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/* 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
//! The context within which style is calculated.
#[cfg(feature = "servo")]
use crate::animation::DocumentAnimationSet;
use crate::bloom::StyleBloom;
use crate::computed_value_flags::ComputedValueFlags;
use crate::data::{EagerPseudoStyles, ElementData};
use crate::dom::{SendElement, TElement};
#[cfg(feature = "gecko")]
use crate::gecko_bindings::structs;
use crate::parallel::{STACK_SAFETY_MARGIN_KB, STYLE_THREAD_STACK_SIZE_KB};
use crate::properties::ComputedValues;
#[cfg(feature = "servo")]
use crate::properties::PropertyId;
use crate::rule_cache::RuleCache;
use crate::rule_tree::StrongRuleNode;
use crate::selector_parser::{SnapshotMap, EAGER_PSEUDO_COUNT};
use crate::shared_lock::StylesheetGuards;
use crate::sharing::StyleSharingCache;
use crate::stylist::Stylist;
use crate::thread_state::{self, ThreadState};
use crate::traversal::DomTraversal;
use crate::traversal_flags::TraversalFlags;
use app_units::Au;
use euclid::default::Size2D;
use euclid::Scale;
#[cfg(feature = "servo")]
use fxhash::FxHashMap;
use selectors::context::SelectorCaches;
#[cfg(feature = "gecko")]
use servo_arc::Arc;
#[cfg(feature = "servo")]
use servo_atoms::Atom;
use std::fmt;
use std::ops;
use std::time::{Duration, Instant};
use style_traits::CSSPixel;
use style_traits::DevicePixel;
#[cfg(feature = "servo")]
use style_traits::SpeculativePainter;
pub use selectors::matching::QuirksMode;
/// A global options structure for the style system. We use this instead of
/// opts to abstract across Gecko and Servo.
#[derive(Clone)]
pub struct StyleSystemOptions {
/// Whether the style sharing cache is disabled.
pub disable_style_sharing_cache: bool,
/// Whether we should dump statistics about the style system.
pub dump_style_statistics: bool,
/// The minimum number of elements that must be traversed to trigger a dump
/// of style statistics.
pub style_statistics_threshold: usize,
}
#[cfg(feature = "gecko")]
fn get_env_bool(name: &str) -> bool {
use std::env;
match env::var(name) {
Ok(s) => !s.is_empty(),
Err(_) => false,
}
}
const DEFAULT_STATISTICS_THRESHOLD: usize = 50;
#[cfg(feature = "gecko")]
fn get_env_usize(name: &str) -> Option<usize> {
use std::env;
env::var(name).ok().map(|s| {
s.parse::<usize>()
.expect("Couldn't parse environmental variable as usize")
})
}
/// A global variable holding the state of
/// `StyleSystemOptions::default().disable_style_sharing_cache`.
#[cfg(feature = "servo")]
pub static DEFAULT_DISABLE_STYLE_SHARING_CACHE: std::sync::atomic::AtomicBool =
std::sync::atomic::AtomicBool::new(false);
/// A global variable holding the state of
/// `StyleSystemOptions::default().dump_style_statistics`.
#[cfg(feature = "servo")]
pub static DEFAULT_DUMP_STYLE_STATISTICS: std::sync::atomic::AtomicBool =
std::sync::atomic::AtomicBool::new(false);
impl Default for StyleSystemOptions {
#[cfg(feature = "servo")]
fn default() -> Self {
use std::sync::atomic::Ordering;
StyleSystemOptions {
disable_style_sharing_cache: DEFAULT_DISABLE_STYLE_SHARING_CACHE
.load(Ordering::Relaxed),
dump_style_statistics: DEFAULT_DUMP_STYLE_STATISTICS.load(Ordering::Relaxed),
style_statistics_threshold: DEFAULT_STATISTICS_THRESHOLD,
}
}
#[cfg(feature = "gecko")]
fn default() -> Self {
StyleSystemOptions {
disable_style_sharing_cache: get_env_bool("DISABLE_STYLE_SHARING_CACHE"),
dump_style_statistics: get_env_bool("DUMP_STYLE_STATISTICS"),
style_statistics_threshold: get_env_usize("STYLE_STATISTICS_THRESHOLD")
.unwrap_or(DEFAULT_STATISTICS_THRESHOLD),
}
}
}
/// A shared style context.
