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diff --git a/servo/components/style/values/generics/basic_shape.rs b/servo/components/style/values/generics/basic_shape.rs
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+++ b/servo/components/style/values/generics/basic_shape.rs
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! CSS handling for the [`basic-shape`](https://drafts.csswg.org/css-shapes/#typedef-basic-shape)
+//! types that are generic over their `ToCss` implementations.
+
+use crate::values::animated::{lists, Animate, Procedure, ToAnimatedZero};
+use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
+use crate::values::generics::border::GenericBorderRadius;
+use crate::values::generics::position::GenericPositionOrAuto;
+use crate::values::generics::rect::Rect;
+use crate::values::specified::SVGPathData;
+use crate::Zero;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
+
+/// <https://drafts.fxtf.org/css-masking-1/#typedef-geometry-box>
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    Parse,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum ShapeGeometryBox {
+    /// Depending on which kind of element this style value applied on, the
+    /// default value of the reference-box can be different.  For an HTML
+    /// element, the default value of reference-box is border-box; for an SVG
+    /// element, the default value is fill-box.  Since we can not determine the
+    /// default value at parsing time, we keep this value to make a decision on
+    /// it.
+    #[css(skip)]
+    ElementDependent,
+    FillBox,
+    StrokeBox,
+    ViewBox,
+    ShapeBox(ShapeBox),
+}
+
+impl Default for ShapeGeometryBox {
+    fn default() -> Self {
+        Self::ElementDependent
+    }
+}
+
+/// Skip the serialization if the author omits the box or specifies border-box.
+#[inline]
+fn is_default_box_for_clip_path(b: &ShapeGeometryBox) -> bool {
+    // Note: for clip-path, ElementDependent is always border-box, so we have to check both of them
+    // for serialization.
+    matches!(b, ShapeGeometryBox::ElementDependent) ||
+        matches!(b, ShapeGeometryBox::ShapeBox(ShapeBox::BorderBox))
+}
+
+/// https://drafts.csswg.org/css-shapes-1/#typedef-shape-box
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Animate,
+    Clone,
+    Copy,
+    ComputeSquaredDistance,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum ShapeBox {
+    MarginBox,
+    BorderBox,
+    PaddingBox,
+    ContentBox,
+}
+
+impl Default for ShapeBox {
+    fn default() -> Self {
+        ShapeBox::MarginBox
+    }
+}
+
+/// A value for the `clip-path` property.
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[animation(no_bound(U))]
+#[repr(u8)]
+pub enum GenericClipPath<BasicShape, U> {
+    #[animation(error)]
+    None,
+    #[animation(error)]
+    Url(U),
+    Shape(
+        Box<BasicShape>,
+        #[css(skip_if = "is_default_box_for_clip_path")] ShapeGeometryBox,
+    ),
+    #[animation(error)]
+    Box(ShapeGeometryBox),
+}
+
+pub use self::GenericClipPath as ClipPath;
+
+/// A value for the `shape-outside` property.
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[animation(no_bound(I))]
+#[repr(u8)]
+pub enum GenericShapeOutside<BasicShape, I> {
+    #[animation(error)]
+    None,
+    #[animation(error)]
+    Image(I),
+    Shape(Box<BasicShape>, #[css(skip_if = "is_default")] ShapeBox),
+    #[animation(error)]
+    Box(ShapeBox),
+}
+
+pub use self::GenericShapeOutside as ShapeOutside;
+
+/// The <basic-shape>.
+///
+/// https://drafts.csswg.org/css-shapes-1/#supported-basic-shapes
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericBasicShape<Position, LengthPercentage, NonNegativeLengthPercentage, BasicShapeRect>
+{
+    /// The <basic-shape-rect>.
+    Rect(BasicShapeRect),
+    /// Defines a circle with a center and a radius.
+    Circle(
+        #[css(field_bound)]
+        #[shmem(field_bound)]
+        Circle<Position, NonNegativeLengthPercentage>,
+    ),
+    /// Defines an ellipse with a center and x-axis/y-axis radii.
+    Ellipse(
+        #[css(field_bound)]
+        #[shmem(field_bound)]
+        Ellipse<Position, NonNegativeLengthPercentage>,
+    ),
+    /// Defines a polygon with pair arguments.
+    Polygon(GenericPolygon<LengthPercentage>),
+    /// Defines a path with SVG path syntax.
+    Path(Path),
+    // TODO: Bug 1823463. Add shape().
+    // https://drafts.csswg.org/css-shapes-2/#shape-function
+}
+
+pub use self::GenericBasicShape as BasicShape;
+
+/// <https://drafts.csswg.org/css-shapes/#funcdef-inset>
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(function = "inset")]
+#[repr(C)]
+pub struct GenericInsetRect<LengthPercentage, NonNegativeLengthPercentage> {
+    pub rect: Rect<LengthPercentage>,
+    #[shmem(field_bound)]
+    pub round: GenericBorderRadius<NonNegativeLengthPercentage>,
+}
+
+pub use self::GenericInsetRect as InsetRect;
+
+/// <https://drafts.csswg.org/css-shapes/#funcdef-circle>
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(function)]
+#[repr(C)]
+pub struct Circle<Position, NonNegativeLengthPercentage> {
+    pub position: GenericPositionOrAuto<Position>,
+    pub radius: GenericShapeRadius<NonNegativeLengthPercentage>,
+}
+
+/// <https://drafts.csswg.org/css-shapes/#funcdef-ellipse>
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(function)]
+#[repr(C)]
+pub struct Ellipse<Position, NonNegativeLengthPercentage> {
+    pub position: GenericPositionOrAuto<Position>,
+    pub semiaxis_x: GenericShapeRadius<NonNegativeLengthPercentage>,
+    pub semiaxis_y: GenericShapeRadius<NonNegativeLengthPercentage>,
+}
+
+/// <https://drafts.csswg.org/css-shapes/#typedef-shape-radius>
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericShapeRadius<NonNegativeLengthPercentage> {
+    Length(NonNegativeLengthPercentage),
+    #[animation(error)]
+    ClosestSide,
+    #[animation(error)]
+    FarthestSide,
+}
+
+pub use self::GenericShapeRadius as ShapeRadius;
+
+/// A generic type for representing the `polygon()` function
+///
+/// <https://drafts.csswg.org/css-shapes/#funcdef-polygon>
+#[derive(
+    Clone,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(comma, function = "polygon")]
+#[repr(C)]
+pub struct GenericPolygon<LengthPercentage> {
+    /// The filling rule for a polygon.
