jiuyiUniapp/service/node_modules/react-native/ReactCommon/react/renderer/mounting/updateMountedFlag.cpp

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2025-02-13 09:59:20 +08:00
/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/
#include "updateMountedFlag.h"
namespace facebook::react {
void updateMountedFlag(
const ShadowNode::ListOfShared& oldChildren,
const ShadowNode::ListOfShared& newChildren) {
// This is a simplified version of Diffing algorithm that only updates
// `mounted` flag on `ShadowNode`s. The algorithm sets "mounted" flag before
// "unmounted" to allow `ShadowNode` detect a situation where the node was
// remounted.
if (&oldChildren == &newChildren) {
// Lists are identical, nothing to do.
return;
}
if (oldChildren.empty() && newChildren.empty()) {
// Both lists are empty, nothing to do.
return;
}
size_t index = 0;
// Stage 1: Mount and unmount "updated" children.
for (index = 0; index < oldChildren.size() && index < newChildren.size();
index++) {
const auto& oldChild = oldChildren[index];
const auto& newChild = newChildren[index];
if (oldChild == newChild) {
// Nodes are identical, skipping the subtree.
continue;
}
if (!ShadowNode::sameFamily(*oldChild, *newChild)) {
// Totally different nodes, updating is impossible.
break;
}
newChild->setMounted(true);
oldChild->setMounted(false);
updateMountedFlag(oldChild->getChildren(), newChild->getChildren());
}
size_t lastIndexAfterFirstStage = index;
// State 2: Mount new children.
for (index = lastIndexAfterFirstStage; index < newChildren.size(); index++) {
const auto& newChild = newChildren[index];
newChild->setMounted(true);
updateMountedFlag({}, newChild->getChildren());
}
// State 3: Unmount old children.
for (index = lastIndexAfterFirstStage; index < oldChildren.size(); index++) {
const auto& oldChild = oldChildren[index];
oldChild->setMounted(false);
updateMountedFlag(oldChild->getChildren(), {});
}
}
} // namespace facebook::react