Bug 1897405 p1. Implement parsing of CSS 'anchor-name'. r=emilio,devtools-reviewers,firefox-style-system-reviewers,nchevobbe

Differential Revision: https://phabricator.services.mozilla.com/D210787

devtools/server/actors/animation-type-longhand.js

@@ -9,6 +9,7 @@ exports.ANIMATION_TYPE_FOR_LONGHANDS = [
   [
     "discrete",
     new Set([
+      "anchor-name",
       "align-content",
       "align-items",
       "align-self",

dom/base/use_counter_metrics.yaml

@@ -107,7 +107,7 @@ use.counter:
     send_in_pings:
       - use-counters
 
-# Total of 2301 use counter metrics (excludes denominators).
+# Total of 2303 use counter metrics (excludes denominators).
 # Total of 354 'page' use counters.
 use.counter.page:
   svgsvgelement_getelementbyid:
@@ -15541,7 +15541,7 @@ use.counter.deprecated_ops.doc:
     send_in_pings:
       - use-counters
 
-# Total of 697 'CSS (page)' use counters.
+# Total of 698 'CSS (page)' use counters.
 use.counter.css.page:
   css_align_content:
     type: counter
@@ -18586,6 +18586,23 @@ use.counter.css.page:
     send_in_pings:
       - use-counters
 
+  css_anchor_name:
+    type: counter
+    description: >
+      Whether a page used the CSS property anchor-name.
+      Compare against `use.counter.top_level_content_documents_destroyed`
+      to calculate the rate.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1852098
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1852098
+    notification_emails:
+      - dom-core@mozilla.com
+      - emilio@mozilla.com
+    expires: never
+    send_in_pings:
+      - use-counters
+
   css_animation_composition:
     type: counter
     description: >
@@ -27392,7 +27409,7 @@ use.counter.css.page:
     send_in_pings:
       - use-counters
 
-# Total of 697 'CSS (document)' use counters.
+# Total of 698 'CSS (document)' use counters.
 use.counter.css.doc:
   css_align_content:
     type: counter
@@ -30437,6 +30454,23 @@ use.counter.css.doc:
     send_in_pings:
       - use-counters
 
+  css_anchor_name:
+    type: counter
+    description: >
+      Whether a document used the CSS property anchor-name.
+      Compare against `use.counter.content_documents_destroyed`
+      to calculate the rate.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1852098
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1852098
+    notification_emails:
+      - dom-core@mozilla.com
+      - emilio@mozilla.com
+    expires: never
+    send_in_pings:
+      - use-counters
+
   css_animation_composition:
     type: counter
     description: >

layout/style/ServoBindings.toml

@@ -620,6 +620,7 @@ cbindgen-types = [
     { gecko = "StyleLockedFontFaceRule", servo = "crate::gecko::arc_types::LockedFontFaceRule" },
     { gecko = "StyleBaselineSource", servo = "crate::values::computed::BaselineSource" },
     { gecko = "StyleAu", servo = "app_units::Au" },
+    { gecko = "StyleAnchorName", servo = "crate::values::computed::position::AnchorName" },
 ]
 
 mapped-generic-types = [

layout/style/nsStyleStruct.cpp

@@ -2151,7 +2151,8 @@ nsStyleDisplay::nsStyleDisplay(const nsStyleDisplay& aSource)
       mWebkitLineClamp(aSource.mWebkitLineClamp),
       mShapeImageThreshold(aSource.mShapeImageThreshold),
       mShapeMargin(aSource.mShapeMargin),
-      mShapeOutside(aSource.mShapeOutside) {
+      mShapeOutside(aSource.mShapeOutside),
+      mAnchorName(aSource.mAnchorName) {
   MOZ_COUNT_CTOR(nsStyleDisplay);
 }
 
@@ -2522,7 +2523,8 @@ nsChangeHint nsStyleDisplay::CalcDifference(
                 mContentVisibility != aNewData.mContentVisibility ||
                 mContainerType != aNewData.mContainerType ||
                 mContain != aNewData.mContain ||
-                mContainerName != aNewData.mContainerName)) {
+                mContainerName != aNewData.mContainerName ||
+                mAnchorName != aNewData.mAnchorName)) {
     hint |= nsChangeHint_NeutralChange;
   }
 

layout/style/nsStyleStruct.h

@@ -1316,6 +1316,10 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleDisplay {
 
   mozilla::StyleShapeOutside mShapeOutside;
 
