From 92bcb5a2879276961353d57a2f94774ed6bdd269 Mon Sep 17 00:00:00 2001
From: Sam Atkins <atkinssj@gmail.com>
Date: Mon, 15 Jul 2024 17:46:35 +0100
Subject: [PATCH] WIP: Counters

---
 .../Libraries/LibWeb/CSS/StyleProperties.cpp  | 13 +++++++++----
 .../Libraries/LibWeb/CSS/StyleProperties.h    |  2 +-
 .../CSS/StyleValues/CounterStyleValue.cpp     | 19 +++++++++++++++++++
 .../CSS/StyleValues/CounterStyleValue.h       |  3 +++
 Userland/Libraries/LibWeb/DOM/Element.cpp     | 11 ++++++++---
 Userland/Libraries/LibWeb/DOM/Element.h       |  1 +
 .../Libraries/LibWeb/Layout/TreeBuilder.cpp   |  2 +-
 7 files changed, 42 insertions(+), 9 deletions(-)

diff --git a/Userland/Libraries/LibWeb/CSS/StyleProperties.cpp b/Userland/Libraries/LibWeb/CSS/StyleProperties.cpp
index ebebe3f7b2240..66347e489221e 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleProperties.cpp
+++ b/Userland/Libraries/LibWeb/CSS/StyleProperties.cpp
@@ -1,6 +1,6 @@
 /*
  * Copyright (c) 2018-2023, Andreas Kling <kling@serenityos.org>
- * Copyright (c) 2021-2023, Sam Atkins <atkinssj@serenityos.org>
+ * Copyright (c) 2021-2024, Sam Atkins <atkinssj@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -11,6 +11,7 @@
 #include <LibWeb/CSS/StyleProperties.h>
 #include <LibWeb/CSS/StyleValues/AngleStyleValue.h>
 #include <LibWeb/CSS/StyleValues/ContentStyleValue.h>
+#include <LibWeb/CSS/StyleValues/CounterStyleValue.h>
 #include <LibWeb/CSS/StyleValues/DisplayStyleValue.h>
 #include <LibWeb/CSS/StyleValues/GridAutoFlowStyleValue.h>
 #include <LibWeb/CSS/StyleValues/GridTemplateAreaStyleValue.h>
@@ -646,7 +647,7 @@ Optional<CSS::Clear> StyleProperties::clear() const
     return value_id_to_clear(value->to_identifier());
 }
 
-StyleProperties::ContentDataAndQuoteNestingLevel StyleProperties::content(u32 initial_quote_nesting_level) const
+StyleProperties::ContentDataAndQuoteNestingLevel StyleProperties::content(DOM::Element& element, u32 initial_quote_nesting_level) const
 {
     auto value = property(CSS::PropertyID::Content);
     auto quotes_data = quotes();
@@ -709,8 +710,10 @@ StyleProperties::ContentDataAndQuoteNestingLevel StyleProperties::content(u32 in
                     dbgln("`{}` is not supported in `content` (yet?)", item->to_string());
                     break;
                 }
+            } else if (item->is_counter()) {
+                builder.append(item->as_counter().resolve(element.ensure_counters_set()));
             } else {
-                // TODO: Implement counters, images, and other things.
+                // TODO: Implement images, and other things.
                 dbgln("`{}` is not supported in `content` (yet?)", item->to_string());
             }
         }
@@ -722,8 +725,10 @@ StyleProperties::ContentDataAndQuoteNestingLevel StyleProperties::content(u32 in
             for (auto const& item : content_style_value.alt_text()->values()) {
                 if (item->is_string()) {
                     alt_text_builder.append(item->as_string().string_value());
+                } else if (item->is_counter()) {
+                    alt_text_builder.append(item->as_counter().resolve(element.ensure_counters_set()));
                 } else {
-                    // TODO: Implement counters
+                    dbgln("`{}` is not supported in `content` alt-text (yet?)", item->to_string());
                 }
             }
             content_data.alt_text = MUST(alt_text_builder.to_string());
diff --git a/Userland/Libraries/LibWeb/CSS/StyleProperties.h b/Userland/Libraries/LibWeb/CSS/StyleProperties.h
index cb3ae3d3c837a..16eec76cf3bc9 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleProperties.h
+++ b/Userland/Libraries/LibWeb/CSS/StyleProperties.h
@@ -85,7 +85,7 @@ class StyleProperties : public RefCounted<StyleProperties> {
         CSS::ContentData content_data;
         u32 final_quote_nesting_level { 0 };
     };
-    ContentDataAndQuoteNestingLevel content(u32 initial_quote_nesting_level) const;
+    ContentDataAndQuoteNestingLevel content(DOM::Element&, u32 initial_quote_nesting_level) const;
     Optional<CSS::Cursor> cursor() const;
     Optional<CSS::WhiteSpace> white_space() const;
     Optional<CSS::LineStyle> line_style(CSS::PropertyID) const;
diff --git a/Userland/Libraries/LibWeb/CSS/StyleValues/CounterStyleValue.cpp b/Userland/Libraries/LibWeb/CSS/StyleValues/CounterStyleValue.cpp
index adef158fa2bd9..794cbff0ed830 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleValues/CounterStyleValue.cpp
+++ b/Userland/Libraries/LibWeb/CSS/StyleValues/CounterStyleValue.cpp
@@ -22,6 +22,25 @@ CounterStyleValue::CounterStyleValue(CounterFunction function, ValueComparingNon
 
