Implements the "top layer" concept from "CSS Positioned Layout Module
Level 4" specification.
- The tree builder is modified to ensure that layout nodes created by
top layer elements are children of the viewport.
- Implements missing steps in `showModal()` to add an element top top
layer.
- Implements missing steps in `close()` to remove an element from top
layer.
Further steps could be:
- Add support for `::backdrop` pseudo-element.
- Implement the "inert" concept from HTML spec to block hit-testing
when element from top layer is displayed.
Given a selector like `.foo .bar #baz`, we know that elements with
the class names `foo` and `bar` must be present in the ancestor chain of
the candidate element, or the selector cannot match.
By keeping track of the current ancestor chain during style computation,
and which strings are used in tag names and attribute names, we can do
a quick check before evaluating the selector itself, to see if all the
required ancestors are present.
The way this works:
1. CSS::Selector now has a cache of up to 8 strings that must be present
in the ancestor chain of a matching element. Note that we actually
store string *hashes*, not the strings themselves.
2. When Document performs a recursive style update, we now push and pop
elements to the ancestor chain stack as they are entered and exited.
3. When entering/exiting an ancestor, StyleComputer collects all the
relevant string hashes from that ancestor element and updates a
counting bloom filter.
4. Before evaluating a selector, we first check if any of the hashes
required by the selector are definitely missing from the ancestor
filter. If so, it cannot be a match, and we reject it immediately.
5. Otherwise, we carry on and evaluate the selector as usual.
I originally tried doing this with a HashMap, but we ended up losing
a huge chunk of the time saved to HashMap instead. As it turns out,
a simple counting bloom filter is way better at handling this.
The cost is a flat 8KB per StyleComputer, and since it's a bloom filter,
false positives are a thing.
This is extremely efficient, and allows us to quickly reject the
majority of selectors on many huge websites.
Some example rejection rates:
- https://amazon.com: 77%
- https://github.com/SerenityOS/serenity: 61%
- https://nytimes.com: 57%
- https://store.steampowered.com: 55%
- https://en.wikipedia.org: 45%
- https://youtube.com: 32%
- https://shopify.com: 25%
This also yields a chunky 37% speedup on StyleBench. :^)
Rather than try to lay out masks normally, this updates the TreeBuilder
to create layout nodes for masks as a child of their user (i.e. the
masked element). This allows each use of a mask to be laid out
differently, which makes supporting `maskContentUnits=objectBoundingBox`
fairly easy.
The `SVGFormattingContext` is then updated to lay out masks last (as
their sizing may depend on their parent), and treats them like
viewports.
This is pretty ad-hoc, but the SVG specification does not give any
guidance on how to actually implement this.
All of this error propogation came from a single call to
HashMap::try_ensure_capacity! As part of the ongoing effort to ignore
small allocation failures, lets just assert this works. This has the
nice side-effect of propogating out to a few other classes.
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.
Previously, our code for the fixup of table rows assumed that missing
cells in a table row must be sequential. This may not be true if the
table contains cells have a rowspan greater than one.
Instead of trying to be clever and detaching the paint tree lazily,
just detach all paintables from both DOM and layout tree when building
and committing respectively.
With this change "display: contents" ancestors are not considered as
insertion point for inline nodes similar to how we already ignore them
for non-inline nodes.
Fixes https://github.com/SerenityOS/serenity/issues/22396
The styling of elements using the `use_pseudo_element()` was only
applied on layout. When an element style was recomputed later that
styling was not overruled with the pseudo element selector styles.
This moves the styling override from `TreeBuilder.cpp` to
`StyleComputer.cpp`. Now the styles are always correctly applied.
I also removed the method `property_id_by_index()` because it was
not needed anymore.
Als some calls to `invalidate_layout()` in the Meter, Progress and
Select elements where not needed anymore because the style values
are update on the changing of the style attribute.
This fixes issue #22278.
No functional impact intended. This is just a more complicated way of
writing what we have now.
The goal of this commit is so that we are able to store the 'name' of a
pseudo element for use in serializing 'unknown -webkit-
pseudo-elements', see:
https://www.w3.org/TR/selectors-4/#compat
This is quite awkward, as in pretty much all cases just the selector
type enum is enough, but we will need to cache the name for serializing
these unknown selectors. I can't figure out any reason why we would need
this name anywhere else in the engine, so pretty much everywhere is
still just passing around this raw enum. But this change will allow us
to easily store the name inside of this new struct for when it is needed
for serialization, once those webkit unknown elements are supported by
our engine.
Out-of-flow boxes (floating and absolutely-positioned elements) were
previously collected and put in the anonymous block wrapper as well, but
this actually made hit testing not able to find them, since they were
breaking expectations about tree structure that hit testing relies on.
