servo/components/style/invalidation/element/invalidator.rs
Emilio Cobos Álvarez 665690bba6
style: Hook in the document invalidator.
Bug: 1409672
Reviewed-by: xidorn
MozReview-Commit-ID: EoSMrYPS7dl
2018-01-17 18:03:16 +01:00

871 lines
32 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/. */
//! The struct that takes care of encapsulating all the logic on where and how
//! element styles need to be invalidated.
use context::StackLimitChecker;
use dom::{TElement, TNode};
use selector_parser::SelectorImpl;
use selectors::matching::{CompoundSelectorMatchingResult, MatchingContext};
use selectors::matching::matches_compound_selector_from;
use selectors::parser::{Combinator, Component, Selector};
use smallvec::SmallVec;
use std::fmt;
/// A trait to abstract the collection of invalidations for a given pass.
pub trait InvalidationProcessor<'a, E>
where
E: TElement,
{
/// Whether an invalidation that contains only an eager pseudo-element
/// selector like ::before or ::after triggers invalidation of the element
/// that would originate it.
fn invalidates_on_eager_pseudo_element(&self) -> bool { false }
/// Whether the invalidation processor only cares about light-tree
/// descendants of a given element, that is, doesn't invalidate
/// pseudo-elements, NAC, or XBL anon content.
fn light_tree_only(&self) -> bool { false }
/// The matching context that should be used to process invalidations.
fn matching_context(&mut self) -> &mut MatchingContext<'a, E::Impl>;
/// Collect invalidations for a given element's descendants and siblings.
///
/// Returns whether the element itself was invalidated.
fn collect_invalidations(
&mut self,
element: E,
self_invalidations: &mut InvalidationVector<'a>,
descendant_invalidations: &mut DescendantInvalidationLists<'a>,
sibling_invalidations: &mut InvalidationVector<'a>,
) -> bool;
/// Returns whether the invalidation process should process the descendants
/// of the given element.
fn should_process_descendants(&mut self, element: E) -> bool;
/// Executes an arbitrary action when the recursion limit is exceded (if
/// any).
fn recursion_limit_exceeded(&mut self, element: E);
/// Executes an action when `Self` is invalidated.
fn invalidated_self(&mut self, element: E);
/// Executes an action when any descendant of `Self` is invalidated.
fn invalidated_descendants(&mut self, element: E, child: E);
}
/// Different invalidation lists for descendants.
#[derive(Debug, Default)]
pub struct DescendantInvalidationLists<'a> {
/// Invalidations for normal DOM children and pseudo-elements.
///
/// TODO(emilio): Having a list of invalidations just for pseudo-elements
/// may save some work here and there.
pub dom_descendants: InvalidationVector<'a>,
/// Invalidations for slotted children of an element.
pub slotted_descendants: InvalidationVector<'a>,
}
impl<'a> DescendantInvalidationLists<'a> {
fn is_empty(&self) -> bool {
self.dom_descendants.is_empty() &&
self.slotted_descendants.is_empty()
}
}
/// The struct that takes care of encapsulating all the logic on where and how
/// element styles need to be invalidated.
pub struct TreeStyleInvalidator<'a, 'b, E, P: 'a>
where
'b: 'a,
E: TElement,
P: InvalidationProcessor<'b, E>,
{
element: E,
stack_limit_checker: Option<&'a StackLimitChecker>,
processor: &'a mut P,
_marker: ::std::marker::PhantomData<&'b ()>
}
/// A vector of invalidations, optimized for small invalidation sets.
pub type InvalidationVector<'a> = SmallVec<[Invalidation<'a>; 10]>;
/// The kind of descendant invalidation we're processing.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
enum DescendantInvalidationKind {
/// A DOM descendant invalidation.
Dom,
/// A ::slotted() descendant invalidation.
Slotted,
}
/// The kind of invalidation we're processing.
///
/// We can use this to avoid pushing invalidations of the same kind to our
/// descendants or siblings.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
enum InvalidationKind {
Descendant(DescendantInvalidationKind),
Sibling,
}
/// An `Invalidation` is a complex selector that describes which elements,
/// relative to a current element we are processing, must be restyled.
