diff --git a/servo/components/style/gecko_conversions.rs b/servo/components/style/gecko_conversions.rs
index ede574d181eb..4e3a5acf2c90 100644
--- a/servo/components/style/gecko_conversions.rs
+++ b/servo/components/style/gecko_conversions.rs
@@ -79,3 +79,182 @@ impl From<nsStyleCoord_CalcValue> for LengthOrPercentage {
         }
     }
 }
+
+pub mod basic_shape {
+    use euclid::size::Size2D;
+    use gecko_bindings::structs::StyleClipPathGeometryBox;
+    use gecko_bindings::structs::{StyleBasicShape, StyleBasicShapeType, StyleFillRule};
+    use gecko_bindings::structs::{nsStyleCoord, nsStyleCorners, nsStyleImageLayers_Position};
+    use gecko_bindings::sugar::ns_style_coord::{CoordDataMut, CoordDataValue};
+    use gecko_values::GeckoStyleCoordConvertible;
+    use std::borrow::Borrow;
+    use values::computed::basic_shape::*;
+    use values::computed::position::Position;
+    use values::computed::{BorderRadiusSize, LengthOrPercentage};
+
+    // using Borrow so that we can have a non-moving .into()
+    impl<T: Borrow<StyleBasicShape>> From<T> for BasicShape {
+        fn from(other: T) -> Self {
+            let other = other.borrow();
+            match other.mType {
+                StyleBasicShapeType::Inset => {
+                    let t = LengthOrPercentage::from_gecko_style_coord(&other.mCoordinates[0]);
+                    let r = LengthOrPercentage::from_gecko_style_coord(&other.mCoordinates[1]);
+                    let b = LengthOrPercentage::from_gecko_style_coord(&other.mCoordinates[2]);
+                    let l = LengthOrPercentage::from_gecko_style_coord(&other.mCoordinates[3]);
+                    let round = (&other.mRadius).into();
+                    BasicShape::Inset(InsetRect {
+                        top: t.expect("inset() offset should be a length, percentage, or calc value"),
+                        right: r.expect("inset() offset should be a length, percentage, or calc value"),
+                        bottom: b.expect("inset() offset should be a length, percentage, or calc value"),
+                        left: l.expect("inset() offset should be a length, percentage, or calc value"),
+                        round: Some(round),
+                    })
+                }
+                StyleBasicShapeType::Circle => {
+                    BasicShape::Circle(Circle {
+                        radius: (&other.mCoordinates[0]).into(),
+                        position: (&other.mPosition).into()
+                    })
+                }
+                StyleBasicShapeType::Ellipse => {
+                    BasicShape::Ellipse(Ellipse {
+                        semiaxis_x: (&other.mCoordinates[0]).into(),
+                        semiaxis_y: (&other.mCoordinates[1]).into(),
+                        position: (&other.mPosition).into()
+                    })
+                }
+                StyleBasicShapeType::Polygon => {
+                    let fill_rule = if other.mFillRule == StyleFillRule::Evenodd {
+                        FillRule::EvenOdd
+                    } else {
+                        FillRule::NonZero
+                    };
+                    let mut coords = Vec::with_capacity(other.mCoordinates.len() / 2);
+                    for i in 0..(other.mCoordinates.len() / 2) {
+                        let x = 2 * i;
+                        let y = x + 1;
+                        coords.push((LengthOrPercentage::from_gecko_style_coord(&other.mCoordinates[x])
+                                    .expect("polygon() coordinate should be a length, percentage, or calc value"),
+                                LengthOrPercentage::from_gecko_style_coord(&other.mCoordinates[y])
+                                    .expect("polygon() coordinate should be a length, percentage, or calc value")
+                            ))
+                    }
+                    BasicShape::Polygon(Polygon {
+                        fill: fill_rule,
+                        coordinates: coords,
+                    })
+                }
+            }
+        }
+    }
+
+    impl<T: Borrow<nsStyleCorners>> From<T> for BorderRadius {
+        fn from(other: T) -> Self {
+            let other = other.borrow();
+            let get_corner = |index| {
+                BorderRadiusSize(Size2D::new(
+                    LengthOrPercentage::from_gecko_style_coord(&other.data_at(index))
+                        .expect("<border-radius> should be a length, percentage, or calc value"),
+                    LengthOrPercentage::from_gecko_style_coord(&other.data_at(index + 1))
+                        .expect("<border-radius> should be a length, percentage, or calc value")))
+            };
+
+            BorderRadius {
+                top_left: get_corner(0),
+                top_right: get_corner(2),
+                bottom_right: get_corner(4),
+                bottom_left: get_corner(6),
+            }
+        }
+    }
+
+    // Can't be a From impl since we need to set an existing
+    // nsStyleCorners, not create a new one
+    impl BorderRadius {
+        pub fn set_corners(&self, other: &mut nsStyleCorners) {
+            let mut set_corner = |field: &BorderRadiusSize, index| {
+                field.0.width.to_gecko_style_coord(&mut other.data_at_mut(index));
+                field.0.height.to_gecko_style_coord(&mut other.data_at_mut(index + 1));
+            };
+            set_corner(&self.top_left, 0);
+            set_corner(&self.top_right, 2);
+            set_corner(&self.bottom_right, 4);
+            set_corner(&self.bottom_left, 6);
+        }
+    }
+
+    /// We use None for a nonexistant radius, but Gecko uses (0 0 0 0 / 0 0 0 0)
+    pub fn set_corners_from_radius(radius: Option<BorderRadius>, other: &mut nsStyleCorners) {
+        if let Some(radius) = radius {
+            radius.set_corners(other);
+        } else {
+            for i in 0..8 {
+                other.data_at_mut(i).set_value(CoordDataValue::Coord(0));
+            }
+        }
+    }
+
+    // Can't be a From impl since we need to set an existing
+    // nsStyleImageLayers_Position, not create a new one
+    impl From<Position> for nsStyleImageLayers_Position {
+        fn from(other: Position) -> Self {
+            nsStyleImageLayers_Position {
+                mXPosition: other.horizontal.into(),
+                mYPosition: other.vertical.into()
+            }
+        }
+    }
+
+    impl<T: Borrow<nsStyleCoord>> From<T> for ShapeRadius {
+        fn from(other: T) -> Self {
+            let other = other.borrow();
+            ShapeRadius::from_gecko_style_coord(other)
+                .expect("<shape-radius> should be a length, percentage, calc, or keyword value")
+        }
+    }
+
+    impl<T: Borrow<nsStyleImageLayers_Position>> From<T> for Position {
+        fn from(other: T) -> Self {
+            let other = other.borrow();
+            Position {
+                horizontal: other.mXPosition.into(),
+                vertical: other.mYPosition.into(),
+            }
+        }
+    }
+
+    impl From<GeometryBox> for StyleClipPathGeometryBox {
+        fn from(reference: GeometryBox) -> Self {
+            use gecko_bindings::structs::StyleClipPathGeometryBox::*;
+            match reference {
+                GeometryBox::ShapeBox(ShapeBox::Content) => Content,
+                GeometryBox::ShapeBox(ShapeBox::Padding) => Padding,
+                GeometryBox::ShapeBox(ShapeBox::Border) => Border,
+                GeometryBox::ShapeBox(ShapeBox::Margin) => Margin,
+                GeometryBox::Fill => Fill,
+                GeometryBox::Stroke => Stroke,
+                GeometryBox::View => View,
+            }
+        }
+    }
+
+    // Will panic on NoBox
+    // Ideally these would be implemented on Option<T>,
+    // but coherence doesn't like that and TryFrom isn't stable
+    impl From<StyleClipPathGeometryBox> for GeometryBox {
+        fn from(reference: StyleClipPathGeometryBox) -> Self {
+            use gecko_bindings::structs::StyleClipPathGeometryBox::*;
+            match reference {
+                NoBox => panic!("Shouldn't convert NoBox to GeometryBox"),
+                Content => GeometryBox::ShapeBox(ShapeBox::Content),
+                Padding => GeometryBox::ShapeBox(ShapeBox::Padding),
+                Border => GeometryBox::ShapeBox(ShapeBox::Border),
+                Margin => GeometryBox::ShapeBox(ShapeBox::Margin),
+                Fill => GeometryBox::Fill,
+                Stroke => GeometryBox::Stroke,
+                View => GeometryBox::View,
+            }
+        }
+    }
+}
diff --git a/servo/components/style/gecko_values.rs b/servo/components/style/gecko_values.rs
index efbcb7db93e1..f3c570f34cc5 100644
--- a/servo/components/style/gecko_values.rs
+++ b/servo/components/style/gecko_values.rs
@@ -7,12 +7,13 @@
 use app_units::Au;
 use cssparser::RGBA;
 use gecko_bindings::structs::nsStyleCoord;
+use gecko_bindings::structs::{NS_RADIUS_CLOSEST_SIDE, NS_RADIUS_FARTHEST_SIDE};
 use gecko_bindings::sugar::ns_style_coord::{CoordDataValue, CoordData, CoordDataMut};
 use std::cmp::max;
 use values::computed::Angle;
+use values::computed::basic_shape::ShapeRadius;
 use values::computed::{LengthOrPercentage, LengthOrPercentageOrAuto, LengthOrPercentageOrNone};
 