After this change, we simply let out-of-flow boxes stay in their
original parent, preserving the author's intended box tree structure.
According to the CSS font matching algorithm specification, it is
supposed to be executed for each glyph instead of each text run, as is
currently done. This change partially implements this by having the
font matching algorithm produce a list of fonts against which each
glyph will be tested to find its suitable font.
Now, it becomes possible to have per-glyph fallback fonts: if the
needed glyph is not present in a font, we can check the subsequent
fonts in the list.
493dd5d93c caused the `::before`
pseudo-element node to be inserted before the element's content, which
caused issues with how we determine where to insert inline nodes into
the layout tree. At the time, I noticed the issue with contents of flex
containers, and prevented them from merging into a `::before` box.
However, a similar situation happens when we're not in a flex container,
but the pseudo-element has `display: block`. This commit fixes that
situation by using the same logic in both places, so a similar mistake
can't be made again.
This fixes the tab text being invisible on GitHub project pages. :^)
This makes multiple levels of quote actually use different quotation
marks, instead of always the first available pair of them.
Each Layout::Node remembers what the quote-nesting level was before its
content was evaluated, so that we can re-use this number in
`apply_style()`. This is a bit hacky, since we end up converting the
`content` value into a string twice.
`StyleProperties::content()` now takes an initial quote-nesting level,
and returns the final level after that content.
This allows any effects of `content` (eg quotes and counters) to happen
in the right order.
To make it work there are a couple of other changes needed:
- Skip nodes generated by ::before when constructing button layout.
- When in a flex parent, don't merge an inline text node into a previous
one that is generated from a pseudo-element.
We shouldn't be putting generated pseudo elements inside elements that
can't have children in the first place.
This patch fixes two issues:
- We stop generating pseudo elements for layout nodes that can't have
children anyway.
- We mark Layout::BreakNode as not being able to have children.
When a button should use flex for alignment and also has ::before
and/or ::after, we previously did the following:
1. Prepended/appended the button's children with boxes for
pseudo-elements.
2. Replaced the button's direct children with a flex container that
contains its children.
As a result, the generated boxes for ::before/::after ended up as
children of the generated flex item, instead of being direct children
of the button layout box as they were supposed to be.
This change reverses these steps, ensuring that boxes for
pseudo-elements are generated only after modifications inside the
button layout are completed.
When modifying the button layout during tree building to use flex for
vertical alignment, let's explicitly set the button box's children to
be non-inline. It doesn't make sense to layout the button as an IFC
when its only child is a flex container.
The final used values for these properties is stored in the layout node,
so we need to make sure they are propagated there as well when doing
table box fixup.
Using flex layout inside button solves the issue with wrongly calculated
height when it has: pseudo element and whitespaces inside.
Also using flex instead of a table layout allows for the same vertical
alignment but with fewer layout nodes: a flex container and anonymous
wrapper for content instead of a table wrapper, table, row, and cell.
Before this change, we were creating a new anonymous flex item for every
inline-level child of a flex container, even when we had a sequence of
inline-level children.
The fix here is to simply keep putting things in the last child of the
flex container, if that child is already an anonymous flex item.
We were relying on the table fixup algorithm to insert the missing table
row, which fails to do so when we only have an image in the button.
While that might be a problem with the table fixup algorithm, we should
build a correct layout tree explicitly anyway.
Fixes crashes on GitHub.
Stop worrying about tiny OOMs. Work towards #20449.
While going through these, I also changed the function signature in many
places where returning ThrowCompletionOr<T> is no longer necessary.
This fixes the "last changed" time for files on GitHub. Note that this
appears to be in accordance with the shadow DOM specification, but I
can't find a line that neatly says it. Though on Google's post about
shadow DOM v1 it says:
> "the element's shadow DOM is rendered in place of its children."
https://web.dev/shadowdom-v1/#creating-shadow-dom-for-a-custom-element
When toggling `display: none` on an element, it can go from having a
layout subtree to not having one. In the `none` case, we were previously
leaving stale layout nodes hanging off DOM nodes in the subtree.
These layout nodes could be queried for outdated information and
probably other things that we shouldn't allow.
Fix this by having TreeBuilder prune any old layout nodes hanging off
nodes in a subtree after its subtree root doesn't produce a layout node.
This change makes tree builder omit elements with "display: contents"
from the layout tree during construction. Their child elements are
instead directly appended to the parent element in layout tree.
On style update, we have to preserve the invariant established when we
built the layout tree - some properties are applied to the table wrapper
and the table box values are reset to their initial values.
This also ensures that the containing block of a table box is always a
table wrapper, which isn't the case if we set absolute position on the
box instead of the wrapper.
Fixes#19452.
