style: Implement basic @page-rule selector parsing

This does not support any of the pseudo page types.

Differential Revision: https://phabricator.services.mozilla.com/D131532

4 files changed, 167 insertions, 20 deletions

diff --git a/components/style/stylesheets/mod.rs b/components/style/stylesheets/mod.rs
index f6348c6190d..d48b7504797 100644
--- a/components/style/stylesheets/mod.rs
+++ b/components/style/stylesheets/mod.rs
@@ -56,7 +56,7 @@ pub use self::loader::StylesheetLoader;
 pub use self::media_rule::MediaRule;
 pub use self::namespace_rule::NamespaceRule;
 pub use self::origin::{Origin, OriginSet, OriginSetIterator, PerOrigin, PerOriginIter};
-pub use self::page_rule::PageRule;
+pub use self::page_rule::{PageRule, PageSelector, PageSelectors};
 pub use self::rule_list::{CssRules, CssRulesHelpers};
 pub use self::rule_parser::{InsertRuleContext, State, TopLevelRuleParser};
 pub use self::rules_iterator::{AllRules, EffectiveRules};
diff --git a/components/style/stylesheets/page_rule.rs b/components/style/stylesheets/page_rule.rs
index 3edf562258f..7bf62f5c9e7 100644
--- a/components/style/stylesheets/page_rule.rs
+++ b/components/style/stylesheets/page_rule.rs
@@ -6,27 +6,100 @@
 //!
 //! [page]: https://drafts.csswg.org/css2/page.html#page-box
 
+use crate::parser::{Parse, ParserContext};
 use crate::properties::PropertyDeclarationBlock;
 use crate::shared_lock::{DeepCloneParams, DeepCloneWithLock, Locked};
 use crate::shared_lock::{SharedRwLock, SharedRwLockReadGuard, ToCssWithGuard};
 use crate::str::CssStringWriter;
-use cssparser::SourceLocation;
+use crate::values::{AtomIdent, CustomIdent};
+use style_traits::{CssWriter, ParseError, ToCss};
+use cssparser::{ToCss as CssParserToCss, Parser, SourceLocation};
 #[cfg(feature = "gecko")]
 use malloc_size_of::{MallocSizeOf, MallocSizeOfOps, MallocUnconditionalShallowSizeOf};
 use servo_arc::Arc;
 use std::fmt::{self, Write};
 
+/// Type of a single [`@page`][page selector]
+///
+/// We do not support pseudo selectors yet.
+/// [page-selectors]: https://drafts.csswg.org/css2/page.html#page-selectors
+#[derive(Clone, Debug, Eq, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToShmem)]
+pub struct PageSelector(pub AtomIdent);
+
+impl PageSelector {
+    /// Checks if the ident matches a page-name's ident.
+    ///
+    /// This does not currently take pseudo selectors into account.
+    #[inline]
+    pub fn ident_matches(&self, other: &CustomIdent) -> bool {
+        self.0.0 == other.0
+    }
+}
+
+impl Parse for PageSelector {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let s = input.expect_ident()?;
+        Ok(PageSelector(AtomIdent::from(&**s)))
+    }
+}
+
+impl ToCss for PageSelector {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write
+    {
+        (&self.0).to_css(dest)
+    }
+}
+
+/// A list of [`@page`][page selectors]
+///
+/// [page-selectors]: https://drafts.csswg.org/css2/page.html#page-selectors
+#[derive(Clone, Debug, Default, MallocSizeOf, ToCss, ToShmem)]
+#[css(comma)]
+pub struct PageSelectors(#[css(iterable)] pub Box<[PageSelector]>);
+
+impl PageSelectors {
+    /// Creates a new PageSelectors from a Vec, as from parse_comma_separated
+    #[inline]
+    pub fn new(s: Vec<PageSelector>) -> Self {
+        PageSelectors(s.into())
+    }
+    /// Returns true iff there are any page selectors
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.as_slice().is_empty()
+    }
+    /// Get the underlying PageSelector data as a slice
+    #[inline]
+    pub fn as_slice(&self) -> &[PageSelector] {
+        &*self.0
+    }
+}
+
+impl Parse for PageSelectors {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(PageSelectors::new(input.parse_comma_separated(|i| PageSelector::parse(context, i))?))
+    }
+}
+
 /// A [`@page`][page] rule.
 ///
 /// This implements only a limited subset of the CSS
 /// 2.2 syntax.
 ///
-/// In this subset, [page selectors][page-selectors] are not implemented.
-///
 /// [page]: https://drafts.csswg.org/css2/page.html#page-box
 /// [page-selectors]: https://drafts.csswg.org/css2/page.html#page-selectors
-#[derive(Debug, ToShmem)]
+#[derive(Clone, Debug, ToShmem)]
 pub struct PageRule {
+    /// Selectors of the page-rule
+    pub selectors: PageSelectors,
     /// The declaration block this page rule contains.
     pub block: Arc<Locked<PropertyDeclarationBlock>>,
     /// The source position this rule was found at.
@@ -38,7 +111,7 @@ impl PageRule {
     #[cfg(feature = "gecko")]
     pub fn size_of(&self, guard: &SharedRwLockReadGuard, ops: &mut MallocSizeOfOps) -> usize {
         // Measurement of other fields may be added later.
-        self.block.unconditional_shallow_size_of(ops) + self.block.read_with(guard).size_of(ops)
+        self.block.unconditional_shallow_size_of(ops) + self.block.read_with(guard).size_of(ops) + self.selectors.size_of(ops)
     }
 }
 
