InlinePaintable was an ad-hoc paintable type required to support the
fragmentation of inline nodes across multiple lines. It existed because
there was no way to associate multiple paintables with a single layout
node. This resulted in a lot of duplicated code between PaintableBox and
InlinePaintable. For example, most of the CSS properties like
background, border, shadows, etc. and hit-testing are almost identical
for both of them. However, the code had to be duplicated to account for
the fact that InlinePaintable creates a box for each line. And we had
quite many places that operate on paintables with a code like:
```
if (box.is_paintable_box()) {
// do something
} else (box.is_inline_paintable()) {
// do exactly the same as for paintable box but using InlinePaintable
}
```
This change replaces the usage of `InlinePaintable` with
`PaintableWithLines` created for each line, which is now possible
because we support having multiple paintables per layout node. By doing
that, we remove lots of duplicated code and bring our implementation
closer to the spec.
CSS fragmentation implies 1:N relationship between layout nodes and
paintables. This change is a preparation for implementation of inline
fragmentation where InlinePaintable will be replaced with
PaintableWithLines corresponding to each line.
Prior to this change, SVGs were following the CSS painting order, which
means SVG boxes could have established stacking context and be sorted by
z-index. There is a section in the spec that defines what kind of SVG
boxes should create a stacking context
https://www.w3.org/TR/SVG2/render.html#EstablishingStackingContex
Although this spec is marked as a draft and rendering order described in
this spec does not match what other engines do.
This spec issue comment has a good summary of what other engines
actually do regarding painting order
https://github.com/w3c/svgwg/issues/264#issuecomment-246432360
"as long as you're relying solely on the default z-index (which SVG1
does, by definition), nothing ever changes order when you apply
opacity/filter/etc".
This change aligns our implementation with other engines by forbidding
SVGs to create a formatting context and painting them in order they are
defined in tree tree.
Sticky positioning is implemented by modifying the algorithm for
assigning and refreshing scroll frames. Now, elements with
"position: sticky" are assigned their own scroll frame, and their
position is refreshed independently from regular scroll boxes.
Refreshing the scroll offsets for sticky boxes does not require display
list invalidation.
A separate hash map is used for the scroll frames of sticky boxes. This
is necessary because a single paintable box can have two scroll frames
if it 1) has "position: sticky" and 2) contains scrollable overflow.
For a long time, we've used two terms, inconsistently:
- "Identifier" is a spec term, but refers to a sequence of alphanumeric
characters, which may or may not be a keyword. (Keywords are a
subset of all identifiers.)
- "ValueID" is entirely non-spec, and is directly called a "keyword" in
the CSS specs.
So to avoid confusion as much as possible, let's align with the spec
terminology. I've attempted to change variable names as well, but
obviously we use Keywords in a lot of places in LibWeb and so I may
have missed some.
One exception is that I've not renamed "valid-identifiers" in
Properties.json... I'd like to combine that and the "valid-types" array
together eventually, so there's no benefit to doing an extra rename
now.
These control the state of CSS counters.
Parsing code for `reversed(counter-name)` is implemented, but disabled
for now until we are able to resolve values for those.
This seems to have been required when pseudo-elements were first
implemented, but has since become unused. It's also awkward because we
don't have access to the DOM Element and its CountersSet at this point.
So, let's remove it.
For reference, Chrome&Firefox both return the computed value for
`content: counter(foo)` as `counter(foo)`, not as the computed string.
So not computing it here seems like the intended behaviour.
When both insets in a given axis are auto, we should use the static
position for absolutely positioned elements.
By doing this correctly, we exposed a bunch of other small bugs which
had to be fixed to compensate for new test failures. Those fixes are
included here as well:
- Don't apply margins twice.
- Compute the static position containing block chain correctly.
This makes https://brave.com/ look much better. :^)
A bunch of this is leftover from pre porting over to new AK::String.
For example, for functions which previously took a ByteString const&
now accepting a StringView.
This allows positioning a child SVG relative to its parent SVG.
Note: These have been implemented as CSS properties as in SVG 2, these
are geometry properties that can be used in CSS (see
https://www.w3.org/TR/SVG/geometry.html), but there is not much browser
support for this. It is nicer to implement than the ad-hoc SVG
attribute parsing though, so I feel it may make sense to port the rest
of the attributes specified here (which should fix some issues with
viewport relative sizes).
This makes them cheap to move around, since we can store them in a
NonnullOwnPtr instead of memcopying 2584(!) bytes.
Drastically reduces the chance of stack overflow while building the
layout tree for deeply nested DOMs (since tree building was putting
these things on the stack).
This change also exposed a completely unnecessary ComputedValues deep
copy in block layout.
The paintable tree structure more closely matches the painting order
when fragments are owned by corresponding inline paintables. This
change does not affect the layout tree, as it is more convenient for
layout purposes to have all fragments owned by a block container in
one place.
Additionally, this improves performance significantly on pages with
many fragments, as we no longer have to walk the ancestor chain up
to the closest block container to determine if a fragment belongs
to an inline paintable.
