servo/components/layout/css/matching.rs
bors-servo 36c5dd4c8c Auto merge of #8299 - pcwalton:dont-reflow-on-hover, r=mbrubeck
Fix several bugs causing the page to reflow on every mouse move event

After all these changes are applied, Hacker News and GitHub only repaint and reflow nodes that actually have hover styles applied when the mouse moves over them.

r? @mbrubeck 

cc @bholley

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2015-11-04 06:28:46 +05:30

729 lines
29 KiB
Rust

/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
//! High-level interface to CSS selector matching.
#![allow(unsafe_code)]
use animation;
use context::SharedLayoutContext;
use data::LayoutDataWrapper;
use incremental::{self, RestyleDamage};
use script::dom::bindings::inheritance::{CharacterDataTypeId, NodeTypeId};
use script::layout_interface::Animation;
use selectors::bloom::BloomFilter;
use selectors::matching::{CommonStyleAffectingAttributeMode, CommonStyleAffectingAttributes};
use selectors::matching::{common_style_affecting_attributes, rare_style_affecting_attributes};
use selectors::parser::PseudoElement;
use selectors::{Element};
use smallvec::SmallVec;
use std::borrow::ToOwned;
use std::hash::{Hash, Hasher};
use std::slice::Iter;
use std::sync::Arc;
use std::sync::mpsc::Sender;
use string_cache::{Atom, Namespace};
use style::node::TElementAttributes;
use style::properties::{ComputedValues, PropertyDeclaration, cascade};
use style::selector_matching::{DeclarationBlock, Stylist};
use util::arc_ptr_eq;
use util::cache::{LRUCache, SimpleHashCache};
use util::opts;
use util::vec::ForgetfulSink;
use wrapper::{LayoutElement, LayoutNode};
pub struct ApplicableDeclarations {
pub normal: SmallVec<[DeclarationBlock; 16]>,
pub before: Vec<DeclarationBlock>,
pub after: Vec<DeclarationBlock>,
/// Whether the `normal` declarations are shareable with other nodes.
pub normal_shareable: bool,
}
impl ApplicableDeclarations {
pub fn new() -> ApplicableDeclarations {
ApplicableDeclarations {
normal: SmallVec::new(),
before: Vec::new(),
after: Vec::new(),
normal_shareable: false,
}
}
pub fn clear(&mut self) {
self.normal = SmallVec::new();
self.before = Vec::new();
self.after = Vec::new();
self.normal_shareable = false;
}
}
#[derive(Clone)]
pub struct ApplicableDeclarationsCacheEntry {
pub declarations: Vec<DeclarationBlock>,
}
impl ApplicableDeclarationsCacheEntry {
fn new(declarations: Vec<DeclarationBlock>) -> ApplicableDeclarationsCacheEntry {
ApplicableDeclarationsCacheEntry {
declarations: declarations,
}
}
}
impl PartialEq for ApplicableDeclarationsCacheEntry {
fn eq(&self, other: &ApplicableDeclarationsCacheEntry) -> bool {
let this_as_query = ApplicableDeclarationsCacheQuery::new(&*self.declarations);
this_as_query.eq(other)
}
}
impl Eq for ApplicableDeclarationsCacheEntry {}
impl Hash for ApplicableDeclarationsCacheEntry {
fn hash<H: Hasher>(&self, state: &mut H) {
let tmp = ApplicableDeclarationsCacheQuery::new(&*self.declarations);
tmp.hash(state);
}
}
struct ApplicableDeclarationsCacheQuery<'a> {
declarations: &'a [DeclarationBlock],
}
impl<'a> ApplicableDeclarationsCacheQuery<'a> {
fn new(declarations: &'a [DeclarationBlock]) -> ApplicableDeclarationsCacheQuery<'a> {
ApplicableDeclarationsCacheQuery {
declarations: declarations,
}
}
}
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
}
}
impl<'a> Eq for ApplicableDeclarationsCacheQuery<'a> {}
impl<'a> PartialEq<ApplicableDeclarationsCacheEntry> for ApplicableDeclarationsCacheQuery<'a> {
fn eq(&self, other: &ApplicableDeclarationsCacheEntry) -> bool {
let other_as_query = ApplicableDeclarationsCacheQuery::new(&other.declarations);
self.eq(&other_as_query)
}
}
impl<'a> Hash for ApplicableDeclarationsCacheQuery<'a> {
fn hash<H: Hasher>(&self, state: &mut H) {
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>;
ptr.hash(state);
}
}
}
static APPLICABLE_DECLARATIONS_CACHE_SIZE: usize = 32;
pub struct ApplicableDeclarationsCache {
cache: SimpleHashCache<ApplicableDeclarationsCacheEntry, Arc<ComputedValues>>,
}
impl ApplicableDeclarationsCache {
pub fn new() -> ApplicableDeclarationsCache {
ApplicableDeclarationsCache {
cache: SimpleHashCache::new(APPLICABLE_DECLARATIONS_CACHE_SIZE),
}
}
fn find(&self, declarations: &[DeclarationBlock]) -> Option<Arc<ComputedValues>> {
match self.cache.find(&ApplicableDeclarationsCacheQuery::new(declarations)) {
None => None,
Some(ref values) => Some((*values).clone()),
}
}
fn insert(&mut self, declarations: Vec<DeclarationBlock>, style: Arc<ComputedValues>) {
self.cache.insert(ApplicableDeclarationsCacheEntry::new(declarations), style)
}
pub fn evict_all(&mut self) {
self.cache.evict_all();
}
}
/// An LRU cache of the last few nodes seen, so that we can aggressively try to reuse their styles.
