Our BrowsingContext currently supports 1 target. So we have a per-BC target_id.
Previously, our target had 1 "frame" - our page. So we often treated the
targetId as the frameId. But to work with frames, we need page-specific
frameIds and loaderIds.
This tries to clean up our ids (a little). frameIds are now ids derived from
a new incrementing page.id. This page.id has to be passed around (via http
Requests and through notifications) in order to properly generate messages with
a frameId.
At a high level, this does for Events what was recently done for XHR, Fetch and
Observers. Events are self-contained in their own arena from the ArenaPool and
are registered with v8 to be finalized.
But events are more complicated than those other types. For one, events have
a prototype chain. (XHR also does, but it's always the top-level object that's
created, whereas it's valid to create a base Event or something that inherits
from Event). But the _real_ complication is that Events, unlike previous types,
can be created from Zig or from V8.
This is something that Fetch had to deal with too, because the Response is only
given to V8 on success. So in Fetch, there's a period of time where Zig is
solely responsible for the Response, until it's passed to v8. But with events
it's a lot more subtle.
There are 3 possibilities:
1 - An Event is created from v8. This is the simplest, and it simply becomes a
a weak reference for us. When v8 is done with it, the finalizer is called.
2 - An Event is created in Zig (e.g. window.load) and dispatched to v8. Again
we can rely on the v8 finalizer.
3 - An event is created in Zig, but not dispatched to v8 (e.g. there are no
listeners), Zig has to release the event.
(It's worth pointing out that one thing that still keeps this relatively
straightforward is that we never hold on to Events past some pretty clear point)
Now, it would seem that #3 is the only issue we have to deal with, and maybe
we can do something like:
```
if (event_manager.hasListener("load", capture)) {
try event_manager.dispatch(event);
} else {
event.deinit();
}
```
In fact, in many cases, we could use this to optimize not even creating the
event:
```
if (event_manager.hasListener("load, capture)) {
const event = try createEvent("load", capture);
try event_manager.dispatch(event);
}
```
And that's an optimization worth considering, but it isn't good enough to
properly manage memory. Do you see the issue? There could be a listener (so we
think v8 owns it), but we might never give the value to v8. Any failure between
hasListener and actually handing the value to v8 would result in a leak.
To solve this, the bridge will now set a _v8_handover flag (if present) once it
has created the finalizer_callback entry. So dispatching code now becomes:
```
const event = try createEvent("load", capture);
defer if (!event._v8_handover) event.deinit(false);
try event_manager.dispatch(event);
```
The v8 finalizer callback was also improved. Previously, we just embedded the
pointer to the zig object. In the v8 callback, we could cast that back to T
and call deinit. But, because of possible timing issues between when (if) v8
calls the finalizer, and our own cleanup, the code would check in the context to
see if the ptr was still valid. Wait, what? We're using the ptr to get the
context to see if the ptr is valid?
We now store a pointer to the FinalizerCallback which contains the context.
So instead of something stupid like:
```
// note, if the identity_map doesn't contain the value, then value is likely
// invalid, and value.page will segfault
value.page.js.identity_map.contains(@intFromPtr(value))
```
We do:
```
if (fc.ctx.finalizer_callbacks.contains(@intFromPtr(fc.value)) {
// fc.value is safe to use
}
```
Support CDP's Input.dispatchKeyEvent and DOM key events. Currently only
keydown is supported and expects every key to be a displayable character.
It turns out that manipulating the DOM via key events isn't great because the
behavior really depends on the cursor. So, to do this more accurately, we'd
have to introduce some concept of a cursor.
Personally, I don't think we'll run into many pages that are purposefully
using keyboard events. But driver (puppeteer/playwright) scripts might be
another issue.
Combine uri + rawuri into single struct.
Try to improve ownership around URIs and URI-like things.
- cookie & request can take *const std.Uri
(TODO: make them aware of the new URL struct?)
- Location (web api) should own its URL (web api URL)
- Window should own its Location
Most of these changes result in (a) a cleaner Page and (b) not having to carry
around 2 nullable objects (URI and rawuri).
FlatRenderer positions items on a single row, giving each a height and width of
1.
Added getBoundingClientRect to the DOMelement which, when requested for the
first time, will place the item in with the renderer.
The goal here is to give elements a fixed position and to make it easy to map
x,y coordinates onto an element. This should work, at least with puppeteer,
since it first requests the boundingClientRect before issuing a click.
