LibWeb: Parse oblique font-style with an angle value

Author: https://github.com/tcl3
Commit: c0f9b11070
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/4552
Reviewed-by: https://github.com/konradekk

Libraries/LibWeb/CSS/StyleValues/FontStyleStyleValue.cpp

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2025, Tim Ledbetter <tim.ledbetter@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "FontStyleStyleValue.h"
+#include <LibWeb/CSS/CSSStyleValue.h>
+#include <LibWeb/CSS/Serialize.h>
+#include <LibWeb/CSS/StyleValues/AngleStyleValue.h>
+
+namespace Web::CSS {
+
+FontStyleStyleValue::FontStyleStyleValue(FontStyle font_style, ValueComparingRefPtr<CSSStyleValue const> angle_value)
+    : StyleValueWithDefaultOperators(Type::FontStyle)
+    , m_font_style(font_style)
+    , m_angle_value(angle_value)
+{
+}
+
+FontStyleStyleValue::~FontStyleStyleValue() = default;
+
+String FontStyleStyleValue::to_string(SerializationMode mode) const
+{
+    Optional<String> angle_string;
+    if (m_angle_value) {
+        angle_string = m_angle_value->to_string(mode);
+        if (m_font_style == FontStyle::Oblique && angle_string == "0deg"sv)
+            return "normal"_string;
+    }
+    StringBuilder builder;
+    builder.append(CSS::to_string(m_font_style));
+    // https://drafts.csswg.org/css-fonts/#valdef-font-style-oblique-angle--90deg-90deg
+    // The lack of an <angle> represents 14deg. (Note that a font might internally provide its own mapping for "oblique", but the mapping within the font is disregarded.)
+    static auto default_angle = Angle::make_degrees(14);
+    if (angle_string.has_value() && !(m_angle_value->is_angle() && m_angle_value->as_angle().angle() == default_angle))
+        builder.appendff(" {}", angle_string);
+
+    return MUST(builder.to_string());
+}
+
+}

Libraries/LibWeb/CSS/StyleValues/FontStyleStyleValue.h

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2025, Tim Ledbetter <tim.ledbetter@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/CSS/CSSStyleValue.h>
+#include <LibWeb/CSS/Enums.h>
+
+namespace Web::CSS {
+
+class FontStyleStyleValue final : public StyleValueWithDefaultOperators<FontStyleStyleValue> {
+public:
+    static ValueComparingNonnullRefPtr<FontStyleStyleValue const> create(FontStyle font_style, ValueComparingRefPtr<CSSStyleValue const> angle_value = {})
+    {
+        return adopt_ref(*new (nothrow) FontStyleStyleValue(font_style, angle_value));
+    }
+
+    virtual ~FontStyleStyleValue() override;
+
+    FontStyle font_style() const { return m_font_style; }
+    ValueComparingRefPtr<CSSStyleValue const> angle() const { return m_angle_value; }
+
+    virtual String to_string(SerializationMode) const override;
+
+    bool equals(CSSStyleValue const& other) const override
+    {
+        if (type() != other.type())
+            return false;
+        auto const& other_font_style = other.as_font_style();
+        return m_font_style == other_font_style.m_font_style && m_angle_value == other_font_style.m_angle_value;
+    }
+
+    bool properties_equal(FontStyleStyleValue const& other) const { return m_font_style == other.m_font_style && m_angle_value == other.m_angle_value; }
+
+private:
+    FontStyleStyleValue(FontStyle, ValueComparingRefPtr<CSSStyleValue const> angle_value);
+
+    FontStyle m_font_style;
+    ValueComparingRefPtr<CSSStyleValue const> m_angle_value;
+};
+
+}

Libraries/LibWeb/CSS/StyleValues/ShorthandStyleValue.cpp

@@ -233,8 +233,9 @@ String ShorthandStyleValue::to_string(SerializationMode mode) const
                 builder.append(' ');
             builder.append(string);
         };
-        if (font_style->to_keyword() != Keyword::Normal && font_style->to_keyword() != Keyword::Initial)
-            append(font_style->to_string(mode));
+        auto font_style_string = font_style->to_string(mode);
+        if (font_style_string != "normal"sv)
+            append(font_style_string);
         if (font_variant_string != "normal"sv && font_variant_string != "initial"sv)
             append(font_variant_string);
         if (font_weight->to_font_weight() != Gfx::FontWeight::Regular && font_weight->to_keyword() != Keyword::Initial)