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LibWeb: Maintain a map of child-to-parent nodes in OOPWV DOM Inspector

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Currently, each time parent_index() is invoked, two depth-first searches
are incurred to find the node's parent and grandparent. This becomes
particularly expensive, for example, when trying to scroll through a
large <ul> list.

Instead, upon creation, traverse the DOM JSON and create a map of child
nodes to their parent. Then those two lookups become hash map lookups
rather than a DFS traversal.
This commit is contained in:
Timothy Flynn 2021-07-01 12:27:32 -04:00 • committed by Andreas Kling
parent 97ea192e3e
commit 447ecc2155
2 changed files with 23 additions and 30 deletions
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36
Userland/Libraries/LibWeb/DOMTreeJSONModel.cpp
View file

@ -18,6 +18,8 @@ DOMTreeJSONModel::DOMTreeJSONModel(JsonObject dom_tree)
m_document_icon.set_bitmap_for_size(16, Gfx::Bitmap::load_from_file("/res/icons/16x16/filetype-html.png"));
m_element_icon.set_bitmap_for_size(16, Gfx::Bitmap::load_from_file("/res/icons/16x16/inspector-object.png"));
m_text_icon.set_bitmap_for_size(16, Gfx::Bitmap::load_from_file("/res/icons/16x16/filetype-unknown.png"));
map_dom_nodes_to_parent(nullptr, &m_dom_tree);
}
DOMTreeJSONModel::~DOMTreeJSONModel()
@ -47,20 +49,18 @@ GUI::ModelIndex DOMTreeJSONModel::parent_index(const GUI::ModelIndex& index) con
return {};
auto const& node = *static_cast<JsonObject const*>(index.internal_data());
auto node_internal_id = get_internal_id(node);
auto const* parent_node = find_parent_of_child_with_internal_id(node_internal_id);
auto const* parent_node = get_parent(node);
if (!parent_node)
return {};
// If the parent is the root document, we know it has index 0, 0
auto parent_node_internal_id = get_internal_id(*parent_node);
if (parent_node_internal_id == get_internal_id(m_dom_tree)) {
if (parent_node == &m_dom_tree) {
return create_index(0, 0, parent_node);
}
// Otherwise, we need to find the grandparent, to find the index of parent within that
auto const* grandparent_node = find_parent_of_child_with_internal_id(parent_node_internal_id);
auto const* grandparent_node = get_parent(*parent_node);
VERIFY(grandparent_node);
auto const* grandparent_children = get_children(*grandparent_node);
@ -69,7 +69,7 @@ GUI::ModelIndex DOMTreeJSONModel::parent_index(const GUI::ModelIndex& index) con
for (size_t grandparent_child_index = 0; grandparent_child_index < grandparent_children->size(); ++grandparent_child_index) {
auto const& child = grandparent_children->at(grandparent_child_index).as_object();
if (get_internal_id(child) == parent_node_internal_id)
if (&child == parent_node)
return create_index(grandparent_child_index, 0, parent_node);
}
@ -157,24 +157,18 @@ void DOMTreeJSONModel::update()
did_update();
}
JsonObject const* DOMTreeJSONModel::find_parent_of_child_with_internal_id(JsonObject const& node, size_t internal_id) const
void DOMTreeJSONModel::map_dom_nodes_to_parent(JsonObject const* parent, JsonObject const* node)
{
auto const* children = get_children(node);
m_dom_node_to_parent_map.set(node, parent);
auto const* children = get_children(*node);
if (!children)
return nullptr;
return;
for (size_t i = 0; i < children->size(); ++i) {
auto const& child = children->at(i).as_object();
auto child_internal_id = get_internal_id(child);
if (child_internal_id == internal_id)
return &node;
if (auto const* maybe_node = find_parent_of_child_with_internal_id(child, internal_id); maybe_node)
return maybe_node;
}
return nullptr;
children->for_each([&](auto const& child) {
auto const& child_node = child.as_object();
map_dom_nodes_to_parent(node, &child_node);
});
}
}