#[derive(Clone)]
pub struct Invalidation<'a> {
selector: &'a Selector<SelectorImpl>,
/// The offset of the selector pointing to a compound selector.
///
/// This order is a "parse order" offset, that is, zero is the leftmost part
/// of the selector written as parsed / serialized.
offset: usize,
/// Whether the invalidation was already matched by any previous sibling or
/// ancestor.
///
/// If this is the case, we can avoid pushing invalidations generated by
/// this one if the generated invalidation is effective for all the siblings
/// or descendants after us.
matched_by_any_previous: bool,
}
impl<'a> Invalidation<'a> {
/// Create a new invalidation for a given selector and offset.
pub fn new(selector: &'a Selector<SelectorImpl>, offset: usize) -> Self {
Self {
selector,
offset,
matched_by_any_previous: false,
}
}
/// Whether this invalidation is effective for the next sibling or
/// descendant after us.
fn effective_for_next(&self) -> bool {
if self.offset == 0 {
return true;
}
// TODO(emilio): For pseudo-elements this should be mostly false, except
// for the weird pseudos in <input type="number">.
//
// We should be able to do better here!
match self.selector.combinator_at_parse_order(self.offset - 1) {
Combinator::Descendant |
Combinator::LaterSibling |
Combinator::PseudoElement => true,
Combinator::SlotAssignment |
Combinator::NextSibling |
Combinator::Child => false,
}
}
fn kind(&self) -> InvalidationKind {
if self.offset == 0 {
return InvalidationKind::Descendant(DescendantInvalidationKind::Dom);
}
match self.selector.combinator_at_parse_order(self.offset - 1) {
Combinator::Child |
Combinator::Descendant |
Combinator::PseudoElement => InvalidationKind::Descendant(DescendantInvalidationKind::Dom),
Combinator::SlotAssignment => InvalidationKind::Descendant(DescendantInvalidationKind::Slotted),
Combinator::NextSibling |
Combinator::LaterSibling => InvalidationKind::Sibling,
}
}
}
impl<'a> fmt::Debug for Invalidation<'a> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
use cssparser::ToCss;
f.write_str("Invalidation(")?;
for component in self.selector.iter_raw_parse_order_from(self.offset) {
if matches!(*component, Component::Combinator(..)) {
break;
}
component.to_css(f)?;
}
f.write_str(")")
}
}
/// The result of processing a single invalidation for a given element.
struct SingleInvalidationResult {
/// Whether the element itself was invalidated.
invalidated_self: bool,
/// Whether the invalidation matched, either invalidating the element or
/// generating another invalidation.
matched: bool,
}
/// The result of a whole invalidation process for a given element.
pub struct InvalidationResult {
/// Whether the element itself was invalidated.
invalidated_self: bool,
/// Whether the element's descendants were invalidated.
invalidated_descendants: bool,
/// Whether the element's siblings were invalidated.
invalidated_siblings: bool,
}
impl InvalidationResult {
/// Create an emtpy result.
pub fn empty() -> Self {
Self {
invalidated_self: false,
invalidated_descendants: false,
invalidated_siblings: false,
}
}
/// Whether the invalidation has invalidate the element itself.
pub fn has_invalidated_self(&self) -> bool {
self.invalidated_self
}
/// Whether the invalidation has invalidate desendants.
pub fn has_invalidated_descendants(&self) -> bool {
self.invalidated_descendants
}
/// Whether the invalidation has invalidate siblings.
pub fn has_invalidated_siblings(&self) -> bool {
self.invalidated_siblings
}
}
impl<'a, 'b, E, P: 'a> TreeStyleInvalidator<'a, 'b, E, P>
where
'b: 'a,
E: TElement,
P: InvalidationProcessor<'b, E>,
{
/// Trivially constructs a new `TreeStyleInvalidator`.
pub fn new(
element: E,
stack_limit_checker: Option<&'a StackLimitChecker>,
processor: &'a mut P,
) -> Self {
Self {
element,
stack_limit_checker,
processor,
_marker: ::std::marker::PhantomData,
}
}
/// Perform the invalidation pass.
