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LibWeb: Don't create mutation record node lists if nobody is interested

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By deferring allocation of StaticNodeList objects until we know somebody
actually wants the MutationRecord, we avoid a *lot* of allocation work.

This shaves several seconds off of loading https://tc39.es/ecma262/

At least one other engine (WebKit) skips creating mutation records if
nobody is interested, so even if this is observable somehow, we would
at least match the behavior of a major engine.
This commit is contained in:
Andreas Kling 2023-05-17 19:47:16 +02:00
parent 0f2b6345c6
commit 80d6330a26
4 changed files with 22 additions and 31 deletions
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39
Userland/Libraries/LibWeb/DOM/Node.cpp
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2018-2023, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021-2022, Linus Groh <linusg@serenityos.org>
* Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
*
@ -405,9 +405,7 @@ void Node::insert_before(JS::NonnullGCPtr<Node> node, JS::GCPtr<Node> child, boo
// 2. Queue a tree mutation record for node with « », nodes, null, and null.
// NOTE: This step intentionally does not pay attention to the suppress observers flag.
auto added_node_list = StaticNodeList::create(realm(), {}).release_value_but_fixme_should_propagate_errors();
auto removed_node_list = StaticNodeList::create(realm(), nodes).release_value_but_fixme_should_propagate_errors();
node->queue_tree_mutation_record(added_node_list, removed_node_list, nullptr, nullptr);
node->queue_tree_mutation_record({}, nodes, nullptr, nullptr);
}
// 5. If child is non-null, then:
@ -480,9 +478,7 @@ void Node::insert_before(JS::NonnullGCPtr<Node> node, JS::GCPtr<Node> child, boo
// 8. If suppress observers flag is unset, then queue a tree mutation record for parent with nodes, « », previousSibling, and child.
if (!suppress_observers) {
auto added_node_list = StaticNodeList::create(realm(), move(nodes)).release_value_but_fixme_should_propagate_errors();
auto removed_node_list = StaticNodeList::create(realm(), {}).release_value_but_fixme_should_propagate_errors();
queue_tree_mutation_record(added_node_list, removed_node_list, previous_sibling.ptr(), child.ptr());
queue_tree_mutation_record(move(nodes), {}, previous_sibling.ptr(), child.ptr());
}
// 9. Run the children changed steps for parent.
@ -650,11 +646,7 @@ void Node::remove(bool suppress_observers)
// 20. If suppress observers flag is unset, then queue a tree mutation record for parent with « », « node », oldPreviousSibling, and oldNextSibling.
if (!suppress_observers) {
Vector<JS::Handle<Node>> removed_nodes;
removed_nodes.append(JS::make_handle(*this));
auto added_node_list = StaticNodeList::create(realm(), {}).release_value_but_fixme_should_propagate_errors();
auto removed_node_list = StaticNodeList::create(realm(), move(removed_nodes)).release_value_but_fixme_should_propagate_errors();
parent->queue_tree_mutation_record(added_node_list, removed_node_list, old_previous_sibling.ptr(), old_next_sibling.ptr());
parent->queue_tree_mutation_record({}, { *this }, old_previous_sibling.ptr(), old_next_sibling.ptr());
}
// 21. Run the children changed steps for parent.
@ -749,9 +741,7 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> Node::replace_child(JS::NonnullGCPtr
insert_before(node, reference_child, true);
// 14. Queue a tree mutation record for parent with nodes, removedNodes, previousSibling, and referenceChild.
auto added_node_list = TRY(StaticNodeList::create(realm(), move(nodes)));
auto removed_node_list = TRY(StaticNodeList::create(realm(), move(removed_nodes)));
queue_tree_mutation_record(added_node_list, removed_node_list, previous_sibling.ptr(), reference_child.ptr());
queue_tree_mutation_record(move(nodes), move(removed_nodes), previous_sibling.ptr(), reference_child.ptr());
// 15. Return child.
return child;
@ -1220,9 +1210,7 @@ void Node::replace_all(JS::GCPtr<Node> node)
