Bug 1897619. Implement parsing of CSS 'position-anchor' property. r=emilio,firefox-style-system-reviewers

Differential Revision: https://phabricator.services.mozilla.com/D210880

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

@@ -143,6 +143,7 @@ exports.ANIMATION_TYPE_FOR_LONGHANDS = [
       "paint-order",
       "pointer-events",
       "position",
+      "position-anchor",
       "print-color-adjust",
       "quotes",
       "resize",

dom/base/use_counter_metrics.yaml

@@ -107,7 +107,7 @@ use.counter:
     send_in_pings:
       - use-counters
 
-# Total of 2305 use counter metrics (excludes denominators).
+# Total of 2307 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 699 'CSS (page)' use counters.
+# Total of 700 'CSS (page)' use counters.
 use.counter.css.page:
   css_align_content:
     type: counter
@@ -19759,6 +19759,23 @@ use.counter.css.page:
     send_in_pings:
       - use-counters
 
+  css_position_anchor:
+    type: counter
+    description: >
+      Whether a page used the CSS property position-anchor.
+      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_quotes:
     type: counter
     description: >
@@ -27426,7 +27443,7 @@ use.counter.css.page:
     send_in_pings:
       - use-counters
 
-# Total of 699 'CSS (document)' use counters.
+# Total of 700 'CSS (document)' use counters.
 use.counter.css.doc:
   css_align_content:
     type: counter
@@ -31644,6 +31661,23 @@ use.counter.css.doc:
     send_in_pings:
       - use-counters
 
+  css_position_anchor:
+    type: counter
+    description: >
+      Whether a document used the CSS property position-anchor.
+      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_quotes:
     type: counter
     description: >

layout/style/ServoBindings.toml

@@ -622,6 +622,7 @@ cbindgen-types = [
     { gecko = "StyleAu", servo = "app_units::Au" },
     { gecko = "StyleAnchorName", servo = "crate::values::computed::position::AnchorName" },
     { gecko = "StyleAnchorScope", servo = "crate::values::computed::position::AnchorScope" },
+    { gecko = "StylePositionAnchor", servo = "crate::values::computed::position::PositionAnchor" },
 ]
 
 mapped-generic-types = [

layout/style/nsStyleStruct.cpp

@@ -1051,6 +1051,7 @@ nsStylePosition::nsStylePosition()
       mHeight(StyleSize::Auto()),
       mMinHeight(StyleSize::Auto()),
       mMaxHeight(StyleMaxSize::None()),
+      mPositionAnchor(StylePositionAnchor::Auto()),
       mFlexBasis(StyleFlexBasis::Size(StyleSize::Auto())),
       mAspectRatio(StyleAspectRatio::Auto()),
       mGridAutoFlow(StyleGridAutoFlow::ROW),
@@ -1099,6 +1100,7 @@ nsStylePosition::nsStylePosition(const nsStylePosition& aSource)
       mHeight(aSource.mHeight),
       mMinHeight(aSource.mMinHeight),
       mMaxHeight(aSource.mMaxHeight),
+      mPositionAnchor(aSource.mPositionAnchor),
       mFlexBasis(aSource.mFlexBasis),
       mGridAutoColumns(aSource.mGridAutoColumns),
       mGridAutoRows(aSource.mGridAutoRows),
@@ -1276,6 +1278,13 @@ nsChangeHint nsStylePosition::CalcDifference(
     }
   }
 