@@ -46,13 +119,18 @@ impl ToCssWithGuard for PageRule {
     /// Serialization of PageRule is not specced, adapted from steps for
     /// StyleRule.
     fn to_css(&self, guard: &SharedRwLockReadGuard, dest: &mut CssStringWriter) -> fmt::Result {
-        dest.write_str("@page { ")?;
+        dest.write_str("@page ")?;
+        if !self.selectors.is_empty() {
+            self.selectors.to_css(&mut CssWriter::new(dest))?;
+            dest.write_char(' ')?;
+        }
+        dest.write_str("{ ")?;
         let declaration_block = self.block.read_with(guard);
         declaration_block.to_css(dest)?;
         if !declaration_block.declarations().is_empty() {
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
         }
-        dest.write_str("}")
+        dest.write_char('}')
     }
 }
 
@@ -64,6 +142,7 @@ impl DeepCloneWithLock for PageRule {
         _params: &DeepCloneParams,
     ) -> Self {
         PageRule {
+            selectors: self.selectors.clone(),
             block: Arc::new(lock.wrap(self.block.read_with(&guard).clone())),
             source_location: self.source_location.clone(),
         }
diff --git a/components/style/stylesheets/rule_parser.rs b/components/style/stylesheets/rule_parser.rs
index 3c0d8a5c231..868137b52cd 100644
--- a/components/style/stylesheets/rule_parser.rs
+++ b/components/style/stylesheets/rule_parser.rs
@@ -23,8 +23,8 @@ use crate::stylesheets::stylesheet::Namespaces;
 use crate::stylesheets::supports_rule::SupportsCondition;
 use crate::stylesheets::{
     viewport_rule, AllowImportRules, CorsMode, CssRule, CssRuleType, CssRules, DocumentRule,
-    FontFeatureValuesRule, KeyframesRule, MediaRule, NamespaceRule, PageRule, RulesMutateError,
-    ScrollTimelineRule, StyleRule, StylesheetLoader, SupportsRule, ViewportRule,
+    FontFeatureValuesRule, KeyframesRule, MediaRule, NamespaceRule, PageRule, PageSelectors,
+    RulesMutateError, ScrollTimelineRule, StyleRule, StylesheetLoader, SupportsRule, ViewportRule,
 };
 use crate::values::computed::font::FamilyName;
 use crate::values::{CssUrl, CustomIdent, KeyframesName, TimelineName};
@@ -168,8 +168,8 @@ pub enum AtRulePrelude {
     Viewport,
     /// A @keyframes rule, with its animation name and vendor prefix if exists.
     Keyframes(KeyframesName, Option<VendorPrefix>),
-    /// A @page rule prelude.
-    Page,
+    /// A @page rule prelude, with its page name if it exists.
+    Page(PageSelectors),
     /// A @document rule, with its conditional.
     Document(DocumentCondition),
     /// A @import rule prelude.
@@ -469,7 +469,11 @@ impl<'a, 'b, 'i> AtRuleParser<'i> for NestedRuleParser<'a, 'b> {
                 AtRulePrelude::Keyframes(name, prefix)
             },
             "page" if cfg!(feature = "gecko") => {
-                AtRulePrelude::Page
+                AtRulePrelude::Page(if static_prefs::pref!("layout.css.named-pages.enabled") {
+                    input.try_parse(|i| PageSelectors::parse(self.context, i)).unwrap_or_default()
+                } else {
+                    PageSelectors::default()
+                })
             },
             "-moz-document" if cfg!(feature = "gecko") => {
                 let cond = DocumentCondition::parse(self.context, input)?;
@@ -583,7 +587,7 @@ impl<'a, 'b, 'i> AtRuleParser<'i> for NestedRuleParser<'a, 'b> {
                     },
                 ))))
             },
-            AtRulePrelude::Page => {
+            AtRulePrelude::Page(selectors) => {
                 let context = ParserContext::new_with_rule_type(
                     self.context,
                     CssRuleType::Page,
@@ -592,6 +596,7 @@ impl<'a, 'b, 'i> AtRuleParser<'i> for NestedRuleParser<'a, 'b> {
 
                 let declarations = parse_property_declaration_list(&context, input, None);
                 Ok(CssRule::Page(Arc::new(self.shared_lock.wrap(PageRule {
+                    selectors,
                     block: Arc::new(self.shared_lock.wrap(declarations)),
                     source_location: start.source_location(),
                 }))))
diff --git a/components/style/stylist.rs b/components/style/stylist.rs
index 14f88c4fe22..dffc2e849ce 100644
--- a/components/style/stylist.rs
+++ b/components/style/stylist.rs
@@ -1612,6 +1612,52 @@ impl<T: 'static> LayerOrderedMap<T> {
     }
 }
 
