From 46b9497a66c01f1c685cfaef21e634abfaac8df3 Mon Sep 17 00:00:00 2001
From: Sam Atkins <sam@ladybird.org>
Date: Mon, 27 Jan 2025 10:39:00 +0000
Subject: [PATCH] LibWeb/CSS: Make non-finite Numbers serialize as themselves

We're required to serialize NaN, infinity, and -infinity as their
keyword names, even after they've been converted to Numbers.
---
 Libraries/LibWeb/CMakeLists.txt               |  1 +
 Libraries/LibWeb/CSS/Number.cpp               | 25 +++++++++++++++++++
 Libraries/LibWeb/CSS/Number.h                 |  9 ++-----
 .../CSS/StyleValues/CalculatedStyleValue.cpp  |  5 ++--
 .../Userland/Libraries/LibWeb/CSS/BUILD.gn    |  1 +
 5 files changed, 31 insertions(+), 10 deletions(-)
 create mode 100644 Libraries/LibWeb/CSS/Number.cpp

diff --git a/Libraries/LibWeb/CMakeLists.txt b/Libraries/LibWeb/CMakeLists.txt
index 44234f843fe..582f6d4fc72 100644
--- a/Libraries/LibWeb/CMakeLists.txt
+++ b/Libraries/LibWeb/CMakeLists.txt
@@ -89,6 +89,7 @@ set(SOURCES
     CSS/MediaQuery.cpp
     CSS/MediaQueryList.cpp
     CSS/MediaQueryListEvent.cpp
+    CSS/Number.cpp
     CSS/Parser/ComponentValue.cpp
     CSS/Parser/GradientParsing.cpp
     CSS/Parser/Helpers.cpp
diff --git a/Libraries/LibWeb/CSS/Number.cpp b/Libraries/LibWeb/CSS/Number.cpp
new file mode 100644
index 00000000000..baed27419c5
--- /dev/null
+++ b/Libraries/LibWeb/CSS/Number.cpp
@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2022-2025, Sam Atkins <sam@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Math.h>
+#include <LibWeb/CSS/Number.h>
+
+namespace Web::CSS {
+
+String Number::to_string() const
+{
+    if (m_type == Type::IntegerWithExplicitSign)
+        return MUST(String::formatted("{:+}", m_value));
+    if (m_value == AK::Infinity<double>)
+        return "infinity"_string;
+    if (m_value == -AK::Infinity<double>)
+        return "-infinity"_string;
+    if (isnan(m_value))
+        return "NaN"_string;
+    return String::number(m_value);
+}
+
+}
diff --git a/Libraries/LibWeb/CSS/Number.h b/Libraries/LibWeb/CSS/Number.h
index d5e728efc1f..74db9e79d68 100644
--- a/Libraries/LibWeb/CSS/Number.h
+++ b/Libraries/LibWeb/CSS/Number.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022-2023, Sam Atkins <atkinssj@serenityos.org>
+ * Copyright (c) 2022-2025, Sam Atkins <sam@ladybird.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -70,12 +70,7 @@ public:
         return { Type::Number, m_value / other.m_value };
     }
 
-    String to_string() const
-    {
-        if (m_type == Type::IntegerWithExplicitSign)
-            return MUST(String::formatted("{:+}", m_value));
-        return String::number(m_value);
-    }
+    String to_string() const;
 
     bool operator==(Number const& other) const
     {
diff --git a/Libraries/LibWeb/CSS/StyleValues/CalculatedStyleValue.cpp b/Libraries/LibWeb/CSS/StyleValues/CalculatedStyleValue.cpp
index 2ea4c99495a..e02a3e05c51 100644
--- a/Libraries/LibWeb/CSS/StyleValues/CalculatedStyleValue.cpp
+++ b/Libraries/LibWeb/CSS/StyleValues/CalculatedStyleValue.cpp
@@ -871,11 +871,10 @@ CalculatedStyleValue::CalculationResult ConstantCalculationNode::resolve(Calcula
         return { AK::E<double>, CSSNumericType {} };
     case ConstantType::Pi:
         return { AK::Pi<double>, CSSNumericType {} };
-    // FIXME: We need to keep track of Infinity and NaN across all nodes, since they require special handling.
     case ConstantType::Infinity:
-        return { NumericLimits<double>::max(), CSSNumericType {} };
+        return { AK::Infinity<double>, CSSNumericType {} };
     case ConstantType::MinusInfinity:
-        return { NumericLimits<double>::lowest(), CSSNumericType {} };
+        return { -AK::Infinity<double>, CSSNumericType {} };
     case ConstantType::NaN:
         return { AK::NaN<double>, CSSNumericType {} };
     }
diff --git a/Meta/gn/secondary/Userland/Libraries/LibWeb/CSS/BUILD.gn b/Meta/gn/secondary/Userland/Libraries/LibWeb/CSS/BUILD.gn
index 246d1e57f48..b539f388a50 100644
--- a/Meta/gn/secondary/Userland/Libraries/LibWeb/CSS/BUILD.gn
+++ b/Meta/gn/secondary/Userland/Libraries/LibWeb/CSS/BUILD.gn
@@ -50,6 +50,7 @@ source_set("CSS") {
     "MediaQuery.cpp",
     "MediaQueryList.cpp",
     "MediaQueryListEvent.cpp",
+    "Number.cpp",
     "ParsedFontFace.cpp",
     "PreferredColorScheme.cpp",
     "PreferredContrast.cpp",