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Diffstat (limited to '')
| -rw-r--r-- | servo/components/style/data.rs | 545 |
1 files changed, 545 insertions, 0 deletions
diff --git a/servo/components/style/data.rs b/servo/components/style/data.rs new file mode 100644 index 0000000000..62dff225f8 --- /dev/null +++ b/servo/components/style/data.rs @@ -0,0 +1,545 @@ +/* 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/. */ + +//! Per-node data used in style calculation. + +use crate::computed_value_flags::ComputedValueFlags; +use crate::context::{SharedStyleContext, StackLimitChecker}; +use crate::dom::TElement; +use crate::invalidation::element::invalidator::InvalidationResult; +use crate::invalidation::element::restyle_hints::RestyleHint; +use crate::properties::ComputedValues; +use crate::selector_parser::{PseudoElement, RestyleDamage, EAGER_PSEUDO_COUNT}; +use crate::style_resolver::{PrimaryStyle, ResolvedElementStyles, ResolvedStyle}; +#[cfg(feature = "gecko")] +use malloc_size_of::MallocSizeOfOps; +use selectors::NthIndexCache; +use servo_arc::Arc; +use std::fmt; +use std::mem; +use std::ops::{Deref, DerefMut}; + +bitflags! { + /// Various flags stored on ElementData. + #[derive(Default)] + pub struct ElementDataFlags: u8 { + /// Whether the styles changed for this restyle. + const WAS_RESTYLED = 1 << 0; + /// Whether the last traversal of this element did not do + /// any style computation. This is not true during the initial + /// styling pass, nor is it true when we restyle (in which case + /// WAS_RESTYLED is set). + /// + /// This bit always corresponds to the last time the element was + /// traversed, so each traversal simply updates it with the appropriate + /// value. + const TRAVERSED_WITHOUT_STYLING = 1 << 1; + + /// Whether the primary style of this element data was reused from + /// another element via a rule node comparison. This allows us to + /// differentiate between elements that shared styles because they met + /// all the criteria of the style sharing cache, compared to elements + /// that reused style structs via rule node identity. + /// + /// The former gives us stronger transitive guarantees that allows us to + /// apply the style sharing cache to cousins. + const PRIMARY_STYLE_REUSED_VIA_RULE_NODE = 1 << 2; + } +} + +/// A lazily-allocated list of styles for eagerly-cascaded pseudo-elements. +/// +/// We use an Arc so that sharing these styles via the style sharing cache does +/// not require duplicate allocations. We leverage the copy-on-write semantics of +/// Arc::make_mut(), which is free (i.e. does not require atomic RMU operations) +/// in servo_arc. +#[derive(Clone, Debug, Default)] +pub struct EagerPseudoStyles(Option<Arc<EagerPseudoArray>>); + +#[derive(Default)] +struct EagerPseudoArray(EagerPseudoArrayInner); +type EagerPseudoArrayInner = [Option<Arc<ComputedValues>>; EAGER_PSEUDO_COUNT]; + +impl Deref for EagerPseudoArray { + type Target = EagerPseudoArrayInner; + fn deref(&self) -> &Self::Target { + &self.0 + } +} + +impl DerefMut for EagerPseudoArray { + fn deref_mut(&mut self) -> &mut Self::Target { + &mut self.0 + } +} + +// Manually implement `Clone` here because the derived impl of `Clone` for +// array types assumes the value inside is `Copy`. +impl Clone for EagerPseudoArray { + fn clone(&self) -> Self { + let mut clone = Self::default(); + for i in 0..EAGER_PSEUDO_COUNT { + clone[i] = self.0[i].clone(); + } + clone + } +} + +// Override Debug to print which pseudos we have, and substitute the rule node +// for the much-more-verbose ComputedValues stringification. +impl fmt::Debug for EagerPseudoArray { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + write!(f, "EagerPseudoArray {{ ")?; + for i in 0..EAGER_PSEUDO_COUNT { + if let Some(ref values) = self[i] { + write!( + f, + "{:?}: {:?}, ", + PseudoElement::from_eager_index(i), + &values.rules + )?; + } + } + write!(f, "}}") + } +} + +// Can't use [None; EAGER_PSEUDO_COUNT] here because it complains +// about Copy not being implemented for our Arc type. +#[cfg(feature = "gecko")] +const EMPTY_PSEUDO_ARRAY: &'static EagerPseudoArrayInner = &[None, None, None, None]; +#[cfg(feature = "servo")] +const EMPTY_PSEUDO_ARRAY: &'static EagerPseudoArrayInner = &[None, None, None]; + +impl EagerPseudoStyles { + /// Returns whether there are any pseudo styles. + pub fn is_empty(&self) -> bool { + self.0.is_none() + } + + /// Grabs a reference to the list of styles, if they exist. + pub fn as_optional_array(&self) -> Option<&EagerPseudoArrayInner> { + match self.0 { + None => None, + Some(ref x) => Some(&x.0), + } + } + + /// Grabs a reference to the list of styles or a list of None if + /// there are no styles to be had. + pub fn as_array(&self) -> &EagerPseudoArrayInner { + self.as_optional_array().unwrap_or(EMPTY_PSEUDO_ARRAY) + } + + /// Returns a reference to the style for a given eager pseudo, if it exists. + pub fn get(&self, pseudo: &PseudoElement) -> Option<&Arc<ComputedValues>> { + debug_assert!