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LibWeb: Make Layout::FormattingState copies shallow

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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.
This commit is contained in:
Andreas Kling 2022-03-12 16:33:11 +01:00
parent b6097cf724
commit 515db5fc1b
4 changed files with 40 additions and 30 deletions
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8
Userland/Libraries/LibWeb/Layout/FlexFormattingContext.cpp
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@ -440,7 +440,7 @@ float FlexFormattingContext::calculate_indefinite_main_size(FlexItem const& item
if (has_definite_cross_size(item.box)) {
// For indefinite main sizes, we perform a throwaway layout and then measure it.
auto throwaway_state = m_state;
FormattingState throwaway_state(&m_state);
auto& box_state = throwaway_state.get_mutable(item.box);
// Item has definite cross size, layout with that as the used cross size.
@ -470,7 +470,7 @@ float FlexFormattingContext::calculate_indefinite_main_size(FlexItem const& item
// then layout with that and see what height comes out of it.
float fit_content_cross_size = calculate_fit_content_width(item.box, m_available_space->cross);
auto throwaway_state = m_state;
FormattingState throwaway_state(&m_state);
auto& box_state = throwaway_state.get_mutable(item.box);
// Item has definite cross size, layout with that as the used cross size.
@ -814,7 +814,7 @@ void FlexFormattingContext::determine_hypothetical_cross_size_of_item(FlexItem&
if (has_definite_main_size(item.box)) {
// For indefinite cross sizes, we perform a throwaway layout and then measure it.
auto throwaway_state = m_state;
FormattingState throwaway_state(&m_state);
auto& box_state = throwaway_state.get_mutable(item.box);
// Item has definite main size, layout with that as the used main size.
@ -842,7 +842,7 @@ void FlexFormattingContext::determine_hypothetical_cross_size_of_item(FlexItem&
else
fit_content_main_size = calculate_fit_content_height(item.box, m_available_space->main);
auto throwaway_state = m_state;
FormattingState throwaway_state(&m_state);
auto& box_state = throwaway_state.get_mutable(item.box);
// Item has definite main size, layout with that as the used main size.