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LibWeb: Avoid rebuilding layout tree unless CSS display property changes

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Before this, any style change that mutated a property we consider
"layout-affecting" would trigger a complete teardown and rebuild of the
layout tree.

This isn't actually necessary for the vast majority of CSS properties,
so this patch makes the invalidation a bit finer, and we now only
rebuild the layout tree when the CSS display property changes.

For other layout-affecting properties, we keep the old layout tree (if
we have one) and run the layout algorithms over that once again.
This is significantly faster, since we don't have to run all the CSS
selectors all over again.
This commit is contained in:
Andreas Kling 2023-05-22 16:09:15 +02:00
parent 8f5cc613d2
commit 821f808e52
3 changed files with 66 additions and 53 deletions
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22
Userland/Libraries/LibWeb/DOM/Document.cpp
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@ -908,13 +908,13 @@ void Document::update_layout()
m_layout_update_timer->stop();
}
[[nodiscard]] static bool update_style_recursively(DOM::Node& node)
[[nodiscard]] static Element::RequiredInvalidationAfterStyleChange update_style_recursively(DOM::Node& node)
{
bool const needs_full_style_update = node.document().needs_full_style_update();
bool needs_relayout = false;
Element::RequiredInvalidationAfterStyleChange invalidation;
if (is<Element>(node)) {
needs_relayout |= static_cast<Element&>(node).recompute_style() == Element::NeedsRelayout::Yes;
invalidation |= static_cast<Element&>(node).recompute_style();
}
node.set_needs_style_update(false);
@ -922,18 +922,18 @@ void Document::update_layout()
if (node.is_element()) {
if (auto* shadow_root = static_cast<DOM::Element&>(node).shadow_root_internal()) {
if (needs_full_style_update || shadow_root->needs_style_update() || shadow_root->child_needs_style_update())
needs_relayout |= update_style_recursively(*shadow_root);
invalidation |= update_style_recursively(*shadow_root);
}
}
node.for_each_child([&](auto& child) {
if (needs_full_style_update || child.needs_style_update() || child.child_needs_style_update())
needs_relayout |= update_style_recursively(child);
invalidation |= update_style_recursively(child);
return IterationDecision::Continue;
});
}
node.set_child_needs_style_update(false);
return needs_relayout;
return invalidation;
}
void Document::update_style()
@ -948,8 +948,16 @@ void Document::update_style()
return;
evaluate_media_rules();
if (update_style_recursively(*this))
auto invalidation = update_style_recursively(*this);
if (invalidation.rebuild_layout_tree) {
invalidate_layout();
} else {
if (invalidation.relayout)
set_needs_layout();
if (invalidation.rebuild_stacking_context_tree)
invalidate_stacking_context_tree();
}
m_needs_full_style_update = false;
m_style_update_timer->stop();
}