+    #[css(skip_if = "is_default")]
+    pub fill: FillRule,
+    /// A collection of (x, y) coordinates to draw the polygon.
+    #[css(iterable)]
+    pub coordinates: crate::OwnedSlice<PolygonCoord<LengthPercentage>>,
+}
+
+pub use self::GenericPolygon as Polygon;
+
+/// Coordinates for Polygon.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct PolygonCoord<LengthPercentage>(pub LengthPercentage, pub LengthPercentage);
+
+// https://drafts.csswg.org/css-shapes/#typedef-fill-rule
+// NOTE: Basic shapes spec says that these are the only two values, however
+// https://www.w3.org/TR/SVG/painting.html#FillRuleProperty
+// says that it can also be `inherit`
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Deserialize,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum FillRule {
+    Nonzero,
+    Evenodd,
+}
+
+/// The path function defined in css-shape-2.
+///
+/// https://drafts.csswg.org/css-shapes-2/#funcdef-path
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(comma, function = "path")]
+#[repr(C)]
+pub struct Path {
+    /// The filling rule for the svg path.
+    #[css(skip_if = "is_default")]
+    pub fill: FillRule,
+    /// The svg path data.
+    pub path: SVGPathData,
+}
+
+impl<B, U> ToAnimatedZero for ClipPath<B, U> {
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Err(())
+    }
+}
+
+impl<B, U> ToAnimatedZero for ShapeOutside<B, U> {
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Err(())
+    }
+}
+
+impl<Length, NonNegativeLength> ToCss for InsetRect<Length, NonNegativeLength>
+where
+    Length: ToCss + PartialEq,
+    NonNegativeLength: ToCss + PartialEq + Zero,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        dest.write_str("inset(")?;
+        self.rect.to_css(dest)?;
+        if !self.round.is_zero() {
+            dest.write_str(" round ")?;
+            self.round.to_css(dest)?;
+        }
+        dest.write_char(')')
+    }
+}
+
+impl<Position, NonNegativeLengthPercentage> ToCss for Circle<Position, NonNegativeLengthPercentage>
+where
+    Position: ToCss,
+    NonNegativeLengthPercentage: ToCss + PartialEq,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        let has_radius = self.radius != Default::default();
+
+        dest.write_str("circle(")?;
+        if has_radius {
+            self.radius.to_css(dest)?;
+        }
+
+        // Preserve the `at <position>` even if it specified the default value.
+        // https://github.com/w3c/csswg-drafts/issues/8695
+        if !matches!(self.position, GenericPositionOrAuto::Auto) {
+            if has_radius {
+                dest.write_char(' ')?;
+            }
+            dest.write_str("at ")?;
+            self.position.to_css(dest)?;
+        }
+        dest.write_char(')')
+    }
+}
+
+impl<Position, NonNegativeLengthPercentage> ToCss for Ellipse<Position, NonNegativeLengthPercentage>
+where
+    Position: ToCss,
+    NonNegativeLengthPercentage: ToCss + PartialEq,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        let has_radii =
+            self.semiaxis_x != Default::default() || self.semiaxis_y != Default::default();
+
+        dest.write_str("ellipse(")?;
+        if has_radii {
+            self.semiaxis_x.to_css(dest)?;
+            dest.write_char(' ')?;
+            self.semiaxis_y.to_css(dest)?;
+        }
+
+        // Preserve the `at <position>` even if it specified the default value.
+        // https://github.com/w3c/csswg-drafts/issues/8695
+        if !matches!(self.position, GenericPositionOrAuto::Auto) {
+            if has_radii {
+                dest.write_char(' ')?;
+            }
+            dest.write_str("at ")?;
+            self.position.to_css(dest)?;
+        }
+        dest.write_char(')')
+    }
+}
+
+impl<L> Default for ShapeRadius<L> {
+    #[inline]
+    fn default() -> Self {
+        ShapeRadius::ClosestSide
+    }
+}
+
+impl<L> Animate for Polygon<L>
+where
+    L: Animate,
+{
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        if self.fill != other.fill {
+            return Err(());
+        }
+        let coordinates =
+            lists::by_computed_value::animate(&self.coordinates, &other.coordinates, procedure)?;
+        Ok(Polygon {
+            fill: self.fill,
+            coordinates,
+        })
+    }
+}
+
+impl<L> ComputeSquaredDistance for Polygon<L>
+where
+    L: ComputeSquaredDistance,
+{
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        if self.fill != other.fill {
+            return Err(());
+        }
+        lists::by_computed_value::squared_distance(&self.coordinates, &other.coordinates)
+    }
+}
+
+impl Default for FillRule {
+    #[inline]
+    fn default() -> Self {
+        FillRule::Nonzero
+    }
+}
+
+#[inline]
+fn is_default<T: Default + PartialEq>(fill: &T) -> bool {
+    *fill == Default::default()
+}