-
 pub trait StyleCoordHelpers {
     fn set<T: GeckoStyleCoordConvertible>(&mut self, val: T);
 }
@@ -94,6 +95,28 @@ impl GeckoStyleCoordConvertible for LengthOrPercentageOrNone {
     }
 }
 
+impl GeckoStyleCoordConvertible for ShapeRadius {
+    fn to_gecko_style_coord<T: CoordDataMut>(&self, coord: &mut T) {
+        match *self {
+            ShapeRadius::ClosestSide => {
+                coord.set_value(CoordDataValue::Enumerated(NS_RADIUS_CLOSEST_SIDE))
+            }
+            ShapeRadius::FarthestSide => {
+                coord.set_value(CoordDataValue::Enumerated(NS_RADIUS_FARTHEST_SIDE))
+            }
+            ShapeRadius::Length(lop) => lop.to_gecko_style_coord(coord),
+        }
+    }
+
+    fn from_gecko_style_coord<T: CoordData>(coord: &T) -> Option<Self> {
+        match coord.as_value() {
+            CoordDataValue::Enumerated(NS_RADIUS_CLOSEST_SIDE) => Some(ShapeRadius::ClosestSide),
+            CoordDataValue::Enumerated(NS_RADIUS_FARTHEST_SIDE) => Some(ShapeRadius::FarthestSide),
+            _ => LengthOrPercentage::from_gecko_style_coord(coord).map(ShapeRadius::Length),
+        }
+    }
+}
+
 impl<T: GeckoStyleCoordConvertible> GeckoStyleCoordConvertible for Option<T> {
     fn to_gecko_style_coord<U: CoordDataMut>(&self, coord: &mut U) {
         if let Some(ref me) = *self {
diff --git a/servo/components/style/parser.rs b/servo/components/style/parser.rs
index 52ce1d9d5fd1..db281ec24e2c 100644
--- a/servo/components/style/parser.rs
+++ b/servo/components/style/parser.rs
@@ -81,3 +81,11 @@ impl<'a> ParserContext<'a> {
 pub fn log_css_error(input: &mut Parser, position: SourcePosition, message: &str, parsercontext: &ParserContext) {
     parsercontext.error_reporter.report_error(input, position, message);
 }
+
+// XXXManishearth Replace all specified value parse impls with impls of this
+// trait. This will make it easy to write more generic values in the future.
+// There may need to be two traits -- one for parsing with context, and one
+// for parsing without
+pub trait Parse {
+    fn parse(input: &mut Parser) -> Result<Self, ()> where Self: Sized;
+}
diff --git a/servo/components/style/properties/gecko.mako.rs b/servo/components/style/properties/gecko.mako.rs
index 085c35219c3a..0c717ee678cd 100644
--- a/servo/components/style/properties/gecko.mako.rs
+++ b/servo/components/style/properties/gecko.mako.rs
@@ -1265,7 +1265,7 @@ fn static_assert() {
 </%self:impl_trait>
 
