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LibWeb/HTML: Resolve image decoding promises inside tasks
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This corresponds to whatwg/html#10753

WHile I was at it, I've also moved the checks inside the spin callback,
and reformatted the spec comments to match our style.
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@AtkinsSJ
AtkinsSJ committed Nov 27, 2024
1 parent 5deb2b4 commit d568db4
Showing 1 changed file with 54 additions and 38 deletions.
92 changes: 54 additions & 38 deletions Libraries/LibWeb/HTML/HTMLImageElement.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -315,6 +315,9 @@ WebIDL::ExceptionOr<GC::Ref<WebIDL::Promise>> HTMLImageElement::decode() const

// 2. Queue a microtask to perform the following steps:
queue_a_microtask(&document(), GC::create_function(realm.heap(), [this, promise, &realm]() mutable {
// 1. Let global be this's relevant global object.
auto& global = relevant_global_object(*this);

auto reject_if_document_not_fully_active = [this, promise, &realm]() -> bool {
if (this->document().is_fully_active())
return false;
Expand All @@ -335,55 +338,68 @@ WebIDL::ExceptionOr<GC::Ref<WebIDL::Promise>> HTMLImageElement::decode() const
return true;
};

// 2.1 If any of the following are true:
// 2.1.1 this's node document is not fully active;
// 2.1.1 then reject promise with an "EncodingError" DOMException.
if (reject_if_document_not_fully_active())
return;

// 2.1.2 or this's current request's state is broken,
// 2.1.2 then reject promise with an "EncodingError" DOMException.
if (reject_if_current_request_state_broken())
// 2. If any of the following are true:
// - this's node document is not fully active;
// - or this's current request's state is broken,
// then reject promise with an "EncodingError" DOMException.
if (reject_if_document_not_fully_active() || reject_if_current_request_state_broken()) {
return;
}

// 2.2 Otherwise, in parallel wait for one of the following cases to occur, and perform the corresponding actions:
Platform::EventLoopPlugin::the().deferred_invoke(GC::create_function(heap(), [this, promise, &realm, reject_if_document_not_fully_active, reject_if_current_request_state_broken] {
// 3. Otherwise, in parallel wait for one of the following cases to occur, and perform the corresponding actions:
Platform::EventLoopPlugin::the().deferred_invoke(GC::create_function(heap(), [this, promise, &realm, &global] {
Platform::EventLoopPlugin::the().spin_until(GC::create_function(heap(), [&] {
auto state = this->current_request().state();
auto queue_reject_task = [&](String const& message) {
queue_global_task(Task::Source::DOMManipulation, global, GC::create_function(realm.heap(), [&realm, &promise, &message] {
auto exception = WebIDL::EncodingError::create(realm, message);
HTML::TemporaryExecutionContext context(realm);
WebIDL::reject_promise(realm, promise, exception);
}));
};

// -> This img element's node document stops being fully active
if (!document().is_fully_active()) {
// Queue a global task on the DOM manipulation task source with global to reject promise with an "EncodingError" DOMException.
queue_reject_task("Node document not fully active"_string);
return true;
}

return !this->document().is_fully_active() || state == ImageRequest::State::Broken || state == ImageRequest::State::CompletelyAvailable;
}));
auto state = this->current_request().state();

// 2.2.1 This img element's node document stops being fully active
// 2.2.1 Reject promise with an "EncodingError" DOMException.
if (reject_if_document_not_fully_active())
return;
// -> FIXME: This img element's current request changes or is mutated
if (false) {
// Queue a global task on the DOM manipulation task source with global to reject promise with an "EncodingError" DOMException.
queue_reject_task("Current request changed or was mutated"_string);
return true;
}

// FIXME: 2.2.2 This img element's current request changes or is mutated
// FIXME: 2.2.2 Reject promise with an "EncodingError" DOMException.
// -> This img element's current request's state becomes broken
if (state == ImageRequest::State::Broken) {
// Queue a global task on the DOM manipulation task source with global to reject promise with an "EncodingError" DOMException.
queue_reject_task("Current request state is broken"_string);
return true;
}

// 2.2.3 This img element's current request's state becomes broken
// 2.2.3 Reject promise with an "EncodingError" DOMException.
if (reject_if_current_request_state_broken())
return;
// -> This img element's current request's state becomes completely available
if (state == ImageRequest::State::CompletelyAvailable) {
// FIXME: Decode the image.
// FIXME: If decoding does not need to be performed for this image (for example because it is a vector graphic) or the decoding process completes successfully, then queue a global task on the DOM manipulation task source with global to resolve promise with undefined.
// FIXME: If decoding fails (for example due to invalid image data), then queue a global task on the DOM manipulation task source with global to reject promise with an "EncodingError" DOMException.

// NOTE: For now we just resolve it.
queue_global_task(Task::Source::DOMManipulation, global, GC::create_function(realm.heap(), [&realm, &promise] {
HTML::TemporaryExecutionContext context(realm);
WebIDL::resolve_promise(realm, promise, JS::js_undefined());
}));
return true;
}

// 2.2.4 This img element's current request's state becomes completely available
if (this->current_request().state() == ImageRequest::State::CompletelyAvailable) {
// 2.2.4.1 FIXME: Decode the image.
// 2.2.4.2 FIXME: If decoding does not need to be performed for this image (for example because it is a vector graphic), resolve promise with undefined.
// 2.2.4.3 FIXME: If decoding fails (for example due to invalid image data), reject promise with an "EncodingError" DOMException.
// 2.2.4.4 FIXME: If the decoding process completes successfully, resolve promise with undefined.
// 2.2.4.5 FIXME: User agents should ensure that the decoded media data stays readily available until at least the end of the next successful update
// the rendering step in the event loop. This is an important part of the API contract, and should not be broken if at all possible.
// (Typically, this would only be violated in low-memory situations that require evicting decoded image data, or when the image is too large
// to keep in decoded form for this period of time.)

HTML::TemporaryExecutionContext context(realm);
WebIDL::resolve_promise(realm, promise, JS::js_undefined());
}
return false;
}));
}));
}));

// 3. Return promise.
return promise;
}

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