+  if (mPositionAnchor != aNewData.mPositionAnchor) {
+    // 'position-anchor' provides a default anchor for other anchor positioning
+    // properties in the event that they don't specify one explicitly.
+    // TODO(jwatt): Re-evaluate what we're doing here.
+    hint |= nsChangeHint_NeutralChange;
+  }
+
   if (mAspectRatio != aNewData.mAspectRatio) {
     hint |= nsChangeHint_ReflowHintsForISizeChange |
             nsChangeHint_ReflowHintsForBSizeChange;

layout/style/nsStyleStruct.h

@@ -744,6 +744,11 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStylePosition {
   StyleSize mHeight;
   StyleSize mMinHeight;
   StyleMaxSize mMaxHeight;
+
+  // 'auto' or a `<dashed-ident>` referencing an anchor positioning anchor
+  // element.
+  mozilla::StylePositionAnchor mPositionAnchor;
+
   mozilla::StyleFlexBasis mFlexBasis;
   StyleImplicitGridTracks mGridAutoColumns;
   StyleImplicitGridTracks mGridAutoRows;

layout/style/test/property_database.js

@@ -13337,6 +13337,15 @@ if (IsCSSPropertyPrefEnabled("layout.css.anchor-positioning.enabled")) {
       "--foo,",
     ],
   };
+
+  gCSSProperties["position-anchor"] = {
+    domProp: "positionAnchor",
+    inherited: false,
+    type: CSS_TYPE_LONGHAND,
+    initial_values: ["auto"],
+    other_values: ["--foo"],
+    invalid_values: ["none", "--foo, auto", "auto, --bar", "foo"],
+  };
 }
 
 if (false) {

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

@@ -331,6 +331,17 @@ ${helpers.predefined_type(
     )}
 % endfor
 
+${helpers.predefined_type(
+    "position-anchor",
+    "PositionAnchor",
+    "computed::PositionAnchor::auto()",
+    engines="gecko",
+    animation_value_type="discrete",
+    gecko_pref="layout.css.anchor-positioning.enabled",
+    spec="https://drafts.csswg.org/css-anchor-position-1/#propdef-position-anchor",
+    affects="layout",
+)}
+
 ${helpers.single_keyword(
     "box-sizing",
     "content-box border-box",

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

@@ -90,6 +90,7 @@ pub use self::page::{PageName, PageOrientation, PageSize, PageSizeOrientation, P
 pub use self::percentage::{NonNegativePercentage, Percentage};
 pub use self::position::AnchorName;
 pub use self::position::AnchorScope;
+pub use self::position::PositionAnchor;
 pub use self::position::AspectRatio;
 pub use self::position::{
     GridAutoFlow, GridTemplateAreas, MasonryAutoFlow, Position, PositionOrAuto, ZIndex,

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

@@ -13,7 +13,8 @@ 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::{AnchorName, AnchorScope, GridAutoFlow, GridTemplateAreas, MasonryAutoFlow};
+pub use crate::values::specified::position::{GridAutoFlow, GridTemplateAreas, MasonryAutoFlow};
+pub use crate::values::specified::position::{AnchorName, AnchorScope, PositionAnchor};
 use crate::Zero;
 use std::fmt::{self, Write};
 use style_traits::{CssWriter, ToCss};

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

@@ -83,6 +83,7 @@ pub use self::percentage::{NonNegativePercentage, Percentage};
 pub use self::position::AspectRatio;
 pub use self::position::AnchorName;
 pub use self::position::AnchorScope;
+pub use self::position::PositionAnchor;
 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

@@ -456,6 +456,39 @@ impl Parse for AnchorScope {
     }
 }
 
+/// https://drafts.csswg.org/css-anchor-position-1/#propdef-position-anchor
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum PositionAnchor {
+    /// `auto`
+    Auto,
+    /// `<dashed-ident>`
+    Ident(DashedIdent),
+}
+
+impl PositionAnchor {
+    /// Return the `auto` value.
+    pub fn auto() -> Self {
+        Self::Auto
+    }
+
+    /// Returns whether this is the `auto` value.
+    pub fn is_auto(&self) -> bool {
+        *self == Self::Auto
+    }
+}
+
 /// Represents a side, either horizontal or vertical, of a CSS position.
 pub trait Side {
     /// Returns the start side.

servo/ports/geckolib/cbindgen.toml

@@ -111,6 +111,7 @@ include = [
   "DisplayInside",
   "DisplayMode",
   "Platform",
+  "PositionAnchor",
   "GtkThemeFamily",
   "PrefersColorScheme",
   "PrefersContrast",