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Valentin Shergin
ea8a57116f
Summary: Previously we computed the list of nodes that need to be notified about layout changes using a list of mutation instructions. That was fine, but that's not really compatible with some other changes that I plan to make, so I decided to change it (make it better). Besides the better design (debatable; fewer dependencies to unrelated moving pieces), here is why I believe the new way is more performant: * The new approach has no `dynamic_casts`, whereas the previous has tons of them (two per a mutation). If a `dynamic_cast` takes 10 ns, for 500 nodes it can take up to 5ms only for casts. (Non-scientific assumption.) * After removing dependency to mutation instruction, we can enable flattening for views which have `onLayout` event. Reviewed By: mdvacca Differential Revision: D15110725 fbshipit-source-id: 31a657ccfd02441734ad1d71a833653223163289
48 lines
1.3 KiB
C++
48 lines
1.3 KiB
C++
/**
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* Copyright (c) Facebook, Inc. and its 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 <vector>
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#include <react/core/LayoutableShadowNode.h>
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#include <react/graphics/Geometry.h>
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namespace facebook {
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namespace react {
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/*
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* LayoutContext: Additional contextual information useful for particular
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* layout approaches.
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*/
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struct LayoutContext {
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/*
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* Compound absolute position of the node relative to the root node.
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*/
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Point absolutePosition{0, 0};
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/*
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* Reflects the scale factor needed to convert from the logical coordinate
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* space into the device coordinate space of the physical screen.
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* Some layout systems *might* use this to round layout metric values
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* to `pixel value`.
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*/
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Float pointScaleFactor{1.0};
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/*
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* A raw pointer to list of raw pointers to `LayoutableShadowNode`s that were
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* affected by the re-layout pass. If the field is not `nullptr`, a particular
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* `LayoutableShadowNode` implementation should add mutated nodes to this
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* list. The order is not specified. Nothing in this collection is owing (on
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* purpose), make sure the memory is managed responsibly.
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*/
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std::vector<LayoutableShadowNode const *> *affectedNodes{};
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};
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} // namespace react
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} // namespace facebook
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