408 строки
12 KiB
C++
408 строки
12 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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#include "ShadowTree.h"
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#include <react/components/root/RootComponentDescriptor.h>
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#include <react/components/view/ViewShadowNode.h>
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#include <react/core/LayoutContext.h>
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#include <react/core/LayoutPrimitives.h>
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#include <react/debug/SystraceSection.h>
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#include <react/mounting/MountingTelemetry.h>
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#include <react/mounting/ShadowTreeRevision.h>
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#include <react/mounting/ShadowViewMutation.h>
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#include "ShadowTreeDelegate.h"
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#include "TreeStateReconciliation.h"
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namespace facebook {
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namespace react {
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/*
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* Generates (possibly) a new tree where all nodes with non-obsolete `State`
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* objects. If all `State` objects in the tree are not obsolete for the moment
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* of calling, the function returns `nullptr` (as an indication that no
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* additional work is required).
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*/
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static ShadowNode::Unshared progressState(ShadowNode const &shadowNode) {
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auto isStateChanged = false;
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auto areChildrenChanged = false;
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auto newState = shadowNode.getState();
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if (newState) {
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newState = newState->getMostRecentStateIfObsolete();
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if (newState) {
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isStateChanged = true;
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}
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}
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auto newChildren = ShadowNode::ListOfShared{};
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if (!shadowNode.getChildren().empty()) {
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auto index = size_t{0};
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for (auto const &childNode : shadowNode.getChildren()) {
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auto newChildNode = progressState(*childNode);
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if (newChildNode) {
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if (!areChildrenChanged) {
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// Making a copy before the first mutation.
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newChildren = shadowNode.getChildren();
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}
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newChildren[index] = newChildNode;
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areChildrenChanged = true;
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}
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index++;
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}
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}
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if (!areChildrenChanged && !isStateChanged) {
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return nullptr;
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}
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return shadowNode.clone({
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ShadowNodeFragment::propsPlaceholder(),
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areChildrenChanged ? std::make_shared<ShadowNode::ListOfShared const>(
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std::move(newChildren))
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: ShadowNodeFragment::childrenPlaceholder(),
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isStateChanged ? newState : ShadowNodeFragment::statePlaceholder(),
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});
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}
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/*
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* An optimized version of the previous function (and relies on it).
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* The function uses a given base tree to exclude unchanged (equal) parts
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* of the three from the traversing.
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*/
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static ShadowNode::Unshared progressState(
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ShadowNode const &shadowNode,
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ShadowNode const &baseShadowNode) {
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// The intuition behind the complexity:
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// - A very few nodes have associated state, therefore it's mostly reading and
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// it only writes when state objects were found obsolete;
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// - Most before-after trees are aligned, therefore most tree branches will be
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// skipped;
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// - If trees are significantly different, any other algorithm will have
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// close to linear complexity.
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auto isStateChanged = false;
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auto areChildrenChanged = false;
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auto newState = shadowNode.getState();
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if (newState) {
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newState = newState->getMostRecentStateIfObsolete();
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if (newState) {
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isStateChanged = true;
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}
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}
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auto &children = shadowNode.getChildren();
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auto &baseChildren = baseShadowNode.getChildren();
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auto newChildren = ShadowNode::ListOfShared{};
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auto childrenSize = children.size();
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auto baseChildrenSize = baseChildren.size();
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auto index = size_t{0};
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// Stage 1: Aligned part.
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for (index = 0; index < childrenSize && index < baseChildrenSize; index++) {
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const auto &childNode = *children.at(index);
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const auto &baseChildNode = *baseChildren.at(index);
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if (&childNode == &baseChildNode) {
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// Nodes are identical, skipping.
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continue;
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}
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if (!ShadowNode::sameFamily(childNode, baseChildNode)) {
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// Totally different nodes, updating is impossible.
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break;
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}
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auto newChildNode = progressState(childNode, baseChildNode);
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if (newChildNode) {
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if (!areChildrenChanged) {
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// Making a copy before the first mutation.
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newChildren = children;
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}
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newChildren[index] = newChildNode;
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areChildrenChanged = true;
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}
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}
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// Stage 2: Misaligned part.
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for (; index < childrenSize; index++) {
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auto newChildNode = progressState(*children.at(index));
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if (newChildNode) {
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if (!areChildrenChanged) {
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// Making a copy before the first mutation.
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newChildren = children;
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}
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newChildren[index] = newChildNode;
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areChildrenChanged = true;
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}
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}
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if (!areChildrenChanged && !isStateChanged) {
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return nullptr;
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}
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return shadowNode.clone({
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ShadowNodeFragment::propsPlaceholder(),
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areChildrenChanged ? std::make_shared<ShadowNode::ListOfShared const>(
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std::move(newChildren))
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: ShadowNodeFragment::childrenPlaceholder(),
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isStateChanged ? newState : ShadowNodeFragment::statePlaceholder(),
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});
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}
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static void updateMountedFlag(
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const SharedShadowNodeList &oldChildren,
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const SharedShadowNodeList &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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int index;
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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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int 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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ShadowTree::ShadowTree(
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SurfaceId surfaceId,
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LayoutConstraints const &layoutConstraints,
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LayoutContext const &layoutContext,
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RootComponentDescriptor const &rootComponentDescriptor,
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ShadowTreeDelegate const &delegate,
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std::weak_ptr<MountingOverrideDelegate const> mountingOverrideDelegate)
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: surfaceId_(surfaceId), delegate_(delegate) {
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const auto noopEventEmitter = std::make_shared<const ViewEventEmitter>(
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nullptr, -1, std::shared_ptr<const EventDispatcher>());
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const auto props = std::make_shared<const RootProps>(
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*RootShadowNode::defaultSharedProps(), layoutConstraints, layoutContext);
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auto family = rootComponentDescriptor.createFamily(
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ShadowNodeFamilyFragment{surfaceId, surfaceId, noopEventEmitter},
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nullptr);
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rootShadowNode_ = std::static_pointer_cast<const RootShadowNode>(
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rootComponentDescriptor.createShadowNode(
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ShadowNodeFragment{
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/* .props = */ props,
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},
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family));
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mountingCoordinator_ = std::make_shared<MountingCoordinator const>(
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ShadowTreeRevision{rootShadowNode_, 0, {}}, mountingOverrideDelegate);
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}
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ShadowTree::~ShadowTree() {
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mountingCoordinator_->revoke();
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}
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Tag ShadowTree::getSurfaceId() const {
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return surfaceId_;
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}
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MountingCoordinator::Shared ShadowTree::getMountingCoordinator() const {
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return mountingCoordinator_;
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}
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void ShadowTree::commit(
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ShadowTreeCommitTransaction transaction,
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bool enableStateReconciliation) const {
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SystraceSection s("ShadowTree::commit");
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int attempts = 0;
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while (true) {
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attempts++;
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if (tryCommit(transaction, enableStateReconciliation)) {
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return;
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}
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// After multiple attempts, we failed to commit the transaction.
