Remove unused code (4/4)
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Fourth and final PR in a series of PRs to remove unused/dead code from servo, powered by an (upcoming) tool of mine. Please take a look and tell me if you want to keep something.
* First PR: #23477
* Second PR: #23498
* Third PR: #23499
Shortstat of the combined PR series:
```
47 files changed, 7 insertions(+), 805 deletions(-)
```
---
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We already avoid putting styles in the shared style cache for an element that
has animations[1] but if we are doing the initial style of two siblings where
the _second_ has animations applied, there is nothing to stop us from trying to
share with the first (un-animated) element. This patch adds a check to prevent
sharing in that case since sharing style between animated elements is unsound
for the reasons described in [1].
A number of tests including:
testing/web-platform/tests/web-animations/animation-model/animation-types/visibility.html
will fail without this fix once we remove the style flush from
KeyframeEffect::SetKeyframes later in this patch series.
[1] https://searchfox.org/mozilla-central/rev/6e3cc153566f5f288ae768a2172385b8436d61dd/servo/components/style/sharing/mod.rs#597
Differential Revision: https://phabricator.services.mozilla.com/D18913
We were spuriously reframing the <shadow> because it initially shared style with
the <br>, which ended up being display: none, while the <shadow> should've been
display: contents from the beginning.
lookup_by_rules seems pretty prone to obscure bugs, and also it's pretty
complex... Probably we should try to get rid of it, I'm unconvinced that it's
worth it.
Even with that, in a normal restyle the <details> wouldn't have ended up with a
style. It of course never had it before the reframe because the <shadow> was
display: none, but that doesn't mean it shouldn't have gotten one, since we
detected we needed to go through kids in:
https://searchfox.org/mozilla-central/rev/6eea08365e7386a2b81c044e7cc8a3daa51d8754/servo/components/style/matching.rs#500
That code did happen, but since it's an animation-only restyle, we don't look at
unstyled stuff.
That looks somewhat fishy, but I guess for now it's fine as long as display
isn't animatable.
Bug: 1469076
Reviewed-by: heycam
MozReview-Commit-ID: B6NMSTNOKgK
Currently, NAC always inherits from the closest non-NAC ancestor element,
regardless of whether it is for an element-backed pseudo or not.
This patch changes the inheritance so that for element-backed pseudos, we
inherit from the closest native anonymous root's parent, and for other NAC we
inherit from the parent.
This prevents the following two issues and allows us to remove the
NODE_IS_NATIVE_ANONYMOUS flag:
* Avoiding inheriting from the non-NAC ancestor in XBL bindings bound to NAC.
- This is no longer a problem since we apply the rule only if we're a
pseudo-element, and all pseudo-elements are in native anonymous subtrees.
- This also allows to remove the hack that propagates the
NODE_IS_NATIVE_ANONYMOUS flag from the ::cue pseudo-element from
BindToTree.
* Inheriting from the wrong thing if we're a nested NAC subtree.
- We no longer look past our NAC subtree, with the exception of
::-moz-number-text's pseudo-elements, for which we do want to propagate
::placeholder to.
A few rules from forms.css have been modified because they're useless or needed
to propagate stuff to the anonymous form control in input[type="number"] which
previously inherited from the input itself.
Bug: 1460382
Reviewed-by: heycam
MozReview-Commit-ID: IDKYt3EJtSH
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
If two elements are assigned to different slots, even within the same shadow
root, they could match different rules, due to the slot being assigned to yet
another slot in another shadow root.
MozReview-Commit-ID: CfZJCVxIQzM
It's easy to construct examples where not inserting in those cases causes performance
to get worse (for example, any long list of siblings that match the same selectors
while having some non-effectual differences in LocalName/Class/Id/etc). And the LRU
nature of the cache already does the right thing of pruning non-useful entries.
Fixing this causes several hundred more sharing hits on wikipedia.
MozReview-Commit-ID: L7W8vcMnHaq
This will make the linear probing faster. If we end up implementing the two-tier
cache setup, this code will be unnecessary and can go away.
MozReview-Commit-ID: BRfV5ump34n
