Merge normal and important declarations in style rules.

Have a single Vec instead of two. Fix #3426

components/style/animation.rs

@@ -15,7 +15,7 @@ use properties::longhands::animation_iteration_count::computed_value::AnimationI
 use properties::longhands::animation_play_state::computed_value::AnimationPlayState;
 use properties::longhands::transition_timing_function::computed_value::StartEnd;
 use properties::longhands::transition_timing_function::computed_value::TransitionTimingFunction;
-use properties::{self, ComputedValues};
+use properties::{self, ComputedValues, Importance};
 use selector_matching::DeclarationBlock;
 use std::sync::Arc;
 use std::sync::mpsc::Sender;
@@ -385,7 +385,8 @@ fn compute_style_for_animation_step(context: &SharedStyleContext,
         KeyframesStepValue::ComputedValues => style_from_cascade.clone(),
         KeyframesStepValue::Declarations(ref declarations) => {
             let declaration_block = DeclarationBlock {
-                declarations: declarations.clone(),
+                mixed_declarations: declarations.clone(),
+                importance: Importance::Normal,
                 source_order: 0,
                 specificity: ::std::u32::MAX,
             };

components/style/keyframes.rs

@@ -5,9 +5,9 @@
 use cssparser::{AtRuleParser, Parser, QualifiedRuleParser, RuleListParser};
 use cssparser::{DeclarationListParser, DeclarationParser};
 use parser::{ParserContext, log_css_error};
-use properties::PropertyDeclaration;
 use properties::PropertyDeclarationParseResult;
 use properties::animated_properties::TransitionProperty;
+use properties::{PropertyDeclaration, Importance};
 use std::sync::Arc;
 
 /// A number from 1 to 100, indicating the percentage of the animation where
@@ -72,7 +72,12 @@ impl KeyframeSelector {
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct Keyframe {
     pub selector: KeyframeSelector,
-    pub declarations: Arc<Vec<PropertyDeclaration>>,
+
+    /// `!important` is not allowed in keyframe declarations,
+    /// so the second value of these tuples is always `Importance::Normal`.
+    /// But including them enables `compute_style_for_animation_step` to create a `DeclarationBlock`
+    /// by cloning an `Arc<_>` (incrementing a reference count) rather than re-creating a `Vec<_>`.
+    pub declarations: Arc<Vec<(PropertyDeclaration, Importance)>>,
 }
 
 /// A keyframes step value. This can be a synthetised keyframes animation, that
@@ -82,7 +87,8 @@ pub struct Keyframe {
 #[derive(Debug, Clone, PartialEq)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub enum KeyframesStepValue {
-    Declarations(Arc<Vec<PropertyDeclaration>>),
+    /// See `Keyframe::declarations`’s docs about the presence of `Importance`.
+    Declarations(Arc<Vec<(PropertyDeclaration, Importance)>>),
     ComputedValues,
 }
 
@@ -108,7 +114,7 @@ impl KeyframesStep {
            value: KeyframesStepValue) -> Self {
         let declared_timing_function = match value {
             KeyframesStepValue::Declarations(ref declarations) => {
-                declarations.iter().any(|prop_decl| {
+                declarations.iter().any(|&(ref prop_decl, _)| {
                     match *prop_decl {
                         PropertyDeclaration::AnimationTimingFunction(..) => true,
                         _ => false,
@@ -148,8 +154,8 @@ fn get_animated_properties(keyframe: &Keyframe) -> Vec<TransitionProperty> {
     let mut ret = vec![];
     // NB: declarations are already deduplicated, so we don't have to check for
     // it here.
-    for declaration in keyframe.declarations.iter() {
-        if let Some(property) = TransitionProperty::from_declaration(&declaration) {
+    for &(ref declaration, _) in keyframe.declarations.iter() {
+        if let Some(property) = TransitionProperty::from_declaration(declaration) {
             ret.push(property);
         }
     }
@@ -247,7 +253,7 @@ impl<'a> QualifiedRuleParser for KeyframeListParser<'a> {
         let mut iter = DeclarationListParser::new(input, parser);
         while let Some(declaration) = iter.next() {
             match declaration {
-                Ok(d) => declarations.extend(d),
+                Ok(d) => declarations.extend(d.into_iter().map(|d| (d, Importance::Normal))),
                 Err(range) => {
                     let pos = range.start;
                     let message = format!("Unsupported keyframe property declaration: '{}'",

