Adding upstream version 115.8.0esr.upstream/115.8.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 426 insertions, 0 deletions

diff --git a/servo/components/style/rule_tree/mod.rs b/servo/components/style/rule_tree/mod.rs
new file mode 100644
index 0000000000..01510e6207
--- /dev/null
+++ b/servo/components/style/rule_tree/mod.rs
@@ -0,0 +1,426 @@
+/* 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/. */
+
+#![deny(unsafe_code)]
+
+//! The rule tree.
+
+use crate::applicable_declarations::{ApplicableDeclarationList, CascadePriority};
+use crate::properties::{LonghandIdSet, PropertyDeclarationBlock};
+use crate::shared_lock::{Locked, StylesheetGuards};
+use crate::stylesheets::layer_rule::LayerOrder;
+use servo_arc::{Arc, ArcBorrow};
+use smallvec::SmallVec;
+use std::io::{self, Write};
+
+mod core;
+mod level;
+mod map;
+mod source;
+mod unsafe_box;
+
+pub use self::core::{RuleTree, StrongRuleNode};
+pub use self::level::{CascadeLevel, ShadowCascadeOrder};
+pub use self::source::StyleSource;
+
+impl RuleTree {
+    fn dump<W: Write>(&self, guards: &StylesheetGuards, writer: &mut W) {
+        let _ = writeln!(writer, " + RuleTree");
+        self.root().dump(guards, writer, 0);
+    }
+
+    /// Dump the rule tree to stdout.
+    pub fn dump_stdout(&self, guards: &StylesheetGuards) {
+        let mut stdout = io::stdout();
+        self.dump(guards, &mut stdout);
+    }
+
+    /// Inserts the given rules, that must be in proper order by specifity, and
+    /// returns the corresponding rule node representing the last inserted one.
+    ///
+    /// !important rules are detected and inserted into the appropriate position
+    /// in the rule tree. This allows selector matching to ignore importance,
+    /// while still maintaining the appropriate cascade order in the rule tree.
+    pub fn insert_ordered_rules_with_important<'a, I>(
+        &self,
+        iter: I,
+        guards: &StylesheetGuards,
+    ) -> StrongRuleNode
+    where
+        I: Iterator<Item = (StyleSource, CascadePriority)>,
+    {
+        use self::CascadeLevel::*;
+        let mut current = self.root().clone();
+
+        let mut found_important = false;
+
+        let mut important_author = SmallVec::<[(StyleSource, CascadePriority); 4]>::new();
+        let mut important_user = SmallVec::<[(StyleSource, CascadePriority); 4]>::new();
+        let mut important_ua = SmallVec::<[(StyleSource, CascadePriority); 4]>::new();
+        let mut transition = None;
+
+        for (source, priority) in iter {
+            let level = priority.cascade_level();
+            debug_assert!(!level.is_important(), "Important levels handled internally");
+
+            let any_important = {
+                let pdb = source.read(level.guard(guards));
+                pdb.any_important()
+            };
+
+            if any_important {
+                found_important = true;
+                match level {
+                    AuthorNormal { .. } => {
+                        important_author.push((source.clone(), priority.important()))
+                    },
+                    UANormal => important_ua.push((source.clone(), priority.important())),
+                    UserNormal => important_user.push((source.clone(), priority.important())),
+                    _ => {},
+                };
+            }
+
+            // We don't optimize out empty rules, even though we could.
+            //
+            // Inspector relies on every rule being inserted in the normal level
+            // at least once, in order to return the rules with the correct
+            // specificity order.
+            //
+            // TODO(emilio): If we want to apply these optimizations without
+            // breaking inspector's expectations, we'd need to run
+            // selector-matching again at the inspector's request. That may or
+            // may not be a better trade-off.
+            if matches!(level, Transitions) && found_important {
+                // There can be at most one transition, and it will come at
+                // the end of the iterator. Stash it and apply it after
+                // !important rules.