 <%self:impl_trait style_struct_name="SVG"
-                  skip_longhands="flood-color lighting-color stop-color"
+                  skip_longhands="flood-color lighting-color stop-color clip-path"
                   skip_additionals="*">
 
     <% impl_color("flood_color", "mFloodColor") %>
@@ -1274,6 +1274,140 @@ fn static_assert() {
 
     <% impl_color("stop_color", "mStopColor") %>
 
+    pub fn set_clip_path(&mut self, v: longhands::clip_path::computed_value::T) {
+        use gecko_bindings::bindings::{Gecko_NewBasicShape, Gecko_DestroyClipPath};
+        use gecko_bindings::structs::StyleClipPathGeometryBox;
+        use gecko_bindings::structs::{StyleBasicShape, StyleBasicShapeType, StyleShapeSourceType};
+        use gecko_bindings::structs::{StyleClipPath, StyleFillRule};
+        use gecko_conversions::basic_shape::set_corners_from_radius;
+        use gecko_values::GeckoStyleCoordConvertible;
+        use values::computed::basic_shape::*;
+        let ref mut clip_path = self.gecko.mClipPath;
+        // clean up existing struct
+        unsafe { Gecko_DestroyClipPath(clip_path) };
+
+        clip_path.mType = StyleShapeSourceType::None_;
+
+        match v {
+            ShapeSource::Url(..) => println!("stylo: clip-path: url() not yet implemented"),
+            ShapeSource::None => {} // don't change the type
+            ShapeSource::Box(reference) => {
+                clip_path.mReferenceBox = reference.into();
+                clip_path.mType = StyleShapeSourceType::Box;
+            }
+            ShapeSource::Shape(servo_shape, maybe_box) => {
+                clip_path.mReferenceBox = maybe_box.map(Into::into)
+                                                   .unwrap_or(StyleClipPathGeometryBox::NoBox);
+                clip_path.mType = StyleShapeSourceType::Shape;
+
+                fn init_shape(clip_path: &mut StyleClipPath, ty: StyleBasicShapeType) -> &mut StyleBasicShape {
+                    unsafe {
+                        // We have to be very careful to avoid a copy here!
+                        let ref mut union = clip_path.StyleShapeSource_nsStyleStruct_h_unnamed_26;
+                        let mut shape: &mut *mut StyleBasicShape = union.mBasicShape.as_mut();
+                        *shape = Gecko_NewBasicShape(ty);
+                        &mut **shape
+                    }
+                }
+                match servo_shape {
+                    BasicShape::Inset(rect) => {
+                        let mut shape = init_shape(clip_path, StyleBasicShapeType::Inset);
+                        unsafe { shape.mCoordinates.set_len(4) };
+
+                        // set_len() can't call constructors, so the coordinates
+                        // can contain any value. set_value() attempts to free
+                        // allocated coordinates, so we don't want to feed it
+                        // garbage values which it may misinterpret.
+                        // Instead, we use leaky_set_value to blindly overwrite
+                        // the garbage data without
+                        // attempting to clean up.
+                        shape.mCoordinates[0].leaky_set_null();
+                        rect.top.to_gecko_style_coord(&mut shape.mCoordinates[0]);
+                        shape.mCoordinates[1].leaky_set_null();
+                        rect.right.to_gecko_style_coord(&mut shape.mCoordinates[1]);
+                        shape.mCoordinates[2].leaky_set_null();
+                        rect.bottom.to_gecko_style_coord(&mut shape.mCoordinates[2]);
+                        shape.mCoordinates[3].leaky_set_null();
+                        rect.left.to_gecko_style_coord(&mut shape.mCoordinates[3]);
+
+                        set_corners_from_radius(rect.round, &mut shape.mRadius);
+                    }
+                    BasicShape::Circle(circ) => {
+                        let mut shape = init_shape(clip_path, StyleBasicShapeType::Circle);
+                        unsafe { shape.mCoordinates.set_len(1) };
+                        shape.mCoordinates[0].leaky_set_null();
+                        circ.radius.to_gecko_style_coord(&mut shape.mCoordinates[0]);
+
+                        shape.mPosition = circ.position.into();
+                    }
+                    BasicShape::Ellipse(el) => {
+                        let mut shape = init_shape(clip_path, StyleBasicShapeType::Ellipse);
+                        unsafe { shape.mCoordinates.set_len(2) };
+                        shape.mCoordinates[0].leaky_set_null();
+                        el.semiaxis_x.to_gecko_style_coord(&mut shape.mCoordinates[0]);
+                        shape.mCoordinates[1].leaky_set_null();
+                        el.semiaxis_y.to_gecko_style_coord(&mut shape.mCoordinates[1]);
+
+                        shape.mPosition = el.position.into();
+                    }
+                    BasicShape::Polygon(poly) => {
+                        let mut shape = init_shape(clip_path, StyleBasicShapeType::Polygon);
+                        unsafe {
+                            shape.mCoordinates.set_len(poly.coordinates.len() as u32 * 2);
+                        }
+                        for (i, coord) in poly.coordinates.iter().enumerate() {
+                            shape.mCoordinates[2 * i].leaky_set_null();
+                            shape.mCoordinates[2 * i + 1].leaky_set_null();
+                            coord.0.to_gecko_style_coord(&mut shape.mCoordinates[2 * i]);
+                            coord.1.to_gecko_style_coord(&mut shape.mCoordinates[2 * i + 1]);
+                        }
+                        shape.mFillRule = if poly.fill == FillRule::EvenOdd {
+                            StyleFillRule::Evenodd
+                        } else {
+                            StyleFillRule::Nonzero
+                        };
+                    }
+                }
+            }
+        }
+
+    }
+
+    pub fn copy_clip_path_from(&mut self, other: &Self) {
+        use gecko_bindings::bindings::Gecko_CopyClipPathValueFrom;
+        unsafe {
+            Gecko_CopyClipPathValueFrom(&mut self.gecko.mClipPath, &other.gecko.mClipPath);
+        }
+    }
+
+    pub fn clone_clip_path(&self) -> longhands::clip_path::computed_value::T {
+        use gecko_bindings::structs::StyleShapeSourceType;
+        use gecko_bindings::structs::StyleClipPathGeometryBox;
+        use values::computed::basic_shape::*;
+        let ref clip_path = self.gecko.mClipPath;
+
+        match clip_path.mType {
+            StyleShapeSourceType::None_ => ShapeSource::None,
+            StyleShapeSourceType::Box => {
+                ShapeSource::Box(clip_path.mReferenceBox.into())
+            }
+            StyleShapeSourceType::URL => {
+                warn!("stylo: clip-path: url() not implemented yet");
+                Default::default()
+            }
+            StyleShapeSourceType::Shape => {
+                let reference = if let StyleClipPathGeometryBox::NoBox = clip_path.mReferenceBox {
+                    None
+                } else {
+                    Some(clip_path.mReferenceBox.into())
+                };
+                let union = clip_path.StyleShapeSource_nsStyleStruct_h_unnamed_26;
+                let shape = unsafe { &**union.mBasicShape.as_ref() };
+                ShapeSource::Shape(shape.into(), reference)
+            }
+        }
+    }
+
 </%self:impl_trait>
 
