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style: Avoid extra allocations in serialization of a property declaration block.

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Concretely we avoid allocating and scanning a temporary vector of longhands not
yet serialized for each shorthand.

This doesn't save a lot of time in Linux, but I bet it's somewhat important on
OSX.
This commit is contained in:
Emilio Cobos Álvarez 2017-06-14 12:53:49 +02:00
parent 8b20d7a982
commit 6e85601858
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GPG key ID: 056B727BB9C1027C
1 changed files with 22 additions and 15 deletions
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37
components/style/properties/declaration_block.rs
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@ -14,6 +14,7 @@ use parser::{ParserContext, log_css_error};
use properties::animated_properties::AnimationValue;
use selectors::parser::SelectorParseError;
use shared_lock::Locked;
use smallvec::SmallVec;
use std::fmt;
use std::slice::Iter;
use style_traits::{PARSING_MODE_DEFAULT, ToCss, ParseError, ParsingMode, StyleParseError};
@ -605,24 +606,31 @@ impl ToCss for PropertyDeclarationBlock {
// Step 3.3
let shorthands = declaration.shorthands();
if !shorthands.is_empty() {
// Step 3.3.1
//
// FIXME(emilio): All this looks terribly inefficient...
let mut longhands = self.declarations.iter()
.filter(|d| !already_serialized.contains(d.0.id()))
.collect::<Vec<_>>();
// Step 3.3.1 is done by checking already_serialized while
// iterating below.
// Step 3.3.2
for &shorthand in shorthands {
let properties = shorthand.longhands();
// Substep 2 & 3
let mut current_longhands = Vec::new();
let mut current_longhands = SmallVec::<[_; 10]>::new();
let mut important_count = 0;
let mut found_system = None;
if shorthand == ShorthandId::Font && longhands.iter().any(|&&(ref l, _)| l.get_system().is_some()) {
for &&(ref longhand, longhand_importance) in longhands.iter() {
let is_system_font =
shorthand == ShorthandId::Font &&
self.declarations.iter().any(|&(ref l, _)| {
!already_serialized.contains(l.id()) &&
l.get_system().is_some()
});
if is_system_font {
for &(ref longhand, longhand_importance) in &self.declarations {
if already_serialized.contains(longhand.id()) {
continue;
}
if longhand.get_system().is_some() || longhand.is_default_line_height() {
current_longhands.push(longhand);
if found_system.is_none() {
@ -634,7 +642,11 @@ impl ToCss for PropertyDeclarationBlock {
}
}
} else {
for &&(ref longhand, longhand_importance) in longhands.iter() {
for &(ref longhand, longhand_importance) in &self.declarations {
if already_serialized.contains(longhand.id()) {
continue;
}
if longhand.id().is_longhand_of(shorthand) {
current_longhands.push(longhand);
if longhand_importance.important() {
@ -728,11 +740,6 @@ impl ToCss for PropertyDeclarationBlock {
for current_longhand in &current_longhands {
// Substep 9
already_serialized.insert(current_longhand.id());
let index_to_remove = longhands.iter().position(|l| l.0 == **current_longhand);
if let Some(index) = index_to_remove {
// Substep 10
longhands.remove(index);
}
}
}
}