Move the layout tree from GC allocation to refcounted ownership so
removed layout and paint subtrees are destroyed synchronously instead
of waiting for the next GC sweep. This dramatically reduces GC memory
usage peaks after layout tree churn and makes it easier for memory use
to fall back after large document updates.
Update layout factories, tree traversal, SVG layout node creation,
paintable back-pointers, and pseudo-element layout links to use RefPtr
ownership.
Make display: contents follow the same shape as Blink and WebKit: the
element itself does not create a layout node, and its children are
flattened into the nearest layout parent. Wrap direct non-whitespace
text in an anonymous inline node when the boxless element contributes
inherited style to that text.
Use an internal inline wrapper for display: contents pseudo-elements
so generated content can still participate in layout, painting, hit
testing, and pseudo-element queries. Keep CSSOM reporting the computed
display value from the pseudo style, not the internal wrapper.
Remove the retained out-of-tree layout node list and its testing hook,
since the flattened model does not need a side owner for boxless
elements. Add coverage for inherited text style, dynamic insertion
order, pseudo-element hit testing, and computed style queries.
Move ComputedProperties and CascadedProperties out of the GC. They no
longer contain strong references to GC-managed data.
Keep computed styles alive from DOM elements and animation updates with
RefPtr. Pass style into layout constructors by reference, since layout
only copies the values it needs while building nodes.
Use GC::Weak for cascade source links, so entries no longer keep the
style declaration or shadow root alive.
Previously, presentational hints bypassed the regular cascade pipeline
and wrote directly into `CascadedProperties` under
`CascadeOrigin::Author`. That meant `var()` substitution and the
invalid-at-computed-value-time fallback had to be duplicated in a
separate per-element pass, which in practice missed the IACVT step and
could leave a `GuaranteedInvalidStyleValue` in the cascaded
properties. This caused a crash in downstream code that assumed the
value had been resolved.
This introduces an `AuthorPresentationalHint` cascade origin and feeds
them through the cascade as normal declarations. This means that
`var()` resolution now happens in only one place.
Resulting in a massive rename across almost everywhere! Alongside the
namespace change, we now have the following names:
* JS::NonnullGCPtr -> GC::Ref
* JS::GCPtr -> GC::Ptr
* JS::HeapFunction -> GC::Function
* JS::CellImpl -> GC::Cell
* JS::Handle -> GC::Root
The StyleResolver can find the specified CSS values for the parent
element via the DOM. Forcing everyone to locate specified values for
their parent was completely unnecessary.
Now that we have RTTI in userspace, we can do away with all this manual
hackery and use dynamic_cast.
We keep the is<T> and downcast<T> helpers since they still provide good
readability improvements. Note that unlike dynamic_cast<T>, downcast<T>
does not fail in a recoverable way, but will assert if the object being
casted is not a T.
Bring the names of various boxes closer to spec language. This should
hopefully make things easier to understand and hack on. :^)
Some notable changes:
- LayoutNode -> Layout::Node
- LayoutBox -> Layout::Box
- LayoutBlock -> Layout::BlockBox
- LayoutReplaced -> Layout::ReplacedBox
- LayoutDocument -> Layout::InitialContainingBlockBox
- LayoutText -> Layout::TextNode
- LayoutInline -> Layout::InlineNode
Note that this is not strictly a "box tree" as we also hang inline/text
nodes in the same tree, and they don't generate boxes. (Instead, they
contribute line box fragments to their containing block!)
Note that these aren't full implementations of the bindings. This
mostly implements the low hanging fruit (namely, basic reflections)
There are some attributes that should be USVString instead of
DOMString. However, USVString is a slightly different definition
of DOMString, so it should suffice for now.
LibWeb keeps growing and the Web namespace is filling up fast.
Let's put DOM stuff into Web::DOM, just like we already started doing
with SVG stuff in Web::SVG.