 <%self:impl_trait style_struct_name="Color"
diff --git a/servo/components/style/properties/longhand/svg.mako.rs b/servo/components/style/properties/longhand/svg.mako.rs
index 49dd2bdbdacf..3d0c5cc48aa6 100644
--- a/servo/components/style/properties/longhand/svg.mako.rs
+++ b/servo/components/style/properties/longhand/svg.mako.rs
@@ -49,3 +49,31 @@ ${helpers.predefined_type(
 // https://www.w3.org/TR/css-masking-1/
 ${helpers.single_keyword("mask-type", "luminance alpha",
                          products="gecko", animatable=False)}
+
+<%helpers:longhand name="clip-path" animatable="False" products="gecko">
+    use cssparser::ToCss;
+    use std::fmt;
+    use values::LocalToCss;
+    use values::NoViewportPercentage;
+    use values::specified::basic_shape::{ShapeSource, GeometryBox};
+
+    pub mod computed_value {
+        use app_units::Au;
+        use values::computed::basic_shape::{ShapeSource, GeometryBox};
+
+        pub type T = ShapeSource<GeometryBox>;
+    }
+
+    pub type SpecifiedValue = ShapeSource<GeometryBox>;
+
+    #[inline]
+    pub fn get_initial_value() -> computed_value::T {
+        Default::default()
+    }
+
+    pub fn parse(context: &ParserContext, input: &mut Parser) -> Result<SpecifiedValue, ()> {
+        ShapeSource::parse(context, input)
+    }
+
+    impl NoViewportPercentage for SpecifiedValue {}
+</%helpers:longhand>
diff --git a/servo/components/style/values/computed/basic_shape.rs b/servo/components/style/values/computed/basic_shape.rs
index 7431e616665e..8ea013af0730 100644
--- a/servo/components/style/values/computed/basic_shape.rs
+++ b/servo/components/style/values/computed/basic_shape.rs
@@ -10,10 +10,46 @@
 use cssparser::ToCss;
 use properties::shorthands::serialize_four_sides;
 use std::fmt;
+use url::Url;
+use values::computed::UrlExtraData;
 use values::computed::position::Position;
 use values::computed::{BorderRadiusSize, LengthOrPercentage};
 
-pub use values::specified::basic_shape::FillRule;
+pub use values::specified::basic_shape::{FillRule, GeometryBox, ShapeBox};
+
+#[derive(Clone, PartialEq, Debug)]
+#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+pub enum ShapeSource<T> {
+    Url(Url, UrlExtraData),
+    Shape(BasicShape, Option<T>),
+    Box(T),
+    None,
+}
+
+impl<T> Default for ShapeSource<T> {
+    fn default() -> Self {
+        ShapeSource::None
+    }
+}
+
+impl<T: ToCss> ToCss for ShapeSource<T> {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        use values::LocalToCss;
+        match *self {
+            ShapeSource::Url(ref url, _) => url.to_css(dest),
+            ShapeSource::Shape(ref shape, Some(ref reference)) => {
+                try!(shape.to_css(dest));
+                try!(dest.write_str(" "));
+                reference.to_css(dest)
+            }
+            ShapeSource::Shape(ref shape, None) => shape.to_css(dest),
+            ShapeSource::Box(ref reference) => reference.to_css(dest),
+            ShapeSource::None => dest.write_str("none"),
+
+        }
+    }
+}
+
 