pub struct StyleSharingCandidateCache {
cache: LRUCache<StyleSharingCandidate, ()>,
}
fn create_common_style_affecting_attributes_from_element(element: &LayoutElement)
-> CommonStyleAffectingAttributes {
let mut flags = CommonStyleAffectingAttributes::empty();
for attribute_info in &common_style_affecting_attributes() {
match attribute_info.mode {
CommonStyleAffectingAttributeMode::IsPresent(flag) => {
if element.get_attr(&ns!(""), &attribute_info.atom).is_some() {
flags.insert(flag)
}
}
CommonStyleAffectingAttributeMode::IsEqual(target_value, flag) => {
match element.get_attr(&ns!(""), &attribute_info.atom) {
Some(element_value) if element_value == target_value => {
flags.insert(flag)
}
_ => {}
}
}
}
}
flags
}
#[derive(Clone)]
pub struct StyleSharingCandidate {
pub style: Arc<ComputedValues>,
pub parent_style: Arc<ComputedValues>,
pub local_name: Atom,
// FIXME(pcwalton): Should be a list of atoms instead.
pub class: Option<String>,
pub namespace: Namespace,
pub common_style_affecting_attributes: CommonStyleAffectingAttributes,
pub link: bool,
}
impl PartialEq for StyleSharingCandidate {
fn eq(&self, other: &StyleSharingCandidate) -> bool {
arc_ptr_eq(&self.style, &other.style) &&
arc_ptr_eq(&self.parent_style, &other.parent_style) &&
self.local_name == other.local_name &&
self.class == other.class &&
self.link == other.link &&
self.namespace == other.namespace &&
self.common_style_affecting_attributes == other.common_style_affecting_attributes
}
}
impl StyleSharingCandidate {
/// Attempts to create a style sharing candidate from this node. Returns
/// the style sharing candidate or `None` if this node is ineligible for
/// style sharing.
fn new(element: &LayoutElement) -> Option<StyleSharingCandidate> {
let parent_element = match element.parent_element() {
None => return None,
Some(parent_element) => parent_element,
};
let style = unsafe {
match *element.as_node().borrow_layout_data_unchecked() {
None => return None,
Some(ref layout_data_ref) => {
match layout_data_ref.shared_data.style {
None => return None,
Some(ref data) => (*data).clone(),
}
}
}
};
let parent_style = unsafe {
match *parent_element.as_node().borrow_layout_data_unchecked() {
None => return None,
Some(ref parent_layout_data_ref) => {
match parent_layout_data_ref.shared_data.style {
None => return None,
Some(ref data) => (*data).clone(),
}
}
}
};
if element.style_attribute().is_some() {
return None
}
Some(StyleSharingCandidate {
style: style,
parent_style: parent_style,
local_name: element.get_local_name().clone(),
class: element.get_attr(&ns!(""), &atom!("class"))
.map(|string| string.to_owned()),
link: element.is_link(),
namespace: (*element.get_namespace()).clone(),
common_style_affecting_attributes:
create_common_style_affecting_attributes_from_element(&element)
})
}
fn can_share_style_with(&self, element: &LayoutElement) -> bool {
if *element.get_local_name() != self.local_name {
return false
}
// FIXME(pcwalton): Use `each_class` here instead of slow string comparison.
