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diff --git a/servo/components/style/matching.rs b/servo/components/style/matching.rs
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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/. */
+
+//! High-level interface to CSS selector matching.
+
+#![allow(unsafe_code)]
+#![deny(missing_docs)]
+
+use crate::computed_value_flags::ComputedValueFlags;
+use crate::context::{CascadeInputs, ElementCascadeInputs, QuirksMode};
+use crate::context::{SharedStyleContext, StyleContext};
+use crate::data::{ElementData, ElementStyles};
+use crate::dom::TElement;
+#[cfg(feature = "servo")]
+use crate::dom::TNode;
+use crate::invalidation::element::restyle_hints::RestyleHint;
+use crate::properties::longhands::display::computed_value::T as Display;
+use crate::properties::ComputedValues;
+use crate::properties::PropertyDeclarationBlock;
+use crate::rule_tree::{CascadeLevel, StrongRuleNode};
+use crate::selector_parser::{PseudoElement, RestyleDamage};
+use crate::shared_lock::Locked;
+use crate::style_resolver::ResolvedElementStyles;
+use crate::style_resolver::{PseudoElementResolution, StyleResolverForElement};
+use crate::stylesheets::layer_rule::LayerOrder;
+use crate::stylist::RuleInclusion;
+use crate::traversal_flags::TraversalFlags;
+use servo_arc::{Arc, ArcBorrow};
+
+/// Represents the result of comparing an element's old and new style.
+#[derive(Debug)]
+pub struct StyleDifference {
+ /// The resulting damage.
+ pub damage: RestyleDamage,
+
+ /// Whether any styles changed.
+ pub change: StyleChange,
+}
+
+/// Represents whether or not the style of an element has changed.
+#[derive(Clone, Copy, Debug)]
+pub enum StyleChange {
+ /// The style hasn't changed.
+ Unchanged,
+ /// The style has changed.
+ Changed {
+ /// Whether only reset structs changed.
+ reset_only: bool,
+ },
+}
+
+/// Whether or not newly computed values for an element need to be cascaded to
+/// children (or children might need to be re-matched, e.g., for container
+/// queries).
+#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd)]
+pub enum ChildRestyleRequirement {
+ /// Old and new computed values were the same, or we otherwise know that
+ /// we won't bother recomputing style for children, so we can skip cascading
+ /// the new values into child elements.
+ CanSkipCascade = 0,
+ /// The same as `MustCascadeChildren`, but we only need to actually
+ /// recascade if the child inherits any explicit reset style.
+ MustCascadeChildrenIfInheritResetStyle = 1,
+ /// Old and new computed values were different, so we must cascade the
+ /// new values to children.
+ MustCascadeChildren = 2,
+ /// The same as `MustCascadeChildren`, but for the entire subtree. This is
+ /// used to handle root font-size updates needing to recascade the whole
+ /// document.
+ MustCascadeDescendants = 3,
+ /// We need to re-match the whole subttree. This is used to handle container
+ /// query relative unit changes for example. Container query size changes
+ /// also trigger re-match, but after layout.
+ MustMatchDescendants = 4,
+}
+
+/// Determines which styles are being cascaded currently.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+enum CascadeVisitedMode {
+ /// Cascade the regular, unvisited styles.
+ Unvisited,
+ /// Cascade the styles used when an element's relevant link is visited. A
+ /// "relevant link" is the element being matched if it is a link or the
+ /// nearest ancestor link.
+ Visited,
+}
+
+trait PrivateMatchMethods: TElement {
+ fn replace_single_rule_node(
+ context: &SharedStyleContext,
+ level: CascadeLevel,
+ layer_order: LayerOrder,
+ pdb: Option<ArcBorrow<Locked<PropertyDeclarationBlock>>>,
+ path: &mut StrongRuleNode,
+ ) -> bool {
+ let stylist = &context.stylist;
+ let guards = &context.guards;
+
+ let mut important_rules_changed = false;
+ let new_node = stylist.rule_tree().update_rule_at_level(
+ level,
+ layer_order,
+ pdb,
+ path,
+ guards,
+ &mut important_rules_changed,
+ );
+ if let Some(n) = new_node {
+ *path = n;
+ }
+ important_rules_changed
+ }
+
+ /// Updates the rule nodes without re-running selector matching, using just
+ /// the rule tree, for a specific visited mode.
+ ///
+ /// Returns true if an !important rule was replaced.
