Blocking exercise depending of the session dates and the session visibility.

main/exercice/exercise_submit.php

@@ -913,9 +913,20 @@ $interbreadcrumb[]= array ("url" => $urlMainExercise."exercice.php?gradebook=$gr
 $interbreadcrumb[]= array ("url" => "#","name" => $objExercise->name);
 
 if ($origin != 'learnpath') { //so we are not in learnpath tool
-    Display :: display_header($nameTools,'Exercises');
+    Display :: display_header($nameTools, 'Exercises');
     if (!api_is_allowed_to_session_edit()) {
-        Display :: display_warning_message(get_lang('SessionIsReadOnly'));
+        $sessionId = api_get_session_id();
+        if (!empty($sessionId)) {
+            $session_visibility = api_get_session_visibility($sessionId);
+            switch ($session_visibility) {
+                case SESSION_VISIBLE_READ_ONLY:
+                    Display::display_warning_message(get_lang('SessionIsReadOnly'));
+                    break;
+                case SESSION_INVISIBLE:
+                    api_not_allowed(true);
+                    break;
+            }
+        }
     }
 } else {
     Display::display_reduced_header();