Auto merge of #22930 - emilio:gecko-sync, r=emilio

style: Sync changes from mozilla-central.

See individual commits for details.

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72 files changed, 845 insertions, 1174 deletions

diff --git a/components/layout/display_list/background.rs b/components/layout/display_list/background.rs
index 368818471d5..c6fa1691e46 100644
--- a/components/layout/display_list/background.rs
+++ b/components/layout/display_list/background.rs
@@ -2,8 +2,6 @@
  * 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/. */
 
-// FIXME(rust-lang/rust#26264): Remove GenericBackgroundSize.
-
 use crate::display_list::border;
 use app_units::Au;
 use euclid::{Point2D, Rect, SideOffsets2D, Size2D};
@@ -12,7 +10,6 @@ use style::computed_values::background_clip::single_value::T as BackgroundClip;
 use style::computed_values::background_origin::single_value::T as BackgroundOrigin;
 use style::properties::style_structs::Background;
 use style::values::computed::{BackgroundSize, NonNegativeLengthPercentageOrAuto};
-use style::values::generics::background::BackgroundSize as GenericBackgroundSize;
 use style::values::specified::background::BackgroundRepeatKeyword;
 use webrender_api::BorderRadius;
 
@@ -56,8 +53,8 @@ fn compute_background_image_size(
 ) -> Size2D<Au> {
     match intrinsic_size {
         None => match bg_size {
-            GenericBackgroundSize::Cover | GenericBackgroundSize::Contain => bounds_size,
-            GenericBackgroundSize::Explicit { width, height } => Size2D::new(
+            BackgroundSize::Cover | BackgroundSize::Contain => bounds_size,
+            BackgroundSize::ExplicitSize { width, height } => Size2D::new(
                 width
                     .to_used_value(bounds_size.width)
                     .unwrap_or(bounds_size.width),
@@ -73,20 +70,16 @@ fn compute_background_image_size(
             let bounds_aspect_ratio =
                 bounds_size.width.to_f32_px() / bounds_size.height.to_f32_px();
             match (bg_size, image_aspect_ratio < bounds_aspect_ratio) {
-                (GenericBackgroundSize::Contain, false) | (GenericBackgroundSize::Cover, true) => {
-                    Size2D::new(
-                        bounds_size.width,
-                        bounds_size.width.scale_by(image_aspect_ratio.recip()),
-                    )
-                },
-                (GenericBackgroundSize::Contain, true) | (GenericBackgroundSize::Cover, false) => {
-                    Size2D::new(
-                        bounds_size.height.scale_by(image_aspect_ratio),
-                        bounds_size.height,
-                    )
-                },
+                (BackgroundSize::Contain, false) | (BackgroundSize::Cover, true) => Size2D::new(
+                    bounds_size.width,
+                    bounds_size.width.scale_by(image_aspect_ratio.recip()),
+                ),
+                (BackgroundSize::Contain, true) | (BackgroundSize::Cover, false) => Size2D::new(
+                    bounds_size.height.scale_by(image_aspect_ratio),
+                    bounds_size.height,
+                ),
                 (
-                    GenericBackgroundSize::Explicit {
+                    BackgroundSize::ExplicitSize {
                         width,
                         height: NonNegativeLengthPercentageOrAuto::Auto,
                     },
@@ -98,7 +91,7 @@ fn compute_background_image_size(
                     Size2D::new(width, width.scale_by(image_aspect_ratio.recip()))
                 },
                 (
-                    GenericBackgroundSize::Explicit {
+                    BackgroundSize::ExplicitSize {
                         width: NonNegativeLengthPercentageOrAuto::Auto,
                         height,
                     },
@@ -109,7 +102,7 @@ fn compute_background_image_size(
                         .unwrap_or(own_size.height);
                     Size2D::new(height.scale_by(image_aspect_ratio), height)
                 },
-                (GenericBackgroundSize::Explicit { width, height }, _) => Size2D::new(
+                (BackgroundSize::ExplicitSize { width, height }, _) => Size2D::new(
                     width
                         .to_used_value(bounds_size.width)
                         .unwrap_or(own_size.width),
diff --git a/components/layout/display_list/border.rs b/components/layout/display_list/border.rs
index d5909abee84..dcbef4473fe 100644
--- a/components/layout/display_list/border.rs
+++ b/components/layout/display_list/border.rs
@@ -2,8 +2,6 @@
  * 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/. */
 
-// FIXME(rust-lang/rust#26264): Remove GenericBorderImageSideWidth.
-
 use crate::display_list::ToLayout;
 use app_units::Au;
 use euclid::{Rect, SideOffsets2D, Size2D};
@@ -11,11 +9,9 @@ use style::computed_values::border_image_outset::T as BorderImageOutset;
 use style::properties::style_structs::Border;
 use style::values::computed::NumberOrPercentage;
 use style::values::computed::{BorderCornerRadius, BorderImageWidth};
-use style::values::computed::{BorderImageSideWidth, LengthOrNumber};
-use style::values::generics::border::BorderImageSideWidth as GenericBorderImageSideWidth;
+use style::values::computed::{BorderImageSideWidth, NonNegativeLengthOrNumber};
 use style::values::generics::rect::Rect as StyleRect;
 use style::values::generics::NonNegative;
-use style::values::Either;
 use webrender_api::{BorderRadius, BorderSide, BorderStyle, ColorF};
 use webrender_api::{LayoutSideOffsets, LayoutSize, NormalBorder};
 
@@ -140,10 +136,10 @@ pub fn simple(color: ColorF, style: BorderStyle) -> NormalBorder {
     }
 }
 
-fn side_image_outset(outset: LengthOrNumber, border_width: Au) -> Au {
+fn side_image_outset(outset: NonNegativeLengthOrNumber, border_width: Au) -> Au {
     match outset {
-        Either::First(length) => length.into(),
-        Either::Second(factor) => border_width.scale_by(factor),
+        NonNegativeLengthOrNumber::Length(length) => length.into(),
+        NonNegativeLengthOrNumber::Number(factor) => border_width.scale_by(factor.0),
     }
 }
 
@@ -163,9 +159,9 @@ fn side_image_width(
     total_length: Au,
 ) -> f32 {
     match border_image_width {
-        GenericBorderImageSideWidth::Length(v) => v.to_used_value(total_length).to_f32_px(),
-        GenericBorderImageSideWidth::Number(x) => border_width * x.0,
-        GenericBorderImageSideWidth::Auto => border_width,
+        BorderImageSideWidth::Length(v) => v.to_used_value(total_length).to_f32_px(),
+        BorderImageSideWidth::Number(x) => border_width * x.0,
+        BorderImageSideWidth::Auto => border_width,
     }
 }
 
diff --git a/components/layout/display_list/builder.rs b/components/layout/display_list/builder.rs
index 6de5ac8498c..d26cd6b9c32 100644
--- a/components/layout/display_list/builder.rs
+++ b/components/layout/display_list/builder.rs
@@ -763,7 +763,7 @@ impl Fragment {
                     let background_size =
                         get_cyclic(&style.get_background().background_size.0, i).clone();
                     let size = match background_size {
-                        BackgroundSize::Explicit { width, height } => Size2D::new(
+                        BackgroundSize::ExplicitSize { width, height } => Size2D::new(
                             width
                                 .to_used_value(bounding_box_size.width)
                                 .unwrap_or(bounding_box_size.width),
diff --git a/components/layout/flex.rs b/components/layout/flex.rs
index f761bc95dff..82dd9533175 100644
--- a/components/layout/flex.rs
+++ b/components/layout/flex.rs
@@ -30,7 +30,6 @@ use style::properties::ComputedValues;
 use style::servo::restyle_damage::ServoRestyleDamage;
 use style::values::computed::flex::FlexBasis;
 use style::values::computed::{MaxSize, Size};
-use style::values::generics::flex::FlexBasis as GenericFlexBasis;
 
 /// The size of an axis. May be a specified size, a min/max
 /// constraint, or an unlimited size
@@ -61,8 +60,8 @@ impl AxisSize {
 /// is definite after flex size resolving.
 fn from_flex_basis(flex_basis: FlexBasis, main_length: Size, containing_length: Au) -> MaybeAuto {
     let width = match flex_basis {
-        GenericFlexBasis::Content => return MaybeAuto::Auto,
-        GenericFlexBasis::Width(width) => width,
+        FlexBasis::Content => return MaybeAuto::Auto,
+        FlexBasis::Size(width) => width,
     };
 
     let width = match width {
diff --git a/components/style/cbindgen.toml b/components/style/cbindgen.toml
index 4c0b631d31d..0b8719c4dbf 100644
--- a/components/style/cbindgen.toml
+++ b/components/style/cbindgen.toml
@@ -57,6 +57,7 @@ include = [
   "CursorKind",
   "Display",
   "DisplayMode",
+  "PrefersColorScheme",
   "ExtremumLength",
   "FillRule",
   "FontDisplay",
@@ -69,6 +70,7 @@ include = [
   "UserSelect",
   "Float",
   "OverscrollBehavior",
+  "ScrollSnapAlign",
   "ScrollSnapType",
   "OverflowAnchor",
   "OverflowClipBox",
@@ -77,32 +79,97 @@ include = [
   "LengthPercentage",
   "NonNegativeLengthPercentage",
   "LengthPercentageOrAuto",
+  "NonNegativeLengthPercentageOrAuto",
   "Rect",
   "IntersectionObserverRootMargin",
+  "Size",
+  "MaxSize",
+  "FlexBasis",
+  "Position",
+  "BackgroundSize",
+  "BorderImageSlice",
+  "NonNegativeLengthOrNumberRect",
+  "Perspective",
+  "ZIndex",
+  "TransformOrigin",
 ]
 item_types = ["enums", "structs", "typedefs"]
 
 [export.body]
+"CSSPixelLength" = """
+  inline nscoord ToAppUnits() const;
+"""
+
 "LengthPercentage" = """
   // Defined in nsStyleCoord.h
   static constexpr inline StyleLengthPercentage Zero();
+  static inline StyleLengthPercentage FromAppUnits(nscoord);
+  static inline StyleLengthPercentage FromPixels(CSSCoord);
+  static inline StyleLengthPercentage FromPercentage(float);
+  inline CSSCoord LengthInCSSPixels() const;
+  inline float Percentage() const;
   inline bool HasPercent() const;
   inline bool ConvertsToLength() const;
   inline nscoord ToLength() const;
   inline bool ConvertsToPercentage() const;
+  inline bool HasLengthAndPercentage() const;
   inline float ToPercentage() const;
-  inline CSSCoord LengthInCSSPixels() const;
-  inline float Percentage() const;
   inline CSSCoord ResolveToCSSPixels(CSSCoord aPercentageBasisInCSSPixels) const;
   template<typename T> inline CSSCoord ResolveToCSSPixelsWith(T aPercentageGetter) const;
+  template<typename T, typename U>
+  inline nscoord Resolve(T aPercentageGetter, U aPercentRoundingFunction) const;
+  template<typename T>
+  inline nscoord Resolve(nscoord aPercentageBasis, T aPercentRoundingFunction) const;
+  template<typename T> inline nscoord Resolve(T aPercentageGetter) const;
   inline nscoord Resolve(nscoord aPercentageBasis) const;
-  template<typename T> inline nscoord ResolveWith(T aPercentageGetter) const;
 """
 
 "GenericLengthPercentageOrAuto" = """
   inline const StyleLengthPercentage& AsLengthPercentage() const;
+  inline bool ConvertsToLength() const;
+  inline nscoord ToLength() const;
+  inline bool ConvertsToPercentage() const;
+  inline float ToPercentage() const;
   inline bool HasPercent() const;
+  inline bool HasLengthAndPercentage() const;
+"""
+
+"GenericSize" = """
+  inline const StyleLengthPercentage& AsLengthPercentage() const;
+  inline StyleExtremumLength AsExtremumLength() const;
   inline bool ConvertsToLength() const;
+  inline nscoord ToLength() const;
+  inline bool ConvertsToPercentage() const;
+  inline float ToPercentage() const;
+  inline bool HasPercent() const;
+  inline bool HasLengthAndPercentage() const;
+  inline bool BehavesLikeInitialValueOnBlockAxis() const;
+"""
+
+"GenericFlexBasis" = """
+  inline bool IsAuto() const;
+  inline const StyleSize& AsSize() const;
+"""
+
+"GenericMaxSize" = """
+  inline const StyleLengthPercentage& AsLengthPercentage() const;
+  inline StyleExtremumLength AsExtremumLength() const;
+  inline bool ConvertsToLength() const;
+  inline nscoord ToLength() const;
+  inline bool ConvertsToPercentage() const;
+  inline float ToPercentage() const;
+  inline bool HasPercent() const;
+  inline bool HasLengthAndPercentage() const;
+  inline bool BehavesLikeInitialValueOnBlockAxis() const;
+"""
+
+"GenericPosition" = """
+  inline bool DependsOnPositioningAreaSize() const;
+  static inline StyleGenericPosition FromPercentage(float);
+"""
+
+"GenericBackgroundSize" = """
+  bool IsInitialValue() const;
 """
 
 "Rect" = """
diff --git a/components/style/gecko/conversions.rs b/components/style/gecko/conversions.rs
index ccaa16c844c..2a2ae268395 100644
--- a/components/style/gecko/conversions.rs
+++ b/components/style/gecko/conversions.rs
@@ -23,13 +23,10 @@ use crate::values::computed::url::ComputedImageUrl;
 use crate::values::computed::{Angle, Gradient, Image};
 use crate::values::computed::{Integer, LengthPercentage};
 use crate::values::computed::{Length, Percentage, TextAlign};
-use crate::values::computed::{LengthPercentageOrAuto, NonNegativeLengthPercentageOrAuto};
 use crate::values::generics::box_::VerticalAlign;
 use crate::values::generics::grid::{TrackListValue, TrackSize};
 use crate::values::generics::image::{CompatMode, GradientItem, Image as GenericImage};
-use crate::values::generics::length::LengthPercentageOrAuto as GenericLengthPercentageOrAuto;
 use crate::values::generics::rect::Rect;
-use crate::values::generics::NonNegative;
 use app_units::Au;
 use std::f32::consts::PI;
 use style_traits::values::specified::AllowedNumericType;
@@ -62,42 +59,6 @@ impl From<nsStyleCoord_CalcValue> for LengthPercentage {
         )
     }
 }
-
-impl NonNegativeLengthPercentageOrAuto {
-    /// Convert this value in an appropriate `nsStyleCoord::CalcValue`.
-    pub fn to_calc_value(&self) -> Option<nsStyleCoord_CalcValue> {
-        match *self {
-            GenericLengthPercentageOrAuto::LengthPercentage(ref len) => Some(From::from(len.0)),
-            GenericLengthPercentageOrAuto::Auto => None,
-        }
-    }
-}
-
-impl From<nsStyleCoord_CalcValue> for LengthPercentageOrAuto {
-    fn from(other: nsStyleCoord_CalcValue) -> LengthPercentageOrAuto {
-        GenericLengthPercentageOrAuto::LengthPercentage(LengthPercentage::from(other))
-    }
-}
-
-// FIXME(emilio): A lot of these impl From should probably become explicit or
-// disappear as we move more stuff to cbindgen.
-impl From<nsStyleCoord_CalcValue> for NonNegativeLengthPercentageOrAuto {
-    fn from(other: nsStyleCoord_CalcValue) -> Self {
-        GenericLengthPercentageOrAuto::LengthPercentage(NonNegative(
-            LengthPercentage::with_clamping_mode(
-                Au(other.mLength).into(),
-                if other.mHasPercent {
-                    Some(Percentage(other.mPercent))
-                } else {
-                    None
-                },
-                AllowedNumericType::NonNegative,
-                /* was_calc = */ true,
-            ),
-        ))
-    }
-}
-
 impl From<Angle> for CoordDataValue {
     fn from(reference: Angle) -> Self {
         CoordDataValue::Degree(reference.degrees())
@@ -614,7 +575,6 @@ pub mod basic_shape {
     //! Conversions from and to CSS shape representations.
 
     use crate::gecko::values::GeckoStyleCoordConvertible;
-    use crate::gecko_bindings::structs;
     use crate::gecko_bindings::structs::{nsStyleCoord, nsStyleCorners};
     use crate::gecko_bindings::structs::{StyleBasicShape, StyleBasicShapeType};
     use crate::gecko_bindings::structs::{
@@ -628,7 +588,6 @@ pub mod basic_shape {
     use crate::values::computed::border::{BorderCornerRadius, BorderRadius};
     use crate::values::computed::length::LengthPercentage;
     use crate::values::computed::motion::OffsetPath;
-    use crate::values::computed::position;
     use crate::values::computed::url::ComputedUrl;
     use crate::values::generics::basic_shape::{
         BasicShape as GenericBasicShape, InsetRect, Polygon,
@@ -759,12 +718,12 @@ pub mod basic_shape {
                 },
                 StyleBasicShapeType::Circle => GenericBasicShape::Circle(Circle {
                     radius: (&other.mCoordinates[0]).into(),
-                    position: (&other.mPosition).into(),
+                    position: other.mPosition,
                 }),
                 StyleBasicShapeType::Ellipse => GenericBasicShape::Ellipse(Ellipse {
                     semiaxis_x: (&other.mCoordinates[0]).into(),
                     semiaxis_y: (&other.mCoordinates[1]).into(),
-                    position: (&other.mPosition).into(),
+                    position: other.mPosition,
                 }),
                 StyleBasicShapeType::Polygon => {
                     let mut coords = Vec::with_capacity(other.mCoordinates.len() / 2);
@@ -852,17 +811,6 @@ pub mod basic_shape {
         }
     }
 
-    // Can't be a From impl since we need to set an existing
-    // Position, not create a new one
-    impl From<position::Position> for structs::Position {
-        fn from(other: position::Position) -> Self {
-            structs::Position {
-                mXPosition: other.horizontal.into(),
-                mYPosition: other.vertical.into(),
-            }
-        }
-    }
-
     impl<'a> From<&'a nsStyleCoord> for ShapeRadius {
         fn from(other: &'a nsStyleCoord) -> Self {
             let other = other.borrow();
@@ -871,15 +819,6 @@ pub mod basic_shape {
         }
     }
 
-    impl<'a> From<&'a structs::Position> for position::Position {
-        fn from(other: &'a structs::Position) -> Self {
-            position::Position {
-                horizontal: other.mXPosition.into(),
-                vertical: other.mYPosition.into(),
-            }
-        }
-    }
-
     impl From<ShapeBox> for StyleGeometryBox {
         fn from(reference: ShapeBox) -> Self {
             use crate::gecko_bindings::structs::StyleGeometryBox::*;
diff --git a/components/style/gecko/media_features.rs b/components/style/gecko/media_features.rs
index b6596c75de8..2547f2a45d4 100644
--- a/components/style/gecko/media_features.rs
+++ b/components/style/gecko/media_features.rs
@@ -280,6 +280,16 @@ enum PrefersReducedMotion {
     Reduce,
 }
 
+/// Values for the prefers-color-scheme media feature.
+#[derive(Clone, Copy, Debug, FromPrimitive, Parse, PartialEq, ToCss)]
+#[repr(u8)]
+#[allow(missing_docs)]
+pub enum PrefersColorScheme {
+    Light,
+    Dark,
+    NoPreference,
+}
+
 /// https://drafts.csswg.org/mediaqueries-5/#prefers-reduced-motion
 fn eval_prefers_reduced_motion(device: &Device, query_value: Option<PrefersReducedMotion>) -> bool {
     let prefers_reduced =
@@ -348,6 +358,16 @@ fn eval_overflow_inline(device: &Device, query_value: Option<OverflowInline>) ->
     }
 }
 
+/// https://drafts.csswg.org/mediaqueries-5/#prefers-color-scheme
+fn eval_prefers_color_scheme(device: &Device, query_value: Option<PrefersColorScheme>) -> bool {
+    let prefers_color_scheme =
+        unsafe { bindings::Gecko_MediaFeatures_PrefersColorScheme(device.document()) };
+    match query_value {
+        Some(v) => prefers_color_scheme == v,
+        None => prefers_color_scheme != PrefersColorScheme::NoPreference,
+    }
+}
+
 /// https://drafts.csswg.org/mediaqueries-4/#mf-interaction
 bitflags! {
     struct PointerCapabilities: u8 {
@@ -441,7 +461,7 @@ fn eval_moz_is_glyph(
     query_value: Option<bool>,
     _: Option<RangeOrOperator>,
 ) -> bool {
-    let is_glyph = unsafe { (*device.document()).mIsSVGGlyphsDocument() };
+    let is_glyph = device.document().mIsSVGGlyphsDocument();
     query_value.map_or(is_glyph, |v| v == is_glyph)
 }
 
@@ -526,7 +546,7 @@ lazy_static! {
     /// to support new types in these entries and (2) ensuring that either
     /// nsPresContext::MediaFeatureValuesChanged is called when the value that
     /// would be returned by the evaluator function could change.
-    pub static ref MEDIA_FEATURES: [MediaFeatureDescription; 52] = [
+    pub static ref MEDIA_FEATURES: [MediaFeatureDescription; 53] = [
         feature!(
             atom!("width"),
             AllowsRanges::Yes,
@@ -658,6 +678,12 @@ lazy_static! {
             ParsingRequirements::empty(),
         ),
         feature!(
+            atom!("prefers-color-scheme"),
+            AllowsRanges::No,
+            keyword_evaluator!(eval_prefers_color_scheme, PrefersColorScheme),
+            ParsingRequirements::empty(),
+        ),
+        feature!(
             atom!("pointer"),
             AllowsRanges::No,
             keyword_evaluator!(eval_pointer, Pointer),
diff --git a/components/style/gecko/media_queries.rs b/components/style/gecko/media_queries.rs
index 851422467ce..8fa2258eaaf 100644
--- a/components/style/gecko/media_queries.rs
+++ b/components/style/gecko/media_queries.rs
@@ -85,7 +85,9 @@ impl Device {
         assert!(!pres_context.is_null());
         Device {
             pres_context,
-            default_values: ComputedValues::default_values(unsafe { &*pres_context }),
+            default_values: ComputedValues::default_values(unsafe {
+                &*(*pres_context).mDocument.mRawPtr
+            }),
             // FIXME(bz): Seems dubious?
             root_font_size: AtomicIsize::new(FontSize::medium().size().0 as isize),
             body_text_color: AtomicUsize::new(unsafe { &*pres_context }.mDefaultColor as usize),
@@ -162,13 +164,13 @@ impl Device {
 
     /// Gets the document pointer.
     #[inline]
-    pub fn document(&self) -> *mut structs::Document {
-        self.pres_context().mDocument.mRawPtr
+    pub fn document(&self) -> &structs::Document {
+        unsafe { &*self.pres_context().mDocument.mRawPtr }
     }
 
     /// Recreates the default computed values.
     pub fn reset_computed_values(&mut self) {
-        self.default_values = ComputedValues::default_values(self.pres_context());
+        self.default_values = ComputedValues::default_values(self.document());
     }
 
     /// Rebuild all the cached data.
diff --git a/components/style/gecko/pseudo_element.rs b/components/style/gecko/pseudo_element.rs
index ae314ee3d6d..8160ea2c9b8 100644
--- a/components/style/gecko/pseudo_element.rs
+++ b/components/style/gecko/pseudo_element.rs
@@ -8,7 +8,7 @@
 //! `pseudo_element_definition.mako.rs`. If you touch that file, you probably
 //! need to update the checked-in files for Servo.
 
