From 48c54e6796230dc0ad6100b84d3b4b71390c2a65 Mon Sep 17 00:00:00 2001
From: networkException <git@nwex.de>
Date: Sun, 3 Jul 2022 20:54:13 +0200
Subject: [PATCH] LibWeb: Use lowercase type selectors to match against html
 elements

Previously we would fail to match a selector like "NAV" against a <nav>
html element.

Note that the strings must be identical in XML Documents.
---
 Userland/Libraries/LibWeb/CSS/SelectorEngine.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Userland/Libraries/LibWeb/CSS/SelectorEngine.cpp b/Userland/Libraries/LibWeb/CSS/SelectorEngine.cpp
index 43794e2f6b..d31b7ad564 100644
--- a/Userland/Libraries/LibWeb/CSS/SelectorEngine.cpp
+++ b/Userland/Libraries/LibWeb/CSS/SelectorEngine.cpp
@@ -341,6 +341,9 @@ static inline bool matches(CSS::Selector::SimpleSelector const& component, DOM::
     case CSS::Selector::SimpleSelector::Type::Class:
         return element.has_class(component.name());
     case CSS::Selector::SimpleSelector::Type::TagName:
+        // See https://html.spec.whatwg.org/multipage/semantics-other.html#case-sensitivity-of-selectors
+        if (is<HTML::HTMLElement>(element) && element.document().document_type() != DOM::Document::Type::XML)
+            return component.name().equals_ignoring_case(element.local_name());
         return component.name() == element.local_name();
     case CSS::Selector::SimpleSelector::Type::Attribute:
         return matches_attribute(component.attribute(), element);