style: Support scroll-timeline-name longhand in style system

Implement "scroll-timeline-name: none | <custom-ident>".

Differential Revision: https://phabricator.services.mozilla.com/D146018

components/style/properties/longhands/ui.mako.rs

@@ -304,3 +304,14 @@ ${helpers.predefined_type(
     spec="https://drafts.csswg.org/css-animations-2/#propdef-animation-timeline",
     rule_types_allowed=DEFAULT_RULES_EXCEPT_KEYFRAME,
 )}
+
+${helpers.predefined_type(
+    "scroll-timeline-name",
+    "ScrollTimelineName",
+    "computed::ScrollTimelineName::none()",
+    engines="gecko",
+    animation_value_type="none",
+    gecko_pref="layout.css.scroll-linked-animations.enabled",
+    spec="https://github.com/w3c/csswg-drafts/issues/6674",
+    rule_types_allowed=DEFAULT_RULES_EXCEPT_KEYFRAME,
+)}

components/style/values/computed/box.rs

@@ -14,10 +14,9 @@ use crate::values::specified::box_ as specified;
 pub use crate::values::specified::box_::{
     AnimationName, AnimationTimeline, Appearance, BreakBetween, BreakWithin,
     Clear as SpecifiedClear, Contain, ContainerName, ContainerType, ContentVisibility, Display,
-    Float as SpecifiedFloat, Overflow, OverflowAnchor, OverflowClipBox,
-    OverscrollBehavior, ScrollSnapAlign, ScrollSnapAxis, ScrollSnapStop,
-    ScrollSnapStrictness, ScrollSnapType, ScrollbarGutter, TouchAction,
-    TransitionProperty, WillChange,
+    Float as SpecifiedFloat, Overflow, OverflowAnchor, OverflowClipBox, OverscrollBehavior,
+    ScrollSnapAlign, ScrollSnapAxis, ScrollSnapStop, ScrollSnapStrictness, ScrollSnapType,
+    ScrollTimelineName, ScrollbarGutter, TouchAction, TransitionProperty, WillChange,
 };
 
 /// A computed value for the `vertical-align` property.

components/style/values/computed/mod.rs

@@ -50,7 +50,7 @@ pub use self::box_::{Appearance, BreakBetween, BreakWithin, Clear, ContentVisibi
 pub use self::box_::{Display, Overflow, OverflowAnchor, TransitionProperty};
 pub use self::box_::{OverflowClipBox, OverscrollBehavior, Perspective, Resize, ScrollbarGutter};
 pub use self::box_::{ScrollSnapAlign, ScrollSnapAxis, ScrollSnapStop};
-pub use self::box_::{ScrollSnapStrictness, ScrollSnapType};
+pub use self::box_::{ScrollSnapStrictness, ScrollSnapType, ScrollTimelineName};
 pub use self::box_::{TouchAction, VerticalAlign, WillChange};
 pub use self::color::{Color, ColorOrAuto, ColorPropertyValue, ColorScheme, PrintColorAdjust};
 pub use self::column::ColumnCount;

components/style/values/mod.rs

@@ -586,6 +586,12 @@ pub trait IsAuto {
 pub struct TimelineName(TimelineOrKeyframesName);
 
 impl TimelineName {
+    /// Create a new TimelineName from Atom.
+    #[cfg(feature = "gecko")]
+    pub fn from_atom(atom: Atom) -> Self {
+        Self(TimelineOrKeyframesName::from_atom(atom))
+    }
+
     /// Returns the `none` value.
     pub fn none() -> Self {
         Self(TimelineOrKeyframesName::none())

components/style/values/specified/box.rs

@@ -874,6 +874,49 @@ impl Parse for AnimationTimeline {
     }
 }
 
+/// A value for the scroll-timeline-name.
+///
+/// Note: The spec doesn't mention `auto` for scroll-timeline-name. However, `auto` is a keyword in
+/// animation-timeline, so we reject `auto` for scroll-timeline-name now.
+///
+/// https://drafts.csswg.org/scroll-animations-1/rewrite#scroll-timeline-name
+#[derive(
+    Clone,
+    Debug,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct ScrollTimelineName(pub TimelineName);
+
+impl ScrollTimelineName {
+    /// Returns the `none` value.
+    pub fn none() -> Self {
+        Self(TimelineName::none())
+    }
+}
+
+impl Parse for ScrollTimelineName {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(name) = input.try_parse(|input| TimelineName::parse(context, input)) {
+            return Ok(Self(name));
+        }
+
+        input.expect_ident_matching("none")?;
+        Ok(Self(TimelineName::none()))
+    }
+}
+
 /// https://drafts.csswg.org/css-scroll-snap-1/#snap-axis
 #[allow(missing_docs)]
 #[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]

components/style/values/specified/mod.rs

@@ -41,7 +41,7 @@ pub use self::box_::{Appearance, BreakBetween, BreakWithin, ContainerName, Conta
 pub use self::box_::{Clear, ContentVisibility, Float, Overflow, OverflowAnchor};
 pub use self::box_::{OverflowClipBox, OverscrollBehavior, Perspective, Resize, ScrollbarGutter};
 pub use self::box_::{ScrollSnapAlign, ScrollSnapAxis, ScrollSnapStop};
-pub use self::box_::{ScrollSnapStrictness, ScrollSnapType};
+pub use self::box_::{ScrollSnapStrictness, ScrollSnapType, ScrollTimelineName};
 pub use self::box_::{TouchAction, TransitionProperty, VerticalAlign, WillChange};
 pub use self::color::{Color, ColorOrAuto, ColorPropertyValue, ColorScheme, PrintColorAdjust};
 pub use self::column::ColumnCount;