///
/// There's exactly one of these during a given restyle traversal, and it's
/// shared among the worker threads.
pub struct SharedStyleContext<'a> {
/// The CSS selector stylist.
pub stylist: &'a Stylist,
/// Whether visited styles are enabled.
///
/// They may be disabled when Gecko's pref layout.css.visited_links_enabled
/// is false, or when in private browsing mode.
pub visited_styles_enabled: bool,
/// Configuration options.
pub options: StyleSystemOptions,
/// Guards for pre-acquired locks
pub guards: StylesheetGuards<'a>,
/// The current time for transitions and animations. This is needed to ensure
/// a consistent sampling time and also to adjust the time for testing.
pub current_time_for_animations: f64,
/// Flags controlling how we traverse the tree.
pub traversal_flags: TraversalFlags,
/// A map with our snapshots in order to handle restyle hints.
pub snapshot_map: &'a SnapshotMap,
/// The state of all animations for our styled elements.
#[cfg(feature = "servo")]
pub animations: DocumentAnimationSet,
/// Paint worklets
#[cfg(feature = "servo")]
pub registered_speculative_painters: &'a dyn RegisteredSpeculativePainters,
}
impl<'a> SharedStyleContext<'a> {
/// Return a suitable viewport size in order to be used for viewport units.
pub fn viewport_size(&self) -> Size2D<Au> {
self.stylist.device().au_viewport_size()
}
/// The device pixel ratio
pub fn device_pixel_ratio(&self) -> Scale<f32, CSSPixel, DevicePixel> {
self.stylist.device().device_pixel_ratio()
}
/// The quirks mode of the document.
pub fn quirks_mode(&self) -> QuirksMode {
self.stylist.quirks_mode()
}
}
/// The structure holds various intermediate inputs that are eventually used by
/// by the cascade.
///
/// The matching and cascading process stores them in this format temporarily
/// within the `CurrentElementInfo`. At the end of the cascade, they are folded
/// down into the main `ComputedValues` to reduce memory usage per element while
/// still remaining accessible.
#[derive(Clone, Debug, Default)]
pub struct CascadeInputs {
/// The rule node representing the ordered list of rules matched for this
/// node.
pub rules: Option<StrongRuleNode>,
/// The rule node representing the ordered list of rules matched for this
/// node if visited, only computed if there's a relevant link for this
/// element. A element's "relevant link" is the element being matched if it
/// is a link or the nearest ancestor link.
pub visited_rules: Option<StrongRuleNode>,
/// The set of flags from container queries that we need for invalidation.
pub flags: ComputedValueFlags,
}
impl CascadeInputs {
/// Construct inputs from previous cascade results, if any.
pub fn new_from_style(style: &ComputedValues) -> Self {
Self {
rules: style.rules.clone(),
visited_rules: style.visited_style().and_then(|v| v.rules.clone()),
flags: style.flags.for_cascade_inputs(),
}
}
}
/// A list of cascade inputs for eagerly-cascaded pseudo-elements.
/// The list is stored inline.
#[derive(Debug)]
pub struct EagerPseudoCascadeInputs(Option<[Option<CascadeInputs>; EAGER_PSEUDO_COUNT]>);
// Manually implement `Clone` here because the derived impl of `Clone` for
// array types assumes the value inside is `Copy`.
impl Clone for EagerPseudoCascadeInputs {
fn clone(&self) -> Self {
if self.0.is_none() {
return EagerPseudoCascadeInputs(None);
}
let self_inputs = self.0.as_ref().unwrap();
let mut inputs: [Option<CascadeInputs>; EAGER_PSEUDO_COUNT] = Default::default();
for i in 0..EAGER_PSEUDO_COUNT {
inputs[i] = self_inputs[i].clone();
}
EagerPseudoCascadeInputs(Some(inputs))
}
}
impl EagerPseudoCascadeInputs {
/// Construct inputs from previous cascade results, if any.
