Avoid copying AttributedString on the iOS text measure path

iOS text measurement deep-copied the AttributedString several times per
measure, even on a cache hit. Bind references where the code only reads,
move dying locals into the box, add an AttributedString&& box constructor,
build the empty-string placeholder only when needed, and take
const AttributedString& in the RCTTextLayoutManager methods.

Author: dheerajkoppu

packages/react-native/React/Fabric/Mounting/ComponentViews/Text/RCTParagraphComponentView.mm

@@ -27,7 +27,7 @@
 
 @interface RCTTextLayoutManager (RCTParagraphComponentViewPrivate)
 
-- (CGRect)drawingFrameForAttributedString:(facebook::react::AttributedString)attributedString
+- (CGRect)drawingFrameForAttributedString:(const facebook::react::AttributedString &)attributedString
                       paragraphAttributes:(facebook::react::ParagraphAttributes)paragraphAttributes
                                     frame:(CGRect)frame
                            containerFrame:(CGRect *)containerFrame;

packages/react-native/ReactCommon/react/renderer/attributedstring/AttributedStringBox.cpp

@@ -23,6 +23,11 @@ AttributedStringBox::AttributedStringBox(const AttributedString& value)
       value_(std::make_shared<const AttributedString>(value)),
       opaquePointer_({}) {};
 
+AttributedStringBox::AttributedStringBox(AttributedString&& value)
+    : mode_(Mode::Value),
+      value_(std::make_shared<const AttributedString>(std::move(value))),
+      opaquePointer_({}) {};
+
 AttributedStringBox::AttributedStringBox(std::shared_ptr<void> opaquePointer)
     : mode_(Mode::OpaquePointer),
       value_({}),

packages/react-native/ReactCommon/react/renderer/attributedstring/AttributedStringBox.h

@@ -37,6 +37,7 @@ class AttributedStringBox final {
    * Custom explicit constructors.
    */
   explicit AttributedStringBox(const AttributedString &value);
+  explicit AttributedStringBox(AttributedString &&value);
   explicit AttributedStringBox(std::shared_ptr<void> opaquePointer);
 
   /*

packages/react-native/ReactCommon/react/renderer/attributedstring/tests/AttributedStringBoxTest.cpp

@@ -30,6 +30,18 @@ TEST(AttributedStringBoxTest, testValueConstructor) {
   EXPECT_EQ(attributedStringBox.getValue(), attributedString);
 }
 
+TEST(AttributedStringBoxTest, testValueMoveConstructor) {
+  auto attributedString = AttributedString{};
+  auto fragment = AttributedString::Fragment{};
+  fragment.string = "test string";
+  attributedString.appendFragment(std::move(fragment));
+  auto expectedAttributedString = attributedString;
+  auto attributedStringBox = AttributedStringBox{std::move(attributedString)};
+
+  EXPECT_EQ(attributedStringBox.getMode(), AttributedStringBox::Mode::Value);
+  EXPECT_EQ(attributedStringBox.getValue(), expectedAttributedString);
+}
+
 TEST(AttributedStringBoxTest, testOpaquePointerConstructor) {
   auto string = std::make_shared<std::string>("test string");
   auto attributedStringBox = AttributedStringBox{string};

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

@@ -88,7 +88,9 @@ const Content& ParagraphShadowNode::getContent(
   attributedString.setBaseTextAttributes(textAttributes);
 
   content_ = Content{
-      attributedString, getConcreteProps().paragraphAttributes, attachments};
+      std::move(attributedString),
+      getConcreteProps().paragraphAttributes,
+      std::move(attachments)};
 
   return content_.value();
 }
@@ -264,7 +266,7 @@ Size ParagraphShadowNode::measureContent(
 
   auto size = textLayoutManager_
                   ->measure(
-                      AttributedStringBox{content.attributedString},
+                      AttributedStringBox{std::move(content.attributedString)},
                       content.paragraphAttributes,
                       textLayoutContext,
                       layoutConstraints)
@@ -282,7 +284,7 @@ Float ParagraphShadowNode::baseline(
   auto content =
       getContentWithMeasuredAttachments(layoutContext, layoutConstraints);
 