-use crate::gecko_bindings::structs::{self, CSSPseudoElementType};
+use crate::gecko_bindings::structs::{self, PseudoStyleType};
 use crate::properties::longhands::display::computed_value::T as Display;
 use crate::properties::{ComputedValues, PropertyFlags};
 use crate::selector_parser::{NonTSPseudoClass, PseudoElementCascadeType, SelectorImpl};
diff --git a/components/style/gecko/pseudo_element_definition.mako.rs b/components/style/gecko/pseudo_element_definition.mako.rs
index 613bbd281ee..be156b54a14 100644
--- a/components/style/gecko/pseudo_element_definition.mako.rs
+++ b/components/style/gecko/pseudo_element_definition.mako.rs
@@ -48,17 +48,6 @@ PseudoElement::${pseudo.capitalized_pseudo()}${"({})".format(tree_arg) if pseudo
 </%def>
 
 impl PseudoElement {
-    /// Get the pseudo-element as an atom.
-    #[inline]
-    fn atom(&self) -> Atom {
-        match *self {
-            % for pseudo in PSEUDOS:
-                ${pseudo_element_variant(pseudo)} => atom!("${pseudo.value}"),
-            % endfor
-            PseudoElement::UnknownWebkit(..) => unreachable!(),
-        }
-    }
-
     /// Returns an index of the pseudo-element.
     #[inline]
     pub fn index(&self) -> usize {
@@ -138,45 +127,36 @@ impl PseudoElement {
         }
     }
 
-    /// Construct a pseudo-element from a `CSSPseudoElementType`.
+    /// Construct a pseudo-element from a `PseudoStyleType`.
     #[inline]
-    pub fn from_pseudo_type(type_: CSSPseudoElementType) -> Option<Self> {
+    pub fn from_pseudo_type(type_: PseudoStyleType) -> Option<Self> {
         match type_ {
             % for pseudo in PSEUDOS:
-                % if not pseudo.is_anon_box():
-                    CSSPseudoElementType::${pseudo.pseudo_ident} => {
-                        Some(${pseudo_element_variant(pseudo)})
-                    },
-                % endif
+            % if not pseudo.is_tree_pseudo_element():
+                PseudoStyleType::${pseudo.pseudo_ident} => {
+                    Some(${pseudo_element_variant(pseudo)})
+                },
+            % endif
             % endfor
             _ => None,
         }
     }
 
-    /// Construct a `CSSPseudoElementType` from a pseudo-element
+    /// Construct a `PseudoStyleType` from a pseudo-element
     #[inline]
-    fn pseudo_type(&self) -> CSSPseudoElementType {
+    pub fn pseudo_type(&self) -> PseudoStyleType {
         match *self {
             % for pseudo in PSEUDOS:
-                % if not pseudo.is_anon_box():
-                    PseudoElement::${pseudo.capitalized_pseudo()} => CSSPseudoElementType::${pseudo.pseudo_ident},
-                % elif pseudo.is_tree_pseudo_element():
-                    PseudoElement::${pseudo.capitalized_pseudo()}(..) => CSSPseudoElementType::XULTree,
-                % elif pseudo.is_inheriting_anon_box():
-                    PseudoElement::${pseudo.capitalized_pseudo()} => CSSPseudoElementType::InheritingAnonBox,
-                % else:
-                    PseudoElement::${pseudo.capitalized_pseudo()} => CSSPseudoElementType::NonInheritingAnonBox,
-                % endif
+            % if pseudo.is_tree_pseudo_element():
+                PseudoElement::${pseudo.capitalized_pseudo()}(..) => PseudoStyleType::XULTree,
+            % else:
+                PseudoElement::${pseudo.capitalized_pseudo()} => PseudoStyleType::${pseudo.pseudo_ident},
+            % endif
             % endfor
             PseudoElement::UnknownWebkit(..) => unreachable!(),
         }
     }
 
-    /// Get a PseudoInfo for a pseudo
-    pub fn pseudo_info(&self) -> (*mut structs::nsAtom, CSSPseudoElementType) {
-        (self.atom().as_ptr(), self.pseudo_type())
-    }
-
     /// Get the argument list of a tree pseudo-element.
     #[inline]
     pub fn tree_pseudo_args(&self) -> Option<<&[Atom]> {
@@ -188,45 +168,15 @@ impl PseudoElement {
         }
     }
 
-    /// Construct a pseudo-element from an `Atom`.
-    #[inline]
-    pub fn from_atom(atom: &Atom) -> Option<Self> {
-        % for pseudo in PSEUDOS:
-            % if pseudo.is_tree_pseudo_element():
-                // We cannot generate ${pseudo_element_variant(pseudo)} from just an atom.
-            % else:
-                if atom == &atom!("${pseudo.value}") {
-                    return Some(${pseudo_element_variant(pseudo)});
-                }
-            % endif
-        % endfor
-        None
-    }
-
-    /// Construct a pseudo-element from an anonymous box `Atom`.
-    #[inline]
-    pub fn from_anon_box_atom(atom: &Atom) -> Option<Self> {
-        % for pseudo in PSEUDOS:
-            % if pseudo.is_tree_pseudo_element():
-                // We cannot generate ${pseudo_element_variant(pseudo)} from just an atom.
-            % elif pseudo.is_anon_box():
-                if atom == &atom!("${pseudo.value}") {
-                    return Some(${pseudo_element_variant(pseudo)});
-                }
-            % endif
-        % endfor
-        None
-    }
-
     /// Construct a tree pseudo-element from atom and args.
     #[inline]
     pub fn from_tree_pseudo_atom(atom: &Atom, args: Box<[Atom]>) -> Option<Self> {
         % for pseudo in PSEUDOS:
-            % if pseudo.is_tree_pseudo_element():
-                if atom == &atom!("${pseudo.value}") {
-                    return Some(PseudoElement::${pseudo.capitalized_pseudo()}(args.into()));
-                }
-            % endif
+        % if pseudo.is_tree_pseudo_element():
+            if atom == &atom!("${pseudo.value}") {
+                return Some(PseudoElement::${pseudo.capitalized_pseudo()}(args.into()));
+            }
+        % endif
         % endfor
         None
     }
diff --git a/components/style/gecko/regen_atoms.py b/components/style/gecko/regen_atoms.py
index b6f68fceb7d..0066d06d054 100755
--- a/components/style/gecko/regen_atoms.py
+++ b/components/style/gecko/regen_atoms.py
@@ -41,8 +41,10 @@ class Atom:
         # The type of atom: "Atom", "PseudoElement", "NonInheritingAnonBox",
         # or "InheritingAnonBox".
         self.atom_type = atom_type
-        if self.is_pseudo() or self.is_anon_box():
+
+        if self.is_pseudo_element() or self.is_anon_box() or self.is_tree_pseudo_element():
             self.pseudo_ident = (ident.split("_", 1))[1]
+
         if self.is_anon_box():
             assert self.is_inheriting_anon_box() or self.is_non_inheriting_anon_box()
 
@@ -52,16 +54,21 @@ class Atom:
     def capitalized_pseudo(self):
         return self.pseudo_ident[0].upper() + self.pseudo_ident[1:]
 
-    def is_pseudo(self):
+    def is_pseudo_element(self):
         return self.atom_type == "PseudoElementAtom"
 
     def is_anon_box(self):
+        if self.is_tree_pseudo_element():
+            return False
         return self.is_non_inheriting_anon_box() or self.is_inheriting_anon_box()
 
     def is_non_inheriting_anon_box(self):
+        assert not self.is_tree_pseudo_element()
         return self.atom_type == "NonInheritingAnonBoxAtom"
 
     def is_inheriting_anon_box(self):
+        if self.is_tree_pseudo_element():
+            return False
         return self.atom_type == "InheritingAnonBoxAtom"
 
     def is_tree_pseudo_element(self):
diff --git a/components/style/gecko/values.rs b/components/style/gecko/values.rs
index 33706f70537..fa1c7d1f6d3 100644
--- a/components/style/gecko/values.rs
+++ b/components/style/gecko/values.rs
@@ -7,22 +7,16 @@
 //! Different kind of helpers to interact with Gecko values.
 
 use crate::counter_style::{Symbol, Symbols};
-use crate::gecko_bindings::structs::{self, nsStyleCoord, CounterStylePtr};
+use crate::gecko_bindings::structs::{nsStyleCoord, CounterStylePtr};
 use crate::gecko_bindings::structs::{StyleGridTrackBreadth, StyleShapeRadius};
 use crate::gecko_bindings::sugar::ns_style_coord::{CoordData, CoordDataMut, CoordDataValue};
-use crate::media_queries::Device;
 use crate::values::computed::basic_shape::ShapeRadius as ComputedShapeRadius;
-use crate::values::computed::FlexBasis as ComputedFlexBasis;
-use crate::values::computed::{Angle, ExtremumLength, Length, LengthPercentage};
-use crate::values::computed::{MaxSize as ComputedMaxSize, Size as ComputedSize};
-use crate::values::computed::{NonNegativeLengthPercentage, Percentage};
-use crate::values::computed::{Number, NumberOrPercentage};
+use crate::values::computed::{Angle, Length, LengthPercentage};
+use crate::values::computed::{Number, NumberOrPercentage, Percentage};
 use crate::values::generics::basic_shape::ShapeRadius;
-use crate::values::generics::box_::Perspective;
-use crate::values::generics::flex::FlexBasis;
 use crate::values::generics::gecko::ScrollSnapPoint;
 use crate::values::generics::grid::{TrackBreadth, TrackKeyword};
-use crate::values::generics::length::{LengthPercentageOrAuto, MaxSize, Size};
+use crate::values::generics::length::LengthPercentageOrAuto;
 use crate::values::generics::{CounterStyleOrNone, NonNegative};
 use crate::values::{Auto, Either, None_, Normal};
 use crate::Atom;
@@ -80,29 +74,6 @@ where
     }
 }
 
-impl GeckoStyleCoordConvertible for ComputedFlexBasis {
-    fn to_gecko_style_coord<T: CoordDataMut>(&self, coord: &mut T) {
-        match *self {
-            FlexBasis::Content => coord.set_value(CoordDataValue::Enumerated(
-                structs::NS_STYLE_FLEX_BASIS_CONTENT,
-            )),
-            FlexBasis::Width(ref w) => w.to_gecko_style_coord(coord),
-        }
-    }
-
-    fn from_gecko_style_coord<T: CoordData>(coord: &T) -> Option<Self> {
-        if let Some(width) = ComputedSize::from_gecko_style_coord(coord) {
-            return Some(FlexBasis::Width(width));
-        }
-
-        if let CoordDataValue::Enumerated(structs::NS_STYLE_FLEX_BASIS_CONTENT) = coord.as_value() {
-            return Some(FlexBasis::Content);
-        }
-
-        None
-    }
-}
-
 impl GeckoStyleCoordConvertible for Number {
     fn to_gecko_style_coord<T: CoordDataMut>(&self, coord: &mut T) {
         coord.set_value(CoordDataValue::Factor(*self));
@@ -336,60 +307,6 @@ impl GeckoStyleCoordConvertible for Normal {
     }
 }
 
-impl GeckoStyleCoordConvertible for ExtremumLength {
-    fn to_gecko_style_coord<T: CoordDataMut>(&self, coord: &mut T) {
-        coord.set_value(CoordDataValue::Enumerated(*self as u32));
-    }
-
-    fn from_gecko_style_coord<T: CoordData>(coord: &T) -> Option<Self> {
-        use num_traits::FromPrimitive;
-        match coord.as_value() {
-            CoordDataValue::Enumerated(v) => ExtremumLength::from_u32(v),
-            _ => None,
-        }
-    }
-}
-
-impl GeckoStyleCoordConvertible for ComputedSize {
-    fn to_gecko_style_coord<T: CoordDataMut>(&self, coord: &mut T) {
-        match *self {
-            Size::LengthPercentage(ref lpoa) => lpoa.to_gecko_style_coord(coord),
-            Size::Auto => coord.set_value(CoordDataValue::Auto),
-            Size::ExtremumLength(ref e) => e.to_gecko_style_coord(coord),
-        }
-    }
-
-    fn from_gecko_style_coord<T: CoordData>(coord: &T) -> Option<Self> {
-        if let CoordDataValue::Auto = coord.as_value() {
-            return Some(Size::Auto);
-        }
-        if let Some(lp) = NonNegativeLengthPercentage::from_gecko_style_coord(coord) {
-            return Some(Size::LengthPercentage(lp));
-        }
-        ExtremumLength::from_gecko_style_coord(coord).map(Size::ExtremumLength)
-    }
-}
-
-impl GeckoStyleCoordConvertible for ComputedMaxSize {
-    fn to_gecko_style_coord<T: CoordDataMut>(&self, coord: &mut T) {
-        match *self {
-            MaxSize::LengthPercentage(ref lpon) => lpon.to_gecko_style_coord(coord),
-            MaxSize::None => coord.set_value(CoordDataValue::None),
-            MaxSize::ExtremumLength(ref e) => e.to_gecko_style_coord(coord),
-        }
-    }
-
-    fn from_gecko_style_coord<T: CoordData>(coord: &T) -> Option<Self> {
-        if let CoordDataValue::None = coord.as_value() {
-            return Some(MaxSize::None);
-        }
-        if let Some(lp) = NonNegativeLengthPercentage::from_gecko_style_coord(coord) {
-            return Some(MaxSize::LengthPercentage(lp));
-        }
-        ExtremumLength::from_gecko_style_coord(coord).map(MaxSize::ExtremumLength)
-    }
-}
-
 impl GeckoStyleCoordConvertible for ScrollSnapPoint<LengthPercentage> {
     fn to_gecko_style_coord<T: CoordDataMut>(&self, coord: &mut T) {
         match self.repeated() {
@@ -412,27 +329,6 @@ impl GeckoStyleCoordConvertible for ScrollSnapPoint<LengthPercentage> {
     }
 }
 
-impl<L> GeckoStyleCoordConvertible for Perspective<L>
-where
-    L: GeckoStyleCoordConvertible,
-{
-    fn to_gecko_style_coord<T: CoordDataMut>(&self, coord: &mut T) {
-        match *self {
-            Perspective::None => coord.set_value(CoordDataValue::None),
-            Perspective::Length(ref l) => l.to_gecko_style_coord(coord),
-        };
-    }
-
-    fn from_gecko_style_coord<T: CoordData>(coord: &T) -> Option<Self> {
-        use crate::gecko_bindings::structs::root::nsStyleUnit;
-
-        if coord.unit() == nsStyleUnit::eStyleUnit_None {
-            return Some(Perspective::None);
-        }
-        Some(Perspective::Length(L::from_gecko_style_coord(coord)?))
-    }
-}
-
 /// Convert a given RGBA value to `nscolor`.
 pub fn convert_rgba_to_nscolor(rgba: &RGBA) -> u32 {
     ((rgba.alpha as u32) << 24) |
@@ -468,16 +364,15 @@ pub fn round_border_to_device_pixels(width: Au, au_per_device_px: Au) -> Au {
 
 impl CounterStyleOrNone {
     /// Convert this counter style to a Gecko CounterStylePtr.
-    pub fn to_gecko_value(self, gecko_value: &mut CounterStylePtr, device: &Device) {
+    pub fn to_gecko_value(self, gecko_value: &mut CounterStylePtr) {
         use crate::gecko_bindings::bindings::Gecko_SetCounterStyleToName as set_name;
         use crate::gecko_bindings::bindings::Gecko_SetCounterStyleToSymbols as set_symbols;
-        let pres_context = device.pres_context();
         match self {
             CounterStyleOrNone::None => unsafe {
-                set_name(gecko_value, atom!("none").into_addrefed(), pres_context);
+                set_name(gecko_value, atom!("none").into_addrefed());
             },
             CounterStyleOrNone::Name(name) => unsafe {
-                set_name(gecko_value, name.0.into_addrefed(), pres_context);
+                set_name(gecko_value, name.0.into_addrefed());
             },
             CounterStyleOrNone::Symbols(symbols_type, symbols) => {
                 let symbols: Vec<_> = symbols
diff --git a/components/style/gecko_bindings/sugar/style_complex_color.rs b/components/style/gecko_bindings/sugar/style_complex_color.rs
index 4d31459a628..aec334969d4 100644
--- a/components/style/gecko_bindings/sugar/style_complex_color.rs
+++ b/components/style/gecko_bindings/sugar/style_complex_color.rs
@@ -7,10 +7,10 @@
 use crate::gecko::values::{convert_nscolor_to_rgba, convert_rgba_to_nscolor};
 use crate::gecko_bindings::structs::StyleComplexColor;
 use crate::gecko_bindings::structs::StyleComplexColor_Tag as Tag;
-use crate::values::computed::ui::ColorOrAuto;
-use crate::values::computed::{Color as ComputedColor, RGBAColor as ComputedRGBA};
-use crate::values::generics::color::{Color as GenericColor, ComplexColorRatios};
-use crate::values::{Auto, Either};
+use crate::values::computed::{Color as ComputedColor, ColorOrAuto, RGBAColor as ComputedRGBA};
+use crate::values::generics::color::{
+    Color as GenericColor, ColorOrAuto as GenericColorOrAuto, ComplexColorRatios,
+};
 
 impl StyleComplexColor {
     /// Create a `StyleComplexColor` value that represents `currentColor`.
@@ -94,8 +94,8 @@ impl From<StyleComplexColor> for ComputedColor {
 impl From<ColorOrAuto> for StyleComplexColor {
     fn from(other: ColorOrAuto) -> Self {
         match other {
-            Either::First(color) => color.into(),
-            Either::Second(_) => StyleComplexColor::auto(),
+            GenericColorOrAuto::Color(color) => color.into(),
+            GenericColorOrAuto::Auto => StyleComplexColor::auto(),
         }
     }
 }
@@ -103,9 +103,9 @@ impl From<ColorOrAuto> for StyleComplexColor {
 impl From<StyleComplexColor> for ColorOrAuto {
     fn from(other: StyleComplexColor) -> Self {
         if other.mTag != Tag::eAuto {
-            Either::First(other.into())
+            GenericColorOrAuto::Color(other.into())
         } else {
-            Either::Second(Auto)
+            GenericColorOrAuto::Auto
         }
     }
 }
diff --git a/components/style/properties/cascade.rs b/components/style/properties/cascade.rs
index d881524deb5..4a0e07fdcac 100644
--- a/components/style/properties/cascade.rs
+++ b/components/style/properties/cascade.rs
@@ -236,7 +236,7 @@ where
                 parent_style.unwrap(),
                 parent_style_ignoring_first_line.unwrap()
             ) ||
-            parent_style.unwrap().pseudo() == Some(PseudoElement::FirstLine)
+            parent_style.unwrap().is_first_line_style()
     );
 
     let inherited_style = parent_style.unwrap_or(device.default_computed_values());
@@ -745,13 +745,13 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
 
