To support visited styles, we match and cascade a separate set of styles any
time we notice that an element has a relevant link.
The visited rules and values are held in `ComputedStyle` alongside the
regular rules and values, which simplifies supporting various APIs like
`cascade_primary_and_pseudos` which expect easy access to previously matched
rules.
To simplify passing the additional values around, an additional reference to the
visited `ComputedValues` is placed inside the regular `ComputedValues`.
MozReview-Commit-ID: 2ebbjcfkfWf
In the case where we process an element which has SMIL animations in normal travesal
the SMIL styles must have been computed in animation-only restyles. So we
have only to pick the computed styles instead of recomputing it.
If we add/remove important rules, we may need to update a list of all important
rules (in Gecko) which overrides animation properties. Therefore, we need to
set a flag if we update the primary rules which includes important ones.
If we have animations on this element, we update its effect properties, and
also send a task to update cascade results.
Calling get_properties_overriding_animations() might cases some impact
on performance because we need to walk the rule tree, so if possible, we could
just store this set into TNode to avoid finding the properties for both old
and new rules each time. This could be a future work if necessary.
I've chosen this approach mainly because there's no other good way to guarantee
the model is correct than holding the snapshots alive until a style refresh.
What I tried before this (storing them in a sort of "immutable element data") is
a pain, since we call into style from the frame constructor and other content
notifications, which makes keeping track of which snapshots should be cleared an
which shouldn't an insane task.
Ideally we'd have a single entry-point for style, but that's not the case right
now, and changing that requires pretty non-trivial changes to the frame
constructor.
MozReview-Commit-ID: FF1KWZv2iBM
Signed-off-by: Emilio Cobos Álvarez <emilio@crisal.io>
This is necessary in order to make the computation of eager pseudos depend on
the primary ComputedValues, which we want to do for ::first-letter/::first-line.
This also fixes a bug where the behavior of EagerPseudoStyles::is_empty was reversed
in both the implementation and the callsite.
MozReview-Commit-ID: EXBxclyHWXu
The primary idea of this patch is to ditch the rigid enum of Previous/Current
styles, and replace it with a series of indicators for the various types of
work that needs to be performed (expanding snapshots, rematching, recascading,
and damage processing). This loses us a little bit of sanity checking (since
the up-to-date-ness of our style is no longer baked into the type system), but
gives us a lot more flexibility that we'll need going forward (especially when
we separate matching from cascading). We also eliminate get_styling_mode in
favor of a method on the traversal.
This patch does a few other things as ridealongs:
* Temporarily eliminates the handling for transfering ownership of styles to the
frame. We'll need this again at some point, but for now it's causing too much
complexity for a half-implemented feature.
* Ditches TRestyleDamage, which is no longer necessary post-crate-merge, and is
a constant source of compilation failures from either needing to be imported
or being unnecessarily imported (which varies between gecko and servo).
* Expands Snapshots for the traversal root, which was missing before.
* Fixes up the skip_root stuff to avoid visiting the skipped root.
* Unifies parallel traversal and avoids spawning for a single work item.
* Adds an explicit pre_traverse step do any pre-processing and determine whether
we need to traverse at all.
MozReview-Commit-ID: IKhLAkAigXE
This patch introduces infrastructure for the rule tree, and constructs it.
We don't use it yet, nor have good heuristics for GC'ing it, but this should not
happen anymore once we store the rule node reference in the node.
I haven't messed up with memory orders because I want to do a try run with it,
then mess with them.
Take down the ApplicableDeclarationsCache, use the rule tree for doing the cascade.
We don't need this for Gecko, and it's hard to implement in that case because
there's nowhere obvious to put it (we don't plan to create TSDs for non-dirty
nodes, and non-dirty nodes can have dirty children which require the
children_to_process atomic). There are various solutions here, but punting is
the easiest.
We'll need to rethink this if/when we need to do a bottom-up traversal for
Gecko.
This commit adds hooks to the Servo style traversal to avoid traversing all the
DOM for every restyle. Additionally it changes the behavior of the dirty flag to
be propagated top down, to prevent extra overhead when an element is dirtied.
This commit doesn't aim to change the behavior on Servo just yet, since Servo
might rely on a full bottom up reconstruction of the flows. I'll need to double
check and implement that separately.
This commit refactors the style crate to be completely independent of
the actual implementation and pseudo-elements supported.
This also adds a gecko backend which introduces parsing for the
anonymous box pseudo-elements[1], although there's still no way of
querying them.
https://mxr.mozilla.org/mozilla-central/source/layout/style/nsCSSAnonBoxList.h
