style: Switch to the new scroll-snap-type syntax for the old scroll snap implementation and drop the scroll-snap-type-{x,y} longhands.

Now scroll-snap-type is a longhand property.

Differential Revision: https://phabricator.services.mozilla.com/D21622

components/style/properties/data.py

@@ -341,7 +341,9 @@ class Longhand(object):
                 "SVGOpacity",
                 "SVGPaintOrder",
                 "ScrollSnapAlign",
+                "ScrollSnapAxis",
                 "ScrollSnapStrictness",
+                "ScrollSnapType",
                 "TextAlign",
                 "TextDecorationLine",
                 "TextEmphasisPosition",

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

@@ -427,18 +427,15 @@ ${helpers.predefined_type(
     animation_value_type="discrete",
 )}
 
-% for axis in ["x", "y"]:
+${helpers.predefined_type(
-    ${helpers.predefined_type(
+    "scroll-snap-type",
-        "scroll-snap-type-" + axis,
+    "ScrollSnapType",
-        "ScrollSnapStrictness",
+    "computed::ScrollSnapType::none()",
-        "computed::ScrollSnapStrictness::None",
+    products="gecko",
-        products="gecko",
+    gecko_pref="layout.css.scroll-snap.enabled",
-        needs_context=False,
+    spec="https://drafts.csswg.org/css-scroll-snap-1/#scroll-snap-type",
-        gecko_pref="layout.css.scroll-snap.enabled",
+    animation_value_type="discrete",
-        spec="Nonstandard (https://developer.mozilla.org/en-US/docs/Web/CSS/scroll-snap-type-x)",
+)}
-        animation_value_type="discrete",
-    )}
-% endfor
 
 % for axis in ["x", "y"]:
     ${helpers.predefined_type(

components/style/properties/shorthands/box.mako.rs

@@ -303,36 +303,6 @@ macro_rules! try_parse_one {
     }
 </%helpers:shorthand>
 
-<%helpers:shorthand name="scroll-snap-type" products="gecko"
-                    gecko_pref="layout.css.scroll-snap.enabled"
-                    sub_properties="scroll-snap-type-x scroll-snap-type-y"
-                    spec="https://drafts.csswg.org/css-scroll-snap/#propdef-scroll-snap-type">
-    use crate::properties::longhands::scroll_snap_type_x;
-
-    pub fn parse_value<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Longhands, ParseError<'i>> {
-        let result = scroll_snap_type_x::parse(context, input)?;
-        Ok(expanded! {
-            scroll_snap_type_x: result,
-            scroll_snap_type_y: result,
-        })
-    }
-
-    impl<'a> ToCss for LonghandsToSerialize<'a>  {
-        // Serializes into the single keyword value if both scroll-snap-type-x and scroll-snap-type-y are same.
-        // Otherwise into an empty string. This is done to match Gecko's behaviour.
-        fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result where W: fmt::Write {
-            if self.scroll_snap_type_x == self.scroll_snap_type_y {
-                self.scroll_snap_type_x.to_css(dest)
-            } else {
-                Ok(())
-            }
-        }
-    }
-</%helpers:shorthand>
-
 ${helpers.two_properties_shorthand(
     "overscroll-behavior",
     "overscroll-behavior-x",

components/style/values/computed/box.rs

@@ -14,8 +14,8 @@ use crate::values::specified::box_ as specified;
 pub use crate::values::specified::box_::{AnimationName, Appearance, BreakBetween, BreakWithin};
 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_::{OverflowAnchor, OverflowClipBox, OverscrollBehavior};
-pub use crate::values::specified::box_::{OverscrollBehavior, ScrollSnapAlign, ScrollSnapStrictness};
+pub use crate::values::specified::box_::{ScrollSnapAlign, ScrollSnapAxis, ScrollSnapStrictness, ScrollSnapType};
 pub use crate::values::specified::box_::{TouchAction, TransitionProperty, WillChange};
 
 /// A computed value for the `vertical-align` property.

components/style/values/computed/mod.rs

@@ -42,7 +42,8 @@ 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_::{ScrollSnapAlign, ScrollSnapStrictness, TouchAction, VerticalAlign, WillChange};
+pub use self::box_::{ScrollSnapAlign, ScrollSnapAxis, ScrollSnapStrictness, ScrollSnapType};
+pub use self::box_::{TouchAction, VerticalAlign, WillChange};
 pub use self::color::{Color, ColorOrAuto, ColorPropertyValue};
 pub use self::column::ColumnCount;
 pub use self::counters::{Content, ContentItem, CounterIncrement, CounterSetOrReset};

components/style/values/specified/box.rs

@@ -379,6 +379,32 @@ impl Parse for AnimationName {
     }
 }
 
+/// https://drafts.csswg.org/css-scroll-snap-1/#snap-axis
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum ScrollSnapAxis {
+    X,
+    Y,
+    Block,
+    Inline,
+    Both,
+}
+
 /// https://drafts.csswg.org/css-scroll-snap-1/#snap-strictness
 #[allow(missing_docs)]
 #[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
@@ -398,11 +424,77 @@ impl Parse for AnimationName {
 )]
 #[repr(u8)]
 pub enum ScrollSnapStrictness {
-    None,
+    #[css(skip)]
+    None, // Used to represent scroll-snap-type: none.  It's not parsed.
     Mandatory,
     Proximity,
 }
 
+/// https://drafts.csswg.org/css-scroll-snap-1/#scroll-snap-type
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct ScrollSnapType {
+    axis: ScrollSnapAxis,
+    strictness: ScrollSnapStrictness,
+}
+
+impl ScrollSnapType {
+    /// Returns `none`.
+    #[inline]
+    pub fn none() -> Self {
+        Self {
+            axis: ScrollSnapAxis::Both,
+            strictness: ScrollSnapStrictness::None,
+        }
+    }
+}
+
+impl Parse for ScrollSnapType {
+    /// none | [ x | y | block | inline | both ] [ mandatory | proximity ]?
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if input.try(|input| input.expect_ident_matching("none")).is_ok() {
+            return Ok(ScrollSnapType::none());
+        }
+
+        let axis = ScrollSnapAxis::parse(input)?;
+        let strictness = input.try(ScrollSnapStrictness::parse).unwrap_or(ScrollSnapStrictness::Proximity);
+        Ok(Self { axis, strictness })
+    }
+}
+
+impl ToCss for ScrollSnapType {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.strictness == ScrollSnapStrictness::None {
+            return dest.write_str("none");
+        }
+        self.axis.to_css(dest)?;
+        if self.strictness != ScrollSnapStrictness::Proximity {
+            dest.write_str(" ")?;
+            self.strictness.to_css(dest)?;
+        }
+        Ok(())
+    }
+}
+
 /// Specified value of scroll-snap-align keyword value.
 #[allow(missing_docs)]
 #[derive(

components/style/values/specified/mod.rs

@@ -40,7 +40,7 @@ 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_::{ScrollSnapAlign, ScrollSnapStrictness};
+pub use self::box_::{ScrollSnapAlign, ScrollSnapAxis, ScrollSnapStrictness, ScrollSnapType};
 pub use self::box_::{TouchAction, TransitionProperty, VerticalAlign, WillChange};
 pub use self::color::{Color, ColorOrAuto, ColorPropertyValue};
 pub use self::column::ColumnCount;