                 // FIXME(emilio): Why both setting the generic and passing it
                 // down?
-                let pres_context = self.context.builder.device.pres_context();
+                let doc = self.context.builder.device.document();
                 let gecko_font = self.context.builder.mutate_font().gecko_mut();
                 gecko_font.mGenericID = generic;
                 unsafe {
                     crate::gecko_bindings::bindings::Gecko_nsStyleFont_PrefillDefaultForGeneric(
                         gecko_font,
-                        pres_context,
+                        doc,
                         generic,
                     );
                 }
diff --git a/components/style/properties/data.py b/components/style/properties/data.py
index b897cc140d2..f3b4e43c225 100644
--- a/components/style/properties/data.py
+++ b/components/style/properties/data.py
@@ -339,6 +339,7 @@ class Longhand(object):
                 "Resize",
                 "SVGOpacity",
                 "SVGPaintOrder",
+                "ScrollSnapAlign",
                 "ScrollSnapType",
                 "TextAlign",
                 "TextDecorationLine",
diff --git a/components/style/properties/gecko.mako.rs b/components/style/properties/gecko.mako.rs
index 6baae1d9063..b1be315e7a0 100644
--- a/components/style/properties/gecko.mako.rs
+++ b/components/style/properties/gecko.mako.rs
@@ -35,10 +35,9 @@ use crate::gecko_bindings::bindings::Gecko_SetListStyleImageNone;
 use crate::gecko_bindings::bindings::Gecko_SetListStyleImageImageValue;
 use crate::gecko_bindings::bindings::Gecko_SetNullImageValue;
 use crate::gecko_bindings::bindings::{Gecko_ResetFilters, Gecko_CopyFiltersFrom};
-use crate::gecko_bindings::bindings::RawGeckoPresContextBorrowed;
 use crate::gecko_bindings::structs;
 use crate::gecko_bindings::structs::nsCSSPropertyID;
-use crate::gecko_bindings::structs::mozilla::CSSPseudoElementType;
+use crate::gecko_bindings::structs::mozilla::PseudoStyleType;
 use crate::gecko_bindings::sugar::ns_style_coord::{CoordDataValue, CoordData, CoordDataMut};
 use crate::gecko_bindings::sugar::refptr::RefPtr;
 use crate::gecko::values::convert_nscolor_to_rgba;
@@ -61,8 +60,6 @@ use crate::values::computed::BorderStyle;
 use crate::values::computed::font::FontSize;
 use crate::values::computed::effects::{BoxShadow, Filter, SimpleShadow};
 use crate::values::generics::column::ColumnCount;
-use crate::values::generics::position::ZIndex;
-use crate::values::generics::text::MozTabSize;
 use crate::values::generics::transform::TransformStyle;
 use crate::values::generics::url::UrlOrNone;
 
@@ -102,7 +99,7 @@ impl ComputedValues {
         ).to_outer(pseudo)
     }
 
-    pub fn default_values(pres_context: RawGeckoPresContextBorrowed) -> Arc<Self> {
+    pub fn default_values(doc: &structs::Document) -> Arc<Self> {
         ComputedValuesInner::new(
             /* custom_properties = */ None,
             /* writing_mode = */ WritingMode::empty(), // FIXME(bz): This seems dubious
@@ -110,31 +107,22 @@ impl ComputedValues {
             /* rules = */ None,
             /* visited_style = */ None,
             % for style_struct in data.style_structs:
-            style_structs::${style_struct.name}::default(pres_context),
+            style_structs::${style_struct.name}::default(doc),
             % endfor
         ).to_outer(None)
     }
 
+    #[inline]
     pub fn pseudo(&self) -> Option<PseudoElement> {
-        let atom = (self.0).mPseudoTag.mRawPtr;
-        if atom.is_null() {
+        if self.0.mPseudoType == PseudoStyleType::NotPseudo {
             return None;
         }
-
-        let atom = unsafe { Atom::from_raw(atom) };
-        PseudoElement::from_atom(&atom)
+        PseudoElement::from_pseudo_type(self.0.mPseudoType)
     }
 
     #[inline]
-    fn get_pseudo_type(&self) -> CSSPseudoElementType {
-        self.0.mPseudoType
-    }
-
-    #[inline]
-    pub fn is_anon_box(&self) -> bool {
-        let our_type = self.get_pseudo_type();
-        return our_type == CSSPseudoElementType::InheritingAnonBox ||
-               our_type == CSSPseudoElementType::NonInheritingAnonBox;
+    pub fn is_first_line_style(&self) -> bool {
+        self.pseudo() == Some(PseudoElement::FirstLine)
     }
 
     /// Returns true if the display property is changed from 'none' to others.
@@ -213,9 +201,9 @@ impl ComputedValuesInner {
         self,
         pseudo: Option<<&PseudoElement>,
     ) -> Arc<ComputedValues> {
-        let (pseudo_tag, pseudo_ty) = match pseudo {
-            Some(p) => p.pseudo_info(),
-            None => (ptr::null_mut(), structs::CSSPseudoElementType::NotPseudo),
+        let pseudo_ty = match pseudo {
+            Some(p) => p.pseudo_type(),
+            None => structs::PseudoStyleType::NotPseudo,
         };
         let arc = unsafe {
             let arc: Arc<ComputedValues> = Arc::new(uninitialized());
@@ -223,7 +211,6 @@ impl ComputedValuesInner {
                 &arc.0 as *const _ as *mut _,
                 &self,
                 pseudo_ty,
-                pseudo_tag
             );
             // We're simulating a move by having C++ do a memcpy and then forgetting
             // it on this end.
@@ -453,22 +440,6 @@ def set_gecko_property(ffi_name, expr):
     }
 </%def>
 
-<%def name="impl_position(ident, gecko_ffi_name)">
-    #[allow(non_snake_case)]
-    pub fn set_${ident}(&mut self, v: longhands::${ident}::computed_value::T) {
-        ${set_gecko_property("%s.mXPosition" % gecko_ffi_name, "v.horizontal.into()")}
-        ${set_gecko_property("%s.mYPosition" % gecko_ffi_name, "v.vertical.into()")}
-    }
-    <%call expr="impl_simple_copy(ident, gecko_ffi_name)"></%call>
-    #[allow(non_snake_case)]
-    pub fn clone_${ident}(&self) -> longhands::${ident}::computed_value::T {
-        longhands::${ident}::computed_value::T {
-            horizontal: self.gecko.${gecko_ffi_name}.mXPosition.into(),
-            vertical: self.gecko.${gecko_ffi_name}.mYPosition.into(),
-        }
-    }
-</%def>
-
 <%def name="impl_color(ident, gecko_ffi_name)">
 <%call expr="impl_color_setter(ident, gecko_ffi_name)"></%call>
 <%call expr="impl_color_copy(ident, gecko_ffi_name)"></%call>
@@ -1217,55 +1188,6 @@ pub fn clone_transform_from_list(
     }
 </%def>
 
-<%def name="impl_transform_origin(ident, gecko_ffi_name)">
-    #[allow(non_snake_case)]
-    pub fn set_${ident}(&mut self, v: values::computed::TransformOrigin) {
-        self.gecko.${gecko_ffi_name}[0].set(v.horizontal);
-        self.gecko.${gecko_ffi_name}[1].set(v.vertical);
-        // transform-origin supports the third value for depth, while
-        // -moz-window-transform-origin doesn't. The following code is
-        // for handling this difference. If we can have more knowledge
-        // about the type here, we may want to check that the length is
-        // exactly either 2 or 3 in compile time.
-        if let Some(third) = self.gecko.${gecko_ffi_name}.get_mut(2) {
-            third.set(v.depth);
-        }
-    }
-
-    #[allow(non_snake_case)]
-    pub fn copy_${ident}_from(&mut self, other: &Self) {
-        self.gecko.${gecko_ffi_name}[0].copy_from(&other.gecko.${gecko_ffi_name}[0]);
-        self.gecko.${gecko_ffi_name}[1].copy_from(&other.gecko.${gecko_ffi_name}[1]);
-        if let (Some(self_third), Some(other_third)) =
-            (self.gecko.${gecko_ffi_name}.get_mut(2), other.gecko.${gecko_ffi_name}.get(2))
-        {
-            self_third.copy_from(other_third)
-        }
-    }
-
-    #[allow(non_snake_case)]
-    pub fn reset_${ident}(&mut self, other: &Self) {
-        self.copy_${ident}_from(other)
-    }
-
-    #[allow(non_snake_case)]
-    pub fn clone_${ident}(&self) -> values::computed::TransformOrigin {
-        use crate::values::computed::{Length, LengthPercentage, TransformOrigin};
-        TransformOrigin {
-            horizontal: LengthPercentage::from_gecko_style_coord(&self.gecko.${gecko_ffi_name}[0])
-                .expect("clone for LengthPercentage failed"),
-            vertical: LengthPercentage::from_gecko_style_coord(&self.gecko.${gecko_ffi_name}[1])
-                .expect("clone for LengthPercentage failed"),
-            depth: if let Some(third) = self.gecko.${gecko_ffi_name}.get(2) {
-                Length::from_gecko_style_coord(third)
-                    .expect("clone for Length failed")
-            } else {
-                Length::new(0.)
-            },
-        }
-    }
-</%def>
-
 <%def name="impl_logical(name, **kwargs)">
     ${helpers.logical_setter(name)}
 </%def>
@@ -1273,11 +1195,13 @@ pub fn clone_transform_from_list(
 <%def name="impl_style_struct(style_struct)">
 impl ${style_struct.gecko_struct_name} {
     #[allow(dead_code, unused_variables)]
-    pub fn default(pres_context: RawGeckoPresContextBorrowed) -> Arc<Self> {
+    pub fn default(document: &structs::Document) -> Arc<Self> {
         let mut result = Arc::new(${style_struct.gecko_struct_name} { gecko: unsafe { zeroed() } });
         unsafe {
-            Gecko_Construct_Default_${style_struct.gecko_ffi_name}(&mut Arc::get_mut(&mut result).unwrap().gecko,
-                                                                   pres_context);
+            Gecko_Construct_Default_${style_struct.gecko_ffi_name}(
+                &mut Arc::get_mut(&mut result).unwrap().gecko,
+                document,
+            );
         }
         result
     }
@@ -1370,6 +1294,7 @@ impl Clone for ${style_struct.gecko_struct_name} {
         "Appearance": impl_simple,
         "OverscrollBehavior": impl_simple,
         "OverflowClipBox": impl_simple,
+        "ScrollSnapAlign": impl_simple,
         "ScrollSnapType": impl_simple,
         "Float": impl_simple,
         "Overflow": impl_simple,
@@ -1385,32 +1310,36 @@ impl Clone for ${style_struct.gecko_struct_name} {
         "length::NonNegativeLengthOrAuto": impl_style_coord,
         "length::NonNegativeLengthPercentageOrNormal": impl_style_coord,
         "FillRule": impl_simple,
-        "FlexBasis": impl_style_coord,
+        "FlexBasis": impl_simple,
         "Length": impl_absolute_length,
         "LengthOrNormal": impl_style_coord,
         "LengthPercentage": impl_simple,
         "LengthPercentageOrAuto": impl_style_coord,
-        "MaxSize": impl_style_coord,
-        "Size": impl_style_coord,
+        "MaxSize": impl_simple,
+        "Size": impl_simple,
         "MozScriptMinSize": impl_absolute_length,
         "MozScriptSizeMultiplier": impl_simple,
         "NonNegativeLengthPercentage": impl_simple,
+        "NonNegativeLengthOrNumber": impl_simple,
+        "NonNegativeLengthOrNumberRect": impl_simple,
+        "BorderImageSlice": impl_simple,
         "NonNegativeNumber": impl_simple,
         "Number": impl_simple,
         "Opacity": impl_simple,
         "OverflowWrap": impl_simple,
         "OverflowAnchor": impl_simple,
-        "Perspective": impl_style_coord,
-        "Position": impl_position,
+        "Perspective": impl_simple,
+        "Position": impl_simple,
         "RGBAColor": impl_rgba_color,
         "SVGLength": impl_svg_length,
         "SVGOpacity": impl_svg_opacity,
         "SVGPaint": impl_svg_paint,
         "SVGWidth": impl_svg_length,
         "Transform": impl_transform,
-        "TransformOrigin": impl_transform_origin,
+        "TransformOrigin": impl_simple,
         "UserSelect": impl_simple,
         "url::UrlOrNone": impl_css_url,
+        "ZIndex": impl_simple,
     }
 
     def longhand_method(longhand):
@@ -1500,8 +1429,8 @@ fn static_assert() {
                                      for x in CORNERS]) %>
 
 <%self:impl_trait style_struct_name="Border"
-                  skip_longhands="${skip_border_longhands} border-image-source border-image-outset
-                                  border-image-repeat border-image-width border-image-slice">
+                  skip_longhands="${skip_border_longhands} border-image-source
+                                  border-image-repeat border-image-width">
     % for side in SIDES:
     pub fn set_border_${side.ident}_style(&mut self, v: BorderStyle) {
         self.gecko.mBorderStyle[${side.index}] = v;
@@ -1602,8 +1531,6 @@ fn static_assert() {
         }
     }
 
-    <% impl_style_sides("border_image_outset") %>
-
     <%
     border_image_repeat_keywords = ["Stretch", "Repeat", "Round", "Space"]
     %>
@@ -1645,63 +1572,41 @@ fn static_assert() {
     }
 
     <% impl_style_sides("border_image_width") %>
-
-    pub fn set_border_image_slice(&mut self, v: longhands::border_image_slice::computed_value::T) {
-        use crate::gecko_bindings::structs::{NS_STYLE_BORDER_IMAGE_SLICE_NOFILL, NS_STYLE_BORDER_IMAGE_SLICE_FILL};
-
-        v.offsets.to_gecko_rect(&mut self.gecko.mBorderImageSlice);
-
-        let fill = if v.fill {
-            NS_STYLE_BORDER_IMAGE_SLICE_FILL
-        } else {
-            NS_STYLE_BORDER_IMAGE_SLICE_NOFILL
-        };
-        self.gecko.mBorderImageFill = fill as u8;
-    }
-
-    <%self:copy_sides_style_coord ident="border_image_slice">
-        self.gecko.mBorderImageFill = other.gecko.mBorderImageFill;
-    </%self:copy_sides_style_coord>
-
-    pub fn clone_border_image_slice(&self) -> longhands::border_image_slice::computed_value::T {
-        use crate::gecko_bindings::structs::NS_STYLE_BORDER_IMAGE_SLICE_FILL;
-        use crate::values::computed::{BorderImageSlice, NonNegativeNumberOrPercentage};
-        type NumberOrPercentageRect = crate::values::generics::rect::Rect<NonNegativeNumberOrPercentage>;
-
-        BorderImageSlice {
-            offsets:
-                NumberOrPercentageRect::from_gecko_rect(&self.gecko.mBorderImageSlice)
-                    .expect("mBorderImageSlice[${side}] could not convert to NumberOrPercentageRect"),
-            fill: self.gecko.mBorderImageFill as u32 == NS_STYLE_BORDER_IMAGE_SLICE_FILL
-        }
-    }
 </%self:impl_trait>
 
+<% skip_scroll_margin_longhands = " ".join(["scroll-margin-%s" % x.ident for x in SIDES]) %>
 <% skip_margin_longhands = " ".join(["margin-%s" % x.ident for x in SIDES]) %>
 <%self:impl_trait style_struct_name="Margin"
-                  skip_longhands="${skip_margin_longhands}">
+                  skip_longhands="${skip_margin_longhands}
+                                  ${skip_scroll_margin_longhands}">
 
     % for side in SIDES:
     <% impl_split_style_coord("margin_%s" % side.ident,
                               "mMargin",
                               side.index) %>
+    <% impl_split_style_coord("scroll_margin_%s" % side.ident,
+                              "mScrollMargin",
+                              side.index) %>
     % endfor
 </%self:impl_trait>
 
+<% skip_scroll_padding_longhands = " ".join(["scroll-padding-%s" % x.ident for x in SIDES]) %>
 <% skip_padding_longhands = " ".join(["padding-%s" % x.ident for x in SIDES]) %>
 <%self:impl_trait style_struct_name="Padding"
-                  skip_longhands="${skip_padding_longhands}">
+                  skip_longhands="${skip_padding_longhands}
+                                  ${skip_scroll_padding_longhands}">
 
     % for side in SIDES:
     <% impl_split_style_coord("padding_%s" % side.ident,
                               "mPadding",
                               side.index) %>
+    <% impl_split_style_coord("scroll_padding_%s" % side.ident, "mScrollPadding", side.index) %>
     % endfor
 </%self:impl_trait>
 
 <% skip_position_longhands = " ".join(x.ident for x in SIDES + GRID_LINES) %>
 <%self:impl_trait style_struct_name="Position"
-                  skip_longhands="${skip_position_longhands} z-index order
+                  skip_longhands="${skip_position_longhands} order
                                   align-content justify-content align-self
                                   justify-self align-items justify-items
                                   grid-auto-rows grid-auto-columns
@@ -1711,38 +1616,6 @@ fn static_assert() {
     <% impl_split_style_coord(side.ident, "mOffset", side.index) %>
     % endfor
 
-    pub fn set_z_index(&mut self, v: longhands::z_index::computed_value::T) {
-        match v {
-            ZIndex::Integer(n) => self.gecko.mZIndex.set_value(CoordDataValue::Integer(n)),
-            ZIndex::Auto => self.gecko.mZIndex.set_value(CoordDataValue::Auto),
-        }
-    }
-
-    pub fn copy_z_index_from(&mut self, other: &Self) {
-        use crate::gecko_bindings::structs::nsStyleUnit;
-        // z-index is never a calc(). If it were, we'd be leaking here, so
-        // assert that it isn't.
-        debug_assert_ne!(self.gecko.mZIndex.unit(), nsStyleUnit::eStyleUnit_Calc);
-        unsafe {
-            self.gecko.mZIndex.copy_from_unchecked(&other.gecko.mZIndex);
-        }
-    }
-
-    pub fn reset_z_index(&mut self, other: &Self) {
-        self.copy_z_index_from(other)
-    }
-
-    pub fn clone_z_index(&self) -> longhands::z_index::computed_value::T {
-        return match self.gecko.mZIndex.as_value() {
-            CoordDataValue::Integer(n) => ZIndex::Integer(n),
-            CoordDataValue::Auto => ZIndex::Auto,
-            _ => {
-                debug_assert!(false);
-                ZIndex::Integer(0)
-            }
-        }
-    }
-
     % for kind in ["align", "justify"]:
     ${impl_simple_type_with_conversion(kind + "_content")}
     ${impl_simple_type_with_conversion(kind + "_self")}
@@ -2216,7 +2089,7 @@ fn static_assert() {
     pub fn fixup_none_generic(&mut self, device: &Device) {
         self.gecko.mFont.systemFont = false;
         unsafe {
-            bindings::Gecko_nsStyleFont_FixupNoneGeneric(&mut self.gecko, device.pres_context())
+            bindings::Gecko_nsStyleFont_FixupNoneGeneric(&mut self.gecko, device.document())
         }
     }
 
@@ -2332,7 +2205,7 @@ fn static_assert() {
     }
 
     pub fn fixup_font_min_size(&mut self, device: &Device) {
-        unsafe { bindings::Gecko_nsStyleFont_FixupMinFontSize(&mut self.gecko, device.pres_context()) }
+        unsafe { bindings::Gecko_nsStyleFont_FixupMinFontSize(&mut self.gecko, device.document()) }
     }
 
     pub fn apply_unconstrained_font_size(&mut self, v: NonNegativeLength) {
@@ -2654,12 +2527,11 @@ fn static_assert() {
     ${impl_simple("_moz_script_level", "mScriptLevel")}
     <% impl_simple_type_with_conversion("font_language_override", "mFont.languageOverride") %>
 
-    pub fn set_font_variant_alternates(&mut self,
-                                       v: values::computed::font::FontVariantAlternates,
-                                       device: &Device) {
+    pub fn set_font_variant_alternates(
+        &mut self,
+        v: values::computed::font::FontVariantAlternates,
+    ) {
         use crate::gecko_bindings::bindings::{Gecko_ClearAlternateValues, Gecko_AppendAlternateValues};
-        use crate::gecko_bindings::bindings::Gecko_nsFont_ResetFontFeatureValuesLookup;
-        use crate::gecko_bindings::bindings::Gecko_nsFont_SetFontFeatureValuesLookup;
         % for value in "normal swash stylistic ornaments annotation styleset character_variant historical".split():
             use crate::gecko_bindings::structs::NS_FONT_VARIANT_ALTERNATES_${value.upper()};
         % endfor
@@ -2671,7 +2543,6 @@ fn static_assert() {
 
         if v.0.is_empty() {
             self.gecko.mFont.variantAlternates = NS_FONT_VARIANT_ALTERNATES_NORMAL as u16;
-            unsafe { Gecko_nsFont_ResetFontFeatureValuesLookup(&mut self.gecko.mFont); }
             return;
         }
 
@@ -2704,10 +2575,6 @@ fn static_assert() {
                 }
             }
         }
-
-        unsafe {
-            Gecko_nsFont_SetFontFeatureValuesLookup(&mut self.gecko.mFont, device.pres_context());
-        }
     }
 