 CounterStyleValue::~CounterStyleValue() = default;
 
+String CounterStyleValue::resolve(CountersSet& counters_set) const
+{
+    // counter( <counter-name>, <counter-style>? )
+    if (m_properties.function == CounterFunction::Counter) {
+        StringBuilder stb;
+        auto counter = counters_set.last_counter_with_name(m_properties.counter_name->to_string());
+        if (!counter.has_value()) {
+            // "If no counter named <counter-name> exists on an element where counter() or counters() is used,
+            // one is first instantiated with a starting value of 0."
+            counters_set.
+        }
+
+        return stb.to_string_without_validation();
+    }
+    // counters( <counter-name>, <string>, <counter-style>? )
+    StringBuilder stb;
+    return stb.to_string_without_validation();
+}
+
 // https://drafts.csswg.org/cssom-1/#ref-for-typedef-counter
 String CounterStyleValue::to_string() const
 {
diff --git a/Userland/Libraries/LibWeb/CSS/StyleValues/CounterStyleValue.h b/Userland/Libraries/LibWeb/CSS/StyleValues/CounterStyleValue.h
index be2eea0b38673..a27e67c149479 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleValues/CounterStyleValue.h
+++ b/Userland/Libraries/LibWeb/CSS/StyleValues/CounterStyleValue.h
@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include "LibWeb/CSS/CountersSet.h"
 #include <LibWeb/CSS/StyleValue.h>
 
 namespace Web::CSS {
@@ -33,6 +34,8 @@ class CounterStyleValue : public StyleValueWithDefaultOperators<CounterStyleValu
     auto counter_style() const { return m_properties.counter_style; }
     auto join_string() const { return m_properties.join_string; }
 
+    String resolve(CountersSet&) const;
+
     virtual String to_string() const override;
 
     bool properties_equal(CounterStyleValue const& other) const;
diff --git a/Userland/Libraries/LibWeb/DOM/Element.cpp b/Userland/Libraries/LibWeb/DOM/Element.cpp
index ae9156aff3166..8b75fe717ffc7 100644
--- a/Userland/Libraries/LibWeb/DOM/Element.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Element.cpp
@@ -2671,14 +2671,19 @@ Optional<CSS::CountersSet const&> Element::counters_set()
     return *m_counters_set;
 }
 
+CSS::CountersSet& Element::ensure_counters_set()
+{
+    if (!m_counters_set)
+        m_counters_set = make<CSS::CountersSet>();
+    return *m_counters_set;
+}
+
 // https://drafts.csswg.org/css-lists-3/#instantiate-counter
 void Element::instantiate_a_counter(FlyString name, bool reversed, Optional<CSS::CounterValue> value)
 {
     // 1. Let counters be element’s CSS counters set.
     // NOTE: We use nullptr for an empty CountersSet, so must ensure it exists here.
-    if (!has_non_empty_counters_set())
-        m_counters_set = make<CSS::CountersSet>();
-    auto& counters = *m_counters_set;
+    auto& counters = ensure_counters_set();
 
     // 2. Let innermost counter be the last counter in counters with the name name.
     //    If innermost counter’s originating element is element or a previous sibling of element,
diff --git a/Userland/Libraries/LibWeb/DOM/Element.h b/Userland/Libraries/LibWeb/DOM/Element.h
index 5321a00dd4745..2a26b135e1654 100644
--- a/Userland/Libraries/LibWeb/DOM/Element.h
+++ b/Userland/Libraries/LibWeb/DOM/Element.h
@@ -393,6 +393,7 @@ class Element
 
     bool has_non_empty_counters_set() const { return m_counters_set; }
     Optional<CSS::CountersSet const&> counters_set();
+    CSS::CountersSet& ensure_counters_set();
     void instantiate_a_counter(FlyString name, bool reversed, Optional<CSS::CounterValue>);
     void inherit_counters();
 
diff --git a/Userland/Libraries/LibWeb/Layout/TreeBuilder.cpp b/Userland/Libraries/LibWeb/Layout/TreeBuilder.cpp
index 5d8126f6e9e4a..35431ed054903 100644
--- a/Userland/Libraries/LibWeb/Layout/TreeBuilder.cpp
+++ b/Userland/Libraries/LibWeb/Layout/TreeBuilder.cpp
@@ -198,7 +198,7 @@ void TreeBuilder::create_pseudo_element_if_needed(DOM::Element& element, CSS::Se
         return;
 
     auto initial_quote_nesting_level = m_quote_nesting_level;
-    auto [pseudo_element_content, final_quote_nesting_level] = pseudo_element_style->content(initial_quote_nesting_level);
+    auto [pseudo_element_content, final_quote_nesting_level] = pseudo_element_style->content(element, initial_quote_nesting_level);
     m_quote_nesting_level = final_quote_nesting_level;
     auto pseudo_element_display = pseudo_element_style->display();
     // ::before and ::after only exist if they have content. `content: normal` computes to `none` for them.