components/style/matching.rs

@@ -14,7 +14,7 @@ use context::{StyleContext, SharedStyleContext};
 use data::PrivateStyleData;
 use dom::{TElement, TNode, TRestyleDamage, UnsafeNode};
 use properties::longhands::display::computed_value as display;
-use properties::{ComputedValues, PropertyDeclaration, cascade};
+use properties::{ComputedValues, cascade};
 use selector_impl::{TheSelectorImpl, PseudoElement};
 use selector_matching::{DeclarationBlock, Stylist};
 use selectors::bloom::BloomFilter;
@@ -118,15 +118,11 @@ impl<'a> ApplicableDeclarationsCacheQuery<'a> {
 
 impl<'a> PartialEq for ApplicableDeclarationsCacheQuery<'a> {
     fn eq(&self, other: &ApplicableDeclarationsCacheQuery<'a>) -> bool {
-        if self.declarations.len() != other.declarations.len() {
-            return false
-        }
-        for (this, other) in self.declarations.iter().zip(other.declarations) {
-            if !arc_ptr_eq(&this.declarations, &other.declarations) {
-                return false
-            }
-        }
-        true
+        self.declarations.len() == other.declarations.len() &&
+        self.declarations.iter().zip(other.declarations).all(|(this, other)| {
+            arc_ptr_eq(&this.mixed_declarations, &other.mixed_declarations) &&
+            this.importance == other.importance
+        })
     }
 }
 impl<'a> Eq for ApplicableDeclarationsCacheQuery<'a> {}
@@ -143,8 +139,9 @@ impl<'a> Hash for ApplicableDeclarationsCacheQuery<'a> {
         for declaration in self.declarations {
             // Each declaration contians an Arc, which is a stable
             // pointer; we use that for hashing and equality.
-            let ptr = &*declaration.declarations as *const Vec<PropertyDeclaration>;
+            let ptr: *const Vec<_> = &*declaration.mixed_declarations;
             ptr.hash(state);
+            declaration.importance.hash(state);
         }
     }
 }

components/style/properties/properties.mako.rs

@@ -14,8 +14,6 @@ use std::ascii::AsciiExt;
 use std::boxed::Box as StdBox;
 use std::collections::HashSet;
 use std::fmt::{self, Write};
-use std::iter::{Iterator, Chain, Zip, Repeat, repeat};
-use std::slice;
 use std::sync::Arc;
 
 use app_units::Au;
@@ -264,7 +262,7 @@ mod property_bit_field {
 % endfor
 
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub enum Importance {
     /// Indicates a declaration without `!important`.
     Normal,
@@ -288,21 +286,7 @@ impl Importance {
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct PropertyDeclarationBlock {
     #[cfg_attr(feature = "servo", ignore_heap_size_of = "#7038")]
-    pub important: Arc<Vec<PropertyDeclaration>>,
-    #[cfg_attr(feature = "servo", ignore_heap_size_of = "#7038")]
-    pub normal: Arc<Vec<PropertyDeclaration>>,
-}
-
-impl PropertyDeclarationBlock {
-    /// Provides an iterator of all declarations, with indication of !important value
-    pub fn declarations(&self) -> Chain<
-        Zip<slice::Iter<PropertyDeclaration>, Repeat<Importance>>,
-        Zip<slice::Iter<PropertyDeclaration>, Repeat<Importance>>
-    > {
-        let normal = self.normal.iter().zip(repeat(Importance::Normal));
-        let important = self.important.iter().zip(repeat(Importance::Important));
-        normal.chain(important)
-    }
+    pub declarations: Arc<Vec<(PropertyDeclaration, Importance)>>,
 }
 
 impl ToCss for PropertyDeclarationBlock {
@@ -316,7 +300,7 @@ impl ToCss for PropertyDeclarationBlock {
         let mut already_serialized = Vec::new();
 
         // Step 3
-        for (declaration, importance) in self.declarations() {
+        for &(ref declaration, importance) in &*self.declarations {
             // Step 3.1
             let property = declaration.name();
 