     #[allow(non_snake_case)]
@@ -2997,10 +2864,8 @@ fn static_assert() {
                           clear transition-duration transition-delay
                           transition-timing-function transition-property
                           rotate scroll-snap-points-x scroll-snap-points-y
-                          scroll-snap-coordinate
-                          perspective-origin -moz-binding will-change
-                          offset-path perspective-origin -moz-binding
-                          will-change shape-outside contain touch-action
+                          scroll-snap-coordinate -moz-binding will-change
+                          offset-path shape-outside contain touch-action
                           translate scale""" %>
 <%self:impl_trait style_struct_name="Box" skip_longhands="${skip_box_longhands}">
     #[inline]
@@ -3095,11 +2960,7 @@ fn static_assert() {
         where I: IntoIterator<Item = longhands::scroll_snap_coordinate::computed_value::single_value::T>,
               I::IntoIter: ExactSizeIterator
     {
-        let iter = v.into_iter().map(|c| structs::mozilla::Position {
-            mXPosition: c.horizontal.into(),
-            mYPosition: c.vertical.into(),
-        });
-        self.gecko.mScrollSnapCoordinate.assign_from_iter_pod(iter);
+        self.gecko.mScrollSnapCoordinate.assign_from_iter_pod(v.into_iter());
     }
 
     pub fn copy_scroll_snap_coordinate_from(&mut self, other: &Self) {
@@ -3112,7 +2973,7 @@ fn static_assert() {
     }
 
     pub fn clone_scroll_snap_coordinate(&self) -> longhands::scroll_snap_coordinate::computed_value::T {
-        let vec = self.gecko.mScrollSnapCoordinate.iter().map(|f| f.into()).collect();
+        let vec = self.gecko.mScrollSnapCoordinate.iter().cloned().collect();
         longhands::scroll_snap_coordinate::computed_value::List(vec)
     }
 
@@ -3356,31 +3217,6 @@ fn static_assert() {
 
     ${impl_animation_timing_function()}
 
-    pub fn set_perspective_origin(&mut self, v: longhands::perspective_origin::computed_value::T) {
-        self.gecko.mPerspectiveOrigin[0].set(v.horizontal);
-        self.gecko.mPerspectiveOrigin[1].set(v.vertical);
-    }
-
-    pub fn copy_perspective_origin_from(&mut self, other: &Self) {
-        self.gecko.mPerspectiveOrigin[0].copy_from(&other.gecko.mPerspectiveOrigin[0]);
-        self.gecko.mPerspectiveOrigin[1].copy_from(&other.gecko.mPerspectiveOrigin[1]);
-    }
-
-    pub fn reset_perspective_origin(&mut self, other: &Self) {
-        self.copy_perspective_origin_from(other)
-    }
-
-    pub fn clone_perspective_origin(&self) -> longhands::perspective_origin::computed_value::T {
-        use crate::properties::longhands::perspective_origin::computed_value::T;
-        use crate::values::computed::LengthPercentage;
-        T {
-            horizontal: LengthPercentage::from_gecko_style_coord(&self.gecko.mPerspectiveOrigin[0])
-                .expect("Expected length or percentage for horizontal value of perspective-origin"),
-            vertical: LengthPercentage::from_gecko_style_coord(&self.gecko.mPerspectiveOrigin[1])
-                .expect("Expected length or percentage for vertical value of perspective-origin"),
-        }
-    }
-
     ${impl_individual_transform('rotate', 'Rotate', 'mSpecifiedRotate')}
     ${impl_individual_transform('translate', 'Translate', 'mSpecifiedTranslate')}
     ${impl_individual_transform('scale', 'Scale', 'mSpecifiedScale')}
@@ -3759,7 +3595,7 @@ fn static_assert() {
     <% impl_simple_image_array_property("clip", shorthand, image_layers_field, "mClip", struct_name) %>
     <% impl_simple_image_array_property("origin", shorthand, image_layers_field, "mOrigin", struct_name) %>
 
-    % for orientation in ["x", "y"]:
+    % for (orientation, keyword) in [("x", "horizontal"), ("y", "vertical")]:
     pub fn copy_${shorthand}_position_${orientation}_from(&mut self, other: &Self) {
         use crate::gecko_bindings::structs::nsStyleImageLayers_LayerType as LayerType;
 
@@ -3774,8 +3610,7 @@ fn static_assert() {
         for (layer, other) in self.gecko.${image_layers_field}.mLayers.iter_mut()
                                   .zip(other.gecko.${image_layers_field}.mLayers.iter())
                                   .take(count as usize) {
-            layer.mPosition.m${orientation.upper()}Position
-                = other.mPosition.m${orientation.upper()}Position;
+            layer.mPosition.${keyword} = other.mPosition.${keyword};
         }
         self.gecko.${image_layers_field}.mPosition${orientation.upper()}Count = count;
     }
@@ -3789,7 +3624,7 @@ fn static_assert() {
         longhands::${shorthand}_position_${orientation}::computed_value::List(
             self.gecko.${image_layers_field}.mLayers.iter()
                 .take(self.gecko.${image_layers_field}.mPosition${orientation.upper()}Count as usize)
-                .map(|position| position.mPosition.m${orientation.upper()}Position.into())
+                .map(|position| position.mPosition.${keyword})
                 .collect()
         )
     }
@@ -3812,86 +3647,18 @@ fn static_assert() {
         self.gecko.${image_layers_field}.mPosition${orientation[0].upper()}Count = v.len() as u32;
         for (servo, geckolayer) in v.zip(self.gecko.${image_layers_field}
                                                            .mLayers.iter_mut()) {
-            geckolayer.mPosition.m${orientation[0].upper()}Position = servo.into();
+            geckolayer.mPosition.${keyword} = servo;
         }
     }
     % endfor
 
     <%self:simple_image_array_property name="size" shorthand="${shorthand}" field_name="mSize">
-        use crate::gecko_bindings::structs::nsStyleImageLayers_Size_Dimension;
-        use crate::gecko_bindings::structs::nsStyleImageLayers_Size_DimensionType;
-        use crate::gecko_bindings::structs::{nsStyleCoord_CalcValue, nsStyleImageLayers_Size};
-        use crate::values::generics::background::BackgroundSize;
-
-        let mut width = nsStyleCoord_CalcValue::new();
-        let mut height = nsStyleCoord_CalcValue::new();
-
-        let (w_type, h_type) = match servo {
-            BackgroundSize::Explicit { width: explicit_width, height: explicit_height } => {
-                let mut w_type = nsStyleImageLayers_Size_DimensionType::eAuto;
-                let mut h_type = nsStyleImageLayers_Size_DimensionType::eAuto;
-                if let Some(w) = explicit_width.to_calc_value() {
-                    width = w;
-                    w_type = nsStyleImageLayers_Size_DimensionType::eLengthPercentage;
-                }
-                if let Some(h) = explicit_height.to_calc_value() {
-                    height = h;
-                    h_type = nsStyleImageLayers_Size_DimensionType::eLengthPercentage;
-                }
-                (w_type, h_type)
-            }
-            BackgroundSize::Cover => {
-                (
-                    nsStyleImageLayers_Size_DimensionType::eCover,
-                    nsStyleImageLayers_Size_DimensionType::eCover,
-                )
-            },
-            BackgroundSize::Contain => {
-                (
-                    nsStyleImageLayers_Size_DimensionType::eContain,
-                    nsStyleImageLayers_Size_DimensionType::eContain,
-                )
-            },
-        };
-
-        nsStyleImageLayers_Size {
-            mWidth: nsStyleImageLayers_Size_Dimension { _base: width },
-            mHeight: nsStyleImageLayers_Size_Dimension { _base: height },
-            mWidthType: w_type as u8,
-            mHeightType: h_type as u8,
-        }
+        servo
     </%self:simple_image_array_property>
 
     pub fn clone_${shorthand}_size(&self) -> longhands::${shorthand}_size::computed_value::T {
-        use crate::gecko_bindings::structs::nsStyleCoord_CalcValue as CalcValue;
-        use crate::gecko_bindings::structs::nsStyleImageLayers_Size_DimensionType as DimensionType;
-        use crate::values::computed::NonNegativeLengthPercentageOrAuto;
-        use crate::values::generics::background::BackgroundSize;
-
-        fn to_servo(value: CalcValue, ty: u8) -> NonNegativeLengthPercentageOrAuto {
-            if ty == DimensionType::eAuto as u8 {
-                NonNegativeLengthPercentageOrAuto::auto()
-            } else {
-                debug_assert_eq!(ty, DimensionType::eLengthPercentage as u8);
-                value.into()
-            }
-        }
-
         longhands::${shorthand}_size::computed_value::List(
-            self.gecko.${image_layers_field}.mLayers.iter().map(|ref layer| {
-                if DimensionType::eCover as u8 == layer.mSize.mWidthType {
-                    debug_assert_eq!(layer.mSize.mHeightType, DimensionType::eCover as u8);
-                    return BackgroundSize::Cover
-                }
-                if DimensionType::eContain as u8 == layer.mSize.mWidthType {
-                    debug_assert_eq!(layer.mSize.mHeightType, DimensionType::eContain as u8);
-                    return BackgroundSize::Contain
-                }
-                BackgroundSize::Explicit {
-                    width: to_servo(layer.mSize.mWidth._base, layer.mSize.mWidthType),
-                    height: to_servo(layer.mSize.mHeight._base, layer.mSize.mHeightType),
-                }
-            }).collect()
+            self.gecko.${image_layers_field}.mLayers.iter().map(|layer| layer.mSize).collect()
         )
     }
 
@@ -4043,12 +3810,12 @@ fn static_assert() {
         }
     }
 
-    pub fn set_list_style_type(&mut self, v: longhands::list_style_type::computed_value::T, device: &Device) {
+    pub fn set_list_style_type(&mut self, v: longhands::list_style_type::computed_value::T) {
         use crate::gecko_bindings::bindings::Gecko_SetCounterStyleToString;
         use nsstring::{nsACString, nsCStr};
         use self::longhands::list_style_type::computed_value::T;
         match v {
-            T::CounterStyle(s) => s.to_gecko_value(&mut self.gecko.mCounterStyle, device),
+            T::CounterStyle(s) => s.to_gecko_value(&mut self.gecko.mCounterStyle),
             T::String(s) => unsafe {
                 Gecko_SetCounterStyleToString(&mut self.gecko.mCounterStyle,
                                               &nsCStr::from(&s) as &nsACString)
@@ -4472,7 +4239,7 @@ fn static_assert() {
 
 <%self:impl_trait style_struct_name="InheritedText"
                   skip_longhands="text-align text-emphasis-style text-shadow line-height letter-spacing word-spacing
-                                  -webkit-text-stroke-width text-emphasis-position -moz-tab-size">
+                                  -webkit-text-stroke-width text-emphasis-position">
 
     <% text_align_keyword = Keyword("text-align",
                                     "start end left right center justify -moz-center -moz-left -moz-right char",
@@ -4661,28 +4428,6 @@ fn static_assert() {
     ${impl_non_negative_length('_webkit_text_stroke_width',
                                'mWebkitTextStrokeWidth')}
 
-    #[allow(non_snake_case)]
-    pub fn set__moz_tab_size(&mut self, v: longhands::_moz_tab_size::computed_value::T) {
-        match v {
-            MozTabSize::Number(non_negative_number) => {
-                self.gecko.mTabSize.set_value(CoordDataValue::Factor(non_negative_number.0));
-            }
-            MozTabSize::Length(non_negative_length) => {
-                self.gecko.mTabSize.set(non_negative_length);
-            }
-        }
-    }
-
-    #[allow(non_snake_case)]
-    pub fn clone__moz_tab_size(&self) -> longhands::_moz_tab_size::computed_value::T {
-        match self.gecko.mTabSize.as_value() {
-            CoordDataValue::Coord(coord) => MozTabSize::Length(Au(coord).into()),
-            CoordDataValue::Factor(number) => MozTabSize::Number(From::from(number)),
-            _ => unreachable!(),
-        }
-    }
-
-    <%call expr="impl_coord_copy('_moz_tab_size', 'mTabSize')"></%call>
 </%self:impl_trait>
 
 <%self:impl_trait style_struct_name="Text"
@@ -5290,7 +5035,7 @@ clip-path
         self.gecko.mContents.is_empty()
     }
 
-    pub fn set_content(&mut self, v: longhands::content::computed_value::T, device: &Device) {
+    pub fn set_content(&mut self, v: longhands::content::computed_value::T) {
         use crate::values::CustomIdent;
         use crate::values::generics::counters::{Content, ContentItem};
         use crate::values::generics::CounterStyleOrNone;
@@ -5315,7 +5060,6 @@ clip-path
             name: &CustomIdent,
             sep: &str,
             style: CounterStyleOrNone,
-            device: &Device,
         ) {
             debug_assert!(content_type == StyleContentType::Counter ||
                           content_type == StyleContentType::Counters);
@@ -5326,7 +5070,7 @@ clip-path
             if content_type == StyleContentType::Counters {
                 counter_func.mSeparator.assign_str(sep);
             }
-            style.to_gecko_value(&mut counter_func.mCounterStyle, device);
+            style.to_gecko_value(&mut counter_func.mCounterStyle);
         }
 
         match v {
@@ -5401,7 +5145,6 @@ clip-path
                                 &name,
                                 "",
                                 style.clone(),
-                                device,
                             );
                         }
                         ContentItem::Counters(ref name, ref sep, ref style) => {
@@ -5411,7 +5154,6 @@ clip-path
                                 &name,
                                 &sep,
                                 style.clone(),
-                                device,
                             );
                         }
                         ContentItem::Url(ref url) => {
diff --git a/components/style/properties/longhands/border.mako.rs b/components/style/properties/longhands/border.mako.rs
index c9d6b7f5e19..13a7f237350 100644
--- a/components/style/properties/longhands/border.mako.rs
+++ b/components/style/properties/longhands/border.mako.rs
@@ -119,10 +119,9 @@ ${helpers.predefined_type(
 
 ${helpers.predefined_type(
     "border-image-outset",
-    "LengthOrNumberRect",
-    parse_method="parse_non_negative",
-    initial_value="computed::LengthOrNumberRect::all(computed::LengthOrNumber::zero())",
-    initial_specified_value="specified::LengthOrNumberRect::all(specified::LengthOrNumber::zero())",
+    "NonNegativeLengthOrNumberRect",
+    initial_value="generics::rect::Rect::all(computed::NonNegativeLengthOrNumber::zero())",
+    initial_specified_value="generics::rect::Rect::all(specified::NonNegativeLengthOrNumber::zero())",
     spec="https://drafts.csswg.org/css-backgrounds/#border-image-outset",
     animation_value_type="discrete",
     flags="APPLIES_TO_FIRST_LETTER",
diff --git a/components/style/properties/longhands/box.mako.rs b/components/style/properties/longhands/box.mako.rs
index 223db1d6e7c..1a8abfb3611 100644
--- a/components/style/properties/longhands/box.mako.rs
+++ b/components/style/properties/longhands/box.mako.rs
@@ -417,6 +417,16 @@ ${helpers.single_keyword(
     animation_value_type="discrete",
 )}
 
+${helpers.predefined_type(
+    "scroll-snap-align",
+    "ScrollSnapAlign",
+    "computed::ScrollSnapAlign::none()",
+    products="gecko",
+    gecko_pref="layout.css.scroll-snap-v1.enabled",
+    spec="https://drafts.csswg.org/css-scroll-snap-1/#scroll-snap-align",
+    animation_value_type="discrete",
+)}
+
 % for axis in ["x", "y"]:
     ${helpers.predefined_type(
         "scroll-snap-type-" + axis,
diff --git a/components/style/properties/longhands/color.mako.rs b/components/style/properties/longhands/color.mako.rs
index 13b1fda545c..487814935aa 100644
--- a/components/style/properties/longhands/color.mako.rs
+++ b/components/style/properties/longhands/color.mako.rs
@@ -98,7 +98,7 @@ pub mod system_colors {
             unsafe {
                 Gecko_GetLookAndFeelSystemColor(
                     *self as i32,
-                    cx.device().pres_context(),
+                    cx.device().document(),
                 )
             }
         }
diff --git a/components/style/properties/longhands/font.mako.rs b/components/style/properties/longhands/font.mako.rs
index 755797711e1..047ec90c480 100644
--- a/components/style/properties/longhands/font.mako.rs
+++ b/components/style/properties/longhands/font.mako.rs
@@ -396,7 +396,7 @@ ${helpers.predefined_type(
                         &mut system,
                         id as i32,
                         cx.style().get_font().gecko(),
-                        cx.device().pres_context()
+                        cx.device().document()
                     )
                 }
                 let font_weight = longhands::font_weight::computed_value::T::from_gecko_weight(system.weight);
diff --git a/components/style/properties/longhands/inherited_text.mako.rs b/components/style/properties/longhands/inherited_text.mako.rs
index b1ed79379ca..97d551120a4 100644
--- a/components/style/properties/longhands/inherited_text.mako.rs
+++ b/components/style/properties/longhands/inherited_text.mako.rs
@@ -257,10 +257,10 @@ ${helpers.predefined_type(
 
 ${helpers.predefined_type(
     "-moz-tab-size",
-    "MozTabSize",
-    "generics::text::MozTabSize::Number(From::from(8.0))",
+    "NonNegativeLengthOrNumber",
+    "generics::length::LengthOrNumber::Number(From::from(8.0))",
     products="gecko",
-    animation_value_type="AnimatedMozTabSize",
+    animation_value_type="LengthOrNumber",
     spec="https://drafts.csswg.org/css-text-3/#tab-size-property",
 )}
 
@@ -349,8 +349,8 @@ ${helpers.single_keyword(
     "-moz-control-character-visibility",
     "hidden visible",
     gecko_constant_prefix="NS_STYLE_CONTROL_CHARACTER_VISIBILITY",
-    gecko_ffi_name="mControlCharacterVisibility",
     animation_value_type="none",
+    gecko_ffi_name="mControlCharacterVisibility",
     products="gecko",
     spec="Nonstandard",
 )}
diff --git a/components/style/properties/longhands/inherited_ui.mako.rs b/components/style/properties/longhands/inherited_ui.mako.rs
index 87c7cd9ac4b..94709e1a681 100644
--- a/components/style/properties/longhands/inherited_ui.mako.rs
+++ b/components/style/properties/longhands/inherited_ui.mako.rs
@@ -60,7 +60,7 @@ ${helpers.single_keyword(
 ${helpers.predefined_type(
     "caret-color",
     "ColorOrAuto",
-    "Either::Second(Auto)",
+    "generics::color::ColorOrAuto::Auto",
     spec="https://drafts.csswg.org/css-ui/#caret-color",
     animation_value_type="AnimatedCaretColor",
     ignored_when_colors_disabled=True,
diff --git a/components/style/properties/longhands/margin.mako.rs b/components/style/properties/longhands/margin.mako.rs
index e5eac633c96..d2a3be11d1d 100644
--- a/components/style/properties/longhands/margin.mako.rs
+++ b/components/style/properties/longhands/margin.mako.rs
@@ -27,3 +27,18 @@
         servo_restyle_damage="reflow"
     )}
 % endfor
+
+% for side in ALL_SIDES:
+    ${helpers.predefined_type(
+        "scroll-margin-%s" % side[0],
+        "Length",
+        "computed::Length::zero()",
+        products="gecko",
+        gecko_pref="layout.css.scroll-snap-v1.enabled",
+        logical=side[1],
+        logical_group="scroll-margin",
+        spec="https://drafts.csswg.org/css-scroll-snap-1/#propdef-scroll-margin-%s" % side[0],
+        flags="APPLIES_TO_FIRST_LETTER APPLIES_TO_FIRST_LINE",
+        animation_value_type="ComputedValue",
+    )}
+% endfor
diff --git a/components/style/properties/longhands/padding.mako.rs b/components/style/properties/longhands/padding.mako.rs
index 5fa51863629..6c4e2b32cf9 100644
--- a/components/style/properties/longhands/padding.mako.rs
+++ b/components/style/properties/longhands/padding.mako.rs
@@ -28,3 +28,17 @@
         servo_restyle_damage="reflow rebuild_and_reflow_inline"
     )}
 % endfor
+
+% for side in ALL_SIDES:
+    ${helpers.predefined_type(
+        "scroll-padding-%s" % side[0],
+        "NonNegativeLengthPercentageOrAuto",
+        "computed::NonNegativeLengthPercentageOrAuto::auto()",
+        products="gecko",
+        gecko_pref="layout.css.scroll-snap-v1.enabled",
+        logical=side[1],
+        logical_group="scroll-padding",
+        spec="https://drafts.csswg.org/css-scroll-snap-1/#propdef-scroll-padding-%s" % side[0],
+        animation_value_type="ComputedValue",
+    )}
+% endfor
diff --git a/components/style/properties/longhands/position.mako.rs b/components/style/properties/longhands/position.mako.rs
index 714de149b56..725f0862a99 100644
--- a/components/style/properties/longhands/position.mako.rs
+++ b/components/style/properties/longhands/position.mako.rs
@@ -75,6 +75,7 @@ ${helpers.single_keyword(
     extra_prefixes="webkit",
     animation_value_type="discrete",
     servo_restyle_damage = "reflow",
+    gecko_enum_prefix = "StyleFlexDirection",
 )}
 