+                debug_assert!(transition.is_none());
+                transition = Some(source);
+            } else {
+                current = current.ensure_child(self.root(), source, priority);
+            }
+        }
+
+        // Early-return in the common case of no !important declarations.
+        if !found_important {
+            return current;
+        }
+
+        // Insert important declarations, in order of increasing importance,
+        // followed by any transition rule.
+        //
+        // Important rules are sorted differently from unimportant ones by
+        // shadow order and cascade order.
+        if !important_author.is_empty() &&
+            important_author.first().unwrap().1 != important_author.last().unwrap().1
+        {
+            // We only need to sort if the important rules come from
+            // different trees, but we need this sort to be stable.
+            //
+            // FIXME(emilio): This could maybe be smarter, probably by chunking
+            // the important rules while inserting, and iterating the outer
+            // chunks in reverse order.
+            //
+            // That is, if we have rules with levels like: -1 -1 -1 0 0 0 1 1 1,
+            // we're really only sorting the chunks, while keeping elements
+            // inside the same chunk already sorted. Seems like we could try to
+            // keep a SmallVec-of-SmallVecs with the chunks and just iterate the
+            // outer in reverse.
+            important_author.sort_by_key(|&(_, priority)| priority);
+        }
+
+        for (source, priority) in important_author.drain(..) {
+            current = current.ensure_child(self.root(), source, priority);
+        }
+
+        for (source, priority) in important_user.drain(..) {
+            current = current.ensure_child(self.root(), source, priority);
+        }
+
+        for (source, priority) in important_ua.drain(..) {
+            current = current.ensure_child(self.root(), source, priority);
+        }
+
+        if let Some(source) = transition {
+            current = current.ensure_child(
+                self.root(),
+                source,
+                CascadePriority::new(Transitions, LayerOrder::root()),
+            );
+        }
+
+        current
+    }
+
+    /// Given a list of applicable declarations, insert the rules and return the
+    /// corresponding rule node.
+    pub fn compute_rule_node(
+        &self,
+        applicable_declarations: &mut ApplicableDeclarationList,
+        guards: &StylesheetGuards,
+    ) -> StrongRuleNode {
+        self.insert_ordered_rules_with_important(
+            applicable_declarations.drain(..).map(|d| d.for_rule_tree()),
+            guards,
+        )
+    }
+
+    /// Insert the given rules, that must be in proper order by specifity, and
+    /// return the corresponding rule node representing the last inserted one.
+    pub fn insert_ordered_rules<'a, I>(&self, iter: I) -> StrongRuleNode
+    where
+        I: Iterator<Item = (StyleSource, CascadePriority)>,
+    {
+        self.insert_ordered_rules_from(self.root().clone(), iter)
+    }
+
+    fn insert_ordered_rules_from<'a, I>(&self, from: StrongRuleNode, iter: I) -> StrongRuleNode
+    where
+        I: Iterator<Item = (StyleSource, CascadePriority)>,
+    {
+        let mut current = from;
+        for (source, priority) in iter {
+            current = current.ensure_child(self.root(), source, priority);
+        }
+        current
+    }
+
+    /// Replaces a rule in a given level (if present) for another rule.
+    ///
+    /// Returns the resulting node that represents the new path, or None if
+    /// the old path is still valid.
+    pub fn update_rule_at_level(
+        &self,
+        level: CascadeLevel,
+        layer_order: LayerOrder,
+        pdb: Option<ArcBorrow<Locked<PropertyDeclarationBlock>>>,
+        path: &StrongRuleNode,
+        guards: &StylesheetGuards,
+        important_rules_changed: &mut bool,
+    ) -> Option<StrongRuleNode> {
+        // TODO(emilio): Being smarter with lifetimes we could avoid a bit of
+        // the refcount churn.
+        let mut current = path.clone();
+        *important_rules_changed = false;
+
+        // First walk up until the first less-or-equally specific rule.