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// Something internally went terribly wrong.
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assert(attempts < 1024);
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}
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}
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bool ShadowTree::tryCommit(
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ShadowTreeCommitTransaction transaction,
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bool enableStateReconciliation) const {
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SystraceSection s("ShadowTree::tryCommit");
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auto telemetry = MountingTelemetry{};
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telemetry.willCommit();
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RootShadowNode::Shared oldRootShadowNode;
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{
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// Reading `rootShadowNode_` in shared manner.
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std::shared_lock<better::shared_mutex> lock(commitMutex_);
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oldRootShadowNode = rootShadowNode_;
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}
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RootShadowNode::Unshared newRootShadowNode = transaction(oldRootShadowNode);
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if (!newRootShadowNode) {
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return false;
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}
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if (enableStateReconciliation) {
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if (enableNewStateReconciliation_) {
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auto updatedNewRootShadowNode =
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progressState(*newRootShadowNode, *oldRootShadowNode);
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if (updatedNewRootShadowNode) {
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newRootShadowNode =
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std::static_pointer_cast<RootShadowNode>(updatedNewRootShadowNode);
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}
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} else {
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// Compare state revisions of old and new root
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// Children of the root node may be mutated in-place
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UnsharedShadowNode reconciledNode =
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reconcileStateWithTree(newRootShadowNode.get(), oldRootShadowNode);
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if (reconciledNode != nullptr) {
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newRootShadowNode = std::make_shared<RootShadowNode>(
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*reconciledNode, ShadowNodeFragment{});
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}
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}
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}
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// Layout nodes
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std::vector<LayoutableShadowNode const *> affectedLayoutableNodes{};
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affectedLayoutableNodes.reserve(1024);
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telemetry.willLayout();
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newRootShadowNode->layoutIfNeeded(&affectedLayoutableNodes);
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telemetry.didLayout();
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// Seal the shadow node so it can no longer be mutated
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newRootShadowNode->sealRecursive();
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auto revisionNumber = ShadowTreeRevision::Number{};
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{
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// Updating `rootShadowNode_` in unique manner if it hasn't changed.
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std::unique_lock<better::shared_mutex> lock(commitMutex_);
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if (rootShadowNode_ != oldRootShadowNode) {
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return false;
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}
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rootShadowNode_ = newRootShadowNode;
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{
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std::lock_guard<std::mutex> dispatchLock(EventEmitter::DispatchMutex());
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updateMountedFlag(
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oldRootShadowNode->getChildren(), newRootShadowNode->getChildren());
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}
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revisionNumber_++;
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revisionNumber = revisionNumber_;
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}
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emitLayoutEvents(affectedLayoutableNodes);
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telemetry.didCommit();
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mountingCoordinator_->push(
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ShadowTreeRevision{newRootShadowNode, revisionNumber, telemetry});
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notifyDelegatesOfUpdates();
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return true;
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}
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void ShadowTree::commitEmptyTree() const {
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commit(
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[](RootShadowNode::Shared const &oldRootShadowNode)
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-> RootShadowNode::Unshared {
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return std::make_shared<RootShadowNode>(
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*oldRootShadowNode,
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ShadowNodeFragment{
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/* .props = */ ShadowNodeFragment::propsPlaceholder(),
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/* .children = */ ShadowNode::emptySharedShadowNodeSharedList(),
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});
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});
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}
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void ShadowTree::emitLayoutEvents(
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std::vector<LayoutableShadowNode const *> &affectedLayoutableNodes) const {
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SystraceSection s("ShadowTree::emitLayoutEvents");
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for (auto const *layoutableNode : affectedLayoutableNodes) {
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// Only instances of `ViewShadowNode` (and subclasses) are supported.
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auto const &viewShadowNode =
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static_cast<ViewShadowNode const &>(*layoutableNode);
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auto const &viewEventEmitter = static_cast<ViewEventEmitter const &>(
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*viewShadowNode.getEventEmitter());
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// Checking if the `onLayout` event was requested for the particular Shadow
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// Node.
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auto const &viewProps =
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static_cast<ViewProps const &>(*viewShadowNode.getProps());
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if (!viewProps.onLayout) {
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continue;
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}
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viewEventEmitter.onLayout(layoutableNode->getLayoutMetrics());
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}
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}
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void ShadowTree::notifyDelegatesOfUpdates() const {
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delegate_.shadowTreeDidFinishTransaction(*this, mountingCoordinator_);
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}
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} // namespace react
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} // namespace facebook
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