 ${helpers.single_keyword(
@@ -225,7 +226,7 @@ ${helpers.predefined_type(
     extra_prefixes="webkit",
     animation_value_type="ComputedValue",
     spec="https://drafts.csswg.org/css-flexbox/#order-property",
-    servo_restyle_damage = "reflow",
+    servo_restyle_damage="reflow",
 )}
 
 ${helpers.predefined_type(
@@ -235,7 +236,8 @@ ${helpers.predefined_type(
     spec="https://drafts.csswg.org/css-flexbox/#flex-basis-property",
     extra_prefixes="webkit",
     animation_value_type="FlexBasis",
-    servo_restyle_damage = "reflow",
+    servo_restyle_damage="reflow",
+    boxed=True,
 )}
 
 % for (size, logical) in ALL_SIZES:
diff --git a/components/style/properties/longhands/svg.mako.rs b/components/style/properties/longhands/svg.mako.rs
index f003fa5222e..1a84c1d669f 100644
--- a/components/style/properties/longhands/svg.mako.rs
+++ b/components/style/properties/longhands/svg.mako.rs
@@ -96,6 +96,7 @@ ${helpers.predefined_type(
 ${helpers.single_keyword(
     "mask-mode",
     "match-source alpha luminance",
+    gecko_enum_prefix="StyleMaskMode",
     vector=True,
     products="gecko",
     animation_value_type="discrete",
diff --git a/components/style/properties/properties.mako.rs b/components/style/properties/properties.mako.rs
index d818306e96c..7e35d318c30 100644
--- a/components/style/properties/properties.mako.rs
+++ b/components/style/properties/properties.mako.rs
@@ -3358,7 +3358,7 @@ impl<'a> StyleBuilder<'a> {
         debug_assert!(parent_style.is_none() ||
                       std::ptr::eq(parent_style.unwrap(),
                                      parent_style_ignoring_first_line.unwrap()) ||
-                      parent_style.unwrap().pseudo() == Some(PseudoElement::FirstLine));
+                      parent_style.unwrap().is_first_line_style());
         let reset_style = device.default_computed_values();
         let inherited_style = parent_style.unwrap_or(reset_style);
         let inherited_style_ignoring_first_line = parent_style_ignoring_first_line.unwrap_or(reset_style);
@@ -3402,7 +3402,7 @@ impl<'a> StyleBuilder<'a> {
         let inherited_style = parent_style.unwrap_or(reset_style);
         #[cfg(feature = "gecko")]
         debug_assert!(parent_style.is_none() ||
-                      parent_style.unwrap().pseudo() != Some(PseudoElement::FirstLine));
+                      !parent_style.unwrap().is_first_line_style());
         StyleBuilder {
             device,
             inherited_style,
@@ -3507,14 +3507,11 @@ impl<'a> StyleBuilder<'a> {
         self.modified_reset = true;
         % endif
 
-        <% props_need_device = ["content", "list_style_type", "font_variant_alternates"] %>
         self.${property.style_struct.ident}.mutate()
             .set_${property.ident}(
                 value,
                 % if property.logical:
                 self.writing_mode,
-                % elif product == "gecko" and property.ident in props_need_device:
-                self.device,
                 % endif
             );
     }
diff --git a/components/style/properties/shorthands/margin.mako.rs b/components/style/properties/shorthands/margin.mako.rs
index 8ccd33ebf3b..fd3124a6ae1 100644
--- a/components/style/properties/shorthands/margin.mako.rs
+++ b/components/style/properties/shorthands/margin.mako.rs
@@ -28,3 +28,32 @@ ${helpers.two_properties_shorthand(
     "specified::LengthPercentageOrAuto::parse",
     spec="https://drafts.csswg.org/css-logical/#propdef-margin-inline"
 )}
+
+${helpers.four_sides_shorthand(
+    "scroll-margin",
+    "scroll-margin-%s",
+    "specified::Length::parse",
+    spec="https://drafts.csswg.org/css-scroll-snap-1/#propdef-scroll-margin",
+    products="gecko",
+    gecko_pref="layout.css.scroll-snap-v1.enabled",
+)}
+
+${helpers.two_properties_shorthand(
+    "scroll-margin-block",
+    "scroll-margin-block-start",
+    "scroll-margin-block-end",
+    "specified::Length::parse",
+    spec="https://drafts.csswg.org/css-scroll-snap-1/#propdef-scroll-margin-block",
+    products="gecko",
+    gecko_pref="layout.css.scroll-snap-v1.enabled",
+)}
+
+${helpers.two_properties_shorthand(
+    "scroll-margin-inline",
+    "scroll-margin-inline-start",
+    "scroll-margin-inline-end",
+    "specified::Length::parse",
+    spec="https://drafts.csswg.org/css-scroll-snap-1/#propdef-scroll-margin-inline",
+    products="gecko",
+    gecko_pref="layout.css.scroll-snap-v1.enabled",
+)}
diff --git a/components/style/properties/shorthands/padding.mako.rs b/components/style/properties/shorthands/padding.mako.rs
index 3efc0b4a153..a4e013caabc 100644
--- a/components/style/properties/shorthands/padding.mako.rs
+++ b/components/style/properties/shorthands/padding.mako.rs
@@ -27,3 +27,33 @@ ${helpers.two_properties_shorthand(
     "specified::NonNegativeLengthPercentage::parse",
     spec="https://drafts.csswg.org/css-logical/#propdef-padding-inline"
 )}
+
+${helpers.four_sides_shorthand(
+    "scroll-padding",
+    "scroll-padding-%s",
+    "specified::NonNegativeLengthPercentageOrAuto::parse",
+    products="gecko",
+    gecko_pref="layout.css.scroll-snap-v1.enabled",
+    spec="https://drafts.csswg.org/css-scroll-snap-1/#propdef-scroll-padding"
+)}
+
+${helpers.two_properties_shorthand(
+    "scroll-padding-block",
+    "scroll-padding-block-start",
+    "scroll-padding-block-end",
+    "specified::NonNegativeLengthPercentageOrAuto::parse",
+    products="gecko",
+    gecko_pref="layout.css.scroll-snap-v1.enabled",
+    spec="https://drafts.csswg.org/css-scroll-snap-1/#propdef-scroll-padding-block"
+)}
+
+${helpers.two_properties_shorthand(
+    "scroll-padding-inline",
+    "scroll-padding-inline-start",
+    "scroll-padding-inline-end",
+    "specified::NonNegativeLengthPercentageOrAuto::parse",
+    products="gecko",
+    gecko_pref="layout.css.scroll-snap-v1.enabled",
+    spec="https://drafts.csswg.org/css-scroll-snap-1/#propdef-scroll-padding-inline"
+)}
+
diff --git a/components/style/sharing/mod.rs b/components/style/sharing/mod.rs
index c7be23572c6..0675359ed77 100644
--- a/components/style/sharing/mod.rs
+++ b/components/style/sharing/mod.rs
@@ -766,6 +766,11 @@ impl<E: TElement> StyleSharingCache<E> {
             return None;
         }
 
+        if target.element.has_animations() {
+            trace!("Miss: Has Animations");
+            return None;
+        }
+
         if target.matches_user_and_author_rules() !=
             candidate.element.matches_user_and_author_rules()
         {
diff --git a/components/style/stylesheets/document_rule.rs b/components/style/stylesheets/document_rule.rs
index 4813a0e9150..c73b96bcd9d 100644
--- a/components/style/stylesheets/document_rule.rs
+++ b/components/style/stylesheets/document_rule.rs
@@ -198,7 +198,7 @@ impl DocumentMatchingFunction {
                 MediaDocumentKind::Video => "video",
             },
         });
-        unsafe { Gecko_DocumentRule_UseForPresentation(device.pres_context(), &*pattern, func) }
+        unsafe { Gecko_DocumentRule_UseForPresentation(device.document(), &*pattern, func) }
     }
 
     #[cfg(not(feature = "gecko"))]
diff --git a/components/style/values/computed/background.rs b/components/style/values/computed/background.rs
index dc23915a74b..e2a58f8b74e 100644
--- a/components/style/values/computed/background.rs
+++ b/components/style/values/computed/background.rs
@@ -6,19 +6,8 @@
 
 use crate::values::computed::length::NonNegativeLengthPercentage;
 use crate::values::generics::background::BackgroundSize as GenericBackgroundSize;
-use crate::values::generics::length::LengthPercentageOrAuto;
 
 pub use crate::values::specified::background::BackgroundRepeat;
 
 /// A computed value for the `background-size` property.
 pub type BackgroundSize = GenericBackgroundSize<NonNegativeLengthPercentage>;
-
-impl BackgroundSize {
-    /// Returns `auto auto`.
-    pub fn auto() -> Self {
-        GenericBackgroundSize::Explicit {
-            width: LengthPercentageOrAuto::auto(),
-            height: LengthPercentageOrAuto::auto(),
-        }
-    }
-}
diff --git a/components/style/values/computed/box.rs b/components/style/values/computed/box.rs
index 46d3f93854e..decba9f342f 100644
--- a/components/style/values/computed/box.rs
+++ b/components/style/values/computed/box.rs
@@ -15,7 +15,7 @@ pub use crate::values::specified::box_::{AnimationName, Appearance, BreakBetween
 pub use crate::values::specified::box_::{Clear as SpecifiedClear, Float as SpecifiedFloat};
 pub use crate::values::specified::box_::{Contain, Display, Overflow};
 pub use crate::values::specified::box_::{OverflowAnchor, OverflowClipBox};
-pub use crate::values::specified::box_::{OverscrollBehavior, ScrollSnapType};
+pub use crate::values::specified::box_::{OverscrollBehavior, ScrollSnapAlign, ScrollSnapType};
 pub use crate::values::specified::box_::{TouchAction, TransitionProperty, WillChange};
 
 /// A computed value for the `vertical-align` property.
diff --git a/components/style/values/computed/color.rs b/components/style/values/computed/color.rs
index 758d86be1b8..6795b399888 100644
--- a/components/style/values/computed/color.rs
+++ b/components/style/values/computed/color.rs
@@ -6,7 +6,7 @@
 
 use crate::values::animated::color::RGBA as AnimatedRGBA;
 use crate::values::animated::ToAnimatedValue;
-use crate::values::generics::color::Color as GenericColor;
+use crate::values::generics::color::{Color as GenericColor, ColorOrAuto as GenericColorOrAuto};
 use cssparser::{Color as CSSParserColor, RGBA};
 use std::fmt;
 use style_traits::{CssWriter, ToCss};
@@ -101,3 +101,6 @@ impl ToAnimatedValue for RGBA {
         RGBA::from_floats(animated.red, animated.green, animated.blue, animated.alpha)
     }
 }
+
+/// auto | <color>
+pub type ColorOrAuto = GenericColorOrAuto<Color>;
diff --git a/components/style/values/computed/flex.rs b/components/style/values/computed/flex.rs
index c0c2703732f..95c497ecf63 100644
--- a/components/style/values/computed/flex.rs
+++ b/components/style/values/computed/flex.rs
@@ -14,6 +14,6 @@ impl FlexBasis {
     /// `auto`
     #[inline]
     pub fn auto() -> Self {
-        GenericFlexBasis::Width(Size::auto())
+        GenericFlexBasis::Size(Size::auto())
     }
 }
diff --git a/components/style/values/computed/length.rs b/components/style/values/computed/length.rs
index 6cdf359d16a..f578bbbd5ce 100644
--- a/components/style/values/computed/length.rs
+++ b/components/style/values/computed/length.rs
@@ -6,9 +6,12 @@
 
 use super::{Context, Number, Percentage, ToComputedValue};
 use crate::values::animated::ToAnimatedValue;
+use crate::values::computed::NonNegativeNumber;
 use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
 use crate::values::generics::length as generics;
-use crate::values::generics::length::{MaxSize as GenericMaxSize, Size as GenericSize};
+use crate::values::generics::length::{
+    GenericLengthOrNumber, MaxSize as GenericMaxSize, Size as GenericSize,
+};
 use crate::values::generics::transform::IsZeroLength;
 use crate::values::generics::NonNegative;
 use crate::values::specified::length::ViewportPercentageLength;
@@ -503,7 +506,7 @@ impl LengthPercentageOrAuto {
 
 /// A wrapper of LengthPercentageOrAuto, whose value must be >= 0.
 pub type NonNegativeLengthPercentageOrAuto =
-    generics::LengthPercentageOrAuto<NonNegativeLengthPercentage>;
+    generics::GenericLengthPercentageOrAuto<NonNegativeLengthPercentage>;
 
 impl NonNegativeLengthPercentageOrAuto {
     computed_length_percentage_or_auto!(NonNegativeLengthPercentage);
@@ -678,6 +681,15 @@ impl ToCss for CSSPixelLength {
     }
 }
 
+impl Add for CSSPixelLength {
+    type Output = Self;
+
+    #[inline]
+    fn add(self, other: Self) -> Self {
+        Self::new(self.px() + other.px())
+    }
+}
+
 impl Neg for CSSPixelLength {
     type Output = Self;
 
@@ -708,15 +720,7 @@ pub type Length = CSSPixelLength;
 pub type LengthOrAuto = Either<Length, Auto>;
 
 /// Either a computed `<length>` or a `<number>` value.
-pub type LengthOrNumber = Either<Length, Number>;
-
-impl LengthOrNumber {
-    /// Returns `0`.
-    #[inline]
-    pub fn zero() -> Self {
-        Either::Second(0.)
-    }
-}
+pub type LengthOrNumber = GenericLengthOrNumber<Length, Number>;
 
 /// Either a computed `<length>` or the `normal` keyword.
 pub type LengthOrNormal = Either<Length, Normal>;
@@ -776,13 +780,6 @@ impl NonNegativeLength {
     }
 }
 
-impl Add<NonNegativeLength> for NonNegativeLength {
-    type Output = Self;
-    fn add(self, other: Self) -> Self {
-        NonNegativeLength::new(self.px() + other.px())
-    }
-}
-
 impl From<Length> for NonNegativeLength {
     #[inline]
     fn from(len: Length) -> Self {
@@ -813,6 +810,9 @@ pub type NonNegativeLengthOrNormal = Either<NonNegativeLength, Normal>;
 /// Either a computed NonNegativeLengthPercentage or the `normal` keyword.
 pub type NonNegativeLengthPercentageOrNormal = Either<NonNegativeLengthPercentage, Normal>;
 
+/// Either a non-negative `<length>` or a `<number>`.
+pub type NonNegativeLengthOrNumber = GenericLengthOrNumber<NonNegativeLength, NonNegativeNumber>;
+
 /// A type for possible values for min- and max- flavors of width, height,
 /// block-size, and inline-size.
 #[allow(missing_docs)]
diff --git a/components/style/values/computed/mod.rs b/components/style/values/computed/mod.rs
index 8158e1a16d7..6fe36d684f2 100644
--- a/components/style/values/computed/mod.rs
+++ b/components/style/values/computed/mod.rs
@@ -44,8 +44,8 @@ pub use self::box_::{AnimationIterationCount, AnimationName, Contain};
 pub use self::box_::{Appearance, BreakBetween, BreakWithin, Clear, Float};
 pub use self::box_::{Display, Overflow, OverflowAnchor, TransitionProperty};
 pub use self::box_::{OverflowClipBox, OverscrollBehavior, Perspective, Resize};
-pub use self::box_::{ScrollSnapType, TouchAction, VerticalAlign, WillChange};
-pub use self::color::{Color, ColorPropertyValue, RGBAColor};
+pub use self::box_::{ScrollSnapAlign, ScrollSnapType, TouchAction, VerticalAlign, WillChange};
+pub use self::color::{Color, ColorOrAuto, ColorPropertyValue, RGBAColor};
 pub use self::column::ColumnCount;
 pub use self::counters::{Content, ContentItem, CounterIncrement, CounterReset};
 pub use self::easing::TimingFunction;
@@ -61,7 +61,7 @@ pub use self::font::{MozScriptLevel, MozScriptMinSize, MozScriptSizeMultiplier,
 pub use self::gecko::ScrollSnapPoint;
 pub use self::image::{Gradient, GradientItem, Image, ImageLayer, LineDirection, MozImageRect};
 pub use self::length::{CSSPixelLength, ExtremumLength, NonNegativeLength};
-pub use self::length::{Length, LengthOrNumber, LengthPercentage};
+pub use self::length::{Length, LengthOrNumber, LengthPercentage, NonNegativeLengthOrNumber};
 pub use self::length::{LengthPercentageOrAuto, MaxSize, Size};
 pub use self::length::{NonNegativeLengthPercentage, NonNegativeLengthPercentageOrAuto};
 #[cfg(feature = "gecko")]
@@ -71,13 +71,13 @@ pub use self::motion::OffsetPath;
 pub use self::outline::OutlineStyle;
 pub use self::percentage::{NonNegativePercentage, Percentage};
 pub use self::position::{GridAutoFlow, GridTemplateAreas, Position, ZIndex};
-pub use self::rect::LengthOrNumberRect;
+pub use self::rect::NonNegativeLengthOrNumberRect;
 pub use self::resolution::Resolution;
 pub use self::svg::MozContextProperties;
 pub use self::svg::{SVGLength, SVGOpacity, SVGPaint, SVGPaintKind};
 pub use self::svg::{SVGPaintOrder, SVGStrokeDashArray, SVGWidth};
 pub use self::table::XSpan;
-pub use self::text::{InitialLetter, LetterSpacing, LineHeight, MozTabSize};
+pub use self::text::{InitialLetter, LetterSpacing, LineHeight};
 pub use self::text::{OverflowWrap, TextOverflow, WordSpacing};
 pub use self::text::{TextAlign, TextEmphasisPosition, TextEmphasisStyle};
 pub use self::time::Time;
@@ -85,7 +85,7 @@ pub use self::transform::{Rotate, Scale, Transform, TransformOperation};
 pub use self::transform::{TransformOrigin, TransformStyle, Translate};
 #[cfg(feature = "gecko")]
 pub use self::ui::CursorImage;
-pub use self::ui::{ColorOrAuto, Cursor, MozForceBrokenImageIcon, UserSelect};
+pub use self::ui::{Cursor, MozForceBrokenImageIcon, UserSelect};
 pub use super::specified::{BorderStyle, TextDecorationLine};
 pub use super::{Auto, Either, None_};
 pub use app_units::Au;
@@ -536,6 +536,7 @@ impl From<GreaterThanOrEqualToOneNumber> for CSSFloat {
 
 #[allow(missing_docs)]
 #[derive(Clone, ComputeSquaredDistance, Copy, Debug, MallocSizeOf, PartialEq, ToCss)]
+#[repr(C, u8)]
 pub enum NumberOrPercentage {
     Percentage(Percentage),
     Number(Number),
diff --git a/components/style/values/computed/rect.rs b/components/style/values/computed/rect.rs
index 40b722ade21..ec44360fc81 100644
--- a/components/style/values/computed/rect.rs
+++ b/components/style/values/computed/rect.rs
@@ -4,8 +4,8 @@
 
 //! Computed types for CSS borders.
 
-use crate::values::computed::length::LengthOrNumber;
+use crate::values::computed::length::NonNegativeLengthOrNumber;
 use crate::values::generics::rect::Rect;
 
 /// A specified rectangle made of four `<length-or-number>` values.
-pub type LengthOrNumberRect = Rect<LengthOrNumber>;
+pub type NonNegativeLengthOrNumberRect = Rect<NonNegativeLengthOrNumber>;
diff --git a/components/style/values/computed/text.rs b/components/style/values/computed/text.rs
index 030a6df6cff..2c9a9593ecc 100644
--- a/components/style/values/computed/text.rs
+++ b/components/style/values/computed/text.rs
@@ -10,7 +10,6 @@ use crate::values::computed::length::{Length, LengthPercentage};
 use crate::values::computed::{NonNegativeLength, NonNegativeNumber};
 use crate::values::generics::text::InitialLetter as GenericInitialLetter;
 use crate::values::generics::text::LineHeight as GenericLineHeight;
-use crate::values::generics::text::MozTabSize as GenericMozTabSize;
 use crate::values::generics::text::Spacing;
 use crate::values::specified::text::TextOverflowSide;
 use crate::values::specified::text::{TextEmphasisFillMode, TextEmphasisShapeKeyword};
@@ -124,9 +123,6 @@ impl TextDecorationsInEffect {
     }
 }
 
-/// A specified value for the `-moz-tab-size` property.
-pub type MozTabSize = GenericMozTabSize<NonNegativeNumber, NonNegativeLength>;
-
 /// computed value for the text-emphasis-style property
 #[derive(Clone, Debug, MallocSizeOf, PartialEq, ToCss)]
 pub enum TextEmphasisStyle {
diff --git a/components/style/values/computed/transform.rs b/components/style/values/computed/transform.rs
index 979886aa996..dd3fe20754c 100644
--- a/components/style/values/computed/transform.rs
+++ b/components/style/values/computed/transform.rs
@@ -21,7 +21,8 @@ pub type TransformOperation =
 pub type Transform = generic::Transform<TransformOperation>;
 
 /// The computed value of a CSS `<transform-origin>`
-pub type TransformOrigin = generic::TransformOrigin<LengthPercentage, LengthPercentage, Length>;
+pub type TransformOrigin =
+    generic::GenericTransformOrigin<LengthPercentage, LengthPercentage, Length>;
 
 /// A vector to represent the direction vector (rotate axis) for Rotate3D.
 pub type DirectionVector = Vector3D<CSSFloat>;
diff --git a/components/style/values/computed/ui.rs b/components/style/values/computed/ui.rs
index ef19b975494..0c37ea4f518 100644
--- a/components/style/values/computed/ui.rs
+++ b/components/style/values/computed/ui.rs
@@ -8,14 +8,10 @@ use crate::values::computed::color::Color;
 use crate::values::computed::url::ComputedImageUrl;
 use crate::values::computed::Number;
 use crate::values::generics::ui as generics;
-use crate::values::{Auto, Either};
 
 pub use crate::values::specified::ui::CursorKind;
 pub use crate::values::specified::ui::{MozForceBrokenImageIcon, UserSelect};
 
-/// auto | <color>
-pub type ColorOrAuto = Either<Color, Auto>;
-
 /// A computed value for the `cursor` property.
 pub type Cursor = generics::Cursor<CursorImage>;
 
diff --git a/components/style/values/generics/background.rs b/components/style/values/generics/background.rs
index d739329e4fc..14ac9744b14 100644
--- a/components/style/values/generics/background.rs
+++ b/components/style/values/generics/background.rs
@@ -4,7 +4,7 @@
 
 //! Generic types for CSS values related to backgrounds.
 
