LibWeb: Add LinearGradientStyleValue

Userland/Libraries/LibWeb/CSS/StyleValue.cpp

@@ -143,6 +143,12 @@ LengthStyleValue const& StyleValue::as_length() const
     return static_cast<LengthStyleValue const&>(*this);
 }
 
+LinearGradientStyleValue const& StyleValue::as_linear_gradient() const
+{
+    VERIFY(is_linear_gradient());
+    return static_cast<LinearGradientStyleValue const&>(*this);
+}
+
 ListStyleStyleValue const& StyleValue::as_list_style() const
 {
     VERIFY(is_list_style());
@@ -1402,6 +1408,124 @@ bool ImageStyleValue::equals(StyleValue const& other) const
     return m_url == other.as_image().m_url;
 }
 
+String LinearGradientStyleValue::to_string() const
+{
+    StringBuilder builder;
+    auto side_or_corner_to_string = [](SideOrCorner value) {
+        switch (value) {
+        case SideOrCorner::Top:
+            return "top"sv;
+        case SideOrCorner::Bottom:
+            return "bottom"sv;
+        case SideOrCorner::Left:
+            return "left"sv;
+        case SideOrCorner::Right:
+            return "right"sv;
+        case SideOrCorner::TopLeft:
+            return "top left"sv;
+        case SideOrCorner::TopRight:
+            return "top right"sv;
+        case SideOrCorner::BottomLeft:
+            return "bottom left"sv;
+        case SideOrCorner::BottomRight:
+            return "bottom right"sv;
+        default:
+            VERIFY_NOT_REACHED();
+        }
+    };
+
+    builder.append("linear-gradient("sv);
+    m_direction.visit(
+        [&](SideOrCorner side_or_corner) {
+            builder.appendff("to {}, "sv, side_or_corner_to_string(side_or_corner));
+        },
+        [&](Angle const& angle) {
+            builder.appendff("{}, "sv, angle.to_string());
+        });
+
+    bool first = true;
+    for (auto const& element : m_color_stop_list) {
+        if (!first)
+            builder.append(", "sv);
+
+        if (element.transition_hint.has_value()) {
+            builder.appendff("{}, "sv, element.transition_hint->value.to_string());
+        }
+
+        serialize_a_srgb_value(builder, element.color_stop.color);
+        if (element.color_stop.length.has_value()) {
+            builder.appendff(" {}"sv, element.color_stop.length->to_string());
+        }
+        first = false;
+    }
+    builder.append(")"sv);
+    return builder.to_string();
+}
+
+static bool operator==(LinearGradientStyleValue::GradientDirection a, LinearGradientStyleValue::GradientDirection b)
+{
+    if (a.has<SideOrCorner>() && b.has<SideOrCorner>())
+        return a.get<SideOrCorner>() == b.get<SideOrCorner>();
+    if (a.has<Angle>() && b.has<Angle>())
+        return a.get<Angle>() == b.get<Angle>();
+    return false;
+}
+
+static bool operator==(GradientColorHint a, GradientColorHint b)
+{
+    return a.value == b.value;
+}
+
+static bool operator==(GradientColorStop a, GradientColorStop b)
+{
+    return a.color == b.color && a.length == b.length;
+}
+
+static bool operator==(ColorStopListElement a, ColorStopListElement b)
+{
+    return a.transition_hint == b.transition_hint && a.color_stop == b.color_stop;
+}
+
+bool LinearGradientStyleValue::equals(StyleValue const& other_) const
+{
+    if (type() != other_.type())
+        return false;
+    auto& other = other_.as_linear_gradient();
+
+    if (m_direction != other.m_direction || m_color_stop_list.size() != other.m_color_stop_list.size())
+        return false;
+
+    for (size_t i = 0; i < m_color_stop_list.size(); i++) {
+        if (m_color_stop_list[i] != other.m_color_stop_list[i])
+            return false;
+    }
+    return true;
+}
+
+float LinearGradientStyleValue::angle(Gfx::FloatRect const& background_box) const
+{
+    (void)background_box;
+    return m_direction.visit(
+        [&](SideOrCorner side_or_corner) {
+            switch (side_or_corner) {
+            case SideOrCorner::Top:
+                return 0.0f;
+            case SideOrCorner::Bottom:
+                return 180.0f;
+            case SideOrCorner::Left:
+                return 270.0f;
+            case SideOrCorner::Right:
+                return 90.0f;
+            default:
+                // FIXME: Angle gradients towards corners
+                return 0.0f;
+            }
+        },
+        [&](Angle const& angle) {
+            return angle.to_degrees();
+        });
+}
+
 bool InheritStyleValue::equals(StyleValue const& other) const
 {
     return type() == other.type();

Userland/Libraries/LibWeb/CSS/StyleValue.h

@@ -58,6 +58,31 @@ enum class FlexBasis {
     Auto,
 };
 