match (&self.class, element.get_attr(&ns!(""), &atom!("class"))) {
(&None, Some(_)) | (&Some(_), None) => return false,
(&Some(ref this_class), Some(element_class)) if
element_class != &**this_class => {
return false
}
(&Some(_), Some(_)) | (&None, None) => {}
}
if *element.get_namespace() != self.namespace {
return false
}
let mut matching_rules = ForgetfulSink::new();
element.synthesize_presentational_hints_for_legacy_attributes(&mut matching_rules);
if !matching_rules.is_empty() {
return false;
}
// FIXME(pcwalton): It's probably faster to iterate over all the element's attributes and
// use the {common, rare}-style-affecting-attributes tables as lookup tables.
for attribute_info in &common_style_affecting_attributes() {
match attribute_info.mode {
CommonStyleAffectingAttributeMode::IsPresent(flag) => {
if self.common_style_affecting_attributes.contains(flag) !=
element.get_attr(&ns!(""), &attribute_info.atom).is_some() {
return false
}
}
CommonStyleAffectingAttributeMode::IsEqual(target_value, flag) => {
match element.get_attr(&ns!(""), &attribute_info.atom) {
Some(ref element_value) if self.common_style_affecting_attributes
.contains(flag) &&
*element_value != target_value => {
return false
}
Some(_) if !self.common_style_affecting_attributes.contains(flag) => {
return false
}
None if self.common_style_affecting_attributes.contains(flag) => {
return false
}
_ => {}
}
}
}
}
for attribute_name in &rare_style_affecting_attributes() {
if element.get_attr(&ns!(""), attribute_name).is_some() {
return false
}
}
if element.is_link() != self.link {
return false
}
// TODO(pcwalton): We don't support visited links yet, but when we do there will need to
// be some logic here.
true
}
}
static STYLE_SHARING_CANDIDATE_CACHE_SIZE: usize = 40;
impl StyleSharingCandidateCache {
pub fn new() -> StyleSharingCandidateCache {
StyleSharingCandidateCache {
cache: LRUCache::new(STYLE_SHARING_CANDIDATE_CACHE_SIZE),
}
}
pub fn iter(&self) -> Iter<(StyleSharingCandidate, ())> {
self.cache.iter()
}
pub fn insert_if_possible(&mut self, element: &LayoutElement) {
match StyleSharingCandidate::new(element) {
None => {}
Some(candidate) => self.cache.insert(candidate, ())
}
}
pub fn touch(&mut self, index: usize) {
self.cache.touch(index)
}
}
/// The results of attempting to share a style.
pub enum StyleSharingResult {
/// We didn't find anybody to share the style with.
CannotShare,
/// The node's style can be shared. The integer specifies the index in the LRU cache that was
/// hit and the damage that was done.
StyleWasShared(usize, RestyleDamage),
}
pub trait ElementMatchMethods {
fn match_element(&self,
stylist: &Stylist,
parent_bf: Option<&BloomFilter>,
applicable_declarations: &mut ApplicableDeclarations)
-> bool;
/// Attempts to share a style with another node. This method is unsafe because it depends on
/// the `style_sharing_candidate_cache` having only live nodes in it, and we have no way to
/// guarantee that at the type system level yet.
unsafe fn share_style_if_possible(&self,
style_sharing_candidate_cache:
&mut StyleSharingCandidateCache,
parent: Option<LayoutNode>)
-> StyleSharingResult;
}
pub trait MatchMethods {
/// Inserts and removes the matching `Descendant` selectors from a bloom
/// filter. This is used to speed up CSS selector matching to remove
/// unnecessary tree climbs for `Descendant` queries.
///
/// A bloom filter of the local names, namespaces, IDs, and classes is kept.
/// Therefore, each node must have its matching selectors inserted _after_
/// its own selector matching and _before_ its children start.
fn insert_into_bloom_filter(&self, bf: &mut BloomFilter);
/// After all the children are done css selector matching, this must be
/// called to reset the bloom filter after an `insert`.
fn remove_from_bloom_filter(&self, bf: &mut BloomFilter);
unsafe fn cascade_node(&self,
layout_context: &SharedLayoutContext,
parent: Option<LayoutNode>,
applicable_declarations: &ApplicableDeclarations,
applicable_declarations_cache: &mut ApplicableDeclarationsCache,
new_animations_sender: &Sender<Animation>);
}
trait PrivateMatchMethods {
fn cascade_node_pseudo_element(&self,
layout_context: &SharedLayoutContext,
parent_style: Option<&Arc<ComputedValues>>,
applicable_declarations: &[DeclarationBlock],
style: &mut Option<Arc<ComputedValues>>,
applicable_declarations_cache:
&mut ApplicableDeclarationsCache,
new_animations_sender: &Sender<Animation>,
shareable: bool,
animate_properties: bool)
-> RestyleDamage;
}
trait PrivateElementMatchMethods {
fn share_style_with_candidate_if_possible(&self,
parent_node: Option<LayoutNode>,
candidate: &StyleSharingCandidate)
-> Option<Arc<ComputedValues>>;
}
impl<'ln> PrivateMatchMethods for LayoutNode<'ln> {
fn cascade_node_pseudo_element(&self,
layout_context: &SharedLayoutContext,
parent_style: Option<&Arc<ComputedValues>>,
applicable_declarations: &[DeclarationBlock],
style: &mut Option<Arc<ComputedValues>>,
applicable_declarations_cache:
&mut ApplicableDeclarationsCache,
new_animations_sender: &Sender<Animation>,
shareable: bool,
animate_properties: bool)
-> RestyleDamage {
// Finish any transitions.