@@ -330,7 +314,7 @@ impl ToCss for PropertyDeclarationBlock {
             if !shorthands.is_empty() {
 
                 // Step 3.3.1
-                let mut longhands = self.declarations()
+                let mut longhands = self.declarations.iter()
                     .filter(|d| !already_serialized.contains(&d.0.name()))
                     .collect::<Vec<_>>();
 
@@ -342,7 +326,7 @@ impl ToCss for PropertyDeclarationBlock {
                     let mut current_longhands = Vec::new();
                     let mut important_count = 0;
 
-                    for &(longhand, longhand_importance) in longhands.iter() {
+                    for &&(ref longhand, longhand_importance) in longhands.iter() {
                         let longhand_name = longhand.name();
                         if properties.iter().any(|p| &longhand_name == *p) {
                             current_longhands.push(longhand);
@@ -386,7 +370,7 @@ impl ToCss for PropertyDeclarationBlock {
                     for current_longhand in current_longhands {
                         // Substep 9
                         already_serialized.push(current_longhand.name());
-                        let index_to_remove = longhands.iter().position(|l| l.0 == current_longhand);
+                        let index_to_remove = longhands.iter().position(|l| l.0 == *current_longhand);
                         if let Some(index) = index_to_remove {
                             // Substep 10
                             longhands.remove(index);
@@ -557,8 +541,7 @@ impl<'a, 'b> DeclarationParser for PropertyDeclarationParser<'a, 'b> {
 
 pub fn parse_property_declaration_list(context: &ParserContext, input: &mut Parser)
                                        -> PropertyDeclarationBlock {
-    let mut important_declarations = Vec::new();
-    let mut normal_declarations = Vec::new();
+    let mut declarations = Vec::new();
     let parser = PropertyDeclarationParser {
         context: context,
     };
@@ -566,11 +549,7 @@ pub fn parse_property_declaration_list(context: &ParserContext, input: &mut Pars
     while let Some(declaration) = iter.next() {
         match declaration {
             Ok((results, importance)) => {
-                if importance.important() {
-                    important_declarations.extend(results);
-                } else {
-                    normal_declarations.extend(results);
-                }
+                declarations.extend(results.into_iter().map(|d| (d, importance)))
             }
             Err(range) => {
                 let pos = range.start;
@@ -581,46 +560,79 @@ pub fn parse_property_declaration_list(context: &ParserContext, input: &mut Pars
         }
     }
     PropertyDeclarationBlock {
-        important: Arc::new(deduplicate_property_declarations(important_declarations)),
-        normal: Arc::new(deduplicate_property_declarations(normal_declarations)),
+        declarations: Arc::new(deduplicate_property_declarations(declarations)),
     }
 }
 
 
-/// Only keep the last declaration for any given property.
+/// Only keep the "winning" declaration for any given property, by importance then source order.
 /// The input and output are in source order
-fn deduplicate_property_declarations(declarations: Vec<PropertyDeclaration>)
-                                     -> Vec<PropertyDeclaration> {
-    let mut deduplicated = vec![];
-    let mut seen = PropertyBitField::new();
-    let mut seen_custom = Vec::new();
-    for declaration in declarations.into_iter().rev() {
+fn deduplicate_property_declarations(declarations: Vec<(PropertyDeclaration, Importance)>)
+                                     -> Vec<(PropertyDeclaration, Importance)> {
+    let mut deduplicated = Vec::new();
+    let mut seen_normal = PropertyBitField::new();
+    let mut seen_important = PropertyBitField::new();
+    let mut seen_custom_normal = Vec::new();
+    let mut seen_custom_important = Vec::new();
+    for (declaration, importance) in declarations.into_iter().rev() {
         match declaration {
             % for property in data.longhands:
                 PropertyDeclaration::${property.camel_case}(..) => {
                     % if not property.derived_from:
-                        if seen.get_${property.ident}() {
-                            continue
+                        if importance.important() {
+                            if seen_important.get_${property.ident}() {
+                                continue
+                            }
+                            if seen_normal.get_${property.ident}() {
+                                remove_one(&mut deduplicated, |d| {
+                                    matches!(d, &(PropertyDeclaration::${property.camel_case}(..), _))
+                                })
+                            }
+                            seen_important.set_${property.ident}()
+                        } else {
+                            if seen_normal.get_${property.ident}() ||
+                               seen_important.get_${property.ident}() {
+                                continue
+                            }
+                            seen_normal.set_${property.ident}()
                         }
-                        seen.set_${property.ident}()
                     % else:
                         unreachable!();
                     % endif
                 },
             % endfor
             PropertyDeclaration::Custom(ref name, _) => {
-                if seen_custom.contains(name) {
-                    continue
+                if importance.important() {
+                    if seen_custom_important.contains(name) {
+                        continue
+                    }
+                    if seen_custom_normal.contains(name) {
+                        remove_one(&mut deduplicated, |d| {
+                            matches!(d, &(PropertyDeclaration::Custom(ref n, _), _) if n == name)
+                        })
+                    }
+                    seen_custom_important.push(name.clone())
+                } else {
+                    if seen_custom_normal.contains(name) ||
+                       seen_custom_important.contains(name) {
+                        continue
+                    }
+                    seen_custom_normal.push(name.clone())
                 }
-                seen_custom.push(name.clone())
             }
         }
-        deduplicated.push(declaration)
+        deduplicated.push((declaration, importance))
     }
     deduplicated.reverse();
     deduplicated
 }
 