 #[derive(Clone, PartialEq, Debug)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
diff --git a/servo/components/style/values/specified/basic_shape.rs b/servo/components/style/values/specified/basic_shape.rs
index b50effd85ae1..ff9b88559a61 100644
--- a/servo/components/style/values/specified/basic_shape.rs
+++ b/servo/components/style/values/specified/basic_shape.rs
@@ -8,13 +8,111 @@
 //! [basic-shape]: https://drafts.csswg.org/css-shapes/#typedef-basic-shape
 
 use cssparser::{Parser, ToCss};
+use parser::{ParserContext, Parse};
 use properties::shorthands::{parse_four_sides, serialize_four_sides};
 use std::fmt;
+use url::Url;
 use values::computed::basic_shape as computed_basic_shape;
 use values::computed::{Context, ToComputedValue, ComputedValueAsSpecified};
+use values::specified::UrlExtraData;
 use values::specified::position::Position;
 use values::specified::{BorderRadiusSize, LengthOrPercentage, Percentage};
 
+/// A shape source, for some reference box
+///
+/// clip-path uses ShapeSource<GeometryBox>,
+/// shape-outside uses ShapeSource<ShapeBox>
+#[derive(Clone, PartialEq, Debug)]
+#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+pub enum ShapeSource<T> {
+    Url(Url, UrlExtraData),
+    Shape(BasicShape, Option<T>),
+    Box(T),
+    None,
+}
+
+impl<T> Default for ShapeSource<T> {
+    fn default() -> Self {
+        ShapeSource::None
+    }
+}
+
+impl<T: ToCss> ToCss for ShapeSource<T> {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        use values::LocalToCss;
+        match *self {
+            ShapeSource::Url(ref url, _) => url.to_css(dest),
+            ShapeSource::Shape(ref shape, Some(ref reference)) => {
+                try!(shape.to_css(dest));
+                try!(dest.write_str(" "));
+                reference.to_css(dest)
+            }
+            ShapeSource::Shape(ref shape, None) => shape.to_css(dest),
+            ShapeSource::Box(ref reference) => reference.to_css(dest),
+            ShapeSource::None => dest.write_str("none"),
+
+        }
+    }
+}
+
+impl<T: Parse + PartialEq + Copy> ShapeSource<T> {
+    pub fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
+        if let Ok(_) = input.try(|input| input.expect_ident_matching("none")) {
+            Ok(ShapeSource::None)
+        } else if let Ok(url) = input.try(|input| input.expect_url()) {
+            match UrlExtraData::make_from(context) {
+                Some(extra_data) => {
+                    Ok(ShapeSource::Url(context.parse_url(&url), extra_data))
+                },
+                None => Err(()),
+            }
+        } else {
+            fn parse_component<U: Parse>(input: &mut Parser, component: &mut Option<U>) -> bool {
+                if component.is_some() {
+                    return false; // already parsed this component
+                }
+                *component = input.try(U::parse).ok();
+                component.is_some()
+            }
+
+            let mut shape = None;
+            let mut reference = None;
+            loop {
+                if !parse_component(input, &mut shape) &&
+                   !parse_component(input, &mut reference) {
+                    break;
+                }
+            }
+            match (shape, reference) {
+                (Some(shape), _) => Ok(ShapeSource::Shape(shape, reference)),
+                (None, Some(reference)) => Ok(ShapeSource::Box(reference)),
+                (None, None) => Err(()),
+            }
+        }
+    }
+}
+
+impl<T: ToComputedValue> ToComputedValue for ShapeSource<T> {
+    type ComputedValue = computed_basic_shape::ShapeSource<T::ComputedValue>;
+    #[inline]
+    fn to_computed_value(&self, cx: &Context) -> Self::ComputedValue {
+        match *self {
+            ShapeSource::Url(ref url, ref data) => {
+                computed_basic_shape::ShapeSource::Url(url.clone(), data.clone())
+            }
+            ShapeSource::Shape(ref shape, ref reference) => {
+                computed_basic_shape::ShapeSource::Shape(
+                    shape.to_computed_value(cx),
+                    reference.as_ref().map(|ref r| r.to_computed_value(cx)))
+            }
+            ShapeSource::Box(ref reference) => {
+                computed_basic_shape::ShapeSource::Box(reference.to_computed_value(cx))
+            }
+            ShapeSource::None => computed_basic_shape::ShapeSource::None,
+        }
+    }
+}
+
 #[derive(Clone, PartialEq, Debug)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub enum BasicShape {
@@ -24,8 +122,8 @@ pub enum BasicShape {
     Polygon(Polygon),
 }
 
