From 3cea86632d8442ecda805ec588be85f79aae936e Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Tue, 6 Jun 2023 06:51:17 +0200
Subject: [PATCH] LibWeb: Invalidate the layout tree on DOM node insertion

---
 .../expected/append-child-must-update-layout-tree.txt     | 2 ++
 .../Text/input/append-child-must-update-layout-tree.html  | 8 ++++++++
 Userland/Libraries/LibWeb/DOM/Node.cpp                    | 2 ++
 3 files changed, 12 insertions(+)
 create mode 100644 Tests/LibWeb/Text/expected/append-child-must-update-layout-tree.txt
 create mode 100644 Tests/LibWeb/Text/input/append-child-must-update-layout-tree.html

diff --git a/Tests/LibWeb/Text/expected/append-child-must-update-layout-tree.txt b/Tests/LibWeb/Text/expected/append-child-must-update-layout-tree.txt
new file mode 100644
index 0000000000..51fe249b9c
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/append-child-must-update-layout-tree.txt
@@ -0,0 +1,2 @@
+Hello
+friends
diff --git a/Tests/LibWeb/Text/input/append-child-must-update-layout-tree.html b/Tests/LibWeb/Text/input/append-child-must-update-layout-tree.html
new file mode 100644
index 0000000000..8bd7944db0
--- /dev/null
+++ b/Tests/LibWeb/Text/input/append-child-must-update-layout-tree.html
@@ -0,0 +1,8 @@
+<script src="include.js"></script>
+<script>
+    test(() => {
+        println("Hello");
+        document.body.offsetWidth // Force a layout
+        println("friends"); // This will append a text child to the output element, and should update the layout tree.
+    });
+</script>
diff --git a/Userland/Libraries/LibWeb/DOM/Node.cpp b/Userland/Libraries/LibWeb/DOM/Node.cpp
index 15fa30d4aa..0fa190b776 100644
--- a/Userland/Libraries/LibWeb/DOM/Node.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Node.cpp
@@ -487,6 +487,8 @@ void Node::insert_before(JS::NonnullGCPtr<Node> node, JS::GCPtr<Node> child, boo
 
     // FIXME: This will need to become smarter when we implement the :has() selector.
     invalidate_style();
+
+    document().invalidate_layout();
 }
 
 // https://dom.spec.whatwg.org/#concept-node-pre-insert