70 lines
2.0 KiB
C++
70 lines
2.0 KiB
C++
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/*
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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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#include "updateMountedFlag.h"
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namespace facebook::react {
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void updateMountedFlag(
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const ShadowNode::ListOfShared& oldChildren,
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const ShadowNode::ListOfShared& newChildren) {
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// This is a simplified version of Diffing algorithm that only updates
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// `mounted` flag on `ShadowNode`s. The algorithm sets "mounted" flag before
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// "unmounted" to allow `ShadowNode` detect a situation where the node was
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// remounted.
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if (&oldChildren == &newChildren) {
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// Lists are identical, nothing to do.
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return;
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}
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if (oldChildren.empty() && newChildren.empty()) {
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// Both lists are empty, nothing to do.
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return;
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}
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size_t index = 0;
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// Stage 1: Mount and unmount "updated" children.
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for (index = 0; index < oldChildren.size() && index < newChildren.size();
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index++) {
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const auto& oldChild = oldChildren[index];
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const auto& newChild = newChildren[index];
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if (oldChild == newChild) {
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// Nodes are identical, skipping the subtree.
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continue;
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}
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if (!ShadowNode::sameFamily(*oldChild, *newChild)) {
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// Totally different nodes, updating is impossible.
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break;
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}
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newChild->setMounted(true);
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oldChild->setMounted(false);
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updateMountedFlag(oldChild->getChildren(), newChild->getChildren());
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}
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size_t lastIndexAfterFirstStage = index;
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// State 2: Mount new children.
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for (index = lastIndexAfterFirstStage; index < newChildren.size(); index++) {
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const auto& newChild = newChildren[index];
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newChild->setMounted(true);
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updateMountedFlag({}, newChild->getChildren());
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}
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// State 3: Unmount old children.
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for (index = lastIndexAfterFirstStage; index < oldChildren.size(); index++) {
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const auto& oldChild = oldChildren[index];
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oldChild->setMounted(false);
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updateMountedFlag(oldChild->getChildren(), {});
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}
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}
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} // namespace facebook::react
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