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style: Implement parsing / selector-matching for :is() and :where().

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This implements the easy / straight-forward parts of the :where / :is
selectors.

The biggest missing piece is to handle properly invalidation when there
are combinators present inside the :where. That's the hard part of this,
actually.

But this is probably worth landing in the interim. This fixes some of
the visitors that were easy to fix.

Differential Revision: https://phabricator.services.mozilla.com/D70788
This commit is contained in:
Emilio Cobos Álvarez 2020-04-17 13:37:59 +00:00
parent 66f14773c6
commit 83ea321096
10 changed files with 338 additions and 223 deletions
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13
components/style/invalidation/element/invalidation_map.rs
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@ -13,7 +13,7 @@ use fallible::FallibleVec;
use hashglobe::FailedAllocationError;
use selectors::attr::NamespaceConstraint;
use selectors::parser::{Combinator, Component};
use selectors::parser::{Selector, SelectorIter, Visit};
use selectors::parser::{Selector, SelectorIter};
use selectors::visitor::SelectorVisitor;
use smallvec::SmallVec;
@ -322,6 +322,17 @@ impl InvalidationMap {
}
/// A struct that collects invalidations for a given compound selector.
///
/// FIXME(emilio, bug 1509418): :where is mishandled, figure out the right way
/// to do invalidation for :where when combinators are inside.
///
/// Simplest feasible idea seems to be: For each :where branch, if there are
/// combinators in the branch, treat as its own selector (basically, call
/// `.note_selector` with the nested selector). That may over-invalidate, but
/// not too much. If there are no combinators, then behave like we do today and
/// use the outer selector as a whole. If we care a lot about that potential
/// over-invalidation where combinators are present then we need more complex
/// data-structures in `Dependency`.
struct CompoundSelectorDependencyCollector<'a> {
/// The state this compound selector is affected by.
state: ElementState,