stylo: Avoid restyling the whole document when adding stylesheets.

components/style/data.rs

@@ -388,6 +388,11 @@ impl StoredRestyleHint {
         self.0.insert(other.0)
     }
 
+    /// Contains whether the whole subtree is invalid.
+    pub fn contains_subtree(&self) -> bool {
+        self.0.contains(&RestyleHint::subtree())
+    }
+
     /// Insert another restyle hint, effectively resulting in the union of both.
     pub fn insert_from(&mut self, other: &Self) {
         self.0.insert_from(&other.0)

components/style/gecko/data.rs

@@ -6,8 +6,10 @@
 
 use Atom;
 use atomic_refcell::{AtomicRef, AtomicRefCell, AtomicRefMut};
+use dom::TElement;
 use fnv::FnvHashMap;
 use gecko::rules::{CounterStyleRule, FontFaceRule};
+use gecko::wrapper::GeckoElement;
 use gecko_bindings::bindings::RawServoStyleSet;
 use gecko_bindings::structs::RawGeckoPresContextOwned;
 use gecko_bindings::structs::nsIDocument;
@@ -72,13 +74,17 @@ impl PerDocumentStyleDataImpl {
     ///
     /// Implies also a stylesheet flush.
     pub fn reset_device(&mut self, guard: &SharedRwLockReadGuard) {
-        Arc::get_mut(self.stylist.device_mut()).unwrap().reset();
+        self.stylist.device_mut().reset();
         self.stylesheets.force_dirty();
-        self.flush_stylesheets(guard);
+        self.flush_stylesheets::<GeckoElement>(guard, None);
     }
 
     /// Recreate the style data if the stylesheets have changed.
-    pub fn flush_stylesheets(&mut self, guard: &SharedRwLockReadGuard) {
+    pub fn flush_stylesheets<E>(&mut self,
+                                guard: &SharedRwLockReadGuard,
+                                document_element: Option<E>)
+        where E: TElement,
+    {
         if !self.stylesheets.has_changed() {
             return;
         }
@@ -90,7 +96,8 @@ impl PerDocumentStyleDataImpl {
 
         let author_style_disabled = self.stylesheets.author_style_disabled();
         self.stylist.clear();
-        self.stylist.rebuild(self.stylesheets.flush(),
+        let iter = self.stylesheets.flush(document_element);
+        self.stylist.rebuild(iter,
                              &StylesheetGuards::same(guard),
                              /* ua_sheets = */ None,
                              /* stylesheets_changed = */ true,

components/style/gecko/generated/bindings.rs

@@ -1804,7 +1804,9 @@ extern "C" {
                                                  before_unique_id: u64);
 }
 extern "C" {
-    pub fn Servo_StyleSet_FlushStyleSheets(set: RawServoStyleSetBorrowed);
+    pub fn Servo_StyleSet_FlushStyleSheets(set: RawServoStyleSetBorrowed,
+                                           doc_elem:
+                                               RawGeckoElementBorrowedOrNull);
 }
 extern "C" {
     pub fn Servo_StyleSet_NoteStyleSheetsChanged(set:

components/style/invalidation/mod.rs

@@ -0,0 +1,296 @@
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+//! A collection of invalidations due to changes in which stylesheets affect a
+//! document.
+
+#![deny(unsafe_code)]
+
+use Atom;
+use data::StoredRestyleHint;
+use dom::{TElement, TNode};
+use fnv::FnvHashSet;
+use selector_parser::SelectorImpl;
+use selectors::parser::{Component, Selector};
+use shared_lock::SharedRwLockReadGuard;
+use stylesheets::{CssRule, Stylesheet};
+use stylist::Stylist;
+
+/// An invalidation scope represents a kind of subtree that may need to be
+/// restyled.
+#[derive(Debug, Hash, Eq, PartialEq)]
+enum InvalidationScope {
+    /// All the descendants of an element with a given id.
+    ID(Atom),
+    /// All the descendants of an element with a given class name.
+    Class(Atom),
+}
+
+impl InvalidationScope {
+    fn is_id(&self) -> bool {
+        matches!(*self, InvalidationScope::ID(..))
+    }
+
+    fn matches<E>(&self, element: E) -> bool
+        where E: TElement,
+    {
+        match *self {
+            InvalidationScope::Class(ref class) => {
+                element.has_class(class)
+            }
+            InvalidationScope::ID(ref id) => {
+                match element.get_id() {
+                    Some(element_id) => element_id == *id,
+                    None => false,
+                }
+            }
+        }
+    }
+}
+
+/// A set of invalidations due to stylesheet additions.
+///
+/// TODO(emilio): We might be able to do the same analysis for removals and
+/// media query changes too?
+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.
+    fully_invalid: bool,
+}
+
+impl StylesheetInvalidationSet {
+    /// Create an empty `StylesheetInvalidationSet`.
+    pub fn new() -> Self {
+        Self {
+            invalid_scopes: 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.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(
+        &mut self,
+        stylist: &Stylist,
+        stylesheet: &Stylesheet,
+        guard: &SharedRwLockReadGuard)
+    {
+        debug!("StylesheetInvalidationSet::collect_invalidations_for");
+        if self.fully_invalid {
+            debug!(" > Fully invalid already");
+            return;
+        }
+
+        if stylesheet.disabled() ||
+           !stylesheet.is_effective_for_device(stylist.device(), guard) {
+            debug!(" > Stylesheet was not effective");
+            return; // Nothing to do here.
+        }
+
+        for rule in stylesheet.effective_rules(stylist.device(), guard) {
+            self.collect_invalidations_for_rule(rule, guard);
+            if self.fully_invalid {
+                self.invalid_scopes.clear();
+                break;
+            }
+        }
+
+        debug!(" > resulting invalidations: {:?}", self.invalid_scopes);
+        debug!(" > fully_invalid: {}", self.fully_invalid);
+    }
+
+    /// Clears the invalidation set, invalidating elements as needed if
+    /// `document_element` is provided.
+    pub fn flush<E>(&mut self, document_element: Option<E>)
+        where E: TElement,
+    {
+        if let Some(e) = document_element {
+            self.process_invalidations_in_subtree(e);
+        }
+        self.invalid_scopes.clear();
+        self.fully_invalid = false;
+    }
+
+    /// 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.
+    ///
+    /// 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,
+            None => return false,
+        };
+
+        if !data.has_styles() {
+            return false;
+        }
+
+        if let Some(ref r) = data.get_restyle() {
+            if r.hint.contains_subtree() {
+                debug!("process_invalidations_in_subtree: {:?} was already invalid",
+                       element);
+                return false;
+            }
+        }
+
+        if self.fully_invalid {
+            debug!("process_invalidations_in_subtree: fully_invalid({:?})",
+                   element);
+            data.ensure_restyle().hint.insert(StoredRestyleHint::subtree());
+            return true;
+        }
+
+        for scope in &self.invalid_scopes {
+            if scope.matches(element) {
+                debug!("process_invalidations_in_subtree: {:?} matched {:?}",
+                       element, scope);
+                data.ensure_restyle().hint.insert(StoredRestyleHint::subtree());
+                return true;
+            }
+        }
+
+
+        let mut any_children_invalid = false;
+
+        for child in element.as_node().children() {
+            let child = match child.as_element() {
+                Some(e) => e,
+                None => continue,
+            };
+
+            any_children_invalid |= self.process_invalidations_in_subtree(child);
+        }
+
+        if any_children_invalid {
+            debug!("Children of {:?} changed, setting dirty descendants",
+                   element);
+            unsafe { element.set_dirty_descendants() }
+        }
+
+        return any_children_invalid
+    }
+
+    fn scan_component(
+        component: &Component<SelectorImpl>,
+        scope: &mut Option<InvalidationScope>)
+    {
+        match *component {
+            Component::Class(ref class) => {
+                if scope.as_ref().map_or(true, |s| !s.is_id()) {
+                    *scope = Some(InvalidationScope::Class(class.clone()));
+                }
+            }
+            Component::ID(ref id) => {
+                if scope.is_none() {
+                    *scope = Some(InvalidationScope::ID(id.clone()));
+                }
+            }
+            _ => {
+                // Ignore everything else, at least for now.
+            }
+        }
+    }
+
+    /// Collect a style scopes 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 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);
+
+        let mut scope: Option<InvalidationScope> = None;
+
+        let mut scan = true;
+        let mut iter = selector.inner.complex.iter();
+
+        loop {
+            for component in &mut iter {
+                if scan {
+                    Self::scan_component(component, &mut scope);
+                }
+            }
+            match iter.next_sequence() {
+                None => break,
+                Some(combinator) => {
+                    scan = combinator.is_ancestor();
+                }
+            }
+        }
+
+        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;
+            }
+        }
+    }
+
+    /// Collects invalidations for a given CSS rule.
+    fn collect_invalidations_for_rule(
+        &mut self,
+        rule: &CssRule,
+        guard: &SharedRwLockReadGuard)
+    {
+        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);
+                    if self.fully_invalid {
+                        return;
+                    }
+                }
+            }
+            Document(..) |
+            Namespace(..) |
+            Import(..) |
+            Media(..) |
+            Supports(..) => {
+                // Do nothing, relevant nested rules are visited as part of the
+                // iteration.
+            }
+            FontFace(..) |
+            CounterStyle(..) |
+            Keyframes(..) |
+            Page(..) |
+            Viewport(..) => {
+                debug!(" > Found unsupported rule, marking the whole subtree \
+                       invalid.");
+
+                // TODO(emilio): Can we do better here?
+                //
+                // At least in `@page`, we could check the relevant media, I
+                // guess.
+                self.fully_invalid = true;
+            }
+        }
+    }
+}

components/style/lib.rs

@@ -110,6 +110,7 @@ pub mod font_face;
 pub mod font_metrics;
 #[cfg(feature = "gecko")] #[allow(unsafe_code)] pub mod gecko;
 #[cfg(feature = "gecko")] #[allow(unsafe_code)] pub mod gecko_bindings;
+pub mod invalidation;
 pub mod keyframes;
 #[allow(missing_docs)] // TODO.
 pub mod logical_geometry;

components/style/restyle_hints.rs

@@ -368,7 +368,7 @@ impl RestyleHint {
     /// Returns whether this `RestyleHint` represents at least as much restyle
     /// work as the specified one.
     #[inline]
-    pub fn contains(&mut self, other: &Self) -> bool {
+    pub fn contains(&self, other: &Self) -> bool {
         self.match_under_self.contains(other.match_under_self) &&
         (self.match_later_siblings & other.match_later_siblings) == other.match_later_siblings &&
         self.replacements.contains(other.replacements)