-  AttributedStringBox attributedStringBox{content.attributedString};
+  AttributedStringBox attributedStringBox{std::move(content.attributedString)};
 
   if constexpr (TextLayoutManagerExtended::supportsLineMeasurement()) {
     auto lines =
@@ -346,7 +348,9 @@ void ParagraphShadowNode::layout(LayoutContext layoutContext) {
       .pointScaleFactor = layoutContext.pointScaleFactor,
       .surfaceId = getSurfaceId(),
   };
-  AttributedStringBox attributedStringBox{content.attributedString};
+  // The state update above already captured the attributed string and
+  // nothing below reads it, so the box can take it instead of copying it.
+  AttributedStringBox attributedStringBox{std::move(content.attributedString)};
 
   if (getConcreteProps().onTextLayout) {
     if constexpr (TextLayoutManagerExtended::supportsLineMeasurement()) {

packages/react-native/ReactCommon/react/renderer/textlayoutmanager/platform/ios/react/renderer/textlayoutmanager/RCTTextLayoutManager.h

@@ -29,7 +29,7 @@ using RCTTextLayoutFragmentEnumerationBlock =
  */
 @interface RCTTextLayoutManager : NSObject
 
-- (facebook::react::TextMeasurement)measureAttributedString:(facebook::react::AttributedString)attributedString
+- (facebook::react::TextMeasurement)measureAttributedString:(const facebook::react::AttributedString &)attributedString
                                         paragraphAttributes:(facebook::react::ParagraphAttributes)paragraphAttributes
                                               layoutContext:(facebook::react::TextLayoutContext)layoutContext
                                           layoutConstraints:(facebook::react::LayoutConstraints)layoutConstraints;
@@ -39,23 +39,23 @@ using RCTTextLayoutFragmentEnumerationBlock =
                                                 layoutContext:(facebook::react::TextLayoutContext)layoutContext
                                             layoutConstraints:(facebook::react::LayoutConstraints)layoutConstraints;
 
-- (void)drawAttributedString:(facebook::react::AttributedString)attributedString
+- (void)drawAttributedString:(const facebook::react::AttributedString &)attributedString
          paragraphAttributes:(facebook::react::ParagraphAttributes)paragraphAttributes
                        frame:(CGRect)frame
            drawHighlightPath:(void (^_Nullable)(UIBezierPath *highlightPath))block;
 
-- (facebook::react::LinesMeasurements)getLinesForAttributedString:(facebook::react::AttributedString)attributedString
-                                              paragraphAttributes:
-                                                  (facebook::react::ParagraphAttributes)paragraphAttributes
-                                                             size:(CGSize)size;
+- (facebook::react::LinesMeasurements)
+    getLinesForAttributedString:(const facebook::react::AttributedString &)attributedString
+            paragraphAttributes:(facebook::react::ParagraphAttributes)paragraphAttributes
+                           size:(CGSize)size;
 
 - (std::shared_ptr<const facebook::react::EventEmitter>)
-    getEventEmitterWithAttributeString:(facebook::react::AttributedString)attributedString
+    getEventEmitterWithAttributeString:(const facebook::react::AttributedString &)attributedString
                    paragraphAttributes:(facebook::react::ParagraphAttributes)paragraphAttributes
                                  frame:(CGRect)frame
                                atPoint:(CGPoint)point;
 
-- (void)getRectWithAttributedString:(facebook::react::AttributedString)attributedString
+- (void)getRectWithAttributedString:(const facebook::react::AttributedString &)attributedString
                 paragraphAttributes:(facebook::react::ParagraphAttributes)paragraphAttributes
                  enumerateAttribute:(NSString *)enumerateAttribute
                               frame:(CGRect)frame

packages/react-native/ReactCommon/react/renderer/textlayoutmanager/platform/ios/react/renderer/textlayoutmanager/RCTTextLayoutManager.mm

