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LibWeb: Skip assigning slottables for non-shadow roots

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For example, on https://html.spec.whatwg.org, there are hundreds of
thousands of nodes. This method is invoked as each node is inserted.
Traversing the entire tree each time takes a prohibitively long time,
so let's bail early when we know the operation is a no-op.
This commit is contained in:
Timothy Flynn 2023-11-03 14:31:46 -04:00 • committed by Andreas Kling
parent f3e14d7f64
commit cdbde1765a
1 changed files with 6 additions and 0 deletions
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6
Userland/Libraries/LibWeb/DOM/Slottable.cpp
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@ -176,6 +176,12 @@ void assign_slottables(JS::NonnullGCPtr<HTML::HTMLSlotElement> slot)
// https://dom.spec.whatwg.org/#assign-slotables-for-a-tree // https://dom.spec.whatwg.org/#assign-slotables-for-a-tree
void assign_slottables_for_a_tree(JS::NonnullGCPtr<Node> root) void assign_slottables_for_a_tree(JS::NonnullGCPtr<Node> root)
{ {
// AD-HOC: This method iterates over the root's entire subtree. That iteration does nothing if the root is not a
// shadow root (see `find_slottables`). This iteration can be very expensive as the HTML parser inserts
// nodes, especially on sites with many elements. So we skip it if we know it's going to be a no-op anyways.
if (!root->is_shadow_root())
return;
// To assign slottables for a tree, given a node root, run assign slottables for each slot slot in root’s inclusive // To assign slottables for a tree, given a node root, run assign slottables for each slot slot in root’s inclusive
// descendants, in tree order. // descendants, in tree order.
root->for_each_in_inclusive_subtree_of_type<HTML::HTMLSlotElement>([](auto& slot) { root->for_each_in_inclusive_subtree_of_type<HTML::HTMLSlotElement>([](auto& slot) {