Auto merge of #18398 - canaltinova:at-page-rule, r=emilio

stylo: Pass the @page values to precomputed pseudo element declarations

We were parsing @page rules correctly and serializing for cssom when we
we need. But we weren't actually including them to the pseudo element
declarations when we need to print a page.

Reviewed by emilio on Bugzilla.

---
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix [Bug 1394035](https://bugzilla.mozilla.org/show_bug.cgi?id=1394035)

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---
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components/style/stylist.rs

@@ -21,7 +21,7 @@ use properties::{AnimationRules, PropertyDeclarationBlock};
 #[cfg(feature = "servo")]
 use properties::INHERIT_ALL;
 use properties::IS_LINK;
-use rule_tree::{CascadeLevel, RuleTree, StyleSource};
+use rule_tree::{CascadeLevel, RuleTree, StrongRuleNode, StyleSource};
 use selector_map::{PrecomputedHashMap, SelectorMap, SelectorMapEntry};
 use selector_parser::{SelectorImpl, PerPseudoElementMap, PseudoElement};
 use selectors::attr::NamespaceConstraint;
@@ -40,7 +40,7 @@ use std::ops;
 use style_traits::viewport::ViewportConstraints;
 use stylesheet_set::{OriginValidity, SheetRebuildKind, StylesheetSet, StylesheetIterator, StylesheetFlusher};
 #[cfg(feature = "gecko")]
-use stylesheets::{CounterStyleRule, FontFaceRule, FontFeatureValuesRule};
+use stylesheets::{CounterStyleRule, FontFaceRule, FontFeatureValuesRule, PageRule};
 use stylesheets::{CssRule, Origin, OriginSet, PerOrigin, PerOriginIter};
 #[cfg(feature = "gecko")]
 use stylesheets::{MallocEnclosingSizeOfFn, MallocSizeOf, MallocSizeOfBox, MallocSizeOfFn};
@@ -357,6 +357,12 @@ impl DocumentCascadeData {
                         .borrow_mut_for_origin(&origin)
                         .add_counter_style(guard, rule);
                 }
+                #[cfg(feature = "gecko")]
+                CssRule::Page(ref rule) => {
+                    _extra_data
+                        .borrow_mut_for_origin(&origin)
+                        .add_page(rule);
+                }
                 // We don't care about any other rule.
                 _ => {}
             }
@@ -711,17 +717,33 @@ impl Stylist {
     ) -> Arc<ComputedValues> {
         debug_assert!(pseudo.is_precomputed());
 
-        let rule_node =
+        let rule_node = self.rule_node_for_precomputed_pseudo(
-            match self.cascade_data.precomputed_pseudo_element_decls.get(pseudo) {
+            guards,
-                Some(declarations) => {
+            pseudo,
-                    self.rule_tree.insert_ordered_rules_with_important(
+            None,
-                        declarations.into_iter().map(|a| (a.source.clone(), a.level())),
+        );
-                        guards
-                    )
-                }
-                None => self.rule_tree.root().clone(),
-            };
 
+        self.precomputed_values_for_pseudo_with_rule_node(
+            guards,
+            pseudo,
+            parent,
+            cascade_flags,
+            font_metrics,
+            &rule_node
+        )
+    }
+
+    /// Computes the style for a given "precomputed" pseudo-element with
+    /// given rule node.
+    pub fn precomputed_values_for_pseudo_with_rule_node(
+        &self,
+        guards: &StylesheetGuards,
+        pseudo: &PseudoElement,
+        parent: Option<&ComputedValues>,
+        cascade_flags: CascadeFlags,
+        font_metrics: &FontMetricsProvider,
+        rule_node: &StrongRuleNode
+    ) -> Arc<ComputedValues> {
         // NOTE(emilio): We skip calculating the proper layout parent style
         // here.
         //
@@ -739,7 +761,7 @@ impl Stylist {
         properties::cascade(
             &self.device,
             Some(pseudo),
-            &rule_node,
+            rule_node,
             guards,
             parent,
             parent,
@@ -751,6 +773,43 @@ impl Stylist {
         )
     }
 
