From 2c28310267e68d3ac75615d27e22126202bd5411 Mon Sep 17 00:00:00 2001
From: Valentin Shergin <shergin@fb.com>
Date: Sun, 15 Jul 2018 16:46:24 -0700
Subject: [PATCH] Fabric: Computed attributed string caching inside <Paragraph>

Summary:
@public
Quite trivial. We had to have this from the day one.
We don't need cache invalidation policy because all subtree is immutable.

Reviewed By: mdvacca

Differential Revision: D8709973

fbshipit-source-id: bd7fcf0ae1dcb23894321cb5d16da18cb1ab788f
---
 ReactCommon/fabric/attributedstring/AttributedString.h    | 1 -
 ReactCommon/fabric/text/basetext/BaseTextShadowNode.cpp   | 2 --
 ReactCommon/fabric/text/paragraph/ParagraphShadowNode.cpp | 7 ++++++-
 ReactCommon/fabric/text/paragraph/ParagraphShadowNode.h   | 7 +++++++
 4 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/ReactCommon/fabric/attributedstring/AttributedString.h b/ReactCommon/fabric/attributedstring/AttributedString.h
index 07cc47603e4..4fa5ac9b466 100644
--- a/ReactCommon/fabric/attributedstring/AttributedString.h
+++ b/ReactCommon/fabric/attributedstring/AttributedString.h
@@ -72,4 +72,3 @@ private:
 
 } // namespace react
 } // namespace facebook
-
diff --git a/ReactCommon/fabric/text/basetext/BaseTextShadowNode.cpp b/ReactCommon/fabric/text/basetext/BaseTextShadowNode.cpp
index f2f2d08a7ee..ec97f412444 100644
--- a/ReactCommon/fabric/text/basetext/BaseTextShadowNode.cpp
+++ b/ReactCommon/fabric/text/basetext/BaseTextShadowNode.cpp
@@ -20,8 +20,6 @@ AttributedString BaseTextShadowNode::getAttributedString(
   const TextAttributes &textAttributes,
   const SharedShadowNodeSharedList &childNodes
 ) const {
-  // TODO: Implement caching.
-
   AttributedString attributedString;
 
   for (const auto &childNode : *childNodes) {
diff --git a/ReactCommon/fabric/text/paragraph/ParagraphShadowNode.cpp b/ReactCommon/fabric/text/paragraph/ParagraphShadowNode.cpp
index e7b6513ba23..99222fc317f 100644
--- a/ReactCommon/fabric/text/paragraph/ParagraphShadowNode.cpp
+++ b/ReactCommon/fabric/text/paragraph/ParagraphShadowNode.cpp
@@ -19,7 +19,12 @@ ComponentName ParagraphShadowNode::getComponentName() const {
 }
 
 AttributedString ParagraphShadowNode::getAttributedString() const {
-  return BaseTextShadowNode::getAttributedString(getProps()->textAttributes, getChildren());
+  if (!cachedAttributedString_.has_value()) {
+    cachedAttributedString_ =
+      BaseTextShadowNode::getAttributedString(getProps()->textAttributes, getChildren());
+  }
+
+  return cachedAttributedString_.value();
 }
 
 void ParagraphShadowNode::setTextLayoutManager(SharedTextLayoutManager textLayoutManager) {
diff --git a/ReactCommon/fabric/text/paragraph/ParagraphShadowNode.h b/ReactCommon/fabric/text/paragraph/ParagraphShadowNode.h
index df16aee1b79..f7b1ea4fd2a 100644
--- a/ReactCommon/fabric/text/paragraph/ParagraphShadowNode.h
+++ b/ReactCommon/fabric/text/paragraph/ParagraphShadowNode.h
@@ -14,6 +14,7 @@
 #include <fabric/text/TextShadowNode.h>
 #include <fabric/textlayoutmanager/TextLayoutManager.h>
 #include <fabric/view/ConcreteViewShadowNode.h>
+#include <folly/Optional.h>
 
 namespace facebook {
 namespace react {
@@ -63,6 +64,12 @@ private:
   void updateLocalData();
 
   SharedTextLayoutManager textLayoutManager_;
+
+  /*
+   * Cached attributed string that represents the content of the subtree started
+   * from the node.
+   */
+  mutable folly::Optional<AttributedString> cachedAttributedString_ {};
 };
 
 } // namespace react