-use crate::values::generics::length::LengthPercentageOrAuto;
+use crate::values::generics::length::{GenericLengthPercentageOrAuto, LengthPercentageOrAuto};
 use std::fmt::{self, Write};
 use style_traits::{CssWriter, ToCss};
 
@@ -22,13 +22,14 @@ use style_traits::{CssWriter, ToCss};
     ToAnimatedZero,
     ToComputedValue,
 )]
-pub enum BackgroundSize<LengthPercentage> {
+#[repr(C, u8)]
+pub enum GenericBackgroundSize<LengthPercent> {
     /// `<width> <height>`
-    Explicit {
+    ExplicitSize {
         /// Explicit width.
-        width: LengthPercentageOrAuto<LengthPercentage>,
+        width: GenericLengthPercentageOrAuto<LengthPercent>,
         /// Explicit height.
-        height: LengthPercentageOrAuto<LengthPercentage>,
+        height: GenericLengthPercentageOrAuto<LengthPercent>,
     },
     /// `cover`
     #[animation(error)]
@@ -38,6 +39,8 @@ pub enum BackgroundSize<LengthPercentage> {
     Contain,
 }
 
+pub use self::GenericBackgroundSize as BackgroundSize;
+
 impl<LengthPercentage> ToCss for BackgroundSize<LengthPercentage>
 where
     LengthPercentage: ToCss,
@@ -47,7 +50,7 @@ where
         W: Write,
     {
         match self {
-            BackgroundSize::Explicit { width, height } => {
+            BackgroundSize::ExplicitSize { width, height } => {
                 width.to_css(dest)?;
                 // NOTE(emilio): We should probably simplify all these in case
                 // `width == `height`, but all other browsers agree on only
@@ -63,3 +66,13 @@ where
         }
     }
 }
+
+impl<LengthPercentage> BackgroundSize<LengthPercentage> {
+    /// Returns `auto auto`.
+    pub fn auto() -> Self {
+        GenericBackgroundSize::ExplicitSize {
+            width: LengthPercentageOrAuto::Auto,
+            height: LengthPercentageOrAuto::Auto,
+        }
+    }
+}
diff --git a/components/style/values/generics/border.rs b/components/style/values/generics/border.rs
index 0a1cef3b4bb..ffd30e98678 100644
--- a/components/style/values/generics/border.rs
+++ b/components/style/values/generics/border.rs
@@ -26,7 +26,8 @@ pub enum BorderImageSideWidth<LengthPercentage, Number> {
 #[derive(
     Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToComputedValue, ToCss,
 )]
-pub struct BorderImageSlice<NumberOrPercentage> {
+#[repr(C)]
+pub struct GenericBorderImageSlice<NumberOrPercentage> {
     /// The offsets.
     #[css(field_bound)]
     pub offsets: Rect<NumberOrPercentage>,
@@ -35,6 +36,8 @@ pub struct BorderImageSlice<NumberOrPercentage> {
     pub fill: bool,
 }
 
+pub use self::GenericBorderImageSlice as BorderImageSlice;
+
 /// A generic value for the `border-*-radius` longhand properties.
 #[derive(
     Animate,
diff --git a/components/style/values/generics/box.rs b/components/style/values/generics/box.rs
index 8a8dc58fd92..f49cba4c2e1 100644
--- a/components/style/values/generics/box.rs
+++ b/components/style/values/generics/box.rs
@@ -74,6 +74,7 @@ pub enum AnimationIterationCount<Number> {
     Copy,
     Debug,
     MallocSizeOf,
+    Parse,
     PartialEq,
     SpecifiedValueInfo,
     ToAnimatedValue,
@@ -81,13 +82,16 @@ pub enum AnimationIterationCount<Number> {
     ToComputedValue,
     ToCss,
 )]
-pub enum Perspective<NonNegativeLength> {
+#[repr(C, u8)]
+pub enum GenericPerspective<NonNegativeLength> {
     /// A non-negative length.
     Length(NonNegativeLength),
     /// The keyword `none`.
     None,
 }
 
+pub use self::GenericPerspective as Perspective;
+
 impl<L> Perspective<L> {
     /// Returns `none`.
     #[inline]
diff --git a/components/style/values/generics/color.rs b/components/style/values/generics/color.rs
index 594df927ca9..58e4e9fa97c 100644
--- a/components/style/values/generics/color.rs
+++ b/components/style/values/generics/color.rs
@@ -74,3 +74,26 @@ impl<RGBA> From<RGBA> for Color<RGBA> {
         Self::rgba(color)
     }
 }
+
+/// Either `<color>` or `auto`.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    Parse,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+)]
+pub enum ColorOrAuto<C> {
+    /// A `<color>
+    Color(C),
+    /// `auto`
+    Auto,
+}
diff --git a/components/style/values/generics/column.rs b/components/style/values/generics/column.rs
index d27e47ed4c7..6f8c9daef5b 100644
--- a/components/style/values/generics/column.rs
+++ b/components/style/values/generics/column.rs
@@ -12,6 +12,7 @@
     Copy,
     Debug,
     MallocSizeOf,
+    Parse,
     PartialEq,
     SpecifiedValueInfo,
     ToAnimatedValue,
diff --git a/components/style/values/generics/flex.rs b/components/style/values/generics/flex.rs
index 31e32a91f81..de67b56e35b 100644
--- a/components/style/values/generics/flex.rs
+++ b/components/style/values/generics/flex.rs
@@ -12,6 +12,7 @@
     ComputeSquaredDistance,
     Copy,
     Debug,
+    Parse,
     PartialEq,
     SpecifiedValueInfo,
     ToAnimatedValue,
@@ -19,9 +20,12 @@
     ToComputedValue,
     ToCss,
 )]
-pub enum FlexBasis<Width> {
+#[repr(C)]
+pub enum GenericFlexBasis<S> {
     /// `content`
     Content,
     /// `<width>`
-    Width(Width),
+    Size(S),
 }
+
+pub use self::GenericFlexBasis as FlexBasis;
diff --git a/components/style/values/generics/grid.rs b/components/style/values/generics/grid.rs
index 7dbee9b8dbe..6650996c794 100644
--- a/components/style/values/generics/grid.rs
+++ b/components/style/values/generics/grid.rs
@@ -192,10 +192,7 @@ impl<L> TrackBreadth<L> {
     /// <https://drafts.csswg.org/css-grid/#typedef-fixed-breadth>
     #[inline]
     pub fn is_fixed(&self) -> bool {
-        match *self {
-            TrackBreadth::Breadth(ref _lp) => true,
-            _ => false,
-        }
+        matches!(*self, TrackBreadth::Breadth(..))
     }
 }
 
diff --git a/components/style/values/generics/length.rs b/components/style/values/generics/length.rs
index f55db4f52c5..1a83f58054c 100644
--- a/components/style/values/generics/length.rs
+++ b/components/style/values/generics/length.rs
@@ -8,6 +8,7 @@ use crate::parser::{Parse, ParserContext};
 #[cfg(feature = "gecko")]
 use crate::values::computed::ExtremumLength;
 use cssparser::Parser;
+use num_traits::Zero;
 use style_traits::ParseError;
 
 /// A `<length-percentage> | auto` value.
@@ -96,14 +97,17 @@ impl<LengthPercentage: Parse> Parse for LengthPercentageOrAuto<LengthPercentage>
     ToComputedValue,
     ToCss,
 )]
-pub enum Size<LengthPercentage> {
-    LengthPercentage(LengthPercentage),
+#[repr(C, u8)]
+pub enum GenericSize<LengthPercent> {
+    LengthPercentage(LengthPercent),
     Auto,
     #[cfg(feature = "gecko")]
     #[animation(error)]
     ExtremumLength(ExtremumLength),
 }
 
+pub use self::GenericSize as Size;
+
 impl<LengthPercentage> Size<LengthPercentage> {
     /// `auto` value.
     #[inline]
@@ -134,14 +138,17 @@ impl<LengthPercentage> Size<LengthPercentage> {
     ToComputedValue,
     ToCss,
 )]
-pub enum MaxSize<LengthPercentage> {
-    LengthPercentage(LengthPercentage),
+#[repr(C, u8)]
+pub enum GenericMaxSize<LengthPercent> {
+    LengthPercentage(LengthPercent),
     None,
     #[cfg(feature = "gecko")]
     #[animation(error)]
     ExtremumLength(ExtremumLength),
 }
 
+pub use self::GenericMaxSize as MaxSize;
+
 impl<LengthPercentage> MaxSize<LengthPercentage> {
     /// `none` value.
     #[inline]
@@ -149,3 +156,42 @@ impl<LengthPercentage> MaxSize<LengthPercentage> {
         MaxSize::None
     }
 }
+
+/// A generic `<length>` | `<number>` value for the `-moz-tab-size` property.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+)]
+#[repr(C, u8)]
+pub enum GenericLengthOrNumber<L, N> {
+    /// A number.
+    ///
+    /// NOTE: Numbers need to be before lengths, in order to parse them
+    /// first, since `0` should be a number, not the `0px` length.
+    Number(N),
+    /// A length.
+    Length(L),
+}
+
+pub use self::GenericLengthOrNumber as LengthOrNumber;
+
+impl<L, N> LengthOrNumber<L, N> {
+    /// Returns `0`.
+    pub fn zero() -> Self
+    where
+        N: Zero,
+    {
+        LengthOrNumber::Number(num_traits::Zero::zero())
+    }
+}
diff --git a/components/style/values/generics/mod.rs b/components/style/values/generics/mod.rs
index a5c8c957073..737c88e7ba7 100644
--- a/components/style/values/generics/mod.rs
+++ b/components/style/values/generics/mod.rs
@@ -9,6 +9,8 @@ use super::CustomIdent;
 use crate::counter_style::{parse_counter_style_name, Symbols};
 use crate::parser::{Parse, ParserContext};
 use cssparser::Parser;
+use num_traits::Zero;
+use std::ops::Add;
 use style_traits::{KeywordsCollectFn, ParseError};
 use style_traits::{SpecifiedValueInfo, StyleParseErrorKind};
 
@@ -117,27 +119,25 @@ impl Parse for CounterStyleOrNone {
         if input.try(|i| i.expect_ident_matching("none")).is_ok() {
             return Ok(CounterStyleOrNone::None);
         }
-        if input.try(|i| i.expect_function_matching("symbols")).is_ok() {
-            return input.parse_nested_block(|input| {
-                let symbols_type = input
-                    .try(|i| SymbolsType::parse(i))
-                    .unwrap_or(SymbolsType::Symbolic);
-                let symbols = Symbols::parse(context, input)?;
-                // There must be at least two symbols for alphabetic or
-                // numeric system.
-                if (symbols_type == SymbolsType::Alphabetic ||
-                    symbols_type == SymbolsType::Numeric) && symbols.0.len() < 2
-                {
-                    return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
-                }
-                // Identifier is not allowed in symbols() function.
-                if symbols.0.iter().any(|sym| !sym.is_allowed_in_symbols()) {
-                    return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
-                }
-                Ok(CounterStyleOrNone::Symbols(symbols_type, symbols))
-            });
-        }
-        Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+        input.expect_function_matching("symbols")?;
+        input.parse_nested_block(|input| {
+            let symbols_type = input
+                .try(SymbolsType::parse)
+                .unwrap_or(SymbolsType::Symbolic);
+            let symbols = Symbols::parse(context, input)?;
+            // There must be at least two symbols for alphabetic or
+            // numeric system.
+            if (symbols_type == SymbolsType::Alphabetic || symbols_type == SymbolsType::Numeric) &&
+                symbols.0.len() < 2
+            {
+                return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+            }
+            // Identifier is not allowed in symbols() function.
+            if symbols.0.iter().any(|sym| !sym.is_allowed_in_symbols()) {
+                return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+            }
+            Ok(CounterStyleOrNone::Symbols(symbols_type, symbols))
+        })
     }
 }
 
@@ -177,6 +177,24 @@ impl SpecifiedValueInfo for CounterStyleOrNone {
 #[repr(transparent)]
 pub struct NonNegative<T>(pub T);
 
+impl<T: Add<Output = T>> Add<NonNegative<T>> for NonNegative<T> {
+    type Output = Self;
+
+    fn add(self, other: Self) -> Self {
+        NonNegative(self.0 + other.0)
+    }
+}
+
+impl<T: Zero> Zero for NonNegative<T> {
+    fn is_zero(&self) -> bool {
+        self.0.is_zero()
+    }
+
+    fn zero() -> Self {
+        NonNegative(T::zero())
+    }
+}
+
 /// A wrapper of greater-than-or-equal-to-one values.
 #[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
 #[derive(
diff --git a/components/style/values/generics/position.rs b/components/style/values/generics/position.rs
index 07612913c0a..34034b7d5b7 100644
--- a/components/style/values/generics/position.rs
+++ b/components/style/values/generics/position.rs
@@ -19,19 +19,22 @@
     ToAnimatedZero,
     ToComputedValue,
 )]
-pub struct Position<H, V> {
+#[repr(C)]
+pub struct GenericPosition<H, V> {
     /// The horizontal component of position.
     pub horizontal: H,
     /// The vertical component of position.
     pub vertical: V,
 }
 
+pub use self::GenericPosition as Position;
+
 impl<H, V> Position<H, V> {
     /// Returns a new position.
     pub fn new(horizontal: H, vertical: V) -> Self {
         Self {
-            horizontal: horizontal,
-            vertical: vertical,
+            horizontal,
+            vertical,
         }
     }
 }
@@ -45,18 +48,22 @@ impl<H, V> Position<H, V> {
     Debug,
     MallocSizeOf,
     PartialEq,
+    Parse,
     SpecifiedValueInfo,
     ToAnimatedZero,
     ToComputedValue,
     ToCss,
 )]
-pub enum ZIndex<Integer> {
+#[repr(C, u8)]
+pub enum GenericZIndex<I> {
     /// An integer value.
-    Integer(Integer),
+    Integer(I),
     /// The keyword `auto`.
     Auto,
 }
 
+pub use self::GenericZIndex as ZIndex;
+
 impl<Integer> ZIndex<Integer> {
     /// Returns `auto`
     #[inline]
diff --git a/components/style/values/generics/svg.rs b/components/style/values/generics/svg.rs
index 914de88999c..7f52126a748 100644
--- a/components/style/values/generics/svg.rs
+++ b/components/style/values/generics/svg.rs
@@ -136,6 +136,7 @@ impl<ColorType: Parse, UrlPaintServer: Parse> Parse for SVGPaint<ColorType, UrlP
     Debug,
     MallocSizeOf,
     PartialEq,
+    Parse,
     SpecifiedValueInfo,
     ToAnimatedValue,
     ToAnimatedZero,
@@ -143,28 +144,26 @@ impl<ColorType: Parse, UrlPaintServer: Parse> Parse for SVGPaint<ColorType, UrlP
     ToCss,
 )]
 pub enum SvgLengthPercentageOrNumber<LengthPercentage, Number> {
-    /// <length> | <percentage>
-    LengthPercentage(LengthPercentage),
     /// <number>
+    ///
+    /// Note that this needs to be before, so it gets parsed before the length,
+    /// to handle `0` correctly as a number instead of a `<length>`.
     Number(Number),
+    /// <length> | <percentage>
+    LengthPercentage(LengthPercentage),
 }
 
-/// Parsing the SvgLengthPercentageOrNumber. At first, we need to parse number
-/// since prevent converting to the length.
-impl<LengthPercentageType: Parse, NumberType: Parse> Parse
-    for SvgLengthPercentageOrNumber<LengthPercentageType, NumberType>
-{
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        if let Ok(num) = input.try(|i| NumberType::parse(context, i)) {
-            return Ok(SvgLengthPercentageOrNumber::Number(num));
-        }
+/// Whether the `context-value` value is enabled.
+#[cfg(feature = "gecko")]
+pub fn is_context_value_enabled(_: &ParserContext) -> bool {
+    use crate::gecko_bindings::structs::mozilla;
+    unsafe { mozilla::StaticPrefs_sVarCache_gfx_font_rendering_opentype_svg_enabled }
+}
 
-        let lp = LengthPercentageType::parse(context, input)?;
-        Ok(SvgLengthPercentageOrNumber::LengthPercentage(lp))
-    }
+/// Whether the `context-value` value is enabled.
+#[cfg(not(feature = "gecko"))]
+pub fn is_context_value_enabled(_: &ParserContext) -> bool {
+    false
 }
 
 /// An SVG length value supports `context-value` in addition to length.
@@ -175,6 +174,7 @@ impl<LengthPercentageType: Parse, NumberType: Parse> Parse
     Debug,
     MallocSizeOf,
     PartialEq,
+    Parse,
     SpecifiedValueInfo,
     ToAnimatedValue,
     ToAnimatedZero,
@@ -185,6 +185,7 @@ pub enum SVGLength<LengthType> {
     /// `<length> | <percentage> | <number>`
     Length(LengthType),
     /// `context-value`
+    #[parse(condition = "is_context_value_enabled")]
     ContextValue,
 }
 
@@ -216,6 +217,7 @@ pub enum SVGStrokeDashArray<LengthType> {
     Debug,
     MallocSizeOf,
     PartialEq,
+    Parse,
     SpecifiedValueInfo,
     ToAnimatedZero,
     ToComputedValue,
diff --git a/components/style/values/generics/text.rs b/components/style/values/generics/text.rs
index 5a4f9213908..029c5681318 100644
--- a/components/style/values/generics/text.rs
+++ b/components/style/values/generics/text.rs
@@ -149,25 +149,3 @@ impl<N, L> LineHeight<N, L> {
         LineHeight::Normal
     }
 }
-
-/// A generic value for the `-moz-tab-size` property.
-#[derive(
-    Animate,
-    Clone,
-    ComputeSquaredDistance,
-    Copy,
-    Debug,
-    MallocSizeOf,
-    PartialEq,
-    SpecifiedValueInfo,
-    ToAnimatedValue,
-    ToAnimatedZero,
-    ToComputedValue,
-    ToCss,
-)]
-pub enum MozTabSize<Number, Length> {
-    /// A number.
-    Number(Number),
-    /// A length.
-    Length(Length),
-}
diff --git a/components/style/values/generics/transform.rs b/components/style/values/generics/transform.rs
index 4591f3addd2..6c60e76cbf6 100644
--- a/components/style/values/generics/transform.rs
+++ b/components/style/values/generics/transform.rs
@@ -83,7 +83,8 @@ impl<T: Into<f64>> From<Matrix3D<T>> for Transform3D<f64> {
     ToComputedValue,
     ToCss,
 )]
-pub struct TransformOrigin<H, V, Depth> {
+#[repr(C)]
+pub struct GenericTransformOrigin<H, V, Depth> {
     /// The horizontal origin.
     pub horizontal: H,
     /// The vertical origin.
@@ -92,13 +93,15 @@ pub struct TransformOrigin<H, V, Depth> {
     pub depth: Depth,
 }
 
+pub use self::GenericTransformOrigin as TransformOrigin;
+
 impl<H, V, D> TransformOrigin<H, V, D> {
     /// Returns a new transform origin.
     pub fn new(horizontal: H, vertical: V, depth: D) -> Self {
         Self {
-            horizontal: horizontal,
-            vertical: vertical,
-            depth: depth,
+            horizontal,
+            vertical,
+            depth,
         }
     }
 }
diff --git a/components/style/values/generics/url.rs b/components/style/values/generics/url.rs
index a1f1aeb1884..80fa48ba882 100644
--- a/components/style/values/generics/url.rs
+++ b/components/style/values/generics/url.rs
@@ -4,10 +4,6 @@
 
 //! Generic types for url properties.
 
