style: Update CSSOM for layer rules to the spec

Pretty mechanical.

Tests are in https://wpt.live/css/css-cascade/layer-rules-cssom.html
which (with a fix for @import tests which I'll submit separately) we
pass.

Sync for that is bug 1743936.

Differential Revision: https://phabricator.services.mozilla.com/D133387

components/style/gecko/arc_types.rs

@@ -12,9 +12,10 @@ use crate::gecko::url::CssUrlData;
 use crate::gecko_bindings::structs::{
     RawServoAnimationValue, RawServoCounterStyleRule, RawServoCssUrlData, RawServoDeclarationBlock,
     RawServoFontFaceRule, RawServoFontFeatureValuesRule, RawServoImportRule, RawServoKeyframe,
-    RawServoKeyframesRule, RawServoLayerRule, RawServoMediaList, RawServoMediaRule,
+    RawServoKeyframesRule, RawServoLayerBlockRule, RawServoLayerStatementRule, RawServoMediaList,
-    RawServoMozDocumentRule, RawServoNamespaceRule, RawServoPageRule, RawServoScrollTimelineRule,
+    RawServoMediaRule, RawServoMozDocumentRule, RawServoNamespaceRule, RawServoPageRule,
-    RawServoStyleRule, RawServoStyleSheetContents, RawServoSupportsRule, ServoCssRules,
+    RawServoScrollTimelineRule, RawServoStyleRule, RawServoStyleSheetContents,
+    RawServoSupportsRule, ServoCssRules,
 };
 use crate::gecko_bindings::sugar::ownership::{HasArcFFI, HasFFI, Strong};
 use crate::media_queries::MediaList;
@@ -24,8 +25,8 @@ use crate::shared_lock::Locked;
 use crate::stylesheets::keyframes_rule::Keyframe;
 use crate::stylesheets::{
     CounterStyleRule, CssRules, DocumentRule, FontFaceRule, FontFeatureValuesRule, ImportRule,
-    KeyframesRule, LayerRule, MediaRule, NamespaceRule, PageRule, ScrollTimelineRule, StyleRule,
+    KeyframesRule, LayerBlockRule, LayerStatementRule, MediaRule, NamespaceRule, PageRule,
-    StylesheetContents, SupportsRule,
+    ScrollTimelineRule, StyleRule, StylesheetContents, SupportsRule,
 };
 use servo_arc::{Arc, ArcBorrow};
 use std::{mem, ptr};
@@ -73,8 +74,11 @@ impl_arc_ffi!(Locked<Keyframe> => RawServoKeyframe
 impl_arc_ffi!(Locked<KeyframesRule> => RawServoKeyframesRule
               [Servo_KeyframesRule_AddRef, Servo_KeyframesRule_Release]);
 
-impl_arc_ffi!(Locked<LayerRule> => RawServoLayerRule
+impl_arc_ffi!(Locked<LayerBlockRule> => RawServoLayerBlockRule
-              [Servo_LayerRule_AddRef, Servo_LayerRule_Release]);
+              [Servo_LayerBlockRule_AddRef, Servo_LayerBlockRule_Release]);
+
+impl_arc_ffi!(Locked<LayerStatementRule> => RawServoLayerStatementRule
+              [Servo_LayerStatementRule_AddRef, Servo_LayerStatementRule_Release]);
 
 impl_arc_ffi!(Locked<MediaList> => RawServoMediaList
               [Servo_MediaList_AddRef, Servo_MediaList_Release]);