if animate_properties {
if let Some(ref mut style) = *style {
let this_opaque = self.opaque();
if let Some(ref animations) = layout_context.running_animations.get(&this_opaque) {
for animation in *animations {
animation.property_animation.update(&mut *Arc::make_mut(style), 1.0);
}
}
}
}
let mut this_style;
let cacheable;
match parent_style {
Some(ref parent_style) => {
let cache_entry = applicable_declarations_cache.find(applicable_declarations);
let cached_computed_values = match cache_entry {
None => None,
Some(ref style) => Some(&**style),
};
let (the_style, is_cacheable) = cascade(layout_context.viewport_size,
applicable_declarations,
shareable,
Some(&***parent_style),
cached_computed_values);
cacheable = is_cacheable;
this_style = the_style
}
None => {
let (the_style, is_cacheable) = cascade(layout_context.viewport_size,
applicable_declarations,
shareable,
None,
None);
cacheable = is_cacheable;
this_style = the_style
}
};
// Trigger transitions if necessary. This will reset `this_style` back to its old value if
// it did trigger a transition.
if animate_properties {
if let Some(ref style) = *style {
animation::start_transitions_if_applicable(new_animations_sender,
self.opaque(),
&**style,
&mut this_style);
}
}
// Calculate style difference.
let this_style = Arc::new(this_style);
let damage = incremental::compute_damage(style, &*this_style);
// Cache the resolved style if it was cacheable.
if cacheable {
applicable_declarations_cache.insert(applicable_declarations.to_vec(),
this_style.clone());
}
// Write in the final style and return the damage done to our caller.
*style = Some(this_style);
damage
}
}
impl<'ln> PrivateElementMatchMethods for LayoutElement<'ln> {
fn share_style_with_candidate_if_possible(&self,
parent_node: Option<LayoutNode>,
candidate: &StyleSharingCandidate)
-> Option<Arc<ComputedValues>> {
let parent_node = match parent_node {
Some(ref parent_node) if parent_node.as_element().is_some() => parent_node,
Some(_) | None => return None,
};
let parent_layout_data: &Option<LayoutDataWrapper> = unsafe {
&*parent_node.borrow_layout_data_unchecked()
};
match *parent_layout_data {
Some(ref parent_layout_data_ref) => {
// Check parent style.
let parent_style = parent_layout_data_ref.shared_data.style.as_ref().unwrap();
if !arc_ptr_eq(parent_style, &candidate.parent_style) {
return None
}
// Check tag names, classes, etc.
if !candidate.can_share_style_with(self) {
return None
}
return Some(candidate.style.clone())
}
_ => {}
}
None
}
}
impl<'ln> ElementMatchMethods for LayoutElement<'ln> {
fn match_element(&self,
stylist: &Stylist,
parent_bf: Option<&BloomFilter>,
applicable_declarations: &mut ApplicableDeclarations)
-> bool {
let style_attribute = self.style_attribute().as_ref();
applicable_declarations.normal_shareable =
stylist.push_applicable_declarations(self,
parent_bf,
style_attribute,
None,
&mut applicable_declarations.normal);
stylist.push_applicable_declarations(self,
parent_bf,
None,
Some(PseudoElement::Before),
&mut applicable_declarations.before);
stylist.push_applicable_declarations(self,
parent_bf,
None,
Some(PseudoElement::After),
&mut applicable_declarations.after);
applicable_declarations.normal_shareable &&
applicable_declarations.before.is_empty() &&
applicable_declarations.after.is_empty()
}
unsafe fn share_style_if_possible(&self,
style_sharing_candidate_cache:
&mut StyleSharingCandidateCache,
parent: Option<LayoutNode>)
-> StyleSharingResult {
if opts::get().disable_share_style_cache {
return StyleSharingResult::CannotShare
}
if self.style_attribute().is_some() {
return StyleSharingResult::CannotShare
}
if self.get_attr(&ns!(""), &atom!("id")).is_some() {
return StyleSharingResult::CannotShare
}
for (i, &(ref candidate, ())) in style_sharing_candidate_cache.iter().enumerate() {
match self.share_style_with_candidate_if_possible(parent.clone(), candidate) {
Some(shared_style) => {
// Yay, cache hit. Share the style.
