[ASDisplayNode] Implement a std::atomic-based flag system for superb performance

Source/ASDisplayNode.h

@@ -217,8 +217,7 @@ extern NSInteger const ASDefaultDrawingPriority;
  *
  * @return NO if the node wraps a _ASDisplayView, YES otherwise.
  */
-@property (nonatomic, readonly, assign, getter=isSynchronous) BOOL synchronous;
-
+@property (atomic, readonly, assign, getter=isSynchronous) BOOL synchronous;
 
 /** @name Getting view and layer */
 

Source/ASDisplayNode.mm

@@ -100,9 +100,9 @@ BOOL ASDisplayNodeSubclassOverridesSelector(Class subclass, SEL selector)
 
 // For classes like ASTableNode, ASCollectionNode, ASScrollNode and similar - we have to be sure to set certain properties
 // like setFrame: and setBackgroundColor: directly to the UIView and not apply it to the layer only.
-BOOL ASDisplayNodeNeedsSpecialPropertiesHandlingForFlags(ASDisplayNodeFlags flags)
+BOOL ASDisplayNodeNeedsSpecialPropertiesHandling(BOOL isSynchronous, BOOL isLayerBacked)
 {
- return flags.synchronous && !flags.layerBacked;
+ return isSynchronous && !isLayerBacked;
 }
 
 _ASPendingState *ASDisplayNodeGetPendingState(ASDisplayNode *node)
@@ -314,7 +314,7 @@ - (instancetype)initWithViewClass:(Class)viewClass
  ASDisplayNodeAssert([viewClass isSubclassOfClass:[UIView class]], @"should initialize with a subclass of UIView");
 
  _viewClass = viewClass;
- _flags.synchronous = ![viewClass isSubclassOfClass:[_ASDisplayView class]];
+ setFlag(Synchronous, ![viewClass isSubclassOfClass:[_ASDisplayView class]]);
 
  return self;
 }
@@ -328,8 +328,8 @@ - (instancetype)initWithLayerClass:(Class)layerClass
  ASDisplayNodeAssert([layerClass isSubclassOfClass:[CALayer class]], @"should initialize with a subclass of CALayer");
 
  _layerClass = layerClass;
- _flags.synchronous = ![layerClass isSubclassOfClass:[_ASDisplayLayer class]];
  _flags.layerBacked = YES;
+ setFlag(Synchronous, ![layerClass isSubclassOfClass:[_ASDisplayLayer class]]);
 
  return self;
 }
@@ -378,7 +378,7 @@ - (void)setViewBlock:(ASDisplayNodeViewBlock)viewBlock
  ASDisplayNodeAssertNotNil(viewBlock, @"should initialize with a valid block that returns a UIView");
 
  _viewBlock = viewBlock;
- _flags.synchronous = YES;
+ setFlag(Synchronous, YES);
 }
 
 - (void)setLayerBlock:(ASDisplayNodeLayerBlock)layerBlock
@@ -387,8 +387,8 @@ - (void)setLayerBlock:(ASDisplayNodeLayerBlock)layerBlock
  ASDisplayNodeAssertNotNil(layerBlock, @"should initialize with a valid block that returns a CALayer");
 
  _layerBlock = layerBlock;
- _flags.synchronous = YES;
  _flags.layerBacked = YES;
+ setFlag(Synchronous, YES);
 }
 
 - (void)onDidLoad:(ASDisplayNodeDidLoadBlock)body
@@ -411,7 +411,7 @@ - (void)dealloc
  _flags.isDeallocating = YES;
 
  // Synchronous nodes may not be able to call the hierarchy notifications, so only enforce for regular nodes.
- ASDisplayNodeAssert(_flags.synchronous || !ASInterfaceStateIncludesVisible(_interfaceState), @"Node should always be marked invisible before deallocating. Node: %@", self);
+ ASDisplayNodeAssert(checkFlag(Synchronous) || !ASInterfaceStateIncludesVisible(_interfaceState), @"Node should always be marked invisible before deallocating. Node: %@", self);
 
  self.asyncLayer.asyncDelegate = nil;
  _view.asyncdisplaykit_node = nil;
@@ -547,7 +547,7 @@ - (void)__unloadNode
 {
  ASDisplayNodeAssertMainThread();
  ASDisplayNodeAssert([self isNodeLoaded], @"Implementation shouldn't call __unloadNode if not loaded: %@", self);
- ASDisplayNodeAssert(_flags.synchronous == NO, @"Node created using -initWithViewBlock:/-initWithLayerBlock: cannot be unloaded. Node: %@", self);
+ ASDisplayNodeAssert(checkFlag(Synchronous) == NO, @"Node created using -initWithViewBlock:/-initWithLayerBlock: cannot be unloaded. Node: %@", self);
  ASDN::MutexLocker l(__instanceLock__);
 
