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| -rw-r--r-- | servo/components/style/context.rs | 698 |
1 files changed, 698 insertions, 0 deletions
diff --git a/servo/components/style/context.rs b/servo/components/style/context.rs new file mode 100644 index 0000000000..f38963539b --- /dev/null +++ b/servo/components/style/context.rs @@ -0,0 +1,698 @@ +/* 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 https://mozilla.org/MPL/2.0/. */ + +//! 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::NthIndexCache; +#[cfg(feature = "gecko")] +use servo_arc::Arc; +#[cfg(feature = "servo")] +use servo_atoms::Atom; +use std::fmt; +use std::ops; +use style_traits::CSSPixel; +use style_traits::DevicePixel; +#[cfg(feature = "servo")] +use style_traits::SpeculativePainter; +use time; + +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`. +/// See [#22854](https://github.com/servo/servo/issues/22854). +#[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`. +/// See [#22854](https://github.com/servo/servo/issues/22854). +#[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_ms: f64, + /// 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. +/// See https://bugzilla.mozilla.org/show_bug.cgi?id=1331856#c2 +impl fmt::Display for TraversalStatistics { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + debug_assert!( + self.traversal_time_ms != 0.0, + "should have set traversal time" + ); + 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_ms)?; + 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: f64, + ) -> 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_ms: (time::precise_time_s() - start) * 1000.0, + 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 + /// even on arbitrarily deep trees. See Gecko bug 1376883. + pub stack_limit_checker: StackLimitChecker, + /// A cache for nth-index-like selectors. + pub nth_index_cache: NthIndexCache, +} + +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, + ), + nth_index_cache: NthIndexCache::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>; +} |