Fabric: Caching for `NSAttributedString`s in RCTTextLayoutManager

Summary:
Creation NSAttributedString from attributedString is not so cheap process, so with this simple cache we hopefully can save a couple milliseconds.
The same string is used at least two times: first time for measuring and second for drawing.

Reviewed By: mdvacca

Differential Revision: D14296514

fbshipit-source-id: 6313aa2c6e9f63d873868131750f61c02d64d2de

ReactCommon/fabric/textlayoutmanager/platform/ios/RCTTextLayoutManager.mm

@@ -10,9 +10,13 @@
 #import "NSTextStorage+FontScaling.h"
 #import "RCTAttributedTextUtils.h"
 
+#import <react/utils/SimpleThreadSafeCache.h>
+
 using namespace facebook::react;
 
-@implementation RCTTextLayoutManager
+@implementation RCTTextLayoutManager {
+  SimpleThreadSafeCache<AttributedString, std::shared_ptr<const void>, 256> _cache;
+}
 
 static NSLineBreakMode RCTNSLineBreakModeFromWritingDirection(
     EllipsizeMode ellipsizeMode) {
@@ -34,11 +38,10 @@ static NSLineBreakMode RCTNSLineBreakModeFromWritingDirection(
               layoutConstraints:(LayoutConstraints)layoutConstraints {
   CGSize maximumSize = CGSize{layoutConstraints.maximumSize.width,
                               layoutConstraints.maximumSize.height};
-  NSTextStorage *textStorage =
-      [self _textStorageAndLayoutManagerWithAttributesString:
-                RCTNSAttributedStringFromAttributedString(attributedString)
-                                         paragraphAttributes:paragraphAttributes
-                                                        size:maximumSize];
+  NSTextStorage *textStorage = [self
+      _textStorageAndLayoutManagerWithAttributesString:[self _nsAttributedStringFromAttributedString:attributedString]
+                                   paragraphAttributes:paragraphAttributes
+                                                  size:maximumSize];
 
   NSLayoutManager *layoutManager = textStorage.layoutManagers.firstObject;
   NSTextContainer *textContainer = layoutManager.textContainers.firstObject;
@@ -55,11 +58,10 @@ static NSLineBreakMode RCTNSLineBreakModeFromWritingDirection(
 - (void)drawAttributedString:(AttributedString)attributedString
          paragraphAttributes:(ParagraphAttributes)paragraphAttributes
                        frame:(CGRect)frame {
-  NSTextStorage *textStorage =
-      [self _textStorageAndLayoutManagerWithAttributesString:
-                RCTNSAttributedStringFromAttributedString(attributedString)
-                                         paragraphAttributes:paragraphAttributes
-                                                        size:frame.size];
+  NSTextStorage *textStorage = [self
+      _textStorageAndLayoutManagerWithAttributesString:[self _nsAttributedStringFromAttributedString:attributedString]
+                                   paragraphAttributes:paragraphAttributes
+                                                  size:frame.size];
   NSLayoutManager *layoutManager = textStorage.layoutManagers.firstObject;
   NSTextContainer *textContainer = layoutManager.textContainers.firstObject;
 
@@ -111,11 +113,10 @@ static NSLineBreakMode RCTNSLineBreakModeFromWritingDirection(
                    paragraphAttributes:(ParagraphAttributes)paragraphAttributes
                                  frame:(CGRect)frame
                                atPoint:(CGPoint)point {
-  NSTextStorage *textStorage =
-      [self _textStorageAndLayoutManagerWithAttributesString:
-                RCTNSAttributedStringFromAttributedString(attributedString)
-                                         paragraphAttributes:paragraphAttributes
-                                                        size:frame.size];
+  NSTextStorage *textStorage = [self
+      _textStorageAndLayoutManagerWithAttributesString:[self _nsAttributedStringFromAttributedString:attributedString]
+                                   paragraphAttributes:paragraphAttributes
+                                                  size:frame.size];
   NSLayoutManager *layoutManager = textStorage.layoutManagers.firstObject;
   NSTextContainer *textContainer = layoutManager.textContainers.firstObject;
 
@@ -140,4 +141,14 @@ static NSLineBreakMode RCTNSLineBreakModeFromWritingDirection(
   return nil;
 }
 
+- (NSAttributedString *)_nsAttributedStringFromAttributedString:(AttributedString)attributedString
+{
+  auto sharedNSAttributedString = _cache.get(attributedString, [](const AttributedString attributedString) {
+    return std::shared_ptr<void>(
+        (__bridge_retained void *)RCTNSAttributedStringFromAttributedString(attributedString), CFRelease);
+  });
+
+  return (__bridge NSAttributedString *)sharedNSAttributedString.get();
+}
+
 @end