+ fn replace_rules_internal(
+ &self,
+ replacements: RestyleHint,
+ context: &mut StyleContext<Self>,
+ cascade_visited: CascadeVisitedMode,
+ cascade_inputs: &mut ElementCascadeInputs,
+ ) -> bool {
+ debug_assert!(
+ replacements.intersects(RestyleHint::replacements()) &&
+ (replacements & !RestyleHint::replacements()).is_empty()
+ );
+
+ let primary_rules = match cascade_visited {
+ CascadeVisitedMode::Unvisited => cascade_inputs.primary.rules.as_mut(),
+ CascadeVisitedMode::Visited => cascade_inputs.primary.visited_rules.as_mut(),
+ };
+
+ let primary_rules = match primary_rules {
+ Some(r) => r,
+ None => return false,
+ };
+
+ if !context.shared.traversal_flags.for_animation_only() {
+ let mut result = false;
+ if replacements.contains(RestyleHint::RESTYLE_STYLE_ATTRIBUTE) {
+ let style_attribute = self.style_attribute();
+ result |= Self::replace_single_rule_node(
+ context.shared,
+ CascadeLevel::same_tree_author_normal(),
+ LayerOrder::root(),
+ style_attribute,
+ primary_rules,
+ );
+ result |= Self::replace_single_rule_node(
+ context.shared,
+ CascadeLevel::same_tree_author_important(),
+ LayerOrder::root(),
+ style_attribute,
+ primary_rules,
+ );
+ // FIXME(emilio): Still a hack!
+ self.unset_dirty_style_attribute();
+ }
+ return result;
+ }
+
+ // Animation restyle hints are processed prior to other restyle
+ // hints in the animation-only traversal.
+ //
+ // Non-animation restyle hints will be processed in a subsequent
+ // normal traversal.
+ if replacements.intersects(RestyleHint::for_animations()) {
+ debug_assert!(context.shared.traversal_flags.for_animation_only());
+
+ if replacements.contains(RestyleHint::RESTYLE_SMIL) {
+ Self::replace_single_rule_node(
+ context.shared,
+ CascadeLevel::SMILOverride,
+ LayerOrder::root(),
+ self.smil_override(),
+ primary_rules,
+ );
+ }
+
+ if replacements.contains(RestyleHint::RESTYLE_CSS_TRANSITIONS) {
+ Self::replace_single_rule_node(
+ context.shared,
+ CascadeLevel::Transitions,
+ LayerOrder::root(),
+ self.transition_rule(&context.shared)
+ .as_ref()
+ .map(|a| a.borrow_arc()),
+ primary_rules,
+ );
+ }
+
+ if replacements.contains(RestyleHint::RESTYLE_CSS_ANIMATIONS) {
+ Self::replace_single_rule_node(
+ context.shared,
+ CascadeLevel::Animations,
+ LayerOrder::root(),
+ self.animation_rule(&context.shared)
+ .as_ref()
+ .map(|a| a.borrow_arc()),
+ primary_rules,
+ );
+ }
+ }
+
+ false
+ }
+
+ /// If there is no transition rule in the ComputedValues, it returns None.
+ fn after_change_style(
+ &self,
+ context: &mut StyleContext<Self>,
+ primary_style: &Arc<ComputedValues>,
+ ) -> Option<Arc<ComputedValues>> {
+ let rule_node = primary_style.rules();
+ let without_transition_rules = context
+ .shared
+ .stylist
+ .rule_tree()
+ .remove_transition_rule_if_applicable(rule_node);
+ if without_transition_rules == *rule_node {
+ // We don't have transition rule in this case, so return None to let
+ // the caller use the original ComputedValues.
+ return None;
+ }
+
+ // FIXME(bug 868975): We probably need to transition visited style as
+ // well.
+ let inputs = CascadeInputs {
+ rules: Some(without_transition_rules),
+ visited_rules: primary_style.visited_rules().cloned(),
+ flags: primary_style.flags.for_cascade_inputs(),
+ };
+
+ // Actually `PseudoElementResolution` doesn't really matter.
+ let style = StyleResolverForElement::new(
+ *self,
+ context,
+ RuleInclusion::All,
+ PseudoElementResolution::IfApplicable,
+ )
+ .cascade_style_and_visited_with_default_parents(inputs);
+
+ Some(style.0)
+ }
+
+ fn needs_animations_update(
+ &self,
+ context: &mut StyleContext<Self>,
+ old_style: Option<&ComputedValues>,
+ new_style: &ComputedValues,
+ pseudo_element: Option<PseudoElement>,
+ ) -> bool {
+ let new_ui_style = new_style.get_ui();
+ let new_style_specifies_animations = new_ui_style.specifies_animations();
+
+ let has_animations = self.has_css_animations(&context.shared, pseudo_element);
+ if !new_style_specifies_animations && !has_animations {
+ return false;
+ }
+
+ let old_style = match old_style {
+ Some(old) => old,
+ // If we have no old style but have animations, we may be a
+ // pseudo-element which was re-created without style changes.
