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style: Prevent cousin sharing if we haven't restyled the parents.

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This "fixes" bug 1381821 by disabling the optimization in the cases we can't
prove this is correct. Bug 1387116 tracks fixing the optimization to apply more
broadly.

Bug: 1381821
Reviewed-by: bz
MozReview-Commit-ID: COKdmHHokGx
This commit is contained in:
Emilio Cobos Álvarez 2017-08-03 16:39:33 +02:00
parent 48ea7a29e0
commit 2940270a50
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GPG key ID: 056B727BB9C1027C
1 changed files with 25 additions and 4 deletions
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29
components/style/sharing/checks.rs
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@ -19,17 +19,38 @@ use sharing::{StyleSharingCandidate, StyleSharingTarget};
/// ///
/// This is used to know whether we can share style across cousins (if the two /// This is used to know whether we can share style across cousins (if the two
/// parents have the same style). /// 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 same_computed_values<E>(first: Option<E>, second: Option<E>) -> bool
where E: TElement, where E: TElement,
{ {
let (a, b) = match (first, second) { let (first, second) = match (first, second) {
(Some(f), Some(s)) => (f, s), (Some(f), Some(s)) => (f, s),
_ => return false, _ => return false,
}; };
let eq = Arc::ptr_eq(a.borrow_data().unwrap().styles.primary(), debug_assert_ne!(first, second);
b.borrow_data().unwrap().styles.primary());
eq 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.
//
// Bug 1387116 tracks fixing this, and various solutions are listed there.
if !first_data.restyle.is_restyle() || !second_data.restyle.is_restyle() {
return false;
}
let same_computed_values =
Arc::ptr_eq(first_data.styles.primary(), second_data.styles.primary());
same_computed_values
} }
/// Whether two elements have the same same style attribute (by pointer identity). /// Whether two elements have the same same style attribute (by pointer identity).