components/style/gecko/wrapper.rs

@@ -1578,8 +1578,8 @@ impl<'le> TElement for GeckoElement<'le> {
         use crate::properties::longhands::_x_text_zoom::SpecifiedValue as SpecifiedZoom;
         use crate::properties::longhands::color::SpecifiedValue as SpecifiedColor;
         use crate::properties::longhands::text_align::SpecifiedValue as SpecifiedTextAlign;
-        use crate::values::specified::color::Color;
         use crate::stylesheets::layer_rule::LayerOrder;
+        use crate::values::specified::color::Color;
         lazy_static! {
             static ref TH_RULE: ApplicableDeclarationBlock = {
                 let global_style_data = &*GLOBAL_STYLE_DATA;
@@ -1588,7 +1588,11 @@ impl<'le> TElement for GeckoElement<'le> {
                     Importance::Normal,
                 );
                 let arc = Arc::new_leaked(global_style_data.shared_lock.wrap(pdb));
-                ApplicableDeclarationBlock::from_declarations(arc, ServoCascadeLevel::PresHints, LayerOrder::root())
+                ApplicableDeclarationBlock::from_declarations(
+                    arc,
+                    ServoCascadeLevel::PresHints,
+                    LayerOrder::root(),
+                )
             };
             static ref TABLE_COLOR_RULE: ApplicableDeclarationBlock = {
                 let global_style_data = &*GLOBAL_STYLE_DATA;
@@ -1597,7 +1601,11 @@ impl<'le> TElement for GeckoElement<'le> {
                     Importance::Normal,
                 );
                 let arc = Arc::new_leaked(global_style_data.shared_lock.wrap(pdb));
-                ApplicableDeclarationBlock::from_declarations(arc, ServoCascadeLevel::PresHints, LayerOrder::root())
+                ApplicableDeclarationBlock::from_declarations(
+                    arc,
+                    ServoCascadeLevel::PresHints,
+                    LayerOrder::root(),
+                )
             };
             static ref MATHML_LANG_RULE: ApplicableDeclarationBlock = {
                 let global_style_data = &*GLOBAL_STYLE_DATA;
@@ -1606,7 +1614,11 @@ impl<'le> TElement for GeckoElement<'le> {
                     Importance::Normal,
                 );
                 let arc = Arc::new_leaked(global_style_data.shared_lock.wrap(pdb));
-                ApplicableDeclarationBlock::from_declarations(arc, ServoCascadeLevel::PresHints, LayerOrder::root())
+                ApplicableDeclarationBlock::from_declarations(
+                    arc,
+                    ServoCascadeLevel::PresHints,
+                    LayerOrder::root(),
+                )
             };
             static ref SVG_TEXT_DISABLE_ZOOM_RULE: ApplicableDeclarationBlock = {
                 let global_style_data = &*GLOBAL_STYLE_DATA;
@@ -1615,7 +1627,11 @@ impl<'le> TElement for GeckoElement<'le> {
                     Importance::Normal,
                 );
                 let arc = Arc::new_leaked(global_style_data.shared_lock.wrap(pdb));
-                ApplicableDeclarationBlock::from_declarations(arc, ServoCascadeLevel::PresHints, LayerOrder::root())
+                ApplicableDeclarationBlock::from_declarations(
+                    arc,
+                    ServoCascadeLevel::PresHints,
+                    LayerOrder::root(),
+                )
             };
         };
 

components/style/invalidation/stylesheets.rs

@@ -541,6 +541,7 @@ impl StylesheetInvalidationSet {
             Page(..) |
             Viewport(..) |
             FontFeatureValues(..) |
+            LayerStatement(..) |
             FontFace(..) |
             Keyframes(..) |
             ScrollTimeline(..) |
@@ -556,7 +557,7 @@ impl StylesheetInvalidationSet {
 
                 self.collect_invalidations_for_rule(rule, guard, device, quirks_mode)
             },
-            Document(..) | Import(..) | Media(..) | Supports(..) | Layer(..) => {
+            Document(..) | Import(..) | Media(..) | Supports(..) | LayerBlock(..) => {
                 if !is_generic_change &&
                     !EffectiveRules::is_effective(guard, device, quirks_mode, rule)
                 {
@@ -597,7 +598,8 @@ impl StylesheetInvalidationSet {
                     }
                 }
             },
-            Document(..) | Namespace(..) | Import(..) | Media(..) | Supports(..) | Layer(..) => {
+            Document(..) | Namespace(..) | Import(..) | Media(..) | Supports(..) |
+            LayerStatement(..) | LayerBlock(..) => {
                 // Do nothing, relevant nested rules are visited as part of the
                 // iteration.
             },

