Improve caching of Text per shadow Node

Summary:
This diff optimizes text measurement by adding a layer of caching per shadow node.
When ReactFeatureFlags.enableTextMeasureCachePerShadowNode is enabled, we will cache and reused measurements per shadow node.
This optimization showed a 2x improvement on text rendearing when a screen contains a big amount of text components.

Changelog: [Internal] Internal

Reviewed By: sammy-SC

Differential Revision: D44221170

fbshipit-source-id: c3e7ba1ad216929826a99585874981717c90e13b

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/config/ReactFeatureFlags.java

@@ -75,6 +75,9 @@ public class ReactFeatureFlags {
   /** Feature Flag to enable the pending event queue in fabric before mounting views */
   public static boolean enableFabricPendingEventQueue = false;
 
+  /** Feature Flag to enable caching mechanism of text measurement at shadow node level */
+  public static boolean enableTextMeasureCachePerShadowNode = false;
+
   /**
    * Feature flag that controls how turbo modules are exposed to JS
    *

packages/react-native/ReactAndroid/src/main/jni/react/fabric/Binding.cpp

@@ -429,6 +429,9 @@ void Binding::installFabricUIManager(
       "CalculateTransformedFramesEnabled",
       getFeatureFlagValue("calculateTransformedFramesEnabled"));
 
+  CoreFeatures::cacheLastTextMeasurement =
+      getFeatureFlagValue("enableTextMeasureCachePerShadowNode");
+
   // Props setter pattern feature
   CoreFeatures::enablePropIteratorSetter =
       getFeatureFlagValue("enableCppPropsIteratorSetter");

packages/react-native/ReactCommon/react/renderer/components/text/ParagraphLayoutManager.cpp

@@ -15,6 +15,19 @@ TextMeasurement ParagraphLayoutManager::measure(
     AttributedString const &attributedString,
     ParagraphAttributes const &paragraphAttributes,
     LayoutConstraints layoutConstraints) const {
+  bool cacheLastTextMeasurement = CoreFeatures::cacheLastTextMeasurement;
+  if (cacheLastTextMeasurement &&
+      (layoutConstraints.maximumSize.width == availableWidth_ ||
+       layoutConstraints.maximumSize.width ==
+           cachedTextMeasurement_.size.width)) {
+    /* Yoga has requested measurement for this size before. Let's use cached
+     * value. `TextLayoutManager` might not have cached this because it could be
+     * using different width to generate cache key. This happens because Yoga
+     * switches between available width and exact width but since we already
+     * know exact width, it is wasteful to calculate it again.
+     */
+    return cachedTextMeasurement_;
+  }
   if (CoreFeatures::cacheNSTextStorage) {
     size_t newHash = folly::hash::hash_combine(
         0,
@@ -28,11 +41,23 @@ TextMeasurement ParagraphLayoutManager::measure(
     }
   }
 
-  return textLayoutManager_->measure(
-      AttributedStringBox(attributedString),
-      paragraphAttributes,
-      layoutConstraints,
-      hostTextStorage_);
+  if (cacheLastTextMeasurement) {
+    cachedTextMeasurement_ = textLayoutManager_->measure(
+        AttributedStringBox(attributedString),
+        paragraphAttributes,
+        layoutConstraints,
+        hostTextStorage_);
+
+    availableWidth_ = layoutConstraints.maximumSize.width;
+
+    return cachedTextMeasurement_;
+  } else {
+    return textLayoutManager_->measure(
+        AttributedStringBox(attributedString),
+        paragraphAttributes,
+        layoutConstraints,
+        hostTextStorage_);
+  }
 }
 
 LinesMeasurements ParagraphLayoutManager::measureLines(

packages/react-native/ReactCommon/react/renderer/components/text/ParagraphLayoutManager.h

@@ -54,6 +54,18 @@ class ParagraphLayoutManager {
   std::shared_ptr<TextLayoutManager const> mutable textLayoutManager_{};
   std::shared_ptr<void> mutable hostTextStorage_{};
 
+  /* The width Yoga set as maximum width.
+   * Yoga sometimes calls measure twice with two
+   * different maximum width. One if available space.
+   * The other one is exact space needed for the string.
+   * This happens when node is dirtied but its size is not affected.
+   * To deal with this inefficiency, we cache `TextMeasurement` for each
+   * `ParagraphShadowNode`. If Yoga tries to re-measure with available width
+   * or exact width, we provide it with the cached value.
+   */
+  Float mutable availableWidth_{};
+  TextMeasurement mutable cachedTextMeasurement_{};
+
   size_t mutable hash_{};
 };
 } // namespace facebook::react

packages/react-native/ReactCommon/react/renderer/core/CoreFeatures.cpp

@@ -15,6 +15,7 @@ bool CoreFeatures::enableMapBuffer = false;
 bool CoreFeatures::blockPaintForUseLayoutEffect = false;
 bool CoreFeatures::useNativeState = false;
 bool CoreFeatures::cacheNSTextStorage = false;
+bool CoreFeatures::cacheLastTextMeasurement = false;
 
 } // namespace react
 } // namespace facebook

packages/react-native/ReactCommon/react/renderer/core/CoreFeatures.h

@@ -39,6 +39,11 @@ class CoreFeatures {
   // creating it twice. Once when measuring text and once when rendering it.
   // This flag caches it inside ParagraphState.
   static bool cacheNSTextStorage;
+
+  // Yoga might measure multiple times the same Text with the same constraints
+  // This flag enables a caching mechanism to avoid subsequents measurements
+  // of the same Text with the same constrainst.
+  static bool cacheLastTextMeasurement;
 };
 
 } // namespace react

packages/react-native/ReactCommon/react/renderer/textlayoutmanager/platform/android/react/renderer/textlayoutmanager/TextLayoutManager.cpp

@@ -12,6 +12,7 @@
 #include <react/common/mapbuffer/JReadableMapBuffer.h>
 #include <react/jni/ReadableNativeMap.h>
 #include <react/renderer/attributedstring/conversions.h>
+#include <react/renderer/core/CoreFeatures.h>
 #include <react/renderer/core/conversions.h>
 #include <react/renderer/mapbuffer/MapBuffer.h>
 #include <react/renderer/mapbuffer/MapBufferBuilder.h>
@@ -146,7 +147,10 @@ Size measureAndroidComponentMapBuffer(
 TextLayoutManager::TextLayoutManager(
     const ContextContainer::Shared &contextContainer)
     : contextContainer_(contextContainer),
-      measureCache_(kSimpleThreadSafeCacheSizeCap) {}
+      measureCache_(
+          CoreFeatures::cacheLastTextMeasurement
+              ? 8096
+              : kSimpleThreadSafeCacheSizeCap) {}
 
 void *TextLayoutManager::getNativeTextLayoutManager() const {
   return self_;