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9e8e568b43
Replace per-element OrderedHashMap storage for custom properties with a RefCounted chain (CustomPropertyData) that enables structural sharing. Each chain node stores only the properties declared directly on its element, with a parent pointer to the inherited chain. Elements that don't override any custom properties share the parent's data directly (just a RefPtr copy). During cascade, only entries that actually differ from the parent are stored in own_values - the rest are inherited through the chain. During var() resolution, resolved values are compared against the parent's and matching entries are dropped, enabling further sharing. The chain uses a depth limit (max 32) with flattening, plus absorption of small parent nodes (threshold 8) to keep lookups fast. This reduces custom property memory from ~79 MB to ~5.7 MB on cloudflare.com.
76 lines
2.6 KiB
C++
76 lines
2.6 KiB
C++
/*
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* Copyright (c) 2026, Andreas Kling <andreas@ladybird.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <LibWeb/CSS/CustomPropertyData.h>
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#include <LibWeb/CSS/StyleValues/StyleValue.h>
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namespace Web::CSS {
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static constexpr u8 max_ancestor_count = 32;
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static constexpr size_t absorb_threshold = 8;
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CustomPropertyData::CustomPropertyData(OrderedHashMap<FlyString, StyleProperty> own_values, RefPtr<CustomPropertyData const> parent, u8 ancestor_count)
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: m_own_values(move(own_values))
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, m_parent(move(parent))
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, m_ancestor_count(ancestor_count)
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{
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}
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NonnullRefPtr<CustomPropertyData> CustomPropertyData::create(
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OrderedHashMap<FlyString, StyleProperty> own_values,
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RefPtr<CustomPropertyData const> parent)
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{
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if (!parent)
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return adopt_ref(*new CustomPropertyData(move(own_values), nullptr, 0));
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// If parent chain is too deep, flatten by copying all ancestor values into own.
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if (parent->m_ancestor_count >= max_ancestor_count - 1) {
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parent->for_each_property([&](FlyString const& name, StyleProperty const& property) {
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own_values.ensure(name, [&] { return property; });
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});
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return adopt_ref(*new CustomPropertyData(move(own_values), nullptr, 0));
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}
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// If parent has few own values, absorb them to shorten the chain.
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if (parent->m_own_values.size() <= absorb_threshold) {
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for (auto const& [name, property] : parent->m_own_values)
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own_values.ensure(name, [&] { return property; });
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auto grandparent = parent->m_parent;
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u8 ancestor_count = grandparent ? grandparent->m_ancestor_count + 1 : 0;
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return adopt_ref(*new CustomPropertyData(move(own_values), move(grandparent), ancestor_count));
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}
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u8 ancestor_count = parent->m_ancestor_count + 1;
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return adopt_ref(*new CustomPropertyData(move(own_values), move(parent), ancestor_count));
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}
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StyleProperty const* CustomPropertyData::get(FlyString const& name) const
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{
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if (auto it = m_own_values.find(name); it != m_own_values.end())
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return &it->value;
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if (m_parent)
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return m_parent->get(name);
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return nullptr;
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}
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void CustomPropertyData::for_each_property(Function<void(FlyString const&, StyleProperty const&)> callback) const
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{
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HashTable<FlyString> seen;
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for (auto const* node = this; node; node = node->m_parent.ptr()) {
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for (auto const& [name, property] : node->m_own_values) {
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if (seen.set(name) == HashSetResult::KeptExistingEntry)
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continue;
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callback(name, property);
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}
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}
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}
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bool CustomPropertyData::is_empty() const
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{
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return m_own_values.is_empty() && (!m_parent || m_parent->is_empty());
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}
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}
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