+ //
+ // This can happen when we reframe the pseudo-element without
+ // restyling it (due to content insertion on a flex container or
+ // such, for example). See bug 1564366.
+ //
+ // FIXME(emilio): The really right fix for this is keeping the
+ // pseudo-element itself around on reframes, but that's a bit
+ // harder. If we do that we can probably remove quite a lot of the
+ // EffectSet complexity though, since right now it's stored on the
+ // parent element for pseudo-elements given we need to keep it
+ // around...
+ None => {
+ return new_style_specifies_animations || new_style.is_pseudo_style();
+ },
+ };
+
+ let old_ui_style = old_style.get_ui();
+
+ let keyframes_could_have_changed = context
+ .shared
+ .traversal_flags
+ .contains(TraversalFlags::ForCSSRuleChanges);
+
+ // If the traversal is triggered due to changes in CSS rules changes, we
+ // need to try to update all CSS animations on the element if the
+ // element has or will have CSS animation style regardless of whether
+ // the animation is running or not.
+ //
+ // TODO: We should check which @keyframes were added/changed/deleted and
+ // update only animations corresponding to those @keyframes.
+ if keyframes_could_have_changed {
+ return true;
+ }
+
+ // If the animations changed, well...
+ if !old_ui_style.animations_equals(new_ui_style) {
+ return true;
+ }
+
+ let old_display = old_style.clone_display();
+ let new_display = new_style.clone_display();
+
+ // If we were display: none, we may need to trigger animations.
+ if old_display == Display::None && new_display != Display::None {
+ return new_style_specifies_animations;
+ }
+
+ // If we are becoming display: none, we may need to stop animations.
+ if old_display != Display::None && new_display == Display::None {
+ return has_animations;
+ }
+
+ // We might need to update animations if writing-mode or direction
+ // changed, and any of the animations contained logical properties.
+ //
+ // We may want to be more granular, but it's probably not worth it.
+ if new_style.writing_mode != old_style.writing_mode {
+ return has_animations;
+ }
+
+ false
+ }
+
+ fn might_need_transitions_update(
+ &self,
+ context: &StyleContext<Self>,
+ old_style: Option<&ComputedValues>,
+ new_style: &ComputedValues,
+ pseudo_element: Option<PseudoElement>,
+ ) -> bool {
+ let old_style = match old_style {
+ Some(v) => v,
+ None => return false,
+ };
+
+ if !self.has_css_transitions(context.shared, pseudo_element) &&
+ !new_style.get_ui().specifies_transitions()
+ {
+ return false;
+ }
+
+ if old_style.clone_display().is_none() {
+ return false;
+ }
+
+ return true;
+ }
+
+ /// Create a SequentialTask for resolving descendants in a SMIL display
+ /// property animation if the display property changed from none.
+ #[cfg(feature = "gecko")]
+ fn handle_display_change_for_smil_if_needed(
+ &self,
+ context: &mut StyleContext<Self>,
+ old_values: Option<&ComputedValues>,
+ new_values: &ComputedValues,
+ restyle_hints: RestyleHint,
+ ) {
+ use crate::context::PostAnimationTasks;
+
+ if !restyle_hints.intersects(RestyleHint::RESTYLE_SMIL) {
+ return;
+ }
+
+ if new_values.is_display_property_changed_from_none(old_values) {
+ // When display value is changed from none to other, we need to
+ // traverse descendant elements in a subsequent normal
+ // traversal (we can't traverse them in this animation-only restyle
+ // since we have no way to know whether the decendants
+ // need to be traversed at the beginning of the animation-only
+ // restyle).
+ let task = crate::context::SequentialTask::process_post_animation(
+ *self,
+ PostAnimationTasks::DISPLAY_CHANGED_FROM_NONE_FOR_SMIL,
+ );
+ context.thread_local.tasks.push(task);
+ }
+ }
+
+ #[cfg(feature = "gecko")]
+ fn process_animations(
+ &self,
+ context: &mut StyleContext<Self>,
+ old_styles: &mut ElementStyles,
+ new_styles: &mut ResolvedElementStyles,
+ restyle_hint: RestyleHint,
+ important_rules_changed: bool,
+ ) {
+ use crate::context::UpdateAnimationsTasks;
+
+ let new_values = new_styles.primary_style_mut();
+ let old_values = &old_styles.primary;
+ if context.shared.traversal_flags.for_animation_only() {
+ self.handle_display_change_for_smil_if_needed(
+ context,
+ old_values.as_deref(),
+ new_values,
+ restyle_hint,
+ );
+ return;
+ }
+
+ // Bug 868975: These steps should examine and update the visited styles
+ // in addition to the unvisited styles.
