LibWeb: Introduce CalculatedOr type

This is intended as a replacement for Length and friends each holding a
`RefPtr<CalculatedStyleValue>`. Instead, let's make the types explicit
about whether they are calculated or not. This then means a Length is
always a Length, and won't require including `StyleValue.h`.

As noted, it's probably nicer for LengthOrCalculated to live in
`Length.h`, but we can't do that until Length stops including
`StyleValue.h`.

5 files changed, 206 insertions, 4 deletions

diff --git a/Userland/Libraries/LibWeb/CMakeLists.txt b/Userland/Libraries/LibWeb/CMakeLists.txt
index b4fb86ac21..2cd4effbcf 100644
--- a/Userland/Libraries/LibWeb/CMakeLists.txt
+++ b/Userland/Libraries/LibWeb/CMakeLists.txt
@@ -16,6 +16,7 @@ set(SOURCES
     Crypto/Crypto.cpp
     Crypto/SubtleCrypto.cpp
     CSS/Angle.cpp
+    CSS/CalculatedOr.cpp
     CSS/Clip.cpp
     CSS/CSS.cpp
     CSS/CSSConditionRule.cpp
diff --git a/Userland/Libraries/LibWeb/CSS/CalculatedOr.cpp b/Userland/Libraries/LibWeb/CSS/CalculatedOr.cpp
new file mode 100644
index 0000000000..ed01f47a68
--- /dev/null
+++ b/Userland/Libraries/LibWeb/CSS/CalculatedOr.cpp
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2023, Sam Atkins <atkinssj@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "CalculatedOr.h"
+
+namespace Web::CSS {
+
+Angle AngleOrCalculated::resolve_calculated(NonnullRefPtr<CalculatedStyleValue> const& calculated, Layout::Node const&) const
+{
+    return calculated->resolve_angle().value();
+}
+
+Frequency FrequencyOrCalculated::resolve_calculated(NonnullRefPtr<CalculatedStyleValue> const& calculated, Layout::Node const&) const
+{
+    return calculated->resolve_frequency().value();
+}
+
+Length LengthOrCalculated::resolve_calculated(NonnullRefPtr<CalculatedStyleValue> const& calculated, Layout::Node const& layout_node) const
+{
+    return calculated->resolve_length(layout_node).value();
+}
+
+Percentage PercentageOrCalculated::resolve_calculated(NonnullRefPtr<CalculatedStyleValue> const& calculated, Layout::Node const&) const
+{
+    return calculated->resolve_percentage().value();
+}
+
+Time TimeOrCalculated::resolve_calculated(NonnullRefPtr<CalculatedStyleValue> const& calculated, Layout::Node const&) const
+{
+    return calculated->resolve_time().value();
+}
+
+}
diff --git a/Userland/Libraries/LibWeb/CSS/CalculatedOr.h b/Userland/Libraries/LibWeb/CSS/CalculatedOr.h
new file mode 100644
index 0000000000..f64e879476
--- /dev/null
+++ b/Userland/Libraries/LibWeb/CSS/CalculatedOr.h
@@ -0,0 +1,155 @@
+/*
+ * Copyright (c) 2023, Sam Atkins <atkinssj@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Variant.h>
+#include <LibWeb/CSS/Angle.h>
+#include <LibWeb/CSS/Frequency.h>
+#include <LibWeb/CSS/Length.h>
+#include <LibWeb/CSS/Percentage.h>
+#include <LibWeb/CSS/StyleValue.h>
+#include <LibWeb/CSS/Time.h>
+
+namespace Web::CSS {
+
+template<typename T>
+class CalculatedOr {
+public:
+    CalculatedOr(T t)
+        : m_value(move(t))
+    {
+    }
+
+    CalculatedOr(NonnullRefPtr<CalculatedStyleValue> calculated)
+        : m_value(move(calculated))
+    {
+    }
+
+    virtual ~CalculatedOr() = default;
+
+    bool is_calculated() const { return m_value.template has<NonnullRefPtr<CalculatedStyleValue>>(); }
+
+    T const& value() const
+    {
+        VERIFY(!is_calculated());
