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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
+ * 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
+ }
+}
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