Add tu filter twig extension to admin

admin.php

@@ -291,6 +291,7 @@ class AdminPlugin extends Plugin
     protected function initializeAdmin()
     {
         $this->enable([
+            'onTwigExtensions'    => ['onTwigExtensions', 1000],
             'onPagesInitialized'  => ['onPagesInitialized', 1000],
             'onTwigTemplatePaths' => ['onTwigTemplatePaths', 1000],
             'onTwigSiteVariables' => ['onTwigSiteVariables', 1000],
@@ -335,4 +336,13 @@ class AdminPlugin extends Plugin
         // Get theme for admin
         $this->theme = $this->config->get('plugins.admin.theme', 'grav');
     }
+
+    /**
+     * Add Twig Extensions
+     */
+    public function onTwigExtensions()
+    {
+        require_once(__DIR__.'/twig/AdminTwigExtension.php');
+        $this->grav['twig']->twig->addExtension(new AdminTwigExtension());
+    }
 }

twig/AdminTwigExtension.php

@@ -0,0 +1,38 @@
+<?php
+namespace Grav\Plugin;
+
+use \Grav\Common\Grav;
+
+class AdminTwigExtension extends \Twig_Extension
+{
+    protected $grav;
+
+    public function __construct()
+    {
+        $this->grav = Grav::instance();
+    }
+
+    /**
+     * Returns extension name.
+     *
+     * @return string
+     */
+    public function getName()
+    {
+        return 'AdminTwigExtension';
+    }
+
+    public function getFilters()
+    {
+        return [
+            new \Twig_SimpleFilter('tu', [$this, 'tuFilter']),
+
+        ];
+    }
+
+    public function tuFilter()
+    {
+        return $this->grav['language']->translate(func_get_args());
+    }
+
+}