+        return m_value.template get<T>();
+    }
+
+    NonnullRefPtr<CalculatedStyleValue> const& calculated() const
+    {
+        VERIFY(is_calculated());
+        return m_value.template get<NonnullRefPtr<CalculatedStyleValue>>();
+    }
+
+    virtual T resolve_calculated(NonnullRefPtr<CalculatedStyleValue> const&, Layout::Node const&) const = 0;
+
+    T resolved(Layout::Node const& layout_node) const
+    {
+        return m_value.visit(
+            [&](T const& t) {
+                return t;
+            },
+            [&](NonnullRefPtr<CalculatedStyleValue> const& calculated) {
+                return resolve_calculated(calculated, layout_node);
+            });
+    }
+
+    ErrorOr<String> to_string() const
+    {
+        if (is_calculated())
+            return m_value.template get<NonnullRefPtr<CalculatedStyleValue>>()->to_string();
+
+        return m_value.template get<T>().to_string();
+    }
+
+    bool operator==(CalculatedOr<T> const& other) const
+    {
+        if (is_calculated() || other.is_calculated())
+            return false;
+        return (m_value.template get<T>() == other.m_value.template get<T>());
+    }
+
+private:
+    Variant<T, NonnullRefPtr<CalculatedStyleValue>> m_value;
+};
+
+class AngleOrCalculated : public CalculatedOr<Angle> {
+public:
+    using CalculatedOr<Angle>::CalculatedOr;
+
+    Angle resolve_calculated(NonnullRefPtr<CalculatedStyleValue> const&, Layout::Node const&) const override;
+};
+
+class FrequencyOrCalculated : public CalculatedOr<Frequency> {
+public:
+    using CalculatedOr<Frequency>::CalculatedOr;
+
+    Frequency resolve_calculated(NonnullRefPtr<CalculatedStyleValue> const&, Layout::Node const&) const override;
+};
+
+class LengthOrCalculated : public CalculatedOr<Length> {
+public:
+    using CalculatedOr<Length>::CalculatedOr;
+
+    Length resolve_calculated(NonnullRefPtr<CalculatedStyleValue> const&, Layout::Node const&) const override;
+};
+
+class PercentageOrCalculated : public CalculatedOr<Percentage> {
+public:
+    using CalculatedOr<Percentage>::CalculatedOr;
+
+    Percentage resolve_calculated(NonnullRefPtr<CalculatedStyleValue> const&, Layout::Node const&) const override;
+};
+
+class TimeOrCalculated : public CalculatedOr<Time> {
+public:
+    using CalculatedOr<Time>::CalculatedOr;
+
+    Time resolve_calculated(NonnullRefPtr<CalculatedStyleValue> const&, Layout::Node const&) const override;
+};
+
+}
+
+template<>
+struct AK::Formatter<Web::CSS::AngleOrCalculated> : Formatter<StringView> {
+    ErrorOr<void> format(FormatBuilder& builder, Web::CSS::AngleOrCalculated const& calculated_or)
+    {
+        return Formatter<StringView>::format(builder, TRY(calculated_or.to_string()));
+    }
+};
+
+template<>
+struct AK::Formatter<Web::CSS::FrequencyOrCalculated> : Formatter<StringView> {
+    ErrorOr<void> format(FormatBuilder& builder, Web::CSS::FrequencyOrCalculated const& calculated_or)
+    {
+        return Formatter<StringView>::format(builder, TRY(calculated_or.to_string()));
+    }
+};
+
+template<>
+struct AK::Formatter<Web::CSS::LengthOrCalculated> : Formatter<StringView> {
+    ErrorOr<void> format(FormatBuilder& builder, Web::CSS::LengthOrCalculated const& calculated_or)
+    {
+        return Formatter<StringView>::format(builder, TRY(calculated_or.to_string()));
