Add an experimental framesetter cache in ASTextNode2 (#1063)

* Add an experimental framesetter cache in ASTextNode2, and stop keeping framesetters around

* Update configuration schema

* Fix imports

* Fix import again and remove set statement

CHANGELOG.md

@@ -29,6 +29,7 @@
 - Optimize ASDisplayNode -> ASNodeController reference by removing weak proxy and objc associated objects. [Adlai Holler](https://github.com/Adlai-Holler)
 - Remove CA transaction signpost injection because it causes more transactions and is too chatty. [Adlai Holler](https://github.com/Adlai-Holler)
 - Optimize display node accessibility by not creating attributed & non-attributed copies of hint, label, and value. [Adlai Holler](https://github.com/Adlai-Holler)
+- Add an experimental feature that reuses CTFramesetter objects in ASTextNode2 to improve performance. [Adlai Holler](https://github.com/Adlai-Holler)
 
 
 ## 2.7

Schemas/configuration.json

@@ -21,6 +21,7 @@
                     "exp_network_image_queue",
                     "exp_dealloc_queue_v2",
                     "exp_collection_teardown",
+                    "exp_framesetter_cache"
                 ]
     		}
 		}

Source/ASExperimentalFeatures.h

@@ -27,6 +27,7 @@ typedef NS_OPTIONS(NSUInteger, ASExperimentalFeatures) {
   ASExperimentalNetworkImageQueue = 1 << 5,                 // exp_network_image_queue
   ASExperimentalDeallocQueue = 1 << 6,                      // exp_dealloc_queue_v2
   ASExperimentalCollectionTeardown = 1 << 7,                // exp_collection_teardown
+  ASExperimentalFramesetterCache = 1 << 8,                  // exp_framesetter_cache
   ASExperimentalFeatureAll = 0xFFFFFFFF
 };
 

Source/ASExperimentalFeatures.m

@@ -23,7 +23,8 @@ NSArray<NSString *> *ASExperimentalFeaturesGetNames(ASExperimentalFeatures flags
                                       @"exp_infer_layer_defaults",
                                       @"exp_network_image_queue",
                                       @"exp_dealloc_queue_v2",
-                                      @"exp_collection_teardown"]));
+                                      @"exp_collection_teardown",
+                                      @"exp_framesetter_cache"]));
   
   if (flags == ASExperimentalFeatureAll) {
     return allNames;

Source/Private/TextExperiment/Component/ASTextLayout.h

@@ -225,8 +225,6 @@ AS_EXTERN const CGSize ASTextContainerMaxSize;
 @property (nonatomic, readonly) NSAttributedString *text;
 ///< The text range in full text
 @property (nonatomic, readonly) NSRange range;
-///< CTFrameSetter
-@property (nonatomic, readonly) CTFramesetterRef frameSetter;
 ///< CTFrame
 @property (nonatomic, readonly) CTFrameRef frame;
 ///< Array of `ASTextLine`, no truncated

Source/Private/TextExperiment/Component/ASTextLayout.m

@@ -16,11 +16,15 @@
 //
 
 #import <AsyncDisplayKit/ASTextLayout.h>
+
+#import <AsyncDisplayKit/ASConfigurationInternal.h>
 #import <AsyncDisplayKit/ASTextUtilities.h>
 #import <AsyncDisplayKit/ASTextAttribute.h>
 #import <AsyncDisplayKit/NSAttributedString+ASText.h>
 #import <AsyncDisplayKit/ASInternalHelpers.h>
 
+#import <pthread.h>
+
 const CGSize ASTextContainerMaxSize = (CGSize){0x100000, 0x100000};
 
 typedef struct {
@@ -320,7 +324,6 @@ dispatch_semaphore_signal(_lock);
 @property (nonatomic) NSAttributedString *text;
 @property (nonatomic) NSRange range;
 
-@property (nonatomic) CTFramesetterRef frameSetter;
 @property (nonatomic) CTFrameRef frame;
 @property (nonatomic) NSArray *lines;
 @property (nonatomic) ASTextLine *truncatedLine;
@@ -484,10 +487,71 @@ dispatch_semaphore_signal(_lock);
     frameAttrs[(id)kCTFrameProgressionAttributeName] = @(kCTFrameProgressionRightToLeft);
   }
   