-impl BasicShape {
-    pub fn parse(input: &mut Parser) -> Result<BasicShape, ()> {
+impl Parse for BasicShape {
+    fn parse(input: &mut Parser) -> Result<BasicShape, ()> {
         match_ignore_ascii_case! { try!(input.expect_function()),
             "inset" => {
                 Ok(BasicShape::Inset(
@@ -528,3 +626,77 @@ impl ToCss for FillRule {
         }
     }
 }
+
+/// https://drafts.fxtf.org/css-masking-1/#typedef-geometry-box
+#[derive(Clone, PartialEq, Copy, Debug)]
+#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+pub enum GeometryBox {
+    Fill,
+    Stroke,
+    View,
+    ShapeBox(ShapeBox),
+}
+
+impl Parse for GeometryBox {
+    fn parse(input: &mut Parser) -> Result<Self, ()> {
+        if let Ok(shape_box) = input.try(ShapeBox::parse) {
+            Ok(GeometryBox::ShapeBox(shape_box))
+        } else {
+            match_ignore_ascii_case! { try!(input.expect_ident()),
+                "fill-box" => Ok(GeometryBox::Fill),
+                "stroke-box" => Ok(GeometryBox::Stroke),
+                "view-box" => Ok(GeometryBox::View),
+                _ => Err(())
+            }
+        }
+    }
+}
+
+impl ToCss for GeometryBox {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        match *self {
+            GeometryBox::Fill => dest.write_str("fill-box"),
+            GeometryBox::Stroke => dest.write_str("stroke-box"),
+            GeometryBox::View => dest.write_str("view-box"),
+            GeometryBox::ShapeBox(s) => s.to_css(dest),
+        }
+    }
+}
+
+impl ComputedValueAsSpecified for GeometryBox {}
+
+// https://drafts.csswg.org/css-shapes-1/#typedef-shape-box
+#[derive(Clone, PartialEq, Copy, Debug)]
+#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+pub enum ShapeBox {
+    Margin,
+    // https://drafts.csswg.org/css-backgrounds-3/#box
+    Border,
+    Padding,
+    Content,
+}
+
+impl Parse for ShapeBox {
+    fn parse(input: &mut Parser) -> Result<Self, ()> {
+        match_ignore_ascii_case! { try!(input.expect_ident()),
+            "margin-box" => Ok(ShapeBox::Margin),
+            "border-box" => Ok(ShapeBox::Border),
+            "padding-box" => Ok(ShapeBox::Padding),
+            "content-box" => Ok(ShapeBox::Content),
+            _ => Err(())
+        }
+    }
+}
+
+impl ToCss for ShapeBox {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        match *self {
+            ShapeBox::Margin => dest.write_str("margin-box"),
+            ShapeBox::Border => dest.write_str("border-box"),
+            ShapeBox::Padding => dest.write_str("padding-box"),
+            ShapeBox::Content => dest.write_str("content-box"),
+        }
+    }
+}
+
+impl ComputedValueAsSpecified for ShapeBox {}
diff --git a/servo/ports/geckolib/binding_tools/regen.py b/servo/ports/geckolib/binding_tools/regen.py
index 88c423931d83..0d8a2514aae6 100755
--- a/servo/ports/geckolib/binding_tools/regen.py
+++ b/servo/ports/geckolib/binding_tools/regen.py
@@ -141,7 +141,8 @@ COMPILATION_TARGETS = {
             "nsStyleCoord::Calc", "nsRestyleHint", "ServoElementSnapshot",
             "nsChangeHint", "SheetParsingMode", "nsMainThreadPtrHandle",
             "nsMainThreadPtrHolder", "nscolor", "nsFont", "FontFamilyList",
-            "FontFamilyType", "nsIAtom", "nsStyleContext"
+            "FontFamilyType", "nsIAtom", "nsStyleContext", "StyleClipPath",
+            "StyleBasicShapeType", "StyleBasicShape"
         ],
         "void_types": [
             "nsINode", "nsIDocument", "nsIPrincipal", "nsIURI",
diff --git a/servo/ports/geckolib/gecko_bindings/bindings.rs b/servo/ports/geckolib/gecko_bindings/bindings.rs
index 1acaeb729252..3d03ab527c69 100644
--- a/servo/ports/geckolib/gecko_bindings/bindings.rs
+++ b/servo/ports/geckolib/gecko_bindings/bindings.rs
@@ -152,6 +152,9 @@ use structs::nsStyleContext;
 unsafe impl Send for nsStyleContext {}
 unsafe impl Sync for nsStyleContext {}
 impl HeapSizeOf for nsStyleContext { fn heap_size_of_children(&self) -> usize { 0 } }
+use structs::StyleClipPath;
+use structs::StyleBasicShapeType;
+use structs::StyleBasicShape;
 