+    /// Returns the rule node for given precomputed pseudo-element.
+    ///
+    /// If we want to include extra declarations to this precomputed pseudo-element,
+    /// we can provide a vector of ApplicableDeclarationBlock to extra_declarations
+    /// argument. This is useful for providing extra @page rules.
+    pub fn rule_node_for_precomputed_pseudo(
+        &self,
+        guards: &StylesheetGuards,
+        pseudo: &PseudoElement,
+        extra_declarations: Option<Vec<ApplicableDeclarationBlock>>,
+    ) -> StrongRuleNode {
+        let mut decl;
+        let declarations = match self.cascade_data.precomputed_pseudo_element_decls.get(pseudo) {
+            Some(declarations) => {
+                match extra_declarations {
+                    Some(mut extra_decls) => {
+                        decl = declarations.clone();
+                        decl.append(&mut extra_decls);
+                        Some(&decl)
+                    },
+                    None => Some(declarations),
+                }
+            }
+            None => extra_declarations.as_ref(),
+        };
+
+        match declarations {
+            Some(decls) => {
+                self.rule_tree.insert_ordered_rules_with_important(
+                    decls.into_iter().map(|a| (a.source.clone(), a.level())),
+                    guards
+                )
+            },
+            None => self.rule_tree.root().clone(),
+        }
+    }
+
     /// Returns the style for an anonymous box of the given type.
     #[cfg(feature = "servo")]
     pub fn style_for_anonymous(
@@ -1611,6 +1670,10 @@ pub struct ExtraStyleData {
     /// A map of effective counter-style rules.
     #[cfg(feature = "gecko")]
     pub counter_styles: PrecomputedHashMap<Atom, Arc<Locked<CounterStyleRule>>>,
+
+    /// A map of effective page rules.
+    #[cfg(feature = "gecko")]
+    pub pages: Vec<Arc<Locked<PageRule>>>,
 }
 
 #[cfg(feature = "gecko")]
@@ -1634,6 +1697,11 @@ impl ExtraStyleData {
         let name = rule.read_with(guard).mName.raw::<nsIAtom>().into();
         self.counter_styles.insert(name, rule.clone());
     }
+
+    /// Add the given @page rule.
+    fn add_page(&mut self, rule: &Arc<Locked<PageRule>>) {
+        self.pages.push(rule.clone());
+    }
 }
 
 impl ExtraStyleData {
@@ -1643,6 +1711,7 @@ impl ExtraStyleData {
             self.font_faces.clear();
             self.font_feature_values.clear();
             self.counter_styles.clear();
+            self.pages.clear();
         }
     }
 

ports/geckolib/glue.rs

@@ -12,6 +12,7 @@ use std::env;
 use std::fmt::Write;
 use std::iter;
 use std::ptr;
+use style::applicable_declarations::ApplicableDeclarationBlock;
 use style::context::{CascadeInputs, QuirksMode, SharedStyleContext, StyleContext};
 use style::context::ThreadLocalStyleContext;
 use style::data::ElementStyles;
@@ -113,7 +114,7 @@ use style::properties::PROHIBIT_DISPLAY_CONTENTS;
 use style::properties::animated_properties::{AnimatableLonghand, AnimationValue};
 use style::properties::animated_properties::compare_property_priority;
 use style::properties::parse_one_declaration_into;
-use style::rule_tree::StyleSource;
+use style::rule_tree::{CascadeLevel, StyleSource};
 use style::selector_parser::PseudoElementCascadeType;
 use style::shared_lock::{SharedRwLockReadGuard, StylesheetGuards, ToCssWithGuard, Locked};
 use style::string_cache::Atom;
@@ -1679,11 +1680,44 @@ pub extern "C" fn Servo_ComputedValues_GetForAnonymousBox(parent_style_or_null:
         cascade_flags.insert(IS_FIELDSET_CONTENT);
     }
     let metrics = get_metrics_provider_for_product();
-    data.stylist.precomputed_values_for_pseudo(
+
+    // If the pseudo element is PageContent, we should append the precomputed
+    // pseudo element declerations with specified page rules.
+    let page_decls = match pseudo {
+        PseudoElement::PageContent => {
+            let mut declarations = vec![];
+            let iter = data.extra_style_data.iter_origins_rev();
+            for (data, origin) in iter {
+                let level = match origin {
+                    Origin::UserAgent => CascadeLevel::UANormal,
+                    Origin::User => CascadeLevel::UserNormal,
+                    Origin::Author => CascadeLevel::AuthorNormal,
+                };
+                for rule in data.pages.iter() {
+                    declarations.push(ApplicableDeclarationBlock::from_declarations(
+                        rule.read_with(level.guard(&guards)).block.clone(),
+                        level
+                    ));
+                }
+            }
+            Some(declarations)
+        },
+        _ => None,
+    };
+
+    let rule_node = data.stylist.rule_node_for_precomputed_pseudo(
+        &guards,
+        &pseudo,
+        page_decls,
+    );
+
+    data.stylist.precomputed_values_for_pseudo_with_rule_node(
         &guards,
         &pseudo,
         parent_style_or_null.map(|x| &*x),
-        cascade_flags, &metrics
+        cascade_flags,
+        &metrics,
+        &rule_node
     ).into()
 }