components/style/stylesheets/layer_rule.rs

@@ -159,71 +159,34 @@ impl ToCss for LayerName {
     }
 }
 
-/// The kind of layer rule this is.
 #[derive(Debug, ToShmem)]
-pub enum LayerRuleKind {
+/// A block `@layer <name>? { ... }`
-    /// A block `@layer <name>? { ... }`
+/// https://drafts.csswg.org/css-cascade-5/#layer-block
-    Block {
+pub struct LayerBlockRule {
-        /// The layer name, or `None` if anonymous.
+    /// The layer name, or `None` if anonymous.
-        name: Option<LayerName>,
+    pub name: Option<LayerName>,
-        /// The nested rules.
+    /// The nested rules.
-        rules: Arc<Locked<CssRules>>,
+    pub rules: Arc<Locked<CssRules>>,
-    },
+    /// The source position where this rule was found.
-    /// A statement `@layer <name>, <name>, <name>;`
-    Statement {
-        /// The list of layers to sort.
-        names: Vec<LayerName>,
-    },
-}
-
-/// A [`@layer`][layer] rule.
-///
-/// [layer]: https://drafts.csswg.org/css-cascade-5/#layering
-#[derive(Debug, ToShmem)]
-pub struct LayerRule {
-    /// The kind of layer rule we are.
-    pub kind: LayerRuleKind,
-    /// The source position where this media rule was found.
     pub source_location: SourceLocation,
 }
 
-impl ToCssWithGuard for LayerRule {
+impl ToCssWithGuard for LayerBlockRule {
     fn to_css(
         &self,
         guard: &SharedRwLockReadGuard,
         dest: &mut crate::str::CssStringWriter,
     ) -> fmt::Result {
         dest.write_str("@layer")?;
-        match self.kind {
+        if let Some(ref name) = self.name {
-            LayerRuleKind::Block {
+            dest.write_char(' ')?;
-                ref name,
+            name.to_css(&mut CssWriter::new(dest))?;
-                ref rules,
-            } => {
-                if let Some(ref name) = *name {
-                    dest.write_char(' ')?;
-                    name.to_css(&mut CssWriter::new(dest))?;
-                }
-                rules.read_with(guard).to_css_block(guard, dest)
-            },
-            LayerRuleKind::Statement { ref names } => {
-                let mut writer = CssWriter::new(dest);
-                let mut first = true;
-                for name in &**names {
-                    if first {
-                        writer.write_char(' ')?;
-                    } else {
-                        writer.write_str(", ")?;
-                    }
-                    first = false;
-                    name.to_css(&mut writer)?;
-                }
-                dest.write_char(';')
-            },
         }
+        self.rules.read_with(guard).to_css_block(guard, dest)
     }
 }
 
-impl DeepCloneWithLock for LayerRule {
+impl DeepCloneWithLock for LayerBlockRule {
     fn deep_clone_with_lock(
         &self,
         lock: &SharedRwLock,
@@ -231,25 +194,57 @@ impl DeepCloneWithLock for LayerRule {
         params: &DeepCloneParams,
     ) -> Self {
         Self {
-            kind: match self.kind {
+            name: self.name.clone(),
-                LayerRuleKind::Block {
+            rules: Arc::new(
-                    ref name,
+                lock.wrap(
-                    ref rules,
+                    self.rules
-                } => LayerRuleKind::Block {
+                        .read_with(guard)
-                    name: name.clone(),
+                        .deep_clone_with_lock(lock, guard, params),
-                    rules: Arc::new(
+                ),
-                        lock.wrap(
+            ),
-                            rules
-                                .read_with(guard)
-                                .deep_clone_with_lock(lock, guard, params),
-                        ),
-                    ),
-                },
-                LayerRuleKind::Statement { ref names } => LayerRuleKind::Statement {
-                    names: names.clone(),
-                },
-            },
             source_location: self.source_location.clone(),
         }
     }
 }
+
+/// A statement `@layer <name>, <name>, <name>;`
+///
+/// https://drafts.csswg.org/css-cascade-5/#layer-empty
+#[derive(Clone, Debug, ToShmem)]
+pub struct LayerStatementRule {
+    /// The list of layers to sort.
+    pub names: Vec<LayerName>,
+    /// The source position where this rule was found.
+    pub source_location: SourceLocation,
+}
+
+impl ToCssWithGuard for LayerStatementRule {
+    fn to_css(
+        &self,
+        _: &SharedRwLockReadGuard,
+        dest: &mut crate::str::CssStringWriter,
+    ) -> fmt::Result {
+        let mut writer = CssWriter::new(dest);
+        writer.write_str("@layer ")?;
+        let mut first = true;
+        for name in &*self.names {
+            if !first {
+                writer.write_str(", ")?;
+            }
+            first = false;
+            name.to_css(&mut writer)?;
+        }
+        writer.write_char(';')
+    }
+}
+
+impl DeepCloneWithLock for LayerStatementRule {
+    fn deep_clone_with_lock(
+        &self,
+        _: &SharedRwLock,
+        _: &SharedRwLockReadGuard,
+        _: &DeepCloneParams,
+    ) -> Self {
+        self.clone()
+    }
+}

