Bug 1407522 - stylo: Support more selectors in the style sheet invalidator. draft
authorCameron McCormack <cam@mcc.id.au>
Wed, 11 Oct 2017 16:27:49 +0800
changeset 678393 780db7d6daee6da7836e7bc0443f9604a02ca8c0
parent 678362 e765c18d63292cd28b8a1050d3cfbbf4e8e9e68d
child 735321 ae93337617641447772fb284edbec5c0ad99b7e2
push id83915
push userbmo:cam@mcc.id.au
push dateWed, 11 Oct 2017 09:43:07 +0000
bugs1407522
milestone58.0a1
Bug 1407522 - stylo: Support more selectors in the style sheet invalidator. In addition to being able to invalidate just based on local name, this also adds supports invalidating based on selectors with no ancestor combinator in them (resulting in a RESTYLE_SELF for those elements that match). MozReview-Commit-ID: HiD1dRuTAWc
servo/components/style/invalidation/stylesheets.rs
--- a/servo/components/style/invalidation/stylesheets.rs
+++ b/servo/components/style/invalidation/stylesheets.rs
@@ -5,82 +5,105 @@
 //! A collection of invalidations due to changes in which stylesheets affect a
 //! document.
 
 #![deny(unsafe_code)]
 
 use Atom;
 use dom::{TElement, TNode};
 use fnv::FnvHashSet;
-use invalidation::element::restyle_hints::RestyleHint;
+use invalidation::element::restyle_hints::{RESTYLE_SELF, RestyleHint};
 use media_queries::Device;
 use selector_parser::SelectorImpl;
 use selectors::attr::CaseSensitivity;
-use selectors::parser::{Component, Selector};
+use selectors::parser::{Component, LocalName, Selector};
 use shared_lock::SharedRwLockReadGuard;
 use stylesheets::{CssRule, StylesheetInDocument};
 
-/// An invalidation scope represents a kind of subtree that may need to be
-/// restyled.
+/// A style sheet invalidation represents a kind of element or subtree that may
+/// need to be restyled. Whether it represents a whole subtree or just a single
+/// element is determined by whether the invalidation is stored in the
+/// StylesheetInvalidationSet's invalid_scopes or invalid_elements table.
 #[derive(Debug, Eq, Hash, PartialEq)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
-enum InvalidationScope {
-    /// All the descendants of an element with a given id.
+enum Invalidation {
+    /// An element with a given id.
     ID(Atom),
-    /// All the descendants of an element with a given class name.
+    /// An element with a given class name.
     Class(Atom),
+    /// An element with a given local name.
+    LocalName { name: Atom, lower_name: Atom },
 }
 
-impl InvalidationScope {
+impl Invalidation {
     fn is_id(&self) -> bool {
-        matches!(*self, InvalidationScope::ID(..))
+        matches!(*self, Invalidation::ID(..))
+    }
+
+    fn is_id_or_class(&self) -> bool {
+        matches!(*self, Invalidation::ID(..) | Invalidation::Class(..))
     }
 
     fn matches<E>(&self, element: E) -> bool
         where E: TElement,
     {
         match *self {
-            InvalidationScope::Class(ref class) => {
+            Invalidation::Class(ref class) => {
+                // FIXME This should look at the quirks mode of the document to
+                // determine case sensitivity.
                 element.has_class(class, CaseSensitivity::CaseSensitive)
             }
-            InvalidationScope::ID(ref id) => {
+            Invalidation::ID(ref id) => {
                 match element.get_id() {
+                    // FIXME This should look at the quirks mode of the document
+                    // to determine case sensitivity.
                     Some(element_id) => element_id == *id,
                     None => false,
                 }
             }
+            Invalidation::LocalName { ref name, ref lower_name } => {
+                // This could look at the quirks mode of the document, instead
+                // of testing against both names, but it's probably not worth
+                // it.
+                let local_name = element.get_local_name();
+                *local_name == **name || *local_name == **lower_name
+            }
         }
     }
 }
 
 /// A set of invalidations due to stylesheet additions.
 ///
 /// TODO(emilio): We might be able to do the same analysis for media query
 /// changes too (or even selector changes?).
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct StylesheetInvalidationSet {
-    /// The style scopes we know we have to restyle so far.
-    invalid_scopes: FnvHashSet<InvalidationScope>,
-    /// Whether the whole document should be invalid.
+    /// The subtrees we know we have to restyle so far.
+    invalid_scopes: FnvHashSet<Invalidation>,
+    /// The elements we know we have to restyle so far.
+    invalid_elements: FnvHashSet<Invalidation>,
+    /// Whether the whole document should be restyled.
     fully_invalid: bool,
 }
 
 impl StylesheetInvalidationSet {
     /// Create an empty `StylesheetInvalidationSet`.
     pub fn new() -> Self {
         Self {
             invalid_scopes: FnvHashSet::default(),
+            invalid_elements: FnvHashSet::default(),
             fully_invalid: false,
         }
     }
 
