LibWeb: Coerce NaNs to 0 when escaping top-level calculations

Author: https://github.com/gmta
Commit: https://github.com/LadybirdBrowser/ladybird/commit/6a3c3ee2911
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/4088
Reviewed-by: https://github.com/AtkinsSJ ✅

Libraries/LibWeb/CSS/StyleValues/CalculatedStyleValue.cpp

@@ -2716,9 +2716,16 @@ Optional<Time> CalculatedStyleValue::resolve_time(CalculationResolutionContext c
 Optional<double> CalculatedStyleValue::resolve_number(CalculationResolutionContext const& context) const
 {
     auto result = m_calculation->resolve(context);
-    if (result.type().has_value() && result.type()->matches_number(m_context.percentages_resolve_as))
-        return result.value();
-    return {};
+    if (!result.type().has_value() || !result.type()->matches_number(m_context.percentages_resolve_as))
+        return {};
+
+    // https://drafts.csswg.org/css-values/#calc-ieee
+    // NaN does not escape a top-level calculation; it’s censored into a zero value.
+    auto value = result.value();
+    if (isnan(value))
+        return 0.;
+
+    return value;
 }
 
 Optional<i64> CalculatedStyleValue::resolve_integer(CalculationResolutionContext const& context) const

Tests/LibWeb/Text/expected/css/getComputedStyle-transform.txt

@@ -12,6 +12,7 @@ scale(1, 2) => matrix(1, 0, 0, 2, 0, 0)
 scale(100%, 200%) => matrix(1, 0, 0, 2, 0, 0)
 scale(calc(1 / 2)) => matrix(0.5, 0, 0, 0.5, 0, 0)
 scale(calc(50% + 25%)) => matrix(0.75, 0, 0, 0.75, 0, 0)
+scale(calc(NaN)) => matrix(0, 0, 0, 0, 0, 0)
 scaleX(2) => matrix(2, 0, 0, 1, 0, 0)
 scaleX(200%) => matrix(2, 0, 0, 1, 0, 0)
 scaleY(2.5) => matrix(1, 0, 0, 2.5, 0, 0)

Tests/LibWeb/Text/input/css/getComputedStyle-transform.html

@@ -25,6 +25,7 @@
             "scale(100%, 200%)",
             "scale(calc(1 / 2))",
             "scale(calc(50% + 25%))",
+            "scale(calc(NaN))",
             "scaleX(2)",
             "scaleX(200%)",
             "scaleY(2.5)",