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LibWeb: Cache intrinsic sizes across layout runs

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This change moves intrinsic sizes cache from
LayoutState, which is local to current layout run,
to layout nodes, so it could be reused between
layout runs. This optimization is possible because
we can guarantee that these measurements will
remain unchanged unless the style of the element
or any of its descendants changes.

For now, invalidation is implemented simply by
resetting cache on whole ancestors chain once we
figured that element needs layout update.
The case when layout is invalidated by DOM's
structural changes is covered by layout tree
invalidation that drops intrinsic sizes cache
along with layout nodes.

I measured improvement on couple websites:
- Mail list on GMail 28ms -> 6ms
- GitHub large code page 47ms -> 36ms
- Discord chat history 15ms -> 8ms
(Time does not include `commit()`)
This commit is contained in:
Aliaksandr Kalenik 2025-03-07 20:37:04 +01:00 • committed by Andreas Kling
parent 180a58b3d2
commit 12c6ac78e2
Notes: github-actions[bot] 2025-03-08 10:46:30 +00:00
13 changed files with 108 additions and 102 deletions
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34
Libraries/LibWeb/DOM/Document.cpp
View file

@ -1211,20 +1211,6 @@ Optional<String> Document::encoding_parse_and_serialize_url(StringView url) cons
return parsed_url->serialize();
}
void Document::set_needs_layout(SetNeedsLayoutReason reason)
{
if (m_needs_layout)
return;
if constexpr (UPDATE_LAYOUT_DEBUG) {
// NOTE: We check some conditions here to avoid debug spam in documents that don't do layout.
auto navigable = this->navigable();
if (m_layout_root && navigable && navigable->active_document() == this)
dbgln_if(UPDATE_LAYOUT_DEBUG, "NEED LAYOUT {}", to_string(reason));
}
m_needs_layout = true;
schedule_layout_update();
}
void Document::invalidate_layout_tree(InvalidateLayoutTreeReason reason)
{
if (m_layout_root)
@ -1299,7 +1285,7 @@ void Document::update_layout(UpdateLayoutReason reason)
update_style();
if (!m_needs_layout && m_layout_root)
if (!m_needs_layout_update && m_layout_root)
return;
// NOTE: If this is a document hosting <template> contents, layout is unnecessary.
@ -1329,11 +1315,16 @@ void Document::update_layout(UpdateLayoutReason reason)
}
}
// Assign each box that establishes a formatting context a list of absolutely positioned children it should take care of during layout
m_layout_root->for_each_in_inclusive_subtree_of_type<Layout::Box>([&](auto& child) {
bool needs_layout_update = child.dom_node() && child.dom_node()->needs_layout_update();
if (needs_layout_update || child.is_anonymous()) {
child.reset_cached_intrinsic_sizes();
}
child.clear_contained_abspos_children();
return TraversalDecision::Continue;
});
// Assign each box that establishes a formatting context a list of absolutely positioned children it should take care of during layout
m_layout_root->for_each_in_inclusive_subtree([&](auto& child) {
if (!child.is_absolutely_positioned())
return TraversalDecision::Continue;
@ -1396,7 +1387,10 @@ void Document::update_layout(UpdateLayoutReason reason)
paintable()->recompute_selection_states(*range);
}
m_needs_layout = false;
for_each_shadow_including_inclusive_descendant([](auto& node) {
node.reset_needs_layout_update();
return TraversalDecision::Continue;
});
// Scrolling by zero offset will clamp scroll offset back to valid range if it was out of bounds
// after the viewport size change.
@ -1430,6 +1424,9 @@ void Document::update_layout(UpdateLayoutReason reason)
}
is_display_none = static_cast<Element&>(node).computed_properties()->display().is_none();
}
if (node_invalidation.relayout) {
node.set_needs_layout_update(SetNeedsLayoutReason::StyleChange);
}
if (node_invalidation.rebuild_layout_tree) {
// We mark layout tree for rebuild starting from parent element to correctly invalidate
// "display" property change to/from "contents" value.
@ -1441,6 +1438,7 @@ void Document::update_layout(UpdateLayoutReason reason)
}
invalidation |= node_invalidation;
node.set_needs_style_update(false);
invalidation |= node_invalidation;
bool children_need_inherited_style_update = !invalidation.is_none();
if (needs_full_style_update || node.child_needs_style_update() || children_need_inherited_style_update) {
@ -1532,8 +1530,6 @@ void Document::update_style()
auto invalidation = update_style_recursively(*this, style_computer(), false);
if (!invalidation.is_none())
invalidate_display_list();
if (invalidation.relayout)
set_needs_layout(SetNeedsLayoutReason::StyleChange);
if (invalidation.rebuild_stacking_context_tree)
invalidate_stacking_context_tree();
m_needs_full_style_update = false;