     /// Mark the DOM tree styles' as fully invalid.
     pub fn invalidate_fully(&mut self) {
         debug!("StylesheetInvalidationSet::invalidate_fully");
         self.invalid_scopes.clear();
+        self.invalid_elements.clear();
         self.fully_invalid = true;
     }
 
     /// Analyze the given stylesheet, and collect invalidations from their
     /// rules, in order to avoid doing a full restyle when we style the document
     /// next time.
     pub fn collect_invalidations_for<S>(
         &mut self,
@@ -102,21 +125,23 @@ impl StylesheetInvalidationSet {
             debug!(" > Stylesheet was not effective");
             return; // Nothing to do here.
         }
 
         for rule in stylesheet.effective_rules(device, guard) {
             self.collect_invalidations_for_rule(rule, guard);
             if self.fully_invalid {
                 self.invalid_scopes.clear();
+                self.invalid_elements.clear();
                 break;
             }
         }
 
-        debug!(" > resulting invalidations: {:?}", self.invalid_scopes);
+        debug!(" > resulting subtree invalidations: {:?}", self.invalid_scopes);
+        debug!(" > resulting self invalidations: {:?}", self.invalid_elements);
         debug!(" > fully_invalid: {}", self.fully_invalid);
     }
 
     /// Clears the invalidation set, invalidating elements as needed if
     /// `document_element` is provided.
     ///
     /// Returns true if any invalidations ocurred.
     pub fn flush<E>(&mut self, document_element: Option<E>) -> bool
@@ -128,16 +153,17 @@ impl StylesheetInvalidationSet {
         };
         self.clear();
         have_invalidations
     }
 
     /// Clears the invalidation set without processing.
     pub fn clear(&mut self) {
         self.invalid_scopes.clear();
+        self.invalid_elements.clear();
         self.fully_invalid = false;
     }
 
     fn process_invalidations<E>(&self, element: E) -> bool
         where E: TElement,
     {
         {
             let mut data = match element.mutate_data() {
@@ -148,27 +174,27 @@ impl StylesheetInvalidationSet {
             if self.fully_invalid {
                 debug!("process_invalidations: fully_invalid({:?})",
                        element);
                 data.hint.insert(RestyleHint::restyle_subtree());
                 return true;
             }
         }
 
-        if self.invalid_scopes.is_empty() {
+        if self.invalid_scopes.is_empty() && self.invalid_elements.is_empty() {
             debug!("process_invalidations: empty invalidation set");
             return false;
         }
 
         self.process_invalidations_in_subtree(element)
     }
 
-    /// Process style invalidations in a given subtree, that is, look for all
-    /// the relevant scopes in the subtree, and mark as dirty only the relevant
-    /// ones.
+    /// Process style invalidations in a given subtree. This traverses the
+    /// subtree looking for elements that match the invalidations in
+    /// invalid_scopes and invalid_elements.
     ///
     /// Returns whether it invalidated at least one element's style.
     #[allow(unsafe_code)]
     fn process_invalidations_in_subtree<E>(&self, element: E) -> bool
         where E: TElement,
     {
         let mut data = match element.mutate_data() {
             Some(data) => data,
@@ -180,25 +206,38 @@ impl StylesheetInvalidationSet {
         }
 
         if data.hint.contains_subtree() {
             debug!("process_invalidations_in_subtree: {:?} was already invalid",
                    element);
             return false;
         }
 
-        for scope in &self.invalid_scopes {
-            if scope.matches(element) {
-                debug!("process_invalidations_in_subtree: {:?} matched {:?}",
-                       element, scope);
+        for invalidation in &self.invalid_scopes {
+            if invalidation.matches(element) {
+                debug!("process_invalidations_in_subtree: {:?} matched subtree {:?}",
+                       element, invalidation);
                 data.hint.insert(RestyleHint::restyle_subtree());
                 return true;
             }
         }
 
+        let mut self_invalid = false;
+
+        if !data.hint.contains(RESTYLE_SELF) {
+            for invalidation in &self.invalid_elements {
+                if invalidation.matches(element) {
+                    debug!("process_invalidations_in_subtree: {:?} matched self {:?}",
+                           element, invalidation);
+                    data.hint.insert(RESTYLE_SELF);
+                    self_invalid = true;
+                    break;
+                }
+            }
+        }
 
         let mut any_children_invalid = false;
 
         for child in element.as_node().traversal_children() {
             let child = match child.as_element() {
                 Some(e) => e,
                 None => continue,
             };
@@ -207,81 +246,101 @@ impl StylesheetInvalidationSet {
         }
 
         if any_children_invalid {
             debug!("Children of {:?} changed, setting dirty descendants",
                    element);
             unsafe { element.set_dirty_descendants() }
         }
 
