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. :^)
Instead of invalidating animated style properties whenever
`Document::update_style()` is called, now we only do that when
animations might have actually progressed. We still have to ensure
animated properties are up-to-date in `update_style()` to ensure that
JS methods can access updated style properties.
Before this change, we ran style and layout updates from both event
loop processing and update timers. This could have caused missed resize
observer updates and unnecessary updating of style or layout more than
once before repaint.
Also, we can now be sure unnecessary style or layout updates won't
happen in `EventLoop::spin_processing_tasks_with_source_until()`.
- Compare only the animated properties
- Clone only the hash map containing animated properties, instead of
the entire StyleProperties.
Reduces `KeyframeEffect::update_style_properties()` from 10% to 3% in
GitHub profiles.
This URL library ends up being a relatively fundamental base library of
the system, as LibCore depends on LibURL.
This change has two main benefits:
* Moving AK back more towards being an agnostic library that can
be used between the kernel and userspace. URL has never really fit
that description - and is not used in the kernel.
* URL _should_ depend on LibUnicode, as it needs punnycode support.
However, it's not really possible to do this inside of AK as it can't
depend on any external library. This change brings us a little closer
to being able to do that, but unfortunately we aren't there quite
yet, as the code generators depend on LibCore.
This commit introduces a WEB_SET_PROTOTYPE_FOR_INTERFACE macro that
caches the interface name in a local static FlyString. This means that
we only pay for FlyString-from-literal lookup once per browser lifetime
instead of every time the interface is instantiated.
Document::navigable() can be unpleasantly slow, since we don't have a
direct link between documents and navigables at the moment. So let's not
call it twice when once is enough.
Patch up existing style properties instead of using the regular style
invalidation path, which requires rule matching for each element in the
invalidated subtree.
- !important properties: this change introduces a flag used to skip the
update of animated properties overridden by !important.
- inherited animated properties: for now, these are invalidated by
traversing animated element's subtree to propagate the update.
- StyleProperties has a separate array for animated properties that
allows the removal animated properties after animation has ended,
without requiring full style invalidation.
Normally, assigning to e.g document.body.onload will forward to
window.onload. However, in a detached DOM tree, there is no associated
window, so we have nowhere to forward to, making this a no-op.
The bulk of this change is making Document::window() return a nullable
pointer, as documents created by DOMParser or DOMImplementation do not
have an associated window object, and so must be able to return null
from here.
Performance handles the document origin time correctly, and prevents
these times from being unusually large. Also initialize the
DocumentTimeline time in the constructor, since these can be created
from JS.
Doing that will allow us to get a list of style sheets for each shadow
root from StyleComputer without having to traverse the entire tree in
upcoming changes.
With this commit, we are finally running animations off of the web
animations spec! A lot of the work StyleComputer is doing is now done
elsewhere. For example, fill-forward animations are handled by
Animation::is_relevant() returning true in the after phase, meaning the
"active_state_if_fill_forward" map is no longer needed.
If a call to `document.write` inserts an incomplete HTML tag, e.g.:
document.write("<p");
we would previously continue parsing the document until we reached a
closing angle bracket. However, the spec states we should stop once we
reach the new insertion point.
Extends event loop processing steps to include gathering and
broadcasting resize observations.
Moves layout updates from Navigable::paint() to event loop processing
steps. This ensures resize observation processing occurs between layout
updates and painting.
Adds the initial implementation for interfaces defined in the
ResizeObserver specification. These interfaces will be used to
construct and send observation events in the upcoming changes.
We now cache potentially named elements on the Document when elements
are inserted and removed. This allows us to do lookup of what names are
supported much faster than if we had to iterate the tree every time.
This first cut doesn't implement the rules for 'exposed' object and
embed elements.
Elements are now collected according to paint order as spec says,
replacing the depth-first traversal of the paint tree with hit-testing
on each box.
This change resolves a FIXME in an existing test and adds a new
previously non-working test.
This API seems to be used by WPT for sending synthetic input events.
Implementing the naive translation of elementFromPoint to the spec steps
for this algorithm turns 4 'tests had errors unexpectedly' and 3 'tests
had timeouts unexpectedly' into 1 pass and 7 'tests had unexpected
subtest results' on the infrastructure/ subdirectory of WPT.
In this commit we have optimized the handling of scroll offsets and
clip rectangles to improve performance. Previously, the process
involved multiple full traversals of the paintable tree before each
repaint, which was highly inefficient, especially on pages with a
large number of paintables. The steps were:
1. Traverse the paintable tree to identify all boxes with scrollable or
clipped overflow.
2. Gather the accumulated scroll offset or clip rectangle for each box.
3. Perform another traversal to apply the corresponding scroll offset
and clip rectangle to each paintable.
To address this, we've adopted a new strategy that separates the
assignment of the scroll/clip frame from the refresh of accumulated
scroll offsets and clip rectangles, thus reducing the workload:
1. Post-relayout: Identify all boxes with overflow and link each
paintable to the state of its containing scroll/clip frame.
2. Pre-repaint: Update the clip rectangle and scroll offset only in the
previously identified boxes.
This adjustment ensures that the costly tree traversals are only
necessary after a relayout, substantially decreasing the amount of work
required before each repaint.
Before this change, `set_needs_to_resolve_paint_only_properties()` was
only called after style invalidation. However, since relayout can be
triggered independently from style invalidation, we need to ensure that
paint-only properties are updated in that case too.
This check has been if (false && stuff) for quite a while, since the
transition to Navigables. No one updates the BrowsingContext's session
history, so the check for it having an about blank document and only an
about blank document is always false.
When an element with an ID is added to or removed from the DOM, or if
an ID is added, removed, or changed, then we must reset the form owner
of all form-associated elements who have a form attribute.
We do this in 2 steps, using the DOM document as the messenger to handle
these changes:
1. All form-associated elements with a form attribute are stored on the
document. If the form attribute is removed, the element is removed
from that list as well.
2. When a DOM element with an ID undergoes any of the aforementioned
changes, it notifies the document of the change. The document then
forwards that change to the stored form-associated elements.