 pub type RawGeckoNode = nsINode;
 pub enum Element { }
@@ -326,6 +329,11 @@ extern "C" {
     pub fn Gecko_SetStyleCoordCalcValue(unit: *mut nsStyleUnit,
                                         value: *mut nsStyleUnion,
                                         calc: CalcValue);
+    pub fn Gecko_CopyClipPathValueFrom(dst: *mut StyleClipPath,
+                                       src: *const StyleClipPath);
+    pub fn Gecko_DestroyClipPath(clip: *mut StyleClipPath);
+    pub fn Gecko_NewBasicShape(type_: StyleBasicShapeType)
+     -> *mut StyleBasicShape;
     pub fn Gecko_AddRefCalcArbitraryThread(aPtr: *mut Calc);
     pub fn Gecko_ReleaseCalcArbitraryThread(aPtr: *mut Calc);
     pub fn Servo_StylesheetFromUTF8Bytes(bytes: *const u8, length: u32,
diff --git a/servo/ports/geckolib/gecko_bindings/structs_debug.rs b/servo/ports/geckolib/gecko_bindings/structs_debug.rs
index 432fc55e86d1..d86c90fb298c 100644
--- a/servo/ports/geckolib/gecko_bindings/structs_debug.rs
+++ b/servo/ports/geckolib/gecko_bindings/structs_debug.rs
@@ -5452,7 +5452,7 @@ fn bindgen_test_layout_nsStyleSides() {
     assert_eq!(::std::mem::align_of::<nsStyleSides>() , 8usize);
 }
 /**
- * Class that represents a set of top-left/top-right/bottom-left/bottom-right
+ * Class that represents a set of top-left/top-right/bottom-right/bottom-left
  * nsStyleCoord pairs.  This is used to hold the dimensions of the
  * corners of a box (for, e.g., border-radius and outline-radius).
  */
@@ -6375,8 +6375,7 @@ fn bindgen_test_layout_StyleAnimation() {
 #[repr(C)]
 #[derive(Debug)]
 pub struct StyleBasicShape {
-    pub mRefCnt: nsAutoRefCnt,
-    pub _mOwningThread: nsAutoOwningThread,
+    pub mRefCnt: ThreadSafeAutoRefCnt,
     pub mType: StyleBasicShapeType,
     pub mFillRule: StyleFillRule,
     pub mCoordinates: nsTArray<nsStyleCoord>,
@@ -6385,7 +6384,7 @@ pub struct StyleBasicShape {
 }
 #[test]
 fn bindgen_test_layout_StyleBasicShape() {
-    assert_eq!(::std::mem::size_of::<StyleBasicShape>() , 128usize);
+    assert_eq!(::std::mem::size_of::<StyleBasicShape>() , 120usize);
     assert_eq!(::std::mem::align_of::<StyleBasicShape>() , 8usize);
 }
 #[repr(C)]
diff --git a/servo/ports/geckolib/gecko_bindings/structs_release.rs b/servo/ports/geckolib/gecko_bindings/structs_release.rs
index 30ae855567d7..755b0a02452f 100644
--- a/servo/ports/geckolib/gecko_bindings/structs_release.rs
+++ b/servo/ports/geckolib/gecko_bindings/structs_release.rs
@@ -5431,7 +5431,7 @@ fn bindgen_test_layout_nsStyleSides() {
     assert_eq!(::std::mem::align_of::<nsStyleSides>() , 8usize);
 }
 /**
- * Class that represents a set of top-left/top-right/bottom-left/bottom-right
+ * Class that represents a set of top-left/top-right/bottom-right/bottom-left
  * nsStyleCoord pairs.  This is used to hold the dimensions of the
  * corners of a box (for, e.g., border-radius and outline-radius).
  */
@@ -6353,8 +6353,7 @@ fn bindgen_test_layout_StyleAnimation() {
 #[repr(C)]
 #[derive(Debug)]
 pub struct StyleBasicShape {
-    pub mRefCnt: nsAutoRefCnt,
-    pub _mOwningThread: nsAutoOwningThread,
+    pub mRefCnt: ThreadSafeAutoRefCnt,
     pub mType: StyleBasicShapeType,
     pub mFillRule: StyleFillRule,
     pub mCoordinates: nsTArray<nsStyleCoord>,
@@ -6363,7 +6362,7 @@ pub struct StyleBasicShape {
 }
 #[test]
 fn bindgen_test_layout_StyleBasicShape() {
-    assert_eq!(::std::mem::size_of::<StyleBasicShape>() , 128usize);
+    assert_eq!(::std::mem::size_of::<StyleBasicShape>() , 120usize);
     assert_eq!(::std::mem::align_of::<StyleBasicShape>() , 8usize);
 }
 #[repr(C)]
diff --git a/servo/ports/geckolib/gecko_bindings/sugar/ns_style_coord.rs b/servo/ports/geckolib/gecko_bindings/sugar/ns_style_coord.rs
index a13f08ea37b8..74d20ff3a587 100644
--- a/servo/ports/geckolib/gecko_bindings/sugar/ns_style_coord.rs
+++ b/servo/ports/geckolib/gecko_bindings/sugar/ns_style_coord.rs
@@ -211,6 +211,17 @@ pub trait CoordDataMut : CoordData {
             *union = other.union();
     }
 
