Kinda tricky because :host only matches rules on the shadow root where the rules
come from. So we need to be careful during invalidation and style sharing.
I didn't use the non_ts_pseudo_class_list bits because as soon as we implement
the :host(..) bits we're going to need to special-case it anyway.
The general schema is the following:
* Rightmost featureless :host selectors are handled inserting them in the
host_rules hashmap. Note that we only insert featureless stuff there. We
could insert all of them and just filter during matching, but that's slightly
annoying.
* The other selectors, like non-featureless :host or what not, are added to the
normal cascade data. This is harmless, since the shadow host rules are never
matched against the host, so we know they'll just never match, and avoids
adding more special-cases.
* Featureless :host selectors to the left of a combinator are handled during
matching, in the special-case of next_element_for_combinator in selectors.
This prevents this from being more invasive, and keeps the usual fast path
slim, but it's a bit hard to match the spec and the implementation.
We could keep a copy of the SelectorIter instead in the matching context to
make the handling of featureless-ness explicit in match_non_ts_pseudo_class,
but we'd still need the special-case anyway, so I'm not fond of it.
* We take advantage of one thing that makes this sound. As you may have
noticed, if you had `root` element which is a ShadowRoot, and you matched
something like `div:host` against it, using a MatchingContext with
current_host == root, we'd incorrectly report a match. But this is impossible
due to the following constraints:
* Shadow root rules aren't matched against the host during styling (except
these featureless selectors).
* DOM APIs' current_host needs to be the _containing_ host, not the element
itself if you're a Shadow host.
Bug: 992245
Reviewed-by: xidorn
MozReview-Commit-ID: KayYNfTXb5h
It used to be the case that MatchingContext was immutable and thus we didn't
care to have accessors.
This is no longer true, so let's make this code a bit nicer.
Right now we go through a lot of hoops to see if we ever see a relevant link.
However, that information is not needed: if the element is a link, we'll always
need to compute its visited style because its its own relevant link.
If the element inherits from a link, we need to also compute the visited style
anyway.
So the "has a relevant link been found" is pretty useless when we know what are
we inheriting from.
The branches at the beginning of matches_complex_selector_internal were
affecting performance, and there are no good reasons to keep them.
I've verified that this passes all the visited tests in mozilla central, and
that the test-cases too-flaky to be landed still pass.
This type is a lot of complexity related to a very specific thing such as the
hover and active quirk.
Instead of that, move `nesting_level` to `MatchingContext`, and simplify all
this computing whether the quirk applies upfront, for each complex selector we
test.
This is less error-prone, and also allows simplifying more stuff in a bit.
Otherwise, tests like the following fail, given we always match as unvisited,
and we'd never mark the link as needing invalidation.
<!doctype html>
<style>
a {
color: red !important;
}
.foo :visited {
color: green !important;
}
</style>
<div>
<a href="https://google.es">visit me</a>
<button onclick="this.parentNode.className = 'foo'">Then click me</button>
</div>
Bug: 1368240
MozReview-Commit-ID: LDv6S28c4ju
