From e5d03e382e077c2de0950655c8896100c2d8f444 Mon Sep 17 00:00:00 2001
From: Shannon Booth <shannon@serenityos.org>
Date: Sat, 4 May 2024 12:39:45 +1200
Subject: [PATCH] LibWeb: Add AO for "normalize non-finite values"

We had implemented this in two different ways. Add an AO to to align the
implementations.
---
 Userland/Libraries/LibWeb/DOM/Element.cpp     |  6 ++----
 .../Libraries/LibWeb/HTML/ScrollOptions.h     | 19 +++++++++++++++++++
 Userland/Libraries/LibWeb/HTML/Window.cpp     | 14 ++++++--------
 3 files changed, 27 insertions(+), 12 deletions(-)

diff --git a/Userland/Libraries/LibWeb/DOM/Element.cpp b/Userland/Libraries/LibWeb/DOM/Element.cpp
index f50bb78476d..f1d20ced501 100644
--- a/Userland/Libraries/LibWeb/DOM/Element.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Element.cpp
@@ -1208,8 +1208,7 @@ void Element::set_scroll_left(double x)
     // 1. Let x be the given value.
 
     // 2. Normalize non-finite values for x.
-    if (!isfinite(x))
-        x = 0.0;
+    x = HTML::normalize_non_finite_values(x);
 
     // 3. Let document be the element’s node document.
     auto& document = this->document();
@@ -1265,8 +1264,7 @@ void Element::set_scroll_top(double y)
     // 1. Let y be the given value.
 
     // 2. Normalize non-finite values for y.
-    if (!isfinite(y))
-        y = 0.0;
+    y = HTML::normalize_non_finite_values(y);
 
     // 3. Let document be the element’s node document.
     auto& document = this->document();
diff --git a/Userland/Libraries/LibWeb/HTML/ScrollOptions.h b/Userland/Libraries/LibWeb/HTML/ScrollOptions.h
index 288659f4fde..7a7249831ae 100644
--- a/Userland/Libraries/LibWeb/HTML/ScrollOptions.h
+++ b/Userland/Libraries/LibWeb/HTML/ScrollOptions.h
@@ -15,4 +15,23 @@ struct ScrollOptions {
     Bindings::ScrollBehavior behavior { Bindings::ScrollBehavior::Auto };
 };
 
+// https://drafts.csswg.org/cssom-view/#normalize-non-finite-values
+[[nodiscard]] inline double normalize_non_finite_values(double value)
+{
+    // When asked to normalize non-finite values for a value x, if x is one of the three special floating point
+    // literal values (Infinity, -Infinity or NaN), then x must be changed to the value 0. [WEBIDL]
+    if (isinf(value) || isnan(value))
+        return 0;
+
+    return value;
+}
+
+// https://drafts.csswg.org/cssom-view/#normalize-non-finite-values
+[[nodiscard]] inline double normalize_non_finite_values(Optional<double> const& value)
+{
+    if (!value.has_value())
+        return 0;
+    return normalize_non_finite_values(value.value());
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/HTML/Window.cpp b/Userland/Libraries/LibWeb/HTML/Window.cpp
index 89b059d6b7b..ade57e9c210 100644
--- a/Userland/Libraries/LibWeb/HTML/Window.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Window.cpp
@@ -1368,8 +1368,8 @@ void Window::scroll(ScrollToOptions const& options)
     auto y = options.top.value_or(viewport_rect.y());
 
     // 3. Normalize non-finite values for x and y.
-    x = JS::Value(x).is_finite_number() ? x : 0;
-    y = JS::Value(y).is_finite_number() ? y : 0;
+    x = HTML::normalize_non_finite_values(x);
+    y = HTML::normalize_non_finite_values(y);
 
     // 5. Let viewport width be the width of the viewport excluding the width of the scroll bar, if any.
     auto viewport_width = viewport_rect.width();
@@ -1438,16 +1438,14 @@ void Window::scroll(double x, double y)
 void Window::scroll_by(ScrollToOptions options)
 {
     // 2. Normalize non-finite values for the left and top dictionary members of options.
-    auto x = options.left.value_or(0);
-    auto y = options.top.value_or(0);
-    x = JS::Value(x).is_finite_number() ? x : 0;
-    y = JS::Value(y).is_finite_number() ? y : 0;
+    auto left = HTML::normalize_non_finite_values(options.left);
+    auto top = HTML::normalize_non_finite_values(options.top);
 
     // 3. Add the value of scrollX to the left dictionary member.
-    options.left = x + scroll_x();
+    options.left = left + scroll_x();
 
     // 4. Add the value of scrollY to the top dictionary member.
-    options.top = y + scroll_y();
+    options.top = top + scroll_y();
 
     // 5. Act as if the scroll() method was invoked with options as the only argument.
     scroll(options);