+    /// Useful for initializing uninits
+    /// (set_value may segfault on uninits)
+    fn leaky_set_null(&mut self) {
+        use structs::nsStyleUnit::*;
+        unsafe {
+            let (unit, union) = self.values_mut();
+            *unit = eStyleUnit_Null;
+            *union.mInt.as_mut() = 0;
+        }
+    }
+
     #[inline(always)]
     fn set_value(&mut self, value: CoordDataValue) {
         use self::CoordDataValue::*;
diff --git a/servo/ports/geckolib/string_cache/atom_macro.rs b/servo/ports/geckolib/string_cache/atom_macro.rs
index 18a493963729..e7ccfca12ad5 100644
--- a/servo/ports/geckolib/string_cache/atom_macro.rs
+++ b/servo/ports/geckolib/string_cache/atom_macro.rs
@@ -1172,6 +1172,8 @@ pub enum nsICSSAnonBoxPseudo {}
             pub static nsGkAtoms_minheight: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms13minimum_scaleE"]
             pub static nsGkAtoms_minimum_scale: *mut nsIAtom;
+            #[link_name = "_ZN9nsGkAtoms9minlengthE"]
+            pub static nsGkAtoms_minlength: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms6minposE"]
             pub static nsGkAtoms_minpos: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms9minusSignE"]
@@ -3838,6 +3840,8 @@ pub enum nsICSSAnonBoxPseudo {}
             pub static nsGkAtoms_onmozinterruptbegin: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms17onmozinterruptendE"]
             pub static nsGkAtoms_onmozinterruptend: *mut nsIAtom;
+            #[link_name = "_ZN9nsGkAtoms14ondevicechangeE"]
+            pub static nsGkAtoms_ondevicechange: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms12cdataTagNameE"]
             pub static nsGkAtoms_cdataTagName: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms14commentTagNameE"]
@@ -6083,6 +6087,8 @@ pub enum nsICSSAnonBoxPseudo {}
             pub static nsGkAtoms_minheight: *mut nsIAtom;
             #[link_name = "?minimum_scale@nsGkAtoms@@2PEAVnsIAtom@@EA"]
             pub static nsGkAtoms_minimum_scale: *mut nsIAtom;
+            #[link_name = "?minlength@nsGkAtoms@@2PEAVnsIAtom@@EA"]
+            pub static nsGkAtoms_minlength: *mut nsIAtom;
             #[link_name = "?minpos@nsGkAtoms@@2PEAVnsIAtom@@EA"]
             pub static nsGkAtoms_minpos: *mut nsIAtom;
             #[link_name = "?minusSign@nsGkAtoms@@2PEAVnsIAtom@@EA"]
@@ -8749,6 +8755,8 @@ pub enum nsICSSAnonBoxPseudo {}
             pub static nsGkAtoms_onmozinterruptbegin: *mut nsIAtom;
             #[link_name = "?onmozinterruptend@nsGkAtoms@@2PEAVnsIAtom@@EA"]
             pub static nsGkAtoms_onmozinterruptend: *mut nsIAtom;
+            #[link_name = "?ondevicechange@nsGkAtoms@@2PEAVnsIAtom@@EA"]
+            pub static nsGkAtoms_ondevicechange: *mut nsIAtom;
             #[link_name = "?cdataTagName@nsGkAtoms@@2PEAVnsIAtom@@EA"]
             pub static nsGkAtoms_cdataTagName: *mut nsIAtom;
             #[link_name = "?commentTagName@nsGkAtoms@@2PEAVnsIAtom@@EA"]
@@ -10994,6 +11002,8 @@ pub enum nsICSSAnonBoxPseudo {}
             pub static nsGkAtoms_minheight: *mut nsIAtom;
             #[link_name = "?minimum_scale@nsGkAtoms@@2PAVnsIAtom@@A"]
             pub static nsGkAtoms_minimum_scale: *mut nsIAtom;
+            #[link_name = "?minlength@nsGkAtoms@@2PAVnsIAtom@@A"]
+            pub static nsGkAtoms_minlength: *mut nsIAtom;
             #[link_name = "?minpos@nsGkAtoms@@2PAVnsIAtom@@A"]
             pub static nsGkAtoms_minpos: *mut nsIAtom;
             #[link_name = "?minusSign@nsGkAtoms@@2PAVnsIAtom@@A"]
@@ -13660,6 +13670,8 @@ pub enum nsICSSAnonBoxPseudo {}
             pub static nsGkAtoms_onmozinterruptbegin: *mut nsIAtom;
             #[link_name = "?onmozinterruptend@nsGkAtoms@@2PAVnsIAtom@@A"]
             pub static nsGkAtoms_onmozinterruptend: *mut nsIAtom;
+            #[link_name = "?ondevicechange@nsGkAtoms@@2PAVnsIAtom@@A"]
+            pub static nsGkAtoms_ondevicechange: *mut nsIAtom;
             #[link_name = "?cdataTagName@nsGkAtoms@@2PAVnsIAtom@@A"]
             pub static nsGkAtoms_cdataTagName: *mut nsIAtom;
             #[link_name = "?commentTagName@nsGkAtoms@@2PAVnsIAtom@@A"]
@@ -15332,6 +15344,7 @@ macro_rules! atom {
 ("min") => { $crate::atom_macro::unsafe_atom_from_static($crate::atom_macro::nsGkAtoms_min as *mut _) };
 ("minheight") => { $crate::atom_macro::unsafe_atom_from_static($crate::atom_macro::nsGkAtoms_minheight as *mut _) };
 ("minimum-scale") => { $crate::atom_macro::unsafe_atom_from_static($crate::atom_macro::nsGkAtoms_minimum_scale as *mut _) };
+("minlength") => { $crate::atom_macro::unsafe_atom_from_static($crate::atom_macro::nsGkAtoms_minlength as *mut _) };
 ("minpos") => { $crate::atom_macro::unsafe_atom_from_static($crate::atom_macro::nsGkAtoms_minpos as *mut _) };
 ("minus-sign") => { $crate::atom_macro::unsafe_atom_from_static($crate::atom_macro::nsGkAtoms_minusSign as *mut _) };
 ("minwidth") => { $crate::atom_macro::unsafe_atom_from_static($crate::atom_macro::nsGkAtoms_minwidth as *mut _) };
@@ -16665,6 +16678,7 @@ macro_rules! atom {
 ("ondevicelight") => { $crate::atom_macro::unsafe_atom_from_static($crate::atom_macro::nsGkAtoms_ondevicelight as *mut _) };
 ("onmozinterruptbegin") => { $crate::atom_macro::unsafe_atom_from_static($crate::atom_macro::nsGkAtoms_onmozinterruptbegin as *mut _) };
 ("onmozinterruptend") => { $crate::atom_macro::unsafe_atom_from_static($crate::atom_macro::nsGkAtoms_onmozinterruptend as *mut _) };
+("ondevicechange") => { $crate::atom_macro::unsafe_atom_from_static($crate::atom_macro::nsGkAtoms_ondevicechange as *mut _) };
 ("#cdata-section") => { $crate::atom_macro::unsafe_atom_from_static($crate::atom_macro::nsGkAtoms_cdataTagName as *mut _) };
 ("#comment") => { $crate::atom_macro::unsafe_atom_from_static($crate::atom_macro::nsGkAtoms_commentTagName as *mut _) };
 ("#document") => { $crate::atom_macro::unsafe_atom_from_static($crate::atom_macro::nsGkAtoms_documentNodeName as *mut _) };
diff --git a/servo/tests/unit/style/parsing/basic_shape.rs b/servo/tests/unit/style/parsing/basic_shape.rs
index b3702dfc8cd8..62755582b377 100644
--- a/servo/tests/unit/style/parsing/basic_shape.rs
+++ b/servo/tests/unit/style/parsing/basic_shape.rs
@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use parsing::parse;
+use style::parser::Parse;
 use style::values::specified::basic_shape::*;
 
 // Ensure that basic-shape sub-functions parse as both basic shapes