(pseudo.is_eager()); + self.0 + .as_ref() + .and_then(|p| p[pseudo.eager_index()].as_ref()) + } + + /// Sets the style for the eager pseudo. + pub fn set(&mut self, pseudo: &PseudoElement, value: Arc<ComputedValues>) { + if self.0.is_none() { + self.0 = Some(Arc::new(Default::default())); + } + let arr = Arc::make_mut(self.0.as_mut().unwrap()); + arr[pseudo.eager_index()] = Some(value); + } +} + +/// The styles associated with a node, including the styles for any +/// pseudo-elements. +#[derive(Clone, Default)] +pub struct ElementStyles { + /// The element's style. + pub primary: Option<Arc<ComputedValues>>, + /// A list of the styles for the element's eagerly-cascaded pseudo-elements. + pub pseudos: EagerPseudoStyles, +} + +// There's one of these per rendered elements so it better be small. +size_of_test!(ElementStyles, 16); + +/// Information on how this element uses viewport units. +#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)] +pub enum ViewportUnitUsage { + /// No viewport units are used. + None = 0, + /// There are viewport units used from regular style rules (which means we + /// should re-cascade). + FromDeclaration, + /// There are viewport units used from container queries (which means we + /// need to re-selector-match). + FromQuery, +} + +impl ElementStyles { + /// Returns the primary style. + pub fn get_primary(&self) -> Option<&Arc<ComputedValues>> { + self.primary.as_ref() + } + + /// Returns the primary style. Panic if no style available. + pub fn primary(&self) -> &Arc<ComputedValues> { + self.primary.as_ref().unwrap() + } + + /// Whether this element `display` value is `none`. + pub fn is_display_none(&self) -> bool { + self.primary().get_box().clone_display().is_none() + } + + /// Whether this element uses viewport units. + pub fn viewport_unit_usage(&self) -> ViewportUnitUsage { + fn usage_from_flags(flags: ComputedValueFlags) -> ViewportUnitUsage { + if flags.intersects(ComputedValueFlags::USES_VIEWPORT_UNITS_ON_CONTAINER_QUERIES) { + return ViewportUnitUsage::FromQuery; + } + if flags.intersects(ComputedValueFlags::USES_VIEWPORT_UNITS) { + return ViewportUnitUsage::FromDeclaration; + } + ViewportUnitUsage::None + } + + let mut usage = usage_from_flags(self.primary().flags); + for pseudo_style in self.pseudos.as_array() { + if let Some(ref pseudo_style) = pseudo_style { + usage = std::cmp::max(usage, usage_from_flags(pseudo_style.flags)); + } + } + + usage + } + + #[cfg(feature = "gecko")] + fn size_of_excluding_cvs(&self, _ops: &mut MallocSizeOfOps) -> usize { + // As the method name suggests, we don't measures the ComputedValues + // here, because they are measured on the C++ side. + + // XXX: measure the EagerPseudoArray itself, but not the ComputedValues + // within it. + + 0 + } +} + +// We manually implement Debug for ElementStyles so that we can avoid the +// verbose stringification of every property in the ComputedValues. We +// substitute the rule node instead. +impl fmt::Debug for ElementStyles { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + write!( + f, + "ElementStyles {{ primary: {:?}, pseudos: {:?} }}", + self.primary.as_ref().map(|x| &x.rules), + self.pseudos + ) + } +} + +/// Style system data associated with an Element. +/// +/// In Gecko, this hangs directly off the Element. Servo, this is embedded +/// inside of layout data, which itself hangs directly off the Element. In +/// both cases, it is wrapped inside an AtomicRefCell to ensure thread safety. +#[derive(Debug, Default)] +pub struct ElementData { + /// The styles for the element and its pseudo-elements. + pub styles: ElementStyles, + + /// The restyle damage, indicating what kind of layout changes are required + /// afte restyling. + pub damage: RestyleDamage, + + /// The restyle hint, which indicates whether selectors need to be rematched + /// for this element, its children, and its descendants. + pub hint: RestyleHint, + + /// Flags. + pub flags: ElementDataFlags, +} + +// There's one of these per rendered elements so it better be small. +size_of_test!