fn new_from_style(styles: &EagerPseudoStyles) -> Self {
EagerPseudoCascadeInputs(styles.as_optional_array().map(|styles| {
let mut inputs: [Option<CascadeInputs>; EAGER_PSEUDO_COUNT] = Default::default();
for i in 0..EAGER_PSEUDO_COUNT {
inputs[i] = styles[i].as_ref().map(|s| CascadeInputs::new_from_style(s));
}
inputs
}))
}
/// Returns the list of rules, if they exist.
pub fn into_array(self) -> Option<[Option<CascadeInputs>; EAGER_PSEUDO_COUNT]> {
self.0
}
}
/// The cascade inputs associated with a node, including those for any
/// pseudo-elements.
///
/// The matching and cascading process stores them in this format temporarily
/// within the `CurrentElementInfo`. At the end of the cascade, they are folded
/// down into the main `ComputedValues` to reduce memory usage per element while
/// still remaining accessible.
#[derive(Clone, Debug)]
pub struct ElementCascadeInputs {
/// The element's cascade inputs.
pub primary: CascadeInputs,
/// A list of the inputs for the element's eagerly-cascaded pseudo-elements.
pub pseudos: EagerPseudoCascadeInputs,
}
impl ElementCascadeInputs {
/// Construct inputs from previous cascade results, if any.
#[inline]
pub fn new_from_element_data(data: &ElementData) -> Self {
debug_assert!(data.has_styles());
ElementCascadeInputs {
primary: CascadeInputs::new_from_style(data.styles.primary()),
pseudos: EagerPseudoCascadeInputs::new_from_style(&data.styles.pseudos),
}
}
}
/// Statistics gathered during the traversal. We gather statistics on each
/// thread and then combine them after the threads join via the Add
/// implementation below.
#[derive(AddAssign, Clone, Default)]
pub struct PerThreadTraversalStatistics {
/// The total number of elements traversed.
pub elements_traversed: u32,
/// The number of elements where has_styles() went from false to true.
pub elements_styled: u32,
/// The number of elements for which we performed selector matching.
pub elements_matched: u32,
/// The number of cache hits from the StyleSharingCache.
pub styles_shared: u32,
/// The number of styles reused via rule node comparison from the
/// StyleSharingCache.
pub styles_reused: u32,
}
/// Statistics gathered during the traversal plus some information from
/// other sources including stylist.
#[derive(Default)]
pub struct TraversalStatistics {
/// Aggregated statistics gathered during the traversal.
pub aggregated: PerThreadTraversalStatistics,
/// The number of selectors in the stylist.
pub selectors: u32,
/// The number of revalidation selectors.
pub revalidation_selectors: u32,
/// The number of state/attr dependencies in the dependency set.
pub dependency_selectors: u32,
/// The number of declarations in the stylist.
pub declarations: u32,
/// The number of times the stylist was rebuilt.
pub stylist_rebuilds: u32,
/// Time spent in the traversal, in milliseconds.
pub traversal_time: Duration,
/// Whether this was a parallel traversal.
pub is_parallel: bool,
/// Whether this is a "large" traversal.
pub is_large: bool,
}
/// Format the statistics in a way that the performance test harness understands.
