From 21d9da0f3b0f43cff7dc8ff0ccbfda76192f6517 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Wed, 22 Nov 2023 23:57:34 +0100
Subject: [PATCH] LibWeb: Unregister IntersectionObserver from registration
 document

Before this change, there was some confusion possible where an IO would
try to find its way back to the document where we registered it.
This led to an assertion failure in the test I'm adding in the next
commit, so let's fix this first.

IOs now (weakly) remember the document where they are registered, and
only unregister from there.
---
 .../LibWeb/IntersectionObserver/IntersectionObserver.cpp  | 8 ++++----
 .../LibWeb/IntersectionObserver/IntersectionObserver.h    | 3 +++
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.cpp b/Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.cpp
index f9a9c7361c..cc0c6fb8cb 100644
--- a/Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.cpp
+++ b/Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.cpp
@@ -53,17 +53,17 @@ IntersectionObserver::IntersectionObserver(JS::Realm& realm, JS::GCPtr<WebIDL::C
     , m_thresholds(move(thresholds))
 {
     intersection_root().visit([this](auto& node) {
-        node->document().register_intersection_observer({}, *this);
+        m_document = node->document();
     });
+    m_document->register_intersection_observer({}, *this);
 }
 
 IntersectionObserver::~IntersectionObserver() = default;
 
 void IntersectionObserver::finalize()
 {
-    intersection_root().visit([this](auto& node) {
-        node->document().unregister_intersection_observer({}, *this);
-    });
+    if (m_document)
+        m_document->unregister_intersection_observer({}, *this);
 }
 
 void IntersectionObserver::initialize(JS::Realm& realm)
diff --git a/Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.h b/Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.h
index 83fbee91c0..a8ce7b333f 100644
--- a/Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.h
+++ b/Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.h
@@ -83,6 +83,9 @@ private:
 
     // https://www.w3.org/TR/intersection-observer/#dom-intersectionobserver-observationtargets-slot
     Vector<JS::NonnullGCPtr<DOM::Element>> m_observation_targets;
+
+    // AD-HOC: This is the document where we've registered the IntersectionObserver.
+    WeakPtr<DOM::Document> m_document;
 };
 
 }