@@ -59,7 +59,7 @@ - (TextMeasurement)measureNSAttributedString:(NSAttributedString *)attributedStr
   return [self _measureTextStorage:textStorage paragraphAttributes:paragraphAttributes layoutContext:layoutContext];
 }
 
-- (TextMeasurement)measureAttributedString:(AttributedString)attributedString
+- (TextMeasurement)measureAttributedString:(const AttributedString &)attributedString
                        paragraphAttributes:(ParagraphAttributes)paragraphAttributes
                              layoutContext:(TextLayoutContext)layoutContext
                          layoutConstraints:(LayoutConstraints)layoutConstraints
@@ -70,7 +70,7 @@ - (TextMeasurement)measureAttributedString:(AttributedString)attributedString
                        layoutConstraints:layoutConstraints];
 }
 
-- (CGRect)drawingFrameForAttributedString:(AttributedString)attributedString
+- (CGRect)drawingFrameForAttributedString:(const AttributedString &)attributedString
                       paragraphAttributes:(ParagraphAttributes)paragraphAttributes
                                     frame:(CGRect)frame
                            containerFrame:(CGRect *)containerFrame
@@ -128,7 +128,7 @@ - (CGRect)drawingFrameForAttributedString:(AttributedString)attributedString
   return drawingFrame;
 }
 
-- (void)drawAttributedString:(AttributedString)attributedString
+- (void)drawAttributedString:(const AttributedString &)attributedString
          paragraphAttributes:(ParagraphAttributes)paragraphAttributes
                        frame:(CGRect)frame
            drawHighlightPath:(void (^_Nullable)(UIBezierPath *highlightPath))block
@@ -363,7 +363,7 @@ - (void)processTruncatedAttributedText:(NSTextStorage *)textStorage
   }
 }
 
-- (LinesMeasurements)getLinesForAttributedString:(facebook::react::AttributedString)attributedString
+- (LinesMeasurements)getLinesForAttributedString:(const facebook::react::AttributedString &)attributedString
                              paragraphAttributes:(facebook::react::ParagraphAttributes)paragraphAttributes
                                             size:(CGSize)size
 {
@@ -467,7 +467,7 @@ - (NSTextStorage *)_textStorageAndLayoutManagerWithAttributesString:(NSAttribute
   return textStorage;
 }
 
-- (std::shared_ptr<const EventEmitter>)getEventEmitterWithAttributeString:(AttributedString)attributedString
+- (std::shared_ptr<const EventEmitter>)getEventEmitterWithAttributeString:(const AttributedString &)attributedString
                                                       paragraphAttributes:(ParagraphAttributes)paragraphAttributes
                                                                     frame:(CGRect)frame
                                                                   atPoint:(CGPoint)point
@@ -497,7 +497,7 @@ - (NSTextStorage *)_textStorageAndLayoutManagerWithAttributesString:(NSAttribute
   return nil;
 }
 
-- (void)getRectWithAttributedString:(AttributedString)attributedString
+- (void)getRectWithAttributedString:(const AttributedString &)attributedString
                 paragraphAttributes:(ParagraphAttributes)paragraphAttributes
                  enumerateAttribute:(NSString *)enumerateAttribute
                               frame:(CGRect)frame
@@ -539,7 +539,7 @@ - (void)getRectWithAttributedString:(AttributedString)attributedString
 
 #pragma mark - Private
 
-- (NSAttributedString *)_nsAttributedStringFromAttributedString:(AttributedString)attributedString
+- (NSAttributedString *)_nsAttributedStringFromAttributedString:(const AttributedString &)attributedString
 {
   auto sharedNSAttributedString = _cache.get(attributedString, [&]() {
     return wrapManagedObject(RCTNSAttributedStringFromAttributedString(attributedString));

packages/react-native/ReactCommon/react/renderer/textlayoutmanager/platform/ios/react/renderer/textlayoutmanager/TextLayoutManager.mm