pub fn invalidate(mut self) -> InvalidationResult {
debug!("StyleTreeInvalidator::invalidate({:?})", self.element);
let mut self_invalidations = InvalidationVector::new();
let mut descendant_invalidations = DescendantInvalidationLists::default();
let mut sibling_invalidations = InvalidationVector::new();
let mut invalidated_self = self.processor.collect_invalidations(
self.element,
&mut self_invalidations,
&mut descendant_invalidations,
&mut sibling_invalidations,
);
debug!("Collected invalidations (self: {}): ", invalidated_self);
debug!(" > self: {}, {:?}", self_invalidations.len(), self_invalidations);
debug!(" > descendants: {:?}", descendant_invalidations);
debug!(" > siblings: {}, {:?}", sibling_invalidations.len(), sibling_invalidations);
let invalidated_self_from_collection = invalidated_self;
invalidated_self |= self.process_descendant_invalidations(
&self_invalidations,
&mut descendant_invalidations,
&mut sibling_invalidations,
DescendantInvalidationKind::Dom,
);
if invalidated_self && !invalidated_self_from_collection {
self.processor.invalidated_self(self.element);
}
let invalidated_descendants = self.invalidate_descendants(&descendant_invalidations);
let invalidated_siblings = self.invalidate_siblings(&mut sibling_invalidations);
InvalidationResult {
invalidated_self,
invalidated_descendants,
invalidated_siblings,
}
}
/// Go through later DOM siblings, invalidating style as needed using the
/// `sibling_invalidations` list.
///
/// Returns whether any sibling's style or any sibling descendant's style
/// was invalidated.
fn invalidate_siblings(
&mut self,
sibling_invalidations: &mut InvalidationVector<'b>,
) -> bool {
if sibling_invalidations.is_empty() {
return false;
}
let mut current = self.element.next_sibling_element();
let mut any_invalidated = false;
while let Some(sibling) = current {
let mut sibling_invalidator = TreeStyleInvalidator::new(
sibling,
self.stack_limit_checker,
self.processor,
);
let mut invalidations_for_descendants =
DescendantInvalidationLists::default();
let invalidated_sibling =
sibling_invalidator.process_sibling_invalidations(
&mut invalidations_for_descendants,
sibling_invalidations,
);
if invalidated_sibling {
sibling_invalidator.processor.invalidated_self(sibling);
}
any_invalidated |= invalidated_sibling;
any_invalidated |=
sibling_invalidator.invalidate_descendants(
&invalidations_for_descendants,
);
if sibling_invalidations.is_empty() {
break;
}
current = sibling.next_sibling_element();
}
any_invalidated
}
fn invalidate_pseudo_element_or_nac(
&mut self,
child: E,
invalidations: &[Invalidation<'b>],
) -> bool {
let mut sibling_invalidations = InvalidationVector::new();
let result = self.invalidate_child(
child,
invalidations,
&mut sibling_invalidations,
DescendantInvalidationKind::Dom,
);
// Roots of NAC subtrees can indeed generate sibling invalidations, but
// they can be just ignored, since they have no siblings.
//
// Note that we can end up testing selectors that wouldn't end up
// matching due to this being NAC, like those coming from document
// rules, but we overinvalidate instead of checking this.
result
}
/// Invalidate a child and recurse down invalidating its descendants if
/// needed.
fn invalidate_child(
&mut self,
child: E,
invalidations: &[Invalidation<'b>],
sibling_invalidations: &mut InvalidationVector<'b>,
descendant_invalidation_kind: DescendantInvalidationKind,
) -> bool {
let mut invalidations_for_descendants =
DescendantInvalidationLists::default();
let mut invalidated_child = false;
let invalidated_descendants = {
let mut child_invalidator = TreeStyleInvalidator::new(
child,
self.stack_limit_checker,
self.processor,
);
invalidated_child |=
child_invalidator.process_sibling_invalidations(
&mut invalidations_for_descendants,
sibling_invalidations,
);
invalidated_child |=
child_invalidator.process_descendant_invalidations(
invalidations,
&mut invalidations_for_descendants,
sibling_invalidations,
descendant_invalidation_kind,
);
if invalidated_child {
child_invalidator.processor.invalidated_self(child);
}
child_invalidator.invalidate_descendants(
&invalidations_for_descendants,
)
};
// The child may not be a flattened tree child of the current element,
// but may be arbitrarily deep.