+
+ let mut tasks = UpdateAnimationsTasks::empty();
+
+ if old_values.as_deref().map_or_else(
+ || new_values.get_ui().specifies_scroll_timelines(),
+ |old| !old.get_ui().scroll_timelines_equals(new_values.get_ui()),
+ ) {
+ tasks.insert(UpdateAnimationsTasks::SCROLL_TIMELINES);
+ }
+
+ if old_values.as_deref().map_or_else(
+ || new_values.get_ui().specifies_view_timelines(),
+ |old| !old.get_ui().view_timelines_equals(new_values.get_ui()),
+ ) {
+ tasks.insert(UpdateAnimationsTasks::VIEW_TIMELINES);
+ }
+
+ if self.needs_animations_update(
+ context,
+ old_values.as_deref(),
+ new_values,
+ /* pseudo_element = */ None,
+ ) {
+ tasks.insert(UpdateAnimationsTasks::CSS_ANIMATIONS);
+ }
+
+ let before_change_style = if self.might_need_transitions_update(
+ context,
+ old_values.as_deref(),
+ new_values,
+ /* pseudo_element = */ None,
+ ) {
+ let after_change_style =
+ if self.has_css_transitions(context.shared, /* pseudo_element = */ None) {
+ self.after_change_style(context, new_values)
+ } else {
+ None
+ };
+
+ // In order to avoid creating a SequentialTask for transitions which
+ // may not be updated, we check it per property to make sure Gecko
+ // side will really update transition.
+ let needs_transitions_update = {
+ // We borrow new_values here, so need to add a scope to make
+ // sure we release it before assigning a new value to it.
+ let after_change_style_ref = after_change_style.as_ref().unwrap_or(&new_values);
+
+ self.needs_transitions_update(old_values.as_ref().unwrap(), after_change_style_ref)
+ };
+
+ if needs_transitions_update {
+ if let Some(values_without_transitions) = after_change_style {
+ *new_values = values_without_transitions;
+ }
+ tasks.insert(UpdateAnimationsTasks::CSS_TRANSITIONS);
+
+ // We need to clone old_values into SequentialTask, so we can
+ // use it later.
+ old_values.clone()
+ } else {
+ None
+ }
+ } else {
+ None
+ };
+
+ if self.has_animations(&context.shared) {
+ tasks.insert(UpdateAnimationsTasks::EFFECT_PROPERTIES);
+ if important_rules_changed {
+ tasks.insert(UpdateAnimationsTasks::CASCADE_RESULTS);
+ }
+ if new_values.is_display_property_changed_from_none(old_values.as_deref()) {
+ tasks.insert(UpdateAnimationsTasks::DISPLAY_CHANGED_FROM_NONE);
+ }
+ }
+
+ if !tasks.is_empty() {
+ let task = crate::context::SequentialTask::update_animations(
+ *self,
+ before_change_style,
+ tasks,
+ );
+ context.thread_local.tasks.push(task);
+ }
+ }
+
+ #[cfg(feature = "servo")]
+ fn process_animations(
+ &self,
+ context: &mut StyleContext<Self>,
+ old_styles: &mut ElementStyles,
+ new_resolved_styles: &mut ResolvedElementStyles,
+ _restyle_hint: RestyleHint,
+ _important_rules_changed: bool,
+ ) {
+ use crate::animation::AnimationSetKey;
+ use crate::dom::TDocument;
+
+ let style_changed = self.process_animations_for_style(
+ context,
+ &mut old_styles.primary,
+ new_resolved_styles.primary_style_mut(),
+ /* pseudo_element = */ None,
+ );
+
+ // If we have modified animation or transitions, we recascade style for this node.
