LibWeb: Implement CSS `sign()`

Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp

@@ -3582,6 +3582,18 @@ ErrorOr<OwnPtr<CalculationNode>> Parser::parse_abs_function(Function const& func
     return TRY(AbsCalculationNode::create(calculation_node.release_nonnull()));
 }
 
+ErrorOr<OwnPtr<CalculationNode>> Parser::parse_sign_function(Function const& function)
+{
+    auto calculation_node = TRY(parse_a_calculation(function.values()));
+
+    if (!calculation_node) {
+        dbgln_if(CSS_PARSER_DEBUG, "sign() parameter must be a valid calculation"sv);
+        return nullptr;
+    }
+
+    return TRY(SignCalculationNode::create(calculation_node.release_nonnull()));
+}
+
 ErrorOr<RefPtr<StyleValue>> Parser::parse_dynamic_value(ComponentValue const& component_value)
 {
     if (component_value.is_function()) {
@@ -3623,6 +3635,9 @@ ErrorOr<OwnPtr<CalculationNode>> Parser::parse_a_calc_function_node(Function con
     if (function.name().equals_ignoring_ascii_case("abs"sv))
         return TRY(parse_abs_function(function));
 
+    if (function.name().equals_ignoring_ascii_case("sign"sv))
+        return TRY(parse_sign_function(function));
+
     dbgln_if(CSS_PARSER_DEBUG, "We didn't implement `{}` function yet", function.name());
     return nullptr;
 }

Userland/Libraries/LibWeb/CSS/Parser/Parser.h

@@ -294,6 +294,7 @@ private:
     ErrorOr<OwnPtr<CalculationNode>> parse_max_function(Function const&);
     ErrorOr<OwnPtr<CalculationNode>> parse_clamp_function(Function const&);
     ErrorOr<OwnPtr<CalculationNode>> parse_abs_function(Function const&);
+    ErrorOr<OwnPtr<CalculationNode>> parse_sign_function(Function const&);
     ErrorOr<RefPtr<StyleValue>> parse_dimension_value(ComponentValue const&);
     ErrorOr<RefPtr<StyleValue>> parse_integer_value(TokenStream<ComponentValue>&);
     ErrorOr<RefPtr<StyleValue>> parse_number_value(TokenStream<ComponentValue>&);

Userland/Libraries/LibWeb/CSS/StyleValues/CalculatedStyleValue.cpp

@@ -718,6 +718,65 @@ ErrorOr<void> AbsCalculationNode::dump(StringBuilder& builder, int indent) const
     return {};
 }
 
+ErrorOr<NonnullOwnPtr<SignCalculationNode>> SignCalculationNode::create(NonnullOwnPtr<CalculationNode> value)
+{
+    return adopt_nonnull_own_or_enomem(new (nothrow) SignCalculationNode(move(value)));
+}
+
+SignCalculationNode::SignCalculationNode(NonnullOwnPtr<CalculationNode> value)
+    : CalculationNode(Type::Sign)
+    , m_value(move(value))
+{
+}
+
+SignCalculationNode::~SignCalculationNode() = default;
+
+ErrorOr<String> SignCalculationNode::to_string() const
+{
+    StringBuilder builder;
+    builder.append("sign("sv);
+    builder.append(TRY(m_value->to_string()));
+    builder.append(")"sv);
+    return builder.to_string();
+}
+
+Optional<CalculatedStyleValue::ResolvedType> SignCalculationNode::resolved_type() const
+{
+    return CalculatedStyleValue::ResolvedType::Integer;
+}
+
+bool SignCalculationNode::contains_percentage() const
+{
+    return m_value->contains_percentage();
+}
+
+CalculatedStyleValue::CalculationResult SignCalculationNode::resolve(Optional<Length::ResolutionContext const&> context, CalculatedStyleValue::PercentageBasis const& percentage_basis) const
+{
+    auto node_a = m_value->resolve(context, percentage_basis);
+    auto node_a_value = resolve_value(node_a.value(), context);
+
+    if (node_a_value < 0)
+        return { Number(Number::Type::Integer, -1) };
+
+    if (node_a_value > 0)
+        return { Number(Number::Type::Integer, 1) };
+
+    return { Number(Number::Type::Integer, 0) };
+}
+
+ErrorOr<void> SignCalculationNode::for_each_child_node(Function<ErrorOr<void>(NonnullOwnPtr<CalculationNode>&)> const& callback)
+{
+    TRY(m_value->for_each_child_node(callback));
+    TRY(callback(m_value));
+    return {};
+}
+
+ErrorOr<void> SignCalculationNode::dump(StringBuilder& builder, int indent) const
+{
+    TRY(builder.try_appendff("{: >{}}SIGN: {}\n", "", indent, TRY(to_string())));
+    return {};
+}
+
 void CalculatedStyleValue::CalculationResult::add(CalculationResult const& other, Optional<Length::ResolutionContext const&> context, PercentageBasis const& percentage_basis)
 {
     add_or_subtract_internal(SumOperation::Add, other, context, percentage_basis);

Userland/Libraries/LibWeb/CSS/StyleValues/CalculatedStyleValue.h

@@ -336,4 +336,22 @@ private:
     NonnullOwnPtr<CalculationNode> m_value;
 };
 
+class SignCalculationNode final : public CalculationNode {
+public:
+    static ErrorOr<NonnullOwnPtr<SignCalculationNode>> create(NonnullOwnPtr<CalculationNode>);
+    ~SignCalculationNode();
+
+    virtual ErrorOr<String> to_string() const override;
+    virtual Optional<CalculatedStyleValue::ResolvedType> resolved_type() const override;
+    virtual bool contains_percentage() const override;
+    virtual CalculatedStyleValue::CalculationResult resolve(Optional<Length::ResolutionContext const&>, CalculatedStyleValue::PercentageBasis const&) const override;
+    virtual ErrorOr<void> for_each_child_node(Function<ErrorOr<void>(NonnullOwnPtr<CalculationNode>&)> const&) override;
+
+    virtual ErrorOr<void> dump(StringBuilder&, int indent) const override;
+
+private:
+    SignCalculationNode(NonnullOwnPtr<CalculationNode>);
+    NonnullOwnPtr<CalculationNode> m_value;
+};
+
 }