+    }
+};
+
+template<>
+struct AK::Formatter<Web::CSS::PercentageOrCalculated> : Formatter<StringView> {
+    ErrorOr<void> format(FormatBuilder& builder, Web::CSS::PercentageOrCalculated const& calculated_or)
+    {
+        return Formatter<StringView>::format(builder, TRY(calculated_or.to_string()));
+    }
+};
+
+template<>
+struct AK::Formatter<Web::CSS::TimeOrCalculated> : Formatter<StringView> {
+    ErrorOr<void> format(FormatBuilder& builder, Web::CSS::TimeOrCalculated const& calculated_or)
+    {
+        return Formatter<StringView>::format(builder, TRY(calculated_or.to_string()));
+    }
+};
diff --git a/Userland/Libraries/LibWeb/CSS/Percentage.h b/Userland/Libraries/LibWeb/CSS/Percentage.h
index f49ec90777..48fbc067f9 100644
--- a/Userland/Libraries/LibWeb/CSS/Percentage.h
+++ b/Userland/Libraries/LibWeb/CSS/Percentage.h
@@ -83,8 +83,10 @@ public:
     {
         return m_value.visit(
             [&](T const& t) {
-                if (t.is_calculated())
-                    return calculated_style_value_contains_percentage(*t.calculated_style_value());
+                if constexpr (requires { t.is_calculated(); }) {
+                    if (t.is_calculated())
+                        return calculated_style_value_contains_percentage(*t.calculated_style_value());
+                }
                 return false;
             },
             [&](Percentage const&) {
@@ -116,8 +118,11 @@ public:
     {
         return m_value.visit(
             [&](T const& t) {
-                if (t.is_calculated())
-                    return resolve_calculated(t.calculated_style_value(), layout_node, reference_value);
+                if constexpr (requires { t.is_calculated(); }) {
+                    if (t.is_calculated())
+                        return resolve_calculated(t.calculated_style_value(), layout_node, reference_value);
+                }
+
                 return t;
             },
             [&](Percentage const& percentage) {
diff --git a/Userland/Libraries/LibWeb/Forward.h b/Userland/Libraries/LibWeb/Forward.h
index a5d52e689e..2d3f1a9ad7 100644
--- a/Userland/Libraries/LibWeb/Forward.h
+++ b/Userland/Libraries/LibWeb/Forward.h
@@ -28,6 +28,7 @@ namespace Web::CSS {
 class AbstractImageStyleValue;
 class Angle;
 class AnglePercentage;
+class AngleOrCalculated;
 class AngleStyleValue;
 class BackgroundRepeatStyleValue;
 class BackgroundSizeStyleValue;
@@ -61,6 +62,7 @@ class FontFace;
 class FontStyleValue;
 class Frequency;
 class FrequencyPercentage;
+class FrequencyOrCalculated;
 class FrequencyStyleValue;
 class GridAreaShorthandStyleValue;
 class GridMinMax;
@@ -79,6 +81,7 @@ class InitialStyleValue;
 class Length;
 class LengthBox;
 class LengthPercentage;
+class LengthOrCalculated;
 class LengthStyleValue;
 class LinearGradientStyleValue;
 class ListStyleStyleValue;
@@ -91,6 +94,7 @@ class Number;
 class NumericStyleValue;
 class OverflowStyleValue;
 class Percentage;
+class PercentageOrCalculated;
 class PercentageStyleValue;
 class PositionStyleValue;
 class PropertyOwningCSSStyleDeclaration;
@@ -113,6 +117,7 @@ class Supports;
 class TextDecorationStyleValue;
 class Time;
 class TimePercentage;
+class TimeOrCalculated;
 class TimeStyleValue;
 class TransformationStyleValue;
 class UnicodeRange;