+ if style_changed {
+ let mut rule_node = new_resolved_styles.primary_style().rules().clone();
+ let declarations = context.shared.animations.get_all_declarations(
+ &AnimationSetKey::new_for_non_pseudo(self.as_node().opaque()),
+ context.shared.current_time_for_animations,
+ self.as_node().owner_doc().shared_lock(),
+ );
+ Self::replace_single_rule_node(
+ &context.shared,
+ CascadeLevel::Transitions,
+ declarations.transitions.as_ref().map(|a| a.borrow_arc()),
+ &mut rule_node,
+ );
+ Self::replace_single_rule_node(
+ &context.shared,
+ CascadeLevel::Animations,
+ declarations.animations.as_ref().map(|a| a.borrow_arc()),
+ &mut rule_node,
+ );
+
+ if rule_node != *new_resolved_styles.primary_style().rules() {
+ let inputs = CascadeInputs {
+ rules: Some(rule_node),
+ visited_rules: new_resolved_styles.primary_style().visited_rules().cloned(),
+ };
+
+ new_resolved_styles.primary.style = StyleResolverForElement::new(
+ *self,
+ context,
+ RuleInclusion::All,
+ PseudoElementResolution::IfApplicable,
+ )
+ .cascade_style_and_visited_with_default_parents(inputs);
+ }
+ }
+
+ self.process_animations_for_pseudo(
+ context,
+ old_styles,
+ new_resolved_styles,
+ PseudoElement::Before,
+ );
+ self.process_animations_for_pseudo(
+ context,
+ old_styles,
+ new_resolved_styles,
+ PseudoElement::After,
+ );
+ }
+
+ #[cfg(feature = "servo")]
+ fn process_animations_for_pseudo(
+ &self,
+ context: &mut StyleContext<Self>,
+ old_styles: &mut ElementStyles,
+ new_resolved_styles: &mut ResolvedElementStyles,
+ pseudo_element: PseudoElement,
+ ) {
+ use crate::animation::AnimationSetKey;
+ use crate::dom::TDocument;
+
+ let key = AnimationSetKey::new_for_pseudo(self.as_node().opaque(), pseudo_element.clone());
+ let mut style = match new_resolved_styles.pseudos.get(&pseudo_element) {
+ Some(style) => Arc::clone(style),
+ None => {
+ context
+ .shared
+ .animations
+ .cancel_all_animations_for_key(&key);
+ return;
+ },
+ };
+
+ let mut old_style = old_styles.pseudos.get(&pseudo_element).cloned();
+ self.process_animations_for_style(
+ context,
+ &mut old_style,
+ &mut style,
+ Some(pseudo_element.clone()),
+ );
+
+ let declarations = context.shared.animations.get_all_declarations(
+ &key,
+ context.shared.current_time_for_animations,
+ self.as_node().owner_doc().shared_lock(),
+ );
+ if declarations.is_empty() {
+ return;
+ }
+
+ let mut rule_node = style.rules().clone();
+ Self::replace_single_rule_node(
+ &context.shared,
+ CascadeLevel::Transitions,
+ LayerOrder::root(),
+ declarations.transitions.as_ref().map(|a| a.borrow_arc()),
+ &mut rule_node,
+ );
+ Self::replace_single_rule_node(
+ &context.shared,
+ CascadeLevel::Animations,
+ LayerOrder::root(),
+ declarations.animations.as_ref().map(|a| a.borrow_arc()),
+ &mut rule_node,
+ );
+ if rule_node == *style.rules() {
+ return;
+ }
+
+ let inputs = CascadeInputs {
+ rules: Some(rule_node),
+ visited_rules: style.visited_rules().cloned(),
+ };
+
+ let new_style = StyleResolverForElement::new(
+ *self,
+ context,
+ RuleInclusion::All,
+ PseudoElementResolution::IfApplicable,
+ )
+ .cascade_style_and_visited_for_pseudo_with_default_parents(
+ inputs,
+ &pseudo_element,
+ &new_resolved_styles.primary,
+ );
+
+ new_resolved_styles
+ .pseudos
+ .set(&pseudo_element, new_style.0);
+ }
+
+ #[cfg(feature = "servo")]
+ fn process_animations_for_style(
+ &self,
+ context: &mut StyleContext<Self>,
+ old_values: &mut Option<Arc<ComputedValues>>,
+ new_values: &mut Arc<ComputedValues>,
+ pseudo_element: Option<PseudoElement>,
+ ) -> bool {
+ use crate::animation::{AnimationSetKey, AnimationState};
+
+ // We need to call this before accessing the `ElementAnimationSet` from the
+ // map because this call will do a RwLock::read().
+ let needs_animations_update = self.needs_animations_update(
+ context,
+ old_values.as_deref(),
+ new_values,
+ pseudo_element,
+ );
+
+ let might_need_transitions_update = self.might_need_transitions_update(
+ context,
+ old_values.as_deref(),
+ new_values,
+ pseudo_element,
+ );
+
+ let mut after_change_style = None;
+ if might_need_transitions_update {
+ after_change_style = self.after_change_style(context, new_values);
+ }
+
+ let key = AnimationSetKey::new(self.as_node().opaque(), pseudo_element);
+ let shared_context = context.shared;
+ let mut animation_set = shared_context
+ .animations
+ .sets
+ .write()
+ .remove(&key)
+ .unwrap_or_default();
+
+ // Starting animations is expensive, because we have to recalculate the style
+ // for all the keyframes. We only want to do this if we think that there's a
+ // chance that the animations really changed.
