style: Support ray() in offset-path and make it animatable.

1. Add `generics::motion::OffsetPath`, and use specified `Angle` and
   computed `Angle` to define specified `OffsetPath` and computed `OffsetPath`.
2. Add `ray` function into `OffsetPath`.

We also tweak the degree from 150deg to 135deg in wpt (e.g.
offset-path-ray-001.html and others) to avoid floating point precision issues.
For example:
```
// offset-path: ray(150deg ...);
// offset-distance: 20px;
matrix:
{
  {0.500000 0.866025 0.000000 0.000000},
  {-0.866025 0.500000 0.000000 0.000000},
  {0.000000 0.000000 1.000000 0.000000},
  {10.000000 17.320509 0.000000 1.000000}
}

// rotate(60deg) translate(20px)
matrix:
{
  {0.500000 0.866025 0.000000 0.000000},
  {-0.866025 0.500000 0.000000 0.000000},
  {0.000000 0.000000 1.000000 0.000000},
  {10.000000 17.320507 0.000000 1.000000}
}
```
Their translate parts, 17.320509 vs 17.320507, are almost the same (only
tiny difference), which may cause the reftest failed.

Differential Revision: https://phabricator.services.mozilla.com/D42721

components/style/gecko/conversions.rs

@@ -42,7 +42,7 @@ impl nsStyleImage {
                         image_rect.left,
                     );
                 }
-            },
+            }
             GenericImage::Element(ref element) => unsafe {
                 bindings::Gecko_SetImageElement(self, element.as_ptr());
             },
@@ -76,16 +76,16 @@ impl nsStyleImage {
                         left: rect.3,
                     })))
                 }
-            },
+            }
             nsStyleImageType::eStyleImageType_Gradient => {
                 let gradient: &Gradient = &**self.__bindgen_anon_1.mGradient.as_ref();
                 Some(GenericImage::Gradient(Box::new(gradient.clone())))
-            },
+            }
             nsStyleImageType::eStyleImageType_Element => {
                 use crate::gecko_string_cache::Atom;
                 let atom = bindings::Gecko_GetImageElement(self);
                 Some(GenericImage::Element(Atom::from_raw(atom)))
-            },
+            }
         }
     }
 
@@ -128,13 +128,13 @@ pub mod basic_shape {
                         Some(self.mReferenceBox.into())
                     };
                     Some(ShapeSource::Shape(shape, reference_box))
-                },
+                }
                 StyleShapeSourceType::Image => None,
                 StyleShapeSourceType::Path => {
                     let path = self.to_svg_path().expect("expect an SVGPathData");
                     let fill = unsafe { &*self.__bindgen_anon_1.mSVGPath.as_ref().mPtr }.mFillRule;
                     Some(ShapeSource::Path(Path { fill, path }))
-                },
+                }
             }
         }
 
@@ -144,7 +144,7 @@ pub mod basic_shape {
                 StyleShapeSourceType::Path => {
                     let gecko_path = unsafe { &*self.__bindgen_anon_1.mSVGPath.as_ref().mPtr };
                     Some(SVGPathData(gecko_path.mPath.clone()))
-                },
+                }
                 _ => None,
             }
         }
@@ -187,14 +187,15 @@ pub mod basic_shape {
 
     impl<'a> From<&'a StyleShapeSource> for OffsetPath {
         fn from(other: &'a StyleShapeSource) -> Self {
+            use crate::values::generics::motion::GenericOffsetPath;
             match other.mType {
-                StyleShapeSourceType::Path => {
-                    OffsetPath::Path(other.to_svg_path().expect("Cannot convert to SVGPathData"))
-                },
+                StyleShapeSourceType::Path => GenericOffsetPath::Path(
+                    other.to_svg_path().expect("Cannot convert to SVGPathData"),
+                ),
                 StyleShapeSourceType::None => OffsetPath::none(),
-                StyleShapeSourceType::Shape |
-                StyleShapeSourceType::Box |
-                StyleShapeSourceType::Image => unreachable!("Unsupported offset-path type"),
+                StyleShapeSourceType::Shape
+                | StyleShapeSourceType::Box
+                | StyleShapeSourceType::Image => unreachable!("Unsupported offset-path type"),
             }
         }
     }

components/style/values/computed/motion.rs

@@ -5,12 +5,11 @@
 //! Computed types for CSS values that are related to motion path.
 
 use crate::values::computed::Angle;
+use crate::values::generics::motion::GenericOffsetPath;
 use crate::Zero;
 
-/// A computed offset-path. The computed value is as specified value.
-///
-/// https://drafts.fxtf.org/motion-1/#offset-path-property
-pub use crate::values::specified::motion::OffsetPath;
+/// The computed value of `offset-path`.
+pub type OffsetPath = GenericOffsetPath<Angle>;
 