//
// Since we keep the traversal flags in terms of the flattened tree,
// we need to propagate it as appropriate.
if invalidated_child || invalidated_descendants {
self.processor.invalidated_descendants(self.element, child);
}
invalidated_child || invalidated_descendants
}
fn invalidate_nac(
&mut self,
invalidations: &[Invalidation<'b>],
) -> bool {
let mut any_nac_root = false;
let element = self.element;
element.each_anonymous_content_child(|nac| {
any_nac_root |=
self.invalidate_pseudo_element_or_nac(nac, invalidations);
});
any_nac_root
}
// NB: It's important that this operates on DOM children, which is what
// selector-matching operates on.
fn invalidate_dom_descendants_of(
&mut self,
parent: E::ConcreteNode,
invalidations: &[Invalidation<'b>],
) -> bool {
let mut any_descendant = false;
let mut sibling_invalidations = InvalidationVector::new();
for child in parent.dom_children() {
// TODO(emilio): We handle <xbl:children> fine, because they appear
// in selector-matching (note bug 1374247, though).
//
// This probably needs a shadow root check on `child` here, and
// recursing if that's the case.
let child = match child.as_element() {
Some(e) => e,
None => continue,
};
any_descendant |= self.invalidate_child(
child,
invalidations,
&mut sibling_invalidations,
DescendantInvalidationKind::Dom,
);
}
any_descendant
}
fn invalidate_slotted_elements(
&mut self,
invalidations: &[Invalidation<'b>],
) -> bool {
if invalidations.is_empty() {
return false;
}
let mut any = false;
let mut sibling_invalidations = InvalidationVector::new();
let element = self.element;
for node in element.slotted_nodes() {
let element = match node.as_element() {
Some(e) => e,
None => continue,
};
any |= self.invalidate_child(
element,
invalidations,
&mut sibling_invalidations,
DescendantInvalidationKind::Slotted,
);
// FIXME(emilio): Need to handle nested slotted nodes if `element`
// is itself a <slot>.
debug_assert!(
sibling_invalidations.is_empty(),
"::slotted() shouldn't have sibling combinators to the right, \
this makes no sense! {:?}",
sibling_invalidations
);
}
any
}
fn invalidate_non_slotted_descendants(
&mut self,
invalidations: &[Invalidation<'b>],
) -> bool {
if invalidations.is_empty() {
return false;
}
if self.processor.light_tree_only() {
let node = self.element.as_node();
return self.invalidate_dom_descendants_of(node, invalidations);
}
let mut any_descendant = false;
// NOTE(emilio): This should not be needed for Shadow DOM for normal
// element state / attribute invalidations (it's needed for XBL though,
// due to the weird way the anon content there works (it doesn't block
// combinators)).
//
// However, it's needed as of right now for document state invalidation,
// were we rely on iterating every element that ends up in the composed
// doc.
//
// Also, we could avoid having that special-case for document state
// invalidations if we invalidate for document state changes per
// subtree, though that's kind of annoying because we need to invalidate
// the shadow host subtree (to handle :host and ::slotted), and the
// actual shadow tree (to handle all other rules in the ShadowRoot).
if let Some(anon_content) = self.element.xbl_binding_anonymous_content() {
any_descendant |=
self.invalidate_dom_descendants_of(anon_content, invalidations);
}
if let Some(before) = self.element.before_pseudo_element() {
any_descendant |=
self.invalidate_pseudo_element_or_nac(before, invalidations);
}
let node = self.element.as_node();
any_descendant |=
self.invalidate_dom_descendants_of(node, invalidations);
if let Some(after) = self.element.after_pseudo_element() {
any_descendant |=
self.invalidate_pseudo_element_or_nac(after, invalidations);
}
any_descendant |= self.invalidate_nac(invalidations);
any_descendant
}
/// Given the descendant invalidation lists, go through the current
/// element's descendants, and invalidate style on them.
