MDL-46338 enrol_self: Icon should indicate enrolment availability

enrol/self/lib.php

@@ -48,8 +48,11 @@ class enrol_self_plugin extends enrol_plugin {
         $key = false;
         $nokey = false;
         foreach ($instances as $instance) {
-            if (!$instance->customint6) {
-                // New enrols not allowed.
+            if ($this->can_self_enrol($instance, false) !== true) {
+                // User can not enrol himself.
+                // Note that we do not check here if user is already enrolled for performance reasons -
+                // such check would execute extra queries for each course in the list of courses and
+                // would hide self-enrolment icons from guests.
                 continue;
             }
             if ($instance->password or $instance->customint1) {