-use crate::parser::{Parse, ParserContext};
-use cssparser::Parser;
-use style_traits::ParseError;
-
 /// An image url or none, used for example in list-style-image
 #[derive(
     Animate,
@@ -16,6 +12,7 @@ use style_traits::ParseError;
     Debug,
     MallocSizeOf,
     PartialEq,
+    Parse,
     SpecifiedValueInfo,
     ToAnimatedValue,
     ToAnimatedZero,
@@ -35,19 +32,3 @@ impl<Url> UrlOrNone<Url> {
         UrlOrNone::None
     }
 }
-
-impl<Url> Parse for UrlOrNone<Url>
-where
-    Url: Parse,
-{
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<UrlOrNone<Url>, ParseError<'i>> {
-        if let Ok(url) = input.try(|input| Url::parse(context, input)) {
-            return Ok(UrlOrNone::Url(url));
-        }
-        input.expect_ident_matching("none")?;
-        Ok(UrlOrNone::None)
-    }
-}
diff --git a/components/style/values/mod.rs b/components/style/values/mod.rs
index 659ff95b1a7..ccda0f290c1 100644
--- a/components/style/values/mod.rs
+++ b/components/style/values/mod.rs
@@ -125,6 +125,7 @@ impl Parse for Impossible {
     Copy,
     MallocSizeOf,
     PartialEq,
+    Parse,
     SpecifiedValueInfo,
     ToAnimatedValue,
     ToAnimatedZero,
@@ -147,19 +148,6 @@ impl<A: Debug, B: Debug> Debug for Either<A, B> {
     }
 }
 
-impl<A: Parse, B: Parse> Parse for Either<A, B> {
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Either<A, B>, ParseError<'i>> {
-        if let Ok(v) = input.try(|i| A::parse(context, i)) {
-            Ok(Either::First(v))
-        } else {
-            B::parse(context, input).map(Either::Second)
-        }
-    }
-}
-
 /// <https://drafts.csswg.org/css-values-4/#custom-idents>
 #[derive(Clone, Debug, Eq, Hash, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToComputedValue)]
 pub struct CustomIdent(pub Atom);
diff --git a/components/style/values/specified/background.rs b/components/style/values/specified/background.rs
index b53669abfa8..a1605e977eb 100644
--- a/components/style/values/specified/background.rs
+++ b/components/style/values/specified/background.rs
@@ -26,7 +26,7 @@ impl Parse for BackgroundSize {
             let height = input
                 .try(|i| NonNegativeLengthPercentageOrAuto::parse(context, i))
                 .unwrap_or(NonNegativeLengthPercentageOrAuto::auto());
-            return Ok(GenericBackgroundSize::Explicit { width, height });
+            return Ok(GenericBackgroundSize::ExplicitSize { width, height });
         }
         Ok(try_match_ident_ignore_ascii_case! { input,
             "cover" => GenericBackgroundSize::Cover,
@@ -35,16 +35,6 @@ impl Parse for BackgroundSize {
     }
 }
 
-impl BackgroundSize {
-    /// Returns `auto auto`.
-    pub fn auto() -> Self {
-        GenericBackgroundSize::Explicit {
-            width: NonNegativeLengthPercentageOrAuto::auto(),
-            height: NonNegativeLengthPercentageOrAuto::auto(),
-        }
-    }
-}
-
 /// One of the keywords for `background-repeat`.
 #[derive(
     Clone,
diff --git a/components/style/values/specified/box.rs b/components/style/values/specified/box.rs
index b94ec8a0f26..2495cca3d6c 100644
--- a/components/style/values/specified/box.rs
+++ b/components/style/values/specified/box.rs
@@ -392,6 +392,76 @@ pub enum ScrollSnapType {
     Proximity,
 }
 
+/// Specified value of scroll-snap-align keyword value.
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    FromPrimitive,
+    Hash,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+)]
+#[repr(u8)]
+pub enum ScrollSnapAlignKeyword {
+    None,
+    Start,
+    End,
+    Center,
+}
+
+/// https://drafts.csswg.org/css-scroll-snap-1/#scroll-snap-align
+#[allow(missing_docs)]
+#[derive(Clone, Copy, Debug, Eq, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToComputedValue)]
+#[repr(C)]
+pub struct ScrollSnapAlign {
+    block: ScrollSnapAlignKeyword,
+    inline: ScrollSnapAlignKeyword,
+}
+
+impl ScrollSnapAlign {
+    /// Returns `none`.
+    #[inline]
+    pub fn none() -> Self {
+        ScrollSnapAlign {
+            block: ScrollSnapAlignKeyword::None,
+            inline: ScrollSnapAlignKeyword::None,
+        }
+    }
+}
+
+impl Parse for ScrollSnapAlign {
+    /// [ none | start | end | center ]{1,2}
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<ScrollSnapAlign, ParseError<'i>> {
+        let block = ScrollSnapAlignKeyword::parse(input)?;
+        let inline = input.try(ScrollSnapAlignKeyword::parse).unwrap_or(block);
+        Ok(ScrollSnapAlign { block, inline })
+    }
+}
+
+impl ToCss for ScrollSnapAlign {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.block.to_css(dest)?;
+        if self.block != self.inline {
+            dest.write_str(" ")?;
+            self.inline.to_css(dest)?;
+        }
+        Ok(())
+    }
+}
+
 #[allow(missing_docs)]
 #[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
 #[derive(
@@ -782,20 +852,6 @@ impl Parse for Contain {
 /// A specified value for the `perspective` property.
 pub type Perspective = GenericPerspective<NonNegativeLength>;
 
-impl Parse for Perspective {
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        if input.try(|i| i.expect_ident_matching("none")).is_ok() {
-            return Ok(GenericPerspective::None);
-        }
-        Ok(GenericPerspective::Length(NonNegativeLength::parse(
-            context, input,
-        )?))
-    }
-}
-
 /// A given transition property, that is either `All`, a longhand or shorthand
 /// property, or an unsupported or custom property.
 #[derive(Clone, Debug, Eq, Hash, MallocSizeOf, PartialEq, ToComputedValue)]
diff --git a/components/style/values/specified/color.rs b/components/style/values/specified/color.rs
index 97b450362b3..2ee159987f8 100644
--- a/components/style/values/specified/color.rs
+++ b/components/style/values/specified/color.rs
@@ -11,7 +11,7 @@ use crate::parser::{Parse, ParserContext};
 #[cfg(feature = "gecko")]
 use crate::properties::longhands::system_colors::SystemColor;
 use crate::values::computed::{Color as ComputedColor, Context, ToComputedValue};
-use crate::values::generics::color::Color as GenericColor;
+use crate::values::generics::color::{Color as GenericColor, ColorOrAuto as GenericColorOrAuto};
 use crate::values::specified::calc::CalcNode;
 use cssparser::{AngleOrNumber, Color as CSSParserColor, Parser, Token, RGBA};
 use cssparser::{BasicParseErrorKind, NumberOrPercentage, ParseErrorKind};
@@ -469,3 +469,6 @@ impl Parse for ColorPropertyValue {
         Color::parse_quirky(context, input, AllowQuirks::Yes).map(ColorPropertyValue)
     }
 }
+
+/// auto | <color>
+pub type ColorOrAuto = GenericColorOrAuto<Color>;
diff --git a/components/style/values/specified/column.rs b/components/style/values/specified/column.rs
index 5d612de437a..2dd7bb0144d 100644
--- a/components/style/values/specified/column.rs
+++ b/components/style/values/specified/column.rs
@@ -4,25 +4,8 @@
 
 //! Specified types for the column properties.
 
-use crate::parser::{Parse, ParserContext};
 use crate::values::generics::column::ColumnCount as GenericColumnCount;
 use crate::values::specified::PositiveInteger;
-use cssparser::Parser;
-use style_traits::ParseError;
 
 /// A specified type for `column-count` values.
 pub type ColumnCount = GenericColumnCount<PositiveInteger>;
-
-impl Parse for ColumnCount {
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        if input.try(|i| i.expect_ident_matching("auto")).is_ok() {
-            return Ok(GenericColumnCount::Auto);
-        }
-        Ok(GenericColumnCount::Integer(PositiveInteger::parse(
-            context, input,
-        )?))
-    }
-}
diff --git a/components/style/values/specified/flex.rs b/components/style/values/specified/flex.rs
index a1131dbff5f..7c767cdf34b 100644
--- a/components/style/values/specified/flex.rs
+++ b/components/style/values/specified/flex.rs
@@ -4,39 +4,22 @@
 
 //! Specified types for CSS values related to flexbox.
 
-use crate::parser::{Parse, ParserContext};
 use crate::values::generics::flex::FlexBasis as GenericFlexBasis;
 use crate::values::specified::Size;
-use cssparser::Parser;
-use style_traits::ParseError;
 
 /// A specified value for the `flex-basis` property.
 pub type FlexBasis = GenericFlexBasis<Size>;
 
-impl Parse for FlexBasis {
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        if let Ok(width) = input.try(|i| Size::parse(context, i)) {
-            return Ok(GenericFlexBasis::Width(width));
-        }
-        try_match_ident_ignore_ascii_case! { input,
-            "content" => Ok(GenericFlexBasis::Content),
-        }
-    }
-}
-
 impl FlexBasis {
     /// `auto`
     #[inline]
     pub fn auto() -> Self {
-        GenericFlexBasis::Width(Size::auto())
+        GenericFlexBasis::Size(Size::auto())
     }
 
     /// `0%`
     #[inline]
     pub fn zero_percent() -> Self {
-        GenericFlexBasis::Width(Size::zero_percent())
+        GenericFlexBasis::Size(Size::zero_percent())
     }
 }
diff --git a/components/style/values/specified/font.rs b/components/style/values/specified/font.rs
index 5d428656d40..0344af275ce 100644
--- a/components/style/values/specified/font.rs
+++ b/components/style/values/specified/font.rs
@@ -17,7 +17,7 @@ use crate::values::generics::font::{KeywordSize, VariationValue};
 use crate::values::generics::NonNegative;
 use crate::values::specified::length::{FontBaseSize, AU_PER_PT, AU_PER_PX};
 use crate::values::specified::{AllowQuirks, Angle, Integer, LengthPercentage};
-use crate::values::specified::{NoCalcLength, Number, Percentage};
+use crate::values::specified::{NoCalcLength, NonNegativeNumber, Number, Percentage};
 use crate::values::CustomIdent;
 use crate::Atom;
 use app_units::Au;
@@ -81,7 +81,7 @@ pub const MAX_FONT_WEIGHT: f32 = 1000.;
 /// A specified font-weight value.
 ///
 /// https://drafts.csswg.org/css-fonts-4/#propdef-font-weight
-#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss)]
+#[derive(Clone, Copy, Debug, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss)]
 pub enum FontWeight {
     /// `<font-weight-absolute>`
     Absolute(AbsoluteFontWeight),
@@ -111,22 +111,6 @@ impl FontWeight {
     }
 }
 
-impl Parse for FontWeight {
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<FontWeight, ParseError<'i>> {
-        if let Ok(absolute) = input.try(|input| AbsoluteFontWeight::parse(context, input)) {
-            return Ok(FontWeight::Absolute(absolute));
-        }
-
-        Ok(try_match_ident_ignore_ascii_case! { input,
-            "bolder" => FontWeight::Bolder,
-            "lighter" => FontWeight::Lighter,
-        })
-    }
-}
-
 impl ToComputedValue for FontWeight {
     type ComputedValue = computed::FontWeight;
 
@@ -335,7 +319,7 @@ impl SpecifiedFontStyle {
 }
 
 /// The specified value of the `font-style` property.
-#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss)]
+#[derive(Clone, Copy, Debug, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss)]
 #[allow(missing_docs)]
 pub enum FontStyle {
     Specified(SpecifiedFontStyle),
@@ -368,20 +352,11 @@ impl ToComputedValue for FontStyle {
     }
 }
 
-impl Parse for FontStyle {
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        Ok(FontStyle::Specified(SpecifiedFontStyle::parse(
-            context, input,
-        )?))
-    }
-}
-
 /// A value for the `font-stretch` property.
 ///
 /// https://drafts.csswg.org/css-fonts-4/#font-stretch-prop
+///
+/// TODO(emilio): We could derive Parse if we had NonNegativePercentage.
 #[allow(missing_docs)]
 #[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss)]
 #[repr(u8)]
@@ -628,13 +603,13 @@ impl Parse for FamilyName {
     }
 }
 
-#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss)]
+#[derive(Clone, Copy, Debug, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss)]
 /// Preserve the readability of text when font fallback occurs
 pub enum FontSizeAdjust {
     /// None variant
     None,
     /// Number variant
-    Number(Number),
+    Number(NonNegativeNumber),
     /// system font
     #[css(skip)]
     System(SystemFont),
@@ -657,7 +632,9 @@ impl ToComputedValue for FontSizeAdjust {
         match *self {
             FontSizeAdjust::None => computed::FontSizeAdjust::None,
             FontSizeAdjust::Number(ref n) => {
-                computed::FontSizeAdjust::Number(n.to_computed_value(context))
+                // The computed version handles clamping of animated values
+                // itself.
+                computed::FontSizeAdjust::Number(n.to_computed_value(context).0)
             },
             FontSizeAdjust::System(_) => self.compute_system(context),
         }
@@ -666,32 +643,13 @@ impl ToComputedValue for FontSizeAdjust {
     fn from_computed_value(computed: &computed::FontSizeAdjust) -> Self {
         match *computed {
             computed::FontSizeAdjust::None => FontSizeAdjust::None,
-            computed::FontSizeAdjust::Number(ref v) => {
-                FontSizeAdjust::Number(Number::from_computed_value(v))
+            computed::FontSizeAdjust::Number(v) => {
+                FontSizeAdjust::Number(NonNegativeNumber::from_computed_value(&v.into()))
             },
         }
     }
 }
 
-impl Parse for FontSizeAdjust {
-    /// none | <number>
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<FontSizeAdjust, ParseError<'i>> {
-        if input
-            .try(|input| input.expect_ident_matching("none"))
-            .is_ok()
-        {
-            return Ok(FontSizeAdjust::None);
-        }
-
-        Ok(FontSizeAdjust::Number(Number::parse_non_negative(
-            context, input,
-        )?))
-    }
-}
-
 /// Additional information for specified keyword-derived font sizes.
 pub type KeywordInfo = generics::KeywordInfo<NonNegativeLength>;
 
diff --git a/components/style/values/specified/image.rs b/components/style/values/specified/image.rs
index 2dc56f8ad3f..c9d0f10215d 100644
--- a/components/style/values/specified/image.rs
+++ b/components/style/values/specified/image.rs
@@ -305,7 +305,7 @@ impl Gradient {
     ) -> Result<Self, ParseError<'i>> {
         type Point = GenericPosition<Component<X>, Component<Y>>;
 
-        #[derive(Clone, Copy)]
+        #[derive(Clone, Copy, Parse)]
         enum Component<S> {
             Center,
             Number(NumberOrPercentage),
@@ -408,22 +408,6 @@ impl Gradient {
             }
         }
 
-        impl<S: Parse> Parse for Component<S> {
-            fn parse<'i, 't>(
-                context: &ParserContext,
-                input: &mut Parser<'i, 't>,
-            ) -> Result<Self, ParseError<'i>> {
-                if let Ok(side) = input.try(|i| S::parse(context, i)) {
-                    return Ok(Component::Side(side));
-                }
-                if let Ok(number) = input.try(|i| NumberOrPercentage::parse(context, i)) {
-                    return Ok(Component::Number(number));
-                }
-                input.try(|i| i.expect_ident_matching("center"))?;
-                Ok(Component::Center)
-            }
-        }
-
         let ident = input.expect_ident_cloned()?;
         input.expect_comma()?;
 
diff --git a/components/style/values/specified/length.rs b/components/style/values/specified/length.rs
index 597aa990f0c..a8cae981993 100644
--- a/components/style/values/specified/length.rs
+++ b/components/style/values/specified/length.rs
@@ -11,10 +11,13 @@ use crate::font_metrics::FontMetricsQueryResult;
 use crate::parser::{Parse, ParserContext};
 use crate::values::computed::{self, CSSPixelLength, Context};
 use crate::values::generics::length as generics;
-use crate::values::generics::length::{MaxSize as GenericMaxSize, Size as GenericSize};
+use crate::values::generics::length::{
+    GenericLengthOrNumber, MaxSize as GenericMaxSize, Size as GenericSize,
+};
 use crate::values::generics::transform::IsZeroLength;
 use crate::values::generics::NonNegative;
 use crate::values::specified::calc::CalcNode;
+use crate::values::specified::NonNegativeNumber;
 use crate::values::{Auto, CSSFloat, Either, Normal};
 use app_units::Au;
 use cssparser::{Parser, Token};
@@ -1023,30 +1026,7 @@ pub type LengthOrNormal = Either<Length, Normal>;
 pub type LengthOrAuto = Either<Length, Auto>;
 
 /// Either a `<length>` or a `<number>`.
-pub type LengthOrNumber = Either<Length, Number>;
-
-impl LengthOrNumber {
-    /// Parse a non-negative LengthOrNumber.
-    pub fn parse_non_negative<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        // We try to parse as a Number first because, for cases like
-        // LengthOrNumber, we want "0" to be parsed as a plain Number rather
-        // than a Length (0px); this matches the behaviour of all major browsers
-        if let Ok(v) = input.try(|i| Number::parse_non_negative(context, i)) {
-            return Ok(Either::Second(v));
-        }
-
-        Length::parse_non_negative(context, input).map(Either::First)
-    }
-
-    /// Returns `0`.
-    #[inline]
-    pub fn zero() -> Self {
-        Either::Second(Number::new(0.))
-    }
-}
+pub type LengthOrNumber = GenericLengthOrNumber<Length, Number>;
 
 /// A specified value for `min-width`, `min-height`, `width` or `height` property.
 pub type Size = GenericSize<NonNegativeLengthPercentage>;
@@ -1123,3 +1103,6 @@ impl MaxSize {
         Ok(GenericMaxSize::LengthPercentage(length))
     }
 }
+
+/// A specified non-negative `<length>` | `<number>`.
+pub type NonNegativeLengthOrNumber = GenericLengthOrNumber<NonNegativeLength, NonNegativeNumber>;
diff --git a/components/style/values/specified/mod.rs b/components/style/values/specified/mod.rs
index a9582e90307..4956d53f177 100644
--- a/components/style/values/specified/mod.rs
+++ b/components/style/values/specified/mod.rs
@@ -19,9 +19,10 @@ use crate::values::serialize_atom_identifier;
 use crate::values::specified::calc::CalcNode;
 use crate::{Atom, Namespace, Prefix};
 use cssparser::{Parser, Token};
-use num_traits::One;
+use num_traits::{One, Zero};
 use std::f32;
 use std::fmt::{self, Write};
+use std::ops::Add;
 use style_traits::values::specified::AllowedNumericType;
 use style_traits::{CssWriter, ParseError, SpecifiedValueInfo, StyleParseErrorKind, ToCss};
 
@@ -39,8 +40,9 @@ pub use self::box_::{AnimationIterationCount, AnimationName, Contain, Display};
 pub use self::box_::{Appearance, BreakBetween, BreakWithin};
 pub use self::box_::{Clear, Float, Overflow, OverflowAnchor};
 pub use self::box_::{OverflowClipBox, OverscrollBehavior, Perspective, Resize};
-pub use self::box_::{ScrollSnapType, TouchAction, TransitionProperty, VerticalAlign, WillChange};
-pub use self::color::{Color, ColorPropertyValue, RGBAColor};
+pub use self::box_::{ScrollSnapAlign, ScrollSnapType};
+pub use self::box_::{TouchAction, TransitionProperty, VerticalAlign, WillChange};
+pub use self::color::{Color, ColorOrAuto, ColorPropertyValue, RGBAColor};
 pub use self::column::ColumnCount;
 pub use self::counters::{Content, ContentItem, CounterIncrement, CounterReset};
 pub use self::easing::TimingFunction;
@@ -57,7 +59,7 @@ pub use self::gecko::ScrollSnapPoint;
 pub use self::image::{ColorStop, EndingShape as GradientEndingShape, Gradient};
 pub use self::image::{GradientItem, GradientKind, Image, ImageLayer, MozImageRect};
 pub use self::length::{AbsoluteLength, CalcLengthPercentage, CharacterWidth};
-pub use self::length::{FontRelativeLength, Length, LengthOrNumber};
+pub use self::length::{FontRelativeLength, Length, LengthOrNumber, NonNegativeLengthOrNumber};
 pub use self::length::{LengthPercentage, LengthPercentageOrAuto};
 pub use self::length::{MaxSize, Size};
 pub use self::length::{NoCalcLength, ViewportPercentageLength};
@@ -70,14 +72,14 @@ pub use self::outline::OutlineStyle;
 pub use self::percentage::Percentage;
 pub use self::position::{GridAutoFlow, GridTemplateAreas, Position};
 pub use self::position::{PositionComponent, ZIndex};
-pub use self::rect::LengthOrNumberRect;
+pub use self::rect::NonNegativeLengthOrNumberRect;
 pub use self::resolution::Resolution;
 pub use self::svg::MozContextProperties;
 pub use self::svg::{SVGLength, SVGOpacity, SVGPaint, SVGPaintKind};
 pub use self::svg::{SVGPaintOrder, SVGStrokeDashArray, SVGWidth};
 pub use self::svg_path::SVGPathData;
 pub use self::table::XSpan;
-pub use self::text::{InitialLetter, LetterSpacing, LineHeight, MozTabSize, TextAlign};
+pub use self::text::{InitialLetter, LetterSpacing, LineHeight, TextAlign};
 pub use self::text::{OverflowWrap, TextEmphasisPosition, TextEmphasisStyle};
 pub use self::text::{TextAlignKeyword, TextDecorationLine, TextOverflow, WordSpacing};
 pub use self::time::Time;
@@ -85,7 +87,7 @@ pub use self::transform::{Rotate, Scale, Transform};
 pub use self::transform::{TransformOrigin, TransformStyle, Translate};
 #[cfg(feature = "gecko")]
 pub use self::ui::CursorImage;
-pub use self::ui::{ColorOrAuto, Cursor, MozForceBrokenImageIcon, UserSelect};
+pub use self::ui::{Cursor, MozForceBrokenImageIcon, UserSelect};
 pub use super::generics::grid::GridTemplateComponent as GenericGridTemplateComponent;
 
