The environment settings object is effectively the context a piece of
script is running under, for example, it contains the origin,
responsible document, realm, global object and event loop for the
current context. This effectively replaces ScriptExecutionContext, but
it cannot be removed in this commit as EventTarget still depends on it.
https://html.spec.whatwg.org/multipage/webappapis.html#environment-settings-object
This commit removes all exception related code:
Remove VM::exception(), VM::throw_exception() etc. Any leftover
throw_exception calls are moved to throw_completion.
The one method left is clear_exception() which is now a no-op. Most of
these calls are just to clear whatever exception might have been thrown
when handling a Completion. So to have a cleaner commit this will be
removed in a next commit.
It also removes the actual Exception and TemporaryClearException classes
since these are no longer used.
In any spot where the exception was actually used an attempt was made to
preserve that behavior. However since it is no longer tracked by the VM
we cannot access exceptions which were thrown in previous calls.
There are two such cases which might have different behavior:
- In Web::DOM::Document::interpreter() the on_call_stack_emptied hook
used to print any uncaught exception but this is now no longer
possible as the VM does not store uncaught exceptions.
- In js the code used to be interruptable by throwing an exception on
the VM. This is no longer possible but was already somewhat fragile
before as you could happen to throw an exception just before a VERIFY.
Instead of making each Layout::Node compute style for itself, we now
compute it in TreeBuilder before even calling create_layout_node().
For non-element DOM nodes, we create the style and layout tree node
in TreeBuilder. This allows us to move create_layout_node() from
DOM::Node to DOM::Element.
This also refactors interpreter creation to follow
InitializeHostDefinedRealm, but I couldn't fit it in the title :^)
This allows us to follow the spec much more closely rather than being
completely ad-hoc with just the parse node instead of having all the
surrounding data such as the realm of the parse node.
The interpreter creation refactor creates the global execution context
once and doesn't take it off the stack. This allows LibWeb to take the
global execution context and manually handle it, following the HTML
spec. The HTML spec calls this the "realm execution context" of the
environment settings object.
It also allows us to specify the globalThis type, as it can be
different from the global object type. For example, on the web, Window
global objects use a WindowProxy global this value to enforce the same
origin policy on operations like [[GetOwnProperty]].
Finally, it allows us to directly call Program::execute in perform_eval
and perform_shadow_realm_eval as this moves
global_declaration_instantiation into Interpreter::run
(ScriptEvaluation) as per the spec.
Note that this doesn't evalulate Source Text Modules yet or refactor
the bytecode interpreter, that's work for future us :^)
This patch was originally build by Luke for the environment settings
object change but was also needed for modules. So I (davidot) have
modified it with the new completion changes and setup for that.
Co-authored-by: davidot <davidot@serenityos.org>
Instead of making it a void function, checking for an exception, and
then receiving the relevant result via VM::last_value(), we can
consolidate all of this by using completions.
This allows us to remove more uses of VM::exception(), and all uses of
VM::last_value().
This allows document.implementation to keep the underlying document
alive for as long as we need it (for example, if someone holds on to a
DOMImplementation JS wrapper after the document is GC'd.)
These aren't needed now that we render using background_layers instead.
The one casualty is the resolved style for background-repeat, but that
was incorrect anyway.
Instead of storing these as individual `background-foo` properties, we
combine them together into layers, since that is how they will be
painted. It also makes it more convenient to pass them around.
While right now this doesn't save much complexity, it will do once we
care about multiple background layers per node. Then, having a single
repeat value per layer will simplify things.
It also means we can remove the pseudo-property concept entirely! :^)
If we had a scheduled update of either of these kind, make sure to
cancel it after performing an update. Otherwise we might do a redundant
second update with the same results.
This could happen if something schedules an async layout, and before it
can happen, something requires a sync layout, which we do right away.
We now evaluate the conditions of `@media` rules at the same point in
the HTML event loop as evaluation of `MediaQueryList`s. This is not
strictly to spec, but since the spec doesn't actually say when to do
this, it seems to make the most sense. In any case, it works! :^)
The recursive style update function was written a bit strangely and
would only mark descendants of the style update root as not needing a
style update.
With this patch, all nodes in the subtree now have clean style after a
style update finishes.
Layout depends on style (and not the other way around), so if the
document has dirty style when we enter update_layout(), make sure we
call update_style() before proceeding with the layout work.
This has the pleasant effect of coalescing some redundant layouts.
Instead of doing layout synchronously whenever something changes,
we now use a basic event loop timer to defer and coalesce relayouts.
If you did something that requires a relayout of the page, make sure
to call Document::set_needs_layout() and it will get coalesced with all
the other layout updates.
There's lots of room for improvement here, but this already makes many
web pages significantly snappier. :^)
Also, note that this exposes a number of layout bugs where we have been
relying on multiple relayouts to calculate the correct dimensions for
things. Now that we only do a single layout in many cases, these kind of
problems are much more noticeable. That should also make them easier to
figure out and fix. :^)
This is used surprisingly often. For example, it is used by a core
YouTube library called Structured Page Fragments.
It allows you to manually dispatch an event with arbitrary data
attached to it.
The only thing missing from this implementation is the constructor.
This is because WrapperGenerator is currently missing dictionary
capabilities.
The only difference from what we were already doing is that setting the
same ready state twice no longer fires a "readystatechange" event.
I don't think that could happen in practice though.
Resolved style is a spec concept that refers to the weird mix of
computed style and used style reflected by getComputedStyle().
The purpose of this class is to produce the *computed* style for a given
element, so let's call it StyleComputer.
This also moves getElementsByTagName to ParentNode to remove the code
duplication between Document and Element. This additionally fixes a bug
where getElementsByTagName did not check if the element was a
descendant, meaning it would also include the context element if the
condition matched.
Rather than destroying and rebuilding the entire document layout tree in
every call to `ComputedCSSStyleDeclaration::property()`, we now just
make sure that the layout tree exists.
This speeds up the DOM Inspector significantly, from taking several
seconds to select an element, to almost instant. :^)
This namespace will be used for all interfaces defined in the URL
specification, like URL and URLSearchParams.
This has the unfortunate side-effect of requiring us to use the fully
qualified AK::URL name whenever we want to refer to the AK class, so
this commit also fixes all such references.
The spec allows us to optionally return from these for any reason.
Our reason is that we don't have all the infrastructure in place yet to
implement them.
This will be used by the HTML parser to determine whether it's okay to
start running a script.
Note that we don't actually count the script-blocking style sheets yet.
This patch only adds a the checking mechanism for the parser.