+ if needs_animations_update {
+ let mut resolver = StyleResolverForElement::new(
+ *self,
+ context,
+ RuleInclusion::All,
+ PseudoElementResolution::IfApplicable,
+ );
+
+ animation_set.update_animations_for_new_style::<Self>(
+ *self,
+ &shared_context,
+ &new_values,
+ &mut resolver,
+ );
+ }
+
+ animation_set.update_transitions_for_new_style(
+ might_need_transitions_update,
+ &shared_context,
+ old_values.as_ref(),
+ after_change_style.as_ref().unwrap_or(new_values),
+ );
+
+ // We clear away any finished transitions, but retain animations, because they
+ // might still be used for proper calculation of `animation-fill-mode`. This
+ // should change the computed values in the style, so we don't need to mark
+ // this set as dirty.
+ animation_set
+ .transitions
+ .retain(|transition| transition.state != AnimationState::Finished);
+
+ // If the ElementAnimationSet is empty, and don't store it in order to
+ // save memory and to avoid extra processing later.
+ let changed_animations = animation_set.dirty;
+ if !animation_set.is_empty() {
+ animation_set.dirty = false;
+ shared_context
+ .animations
+ .sets
+ .write()
+ .insert(key, animation_set);
+ }
+
+ changed_animations
+ }
+
+ /// Computes and applies non-redundant damage.
+ fn accumulate_damage_for(
+ &self,
+ shared_context: &SharedStyleContext,
+ damage: &mut RestyleDamage,
+ old_values: &ComputedValues,
+ new_values: &ComputedValues,
+ pseudo: Option<&PseudoElement>,
+ ) -> ChildRestyleRequirement {
+ debug!("accumulate_damage_for: {:?}", self);
+ debug_assert!(!shared_context
+ .traversal_flags
+ .contains(TraversalFlags::FinalAnimationTraversal));
+
+ let difference = self.compute_style_difference(old_values, new_values, pseudo);
+
+ *damage |= difference.damage;
+
+ debug!(" > style difference: {:?}", difference);
+
+ // We need to cascade the children in order to ensure the correct
+ // propagation of inherited computed value flags.
+ if old_values.flags.maybe_inherited() != new_values.flags.maybe_inherited() {
+ debug!(
+ " > flags changed: {:?} != {:?}",
+ old_values.flags, new_values.flags
+ );
+ return ChildRestyleRequirement::MustCascadeChildren;
+ }
+
+ match difference.change {
+ StyleChange::Unchanged => return ChildRestyleRequirement::CanSkipCascade,
+ StyleChange::Changed { reset_only } => {
+ // If inherited properties changed, the best we can do is
+ // cascade the children.
+ if !reset_only {
+ return ChildRestyleRequirement::MustCascadeChildren;
+ }
+ },
+ }
+
+ let old_display = old_values.clone_display();
+ let new_display = new_values.clone_display();
+
+ if old_display != new_display {
+ // If we used to be a display: none element, and no longer are, our
+ // children need to be restyled because they're unstyled.
+ if old_display == Display::None {
+ return ChildRestyleRequirement::MustCascadeChildren;
+ }
+ // Blockification of children may depend on our display value,
+ // so we need to actually do the recascade. We could potentially
+ // do better, but it doesn't seem worth it.
+ if old_display.is_item_container() != new_display.is_item_container() {
+ return ChildRestyleRequirement::MustCascadeChildren;
+ }
+ // We may also need to blockify and un-blockify descendants if our
+ // display goes from / to display: contents, since the "layout
+ // parent style" changes.
+ if old_display.is_contents() || new_display.is_contents() {
+ return ChildRestyleRequirement::MustCascadeChildren;
+ }
+ // Line break suppression may also be affected if the display
+ // type changes from ruby to non-ruby.
+ #[cfg(feature = "gecko")]
+ {
+ if old_display.is_ruby_type() != new_display.is_ruby_type() {
+ return ChildRestyleRequirement::MustCascadeChildren;
+ }
+ }
+ }
+
+ // Children with justify-items: auto may depend on our
+ // justify-items property value.
+ //
+ // Similarly, we could potentially do better, but this really
+ // seems not common enough to care about.