impl fmt::Display for TraversalStatistics {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
writeln!(f, "[PERF] perf block start")?;
writeln!(
f,
"[PERF],traversal,{}",
if self.is_parallel {
"parallel"
} else {
"sequential"
}
)?;
writeln!(
f,
"[PERF],elements_traversed,{}",
self.aggregated.elements_traversed
)?;
writeln!(
f,
"[PERF],elements_styled,{}",
self.aggregated.elements_styled
)?;
writeln!(
f,
"[PERF],elements_matched,{}",
self.aggregated.elements_matched
)?;
writeln!(f, "[PERF],styles_shared,{}", self.aggregated.styles_shared)?;
writeln!(f, "[PERF],styles_reused,{}", self.aggregated.styles_reused)?;
writeln!(f, "[PERF],selectors,{}", self.selectors)?;
writeln!(
f,
"[PERF],revalidation_selectors,{}",
self.revalidation_selectors
)?;
writeln!(
f,
"[PERF],dependency_selectors,{}",
self.dependency_selectors
)?;
writeln!(f, "[PERF],declarations,{}", self.declarations)?;
writeln!(f, "[PERF],stylist_rebuilds,{}", self.stylist_rebuilds)?;
writeln!(f, "[PERF],traversal_time_ms,{}", self.traversal_time.as_secs_f64() * 1000.)?;
writeln!(f, "[PERF] perf block end")
}
}
impl TraversalStatistics {
/// Generate complete traversal statistics.
///
/// The traversal time is computed given the start time in seconds.
pub fn new<E, D>(
aggregated: PerThreadTraversalStatistics,
traversal: &D,
parallel: bool,
start: Instant,
) -> TraversalStatistics
where
E: TElement,
D: DomTraversal<E>,
{
let threshold = traversal
.shared_context()
.options
.style_statistics_threshold;
let stylist = traversal.shared_context().stylist;
let is_large = aggregated.elements_traversed as usize >= threshold;
TraversalStatistics {
aggregated,
selectors: stylist.num_selectors() as u32,
revalidation_selectors: stylist.num_revalidation_selectors() as u32,
dependency_selectors: stylist.num_invalidations() as u32,
declarations: stylist.num_declarations() as u32,
stylist_rebuilds: stylist.num_rebuilds() as u32,
traversal_time: Instant::now() - start,
is_parallel: parallel,
is_large,
}
}
}
#[cfg(feature = "gecko")]
bitflags! {
/// Represents which tasks are performed in a SequentialTask of
/// UpdateAnimations which is a result of normal restyle.
pub struct UpdateAnimationsTasks: u8 {
/// Update CSS Animations.
const CSS_ANIMATIONS = structs::UpdateAnimationsTasks_CSSAnimations;
/// Update CSS Transitions.
const CSS_TRANSITIONS = structs::UpdateAnimationsTasks_CSSTransitions;
/// Update effect properties.
const EFFECT_PROPERTIES = structs::UpdateAnimationsTasks_EffectProperties;
/// Update animation cacade results for animations running on the compositor.
const CASCADE_RESULTS = structs::UpdateAnimationsTasks_CascadeResults;
/// Display property was changed from none.
/// Script animations keep alive on display:none elements, so we need to trigger
/// the second animation restyles for the script animations in the case where
/// the display property was changed from 'none' to others.
const DISPLAY_CHANGED_FROM_NONE = structs::UpdateAnimationsTasks_DisplayChangedFromNone;
/// Update CSS named scroll progress timelines.
const SCROLL_TIMELINES = structs::UpdateAnimationsTasks_ScrollTimelines;
/// Update CSS named view progress timelines.
const VIEW_TIMELINES = structs::UpdateAnimationsTasks_ViewTimelines;
}
}
#[cfg(feature = "gecko")]
bitflags! {
/// Represents which tasks are performed in a SequentialTask as a result of
/// animation-only restyle.
pub struct PostAnimationTasks: u8 {
/// Display property was changed from none in animation-only restyle so
/// that we need to resolve styles for descendants in a subsequent
/// normal restyle.
const DISPLAY_CHANGED_FROM_NONE_FOR_SMIL = 0x01;
}
}
/// A task to be run in sequential mode on the parent (non-worker) thread. This
/// is used by the style system to queue up work which is not safe to do during
/// the parallel traversal.
pub enum SequentialTask<E: TElement> {
/// Entry to avoid an unused type parameter error on servo.
Unused(SendElement<E>),
/// Performs one of a number of possible tasks related to updating
/// animations based on the |tasks| field. These include updating CSS
/// animations/transitions that changed as part of the non-animation style
/// traversal, and updating the computed effect properties.
