Cache the result of a rendered reaction

This greatly reduces the time spent when the same reaction appears multiple times. It does increase the static memory usage but at the same time cuts the GC'ed memory by a lot.

In a test with 32 calls this reduced the time by ~75% and reduced memory usage by ~71%.

Author: dtdesign

wcfsetup/install/files/lib/data/reaction/type/ReactionType.class.php

@@ -27,6 +27,12 @@ class ReactionType extends DatabaseObject implements ITitledObject
      */
     protected static $databaseTableIndexName = 'reactionTypeID';
 
+    /**
+     * Cache for the rendered icons.
+     * @var array<int, string>
+     */
+    private array $renderedIcons = [];
+
     /**
      * @inheritDoc
      */
@@ -42,9 +48,13 @@ public function getTitle(): string
      */
     public function renderIcon()
     {
-        return WCF::getTPL()->render('wcf', 'reactionTypeImage', [
-            'reactionType' => $this,
-        ]);
+        if (!isset($this->renderedIcons[$this->reactionTypeID])) {
+            $this->renderedIcons[$this->reactionTypeID] =  WCF::getTPL()->render('wcf', 'reactionTypeImage', [
+                'reactionType' => $this,
+            ]);
+        }
+
+        return $this->renderedIcons[$this->reactionTypeID];
     }
 
     /**