+enum class SideOrCorner {
+    Top,
+    Bottom,
+    Left,
+    Right,
+    TopLeft,
+    TopRight,
+    BottomLeft,
+    BottomRight
+};
+
+struct GradientColorStop {
+    Color color;
+    Optional<LengthPercentage> length;
+};
+
+struct GradientColorHint {
+    LengthPercentage value;
+};
+
+struct ColorStopListElement {
+    Optional<GradientColorHint> transition_hint;
+    GradientColorStop color_stop;
+};
+
 // FIXME: Find a better place for this helper.
 inline Gfx::Painter::ScalingMode to_gfx_scaling_mode(CSS::ImageRendering css_value)
 {
@@ -99,6 +124,7 @@ public:
         Initial,
         Invalid,
         Length,
+        LinearGradient,
         ListStyle,
         Numeric,
         Overflow,
@@ -112,7 +138,7 @@ public:
         Transformation,
         Unresolved,
         Unset,
-        ValueList,
+        ValueList
     };
 
     Type type() const { return m_type; }
@@ -136,6 +162,7 @@ public:
     bool is_inherit() const { return type() == Type::Inherit; }
     bool is_initial() const { return type() == Type::Initial; }
     bool is_length() const { return type() == Type::Length; }
+    bool is_linear_gradient() const { return type() == Type::LinearGradient; }
     bool is_list_style() const { return type() == Type::ListStyle; }
     bool is_numeric() const { return type() == Type::Numeric; }
     bool is_overflow() const { return type() == Type::Overflow; }
@@ -172,6 +199,7 @@ public:
     InheritStyleValue const& as_inherit() const;
     InitialStyleValue const& as_initial() const;
     LengthStyleValue const& as_length() const;
+    LinearGradientStyleValue const& as_linear_gradient() const;
     ListStyleStyleValue const& as_list_style() const;
     NumericStyleValue const& as_numeric() const;
     OverflowStyleValue const& as_overflow() const;
@@ -206,6 +234,7 @@ public:
     InheritStyleValue& as_inherit() { return const_cast<InheritStyleValue&>(const_cast<StyleValue const&>(*this).as_inherit()); }
     InitialStyleValue& as_initial() { return const_cast<InitialStyleValue&>(const_cast<StyleValue const&>(*this).as_initial()); }
     LengthStyleValue& as_length() { return const_cast<LengthStyleValue&>(const_cast<StyleValue const&>(*this).as_length()); }
+    LinearGradientStyleValue& as_linear_gradient() { return const_cast<LinearGradientStyleValue&>(const_cast<StyleValue const&>(*this).as_linear_gradient()); }
     ListStyleStyleValue& as_list_style() { return const_cast<ListStyleStyleValue&>(const_cast<StyleValue const&>(*this).as_list_style()); }
     NumericStyleValue& as_numeric() { return const_cast<NumericStyleValue&>(const_cast<StyleValue const&>(*this).as_numeric()); }
     OverflowStyleValue& as_overflow() { return const_cast<OverflowStyleValue&>(const_cast<StyleValue const&>(*this).as_overflow()); }
@@ -887,6 +916,39 @@ private:
     RefPtr<Gfx::Bitmap> m_bitmap;
 };
 
+class LinearGradientStyleValue final : public StyleValue {
+public:
+    using GradientDirection = Variant<Angle, SideOrCorner>;
+
+    static NonnullRefPtr<LinearGradientStyleValue> create(GradientDirection direction, Vector<ColorStopListElement> color_stop_list)
+    {
+        VERIFY(color_stop_list.size() >= 2);
+        return adopt_ref(*new LinearGradientStyleValue(direction, move(color_stop_list)));
+    }
+
+    virtual String to_string() const override;
+    virtual ~LinearGradientStyleValue() override = default;
+    virtual bool equals(StyleValue const& other) const override;
+
+    Vector<ColorStopListElement> const& color_stop_list() const
+    {
+        return m_color_stop_list;
+    }
+
+    float angle(Gfx::FloatRect const& background_box) const;
+
+private:
+    LinearGradientStyleValue(GradientDirection direction, Vector<ColorStopListElement> color_stop_list)
+        : StyleValue(Type::LinearGradient)
+        , m_direction(direction)
+        , m_color_stop_list(move(color_stop_list))
+    {
+    }
+
+    GradientDirection m_direction;
+    Vector<ColorStopListElement> m_color_stop_list;
+};
+
 class InheritStyleValue final : public StyleValue {
 public:
     static NonnullRefPtr<InheritStyleValue> the()

Userland/Libraries/LibWeb/Forward.h

@@ -62,6 +62,7 @@ class InitialStyleValue;
 class Length;
 class LengthPercentage;
 class LengthStyleValue;
+class LinearGradientStyleValue;
 class ListStyleStyleValue;
 class MediaList;
 class MediaQuery;