+#[inline]
+fn remove_one<T, F: FnMut(&T) -> bool>(v: &mut Vec<T>, mut remove_this: F) {
+    let previous_len = v.len();
+    v.retain(|x| !remove_this(x));
+    debug_assert_eq!(v.len(), previous_len - 1);
+}
 
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 pub enum CSSWideKeyword {
@@ -1701,7 +1713,7 @@ fn cascade_with_cached_declarations(
     // Declaration blocks are stored in increasing precedence order,
     // we want them in decreasing order here.
     for sub_list in applicable_declarations.iter().rev() {
-        for declaration in sub_list.declarations.iter().rev() {
+        for declaration in sub_list.iter().rev() {
             match *declaration {
                 % for style_struct in data.active_style_structs():
                     % for property in style_struct.longhands:
@@ -1832,7 +1844,7 @@ pub fn cascade(viewport_size: Size2D<Au>,
     let mut custom_properties = None;
     let mut seen_custom = HashSet::new();
     for sub_list in applicable_declarations.iter().rev() {
-        for declaration in sub_list.declarations.iter().rev() {
+        for declaration in sub_list.iter().rev() {
             match *declaration {
                 PropertyDeclaration::Custom(ref name, ref value) => {
                     ::custom_properties::cascade(
@@ -1890,7 +1902,7 @@ pub fn cascade(viewport_size: Size2D<Au>,
     ComputedValues::do_cascade_property(|cascade_property| {
         % for category_to_cascade_now in ["early", "other"]:
             for sub_list in applicable_declarations.iter().rev() {
-                for declaration in sub_list.declarations.iter().rev() {
+                for declaration in sub_list.iter().rev() {
                     if let PropertyDeclaration::Custom(..) = *declaration {
                         continue
                     }

components/style/selector_matching.rs

@@ -9,7 +9,7 @@ use element_state::*;
 use error_reporting::StdoutErrorReporter;
 use keyframes::KeyframesAnimation;
 use media_queries::{Device, MediaType};
-use properties::{self, PropertyDeclaration, PropertyDeclarationBlock, ComputedValues};
+use properties::{self, PropertyDeclaration, PropertyDeclarationBlock, ComputedValues, Importance};
 use quickersort::sort_by;
 use restyle_hints::{RestyleHint, DependencySet};
 use selector_impl::{ElementExt, TheSelectorImpl, PseudoElement};
@@ -25,6 +25,7 @@ use std::collections::HashMap;
 use std::fmt;
 use std::hash::BuildHasherDefault;
 use std::hash::Hash;
+use std::slice;
 use std::sync::Arc;
 use string_cache::Atom;
 use style_traits::viewport::ViewportConstraints;
@@ -163,8 +164,8 @@ impl Stylist {
         // Take apart the StyleRule into individual Rules and insert
         // them into the SelectorMap of that priority.
         macro_rules! append(
-            ($style_rule: ident, $priority: ident) => {
-                if !$style_rule.declarations.$priority.is_empty() {
+            ($style_rule: ident, $priority: ident, $importance: expr) => {
+                if !$style_rule.declarations.declarations.is_empty() {
                     for selector in &$style_rule.selectors {
                         let map = if let Some(ref pseudo) = selector.pseudo_element {
                             self.pseudos_map
@@ -179,7 +180,8 @@ impl Stylist {
                             selector: selector.complex_selector.clone(),
                             declarations: DeclarationBlock {
                                 specificity: selector.specificity,
-                                declarations: $style_rule.declarations.$priority.clone(),
+                                mixed_declarations: $style_rule.declarations.declarations.clone(),
+                                importance: $importance,
                                 source_order: rules_source_order,
                             },
                         });
@@ -191,8 +193,8 @@ impl Stylist {
         for rule in stylesheet.effective_rules(&self.device) {
             match *rule {
                 CSSRule::Style(ref style_rule) => {
-                    append!(style_rule, normal);
-                    append!(style_rule, important);
+                    append!(style_rule, normal, Importance::Normal);
+                    append!(style_rule, important, Importance::Important);
                     rules_source_order += 1;
 
