From fcaf1fefd586963a9f5d9d783fc2d981f8e8d1fd Mon Sep 17 00:00:00 2001
From: Alexander Bias <alexander.bias@uni-ulm.de>
Date: Wed, 8 Aug 2018 13:45:20 +0200
Subject: [PATCH] #225 Allow element plugins to control if they can be added

---
 classes/element.php        | 10 ++++++++++
 classes/element_helper.php |  7 +++++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/classes/element.php b/classes/element.php
index 7acad0b..134414f 100644
--- a/classes/element.php
+++ b/classes/element.php
@@ -352,6 +352,16 @@ abstract class element {
         return true;
     }
 
+    /**
+     * This defines if an element plugin can be added to a certificate.
+     * Can be overridden if an element plugin wants to take over the control.
+     *
+     * @return bool returns true if the element can be added, false otherwise
+     */
+    public static function allow_add() {
+        return true;
+    }
+
     /**
      * Handles rendering the element on the pdf.
      *
diff --git a/classes/element_helper.php b/classes/element_helper.php
index e365c70..b9775bb 100644
--- a/classes/element_helper.php
+++ b/classes/element_helper.php
@@ -412,8 +412,11 @@ class element_helper {
                 $classname = '\\customcertelement_' . $foldername . '\\element';
                 // Ensure the necessary class exists.
                 if (class_exists($classname)) {
-                    $component = "customcertelement_{$foldername}";
-                    $options[$foldername] = get_string('pluginname', $component);
+                    // Additionally, check if the user is allowed to add the element at all.
+                    if ($classname::allow_add()) {
+                        $component = "customcertelement_{$foldername}";
+                        $options[$foldername] = get_string('pluginname', $component);
+                    }
                 }
             }
         }