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LibWeb: Make Layout::FormattingState copies shallow
Previously, each NodeState in a FormattingState was shared with the parent FormattingState, but the HashMap of NodeState had to be copied when making FormattingState copies. This patch makes copying instant by keeping a pointer to the parent FormattingState instead. When fetching immutable state via get(), we may now return a reference to a NodeState owned by a parent FormattingState. get_mutable() will copy any NodeState found in the ancestor chain before making a brand new one.
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parent
b6097cf724
commit
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4 changed files with 40 additions and 30 deletions
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@ -15,6 +15,12 @@
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namespace Web::Layout {
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struct FormattingState {
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FormattingState() { }
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explicit FormattingState(FormattingState const* parent)
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: m_parent(parent)
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{
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}
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struct NodeState {
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float content_width { 0 };
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float content_height { 0 };
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@ -65,31 +71,17 @@ struct FormattingState {
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}
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Optional<LineBoxFragmentCoordinate> containing_line_box_fragment;
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// NOTE: NodeState is ref-counted and accessed via copy-on-write helpers below.
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size_t ref_count { 1 };
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void ref()
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{
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VERIFY(ref_count);
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++ref_count;
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}
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void unref()
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{
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VERIFY(ref_count);
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if (!--ref_count)
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delete this;
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}
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};
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void commit();
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// NOTE: get_mutable() will CoW the NodeState if it's shared with another FormattingContext.
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// NOTE: get_mutable() will CoW the NodeState if it's inherited from an ancestor state;
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NodeState& get_mutable(NodeWithStyleAndBoxModelMetrics const&);
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// NOTE: get() will not CoW the NodeState.
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NodeState const& get(NodeWithStyleAndBoxModelMetrics const&) const;
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HashMap<NodeWithStyleAndBoxModelMetrics const*, NonnullRefPtr<NodeState>> nodes;
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HashMap<NodeWithStyleAndBoxModelMetrics const*, NonnullOwnPtr<NodeState>> nodes;
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// We cache intrinsic sizes once determined, as they will not change over the course of a full layout.
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// This avoids computing them several times while performing flex layout.
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@ -98,6 +90,8 @@ struct FormattingState {
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Gfx::FloatSize max_content_size;
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};
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HashMap<NodeWithStyleAndBoxModelMetrics const*, IntrinsicSizes> mutable intrinsic_sizes;
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FormattingState const* m_parent { nullptr };
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};
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Gfx::FloatRect absolute_content_rect(Box const&, FormattingState const&);
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