Replace the blocking spin_processing_tasks_with_source_until calls
in apply_the_history_step_after_unload_check() with an event-driven
ApplyHistoryStepState GC cell that tracks 5 phases, following the
same pattern used by CheckUnloadingCanceledState.
Key changes:
- Introduce ApplyHistoryStepState with phases:
WaitingForDocumentPopulation, ProcessingContinuations,
WaitingForChangeJobCompletion, WaitingForNonChangingJobs and Completed
- Add on_complete callbacks to apply_the_push_or_replace_history_step,
finalize_a_same_document_navigation,
finalize_a_cross_document_navigation, and
update_for_navigable_creation_or_destruction
- Remove spin_until from Document::open()
- Use null-document tasks for non-changing navigable updates and
document unload/destroy to avoid stuck tasks when documents become
non-fully-active
- Defer completely_finish_loading when document has no navigable yet,
and re-trigger post-load steps in activate_history_entry for documents
that completed loading before activation
Co-Authored-By: Shannon Booth <shannon@serenityos.org>
HTMLParser::the_end() had three spin_until calls that blocked the event
loop: step 5 (deferred scripts), step 7 (ASAP scripts), and step 8
(load event delay). This replaces them with an HTMLParserEndState state
machine that progresses asynchronously via callbacks.
The state machine has three phases matching the three spin_until calls:
- WaitingForDeferredScripts: loops executing ready deferred scripts
- WaitingForASAPScripts: waits for ASAP script lists to empty
- WaitingForLoadEventDelay: waits for nothing to delay the load event
Notification triggers re-evaluate the state machine when conditions
change: HTMLScriptElement::mark_as_ready, stylesheet unblocking in
StyleElementBase/HTMLLinkElement, did_stop_being_active_document, and
DocumentLoadEventDelayer decrements. NavigableContainer state changes
(session history readiness, content navigable cleared, lazy load flag)
also trigger re-evaluation of the load event delay check.
Key design decisions and why:
1. Microtask checkpoint in schedule_progress_check(): The old spin_until
called perform_a_microtask_checkpoint() before checking conditions.
This is critical because HTMLImageElement::update_the_image_data step
8 queues a microtask that creates the DocumentLoadEventDelayer.
Without the checkpoint, check_progress() would see zero delayers and
complete before images start delaying the load event.
2. deferred_invoke in schedule_progress_check():
I tried Core::Timer (0ms), queue_global_task, and synchronous calls.
Timers caused non-deterministic ordering with the HTML event loop's
task processing timer, leading to image layout tests failing (wrong
subtest pass/fail patterns). Synchronous calls fired too early during
image load processing before dimensions were set, causing 0-height
images in layout tests. queue_global_task had task ordering issues
with the session history traversal queue. deferred_invoke runs after
the current callback returns but within the same event loop pump,
giving the right balance.
3. Navigation load event guard (m_navigation_load_event_guard): During
cross-document navigation, finalize_a_cross_document_navigation step
2 calls set_delaying_load_events(false) before the session history
traversal activates the new document. This creates a transient state
where the parent's load event delay check sees the about:blank (which
has ready_for_post_load_tasks=true) as the active document and
completes prematurely.
By making use of the WEB_PLATFORM_OBJECT macro we can remove
the boilerplate of needing to add this override for every
serializable platform object so that we can check whether they
are exposed or not.
Add a clang plugin check that flags GC::Cell subclasses (and their
base classes within the Cell hierarchy) that have destructors with
non-trivial bodies. Such logic should use Cell::finalize() instead.
Add GC_ALLOW_CELL_DESTRUCTOR annotation macro for opting out in
exceptional cases (currently only JS::Object).
This prevents us from accidentally adding code in destructors that
runs after something we're pointing to may have been destroyed.
(This could become a problem when the garbage collector sweeps
objects in an unfortunate order.)
This new check uncovered a handful of bugs which are then also fixed
in this commit. :^)
This change fixes a bug that can be reproduced with the following steps:
```js
const iframe = document.createElement("iframe");
document.body.appendChild(iframe);
iframe.contentWindow.location.href = ("http://localhost:8080/demo.html");
```
These steps are executed in the following order:
1. Create iframe and schedule session history traversal task that adds
session history entry for the iframe.
2. Generate navigation id for scheduled navigation to
`http://localhost:8080/demo.html`.
3. Execute the scheduled session history traversal task, which adds
session history entry for the iframe.
4. Ooops, navigation to `http://localhost:8080/demo.html` is aborted
because addings SHE for the iframe resets the navigation id.
This change fixes this by delaying all navigations until SHE for a
navigable is created.
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
