We can't use a slice anymore, because the input might be the VecDeque from the
sequential traversal, which requires an iterator to handle the ring buffer.
MozReview-Commit-ID: JwH6MtRgMfY
The buggy animation handling isn't a regression, since currently we pass
UnstyledChildrenOnly in those cases, which blocks the animation traversal
in Servo_TraverseSubtree.
In general I really wanted to handle these two paths together. But there's
enough broken with the NewChildren path that I wanted to scope the buginess
as tightly as possible. And I really need to separate the handling here from
StyleDocument() to make the restyle root stuff work.
MozReview-Commit-ID: 9F0mcQl7AAX
Whilst working with variants of the bloom-basic test for Stylo perf
profiling, I noticed that it is easy to cause Firefox to segfault on DOMs
with a depth of more than about 1500 elements. This fix limits the use of
tail recursion to 150 elements. This isn't externally observable to content
-- we're still completely correct, just not using tail recursion any more.
This patch renames TNode::parent_element to traversal_parent, since it returns
the parent from the perspective of traversal (which in Gecko uses the
flattened tree). It also renames TNode::children to traversal_children
for the saem reason.
We keep parent_element and children functions on TNode to use for selector
matching, which must be done on the real DOM tree structure.
The idea is to put the memmoving of the ThreadLocalContext out of line from the point of view of top_down_dom so we don't need to allocate a large chunk of stack space for it.
I wanted to add an environmental variable to disable the style sharing
cache for gecko, but the current pattern involves lazy_static!, which
involves an atomic operation on lookup, which is a bit hot to do each
time we try to share styles. This makes that work happen once per
process.
While we're at it, we also eliminate the 'unknown' dom depth for the
bloom filter. Computing depth has negligible cost relative to the
amount of work we do setting up the bloom filter at a given depth.
Doing it once per traversal should be totally fine.
I originally separated the elimination of unknown dom depth from the
traversal changes, but I got bloom filter crashes on the intermediate
patch, presumably because I didn't properly fix the sequential traversal
for this case. Given that the final state is green, I just decided to
squash and move on.
This way we'll be able to take different paths for the sequential and parallel
traversals in some concrete cases.
This is a preliminar patch to fix bug 1332525.
It turns out that it's problematic to embed ThreadLocalStyleContext within
LayoutContext, because parameterizing the former on TElement (which we do
in the next patch) infects all the traversal stuff with the trait parameters,
which we don't really want.
In general, it probably makes sense to use separate scoped TLS types for
the separate DOM and Flow tree passes, so we can add a different ScopedTLS
type for the Flow pass if we ever need it.
We also reorder the |scope| and |shared| parameters in parallel.rs, because
it aligns more with the order in style/parallel.rs. I did this when I was
adding a TLS parameter to all these functions, which I realized we don't need
for now.
This allows us to get rid of a bunch of lifetimes and simplify a lot of code. It
also lets us get rid of that nasty lifetime transmute, which is awesome.
The situation with thread-local contexts is still suboptimal, but we fix that in
subsequent patches.
I noticed that our current behavior in ContentRangeInserted is incorrect. Unlike
ContentInserted (where this code lived originally), ContentRangeInserted takes a
start and end element. I'm not sure if we ever take that path for new content that
needs style, but it seemed sketchy. And generally, it seems nice to just always
style new content the same way (though we still need to style NAC by the subtree
root, since it hasn't been attached to the parent yet).
For situations where there is indeed only one unstyled child, the traversal
overhead should be neglible, since we special-case the single-element in
parallel.rs to avoid calling into rayon.
Being more explicit about what we want here also makes us more robust against
the other handful of callpaths that can take us into
nsCSSFrameConstructor::{ContentRangeInserted,ContentAppended}. Currently we
can call StyleNewSubtree on an already-styled element via RecreateFramesForContent,
which triggers an assertion in the servo traversal.
MozReview-Commit-ID: DqCGh90deHH
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