                     for selector in &style_rule.selectors {
@@ -397,7 +399,9 @@ impl Stylist {
             relations |= AFFECTED_BY_STYLE_ATTRIBUTE;
             Push::push(
                 applicable_declarations,
-                DeclarationBlock::from_declarations(sa.normal.clone()));
+                DeclarationBlock::from_declarations(
+                    sa.declarations.clone(),
+                    Importance::Normal));
         }
 
         debug!("style attr: {:?}", relations);
@@ -414,7 +418,9 @@ impl Stylist {
         if let Some(ref sa) = style_attribute {
             Push::push(
                 applicable_declarations,
-                DeclarationBlock::from_declarations(sa.important.clone()));
+                DeclarationBlock::from_declarations(
+                    sa.declarations.clone(),
+                    Importance::Important));
         }
 
         debug!("style attr important: {:?}", relations);
@@ -829,20 +835,64 @@ pub struct Rule {
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 #[derive(Debug, Clone)]
 pub struct DeclarationBlock {
-    pub declarations: Arc<Vec<PropertyDeclaration>>,
+    /// Contains declarations of either importance, but only those of self.importance are relevant.
+    /// Use DeclarationBlock::iter
+    pub mixed_declarations: Arc<Vec<(PropertyDeclaration, Importance)>>,
+    pub importance: Importance,
     pub source_order: usize,
     pub specificity: u32,
 }
 
 impl DeclarationBlock {
     #[inline]
-    pub fn from_declarations(declarations: Arc<Vec<PropertyDeclaration>>) -> Self {
+    pub fn from_declarations(declarations: Arc<Vec<(PropertyDeclaration, Importance)>>,
+                             importance: Importance)
+                             -> Self {
         DeclarationBlock {
-            declarations: declarations,
+            mixed_declarations: declarations,
+            importance: importance,
             source_order: 0,
             specificity: 0,
         }
     }
+
+    pub fn iter(&self) -> DeclarationBlockIter {
+        DeclarationBlockIter {
+            iter: self.mixed_declarations.iter(),
+            importance: self.importance,
+        }
+    }
+}
+
+pub struct DeclarationBlockIter<'a> {
+    iter: slice::Iter<'a, (PropertyDeclaration, Importance)>,
+    importance: Importance,
+}
+
+impl<'a> Iterator for DeclarationBlockIter<'a> {
+    type Item = &'a PropertyDeclaration;
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        while let Some(&(ref declaration, importance)) = self.iter.next() {
+            if importance == self.importance {
+                return Some(declaration)
+            }
+        }
+        None
+    }
+}
+
+impl<'a> DoubleEndedIterator for DeclarationBlockIter<'a> {
+    #[inline]
+    fn next_back(&mut self) -> Option<Self::Item> {
+        while let Some(&(ref declaration, importance)) = self.iter.next_back() {
+            if importance == self.importance {
+                return Some(declaration)
+            }
+        }
+        None
+    }
 }
 
 fn find_push<Str: Eq + Hash>(map: &mut HashMap<Str, Vec<Rule>>, key: Str, value: Rule) {