// 7. If either addedNodes or removedNodes is not empty, then queue a tree mutation record for parent with addedNodes, removedNodes, null, and null.
if (!added_nodes.is_empty() || !removed_nodes.is_empty()) {
auto added_node_list = StaticNodeList::create(realm(), move(added_nodes)).release_value_but_fixme_should_propagate_errors();
auto removed_node_list = StaticNodeList::create(realm(), move(removed_nodes)).release_value_but_fixme_should_propagate_errors();
queue_tree_mutation_record(added_node_list, removed_node_list, nullptr, nullptr);
queue_tree_mutation_record(move(added_nodes), move(removed_nodes), nullptr, nullptr);
}
}
@ -1430,7 +1418,7 @@ Painting::PaintableBox const* Node::paintable_box() const
}
// https://dom.spec.whatwg.org/#queue-a-mutation-record
void Node::queue_mutation_record(FlyString const& type, DeprecatedString attribute_name, DeprecatedString attribute_namespace, DeprecatedString old_value, JS::NonnullGCPtr<NodeList> added_nodes, JS::NonnullGCPtr<NodeList> removed_nodes, Node* previous_sibling, Node* next_sibling) const
void Node::queue_mutation_record(FlyString const& type, DeprecatedString attribute_name, DeprecatedString attribute_namespace, DeprecatedString old_value, Vector<JS::Handle<Node>> added_nodes, Vector<JS::Handle<Node>> removed_nodes, Node* previous_sibling, Node* next_sibling) const
{
// NOTE: We defer garbage collection until the end of the scope, since we can't safely use MutationObserver* as a hashmap key otherwise.
// FIXME: This is a total hack.
@ -1479,11 +1467,18 @@ void Node::queue_mutation_record(FlyString const& type, DeprecatedString attribu
}
}
// OPTIMIZATION: If there are no interested observers, bail without doing any more work.
if (interested_observers.is_empty())
return;
auto added_nodes_list = StaticNodeList::create(realm(), move(added_nodes)).release_value_but_fixme_should_propagate_errors();
auto removed_nodes_list = StaticNodeList::create(realm(), move(removed_nodes)).release_value_but_fixme_should_propagate_errors();
// 4. For each observer → mappedOldValue of interestedObservers:
for (auto& interested_observer : interested_observers) {
// 1. Let record be a new MutationRecord object with its type set to type, target set to target, attributeName set to name, attributeNamespace set to namespace, oldValue set to mappedOldValue,
// addedNodes set to addedNodes, removedNodes set to removedNodes, previousSibling set to previousSibling, and nextSibling set to nextSibling.
auto record = MutationRecord::create(realm(), type, *this, added_nodes, removed_nodes, previous_sibling, next_sibling, attribute_name, attribute_namespace, /* mappedOldValue */ interested_observer.value).release_value_but_fixme_should_propagate_errors();
auto record = MutationRecord::create(realm(), type, *this, added_nodes_list, removed_nodes_list, previous_sibling, next_sibling, attribute_name, attribute_namespace, /* mappedOldValue */ interested_observer.value).release_value_but_fixme_should_propagate_errors();
// 2. Enqueue record to observer’s record queue.
interested_observer.key->enqueue_record({}, move(record));
@ -1494,10 +1489,10 @@ void Node::queue_mutation_record(FlyString const& type, DeprecatedString attribu
}
// https://dom.spec.whatwg.org/#queue-a-tree-mutation-record
void Node::queue_tree_mutation_record(JS::NonnullGCPtr<NodeList> added_nodes, JS::NonnullGCPtr<NodeList> removed_nodes, Node* previous_sibling, Node* next_sibling)
void Node::queue_tree_mutation_record(Vector<JS::Handle<Node>> added_nodes, Vector<JS::Handle<Node>> removed_nodes, Node* previous_sibling, Node* next_sibling)
{
// 1. Assert: either addedNodes or removedNodes is not empty.
VERIFY(added_nodes->length() > 0 || removed_nodes->length() > 0);
VERIFY(added_nodes.size() > 0 || removed_nodes.size() > 0);
// 2. Queue a mutation record of "childList" for target with null, null, null, addedNodes, removedNodes, previousSibling, and nextSibling.
queue_mutation_record(MutationType::childList, {}, {}, {}, move(added_nodes), move(removed_nodes), previous_sibling, next_sibling);