+        let mut children = SmallVec::<[_; 10]>::new();
+        while current.cascade_priority().cascade_level() > level {
+            children.push((
+                current.style_source().unwrap().clone(),
+                current.cascade_priority(),
+            ));
+            current = current.parent().unwrap().clone();
+        }
+
+        // Then remove the one at the level we want to replace, if any.
+        //
+        // NOTE: Here we assume that only one rule can be at the level we're
+        // replacing.
+        //
+        // This is certainly true for HTML style attribute rules, animations and
+        // transitions, but could not be so for SMIL animations, which we'd need
+        // to special-case (isn't hard, it's just about removing the `if` and
+        // special cases, and replacing them for a `while` loop, avoiding the
+        // optimizations).
+        if current.cascade_priority().cascade_level() == level {
+            *important_rules_changed |= level.is_important();
+
+            let current_decls = current.style_source().unwrap().as_declarations();
+
+            // If the only rule at the level we're replacing is exactly the
+            // same as `pdb`, we're done, and `path` is still valid.
+            if let (Some(ref pdb), Some(ref current_decls)) = (pdb, current_decls) {
+                // If the only rule at the level we're replacing is exactly the
+                // same as `pdb`, we're done, and `path` is still valid.
+                //
+                // TODO(emilio): Another potential optimization is the one where
+                // we can just replace the rule at that level for `pdb`, and
+                // then we don't need to re-create the children, and `path` is
+                // also equally valid. This is less likely, and would require an
+                // in-place mutation of the source, which is, at best, fiddly,
+                // so let's skip it for now.
+                let is_here_already = ArcBorrow::ptr_eq(pdb, current_decls);
+                if is_here_already {
+                    debug!("Picking the fast path in rule replacement");
+                    return None;
+                }
+            }
+
+            if current_decls.is_some() {
+                current = current.parent().unwrap().clone();
+            }
+        }
+
+        // Insert the rule if it's relevant at this level in the cascade.
+        //
+        // These optimizations are likely to be important, because the levels
+        // where replacements apply (style and animations) tend to trigger
+        // pretty bad styling cases already.
+        if let Some(pdb) = pdb {
+            if level.is_important() {
+                if pdb.read_with(level.guard(guards)).any_important() {
+                    current = current.ensure_child(
+                        self.root(),
+                        StyleSource::from_declarations(pdb.clone_arc()),
+                        CascadePriority::new(level, layer_order),
+                    );
+                    *important_rules_changed = true;
+                }
+            } else {
+                if pdb.read_with(level.guard(guards)).any_normal() {
+                    current = current.ensure_child(
+                        self.root(),
+                        StyleSource::from_declarations(pdb.clone_arc()),
+                        CascadePriority::new(level, layer_order),
+                    );
+                }
+            }
+        }
+
+        // Now the rule is in the relevant place, push the children as
+        // necessary.
+        let rule = self.insert_ordered_rules_from(current, children.drain(..).rev());
+        Some(rule)
+    }
+
+    /// Returns new rule nodes without Transitions level rule.
+    pub fn remove_transition_rule_if_applicable(&self, path: &StrongRuleNode) -> StrongRuleNode {
+        // Return a clone if there is no transition level.
+        if path.cascade_level() != CascadeLevel::Transitions {
+            return path.clone();
+        }
+
+        path.parent().unwrap().clone()
+    }
+
+    /// Returns new rule node without rules from declarative animations.
+    pub fn remove_animation_rules(&self, path: &StrongRuleNode) -> StrongRuleNode {
+        // Return a clone if there are no animation rules.