#[cfg(feature = "gecko")]
UpdateAnimations {
/// The target element or pseudo-element.
el: SendElement<E>,
/// The before-change style for transitions. We use before-change style
/// as the initial value of its Keyframe. Required if |tasks| includes
/// CSSTransitions.
before_change_style: Option<Arc<ComputedValues>>,
/// The tasks which are performed in this SequentialTask.
tasks: UpdateAnimationsTasks,
},
/// Performs one of a number of possible tasks as a result of animation-only
/// restyle.
///
/// Currently we do only process for resolving descendant elements that were
/// display:none subtree for SMIL animation.
#[cfg(feature = "gecko")]
PostAnimation {
/// The target element.
el: SendElement<E>,
/// The tasks which are performed in this SequentialTask.
tasks: PostAnimationTasks,
},
}
impl<E: TElement> SequentialTask<E> {
/// Executes this task.
pub fn execute(self) {
use self::SequentialTask::*;
debug_assert_eq!(thread_state::get(), ThreadState::LAYOUT);
match self {
Unused(_) => unreachable!(),
#[cfg(feature = "gecko")]
UpdateAnimations {
el,
before_change_style,
tasks,
} => {
el.update_animations(before_change_style, tasks);
},
#[cfg(feature = "gecko")]
PostAnimation { el, tasks } => {
el.process_post_animation(tasks);
},
}
}
/// Creates a task to update various animation-related state on a given
/// (pseudo-)element.
#[cfg(feature = "gecko")]
pub fn update_animations(
el: E,
before_change_style: Option<Arc<ComputedValues>>,
tasks: UpdateAnimationsTasks,
) -> Self {
use self::SequentialTask::*;
UpdateAnimations {
el: unsafe { SendElement::new(el) },
before_change_style,
tasks,
}
}
/// Creates a task to do post-process for a given element as a result of
/// animation-only restyle.
#[cfg(feature = "gecko")]
pub fn process_post_animation(el: E, tasks: PostAnimationTasks) -> Self {
use self::SequentialTask::*;
PostAnimation {
el: unsafe { SendElement::new(el) },
tasks,
}
}
}
/// A list of SequentialTasks that get executed on Drop.
pub struct SequentialTaskList<E>(Vec<SequentialTask<E>>)
where
E: TElement;
impl<E> ops::Deref for SequentialTaskList<E>
where
E: TElement,
{
type Target = Vec<SequentialTask<E>>;
fn deref(&self) -> &Self::Target {
&self.0
}
}
impl<E> ops::DerefMut for SequentialTaskList<E>
where
E: TElement,
{
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.0
}
}
impl<E> Drop for SequentialTaskList<E>
where
E: TElement,
{
fn drop(&mut self) {
debug_assert_eq!(thread_state::get(), ThreadState::LAYOUT);
for task in self.0.drain(..) {
task.execute()
}
}
}
/// A helper type for stack limit checking. This assumes that stacks grow
/// down, which is true for all non-ancient CPU architectures.
pub struct StackLimitChecker {
lower_limit: usize,
}
impl StackLimitChecker {
/// Create a new limit checker, for this thread, allowing further use
/// of up to |stack_size| bytes beyond (below) the current stack pointer.
#[inline(never)]
pub fn new(stack_size_limit: usize) -> Self {
StackLimitChecker {
lower_limit: StackLimitChecker::get_sp() - stack_size_limit,
}
}
/// Checks whether the previously stored stack limit has now been exceeded.
#[inline(never)]
pub fn limit_exceeded(&self) -> bool {
let curr_sp = StackLimitChecker::get_sp();
// Do some sanity-checking to ensure that our invariants hold, even in
// the case where we've exceeded the soft limit.
