From 1cc9fb61356ca08b6411ed7fe3e69c952a79f944 Mon Sep 17 00:00:00 2001
From: Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
Date: Sun, 7 Sep 2025 16:59:08 +0200
Subject: [PATCH] LibWeb: Use ResizeObserver instance as `this` in callback
 function

---
 Libraries/LibWeb/ResizeObserver/ResizeObserver.cpp  | 2 +-
 Tests/LibWeb/Text/input/ResizeObserver/observe.html | 6 +++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/Libraries/LibWeb/ResizeObserver/ResizeObserver.cpp b/Libraries/LibWeb/ResizeObserver/ResizeObserver.cpp
index c8398e450fd..06f87fed1ff 100644
--- a/Libraries/LibWeb/ResizeObserver/ResizeObserver.cpp
+++ b/Libraries/LibWeb/ResizeObserver/ResizeObserver.cpp
@@ -116,7 +116,7 @@ void ResizeObserver::invoke_callback(ReadonlySpan<GC::Ref<ResizeObserverEntry>>
         MUST(wrapped_records->create_data_property(property_index, record.ptr()));
     }
 
-    (void)WebIDL::invoke_callback(callback, JS::js_undefined(), WebIDL::ExceptionBehavior::Report, { { wrapped_records } });
+    (void)WebIDL::invoke_callback(callback, this, WebIDL::ExceptionBehavior::Report, { { wrapped_records } });
 }
 
 void ResizeObserver::unregister_observer_if_needed()
diff --git a/Tests/LibWeb/Text/input/ResizeObserver/observe.html b/Tests/LibWeb/Text/input/ResizeObserver/observe.html
index aab45650c4d..3f4128ddec6 100644
--- a/Tests/LibWeb/Text/input/ResizeObserver/observe.html
+++ b/Tests/LibWeb/Text/input/ResizeObserver/observe.html
@@ -23,7 +23,11 @@
             });
         }
 
-        const resizeObserver = new ResizeObserver(entries => {
+        const resizeObserver = new ResizeObserver(function (entries) {
+            if (this !== resizeObserver) {
+                println("this is not the ResizeObserver instance inside callback");
+            }
+
             for (let entry of entries) {
                 const { width, height } = entry.contentRect;
                 println(`Size changed: ${width}px x ${height}px`);