+        if !path.has_animation_or_transition_rules() {
+            return path.clone();
+        }
+
+        let iter = path
+            .self_and_ancestors()
+            .take_while(|node| node.cascade_level() >= CascadeLevel::SMILOverride);
+        let mut last = path;
+        let mut children = SmallVec::<[_; 10]>::new();
+        for node in iter {
+            if !node.cascade_level().is_animation() {
+                children.push((
+                    node.style_source().unwrap().clone(),
+                    node.cascade_priority(),
+                ));
+            }
+            last = node;
+        }
+
+        let rule = self
+            .insert_ordered_rules_from(last.parent().unwrap().clone(), children.drain(..).rev());
+        rule
+    }
+
+    /// Returns new rule node by adding animation rules at transition level.
+    /// The additional rules must be appropriate for the transition
+    /// level of the cascade, which is the highest level of the cascade.
+    /// (This is the case for one current caller, the cover rule used
+    /// for CSS transitions.)
+    pub fn add_animation_rules_at_transition_level(
+        &self,
+        path: &StrongRuleNode,
+        pdb: Arc<Locked<PropertyDeclarationBlock>>,
+        guards: &StylesheetGuards,
+    ) -> StrongRuleNode {
+        let mut dummy = false;
+        self.update_rule_at_level(
+            CascadeLevel::Transitions,
+            LayerOrder::root(),
+            Some(pdb.borrow_arc()),
+            path,
+            guards,
+            &mut dummy,
+        )
+        .expect("Should return a valid rule node")
+    }
+}
+
+impl StrongRuleNode {
+    /// Get an iterator for this rule node and its ancestors.
+    pub fn self_and_ancestors(&self) -> SelfAndAncestors {
+        SelfAndAncestors {
+            current: Some(self),
+        }
+    }
+
+    /// Returns true if there is either animation or transition level rule.
+    pub fn has_animation_or_transition_rules(&self) -> bool {
+        self.self_and_ancestors()
+            .take_while(|node| node.cascade_level() >= CascadeLevel::SMILOverride)
+            .any(|node| node.cascade_level().is_animation())
+    }
+
+    /// Get a set of properties whose CascadeLevel are higher than Animations
+    /// but not equal to Transitions.
+    ///
+    /// If there are any custom properties, we set the boolean value of the
+    /// returned tuple to true.
+    pub fn get_properties_overriding_animations(
+        &self,
+        guards: &StylesheetGuards,
+    ) -> (LonghandIdSet, bool) {
+        use crate::properties::PropertyDeclarationId;
+
+        // We want to iterate over cascade levels that override the animations
+        // level, i.e.  !important levels and the transitions level.
+        //
+        // However, we actually want to skip the transitions level because
+        // although it is higher in the cascade than animations, when both
+        // transitions and animations are present for a given element and
+        // property, transitions are suppressed so that they don't actually
+        // override animations.
+        let iter = self
+            .self_and_ancestors()
+            .skip_while(|node| node.cascade_level() == CascadeLevel::Transitions)
+            .take_while(|node| node.cascade_level() > CascadeLevel::Animations);
+        let mut result = (LonghandIdSet::new(), false);
+        for node in iter {
+            let style = node.style_source().unwrap();
+            for (decl, important) in style
+                .read(node.cascade_level().guard(guards))
+                .declaration_importance_iter()
+            {
+                // Although we are only iterating over cascade levels that
+                // override animations, in a given property declaration block we
+                // can have a mixture of !important and non-!important
+                // declarations but only the !important declarations actually
+                // override animations.
+                if important.important() {
+                    match decl.id() {
+                        PropertyDeclarationId::Longhand(id) => result.0.insert(id),
+                        PropertyDeclarationId::Custom(_) => result.1 = true,
+                    }
+                }
+            }
+        }
+        result
+    }
+}
+
+/// An iterator over a rule node and its ancestors.
+#[derive(Clone)]
+pub struct SelfAndAncestors<'a> {
+    current: Option<&'a StrongRuleNode>,
+}
+
+impl<'a> Iterator for SelfAndAncestors<'a> {
+    type Item = &'a StrongRuleNode;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.current.map(|node| {
+            self.current = node.parent();
+            node
+        })
+    }
+}