+
         $this->enable([
             'onTwigInitialized' => ['setupWebIdeUrl', 0],
         ]);
 
+
 //        $that_page_route = $uri->query('page');
 //        if ($that_page_route) {
 //            $this->enable([
@@ -95,10 +100,11 @@ class M3P2Plugin extends Plugin
     public function onSyncPageInitialized()
     {
         // shell cwd is project root
+        $out = "";
 
-        $out = "Opening a fortune cookie…\n\n\n";
-//        $out .= shell_exec("fortune | cowsay -e Oø -f dragon") . "\n";
-        $out .= shell_exec("fortune") . "\n\n";
+        //$out = "Opening a fortune cookie…\n\n\n";
+        //$out .= shell_exec("fortune") . "\n\n";
+        //$out .= shell_exec("fortune | cowsay -e Oø -f dragon") . "\n";
 
         $out .= "Trying to sync content with GitLab…\n\n\n";
         $out .= shell_exec("cd user/pages && git pull --rebase --autostash origin master 2>&1") . "\n";
@@ -108,6 +114,17 @@ class M3P2Plugin extends Plugin
         die("<pre>".$out."</pre>");  // This is all I could find to write to the page.
     }
 
+    public function setupTwigGoodies()
+    {
+        /** @var Pages $pages */
+        $pages = Grav::instance()['pages'];
+        $this->grav['twig']->twig()->addGlobal('localized_pages', $pages);
+
+        $this->grav['twig']->twig()->addFilter(
+            new \Twig_SimpleFilter('to_page', [$this, 'getPageForPath'])
+        );
+    }
+
     public function setupWebIdeUrl()
     {
         $this->grav['twig']->twig()->addFilter(
@@ -130,6 +147,46 @@ class M3P2Plugin extends Plugin
 //        );
 //    }
 
+    public function getPageForPath($meta)
+    {
+        if (is_array($meta)) {
+            if (isset($meta['path'])) {
+                $path = $meta['path'];
+            } else {
+                trigger_error("Missing `path` in: ".print_r($meta, true));
+            }
+        } elseif (is_string($meta)) {
+            $path = $meta;
+        } else {
+            trigger_error("Unrecognized page: ".print_r($meta, true));
+        }
+
+        /** @var Pages $pages */
+        $pages = Grav::instance()['pages'];
+
+        $page = $pages->find($path);
+
+        if ( ! $page) {
+            try {
+                $page = $pages->get($path);
+            } catch (\Exception $e) {}
+        }
+        if ( ! $page) {
+            try {
+                $cwd = $pages->root()->filePath();  // ends with /
+
+                if (0 === strpos($path, '/')) {
+                    $page = $pages->get($cwd . substr($path, 1));
+                } else {
+                    $page = $pages->get($cwd . $path);
+                }
+//                die($cwd . $path);
+            } catch (\Exception $e) {}
+        }
+
+        return $page;
+    }
+
     public function getWebIdeUrlForPage(Page $page)
     {
         $url = "https://gitlab.m3p2.com/-/ide/project/m3p2/courses/edit/master/-/";  # todo: move to YAML config

user/themes/textbook/templates/parallel.html.twig

+{% extends 'partials/base.html.twig' %}
+
+
+
+{% block stylesheets %}
+    {% do assets.addCss('theme://css/columns.css') %}
+    {{ parent() }}
+{% endblock %}
+
+{% block body %}
+
+{#    {{ localized_pages.instances | keys | join('<br>') }}#}
+
+    <div class="claude-columns">
+    {% for column_page_meta in page.header.pages %}
+        {% set column = column_page_meta | to_page %}
+        {% if column %}
+        <section id="{{ macro.pageLinkName(column.menu) }}" class="claude-column">
+            {{ column.content | raw }}
+            {% include 'partials/contributions-incentive.html.twig' with {page: column} %}
+        </section>
+        {% else %}
+            <p class="col-4">
+                Column <code>{{ column_page_meta | join(' ') }}</code> not found.
+            </p>
+        {% endif %}
+    {% endfor %}
+    </div>
+    {#{{ page.content|raw }}#}
+{% endblock %}
+
+
+{# Disable the Rosetta option of the language selector, for now. #}
+{# How to access the Rosettas of the children poages? #}
+{% block header_language_selection %}
+{% embed 'partials/language-selector.html.twig' %}
+    {% block polyglot_language_selector %}{% endblock %}
+{% endembed %}
+{% endblock %}