LibWeb: Implement CounterStyleValue

This is `counter(name, style?)` or `counters(name, link, style?)`. The
difference being, `counter()` matches only the nearest level (eg, "1"),
and `counters()` combines all the levels in the tree (eg, "3.4.1").

Meta/Lagom/Tools/CodeGenerators/LibWeb/GenerateCSSPropertyID.cpp

@@ -22,9 +22,28 @@ bool is_animatable_property(JsonObject& properties, StringView property_name);
 static bool type_name_is_enum(StringView type_name)
 {
     return !AK::first_is_one_of(type_name,
-        "angle"sv, "background-position"sv, "basic-shape"sv, "color"sv, "custom-ident"sv, "easing-function"sv, "flex"sv, "frequency"sv, "image"sv,
-        "integer"sv, "length"sv, "number"sv, "paint"sv, "percentage"sv, "position"sv, "ratio"sv, "rect"sv,
-        "resolution"sv, "string"sv, "time"sv, "url"sv);
+        "angle"sv,
+        "background-position"sv,
+        "basic-shape"sv,
+        "color"sv,
+        "counter"sv,
+        "custom-ident"sv,
+        "easing-function"sv,
+        "flex"sv,
+        "frequency"sv,
+        "image"sv,
+        "integer"sv,
+        "length"sv,
+        "number"sv,
+        "paint"sv,
+        "percentage"sv,
+        "position"sv,
+        "ratio"sv,
+        "rect"sv,
+        "resolution"sv,
+        "string"sv,
+        "time"sv,
+        "url"sv);
 }
 
 ErrorOr<int> serenity_main(Main::Arguments arguments)
@@ -183,6 +202,7 @@ enum class ValueType {
     BackgroundPosition,
     BasicShape,
     Color,
+    Counter,
     CustomIdent,
     EasingFunction,
     FilterValueList,
@@ -732,6 +752,8 @@ bool property_accepts_type(PropertyID property_id, ValueType value_type)
                     property_generator.appendln("        case ValueType::BasicShape:");
                 } else if (type_name == "color") {
                     property_generator.appendln("        case ValueType::Color:");
+                } else if (type_name == "counter") {
+                    property_generator.appendln("        case ValueType::Counter:");
                 } else if (type_name == "custom-ident") {
                     property_generator.appendln("        case ValueType::CustomIdent:");
                 } else if (type_name == "easing-function") {

Userland/Libraries/LibWeb/CMakeLists.txt

@@ -111,6 +111,7 @@ set(SOURCES
     CSS/StyleValues/ConicGradientStyleValue.cpp
     CSS/StyleValues/ContentStyleValue.cpp
     CSS/StyleValues/CounterDefinitionsStyleValue.cpp
+    CSS/StyleValues/CounterStyleValue.cpp
     CSS/StyleValues/DisplayStyleValue.cpp
     CSS/StyleValues/EasingStyleValue.cpp
     CSS/StyleValues/EdgeStyleValue.cpp

Userland/Libraries/LibWeb/CSS/CSSNumericType.cpp

@@ -36,6 +36,7 @@ Optional<CSSNumericType::BaseType> CSSNumericType::base_type_from_value_type(Val
     case ValueType::BackgroundPosition:
     case ValueType::BasicShape:
     case ValueType::Color:
+    case ValueType::Counter:
     case ValueType::CustomIdent:
     case ValueType::EasingFunction:
     case ValueType::FilterValueList:

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

@@ -45,6 +45,7 @@
 #include <LibWeb/CSS/StyleValues/ColorStyleValue.h>
 #include <LibWeb/CSS/StyleValues/ContentStyleValue.h>
 #include <LibWeb/CSS/StyleValues/CounterDefinitionsStyleValue.h>
+#include <LibWeb/CSS/StyleValues/CounterStyleValue.h>
 #include <LibWeb/CSS/StyleValues/CustomIdentStyleValue.h>
 #include <LibWeb/CSS/StyleValues/DisplayStyleValue.h>
 #include <LibWeb/CSS/StyleValues/EasingStyleValue.h>
@@ -2892,6 +2893,118 @@ RefPtr<StyleValue> Parser::parse_color_value(TokenStream<ComponentValue>& tokens
     return nullptr;
 }
 
