From 704153c45461cb1d2caa35c0d84258b461d25637 Mon Sep 17 00:00:00 2001
From: Marina Glancy <marina@moodle.com>
Date: Mon, 22 Jun 2020 15:09:15 +0200
Subject: [PATCH 1/2] MDL-69109 core: use different cache keys for FA icon maps

---
 lib/classes/output/icon_system_fontawesome.php | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/lib/classes/output/icon_system_fontawesome.php b/lib/classes/output/icon_system_fontawesome.php
index c9dca916837..dcd18da1220 100644
--- a/lib/classes/output/icon_system_fontawesome.php
+++ b/lib/classes/output/icon_system_fontawesome.php
@@ -434,7 +434,10 @@ class icon_system_fontawesome extends icon_system_font {
         if ($this->map === []) {
             $cache = \cache::make('core', 'fontawesomeiconmapping');
 
-            $this->map = $cache->get('mapping');
+            // Create different mapping keys for different icon system classes, there may be several different
+            // themes on the same site.
+            $mapkey = 'mapping_'.preg_replace('/[^a-zA-Z0-9_]/', '_', get_class($this));
+            $this->map = $cache->get($mapkey);
 
             if (empty($this->map)) {
                 $this->map = $this->get_core_icon_map();
@@ -448,7 +451,7 @@ class icon_system_fontawesome extends icon_system_font {
                         }
                     }
                 }
-                $cache->set('mapping', $this->map);
+                $cache->set($mapkey, $this->map);
             }
 
         }

From d690ed3dd3ad6c511354b6ccf20261200d237ebf Mon Sep 17 00:00:00 2001
From: Marina Glancy <marina@moodle.com>
Date: Tue, 23 Jun 2020 16:02:33 +0200
Subject: [PATCH 2/2] MDL-69109 theme: try to load icons from the current theme

---
 lib/classes/output/icon_system.php | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/lib/classes/output/icon_system.php b/lib/classes/output/icon_system.php
index 08e88b54d2e..14e1075c2d7 100644
--- a/lib/classes/output/icon_system.php
+++ b/lib/classes/output/icon_system.php
@@ -72,22 +72,22 @@ abstract class icon_system {
     /**
      * Factory method
      *
-     * @param $type Either a specific type, or null to get the default type.
+     * @param string $type Either a specific type, or null to get the default type.
      * @return \core\output\icon_system
      */
     public final static function instance($type = null) {
         global $PAGE;
 
-        if ($type == null) {
-            if (!empty(self::$instance)) {
-                return self::$instance;
-            }
-            $type = $PAGE->theme->get_icon_system();
-            self::$instance = new $type();
-            // Default one is a singleton.
+        if (empty(self::$instance)) {
+            $icontype = $PAGE->theme->get_icon_system();
+            self::$instance = new $icontype();
+        }
+
+        // If $type is specified we need to make sure that the theme icon system supports this type,
+        // if not, we will return a generic new instance of the $type.
+        if ($type === null || is_a(self::$instance, $type)) {
             return self::$instance;
         } else {
-            // Not a singleton.
             return new $type();
         }
     }