diff --git a/servo/components/style/data.rs b/servo/components/style/data.rs
index 8e63fb525013e6d9be67ec1c345b8335ce4037c3..07870fad7a6957a146e52fd0733e42d9cd09f608 100644
--- a/servo/components/style/data.rs
+++ b/servo/components/style/data.rs
@@ -22,8 +22,17 @@ bitflags! {
flags RestyleFlags: 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 we reframed/reconstructed any ancestor or self.
- const ANCESTOR_WAS_RECONSTRUCTED = 1 << 1,
+ const ANCESTOR_WAS_RECONSTRUCTED = 1 << 2,
}
}
@@ -98,14 +107,25 @@ impl RestyleData {
/// to do a post-traversal.
pub fn set_restyled(&mut self) {
self.flags.insert(WAS_RESTYLED);
+ self.flags.remove(TRAVERSED_WITHOUT_STYLING);
}
- /// Mark this element as restyled, which is useful to know whether we need
- /// to do a post-traversal.
+ /// Returns true if this element was restyled.
pub fn is_restyle(&self) -> bool {
self.flags.contains(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(TRAVERSED_WITHOUT_STYLING);
+ }
+
+ /// Returns whether the element was traversed without computing any style for
+ /// it.
+ pub fn traversed_without_styling(&self) -> bool {
+ self.flags.contains(TRAVERSED_WITHOUT_STYLING)
+ }
+
/// Returns whether this element has been part of a restyle.
pub fn contains_restyle_data(&self) -> bool {
self.is_restyle() || !self.hint.is_empty() || !self.damage.is_empty()
diff --git a/servo/components/style/sharing/checks.rs b/servo/components/style/sharing/checks.rs
index 259cadc958ba76f0299f9a4c1ae4161a97041e04..31296aed44677d4e85dcf92e6c770f109706f758 100644
--- a/servo/components/style/sharing/checks.rs
+++ b/servo/components/style/sharing/checks.rs
@@ -13,18 +13,11 @@ use dom::TElement;
use servo_arc::Arc;
use sharing::{StyleSharingCandidate, StyleSharingTarget};
-/// Whether, given two elements, they have pointer-equal computed values.
+/// Whether styles may be shared across the children of the given parent elements.
+/// This is used to share style across cousins.
///
/// Both elements need to be styled already.
-///
-/// This is used to know whether we can share style across cousins (if the two
-/// parents have the same style).
-///
-/// We can only prove that they have the same class list, state, etc if they've
-/// been restyled at the same time, otherwise the invalidation pass could make
-/// them keep the same computed values even though now we wouldn't be able to
-/// prove we match the same selectors.
-pub fn same_computed_values<E>(first: Option<E>, second: Option<E>) -> bool
+pub fn can_share_style_across_parents<E>(first: Option<E>, second: Option<E>) -> bool
where E: TElement,
{
let (first, second) = match (first, second) {
@@ -37,13 +30,18 @@ pub fn same_computed_values<E>(first: Option<E>, second: Option<E>) -> bool
let first_data = first.borrow_data().unwrap();
let second_data = second.borrow_data().unwrap();
- // FIXME(emilio): This check effectively disables cousin style sharing
- // on the initial style.
- //
- // This is pretty bad, se the discussion in bug 1381821 for mor details.
+ // 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 in
+ // 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.
//
- // Bug 1387116 tracks fixing this, and various solutions are listed there.
- if !first_data.restyle.is_restyle() || !second_data.restyle.is_restyle() {
+ // This is a somewhat conservative check. We could tighten it by having the
+ // invalidation logic explicitly flag elements for which it ellided styling.
+ if first_data.restyle.traversed_without_styling() ||
+ second_data.restyle.traversed_without_styling() {
return false;
}
diff --git a/servo/components/style/sharing/mod.rs b/servo/components/style/sharing/mod.rs
index caa6f4afc869c33db63ac8bcaaa09221664fdeb8..27d911362f724e03baf1eca0dfd245050e825346 100644
--- a/servo/components/style/sharing/mod.rs
+++ b/servo/components/style/sharing/mod.rs
@@ -610,13 +610,14 @@ impl<E: TElement> StyleSharingCandidateCache<E> {
}
}
- // Check that we have the same parent, or at least the same pointer
- // identity for parent computed style. The latter check allows us to
- // share style between cousins if the parents shared style.
+ // Check that we have the same parent, or at least that the parents
+ // share styles and permit sharing across their children. The latter
+ // check allows us to share style between cousins if the parents
+ // shared style.
let parent = target.traversal_parent();
let candidate_parent = candidate.element.traversal_parent();
if parent != candidate_parent &&
- !checks::same_computed_values(parent, candidate_parent) {
+ !checks::can_share_style_across_parents(parent, candidate_parent) {
miss!(Parent)
}
diff --git a/servo/components/style/traversal.rs b/servo/components/style/traversal.rs
index 39206303ae3d039029c0cd24b8d5eedfe3da5b7e..cd90f5687532a8bfdd5b03aac92ef3fc6fa480d8 100644
--- a/servo/components/style/traversal.rs
+++ b/servo/components/style/traversal.rs
@@ -528,6 +528,9 @@ where
// evaluate the worklet code. In the case that the size hasn't changed,
// this will result in increased concurrency between script and layout.
notify_paint_worklet(context, data);
+ } else {
+ debug_assert!(data.has_styles());
+ data.restyle.set_traversed_without_styling();
}
// Now that matching and cascading is done, clear the bits corresponding to