+// https://drafts.csswg.org/css-lists-3/#counter-functions
+RefPtr<StyleValue> Parser::parse_counter_value(TokenStream<ComponentValue>& tokens)
+{
+    auto parse_counter_name = [](TokenStream<ComponentValue>& tokens) -> Optional<FlyString> {
+        // https://drafts.csswg.org/css-lists-3/#typedef-counter-name
+        // Counters are referred to in CSS syntax using the <counter-name> type, which represents
+        // their name as a <custom-ident>. A <counter-name> name cannot match the keyword none;
+        // such an identifier is invalid as a <counter-name>.
+        auto transaction = tokens.begin_transaction();
+        tokens.skip_whitespace();
+
+        auto& token = tokens.next_token();
+        if (!token.is(Token::Type::Ident) || token.token().ident() == "none"sv)
+            return {};
+
+        tokens.skip_whitespace();
+        if (tokens.has_next_token())
+            return {};
+
+        transaction.commit();
+        return token.token().ident();
+    };
+
+    auto parse_counter_style = [](TokenStream<ComponentValue>& tokens) -> RefPtr<StyleValue> {
+        // https://drafts.csswg.org/css-counter-styles-3/#typedef-counter-style
+        // <counter-style> = <counter-style-name> | <symbols()>
+        // For now we just support <counter-style-name>, found here:
+        // https://drafts.csswg.org/css-counter-styles-3/#typedef-counter-style-name
+        // <counter-style-name> is a <custom-ident> that is not an ASCII case-insensitive match for none.
+        auto transaction = tokens.begin_transaction();
+        tokens.skip_whitespace();
+
+        auto& token = tokens.next_token();
+        if (!token.is(Token::Type::Ident) || token.token().ident() == "none"sv)
+            return {};
+
+        tokens.skip_whitespace();
+        if (tokens.has_next_token())
+            return {};
+
+        transaction.commit();
+        return CustomIdentStyleValue::create(token.token().ident());
+    };
+
+    auto transaction = tokens.begin_transaction();
+    auto token = tokens.next_token();
+    if (token.is_function("counter"sv)) {
+        // counter() = counter( <counter-name>, <counter-style>? )
+        auto& function = token.function();
+        TokenStream function_tokens { function.values() };
+        auto function_values = parse_a_comma_separated_list_of_component_values(function_tokens);
+        if (function_values.is_empty() || function_values.size() > 2)
+            return nullptr;
+
+        TokenStream name_tokens { function_values[0] };
+        auto counter_name = parse_counter_name(name_tokens);
+        if (!counter_name.has_value())
+            return nullptr;
+
+        RefPtr<StyleValue> counter_style;
+        if (function_values.size() > 1) {
+            TokenStream counter_style_tokens { function_values[1] };
+            counter_style = parse_counter_style(counter_style_tokens);
+            if (!counter_style)
+                return nullptr;
+        } else {
+            // In both cases, if the <counter-style> argument is omitted it defaults to `decimal`.
+            counter_style = CustomIdentStyleValue::create("decimal"_fly_string);
+        }
+
+        transaction.commit();
+        return CounterStyleValue::create_counter(counter_name.release_value(), counter_style.release_nonnull());
+    }
+
+    if (token.is_function("counters"sv)) {
+        // counters() = counters( <counter-name>, <string>, <counter-style>? )
+        auto& function = token.function();
+        TokenStream function_tokens { function.values() };
+        auto function_values = parse_a_comma_separated_list_of_component_values(function_tokens);
+        if (function_values.is_empty() || function_values.size() > 3)
+            return nullptr;
+
+        TokenStream name_tokens { function_values[0] };
+        auto counter_name = parse_counter_name(name_tokens);
+        if (!counter_name.has_value())
+            return nullptr;
+
+        TokenStream string_tokens { function_values[1] };
+        string_tokens.skip_whitespace();
+        RefPtr<StyleValue> join_string = parse_string_value(string_tokens);
+        string_tokens.skip_whitespace();
+        if (!join_string || string_tokens.has_next_token())
+            return nullptr;
+
+        RefPtr<StyleValue> counter_style;
+        if (function_values.size() > 2) {
+            TokenStream counter_style_tokens { function_values[2] };
+            counter_style = parse_counter_style(counter_style_tokens);
+            if (!counter_style)
+                return nullptr;
+        } else {
+            // In both cases, if the <counter-style> argument is omitted it defaults to `decimal`.
+            counter_style = CustomIdentStyleValue::create("decimal"_fly_string);
+        }
+
+        transaction.commit();
+        return CounterStyleValue::create_counters(counter_name.release_value(), join_string->as_string().string_value(), counter_style.release_nonnull());
+    }
+
+    return nullptr;
+}
+
 RefPtr<StyleValue> Parser::parse_counter_definitions_value(TokenStream<ComponentValue>& tokens, AllowReversed allow_reversed, i32 default_value_if_not_reversed)
 {
     // If AllowReversed is Yes, parses:
@@ -7141,6 +7254,11 @@ Optional<Parser::PropertyAndValue> Parser::parse_css_value_for_properties(Readon
             return PropertyAndValue { *property, maybe_color };
     }
 