components/style/stylesheets/mod.rs

@@ -51,7 +51,7 @@ pub use self::font_face_rule::FontFaceRule;
 pub use self::font_feature_values_rule::FontFeatureValuesRule;
 pub use self::import_rule::ImportRule;
 pub use self::keyframes_rule::KeyframesRule;
-pub use self::layer_rule::LayerRule;
+pub use self::layer_rule::{LayerBlockRule, LayerStatementRule};
 pub use self::loader::StylesheetLoader;
 pub use self::media_rule::MediaRule;
 pub use self::namespace_rule::NamespaceRule;
@@ -261,7 +261,8 @@ pub enum CssRule {
     Supports(Arc<Locked<SupportsRule>>),
     Page(Arc<Locked<PageRule>>),
     Document(Arc<Locked<DocumentRule>>),
-    Layer(Arc<Locked<LayerRule>>),
+    LayerBlock(Arc<Locked<LayerBlockRule>>),
+    LayerStatement(Arc<Locked<LayerStatementRule>>),
     ScrollTimeline(Arc<Locked<ScrollTimelineRule>>),
 }
 
@@ -304,9 +305,8 @@ impl CssRule {
                 lock.unconditional_shallow_size_of(ops) + lock.read_with(guard).size_of(guard, ops)
             },
 
-            // TODO(emilio): Add memory reporting for @layer rules.
+            // TODO(emilio): Add memory reporting for these rules.
-            CssRule::Layer(_) => 0,
+            CssRule::LayerBlock(_) | CssRule::LayerStatement(_) | CssRule::ScrollTimeline(_) => 0,
-            CssRule::ScrollTimeline(_) => 0,
         }
     }
 }
@@ -341,8 +341,9 @@ pub enum CssRuleType {
     Viewport = 15,
     // After viewport, all rules should return 0 from the API, but we still need
     // a constant somewhere.
-    Layer = 16,
+    LayerBlock = 16,
-    ScrollTimeline = 17,
+    LayerStatement = 17,
+    ScrollTimeline = 18,
 }
 