+ #[cfg(feature = "gecko")]
+ {
+ use crate::values::specified::align::AlignFlags;
+
+ let old_justify_items = old_values.get_position().clone_justify_items();
+ let new_justify_items = new_values.get_position().clone_justify_items();
+
+ let was_legacy_justify_items =
+ old_justify_items.computed.0.contains(AlignFlags::LEGACY);
+
+ let is_legacy_justify_items = new_justify_items.computed.0.contains(AlignFlags::LEGACY);
+
+ if is_legacy_justify_items != was_legacy_justify_items {
+ return ChildRestyleRequirement::MustCascadeChildren;
+ }
+
+ if was_legacy_justify_items && old_justify_items.computed != new_justify_items.computed
+ {
+ return ChildRestyleRequirement::MustCascadeChildren;
+ }
+ }
+
+ #[cfg(feature = "servo")]
+ {
+ // We may need to set or propagate the CAN_BE_FRAGMENTED bit
+ // on our children.
+ if old_values.is_multicol() != new_values.is_multicol() {
+ return ChildRestyleRequirement::MustCascadeChildren;
+ }
+ }
+
+ // We could prove that, if our children don't inherit reset
+ // properties, we can stop the cascade.
+ ChildRestyleRequirement::MustCascadeChildrenIfInheritResetStyle
+ }
+}
+
+impl<E: TElement> PrivateMatchMethods for E {}
+
+/// The public API that elements expose for selector matching.
+pub trait MatchMethods: TElement {
+ /// Returns the closest parent element that doesn't have a display: contents
+ /// style (and thus generates a box).
+ ///
+ /// This is needed to correctly handle blockification of flex and grid
+ /// items.
+ ///
+ /// Returns itself if the element has no parent. In practice this doesn't
+ /// happen because the root element is blockified per spec, but it could
+ /// happen if we decide to not blockify for roots of disconnected subtrees,
+ /// which is a kind of dubious behavior.
+ fn layout_parent(&self) -> Self {
+ let mut current = self.clone();
+ loop {
+ current = match current.traversal_parent() {
+ Some(el) => el,
+ None => return current,
+ };
+
+ let is_display_contents = current
+ .borrow_data()
+ .unwrap()
+ .styles
+ .primary()
+ .is_display_contents();
+
+ if !is_display_contents {
+ return current;
+ }
+ }
+ }
+
+ /// Updates the styles with the new ones, diffs them, and stores the restyle
+ /// damage.
+ fn finish_restyle(
+ &self,
+ context: &mut StyleContext<Self>,
+ data: &mut ElementData,
+ mut new_styles: ResolvedElementStyles,
+ important_rules_changed: bool,
+ ) -> ChildRestyleRequirement {
+ use std::cmp;
+
+ self.process_animations(
+ context,
+ &mut data.styles,
+ &mut new_styles,
+ data.hint,
+ important_rules_changed,
+ );
+
+ // First of all, update the styles.
+ let old_styles = data.set_styles(new_styles);
+
+ let new_primary_style = data.styles.primary.as_ref().unwrap();
+
+ let mut restyle_requirement = ChildRestyleRequirement::CanSkipCascade;
+ let is_root = new_primary_style
+ .flags
+ .contains(ComputedValueFlags::IS_ROOT_ELEMENT_STYLE);
+ let is_container = !new_primary_style
+ .get_box()
+ .clone_container_type()
+ .is_normal();
+ if is_root || is_container {
+ let new_font_size = new_primary_style.get_font().clone_font_size();
+ let old_font_size = old_styles
+ .primary
+ .as_ref()
+ .map(|s| s.get_font().clone_font_size());
+
+ if old_font_size != Some(new_font_size) {
+ if is_root {
+ let device = context.shared.stylist.device();
+ debug_assert!(self.owner_doc_matches_for_testing(device));
+ device.set_root_font_size(new_font_size.computed_size().into());
+ if device.used_root_font_size() {
+ // If the root font-size changed since last time, and something
+ // in the document did use rem units, ensure we recascade the
+ // entire tree.
+ restyle_requirement = ChildRestyleRequirement::MustCascadeDescendants;
+ }
+ }
+
+ if is_container && old_font_size.is_some() {
+ // TODO(emilio): Maybe only do this if we were matched
+ // against relative font sizes?
+ // Also, maybe we should do this as well for font-family /
+ // etc changes (for ex/ch/ic units to work correctly)? We
+ // should probably do the optimization mentioned above if
+ // so.
+ restyle_requirement = ChildRestyleRequirement::MustMatchDescendants;
+ }
+ }
+ }
+
+ if context.shared.stylist.quirks_mode() == QuirksMode::Quirks {
+ if self.is_html_document_body_element() {
+ // NOTE(emilio): We _could_ handle dynamic changes to it if it
+ // changes and before we reach our children the cascade stops,
+ // but we don't track right now whether we use the document body
+ // color, and nobody else handles that properly anyway.
