Async scrolling metadata recording checks many paintable nodes for
blocking wheel listeners while building a display list. The helper used
EventTarget::event_listener_list(), which returns a snapshot backed by
GC::Root entries, so the hot paint path allocated and destroyed roots
just to answer a boolean query.
Add a non-allocating EventTarget predicate that scans the stored
listener references directly, and use it from async scrolling metadata
recording. Event dispatch still uses event_listener_list() so it keeps
the required snapshot semantics.
Use compositor hit-test commands in the display list to rebuild async
wheel targets, and serialize the async scroll metadata needed to
reconstruct AsyncScrollingState from the same display-list snapshot.
Driving the async scroll tree off the display list rather than a
separately collected tree has a few benefits:
- No additional full paintable tree traversal is required, since the
information needed by the compositor is gathered while recording
the display list.
- The display list is already serializable, so the async scroll tree
no longer needs its own serialization path.
- It is more debuggable, as the existing display list dump now also
covers the data used to reconstruct the async scroll tree.
- In the future we will want to include other areas that can
interfere with hit-testing; recording them during display list
construction makes it straightforward to preserve a hit-testing
order that matches painting order.
Previously we were inconsistent by generating code for enum definitions
but not generating code for dictionaries. With future changes to the
IDL generator to expose helpers to convert to and from IDL values
this produced circular depdendencies. To solve this problem, also
generate the dictionary definitions in bindings headers.
We weren't doing this before either, but through a slightly sneaky
mechanism: we had overridden Cell::initialize() in
ShadowRealmGlobalScope as a no-op.
Instead of that, do the same thing Window and Worker globals do and
make all of the globals that inherit UniversalGlobalScopeMixin opt
out of WEB_SET_PROTOTYPE_FOR_INTERFACE in EventTarget::initialize().
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
Specification: https://dom.spec.whatwg.org/#concept-event-dispatch
This also introduces shadow roots due to it being a requirement of
the event dispatcher.
However, it does not introduce the full shadow DOM, that can be
left for future work.
This changes some event dispatches which require certain attributes
to be initialised to a value.
This will be inherited by documents and workers, to provide a common
abstraction for script execution. (We don't have workers yet, but we
might as well make this little space for them now to simplify things
down the road.)
For now, the new DOM::EventDispatcher is very simple, it just iterates
over the set of listeners on an EventTarget and invokes the callbacks
as it goes.
This simplifies EventTarget subclasses since they no longer have to
implement the callback mechanism themselves.
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.
This patch adds the Event base class, along with a MouseEvent subclass.
We now dispatch MouseEvent objects for mousedown, mouseup and mousemove
and these objects have the .offsetX and .offsetY properties.
Both of those properties are hard-coded at the moment. This will be
fixed in the next patch. :^)
This patch adds the EventTarget class and makes Node inherit from it.
You can register event listeners on an EventTarget, and when you call
dispatch_event() on it, the event listeners will get invoked.
An event listener is basically a wrapper around a JS::Function*.
This is pretty far from how DOM events should eventually work, but it's
a place to start and we'll build more on top of this. :^)