 #[allow(missing_docs)]
@@ -369,7 +370,8 @@ impl CssRule {
             CssRule::Supports(_) => CssRuleType::Supports,
             CssRule::Page(_) => CssRuleType::Page,
             CssRule::Document(_) => CssRuleType::Document,
-            CssRule::Layer(_) => CssRuleType::Layer,
+            CssRule::LayerBlock(_) => CssRuleType::LayerBlock,
+            CssRule::LayerStatement(_) => CssRuleType::LayerStatement,
             CssRule::ScrollTimeline(_) => CssRuleType::ScrollTimeline,
         }
     }
@@ -504,9 +506,15 @@ impl DeepCloneWithLock for CssRule {
                     lock.wrap(rule.deep_clone_with_lock(lock, guard, params)),
                 ))
             },
-            CssRule::Layer(ref arc) => {
+            CssRule::LayerStatement(ref arc) => {
                 let rule = arc.read_with(guard);
-                CssRule::Layer(Arc::new(
+                CssRule::LayerStatement(Arc::new(
+                    lock.wrap(rule.deep_clone_with_lock(lock, guard, params)),
+                ))
+            },
+            CssRule::LayerBlock(ref arc) => {
+                let rule = arc.read_with(guard);
+                CssRule::LayerBlock(Arc::new(
                     lock.wrap(rule.deep_clone_with_lock(lock, guard, params)),
                 ))
             },
@@ -534,7 +542,8 @@ impl ToCssWithGuard for CssRule {
             CssRule::Supports(ref lock) => lock.read_with(guard).to_css(guard, dest),
             CssRule::Page(ref lock) => lock.read_with(guard).to_css(guard, dest),
             CssRule::Document(ref lock) => lock.read_with(guard).to_css(guard, dest),
-            CssRule::Layer(ref lock) => lock.read_with(guard).to_css(guard, dest),
+            CssRule::LayerBlock(ref lock) => lock.read_with(guard).to_css(guard, dest),
+            CssRule::LayerStatement(ref lock) => lock.read_with(guard).to_css(guard, dest),
             CssRule::ScrollTimeline(ref lock) => lock.read_with(guard).to_css(guard, dest),
         }
     }

components/style/stylesheets/rule_parser.rs

@@ -17,14 +17,14 @@ use crate::stylesheets::document_rule::DocumentCondition;
 use crate::stylesheets::font_feature_values_rule::parse_family_name_list;
 use crate::stylesheets::import_rule::ImportLayer;
 use crate::stylesheets::keyframes_rule::parse_keyframe_list;
-use crate::stylesheets::layer_rule::{LayerName, LayerRuleKind};
+use crate::stylesheets::layer_rule::{LayerBlockRule, LayerName, LayerStatementRule};
 use crate::stylesheets::scroll_timeline_rule::ScrollTimelineDescriptors;
 use crate::stylesheets::stylesheet::Namespaces;
 use crate::stylesheets::supports_rule::SupportsCondition;
 use crate::stylesheets::{
     viewport_rule, AllowImportRules, CorsMode, CssRule, CssRuleType, CssRules, DocumentRule,
-    FontFeatureValuesRule, KeyframesRule, LayerRule, MediaRule, NamespaceRule, PageRule,
+    FontFeatureValuesRule, KeyframesRule, MediaRule, NamespaceRule, PageRule, RulesMutateError,
-    RulesMutateError, ScrollTimelineRule, StyleRule, StylesheetLoader, SupportsRule, ViewportRule,
+    ScrollTimelineRule, StyleRule, StylesheetLoader, SupportsRule, ViewportRule,
 };
 use crate::values::computed::font::FamilyName;
 use crate::values::{CssUrl, CustomIdent, KeyframesName, TimelineName};
@@ -613,13 +613,13 @@ impl<'a, 'b, 'i> AtRuleParser<'i> for NestedRuleParser<'a, 'b> {
                     0 | 1 => names.into_iter().next(),
                     _ => return Err(input.new_error(BasicParseErrorKind::AtRuleBodyInvalid)),
                 };
-                Ok(CssRule::Layer(Arc::new(self.shared_lock.wrap(LayerRule {
+                Ok(CssRule::LayerBlock(Arc::new(self.shared_lock.wrap(
-                    kind: LayerRuleKind::Block {
+                    LayerBlockRule {
                         name,
-                        rules: self.parse_nested_rules(input, CssRuleType::Layer),
+                        rules: self.parse_nested_rules(input, CssRuleType::LayerBlock),
+                        source_location: start.source_location(),
                     },
-                    source_location: start.source_location(),
+                ))))
-                }))))
             },
             AtRulePrelude::Import(..) | AtRulePrelude::Namespace(..) => {
                 // These rules don't have blocks.
@@ -654,8 +654,8 @@ impl<'a, 'b, 'i> AtRuleParser<'i> for NestedRuleParser<'a, 'b> {
                 if names.is_empty() {
                     return Err(());
                 }
-                CssRule::Layer(Arc::new(self.shared_lock.wrap(LayerRule {
+                CssRule::LayerStatement(Arc::new(self.shared_lock.wrap(LayerStatementRule {
-                    kind: LayerRuleKind::Statement { names },
+                    names,
                     source_location: start.source_location(),
                 })))
             },