+    if (auto property = any_property_accepts_type(property_ids, ValueType::Counter); property.has_value()) {
+        if (auto maybe_counter = parse_counter_value(tokens))
+            return PropertyAndValue { *property, maybe_counter };
+    }
+
     if (auto property = any_property_accepts_type(property_ids, ValueType::Image); property.has_value()) {
         if (auto maybe_image = parse_image_value(tokens))
             return PropertyAndValue { *property, maybe_image };

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

@@ -288,6 +288,7 @@ private:
     RefPtr<StyleValue> parse_number_or_percentage_value(TokenStream<ComponentValue>&);
     RefPtr<StyleValue> parse_identifier_value(TokenStream<ComponentValue>&);
     RefPtr<StyleValue> parse_color_value(TokenStream<ComponentValue>&);
+    RefPtr<StyleValue> parse_counter_value(TokenStream<ComponentValue>&);
     enum class AllowReversed {
         No,
         Yes,

Userland/Libraries/LibWeb/CSS/Properties.json

@@ -966,6 +966,7 @@
     "initial": "normal",
     "__comment": "FIXME: This accepts a whole lot of other types and identifiers!",
     "valid-types": [
+      "counter",
       "string"
     ],
     "valid-identifiers": [

Userland/Libraries/LibWeb/CSS/StyleValue.cpp

@@ -21,6 +21,7 @@
 #include <LibWeb/CSS/StyleValues/ConicGradientStyleValue.h>
 #include <LibWeb/CSS/StyleValues/ContentStyleValue.h>
 #include <LibWeb/CSS/StyleValues/CounterDefinitionsStyleValue.h>
+#include <LibWeb/CSS/StyleValues/CounterStyleValue.h>
 #include <LibWeb/CSS/StyleValues/CustomIdentStyleValue.h>
 #include <LibWeb/CSS/StyleValues/DisplayStyleValue.h>
 #include <LibWeb/CSS/StyleValues/EasingStyleValue.h>

Userland/Libraries/LibWeb/CSS/StyleValue.h

@@ -92,6 +92,7 @@ using StyleValueVector = Vector<ValueComparingNonnullRefPtr<StyleValue const>>;
     __ENUMERATE_STYLE_VALUE_TYPE(Color, color)                             \
     __ENUMERATE_STYLE_VALUE_TYPE(ConicGradient, conic_gradient)            \
     __ENUMERATE_STYLE_VALUE_TYPE(Content, content)                         \
+    __ENUMERATE_STYLE_VALUE_TYPE(Counter, counter)                         \
     __ENUMERATE_STYLE_VALUE_TYPE(CounterDefinitions, counter_definitions)  \
     __ENUMERATE_STYLE_VALUE_TYPE(CustomIdent, custom_ident)                \
     __ENUMERATE_STYLE_VALUE_TYPE(Display, display)                         \