@@ -8,12 +8,23 @@
 #import "TextLayoutManager.h"
 #import "RCTTextLayoutManager.h"
 
+#import <optional>
+
 #import <react/renderer/attributedstring/PlaceholderAttributedString.h>
 #import <react/renderer/telemetry/TransactionTelemetry.h>
 #import <react/utils/ManagedObjectWrapper.h>
 
 namespace facebook::react {
 
+// `ensurePlaceholderIfEmpty_DO_NOT_USE` returns a copy, so only call it for an empty string that needs one.
+static std::optional<AttributedString> placeholderIfEmpty(const AttributedString &attributedString)
+{
+  if (attributedString.isEmpty()) {
+    return ensurePlaceholderIfEmpty_DO_NOT_USE(attributedString);
+  }
+  return std::nullopt;
+}
+
 TextLayoutManager::TextLayoutManager(const std::shared_ptr<const ContextContainer> & /*contextContainer*/)
 {
   nativeTextLayoutManager_ = wrapManagedObject([RCTTextLayoutManager new]);
@@ -37,8 +48,10 @@
 
   switch (attributedStringBox.getMode()) {
     case AttributedStringBox::Mode::Value: {
-      auto originalAtributedString = attributedStringBox.getValue();
-      auto attributedString = ensurePlaceholderIfEmpty_DO_NOT_USE(originalAtributedString);
+      const auto &originalAttributedString = attributedStringBox.getValue();
+      auto placeholderAttributedString = placeholderIfEmpty(originalAttributedString);
+      const auto &attributedString =
+          placeholderAttributedString ? *placeholderAttributedString : originalAttributedString;
 
       measurement = textMeasureCache_.get(
           {.attributedString = attributedString,
@@ -60,7 +73,7 @@
             // being used to represent empty string. iOS TextLayoutManager
             // should instead measure using `baseTextAttributes` of the
             // `AttributedString`.
-            if (originalAtributedString.isEmpty()) {
+            if (originalAttributedString.isEmpty()) {
               measurement.size.width = 0;
             }
 
@@ -106,7 +119,9 @@
     const Size &size) const
 {
   react_native_assert(attributedStringBox.getMode() == AttributedStringBox::Mode::Value);
-  auto attributedString = ensurePlaceholderIfEmpty_DO_NOT_USE(attributedStringBox.getValue());
+  const auto &originalAttributedString = attributedStringBox.getValue();
+  auto placeholderAttributedString = placeholderIfEmpty(originalAttributedString);
+  const auto &attributedString = placeholderAttributedString ? *placeholderAttributedString : originalAttributedString;
 
   RCTTextLayoutManager *textLayoutManager = (RCTTextLayoutManager *)unwrapManagedObject(nativeTextLayoutManager_);
 

scripts/cxx-api/api-snapshots/ReactAndroidFrameworksCxx.api

@@ -1366,6 +1366,7 @@ class facebook::react::AttributedStringBox {
   public AttributedStringBox();
   public AttributedStringBox(const facebook::react::AttributedString& value);
   public AttributedStringBox(const facebook::react::AttributedStringBox& other) = default;
+  public AttributedStringBox(facebook::react::AttributedString&& value);
   public AttributedStringBox(facebook::react::AttributedStringBox&& other) noexcept;
   public AttributedStringBox(std::shared_ptr<void> opaquePointer);
   public const facebook::react::AttributedString& getValue() const;

scripts/cxx-api/api-snapshots/ReactAppleFrameworksCxx.api

@@ -1939,12 +1939,12 @@ interface RCTTextInputComponentView : public RCTViewComponentView {
 }
 
