From ba45895a3f7b54cf2b0bf93daaf6b362726e14df Mon Sep 17 00:00:00 2001
From: Valentin Shergin <shergin@fb.com>
Date: Tue, 10 Apr 2018 12:46:20 -0700
Subject: [PATCH] Fabric: Introducing Scheduler

Summary: Scheduler coordinates Shadow Tree updates and event flows (not yet).

Reviewed By: mdvacca

Differential Revision: D7503387

fbshipit-source-id: 4cb8bc574c25a0fd2ace6319c26c644a1e4757a9
---
 ReactCommon/fabric/uimanager/Scheduler.cpp    | 108 ++++++++++++++++++
 ReactCommon/fabric/uimanager/Scheduler.h      |  74 ++++++++++++
 .../fabric/uimanager/SchedulerDelegate.h      |  33 ++++++
 3 files changed, 215 insertions(+)
 create mode 100644 ReactCommon/fabric/uimanager/Scheduler.cpp
 create mode 100644 ReactCommon/fabric/uimanager/Scheduler.h
 create mode 100644 ReactCommon/fabric/uimanager/SchedulerDelegate.h

diff --git a/ReactCommon/fabric/uimanager/Scheduler.cpp b/ReactCommon/fabric/uimanager/Scheduler.cpp
new file mode 100644
index 000000000..b2571ebf6
--- /dev/null
+++ b/ReactCommon/fabric/uimanager/Scheduler.cpp
@@ -0,0 +1,108 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+#include "Scheduler.h"
+
+#include <fabric/core/LayoutContext.h>
+#include <fabric/uimanager/ComponentDescriptorRegistry.h>
+#include <fabric/uimanager/FabricUIManager.h>
+#include <fabric/view/ViewComponentDescriptor.h>
+#include <fabric/view/ViewProps.h>
+#include <fabric/view/ViewShadowNode.h>
+
+#include "Differentiator.h"
+
+namespace facebook {
+namespace react {
+
+Scheduler::Scheduler() {
+  auto componentDescriptorRegistry = std::make_shared<ComponentDescriptorRegistry>();
+  SharedComponentDescriptor viewComponentDescriptor = std::make_shared<ViewComponentDescriptor>();
+  componentDescriptorRegistry->registerComponentDescriptor(viewComponentDescriptor);
+
+  uiManager_ = std::make_shared<FabricUIManager>(componentDescriptorRegistry);
+  uiManager_->setDelegate(this);
+}
+
+Scheduler::~Scheduler() {
+  uiManager_->setDelegate(nullptr);
+}
+
+void Scheduler::registerRootTag(Tag rootTag) {
+  auto rootShadowNode = std::make_shared<RootShadowNode>(rootTag, rootTag, nullptr);
+  rootNodeRegistry_.insert({rootTag, rootShadowNode});
+}
+
+void Scheduler::unregisterRootTag(Tag rootTag) {
+  rootNodeRegistry_.erase(rootTag);
+}
+
+#pragma mark - Delegate
+
+void Scheduler::setDelegate(SchedulerDelegate *delegate) {
+  delegate_ = delegate;
+}
+
+SchedulerDelegate *Scheduler::getDelegate() {
+  return delegate_;
+}
+
+#pragma mark - UIManagerDelegate
+  
+void Scheduler::uiManagerDidFinishTransaction(Tag rootTag, const SharedShadowNodeUnsharedList &rootChildNodes) {
+  SharedRootShadowNode oldRootShadowNode = rootNodeRegistry_[rootTag];
+  assert(oldRootShadowNode);
+
+  SharedRootShadowNode newRootShadowNode =
+    std::make_shared<RootShadowNode>(oldRootShadowNode, nullptr, SharedShadowNodeSharedList(rootChildNodes));
+
+  auto nonConstOldRootShadowNode = std::const_pointer_cast<RootShadowNode>(oldRootShadowNode);
+  auto nonConstNewRootShadowNode = std::const_pointer_cast<RootShadowNode>(newRootShadowNode);
+
+  LayoutContext layoutContext = LayoutContext();
+  layoutContext.affectedShadowNodes = std::make_shared<std::unordered_set<SharedLayoutableShadowNode>>();
+
+  LOG(INFO) << "Old Shadow Tree: \n" << oldRootShadowNode->getDebugDescription();
+  LOG(INFO) << "New Shadow Tree *before* layout: \n" << newRootShadowNode->getDebugDescription();
+
+  nonConstNewRootShadowNode->layout(layoutContext);
+
+  nonConstNewRootShadowNode->sealRecursive();
+
+  LOG(INFO) << "New Shadow Tree *after* layout: \n" << nonConstNewRootShadowNode->getDebugDescription();
+
+  TreeMutationInstructionList instructions = TreeMutationInstructionList();
+
+  calculateMutationInstructions(
+    instructions,
+    oldRootShadowNode,
+    oldRootShadowNode->ShadowNode::getChildren(),
+    newRootShadowNode->ShadowNode::getChildren()
+  );
+
+  LOG(INFO) << "TreeMutationInstructionList:";
+
+  for (auto instruction : instructions) {
