LibWeb: Implement CSS mod()

Author: https://github.com/stelar7
Commit: https://github.com/SerenityOS/serenity/commit/dc042662d1
Pull-request: https://github.com/SerenityOS/serenity/pull/19159
Reviewed-by: https://github.com/AtkinsSJ ✅

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

@@ -4031,6 +4031,46 @@ ErrorOr<OwnPtr<CalculationNode>> Parser::parse_round_function(Function const& fu
     return TRY(RoundCalculationNode::create(mode, node_a.release_nonnull(), node_b.release_nonnull()));
 }
 
+ErrorOr<OwnPtr<CalculationNode>> Parser::parse_mod_function(Function const& function)
+{
+    TokenStream stream { function.values() };
+    auto parameters = parse_a_comma_separated_list_of_component_values(stream);
+
+    if (parameters.size() != 2) {
+        dbgln_if(CSS_PARSER_DEBUG, "mod() must have exactly two parameters"sv);
+        return nullptr;
+    }
+
+    auto node_a = TRY(parse_a_calculation(parameters[0]));
+    auto node_b = TRY(parse_a_calculation(parameters[1]));
+
+    if (!node_a || !node_b) {
+        dbgln_if(CSS_PARSER_DEBUG, "mod() parameters must be valid calculations"sv);
+        return nullptr;
+    }
+
+    auto node_a_maybe_parameter_type = node_a->resolved_type();
+    if (!node_a_maybe_parameter_type.has_value()) {
+        dbgln_if(CSS_PARSER_DEBUG, "Failed to resolve type for mod() parameter 1"sv);
+        return nullptr;
+    }
+
+    auto node_b_maybe_parameter_type = node_b->resolved_type();
+    if (!node_b_maybe_parameter_type.has_value()) {
+        dbgln_if(CSS_PARSER_DEBUG, "Failed to resolve type for mod() parameter 2"sv);
+        return nullptr;
+    }
+
+    auto node_a_resolved_type = node_a_maybe_parameter_type.value();
+    auto node_b_resolved_type = node_b_maybe_parameter_type.value();
+    if (node_a_resolved_type != node_b_resolved_type) {
+        dbgln_if(CSS_PARSER_DEBUG, "mod() parameters must all be of the same type"sv);
+        return nullptr;
+    }
+
+    return TRY(ModCalculationNode::create(node_a.release_nonnull(), node_b.release_nonnull()));
+}
+
 ErrorOr<RefPtr<StyleValue>> Parser::parse_dynamic_value(ComponentValue const& component_value)
 {
     if (component_value.is_function()) {
@@ -4114,6 +4154,9 @@ ErrorOr<OwnPtr<CalculationNode>> Parser::parse_a_calc_function_node(Function con
     if (function.name().equals_ignoring_ascii_case("round"sv))
         return TRY(parse_round_function(function));
 
+    if (function.name().equals_ignoring_ascii_case("mod"sv))
+        return TRY(parse_mod_function(function));
+
     dbgln_if(CSS_PARSER_DEBUG, "We didn't implement `{}` function yet", function.name());
     return nullptr;
 }

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

@@ -308,6 +308,7 @@ private:
     ErrorOr<OwnPtr<CalculationNode>> parse_log_function(Function const&);
     ErrorOr<OwnPtr<CalculationNode>> parse_exp_function(Function const&);
     ErrorOr<OwnPtr<CalculationNode>> parse_round_function(Function const&);
+    ErrorOr<OwnPtr<CalculationNode>> parse_mod_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

@@ -1631,6 +1631,71 @@ ErrorOr<void> RoundCalculationNode::dump(StringBuilder& builder, int indent) con
     return {};
 }
 
+ErrorOr<NonnullOwnPtr<ModCalculationNode>> ModCalculationNode::create(NonnullOwnPtr<CalculationNode> x, NonnullOwnPtr<CalculationNode> y)
+{
+    return adopt_nonnull_own_or_enomem(new (nothrow) ModCalculationNode(move(x), move(y)));
+}
+
+ModCalculationNode::ModCalculationNode(NonnullOwnPtr<CalculationNode> x, NonnullOwnPtr<CalculationNode> y)
+    : CalculationNode(Type::Mod)
+    , m_x(move(x))
+    , m_y(move(y))
+{
+}
+
+ModCalculationNode::~ModCalculationNode() = default;
+
+ErrorOr<String> ModCalculationNode::to_string() const
+{
+    StringBuilder builder;
+    builder.append("mod("sv);
+    builder.append(TRY(m_x->to_string()));
+    builder.append(", "sv);
+    builder.append(TRY(m_y->to_string()));
+    builder.append(")"sv);
+    return builder.to_string();
+}
+
+Optional<CalculatedStyleValue::ResolvedType> ModCalculationNode::resolved_type() const
+{
+    // Note: We check during parsing that all values have the same type
+    return m_x->resolved_type();
+}
+
+bool ModCalculationNode::contains_percentage() const
+{
+    return m_x->contains_percentage() || m_y->contains_percentage();
+}
+
+CalculatedStyleValue::CalculationResult ModCalculationNode::resolve(Optional<Length::ResolutionContext const&> context, CalculatedStyleValue::PercentageBasis const& percentage_basis) const
+{
+    auto resolved_type = m_x->resolved_type().value();
+    auto node_a = m_x->resolve(context, percentage_basis);
+    auto node_b = m_y->resolve(context, percentage_basis);
+
+    auto node_a_value = resolve_value(node_a.value(), context);
+    auto node_b_value = resolve_value(node_b.value(), context);
+
+    auto quotient = floor(node_a_value / node_b_value);
+    auto value = node_a_value - (node_b_value * quotient);
+    return to_resolved_type(resolved_type, value);
+}
+
+ErrorOr<void> ModCalculationNode::for_each_child_node(Function<ErrorOr<void>(NonnullOwnPtr<CalculationNode>&)> const& callback)
+{
+    TRY(m_x->for_each_child_node(callback));
+    TRY(m_y->for_each_child_node(callback));
+    TRY(callback(m_x));
+    TRY(callback(m_y));
+    return {};
+}
+
+ErrorOr<void> ModCalculationNode::dump(StringBuilder& builder, int indent) const
+{
+    TRY(builder.try_appendff("{: >{}}MOD: {}\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

@@ -657,4 +657,23 @@ private:
     NonnullOwnPtr<CalculationNode> m_y;
 };
 
+class ModCalculationNode final : public CalculationNode {
+public:
+    static ErrorOr<NonnullOwnPtr<ModCalculationNode>> create(NonnullOwnPtr<CalculationNode>, NonnullOwnPtr<CalculationNode>);
+    ~ModCalculationNode();
+
+    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:
+    ModCalculationNode(NonnullOwnPtr<CalculationNode>, NonnullOwnPtr<CalculationNode>);
+    NonnullOwnPtr<CalculationNode> m_x;
+    NonnullOwnPtr<CalculationNode> m_y;
+};
+
 }