-        return any_children_invalid
+        return self_invalid || any_children_invalid
     }
 
     fn scan_component(
         component: &Component<SelectorImpl>,
-        scope: &mut Option<InvalidationScope>)
+        invalidation: &mut Option<Invalidation>)
     {
         match *component {
+            Component::LocalName(LocalName { ref name, ref lower_name }) => {
+                if invalidation.as_ref().map_or(true, |s| !s.is_id_or_class()) {
+                    *invalidation = Some(Invalidation::LocalName {
+                        name: name.clone(),
+                        lower_name: lower_name.clone(),
+                    });
+                }
+            }
             Component::Class(ref class) => {
-                if scope.as_ref().map_or(true, |s| !s.is_id()) {
-                    *scope = Some(InvalidationScope::Class(class.clone()));
+                if invalidation.as_ref().map_or(true, |s| !s.is_id()) {
+                    *invalidation = Some(Invalidation::Class(class.clone()));
                 }
             }
             Component::ID(ref id) => {
-                if scope.is_none() {
-                    *scope = Some(InvalidationScope::ID(id.clone()));
+                if invalidation.is_none() {
+                    *invalidation = Some(Invalidation::ID(id.clone()));
                 }
             }
             _ => {
                 // Ignore everything else, at least for now.
             }
         }
     }
 
-    /// Collect a style scopes for a given selector.
+    /// Collect invalidations for a given selector.
     ///
-    /// We look at the outermost class or id selector to the left of an ancestor
-    /// combinator, in order to restyle only a given subtree.
+    /// We look at the outermost local name, class, or ID selector to the left
+    /// of an ancestor combinator, in order to restyle only a given subtree.
+    ///
+    /// If the selector has no ancestor combinator, then we do the same for
+    /// the only sequence it has, but record it as an element invalidation
+    /// instead of a subtree invalidation.
     ///
-    /// We prefer id scopes to class scopes, and outermost scopes to innermost
-    /// scopes (to reduce the amount of traversal we need to do).
-    fn collect_scopes(&mut self, selector: &Selector<SelectorImpl>) {
-        debug!("StylesheetInvalidationSet::collect_scopes({:?})", selector);
+    /// We prefer IDs to classs, and classes to local names, on the basis
+    /// that the former should be more specific than the latter. We also
+    /// prefer to generate subtree invalidations for the outermost part
+    /// of the selector, to reduce the amount of traversal we need to do
+    /// when flushing invalidations.
+    fn collect_invalidations(&mut self, selector: &Selector<SelectorImpl>) {
+        debug!("StylesheetInvalidationSet::collect_invalidations({:?})", selector);
 
-        let mut scope: Option<InvalidationScope> = None;
+        let mut element_invalidation: Option<Invalidation> = None;
+        let mut subtree_invalidation: Option<Invalidation> = None;
 
-        let mut scan = true;
+        let mut scan_for_element_invalidation = true;
+        let mut scan_for_subtree_invalidation = false;
+
         let mut iter = selector.iter();
 
         loop {
             for component in &mut iter {
-                if scan {
-                    Self::scan_component(component, &mut scope);
+                if scan_for_element_invalidation {
+                    Self::scan_component(component, &mut element_invalidation);
+                } else if scan_for_subtree_invalidation {
+                    Self::scan_component(component, &mut subtree_invalidation);
                 }
             }
             match iter.next_sequence() {
                 None => break,
                 Some(combinator) => {
-                    scan = combinator.is_ancestor();
+                    scan_for_subtree_invalidation = combinator.is_ancestor();
                 }
             }
+            scan_for_element_invalidation = false;
         }
 
-        match scope {
-            Some(s) => {
-                debug!(" > Found scope: {:?}", s);
-                self.invalid_scopes.insert(s);
-            }
-            None => {
-                debug!(" > Scope not found");
-
-                // If we didn't find a scope, any element could match this, so
-                // let's just bail out.
-                self.fully_invalid = true;
-            }
+        if let Some(s) = subtree_invalidation {
+            debug!(" > Found subtree invalidation: {:?}", s);
+            self.invalid_scopes.insert(s);
+        } else if let Some(s) = element_invalidation {
+            debug!(" > Found element invalidation: {:?}", s);
+            self.invalid_elements.insert(s);
+        } else {
+            // The selector was of a form that we can't handle. Any element
+            // could match it, so let's just bail out.
+            debug!(" > Can't handle selector, marking fully invalid");
+            self.fully_invalid = true;
         }
     }
 
     /// Collects invalidations for a given CSS rule.
     fn collect_invalidations_for_rule(
         &mut self,
         rule: &CssRule,
         guard: &SharedRwLockReadGuard)
@@ -289,17 +348,17 @@ impl StylesheetInvalidationSet {
         use stylesheets::CssRule::*;
         debug!("StylesheetInvalidationSet::collect_invalidations_for_rule");
         debug_assert!(!self.fully_invalid, "Not worth to be here!");
 
         match *rule {
             Style(ref lock) => {
                 let style_rule = lock.read_with(guard);
                 for selector in &style_rule.selectors.0 {
-                    self.collect_scopes(selector);
+                    self.collect_invalidations(selector);
                     if self.fully_invalid {
                         return;
                     }
                 }
             }
             Document(..) |
             Namespace(..) |
             Import(..) |