+    LOG(INFO) << "Instruction: " << instruction.getDebugDescription();
+  }
+
+  rootNodeRegistry_[rootTag] = newRootShadowNode;
+
+  if (delegate_) {
+    delegate_->schedulerDidComputeMutationInstructions(rootTag, instructions);
+  }
+}
+
+void Scheduler::uiManagerDidCreateShadowNode(const SharedShadowNode &shadowNode) {
+  if (delegate_) {
+    delegate_->schedulerDidRequestPreliminaryViewAllocation(shadowNode->getComponentName());
+  }
+}
+
+#pragma mark - Deprecated
+
+std::shared_ptr<FabricUIManager> Scheduler::getUIManager_DO_NOT_USE() {
+  return uiManager_;
+}
+
+} // namespace react
+} // namespace facebook
diff --git a/ReactCommon/fabric/uimanager/Scheduler.h b/ReactCommon/fabric/uimanager/Scheduler.h
new file mode 100644
index 000000000..4f4ff203b
--- /dev/null
+++ b/ReactCommon/fabric/uimanager/Scheduler.h
@@ -0,0 +1,74 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+#pragma once
+
+#include <memory>
+
+#include <fabric/core/ComponentDescriptor.h>
+#include <fabric/core/LayoutConstraints.h>
+#include <fabric/uimanager/SchedulerDelegate.h>
+#include <fabric/uimanager/UIManagerDelegate.h>
+#include <fabric/view/ViewShadowNode.h>
+
+namespace facebook {
+namespace react {
+
+/*
+ * We expect having a dedicated subclass for root shadow node.
+ */
+using SharedRootShadowNode = SharedViewShadowNode;
+using RootShadowNode = ViewShadowNode;
+
+class FabricUIManager;
+
+/*
+ * Scheduler coordinates Shadow Tree updates and event flows.
+ */
+class Scheduler:
+  public UIManagerDelegate {
+
+public:
+  Scheduler();
+  ~Scheduler();
+
+#pragma mark - Root Nodes Managerment
+
+  void registerRootTag(Tag rootTag);
+  void unregisterRootTag(Tag rootTag);
+
+  void setLayoutConstraints(Tag rootTag, LayoutConstraints layoutConstraints);
+
+#pragma mark - Delegate
+
+  /*
+   * Sets and gets the Scheduler's delegate.
+   * The delegate is stored as a raw pointer, so the owner must null
+   * the pointer before being destroyed.
+   */
+  void setDelegate(SchedulerDelegate *delegate);
+  SchedulerDelegate *getDelegate();
+
+#pragma mark - UIManagerDelegate
+
+  void uiManagerDidFinishTransaction(Tag rootTag, const SharedShadowNodeUnsharedList &rootChildNodes) override;
+  void uiManagerDidCreateShadowNode(const SharedShadowNode &shadowNode) override;
+
+#pragma mark - Deprecated
+
+  /*
+   * UIManager instance must be temporarily exposed for registration purposes.
+   */
+  std::shared_ptr<FabricUIManager> getUIManager_DO_NOT_USE();
+
+private:
+  SchedulerDelegate *delegate_;
+  std::shared_ptr<FabricUIManager> uiManager_;
+
+  /*
+   * All commited `RootShadowNode` instances to differentiate against.
+   */
+  std::unordered_map<Tag, SharedRootShadowNode> rootNodeRegistry_;
+};
+
+} // namespace react
+} // namespace facebook
diff --git a/ReactCommon/fabric/uimanager/SchedulerDelegate.h b/ReactCommon/fabric/uimanager/SchedulerDelegate.h
new file mode 100644
index 000000000..2fe3da02a
--- /dev/null
+++ b/ReactCommon/fabric/uimanager/SchedulerDelegate.h
@@ -0,0 +1,33 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+#pragma once
+
+#include <memory>
+
+#include <fabric/core/ReactPrimitives.h>
+#include <fabric/core/ShadowNode.h>
+#include <fabric/uimanager/TreeMutationInstruction.h>
+
+namespace facebook {
+namespace react {
+
+/*
+ * Abstract class for Scheduler's delegate.
+ */
+class SchedulerDelegate {
+public:
+  /*
+   * Called right after Scheduler computed (and laid out) a new updated version
+   * of the tree and calculated a set of mutation instructions which are
+   * suffisient to construct a new one.
+   */
+  virtual void schedulerDidComputeMutationInstructions(Tag rootTag, const TreeMutationInstructionList &instructions) = 0;
+
+  /*
+   * Called right after a new ShadowNode was created.
+   */
+  virtual void schedulerDidRequestPreliminaryViewAllocation(ComponentName componentName) = 0;
+};
+
+} // namespace react
+} // namespace facebook