Unreverse declarations in memory.

components/script/dom/element.rs

@@ -788,7 +788,7 @@ impl Element {
                 // than that.
                 let existing_declarations = Arc::make_mut(existing_declarations);
 
-                while let Some(mut incoming_declaration) = declarations.pop() {
+                for mut incoming_declaration in declarations {
                     let mut replaced = false;
                     for existing_declaration in &mut *existing_declarations {
                         if existing_declaration.name() == incoming_declaration.name() {
@@ -799,8 +799,7 @@ impl Element {
                     }
 
                     if !replaced {
-                        // inserting instead of pushing since the declarations are in reverse order
-                        existing_declarations.insert(0, incoming_declaration);
+                        existing_declarations.push(incoming_declaration);
                     }
                 }
 

components/style/properties/properties.mako.rs

@@ -14,7 +14,7 @@ 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, Rev, Repeat, repeat};
+use std::iter::{Iterator, Chain, Zip, Repeat, repeat};
 use std::slice;
 use std::sync::Arc;
 
@@ -296,12 +296,11 @@ pub struct PropertyDeclarationBlock {
 impl PropertyDeclarationBlock {
     /// Provides an iterator of all declarations, with indication of !important value
     pub fn declarations(&self) -> Chain<
-        Zip<Rev<slice::Iter<PropertyDeclaration>>, Repeat<Importance>>,
-        Zip<Rev<slice::Iter<PropertyDeclaration>>, Repeat<Importance>>
+        Zip<slice::Iter<PropertyDeclaration>, Repeat<Importance>>,
+        Zip<slice::Iter<PropertyDeclaration>, Repeat<Importance>>
     > {
-        // Declarations are stored in reverse order.
-        let normal = self.normal.iter().rev().zip(repeat(Importance::Normal));
-        let important = self.important.iter().rev().zip(repeat(Importance::Important));
+        let normal = self.normal.iter().zip(repeat(Importance::Normal));
+        let important = self.important.iter().zip(repeat(Importance::Important));
         normal.chain(important)
     }
 }
@@ -589,7 +588,7 @@ pub fn parse_property_declaration_list(context: &ParserContext, input: &mut Pars
 
 
 /// Only keep the last declaration for any given property.
-/// The input is in source order, output in reverse source order.
+/// The input and output are in source order
 fn deduplicate_property_declarations(declarations: Vec<PropertyDeclaration>)
                                      -> Vec<PropertyDeclaration> {
     let mut deduplicated = vec![];
@@ -618,6 +617,7 @@ fn deduplicate_property_declarations(declarations: Vec<PropertyDeclaration>)
         }
         deduplicated.push(declaration)
     }
+    deduplicated.reverse();
     deduplicated
 }
 
@@ -1683,8 +1683,7 @@ 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() {
-        // Declarations are already stored in reverse order.
-        for declaration in sub_list.declarations.iter() {
+        for declaration in sub_list.declarations.iter().rev() {
             match *declaration {
                 % for style_struct in data.active_style_structs():
                     % for property in style_struct.longhands:
@@ -1815,8 +1814,7 @@ 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() {
-        // Declarations are already stored in reverse order.
-        for declaration in sub_list.declarations.iter() {
+        for declaration in sub_list.declarations.iter().rev() {
             match *declaration {
                 PropertyDeclaration::Custom(ref name, ref value) => {
                     ::custom_properties::cascade(
@@ -1874,8 +1872,7 @@ 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() {
-                // Declarations are already stored in reverse order.
-                for declaration in sub_list.declarations.iter() {
+                for declaration in sub_list.declarations.iter().rev() {
                     if let PropertyDeclaration::Custom(..) = *declaration {
                         continue
                     }

tests/unit/style/properties/serialization.rs

@@ -39,8 +39,6 @@ fn property_declaration_block_should_serialize_correctly() {
     let height = DeclaredValue::Value(LengthOrPercentageOrAuto::Length(Length::from_px(20f32)));
     important.push(PropertyDeclaration::Height(height));
 
-    normal.reverse();
-    important.reverse();
     let block = PropertyDeclarationBlock {
         normal: Arc::new(normal),
         important: Arc::new(important)

tests/unit/style/stylesheets.rs

@@ -39,6 +39,16 @@ fn test_parse_stylesheet() {
     let stylesheet = Stylesheet::from_str(css, url, Origin::UserAgent,
                                           Box::new(CSSErrorReporterTest),
                                           ParserContextExtraData::default());
+    macro_rules! assert_eq {
+        ($left: expr, $right: expr) => {
+            let left = $left;
+            let right = $right;
+            if left != right {
+                panic!("{:#?} != {:#?}", left, right)
+            }
+        }
+    }
+
     assert_eq!(stylesheet, Stylesheet {
         origin: Origin::UserAgent,
         media: None,
@@ -157,13 +167,6 @@ fn test_parse_stylesheet() {
                 ],
                 declarations: PropertyDeclarationBlock {
                     normal: Arc::new(vec![
-                        PropertyDeclaration::BackgroundClip(DeclaredValue::Initial),
-                        PropertyDeclaration::BackgroundOrigin(DeclaredValue::Initial),
-                        PropertyDeclaration::BackgroundSize(DeclaredValue::Initial),
-                        PropertyDeclaration::BackgroundImage(DeclaredValue::Initial),
-                        PropertyDeclaration::BackgroundAttachment(DeclaredValue::Initial),
-                        PropertyDeclaration::BackgroundRepeat(DeclaredValue::Initial),
-                        PropertyDeclaration::BackgroundPosition(DeclaredValue::Initial),
                         PropertyDeclaration::BackgroundColor(DeclaredValue::Value(
                             longhands::background_color::SpecifiedValue {
                                 authored: Some("blue".to_owned()),
@@ -172,6 +175,13 @@ fn test_parse_stylesheet() {
                                 }),
                             }
                         )),
+                        PropertyDeclaration::BackgroundPosition(DeclaredValue::Initial),
+                        PropertyDeclaration::BackgroundRepeat(DeclaredValue::Initial),
+                        PropertyDeclaration::BackgroundAttachment(DeclaredValue::Initial),
+                        PropertyDeclaration::BackgroundImage(DeclaredValue::Initial),
+                        PropertyDeclaration::BackgroundSize(DeclaredValue::Initial),
+                        PropertyDeclaration::BackgroundOrigin(DeclaredValue::Initial),
+                        PropertyDeclaration::BackgroundClip(DeclaredValue::Initial),
                     ]),
                     important: Arc::new(vec![]),
                 },