 #[inline]
 fn is_auto_zero_angle(auto: &bool, angle: &Angle) -> bool {

components/style/values/generics/mod.rs

@@ -29,6 +29,7 @@ pub mod font;
 pub mod grid;
 pub mod image;
 pub mod length;
+pub mod motion;
 pub mod position;
 pub mod rect;
 pub mod size;

components/style/values/generics/motion.rs

@@ -0,0 +1,110 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for CSS Motion Path.
+
+use crate::values::specified::SVGPathData;
+
+/// The <size> in ray() function.
+///
+/// https://drafts.fxtf.org/motion-1/#valdef-offsetpath-size
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum RaySize {
+    ClosestSide,
+    ClosestCorner,
+    FarthestSide,
+    FarthestCorner,
+    Sides,
+}
+
+/// The `ray()` function, `ray( [ <angle> && <size> && contain? ] )`
+///
+/// https://drafts.fxtf.org/motion-1/#valdef-offsetpath-ray
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct RayFunction<Angle> {
+    /// 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)]
+    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 offset-path value.
+///
+/// https://drafts.fxtf.org/motion-1/#offset-path-property
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericOffsetPath<Angle> {
+    // 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.
+    #[css(function)]
+    Ray(RayFunction<Angle>),
+    /// None value.
+    #[animation(error)]
+    None,
+    // Bug 1186329: Implement <basic-shape>, <geometry-box>, and <url>.
+}
+
+pub use self::GenericOffsetPath as OffsetPath;
+
+impl<Angle> OffsetPath<Angle> {
+    /// Return None.
+    #[inline]
+    pub fn none() -> Self {
+        OffsetPath::None
+    }
+}

components/style/values/specified/motion.rs

@@ -7,46 +7,53 @@
 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, RayFunction, RaySize};
 use crate::values::specified::{Angle, SVGPathData};
 use crate::Zero;
 use cssparser::Parser;
 use style_traits::{ParseError, StyleParseErrorKind};
 
-/// The offset-path value.
-///
-/// https://drafts.fxtf.org/motion-1/#offset-path-property
-#[derive(
-    Animate,
-    Clone,
-    ComputeSquaredDistance,
-    Debug,
-    MallocSizeOf,
-    PartialEq,
-    SpecifiedValueInfo,
-    ToAnimatedZero,
-    ToComputedValue,
-    ToCss,
-    ToResolvedValue,
-    ToShmem,
-)]
-#[repr(C, u8)]
-pub enum OffsetPath {
-    // 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),
-    /// None value.
-    #[animation(error)]
-    None,
-    // Bug 1186329: Implement ray(), <basic-shape>, <geometry-box>, and <url>.
-}
+/// The specified value of `offset-path`.
+pub type OffsetPath = GenericOffsetPath<Angle>;
 
-impl OffsetPath {
-    /// Return None.
-    #[inline]
-    pub fn none() -> Self {
-        OffsetPath::None
+impl Parse for RayFunction<Angle> {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut angle = None;
+        let mut size = None;
+        let mut contain = false;
+        loop {
+            if angle.is_none() {
+                angle = input.try(|i| Angle::parse(context, i)).ok();
+            }
+
+            if size.is_none() {
+                size = input.try(RaySize::parse).ok();
+                if size.is_some() {
+                    continue;
+                }
+            }
+
+            if !contain {
+                contain = input.try(|i| i.expect_ident_matching("contain")).is_ok();
+                if contain {
+                    continue;
+                }
+            }
+            break;
+        }
+
+        if angle.is_none() || size.is_none() {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        Ok(RayFunction {
+            angle: angle.unwrap(),
+            size: size.unwrap(),
+            contain,
+        })
     }
 }
 
@@ -65,9 +72,10 @@ impl Parse for OffsetPath {
         let function = input.expect_function()?.clone();
         input.parse_nested_block(move |i| {
             match_ignore_ascii_case! { &function,
-                // Bug 1186329: Implement the parser for ray(), <basic-shape>, <geometry-box>,
+                // Bug 1186329: Implement the parser for <basic-shape>, <geometry-box>,
                 // and <url>.
-                "path" => SVGPathData::parse(context, i).map(OffsetPath::Path),
+                "path" => SVGPathData::parse(context, i).map(GenericOffsetPath::Path),
+                "ray" => RayFunction::parse(context, i).map(GenericOffsetPath::Ray),
                 _ => {
                     Err(location.new_custom_error(
                         StyleParseErrorKind::UnexpectedFunction(function.clone())