+  // 'none', 'all', or a list of one or more `<dashed-ident>` identifiers that
+  // anchor positioned elements may reference.
+  mozilla::StyleAnchorName mAnchorName;
+
   mozilla::Maybe<mozilla::WindowButtonType> GetWindowButtonType() const {
     if (MOZ_LIKELY(mDefaultAppearance == mozilla::StyleAppearance::None)) {
       return mozilla::Nothing();

layout/style/test/property_database.js

@@ -13295,6 +13295,25 @@ if (IsCSSPropertyPrefEnabled("layout.css.contain-intrinsic-size.enabled")) {
   };
 }
 
+if (IsCSSPropertyPrefEnabled("layout.css.anchor-positioning.enabled")) {
+  gCSSProperties["anchor-name"] = {
+    domProp: "anchorName",
+    inherited: false,
+    type: CSS_TYPE_LONGHAND,
+    initial_values: ["none"],
+    other_values: ["--foo", "--foo, --baz", "--foo,--baz", "--foo ,--baz"],
+    invalid_values: [
+      "--foo --bar",
+      "foo",
+      "none bar",
+      "none --baz",
+      "--foo bar",
+      ",--foo",
+      "--foo,",
+    ],
+  };
+}
+
 if (false) {
   // TODO These properties are chrome-only, and are not exposed via CSSOM.
   // We may still want to find a way to test them. See bug 1206999.

modules/libpref/init/StaticPrefList.yaml

@@ -8436,6 +8436,14 @@
   value: false
   mirror: always
 
+# Whether to enable CSS Anchor Positioning support.
+# https://drafts.csswg.org/css-anchor-position-1/
+- name: layout.css.anchor-positioning.enabled
+  type: RelaxedAtomicBool
+  value: false
+  mirror: always
+  rust: true
+
 # Override DPI. A value of -1 means use the maximum of 96 and the system DPI.
 # A value of 0 means use the system DPI. A positive value is used as the DPI.
 # This sets the physical size of a device pixel and thus controls the

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

@@ -61,6 +61,19 @@ impl computed_value::T {
 }
 </%helpers:single_keyword>
 
+// Changes do not invalidate our element. We handle notify/invalidating
+// elements that reference anchor-name elsewhere.
+${helpers.predefined_type(
+    "anchor-name",
+    "AnchorName",
+    "computed::AnchorName::none()",
+    engines="gecko",
+    animation_value_type="discrete",
+    gecko_pref="layout.css.anchor-positioning.enabled",
+    spec="https://drafts.csswg.org/css-anchor-position-1/#propdef-anchor-name",
+    affects="",
+)}
+
 ${helpers.predefined_type(
     "float",
     "Float",

servo/components/style/values/computed/mod.rs

@@ -88,6 +88,7 @@ pub use self::motion::{OffsetPath, OffsetPosition, OffsetRotate};
 pub use self::outline::OutlineStyle;
 pub use self::page::{PageName, PageOrientation, PageSize, PageSizeOrientation, PaperSize};
 pub use self::percentage::{NonNegativePercentage, Percentage};
+pub use self::position::AnchorName;
 pub use self::position::AspectRatio;
 pub use self::position::{
     GridAutoFlow, GridTemplateAreas, MasonryAutoFlow, Position, PositionOrAuto, ZIndex,

servo/components/style/values/computed/position.rs

@@ -13,7 +13,7 @@ use crate::values::generics::position::Position as GenericPosition;
 use crate::values::generics::position::PositionComponent as GenericPositionComponent;
 use crate::values::generics::position::PositionOrAuto as GenericPositionOrAuto;
 use crate::values::generics::position::ZIndex as GenericZIndex;
-pub use crate::values::specified::position::{GridAutoFlow, GridTemplateAreas, MasonryAutoFlow};
+pub use crate::values::specified::position::{AnchorName, GridAutoFlow, GridTemplateAreas, MasonryAutoFlow};
 use crate::Zero;
 use std::fmt::{self, Write};
 use style_traits::{CssWriter, ToCss};

servo/components/style/values/mod.rs

@@ -592,6 +592,21 @@ impl ToCss for CustomIdent {
 )]
 pub struct DashedIdent(pub Atom);
 