 #[cfg(feature = "gecko")]
@@ -270,6 +272,26 @@ impl IsParallelTo for (Number, Number, Number) {
 
 impl SpecifiedValueInfo for Number {}
 
+impl Add for Number {
+    type Output = Self;
+
+    fn add(self, other: Self) -> Self {
+        Self::new(self.get() + other.get())
+    }
+}
+
+impl Zero for Number {
+    #[inline]
+    fn zero() -> Self {
+        Self::new(0.)
+    }
+
+    #[inline]
+    fn is_zero(&self) -> bool {
+        self.get() == 0.
+    }
+}
+
 impl From<Number> for f32 {
     #[inline]
     fn from(n: Number) -> Self {
@@ -563,7 +585,7 @@ impl Parse for PositiveInteger {
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
     ) -> Result<Self, ParseError<'i>> {
-        Integer::parse_positive(context, input).map(GreaterThanOrEqualToOne::<Integer>)
+        Integer::parse_positive(context, input).map(GreaterThanOrEqualToOne)
     }
 }
 
diff --git a/components/style/values/specified/position.rs b/components/style/values/specified/position.rs
index b9006ee799b..0212763ec6d 100644
--- a/components/style/values/specified/position.rs
+++ b/components/style/values/specified/position.rs
@@ -731,15 +731,3 @@ impl GridTemplateAreas {
 
 /// A specified value for the `z-index` property.
 pub type ZIndex = GenericZIndex<Integer>;
-
-impl Parse for ZIndex {
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        if input.try(|i| i.expect_ident_matching("auto")).is_ok() {
-            return Ok(GenericZIndex::Auto);
-        }
-        Ok(GenericZIndex::Integer(Integer::parse(context, input)?))
-    }
-}
diff --git a/components/style/values/specified/rect.rs b/components/style/values/specified/rect.rs
index d86a382c7e9..7955ecaa48d 100644
--- a/components/style/values/specified/rect.rs
+++ b/components/style/values/specified/rect.rs
@@ -4,22 +4,8 @@
 
 //! Specified types for CSS borders.
 
-use crate::parser::ParserContext;
 use crate::values::generics::rect::Rect;
-use crate::values::specified::length::LengthOrNumber;
-use cssparser::Parser;
-use style_traits::ParseError;
+use crate::values::specified::length::NonNegativeLengthOrNumber;
 
 /// A specified rectangle made of four `<length-or-number>` values.
-pub type LengthOrNumberRect = Rect<LengthOrNumber>;
-
-impl LengthOrNumberRect {
-    /// Parses a `LengthOrNumberRect`, rejecting negative values.
-    #[inline]
-    pub fn parse_non_negative<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        Rect::parse_with(context, input, LengthOrNumber::parse_non_negative)
-    }
-}
+pub type NonNegativeLengthOrNumberRect = Rect<NonNegativeLengthOrNumber>;
diff --git a/components/style/values/specified/svg.rs b/components/style/values/specified/svg.rs
index 9e9c435ab9d..98db273e61c 100644
--- a/components/style/values/specified/svg.rs
+++ b/components/style/values/specified/svg.rs
@@ -23,31 +23,6 @@ pub type SVGPaint = generic::SVGPaint<Color, SpecifiedUrl>;
 /// Specified SVG Paint Kind value
 pub type SVGPaintKind = generic::SVGPaintKind<Color, SpecifiedUrl>;
 
-#[cfg(feature = "gecko")]
-fn is_context_value_enabled() -> bool {
-    // The prefs can only be mutated on the main thread, so it is safe
-    // to read whenever we are on the main thread or the main thread is
-    // blocked.
-    use crate::gecko_bindings::structs::mozilla;
-    unsafe { mozilla::StaticPrefs_sVarCache_gfx_font_rendering_opentype_svg_enabled }
-}
-#[cfg(not(feature = "gecko"))]
-fn is_context_value_enabled() -> bool {
-    false
-}
-
-fn parse_context_value<'i, 't, T>(
-    input: &mut Parser<'i, 't>,
-    value: T,
-) -> Result<T, ParseError<'i>> {
-    if !is_context_value_enabled() {
-        return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
-    }
-
-    input.expect_ident_matching("context-value")?;
-    Ok(value)
-}
-
 /// A value of <length> | <percentage> | <number> for stroke-dashoffset.
 /// <https://www.w3.org/TR/SVG11/painting.html#StrokeProperties>
 pub type SvgLengthPercentageOrNumber =
@@ -56,18 +31,6 @@ pub type SvgLengthPercentageOrNumber =
 /// <length> | <percentage> | <number> | context-value
 pub type SVGLength = generic::SVGLength<SvgLengthPercentageOrNumber>;
 
-impl Parse for SVGLength {
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        input
-            .try(|i| SvgLengthPercentageOrNumber::parse(context, i))
-            .map(Into::into)
-            .or_else(|_| parse_context_value(input, generic::SVGLength::ContextValue))
-    }
-}
-
 impl From<SvgLengthPercentageOrNumber> for SVGLength {
     fn from(length: SvgLengthPercentageOrNumber) -> Self {
         generic::SVGLength::Length(length)
@@ -82,18 +45,6 @@ pub type NonNegativeSvgLengthPercentageOrNumber =
 /// A non-negative version of SVGLength.
 pub type SVGWidth = generic::SVGLength<NonNegativeSvgLengthPercentageOrNumber>;
 
-impl Parse for SVGWidth {
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        input
-            .try(|i| NonNegativeSvgLengthPercentageOrNumber::parse(context, i))
-            .map(Into::into)
-            .or_else(|_| parse_context_value(input, generic::SVGLength::ContextValue))
-    }
-}
-
 impl From<NonNegativeSvgLengthPercentageOrNumber> for SVGWidth {
     fn from(length: NonNegativeSvgLengthPercentageOrNumber) -> Self {
         generic::SVGLength::Length(length)
@@ -113,34 +64,21 @@ impl Parse for SVGStrokeDashArray {
                 NonNegativeSvgLengthPercentageOrNumber::parse(context, i)
             })
         }) {
-            Ok(generic::SVGStrokeDashArray::Values(values))
-        } else if let Ok(_) = input.try(|i| i.expect_ident_matching("none")) {
-            Ok(generic::SVGStrokeDashArray::Values(vec![]))
-        } else {
-            parse_context_value(input, generic::SVGStrokeDashArray::ContextValue)
-        }
-    }
-}
-
-/// <opacity-value> | context-fill-opacity | context-stroke-opacity
-pub type SVGOpacity = generic::SVGOpacity<Opacity>;
-
-impl Parse for SVGOpacity {
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        if let Ok(opacity) = input.try(|i| Opacity::parse(context, i)) {
-            return Ok(generic::SVGOpacity::Opacity(opacity));
+            return Ok(generic::SVGStrokeDashArray::Values(values));
         }
 
         try_match_ident_ignore_ascii_case! { input,
-            "context-fill-opacity" => Ok(generic::SVGOpacity::ContextFillOpacity),
-            "context-stroke-opacity" => Ok(generic::SVGOpacity::ContextStrokeOpacity),
+            "context-value" if generic::is_context_value_enabled(context) => {
+                Ok(generic::SVGStrokeDashArray::ContextValue)
+            },
+            "none" => Ok(generic::SVGStrokeDashArray::Values(vec![])),
         }
     }
 }
 
+/// <opacity-value> | context-fill-opacity | context-stroke-opacity
+pub type SVGOpacity = generic::SVGOpacity<Opacity>;
+
 /// The specified value for a single CSS paint-order property.
 #[repr(u8)]
 #[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd, ToCss)]
diff --git a/components/style/values/specified/text.rs b/components/style/values/specified/text.rs
index d395132f5b1..1879dc4159a 100644
--- a/components/style/values/specified/text.rs
+++ b/components/style/values/specified/text.rs
@@ -13,11 +13,10 @@ use crate::values::computed::text::TextOverflow as ComputedTextOverflow;
 use crate::values::computed::{Context, ToComputedValue};
 use crate::values::generics::text::InitialLetter as GenericInitialLetter;
 use crate::values::generics::text::LineHeight as GenericLineHeight;
-use crate::values::generics::text::MozTabSize as GenericMozTabSize;
 use crate::values::generics::text::Spacing;
+use crate::values::specified::length::NonNegativeLengthPercentage;
 use crate::values::specified::length::{FontRelativeLength, Length};
 use crate::values::specified::length::{LengthPercentage, NoCalcLength};
-use crate::values::specified::length::{NonNegativeLength, NonNegativeLengthPercentage};
 use crate::values::specified::{AllowQuirks, Integer, NonNegativeNumber, Number};
 use cssparser::{Parser, Token};
 use selectors::parser::SelectorParseErrorKind;
@@ -420,7 +419,7 @@ pub enum TextAlignKeyword {
 
 /// Specified value of text-align property.
 #[cfg_attr(feature = "gecko", derive(MallocSizeOf))]
-#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq, SpecifiedValueInfo, ToCss)]
+#[derive(Clone, Copy, Debug, Eq, Hash, Parse, PartialEq, SpecifiedValueInfo, ToCss)]
 pub enum TextAlign {
     /// Keyword value of text-align property.
     Keyword(TextAlignKeyword),
@@ -436,27 +435,6 @@ pub enum TextAlign {
     MozCenterOrInherit,
 }
 
-impl Parse for TextAlign {
-    fn parse<'i, 't>(
-        _context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        // MozCenterOrInherit cannot be parsed, only set directly on the elements
-        if let Ok(key) = input.try(TextAlignKeyword::parse) {
-            return Ok(TextAlign::Keyword(key));
-        }
-        #[cfg(feature = "gecko")]
-        {
-            input.expect_ident_matching("match-parent")?;
-            return Ok(TextAlign::MatchParent);
-        }
-        #[cfg(feature = "servo")]
-        {
-            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
-        }
-    }
-}
-
 impl TextAlign {
     /// Convert an enumerated value coming from Gecko to a `TextAlign`.
     #[cfg(feature = "gecko")]
@@ -835,25 +813,6 @@ impl From<TextEmphasisPosition> for u8 {
     }
 }
 
-/// A specified value for the `-moz-tab-size` property.
-pub type MozTabSize = GenericMozTabSize<NonNegativeNumber, NonNegativeLength>;
-
-impl Parse for MozTabSize {
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        if let Ok(number) = input.try(|i| NonNegativeNumber::parse(context, i)) {
-            // Numbers need to be parsed first because `0` must be recognised
-            // as the number `0` and not the length `0px`.
-            return Ok(GenericMozTabSize::Number(number));
-        }
-        Ok(GenericMozTabSize::Length(NonNegativeLength::parse(
-            context, input,
-        )?))
-    }
-}
-
 /// Values for the `overflow-wrap` property.
 #[repr(u8)]
 #[derive(
diff --git a/components/style/values/specified/transform.rs b/components/style/values/specified/transform.rs
index 859cbd80e2a..c4f43735498 100644
--- a/components/style/values/specified/transform.rs
+++ b/components/style/values/specified/transform.rs
@@ -231,7 +231,7 @@ impl Parse for Transform {
 }
 
 /// The specified value of a component of a CSS `<transform-origin>`.
-#[derive(Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss)]
+#[derive(Clone, Debug, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss)]
 pub enum OriginComponent<S> {
     /// `center`
     Center,
@@ -295,25 +295,6 @@ impl Parse for TransformOrigin {
     }
 }
 
-impl<S> Parse for OriginComponent<S>
-where
-    S: Parse,
-{
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        if input.try(|i| i.expect_ident_matching("center")).is_ok() {
-            return Ok(OriginComponent::Center);
-        }
-        if let Ok(lp) = input.try(|i| LengthPercentage::parse(context, i)) {
-            return Ok(OriginComponent::Length(lp));
-        }
-        let keyword = S::parse(context, input)?;
-        Ok(OriginComponent::Side(keyword))
-    }
-}
-
 impl<S> ToComputedValue for OriginComponent<S>
 where
     S: Side,
diff --git a/components/style/values/specified/ui.rs b/components/style/values/specified/ui.rs
index 2290ac06d6d..0ccca5d359e 100644
--- a/components/style/values/specified/ui.rs
+++ b/components/style/values/specified/ui.rs
@@ -9,14 +9,10 @@ use crate::values::generics::ui as generics;
 use crate::values::specified::color::Color;
 use crate::values::specified::url::SpecifiedImageUrl;
 use crate::values::specified::Number;
-use crate::values::{Auto, Either};
 use cssparser::Parser;
 use std::fmt::{self, Write};
 use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss};
 
-/// auto | <color>
-pub type ColorOrAuto = Either<Color, Auto>;
-
 /// A specified value for the `cursor` property.
 pub type Cursor = generics::Cursor<CursorImage>;
 
diff --git a/components/style_derive/parse.rs b/components/style_derive/parse.rs
index 0f68f1df5ff..b9b7ae37e1c 100644
--- a/components/style_derive/parse.rs
+++ b/components/style_derive/parse.rs
@@ -5,8 +5,8 @@
 use crate::cg;
 use crate::to_css::CssVariantAttrs;
 use proc_macro2::TokenStream;
-use syn::{DeriveInput, Path};
-use synstructure;
+use syn::{self, DeriveInput, Path};
+use synstructure::{Structure, VariantInfo};
 
 #[darling(attributes(parse), default)]
 #[derive(Default, FromVariant)]
@@ -15,22 +15,90 @@ pub struct ParseVariantAttrs {
     pub condition: Option<Path>,
 }
 
-pub fn derive(input: DeriveInput) -> TokenStream {
+fn parse_non_keyword_variant(
+    name: &syn::Ident,
+    variant: &VariantInfo,
+    variant_attrs: &CssVariantAttrs,
+    parse_attrs: &ParseVariantAttrs,
+    skip_try: bool,
+) -> TokenStream {
+    let bindings = variant.bindings();
+    assert!(parse_attrs.aliases.is_none());
+    assert!(variant_attrs.function.is_none());
+    assert!(variant_attrs.keyword.is_none());
+    assert_eq!(
+        bindings.len(),
+        1,
+        "We only support deriving parse for simple variants"
+    );
+    let variant_name = &variant.ast().ident;
+    let ty = &bindings[0].ast().ty;
+    let mut parse = if skip_try {
+        quote! {
+            let v = <#ty as crate::parser::Parse>::parse(context, input)?;
+            return Ok(#name::#variant_name(v));
+        }
+    } else {
+        quote! {
+            if let Ok(v) = input.try(|i| <#ty as crate::parser::Parse>::parse(context, i)) {
+                return Ok(#name::#variant_name(v));
+            }
+        }
+    };
+
+    if let Some(ref condition) = parse_attrs.condition {
+        parse = quote! {
+            if #condition(context) {
+                #parse
+            }
+        };
+
+        if skip_try {
+            // We're the last variant and we can fail to parse due to the
+            // condition clause. If that happens, we need to return an error.
+            parse = quote! {
+                #parse
+                Err(input.new_custom_error(style_traits::StyleParseErrorKind::UnspecifiedError))
+            };
+        }
+    }
+
+    parse
+}
+
+pub fn derive(mut input: DeriveInput) -> TokenStream {
+    {
+        let mut where_clause = input.generics.where_clause.take();
+        for param in input.generics.type_params() {
+            cg::add_predicate(
+                &mut where_clause,
+                parse_quote!(#param: crate::parser::Parse),
+            );
+        }
+        input.generics.where_clause = where_clause;
+    }
+
     let name = &input.ident;
-    let s = synstructure::Structure::new(&input);
+    let s = Structure::new(&input);
 
     let mut saw_condition = false;
-    let match_body = s.variants().iter().fold(quote!(), |match_body, variant| {
-        let bindings = variant.bindings();
-        assert!(
-            bindings.is_empty(),
-            "Parse is only supported for single-variant enums for now"
-        );
+    let mut match_keywords = quote! {};
+    let mut non_keywords = vec![];
 
+    let mut effective_variants = 0;
+    for variant in s.variants().iter() {
         let css_variant_attrs = cg::parse_variant_attrs_from_ast::<CssVariantAttrs>(&variant.ast());
         let parse_attrs = cg::parse_variant_attrs_from_ast::<ParseVariantAttrs>(&variant.ast());
         if css_variant_attrs.skip {
-            return match_body;
+            continue;
+        }
+        effective_variants += 1;
+
+        saw_condition |= parse_attrs.condition.is_some();
+
+        if !variant.bindings().is_empty() {
+            non_keywords.push((variant, css_variant_attrs, parse_attrs));
+            continue;
         }
 
         let identifier = cg::to_css_identifier(
@@ -40,55 +108,73 @@ pub fn derive(input: DeriveInput) -> TokenStream {
         );
         let ident = &variant.ast().ident;
 
-        saw_condition |= parse_attrs.condition.is_some();
         let condition = match parse_attrs.condition {
             Some(ref p) => quote! { if #p(context) },
             None => quote! {},
         };
 
-        let mut body = quote! {
-            #match_body
+        match_keywords.extend(quote! {
             #identifier #condition => Ok(#name::#ident),
-        };
+        });
 
         let aliases = match parse_attrs.aliases {
             Some(aliases) => aliases,
-            None => return body,
+            None => continue,
         };
 
         for alias in aliases.split(',') {
-            body = quote! {
-                #body
+            match_keywords.extend(quote! {
                 #alias #condition => Ok(#name::#ident),
-            };
+            });
         }
+    }
 
-        body
-    });
+    let needs_context = saw_condition || !non_keywords.is_empty();
 
-    let context_ident = if saw_condition {
+    let context_ident = if needs_context {
         quote! { context }
     } else {
         quote! { _ }
     };
 
-    let parse_body = if saw_condition {
-        quote! {
-            let location = input.current_source_location();
-            let ident = input.expect_ident()?;
-            match_ignore_ascii_case! { &ident,
-                #match_body
-                _ => Err(location.new_unexpected_token_error(
-                    cssparser::Token::Ident(ident.clone())
-                ))
+    let has_keywords = non_keywords.len() != effective_variants;
+
+    let mut parse_non_keywords = quote! {};
+    for (i, (variant, css_attrs, parse_attrs)) in non_keywords.iter().enumerate() {
+        let skip_try = !has_keywords && i == non_keywords.len() - 1;
+        let parse_variant =
+            parse_non_keyword_variant(name, variant, css_attrs, parse_attrs, skip_try);
+        parse_non_keywords.extend(parse_variant);
+    }
+
+    let parse_body = if needs_context {
+        let parse_keywords = if has_keywords {
+            quote! {
+                let location = input.current_source_location();
+                let ident = input.expect_ident()?;
+                match_ignore_ascii_case! { &ident,
+                    #match_keywords
+                    _ => Err(location.new_unexpected_token_error(
+                        cssparser::Token::Ident(ident.clone())
+                    ))
+                }
             }
+        } else {
+            quote! {}
+        };
+
+        quote! {
+            #parse_non_keywords
+            #parse_keywords
         }
     } else {
         quote! { Self::parse(input) }
     };
 
+    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+
     let parse_trait_impl = quote! {
-        impl crate::parser::Parse for #name {
+        impl #impl_generics crate::parser::Parse for #name #ty_generics #where_clause {
             #[inline]
             fn parse<'i, 't>(
                 #context_ident: &crate::parser::ParserContext,
@@ -99,10 +185,12 @@ pub fn derive(input: DeriveInput) -> TokenStream {
         }
     };
 
-    if saw_condition {
+    if needs_context {
         return parse_trait_impl;
     }
 
+    assert!(non_keywords.is_empty());
+
     // TODO(emilio): It'd be nice to get rid of these, but that makes the
     // conversion harder...
     let methods_impl = quote! {
@@ -125,7 +213,7 @@ pub fn derive(input: DeriveInput) -> TokenStream {
             #[inline]
             pub fn from_ident(ident: &str) -> Result<Self, ()> {
                 match_ignore_ascii_case! { ident,
-                    #match_body
+                    #match_keywords
                     _ => Err(()),
                 }
             }