(ElementData, 24); + +/// The kind of restyle that a single element should do. +#[derive(Debug)] +pub enum RestyleKind { + /// We need to run selector matching plus re-cascade, that is, a full + /// restyle. + MatchAndCascade, + /// We need to recascade with some replacement rule, such as the style + /// attribute, or animation rules. + CascadeWithReplacements(RestyleHint), + /// We only need to recascade, for example, because only inherited + /// properties in the parent changed. + CascadeOnly, +} + +impl ElementData { + /// Invalidates style for this element, its descendants, and later siblings, + /// based on the snapshot of the element that we took when attributes or + /// state changed. + pub fn invalidate_style_if_needed<'a, E: TElement>( + &mut self, + element: E, + shared_context: &SharedStyleContext, + stack_limit_checker: Option<&StackLimitChecker>, + nth_index_cache: &mut NthIndexCache, + ) -> InvalidationResult { + // In animation-only restyle we shouldn't touch snapshot at all. + if shared_context.traversal_flags.for_animation_only() { + return InvalidationResult::empty(); + } + + use crate::invalidation::element::invalidator::TreeStyleInvalidator; + use crate::invalidation::element::state_and_attributes::StateAndAttrInvalidationProcessor; + + debug!( + "invalidate_style_if_needed: {:?}, flags: {:?}, has_snapshot: {}, \ + handled_snapshot: {}, pseudo: {:?}", + element, + shared_context.traversal_flags, + element.has_snapshot(), + element.handled_snapshot(), + element.implemented_pseudo_element() + ); + + if !element.has_snapshot() || element.handled_snapshot() { + return InvalidationResult::empty(); + } + + let mut processor = + StateAndAttrInvalidationProcessor::new(shared_context, element, self, nth_index_cache); + + let invalidator = TreeStyleInvalidator::new(element, stack_limit_checker, &mut processor); + + let result = invalidator.invalidate(); + + unsafe { element.set_handled_snapshot() } + debug_assert!(element.handled_snapshot()); + + result + } + + /// Returns true if this element has styles. + #[inline] + pub fn has_styles(&self) -> bool { + self.styles.primary.is_some() + } + + /// Returns this element's styles as resolved styles to use for sharing. + pub fn share_styles(&self) -> ResolvedElementStyles { + ResolvedElementStyles { + primary: self.share_primary_style(), + pseudos: self.styles.pseudos.clone(), + } + } + + /// Returns this element's primary style as a resolved style to use for sharing. + pub fn share_primary_style(&self) -> PrimaryStyle { + let reused_via_rule_node = self + .flags + .contains(ElementDataFlags::PRIMARY_STYLE_REUSED_VIA_RULE_NODE); + + PrimaryStyle { + style: ResolvedStyle(self.styles.primary().clone()), + reused_via_rule_node, + } + } + + /// Sets a new set of styles, returning the old ones. + pub fn set_styles(&mut self, new_styles: ResolvedElementStyles) -> ElementStyles { + if new_styles.primary.reused_via_rule_node { + self.flags + .insert(ElementDataFlags::PRIMARY_STYLE_REUSED_VIA_RULE_NODE); + } else { + self.flags + .remove(ElementDataFlags::PRIMARY_STYLE_REUSED_VIA_RULE_NODE); + } + mem::replace(&mut self.styles, new_styles.into()) + } + + /// Returns the kind of restyling that we're going to need to do on this + /// element, based of the stored restyle hint. + pub fn restyle_kind(&self, shared_context: &SharedStyleContext) -> Option<RestyleKind> { + if shared_context.traversal_flags.for_animation_only() { + return self.restyle_kind_for_animation(shared_context); + } + + let style = match self.styles.primary { + Some(ref s) => s, + None => return Some(RestyleKind::MatchAndCascade), + }; + + let hint = self.hint; + if hint.is_empty() { + return None; + } + + let needs_to_match_self = hint.intersects(RestyleHint::RESTYLE_SELF) || + (hint.intersects(RestyleHint::RESTYLE_SELF_IF_PSEUDO) && style.is_pseudo_style()); + if needs_to_match_self { + return Some(RestyleKind::MatchAndCascade); + } + + if hint.has_replacements() { + debug_assert!( + !hint.has_animation_hint(), + "Animation only restyle hint should have already processed" + ); + return Some(RestyleKind::CascadeWithReplacements( + hint & RestyleHint::replacements(), + )); + } + + let needs_to_recascade_self = hint.intersects(RestyleHint::RECASCADE_SELF) || + (hint.intersects(RestyleHint::RECASCADE_SELF_IF_INHERIT_RESET_STYLE) && + style + .flags + .contains(ComputedValueFlags::INHERITS_RESET_STYLE)); + if needs_to_recascade_self { + return Some(RestyleKind::CascadeOnly); + } + + None + } + + /// Returns the kind of restyling for animation-only restyle. + fn restyle_kind_for_animation( + &self, + shared_context: &SharedStyleContext, + ) -> Option<RestyleKind> { + debug_assert!(shared_context.traversal_flags.for_animation_only()); + debug_assert!