 interface RCTTextLayoutManager : public NSObject {
-  public virtual facebook::react::LinesMeasurements getLinesForAttributedString:paragraphAttributes:size:(facebook::react::AttributedString attributedString, facebook::react::ParagraphAttributes paragraphAttributes, CGSize size);
-  public virtual facebook::react::TextMeasurement measureAttributedString:paragraphAttributes:layoutContext:layoutConstraints:(facebook::react::AttributedString attributedString, facebook::react::ParagraphAttributes paragraphAttributes, facebook::react::TextLayoutContext layoutContext, facebook::react::LayoutConstraints layoutConstraints);
+  public virtual facebook::react::LinesMeasurements getLinesForAttributedString:paragraphAttributes:size:(const facebook::react::AttributedString& attributedString, facebook::react::ParagraphAttributes paragraphAttributes, CGSize size);
+  public virtual facebook::react::TextMeasurement measureAttributedString:paragraphAttributes:layoutContext:layoutConstraints:(const facebook::react::AttributedString& attributedString, facebook::react::ParagraphAttributes paragraphAttributes, facebook::react::TextLayoutContext layoutContext, facebook::react::LayoutConstraints layoutConstraints);
   public virtual facebook::react::TextMeasurement measureNSAttributedString:paragraphAttributes:layoutContext:layoutConstraints:(NSAttributedString* attributedString, facebook::react::ParagraphAttributes paragraphAttributes, facebook::react::TextLayoutContext layoutContext, facebook::react::LayoutConstraints layoutConstraints);
-  public virtual std::shared_ptr<const facebook::react::EventEmitter> getEventEmitterWithAttributeString:paragraphAttributes:frame:atPoint:(facebook::react::AttributedString attributedString, facebook::react::ParagraphAttributes paragraphAttributes, CGRect frame, CGPoint point);
-  public virtual void drawAttributedString:paragraphAttributes:frame:drawHighlightPath:(facebook::react::AttributedString attributedString, facebook::react::ParagraphAttributes paragraphAttributes, CGRect frame, void(^)(UIBezierPath* highlightPath) block);
-  public virtual void getRectWithAttributedString:paragraphAttributes:enumerateAttribute:frame:usingBlock:(facebook::react::AttributedString attributedString, facebook::react::ParagraphAttributes paragraphAttributes, NSString* enumerateAttribute, CGRect frame, RCTTextLayoutFragmentEnumerationBlock block);
+  public virtual std::shared_ptr<const facebook::react::EventEmitter> getEventEmitterWithAttributeString:paragraphAttributes:frame:atPoint:(const facebook::react::AttributedString& attributedString, facebook::react::ParagraphAttributes paragraphAttributes, CGRect frame, CGPoint point);
+  public virtual void drawAttributedString:paragraphAttributes:frame:drawHighlightPath:(const facebook::react::AttributedString& attributedString, facebook::react::ParagraphAttributes paragraphAttributes, CGRect frame, void(^)(UIBezierPath* highlightPath) block);
+  public virtual void getRectWithAttributedString:paragraphAttributes:enumerateAttribute:frame:usingBlock:(const facebook::react::AttributedString& attributedString, facebook::react::ParagraphAttributes paragraphAttributes, NSString* enumerateAttribute, CGRect frame, RCTTextLayoutFragmentEnumerationBlock block);
 }
 
 interface RCTTextSelection : public NSObject {
@@ -3963,6 +3963,7 @@ class facebook::react::AttributedStringBox {
   public AttributedStringBox();
   public AttributedStringBox(const facebook::react::AttributedString& value);
   public AttributedStringBox(const facebook::react::AttributedStringBox& other) = default;
+  public AttributedStringBox(facebook::react::AttributedString&& value);
   public AttributedStringBox(facebook::react::AttributedStringBox&& other) noexcept;
   public AttributedStringBox(std::shared_ptr<void> opaquePointer);
   public const facebook::react::AttributedString& getValue() const;