fn invalidate_descendants(
&mut self,
invalidations: &DescendantInvalidationLists<'b>,
) -> bool {
if invalidations.is_empty() {
return false;
}
debug!("StyleTreeInvalidator::invalidate_descendants({:?})",
self.element);
debug!(" > {:?}", invalidations);
let should_process =
self.processor.should_process_descendants(self.element);
if !should_process {
return false;
}
if let Some(checker) = self.stack_limit_checker {
if checker.limit_exceeded() {
self.processor.recursion_limit_exceeded(self.element);
return true;
}
}
let mut any_descendant = false;
any_descendant |=
self.invalidate_non_slotted_descendants(&invalidations.dom_descendants);
any_descendant |=
self.invalidate_slotted_elements(&invalidations.slotted_descendants);
any_descendant
}
/// Process the given sibling invalidations coming from our previous
/// sibling.
///
/// The sibling invalidations are somewhat special because they can be
/// modified on the fly. New invalidations may be added and removed.
///
/// In particular, all descendants get the same set of invalidations from
/// the parent, but the invalidations from a given sibling depend on the
/// ones we got from the previous one.
///
/// Returns whether invalidated the current element's style.
fn process_sibling_invalidations(
&mut self,
descendant_invalidations: &mut DescendantInvalidationLists<'b>,
sibling_invalidations: &mut InvalidationVector<'b>,
) -> bool {
let mut i = 0;
let mut new_sibling_invalidations = InvalidationVector::new();
let mut invalidated_self = false;
while i < sibling_invalidations.len() {
let result = self.process_invalidation(
&sibling_invalidations[i],
descendant_invalidations,
&mut new_sibling_invalidations,
InvalidationKind::Sibling,
);
invalidated_self |= result.invalidated_self;
sibling_invalidations[i].matched_by_any_previous |= result.matched;
if sibling_invalidations[i].effective_for_next() {
i += 1;
} else {
sibling_invalidations.remove(i);
}
}
sibling_invalidations.extend(new_sibling_invalidations.drain());
invalidated_self
}
/// Process a given invalidation list coming from our parent,
/// adding to `descendant_invalidations` and `sibling_invalidations` as
/// needed.
///
/// Returns whether our style was invalidated as a result.
fn process_descendant_invalidations(
&mut self,
invalidations: &[Invalidation<'b>],
descendant_invalidations: &mut DescendantInvalidationLists<'b>,
sibling_invalidations: &mut InvalidationVector<'b>,
descendant_invalidation_kind: DescendantInvalidationKind,
) -> bool {
let mut invalidated = false;
for invalidation in invalidations {
let result = self.process_invalidation(
invalidation,
descendant_invalidations,
sibling_invalidations,
InvalidationKind::Descendant(descendant_invalidation_kind),
);
invalidated |= result.invalidated_self;
if invalidation.effective_for_next() {
let mut invalidation = invalidation.clone();
invalidation.matched_by_any_previous |= result.matched;
debug_assert_eq!(
descendant_invalidation_kind,
DescendantInvalidationKind::Dom,
"Slotted invalidations don't propagate."
);
descendant_invalidations.dom_descendants.push(invalidation);
}
}
invalidated
}
/// Processes a given invalidation, potentially invalidating the style of
/// the current element.
///
/// Returns whether invalidated the style of the element, and whether the
/// invalidation should be effective to subsequent siblings or descendants
/// down in the tree.
fn process_invalidation(
&mut self,
invalidation: &Invalidation<'b>,
descendant_invalidations: &mut DescendantInvalidationLists<'b>,
sibling_invalidations: &mut InvalidationVector<'b>,
invalidation_kind: InvalidationKind,
) -> SingleInvalidationResult {
debug!("TreeStyleInvalidator::process_invalidation({:?}, {:?}, {:?})",
self.element, invalidation, invalidation_kind);
let matching_result = matches_compound_selector_from(
&invalidation.selector,
invalidation.offset,
self.processor.matching_context(),
&self.element
);
let mut invalidated_self = false;
let mut matched = false;
match matching_result {
CompoundSelectorMatchingResult::FullyMatched => {
debug!(" > Invalidation matched completely");
matched = true;
invalidated_self = true;
}
CompoundSelectorMatchingResult::Matched { next_combinator_offset } => {
let next_combinator =
invalidation.selector.combinator_at_parse_order(next_combinator_offset);
matched = true;
if matches!(next_combinator, Combinator::PseudoElement) {
// This will usually be the very next component, except for
// the fact that we store compound selectors the other way
// around, so there could also be state pseudo-classes.
let pseudo_selector =
invalidation.selector
.iter_raw_parse_order_from(next_combinator_offset + 1)
.skip_while(|c| matches!(**c, Component::NonTSPseudoClass(..)))