( + self.has_styles(), + "animation traversal doesn't care about unstyled elements" + ); + + // FIXME: We should ideally restyle here, but it is a hack to work around our weird + // animation-only traversal stuff: If we're display: none and the rules we could + // match could change, we consider our style up-to-date. This is because re-cascading with + // and old style doesn't guarantee returning the correct animation style (that's + // bug 1393323). So if our display changed, and it changed from display: none, we would + // incorrectly forget about it and wouldn't be able to correctly style our descendants + // later. + // XXX Figure out if this still makes sense. + let hint = self.hint; + if self.styles.is_display_none() && hint.intersects(RestyleHint::RESTYLE_SELF) { + return None; + } + + let style = self.styles.primary(); + // Return either CascadeWithReplacements or CascadeOnly in case of + // animation-only restyle. I.e. animation-only restyle never does + // selector matching. + if hint.has_animation_hint() { + return Some(RestyleKind::CascadeWithReplacements( + hint & RestyleHint::for_animations(), + )); + } + + let needs_to_recascade_self = hint.intersects(RestyleHint::RECASCADE_SELF) || + (hint.intersects(RestyleHint::RECASCADE_SELF_IF_INHERIT_RESET_STYLE) && + style + .flags + .contains(ComputedValueFlags::INHERITS_RESET_STYLE)); + if needs_to_recascade_self { + return Some(RestyleKind::CascadeOnly); + } + return None; + } + + /// Drops any restyle state from the element. + /// + /// FIXME(bholley): The only caller of this should probably just assert that + /// the hint is empty and call clear_flags_and_damage(). + #[inline] + pub fn clear_restyle_state(&mut self) { + self.hint = RestyleHint::empty(); + self.clear_restyle_flags_and_damage(); + } + + /// Drops restyle flags and damage from the element. + #[inline] + pub fn clear_restyle_flags_and_damage(&mut self) { + self.damage = RestyleDamage::empty(); + self.flags.remove(ElementDataFlags::WAS_RESTYLED); + } + + /// Mark this element as restyled, which is useful to know whether we need + /// to do a post-traversal. + pub fn set_restyled(&mut self) { + self.flags.insert(ElementDataFlags::WAS_RESTYLED); + self.flags + .remove(ElementDataFlags::TRAVERSED_WITHOUT_STYLING); + } + + /// Returns true if this element was restyled. + #[inline] + pub fn is_restyle(&self) -> bool { + self.flags.contains(ElementDataFlags::WAS_RESTYLED) + } + + /// Mark that we traversed this element without computing any style for it. + pub fn set_traversed_without_styling(&mut self) { + self.flags + .insert(ElementDataFlags::TRAVERSED_WITHOUT_STYLING); + } + + /// Returns whether this element has been part of a restyle. + #[inline] + pub fn contains_restyle_data(&self) -> bool { + self.is_restyle() || !self.hint.is_empty() || !self.damage.is_empty() + } + + /// Returns whether it is safe to perform cousin sharing based on the ComputedValues + /// identity of the primary style in this ElementData. There are a few subtle things + /// to check. + /// + /// First, if a parent element was already styled and we traversed past it without + /// restyling it, that may be because our clever invalidation logic was able to prove + /// that the styles of that element would remain unchanged despite changes to the id + /// or class attributes. However, style sharing relies on the strong guarantee that all + /// the classes and ids up the respective parent chains are identical. As such, if we + /// skipped styling for one (or both) of the parents on this traversal, we can't share + /// styles across cousins. Note that this is a somewhat conservative check. We could + /// tighten it by having the invalidation logic explicitly flag elements for which it + /// ellided styling. + /// + /// Second, we want to only consider elements whose ComputedValues match due to a hit + /// in the style sharing cache, rather than due to the rule-node-based reuse that + /// happens later in the styling pipeline. The former gives us the stronger guarantees + /// we need for style sharing, the latter does not. + pub fn safe_for_cousin_sharing(&self) -> bool { + if self.flags.intersects( + ElementDataFlags::TRAVERSED_WITHOUT_STYLING | + ElementDataFlags::PRIMARY_STYLE_REUSED_VIA_RULE_NODE, + ) { + return false; + } + if !self + .styles + .primary() + .get_box() + .clone_container_type() + .is_normal() + { + return false; + } + true + } + + /// Measures memory usage. + #[cfg(feature = "gecko")] + pub fn size_of_excluding_cvs(&self, ops: &mut MallocSizeOfOps) -> usize { + let n = self.styles.size_of_excluding_cvs(ops); + + // We may measure more fields in the future if DMD says it's worth it. + + n + } +} |