style: Add at <position> into ray() in style system

We reuse PositionOrAuto here, and let "auto" represent the situation when the
author omits "at <position>" because it has a special meaning.

https://drafts.fxtf.org/motion-1/#valdef-ray-at-position

Note: No need to update css/motion/parsing/offset-path-parsing-valid.html
because Blink added some to the upstream repo already.

Differential Revision: https://phabricator.services.mozilla.com/D179860

components/style/values/computed/motion.rs

@@ -4,12 +4,17 @@
 
 //! Computed types for CSS values that are related to motion path.
 
-use crate::values::computed::{Angle, LengthPercentage};
-use crate::values::generics::motion::{GenericOffsetPath, GenericOffsetPosition};
+use crate::values::computed::{Angle, LengthPercentage, Position};
+use crate::values::generics::motion::{
+    GenericOffsetPath, GenericOffsetPosition, GenericRayFunction,
+};
 use crate::Zero;
 
+/// The computed value of ray() function.
+pub type RayFunction = GenericRayFunction<Angle, Position>;
+
 /// The computed value of `offset-path`.
-pub type OffsetPath = GenericOffsetPath<Angle>;
+pub type OffsetPath = GenericOffsetPath<RayFunction>;
 
 /// The computed value of `offset-position`.
 pub type OffsetPosition = GenericOffsetPosition<LengthPercentage, LengthPercentage>;

components/style/values/generics/motion.rs

@@ -5,15 +5,19 @@
 //! Generic types for CSS Motion Path.
 
 use crate::values::animated::ToAnimatedZero;
-use crate::values::generics::position::GenericPosition;
+use crate::values::generics::position::{GenericPosition, GenericPositionOrAuto};
 use crate::values::specified::SVGPathData;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
 
 /// The <size> in ray() function.
 ///
 /// https://drafts.fxtf.org/motion-1/#valdef-offsetpath-size
 #[allow(missing_docs)]
 #[derive(
+    Animate,
     Clone,
+    ComputeSquaredDistance,
     Copy,
     Debug,
     Deserialize,
@@ -36,15 +40,7 @@ pub enum RaySize {
     Sides,
 }
 
-impl RaySize {
-    /// Returns true if it is the default value.
-    #[inline]
-    pub fn is_default(&self) -> bool {
-        *self == RaySize::ClosestSide
-    }
-}
-
-/// The `ray()` function, `ray( [ <angle> && <size> && contain? ] )`
+/// The `ray()` function, `ray( [ <angle> && <size> && contain? && [at <position>]? ] )`
 ///
 /// https://drafts.fxtf.org/motion-1/#valdef-offsetpath-ray
 #[derive(
@@ -58,25 +54,54 @@ impl RaySize {
     Serialize,
     SpecifiedValueInfo,
     ToComputedValue,
-    ToCss,
     ToResolvedValue,
     ToShmem,
 )]
 #[repr(C)]
-pub struct RayFunction<Angle> {
+pub struct GenericRayFunction<Angle, Position> {
     /// The bearing angle with `0deg` pointing up and positive angles
     /// representing clockwise rotation.
     pub angle: Angle,
     /// Decide the path length used when `offset-distance` is expressed
     /// as a percentage.
-    #[animation(constant)]
-    #[css(skip_if = "RaySize::is_default")]
     pub size: RaySize,
     /// Clamp `offset-distance` so that the box is entirely contained
     /// within the path.
     #[animation(constant)]
-    #[css(represents_keyword)]
     pub contain: bool,
+    /// The "at <position>" part. If omitted, we use auto to represent it.
+    pub position: GenericPositionOrAuto<Position>,
+}
+
+pub use self::GenericRayFunction as RayFunction;
+
+impl<Angle, Position> ToCss for RayFunction<Angle, Position>
+where
+    Angle: ToCss,
+    Position: ToCss,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.angle.to_css(dest)?;
+
+        if !matches!(self.size, RaySize::ClosestSide) {
+            dest.write_char(' ')?;
+            self.size.to_css(dest)?;
+        }
+
+        if self.contain {
+            dest.write_str(" contain")?;
+        }
+
+        if !matches!(self.position, GenericPositionOrAuto::Auto) {
+            dest.write_str(" at ")?;
+            self.position.to_css(dest)?;
+        }
+
+        Ok(())
+    }
 }
 
 /// The offset-path value.
@@ -98,15 +123,16 @@ pub struct RayFunction<Angle> {
     ToShmem,
 )]
 #[repr(C, u8)]
-pub enum GenericOffsetPath<Angle> {
+pub enum GenericOffsetPath<RayFunction> {
     // We could merge SVGPathData into ShapeSource, so we could reuse them. However,
     // we don't want to support other value for offset-path, so use SVGPathData only for now.
     /// Path value for path(<string>).
     #[css(function)]
     Path(SVGPathData),
     /// ray() function, which defines a path in the polar coordinate system.
+    /// Use Box<> to make sure the size of offset-path is not too large.
     #[css(function)]
-    Ray(RayFunction<Angle>),
+    Ray(Box<RayFunction>),
     /// None value.
     #[animation(error)]
     None,
@@ -115,7 +141,7 @@ pub enum GenericOffsetPath<Angle> {
 
 pub use self::GenericOffsetPath as OffsetPath;
 