.next()
.unwrap();
let pseudo = match *pseudo_selector {
Component::PseudoElement(ref pseudo) => pseudo,
_ => {
unreachable!(
"Someone seriously messed up selector parsing: \
{:?} at offset {:?}: {:?}",
invalidation.selector,
next_combinator_offset,
pseudo_selector,
)
}
};
// FIXME(emilio): This is not ideal, and could not be
// accurate if we ever have stateful element-backed eager
// pseudos.
//
// Ideally, we'd just remove element-backed eager pseudos
// altogether, given they work fine without it. Only gotcha
// is that we wouldn't style them in parallel, which may or
// may not be an issue.
//
// Also, this could be more fine grained now (perhaps a
// RESTYLE_PSEUDOS hint?).
//
// Note that we'll also restyle the pseudo-element because
// it would match this invalidation.
if self.processor.invalidates_on_eager_pseudo_element() &&
pseudo.is_eager() {
invalidated_self = true;
}
}
let next_invalidation = Invalidation {
selector: invalidation.selector,
offset: next_combinator_offset + 1,
matched_by_any_previous: false,
};
debug!(" > Invalidation matched, next: {:?}, ({:?})",
next_invalidation, next_combinator);
let next_invalidation_kind = next_invalidation.kind();
// We can skip pushing under some circumstances, and we should
// because otherwise the invalidation list could grow
// exponentially.
//
// * First of all, both invalidations need to be of the same
// kind. This is because of how we propagate them going to
// the right of the tree for sibling invalidations and going
// down the tree for children invalidations. A sibling
// invalidation that ends up generating a children
// invalidation ends up (correctly) in five different lists,
// not in the same list five different times.
//
// * Then, the invalidation needs to be matched by a previous
// ancestor/sibling, in order to know that this invalidation
// has been generated already.
//
// * Finally, the new invalidation needs to be
// `effective_for_next()`, in order for us to know that it is
// still in the list, since we remove the dependencies that
// aren't from the lists for our children / siblings.
//
// To go through an example, let's imagine we are processing a
// dom subtree like:
//
// <div><address><div><div/></div></address></div>
//
// And an invalidation list with a single invalidation like:
//
// [div div div]
//
// When we process the invalidation list for the outer div, we
// match it, and generate a `div div` invalidation, so for the
// <address> child we have:
//
// [div div div, div div]
//
// With the first of them marked as `matched`.
//
// When we process the <address> child, we don't match any of
// them, so both invalidations go untouched to our children.
//
// When we process the second <div>, we match _both_
// invalidations.
//
// However, when matching the first, we can tell it's been
// matched, and not push the corresponding `div div`
// invalidation, since we know it's necessarily already on the
// list.
//
// Thus, without skipping the push, we'll arrive to the
// innermost <div> with:
//
// [div div div, div div, div div, div]
//
// While skipping it, we won't arrive here with duplicating
// dependencies:
//
// [div div div, div div, div]
//
let can_skip_pushing =
next_invalidation_kind == invalidation_kind &&
invalidation.matched_by_any_previous &&
next_invalidation.effective_for_next();
if can_skip_pushing {
debug!(" > Can avoid push, since the invalidation had \
already been matched before");
} else {
match next_invalidation_kind {
InvalidationKind::Descendant(DescendantInvalidationKind::Dom) => {
descendant_invalidations.dom_descendants.push(next_invalidation);
}
InvalidationKind::Descendant(DescendantInvalidationKind::Slotted) => {
descendant_invalidations.slotted_descendants.push(next_invalidation);
}
InvalidationKind::Sibling => {
sibling_invalidations.push(next_invalidation);
}
}
}
}
CompoundSelectorMatchingResult::NotMatched => {}
}
SingleInvalidationResult { invalidated_self, matched, }
}
}