+/// Wrapper to allow better tracking of memory usage by page rule lists.
+///
+/// This includes the layer ID for use with the named page table.
+#[derive(Clone, Debug, MallocSizeOf)]
+pub struct PageRuleData {
+    /// Layer ID for sorting page rules after matching.
+    pub layer: LayerId,
+    /// Page rule
+    #[ignore_malloc_size_of = "Arc, stylesheet measures as primary ref"]
+    pub rule: Arc<Locked<PageRule>>,
+}
+
+/// Wrapper to allow better tracking of memory usage by page rule lists.
+///
+/// This is meant to be used by the global page rule list which are already
+/// sorted by layer ID, since all global page rules are less specific than all
+/// named page rules that match a certain page.
+#[derive(Clone, Debug, Deref, MallocSizeOf)]
+pub struct PageRuleDataNoLayer(
+    #[ignore_malloc_size_of = "Arc, stylesheet measures as primary ref"]
+    pub Arc<Locked<PageRule>>,
+);
+
+/// Stores page rules indexed by page names.
+#[derive(Clone, Debug, Default, MallocSizeOf)]
+pub struct PageRuleMap {
+    /// Global, unnamed page rules.
+    pub global: LayerOrderedVec<PageRuleDataNoLayer>,
+    /// Named page rules
+    pub named: PrecomputedHashMap<Atom, SmallVec<[PageRuleData; 1]>>,
+}
+
+impl PageRuleMap {
+    #[inline]
+    fn clear(&mut self) {
+        self.global.clear();
+        self.named.clear();
+    }
+}
+
+impl MallocShallowSizeOf for PageRuleMap {
+    fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
+        self.global.size_of(ops) + self.named.shallow_size_of(ops)
+    }
+}
+
 /// This struct holds data which users of Stylist may want to extract
 /// from stylesheets which can be done at the same time as updating.
 #[derive(Clone, Debug, Default)]
@@ -1631,7 +1677,7 @@ pub struct ExtraStyleData {
 
     /// A map of effective page rules.
     #[cfg(feature = "gecko")]
-    pub pages: LayerOrderedVec<Arc<Locked<PageRule>>>,
+    pub pages: PageRuleMap,
 
     /// A map of effective scroll-timeline rules.
     #[cfg(feature = "gecko")]
@@ -1666,8 +1712,25 @@ impl ExtraStyleData {
     }
 
     /// Add the given @page rule.
-    fn add_page(&mut self, rule: &Arc<Locked<PageRule>>, layer: LayerId) {
-        self.pages.push(rule.clone(), layer);
+    fn add_page(
+        &mut self,
+        guard: &SharedRwLockReadGuard,
+        rule: &Arc<Locked<PageRule>>,
+        layer: LayerId,
+    ) -> Result<(), AllocErr> {
+        let page_rule = rule.read_with(guard);
+        if page_rule.selectors.0.is_empty() {
+            self.pages.global.push(PageRuleDataNoLayer(rule.clone()), layer);
+        } else {
+            // TODO: Handle pseudo-classes
+            self.pages.named.try_reserve(page_rule.selectors.0.len())?;
+            for name in page_rule.selectors.as_slice() {
+                let vec = self.pages.named.entry(name.0.0.clone()).or_default();
+                vec.try_reserve(1)?;
+                vec.push(PageRuleData{layer, rule: rule.clone()});
+            }
+        }
+        Ok(())
     }
 
     /// Add the given @scroll-timeline rule.
@@ -1685,7 +1748,7 @@ impl ExtraStyleData {
         self.font_faces.sort(layers);
         self.font_feature_values.sort(layers);
         self.counter_styles.sort(layers);
-        self.pages.sort(layers);
+        self.pages.global.sort(layers);
         self.scroll_timelines.sort(layers);
     }
 
@@ -2518,7 +2581,7 @@ impl CascadeData {
                 },
                 #[cfg(feature = "gecko")]
                 CssRule::Page(ref rule) => {
-                    self.extra_data.add_page(rule, current_layer_id);
+                    self.extra_data.add_page(guard, rule, current_layer_id)?;
                 },
                 CssRule::Viewport(..) => {},
                 _ => {