-impl<Angle> OffsetPath<Angle> {
+impl<Ray> OffsetPath<Ray> {
     /// Return None.
     #[inline]
     pub fn none() -> Self {
@@ -123,7 +149,7 @@ impl<Angle> OffsetPath<Angle> {
     }
 }
 
-impl<Angle> ToAnimatedZero for OffsetPath<Angle> {
+impl<Ray> ToAnimatedZero for OffsetPath<Ray> {
     #[inline]
     fn to_animated_zero(&self) -> Result<Self, ()> {
         Err(())

components/style/values/generics/position.rs

@@ -101,6 +101,12 @@ impl<Pos> PositionOrAuto<Pos> {
     pub fn auto() -> Self {
         PositionOrAuto::Auto
     }
+
+    /// Return true if it is 'auto'.
+    #[inline]
+    pub fn is_auto(&self) -> bool {
+        matches!(self, PositionOrAuto::Auto)
+    }
 }
 
 /// A generic value for the `z-index` property.

components/style/values/specified/motion.rs

@@ -7,20 +7,21 @@
 use crate::parser::{Parse, ParserContext};
 use crate::values::computed::motion::OffsetRotate as ComputedOffsetRotate;
 use crate::values::computed::{Context, ToComputedValue};
-use crate::values::generics::motion::{
-    GenericOffsetPath, GenericOffsetPosition, RayFunction, RaySize,
-};
+use crate::values::generics::motion as generics;
 use crate::values::specified::position::{HorizontalPosition, VerticalPosition};
-use crate::values::specified::{Angle, SVGPathData};
+use crate::values::specified::{Angle, Position};
 use crate::Zero;
 use cssparser::Parser;
 use style_traits::{ParseError, StyleParseErrorKind};
 
+/// The specified value of ray() function.
+pub type RayFunction = generics::GenericRayFunction<Angle, Position>;
+
 /// The specified value of `offset-path`.
-pub type OffsetPath = GenericOffsetPath<Angle>;
+pub type OffsetPath = generics::GenericOffsetPath<RayFunction>;
 
 /// The specified value of `offset-position`.
-pub type OffsetPosition = GenericOffsetPosition<HorizontalPosition, VerticalPosition>;
+pub type OffsetPosition = generics::GenericOffsetPosition<HorizontalPosition, VerticalPosition>;
 
 #[cfg(feature = "gecko")]
 fn is_ray_enabled() -> bool {
@@ -31,11 +32,13 @@ fn is_ray_enabled() -> bool {
     false
 }
 
-impl Parse for RayFunction<Angle> {
+impl Parse for RayFunction {
     fn parse<'i, 't>(
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
     ) -> Result<Self, ParseError<'i>> {
+        use crate::values::specified::PositionOrAuto;
+
         if !is_ray_enabled() {
             return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
         }
@@ -43,13 +46,14 @@ impl Parse for RayFunction<Angle> {
         let mut angle = None;
         let mut size = None;
         let mut contain = false;
+        let mut position = None;
         loop {
             if angle.is_none() {
                 angle = input.try_parse(|i| Angle::parse(context, i)).ok();
             }
 
             if size.is_none() {
-                size = input.try_parse(RaySize::parse).ok();
+                size = input.try_parse(generics::RaySize::parse).ok();
                 if size.is_some() {
                     continue;
                 }
@@ -63,6 +67,17 @@ impl Parse for RayFunction<Angle> {
                     continue;
                 }
             }
+
+            if position.is_none() {
+                if input.try_parse(|i| i.expect_ident_matching("at")).is_ok() {
+                    let pos = Position::parse(context, input)?;
+                    position = Some(PositionOrAuto::Position(pos));
+                }
+
+                if position.is_some() {
+                    continue;
+                }
+            }
             break;
         }
 
@@ -73,8 +88,9 @@ impl Parse for RayFunction<Angle> {
         Ok(RayFunction {
             angle: angle.unwrap(),
             // If no <ray-size> is specified it defaults to closest-side.
-            size: size.unwrap_or(RaySize::ClosestSide),
+            size: size.unwrap_or(generics::RaySize::ClosestSide),
             contain,
+            position: position.unwrap_or(PositionOrAuto::auto()),
         })
     }
 }
@@ -84,7 +100,7 @@ impl Parse for OffsetPath {
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
     ) -> Result<Self, ParseError<'i>> {
-        use crate::values::specified::svg_path::AllowEmpty;
+        use crate::values::specified::svg_path::{AllowEmpty, SVGPathData};
 
         // Parse none.
         if input.try_parse(|i| i.expect_ident_matching("none")).is_ok() {
@@ -99,7 +115,7 @@ impl Parse for OffsetPath {
                 // Bug 1186329: Implement the parser for <basic-shape>, <geometry-box>,
                 // and <url>.
                 "path" => SVGPathData::parse(i, AllowEmpty::No).map(OffsetPath::Path),
-                "ray" => RayFunction::parse(context, i).map(OffsetPath::Ray),
+                "ray" => RayFunction::parse(context, i).map(|v| OffsetPath::Ray(Box::new(v))),
                 _ => {
                     Err(location.new_custom_error(
                         StyleParseErrorKind::UnexpectedFunction(function.clone())