-  // create CoreText objects
-  ctSetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)text);
+  /*
+   * Framesetter cache.
+   * Framesetters can only be used by one thread at a time.
+   * Create a CFSet with no callbacks (raw pointers) to keep track of which
+   * framesetters are in use on other threads. If the one for our string is already in use,
+   * just create a new one. This should be pretty rare.
+   */
+  static pthread_mutex_t busyFramesettersLock = PTHREAD_MUTEX_INITIALIZER;
+  static NSCache<NSAttributedString *, id> *framesetterCache;
+  static CFMutableSetRef busyFramesetters;
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    if (ASActivateExperimentalFeature(ASExperimentalFramesetterCache)) {
+      framesetterCache = [[NSCache alloc] init];
+      framesetterCache.name = @"org.TextureGroup.Texture.framesetterCache";
+      busyFramesetters = CFSetCreateMutable(NULL, 0, NULL);
+    }
+  });
+
+  BOOL haveCached = NO, useCached = NO;
+  if (framesetterCache) {
+    // Check if there's one in the cache.
+    ctSetter = (__bridge_retained CTFramesetterRef)[framesetterCache objectForKey:text];
+
+    if (ctSetter) {
+      haveCached = YES;
+
+      // Check-and-set busy on the cached one.
+      pthread_mutex_lock(&busyFramesettersLock);
+      BOOL busy = CFSetContainsValue(busyFramesetters, ctSetter);
+      if (!busy) {
+        CFSetAddValue(busyFramesetters, ctSetter);
+        useCached = YES;
+      }
+      pthread_mutex_unlock(&busyFramesettersLock);
+
+      // Release if it was busy.
+      if (busy) {
+        CFRelease(ctSetter);
+        ctSetter = NULL;
+      }
+    }
+  }
+
+  // Create a framesetter if needed.
+  if (!ctSetter) {
+    ctSetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)text);
+  }
+
   if (!ctSetter) FAIL_AND_RETURN
   ctFrame = CTFramesetterCreateFrame(ctSetter, ASTextCFRangeFromNSRange(range), cgPath, (CFDictionaryRef)frameAttrs);
+
+  // Return to cache.
+  if (framesetterCache) {
+    if (useCached) {
+      // If reused: mark available.
+      pthread_mutex_lock(&busyFramesettersLock);
+      CFSetRemoveValue(busyFramesetters, ctSetter);
+      pthread_mutex_unlock(&busyFramesettersLock);
+    } else if (!haveCached) {
+      // If first framesetter, add to cache.
+      [framesetterCache setObject:(__bridge id)ctSetter forKey:text];
+    }
+  }
+
   if (!ctFrame) FAIL_AND_RETURN
   lines = [NSMutableArray new];
   ctLines = CTFrameGetLines(ctFrame);
@@ -857,8 +921,7 @@ dispatch_semaphore_signal(_lock);
   if (attachments.count == 0) {
     attachments = attachmentRanges = attachmentRects = nil;
   }
-  
-  layout.frameSetter = ctSetter;
+
   layout.frame = ctFrame;
   layout.lines = lines;
   layout.truncatedLine = truncatedLine;
@@ -903,14 +966,6 @@ dispatch_semaphore_signal(_lock);
   return layouts;
 }
 
-- (void)setFrameSetter:(CTFramesetterRef)frameSetter {
-  if (_frameSetter != frameSetter) {
-    if (frameSetter) CFRetain(frameSetter);
-    if (_frameSetter) CFRelease(_frameSetter);
-    _frameSetter = frameSetter;
-  }
-}
-
 - (void)setFrame:(CTFrameRef)frame {
   if (_frame != frame) {
     if (frame) CFRetain(frame);
@@ -920,7 +975,6 @@ dispatch_semaphore_signal(_lock);
 }
 
 - (void)dealloc {
-  if (_frameSetter) CFRelease(_frameSetter);
   if (_frame) CFRelease(_frame);
   if (_lineRowsIndex) free(_lineRowsIndex);
   if (_lineRowsEdge) free(_lineRowsEdge);