+ let device = context.shared.stylist.device();
+
+ // Needed for the "inherit from body" quirk.
+ let text_color = new_primary_style.get_inherited_text().clone_color();
+ device.set_body_text_color(text_color);
+ }
+ }
+
+ // Don't accumulate damage if we're in the final animation traversal.
+ if context
+ .shared
+ .traversal_flags
+ .contains(TraversalFlags::FinalAnimationTraversal)
+ {
+ return ChildRestyleRequirement::MustCascadeChildren;
+ }
+
+ // Also, don't do anything if there was no style.
+ let old_primary_style = match old_styles.primary {
+ Some(s) => s,
+ None => return ChildRestyleRequirement::MustCascadeChildren,
+ };
+
+ let old_container_type = old_primary_style.clone_container_type();
+ let new_container_type = new_primary_style.clone_container_type();
+ if old_container_type != new_container_type && !new_container_type.is_size_container_type()
+ {
+ // Stopped being a size container. Re-evaluate container queries and units on all our descendants.
+ // Changes into and between different size containment is handled in `UpdateContainerQueryStyles`.
+ restyle_requirement = ChildRestyleRequirement::MustMatchDescendants;
+ } else if old_container_type.is_size_container_type() &&
+ !old_primary_style.is_display_contents() &&
+ new_primary_style.is_display_contents()
+ {
+ // Also re-evaluate when a container gets 'display: contents', since size queries will now evaluate to unknown.
+ // Other displays like 'inline' will keep generating a box, so they are handled in `UpdateContainerQueryStyles`.
+ restyle_requirement = ChildRestyleRequirement::MustMatchDescendants;
+ }
+
+ restyle_requirement = cmp::max(
+ restyle_requirement,
+ self.accumulate_damage_for(
+ context.shared,
+ &mut data.damage,
+ &old_primary_style,
+ new_primary_style,
+ None,
+ ),
+ );
+
+ if data.styles.pseudos.is_empty() && old_styles.pseudos.is_empty() {
+ // This is the common case; no need to examine pseudos here.
+ return restyle_requirement;
+ }
+
+ let pseudo_styles = old_styles
+ .pseudos
+ .as_array()
+ .iter()
+ .zip(data.styles.pseudos.as_array().iter());
+
+ for (i, (old, new)) in pseudo_styles.enumerate() {
+ match (old, new) {
+ (&Some(ref old), &Some(ref new)) => {
+ self.accumulate_damage_for(
+ context.shared,
+ &mut data.damage,
+ old,
+ new,
+ Some(&PseudoElement::from_eager_index(i)),
+ );
+ },
+ (&None, &None) => {},
+ _ => {
+ // It's possible that we're switching from not having
+ // ::before/::after at all to having styles for them but not
+ // actually having a useful pseudo-element. Check for that
+ // case.
+ let pseudo = PseudoElement::from_eager_index(i);
+ let new_pseudo_should_exist =
+ new.as_ref().map_or(false, |s| pseudo.should_exist(s));
+ let old_pseudo_should_exist =
+ old.as_ref().map_or(false, |s| pseudo.should_exist(s));
+ if new_pseudo_should_exist != old_pseudo_should_exist {
+ data.damage |= RestyleDamage::reconstruct();
+ return restyle_requirement;
+ }
+ },
+ }
+ }
+
+ restyle_requirement
+ }
+
+ /// Updates the rule nodes without re-running selector matching, using just
+ /// the rule tree.
+ ///
+ /// Returns true if an !important rule was replaced.
+ fn replace_rules(
+ &self,
+ replacements: RestyleHint,
+ context: &mut StyleContext<Self>,
+ cascade_inputs: &mut ElementCascadeInputs,
+ ) -> bool {
+ let mut result = false;
+ result |= self.replace_rules_internal(
+ replacements,
+ context,
+ CascadeVisitedMode::Unvisited,
+ cascade_inputs,
+ );
+ result |= self.replace_rules_internal(
+ replacements,
+ context,
+ CascadeVisitedMode::Visited,
+ cascade_inputs,
+ );
+ result
+ }
+
+ /// Given the old and new style of this element, and whether it's a
+ /// pseudo-element, compute the restyle damage used to determine which
+ /// kind of layout or painting operations we'll need.
+ fn compute_style_difference(
+ &self,
+ old_values: &ComputedValues,
+ new_values: &ComputedValues,
+ pseudo: Option<&PseudoElement>,
+ ) -> StyleDifference {
+ debug_assert!(pseudo.map_or(true, |p| p.is_eager()));
+ RestyleDamage::compute_style_difference(old_values, new_values)
+ }
+}
+
+impl<E: TElement> MatchMethods for E {}