let node = self.as_node();
let mut layout_data_ref = node.mutate_layout_data();
let shared_data = &mut layout_data_ref.as_mut().unwrap().shared_data;
let style = &mut shared_data.style;
let damage = incremental::compute_damage(style, &*shared_style);
*style = Some(shared_style);
return StyleSharingResult::StyleWasShared(i, damage)
}
None => {}
}
}
StyleSharingResult::CannotShare
}
}
impl<'ln> MatchMethods for LayoutNode<'ln> {
// The below two functions are copy+paste because I can't figure out how to
// write a function which takes a generic function. I don't think it can
// be done.
//
// Ideally, I'd want something like:
//
// > fn with_really_simple_selectors(&self, f: <H: Hash>|&H|);
// In terms of `SimpleSelector`s, these two functions will insert and remove:
// - `SimpleSelector::LocalName`
// - `SimpleSelector::Namepace`
// - `SimpleSelector::ID`
// - `SimpleSelector::Class`
fn insert_into_bloom_filter(&self, bf: &mut BloomFilter) {
// Only elements are interesting.
if let Some(element) = self.as_element() {
bf.insert(element.get_local_name());
bf.insert(element.get_namespace());
element.get_id().map(|id| bf.insert(&id));
// TODO: case-sensitivity depends on the document type and quirks mode
element.each_class(|class| bf.insert(class));
}
}
fn remove_from_bloom_filter(&self, bf: &mut BloomFilter) {
// Only elements are interesting.
if let Some(element) = self.as_element() {
bf.remove(element.get_local_name());
bf.remove(element.get_namespace());
element.get_id().map(|id| bf.remove(&id));
// TODO: case-sensitivity depends on the document type and quirks mode
element.each_class(|class| bf.remove(class));
}
}
unsafe fn cascade_node(&self,
layout_context: &SharedLayoutContext,
parent: Option<LayoutNode>,
applicable_declarations: &ApplicableDeclarations,
applicable_declarations_cache: &mut ApplicableDeclarationsCache,
new_animations_sender: &Sender<Animation>) {
// Get our parent's style. This must be unsafe so that we don't touch the parent's
// borrow flags.
//
// FIXME(pcwalton): Isolate this unsafety into the `wrapper` module to allow
// enforced safe, race-free access to the parent style.
let parent_style = match parent {
None => None,
Some(parent_node) => {
let parent_layout_data_ref = parent_node.borrow_layout_data_unchecked();
let parent_layout_data = (&*parent_layout_data_ref).as_ref()
.expect("no parent data!?");
let parent_style = parent_layout_data.shared_data
.style
.as_ref()
.expect("parent hasn't been styled yet!");
Some(parent_style)
}
};
let mut layout_data_ref = self.mutate_layout_data();
match *layout_data_ref {
None => panic!("no layout data"),
Some(ref mut layout_data) => {
match self.type_id() {
NodeTypeId::CharacterData(CharacterDataTypeId::Text) => {
// Text nodes get a copy of the parent style. This ensures
// that during fragment construction any non-inherited
// CSS properties (such as vertical-align) are correctly
// set on the fragment(s).
let cloned_parent_style = parent_style.unwrap().clone();
layout_data.shared_data.style = Some(cloned_parent_style);
}
_ => {
let mut damage = self.cascade_node_pseudo_element(
layout_context,
parent_style,
&applicable_declarations.normal,
&mut layout_data.shared_data.style,
applicable_declarations_cache,
new_animations_sender,
applicable_declarations.normal_shareable,
true);
if applicable_declarations.before.len() > 0 {
damage = damage | self.cascade_node_pseudo_element(
layout_context,
Some(layout_data.shared_data.style.as_ref().unwrap()),
&*applicable_declarations.before,
&mut layout_data.data.before_style,
applicable_declarations_cache,
new_animations_sender,
false,
false);
}
if applicable_declarations.after.len() > 0 {
damage = damage | self.cascade_node_pseudo_element(
layout_context,
Some(layout_data.shared_data.style.as_ref().unwrap()),
&*applicable_declarations.after,
&mut layout_data.data.after_style,
applicable_declarations_cache,
new_animations_sender,
false,
false);
}
layout_data.data.restyle_damage = damage;
}
}
}
}
}
}