+impl DashedIdent {
+    /// Parse an already-tokenizer identifier
+    pub fn from_ident<'i>(
+        location: SourceLocation,
+        ident: &CowRcStr<'i>,
+    ) -> Result<Self, ParseError<'i>> {
+        if !ident.starts_with("--") {
+            return Err(
+                location.new_custom_error(SelectorParseErrorKind::UnexpectedIdent(ident.clone()))
+            );
+        }
+        Ok(Self(Atom::from(ident.as_ref())))
+    }
+}
+
 impl Parse for DashedIdent {
     fn parse<'i, 't>(
         _: &ParserContext,
@@ -599,11 +614,7 @@ impl Parse for DashedIdent {
     ) -> Result<Self, ParseError<'i>> {
         let location = input.current_source_location();
         let ident = input.expect_ident()?;
-        if ident.starts_with("--") {
+        Self::from_ident(location, ident)
-            Ok(Self(Atom::from(ident.as_ref())))
-        } else {
-            Err(location.new_custom_error(SelectorParseErrorKind::UnexpectedIdent(ident.clone())))
-        }
     }
 }
 

servo/components/style/values/specified/mod.rs

@@ -81,6 +81,7 @@ pub use self::outline::OutlineStyle;
 pub use self::page::{PageName, PageOrientation, PageSize, PageSizeOrientation, PaperSize};
 pub use self::percentage::{NonNegativePercentage, Percentage};
 pub use self::position::AspectRatio;
+pub use self::position::AnchorName;
 pub use self::position::{GridAutoFlow, GridTemplateAreas, Position, PositionOrAuto};
 pub use self::position::{MasonryAutoFlow, MasonryItemOrder, MasonryPlacement};
 pub use self::position::{PositionComponent, ZIndex};

servo/components/style/values/specified/position.rs

@@ -10,6 +10,7 @@
 use crate::parser::{Parse, ParserContext};
 use crate::selector_map::PrecomputedHashMap;
 use crate::str::HTML_SPACE_CHARACTERS;
+use crate::values::DashedIdent;
 use crate::values::computed::LengthPercentage as ComputedLengthPercentage;
 use crate::values::computed::{Context, Percentage, ToComputedValue};
 use crate::values::generics::position::AspectRatio as GenericAspectRatio;
@@ -22,10 +23,12 @@ use crate::{Atom, Zero};
 use cssparser::Parser;
 use selectors::parser::SelectorParseErrorKind;
 use servo_arc::Arc;
+use smallvec::{smallvec, SmallVec};
 use std::collections::hash_map::Entry;
 use std::fmt::{self, Write};
 use style_traits::values::specified::AllowedNumericType;
 use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss};
+use style_traits::arc_slice::ArcSlice;
 
 /// The specified value of a CSS `<position>`
 pub type Position = GenericPosition<HorizontalPosition, VerticalPosition>;
@@ -337,6 +340,73 @@ impl<S: Side> PositionComponent<S> {
     }
 }
 
+/// https://drafts.csswg.org/css-anchor-position-1/#propdef-anchor-name
+#[repr(transparent)]
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub struct AnchorName(#[css(iterable, if_empty = "none")] #[ignore_malloc_size_of = "Arc"] pub crate::ArcSlice<DashedIdent>);
+
+impl AnchorName {
+    /// Return the `none` value.
+    pub fn none() -> Self {
+        Self(Default::default())
+    }
+
+    /// Returns whether this is the `none` value.
+    pub fn is_none(&self) -> bool {
+        self.0.is_empty()
+    }
+}
+
+impl Parse for AnchorName {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        let first = input.expect_ident()?;
+        if first.eq_ignore_ascii_case("none") {
+            return Ok(Self::none());
+        }
+        // The common case is probably just to have a single anchor name, so
+        // space for four on the stack should be plenty.
+        let mut idents: SmallVec<[DashedIdent; 4]> = smallvec![DashedIdent::from_ident(
+            location,
+            first,
+        )?];
+        while input.try_parse(|input| input.expect_comma()).is_ok() {
+            idents.push(DashedIdent::parse(context, input)?);
+        }
+        Ok(AnchorName(ArcSlice::from_iter(idents.drain(..))))
+    }
+}
+
+impl ToCss for AnchorName {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        let mut iter = self.0.iter();
+        match iter.next() {
+            None => return dest.write_str("none"),
+            Some(f) => f.to_css(dest)?,
+        }
+        for name in iter {
+            dest.write_str(", ")?;
+            name.to_css(dest)?;
+        }
+        Ok(())
+    }
+}
+
 /// Represents a side, either horizontal or vertical, of a CSS position.
 pub trait Side {
     /// Returns the start side.

servo/ports/geckolib/cbindgen.toml

@@ -82,6 +82,7 @@ exclude = [
   "AuthorStyles",
 ]
 include = [
+  "AnchorName",
   "AnimationTimeline",
   "AnimationIterationCount",
   "AnimationDirection",