From 09502cf627df11ff1d61cefb59c8805fa63223b5 Mon Sep 17 00:00:00 2001
From: Jarek Radosz <jradosz@gmail.com>
Date: Wed, 2 Aug 2023 15:24:30 +0200
Subject: [PATCH] DEV: Reduce the number of IntersectionObservers (#22933)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

…by adding the `chat/track-message` modifier only to the last thread rather than all of them

(plus: don't use Ember's `lastObject`)
---
 .../discourse/components/chat/thread-list.hbs         | 11 ++++-------
 .../discourse/components/chat/thread-list.js          |  4 ++++
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/plugins/chat/assets/javascripts/discourse/components/chat/thread-list.hbs b/plugins/chat/assets/javascripts/discourse/components/chat/thread-list.hbs
index ed91b635bc3..e7117ba65fe 100644
--- a/plugins/chat/assets/javascripts/discourse/components/chat/thread-list.hbs
+++ b/plugins/chat/assets/javascripts/discourse/components/chat/thread-list.hbs
@@ -15,13 +15,10 @@
       {{#each this.sortedThreads as |thread|}}
         <Chat::ThreadList::Item
           @thread={{thread}}
-          {{chat/track-message
-            (if
-              (eq thread this.sortedThreads.lastObject)
-              this.loadThreads
-              (fn (noop))
-            )
-          }}
+          {{(if
+            (eq thread this.lastThread)
+            (modifier "chat/track-message" this.loadThreads)
+          )}}
         />
       {{else}}
         {{#if this.threadsCollection.fetchedOnce}}
diff --git a/plugins/chat/assets/javascripts/discourse/components/chat/thread-list.js b/plugins/chat/assets/javascripts/discourse/components/chat/thread-list.js
index c3d572d5560..0d9b3b6c1fe 100644
--- a/plugins/chat/assets/javascripts/discourse/components/chat/thread-list.js
+++ b/plugins/chat/assets/javascripts/discourse/components/chat/thread-list.js
@@ -57,6 +57,10 @@ export default class ChatThreadList extends Component {
       });
   }
 
+  get lastThread() {
+    return this.sortedThreads[this.sortedThreads.length - 1];
+  }
+
   get shouldRender() {
     return !!this.args.channel;
   }