//
// The correctness of depends on the assumption that no stack wraps
// around the end of the address space.
if cfg!(debug_assertions) {
// Compute the actual bottom of the stack by subtracting our safety
// margin from our soft limit. Note that this will be slightly below
// the actual bottom of the stack, because there are a few initial
// frames on the stack before we do the measurement that computes
// the limit.
let stack_bottom = self.lower_limit - STACK_SAFETY_MARGIN_KB * 1024;
// The bottom of the stack should be below the current sp. If it
// isn't, that means we've either waited too long to check the limit
// and burned through our safety margin (in which case we probably
// would have segfaulted by now), or we're using a limit computed for
// a different thread.
debug_assert!(stack_bottom < curr_sp);
// Compute the distance between the current sp and the bottom of
// the stack, and compare it against the current stack. It should be
// no further from us than the total stack size. We allow some slop
// to handle the fact that stack_bottom is a bit further than the
// bottom of the stack, as discussed above.
let distance_to_stack_bottom = curr_sp - stack_bottom;
let max_allowable_distance = (STYLE_THREAD_STACK_SIZE_KB + 10) * 1024;
debug_assert!(distance_to_stack_bottom <= max_allowable_distance);
}
// The actual bounds check.
curr_sp <= self.lower_limit
}
// Technically, rustc can optimize this away, but shouldn't for now.
// We should fix this once black_box is stable.
#[inline(always)]
fn get_sp() -> usize {
let mut foo: usize = 42;
(&mut foo as *mut usize) as usize
}
}
/// A thread-local style context.
///
/// This context contains data that needs to be used during restyling, but is
/// not required to be unique among worker threads, so we create one per worker
/// thread in order to be able to mutate it without locking.
pub struct ThreadLocalStyleContext<E: TElement> {
/// A cache to share style among siblings.
pub sharing_cache: StyleSharingCache<E>,
/// A cache from matched properties to elements that match those.
pub rule_cache: RuleCache,
/// The bloom filter used to fast-reject selector-matching.
pub bloom_filter: StyleBloom<E>,
/// A set of tasks to be run (on the parent thread) in sequential mode after
/// the rest of the styling is complete. This is useful for
/// infrequently-needed non-threadsafe operations.
///
/// It's important that goes after the style sharing cache and the bloom
/// filter, to ensure they're dropped before we execute the tasks, which
/// could create another ThreadLocalStyleContext for style computation.
pub tasks: SequentialTaskList<E>,
/// Statistics about the traversal.
pub statistics: PerThreadTraversalStatistics,
/// A checker used to ensure that parallel.rs does not recurse indefinitely
pub stack_limit_checker: StackLimitChecker,
/// Collection of caches (And cache-likes) for speeding up expensive selector matches.
pub selector_caches: SelectorCaches,
}
impl<E: TElement> ThreadLocalStyleContext<E> {
/// Creates a new `ThreadLocalStyleContext`
pub fn new() -> Self {
ThreadLocalStyleContext {
sharing_cache: StyleSharingCache::new(),
rule_cache: RuleCache::new(),
bloom_filter: StyleBloom::new(),
tasks: SequentialTaskList(Vec::new()),
statistics: PerThreadTraversalStatistics::default(),
stack_limit_checker: StackLimitChecker::new(
(STYLE_THREAD_STACK_SIZE_KB - STACK_SAFETY_MARGIN_KB) * 1024,
),
selector_caches: SelectorCaches::default(),
}
}
}
/// A `StyleContext` is just a simple container for a immutable reference to a
/// shared style context, and a mutable reference to a local one.
pub struct StyleContext<'a, E: TElement + 'a> {
/// The shared style context reference.
pub shared: &'a SharedStyleContext<'a>,
/// The thread-local style context (mutable) reference.
pub thread_local: &'a mut ThreadLocalStyleContext<E>,
}
/// A registered painter
#[cfg(feature = "servo")]
pub trait RegisteredSpeculativePainter: SpeculativePainter {
/// The name it was registered with
fn name(&self) -> Atom;
/// The properties it was registered with
fn properties(&self) -> &FxHashMap<Atom, PropertyId>;
}
/// A set of registered painters
#[cfg(feature = "servo")]
pub trait RegisteredSpeculativePainters: Sync {
/// Look up a speculative painter
fn get(&self, name: &Atom) -> Option<&dyn RegisteredSpeculativePainter>;
}