components/style/stylesheets/rules_iterator.rs

@@ -70,6 +70,7 @@ where
             CssRule::Keyframes(_) |
             CssRule::ScrollTimeline(_) |
             CssRule::Page(_) |
+            CssRule::LayerStatement(_) |
             CssRule::FontFeatureValues(_) => None,
             CssRule::Import(ref import_rule) => {
                 let import_rule = import_rule.read_with(guard);
@@ -103,14 +104,9 @@ where
                 }
                 Some(supports_rule.rules.read_with(guard).0.iter())
             },
-            CssRule::Layer(ref lock) => {
+            CssRule::LayerBlock(ref lock) => {
-                use crate::stylesheets::layer_rule::LayerRuleKind;
-
                 let layer_rule = lock.read_with(guard);
-                match layer_rule.kind {
+                Some(layer_rule.rules.read_with(guard).0.iter())
-                    LayerRuleKind::Block { ref rules, .. } => Some(rules.read_with(guard).0.iter()),
-                    LayerRuleKind::Statement { .. } => None,
-                }
             },
         }
     }

components/style/stylesheets/stylesheet.rs

@@ -363,7 +363,8 @@ impl SanitizationKind {
             CssRule::Import(..) |
             // TODO(emilio): Perhaps Layer should not be always sanitized? But
             // we sanitize @media and co, so this seems safer for now.
-            CssRule::Layer(..) => false,
+            CssRule::LayerStatement(..) |
+            CssRule::LayerBlock(..) => false,
 
             CssRule::FontFace(..) | CssRule::Namespace(..) | CssRule::Style(..) => true,
 

components/style/stylist.rs

@@ -2516,35 +2516,25 @@ impl CascadeData {
                         self.effective_media_query_results.saw_effective(media_rule);
                     }
                 },
-                CssRule::Layer(ref lock) => {
+                CssRule::LayerBlock(ref lock) => {
-                    use crate::stylesheets::layer_rule::LayerRuleKind;
-
                     let layer_rule = lock.read_with(guard);
-                    match layer_rule.kind {
+                    children_layer_id = maybe_register_layers(
-                        LayerRuleKind::Block { ref name, .. } => {
+                        self,
-                            children_layer_id = maybe_register_layers(
+                        layer_rule.name.as_ref(),
-                                self,
+                        &mut current_layer,
-                                name.as_ref(),
+                        &mut layer_names_to_pop,
-                                &mut current_layer,
+                    );
-                                &mut layer_names_to_pop,
+                },
-                            );
+                CssRule::LayerStatement(ref lock) => {
-                        },
+                    let layer_rule = lock.read_with(guard);
-                        LayerRuleKind::Statement { ref names } => {
+                    for name in &*layer_rule.names {
-                            for name in &**names {
+                        let mut pushed = 0;
-                                let mut pushed = 0;
+                        // There are no children, so we can ignore the
-                                // There are no children, so we can ignore the
+                        // return value.
-                                // return value.
+                        maybe_register_layers(self, Some(name), &mut current_layer, &mut pushed);
-                                maybe_register_layers(
+                        for _ in 0..pushed {
-                                    self,
+                            current_layer.0.pop();
-                                    Some(name),
+                        }
-                                    &mut current_layer,
-                                    &mut pushed,
-                                );
-                                for _ in 0..pushed {
-                                    current_layer.0.pop();
-                                }
-                            }
-                        },
                     }
                 },
                 // We don't care about any other rule.
@@ -2660,7 +2650,8 @@ impl CascadeData {
                 CssRule::Page(..) |
                 CssRule::Viewport(..) |
                 CssRule::Document(..) |
-                CssRule::Layer(..) |
+                CssRule::LayerBlock(..) |
+                CssRule::LayerStatement(..) |
                 CssRule::FontFeatureValues(..) => {
                     // Not affected by device changes.
                     continue;