54 lines
2.0 KiB
C++
54 lines
2.0 KiB
C++
/*
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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#pragma once
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#include <deque>
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#include "CullingContext.h"
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namespace facebook::react {
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struct ShadowViewNodePair;
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/**
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* During differ, we need to keep some `ShadowViewNodePair`s in memory.
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* Some `ShadowViewNodePair`s are referenced from std::vectors returned
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* by `sliceChildShadowNodeViewPairs`; some are referenced in TinyMaps
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* for view (un)flattening especially; and it is not always clear which
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* std::vectors will outlive which TinyMaps, and vice-versa, so it doesn't
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* make sense for the std::vector or TinyMap to own any `ShadowViewNodePair`s.
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*
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* Thus, we introduce the concept of a scope.
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*
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* For the duration of some operation, we keep a ViewNodePairScope around, such
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* that: (1) the ViewNodePairScope keeps each
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* ShadowViewNodePair alive, (2) we have a stable pointer value that we can
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* use to reference each ShadowViewNodePair (not guaranteed with std::vector,
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* for example, which may have to resize and move values around).
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*
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* As long as we only manipulate the data-structure with push_back, std::deque
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* both (1) ensures that pointers into the data-structure are never invalidated,
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* and (2) tries to efficiently allocate storage such that as many objects as
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* possible are close in memory, but does not guarantee adjacency.
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*/
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using ViewNodePairScope = std::deque<ShadowViewNodePair>;
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/**
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* Generates a list of `ShadowViewNodePair`s that represents a layer of a
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* flattened view hierarchy. The V2 version preserves nodes even if they do
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* not form views and their children are flattened.
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*/
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std::vector<ShadowViewNodePair*> sliceChildShadowNodeViewPairs(
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const ShadowViewNodePair& shadowNodePair,
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ViewNodePairScope& viewNodePairScope,
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bool allowFlattened,
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Point layoutOffset,
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const CullingContext& cullingContext);
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} // namespace facebook::react
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