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

@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2024, Sam Atkins <sam@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "CounterStyleValue.h"
+#include <LibWeb/CSS/Serialize.h>
+#include <LibWeb/CSS/StyleValues/CustomIdentStyleValue.h>
+#include <LibWeb/CSS/StyleValues/StringStyleValue.h>
+
+namespace Web::CSS {
+
+CounterStyleValue::CounterStyleValue(CounterFunction function, FlyString counter_name, ValueComparingNonnullRefPtr<StyleValue const> counter_style, FlyString join_string)
+    : StyleValueWithDefaultOperators(Type::Counter)
+    , m_properties {
+        .function = function,
+        .counter_name = move(counter_name),
+        .counter_style = move(counter_style),
+        .join_string = move(join_string)
+    }
+{
+}
+
+CounterStyleValue::~CounterStyleValue() = default;
+
+// https://drafts.csswg.org/cssom-1/#ref-for-typedef-counter
+String CounterStyleValue::to_string() const
+{
+    // The return value of the following algorithm:
+    // 1. Let s be the empty string.
+    StringBuilder s;
+
+    // 2. If <counter> has three CSS component values append the string "counters(" to s.
+    if (m_properties.function == CounterFunction::Counters)
+        s.append("counters("sv);
+
+    // 3. If <counter> has two CSS component values append the string "counter(" to s.
+    else if (m_properties.function == CounterFunction::Counter)
+        s.append("counter("sv);
+
+    // 4. Let list be a list of CSS component values belonging to <counter>,
+    //    omitting the last CSS component value if it is "decimal".
+    Vector<RefPtr<StyleValue const>> list;
+    list.append(CustomIdentStyleValue::create(m_properties.counter_name));
+    if (m_properties.function == CounterFunction::Counters)
+        list.append(StringStyleValue::create(m_properties.join_string.to_string()));
+    if (m_properties.counter_style->to_identifier() != ValueID::Decimal)
+        list.append(m_properties.counter_style);
+
+    // 5. Let each item in list be the result of invoking serialize a CSS component value on that item.
+    // 6. Append the result of invoking serialize a comma-separated list on list to s.
+    serialize_a_comma_separated_list(s, list, [](auto& builder, auto& item) {
+        builder.append(item->to_string());
+    });
+
+    // 7. Append ")" (U+0029) to s.
+    s.append(")"sv);
+
+    // 8. Return s.
+    return MUST(s.to_string());
+}
+
+bool CounterStyleValue::properties_equal(CounterStyleValue const& other) const
+{
+    return m_properties == other.m_properties;
+}
+
+}

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

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2024, Sam Atkins <sam@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/FlyString.h>
+#include <LibWeb/CSS/StyleValue.h>
+
+namespace Web::CSS {
+
+// https://drafts.csswg.org/css-lists-3/#counter-functions
+class CounterStyleValue : public StyleValueWithDefaultOperators<CounterStyleValue> {
+public:
+    enum class CounterFunction {
+        Counter,
+        Counters,
+    };
+
+    static ValueComparingNonnullRefPtr<CounterStyleValue> create_counter(FlyString counter_name, ValueComparingNonnullRefPtr<StyleValue const> counter_style)
+    {
+        return adopt_ref(*new (nothrow) CounterStyleValue(CounterFunction::Counter, move(counter_name), move(counter_style), {}));
+    }
+    static ValueComparingNonnullRefPtr<CounterStyleValue> create_counters(FlyString counter_name, FlyString join_string, ValueComparingNonnullRefPtr<StyleValue const> counter_style)
+    {
+        return adopt_ref(*new (nothrow) CounterStyleValue(CounterFunction::Counters, move(counter_name), move(counter_style), move(join_string)));
+    }
+    virtual ~CounterStyleValue() override;
+
+    CounterFunction function_type() const { return m_properties.function; }
+    auto counter_name() const { return m_properties.counter_name; }
+    auto counter_style() const { return m_properties.counter_style; }
+    auto join_string() const { return m_properties.join_string; }
+
+    String resolve(DOM::Element&) const;
+
+    virtual String to_string() const override;
+
+    bool properties_equal(CounterStyleValue const& other) const;
+
+private:
+    explicit CounterStyleValue(CounterFunction, FlyString counter_name, ValueComparingNonnullRefPtr<StyleValue const> counter_style, FlyString join_string);
+
+    struct Properties {
+        CounterFunction function;
+        FlyString counter_name;
+        ValueComparingNonnullRefPtr<StyleValue const> counter_style;
+        FlyString join_string;
+        bool operator==(Properties const&) const = default;
+    } m_properties;
+};
+
+}

Userland/Libraries/LibWeb/Forward.h

@@ -120,6 +120,7 @@ class Clip;
 class ColorStyleValue;
 class ConicGradientStyleValue;
 class ContentStyleValue;
+class CounterStyleValue;
 class CounterDefinitionsStyleValue;
 class CustomIdentStyleValue;
 class Display;