  if (_flags.layerBacked) {
@@ -583,7 +583,7 @@ - (UIView *)_locked_viewToLoad
  }
 
  // Special handling of wrapping UIKit components
- if (_flags.synchronous) {
+ if (checkFlag(Synchronous)) {
  // UIImageView layers. More details on the flags
  if ([_viewClass isSubclassOfClass:[UIImageView class]]) {
  _flags.canClearContentsOfLayer = NO;
@@ -805,8 +805,7 @@ - (_ASDisplayLayer *)_locked_asyncLayer
 
 - (BOOL)isSynchronous
 {
- ASDN::MutexLocker l(__instanceLock__);
- return _flags.synchronous;
+ return checkFlag(Synchronous);
 }
 
 - (void)setLayerBacked:(BOOL)isLayerBacked
@@ -836,7 +835,7 @@ - (BOOL)isLayerBacked
 - (BOOL)supportsLayerBacking
 {
  ASDN::MutexLocker l(__instanceLock__);
- return !_flags.synchronous && !_flags.viewEverHadAGestureRecognizerAttached && _viewClass == [_ASDisplayView class] && _layerClass == [_ASDisplayLayer class];
+ return !checkFlag(Synchronous) && !_flags.viewEverHadAGestureRecognizerAttached && _viewClass == [_ASDisplayView class] && _layerClass == [_ASDisplayLayer class];
 }
 
 - (BOOL)shouldAnimateSizeChanges
@@ -1948,7 +1947,7 @@ - (BOOL)displaysAsynchronously
  */
 - (BOOL)_locked_displaysAsynchronously
 {
- return _flags.synchronous == NO && _flags.displaysAsynchronously;
+ return checkFlag(Synchronous) == NO && _flags.displaysAsynchronously;
 }
 
 - (void)setDisplaysAsynchronously:(BOOL)displaysAsynchronously
@@ -1958,7 +1957,7 @@ - (void)setDisplaysAsynchronously:(BOOL)displaysAsynchronously
  ASDN::MutexLocker l(__instanceLock__);
 
  // Can't do this for synchronous nodes (using layers that are not _ASDisplayLayer and so we can't control display prevention/cancel)
- if (_flags.synchronous) {
+ if (checkFlag(Synchronous)) {
  return;
  }
 
@@ -2052,7 +2051,7 @@ - (void)setContentsScaleForDisplay:(CGFloat)contentsScaleForDisplay
 - (void)displayImmediately
 {
  ASDisplayNodeAssertMainThread();
- ASDisplayNodeAssert(!_flags.synchronous, @"this method is designed for asynchronous mode only");
+ ASDisplayNodeAssert(!checkFlag(Synchronous), @"this method is designed for asynchronous mode only");
 
  [self.asyncLayer displayImmediately];
 }
@@ -2073,7 +2072,7 @@ - (void)__setNeedsDisplay
  BOOL nowDisplay = ASInterfaceStateIncludesDisplay(_interfaceState);
  // FIXME: This should not need to recursively display, so create a non-recursive variant.
  // The semantics of setNeedsDisplay (as defined by CALayer behavior) are not recursive.
- if (_layer != nil && !_flags.synchronous && nowDisplay && [self _implementsDisplay]) {
+ if (_layer != nil && !checkFlag(Synchronous) && nowDisplay && [self _implementsDisplay]) {
  shouldScheduleForDisplay = YES;
  }
  }
@@ -2317,7 +2316,7 @@ - (void)setDisplaySuspended:(BOOL)flag
  __instanceLock__.lock();
 
  // Can't do this for synchronous nodes (using layers that are not _ASDisplayLayer and so we can't control display prevention/cancel)
- if (_flags.synchronous || _flags.displaySuspended == flag) {
+ if (checkFlag(Synchronous) || _flags.displaySuspended == flag) {
  __instanceLock__.unlock();
  return;
  }
@@ -3406,7 +3405,7 @@ - (void)setHierarchyState:(ASHierarchyState)newState
 
  // Entered rasterization state.
  if (newState & ASHierarchyStateRasterized) {
- ASDisplayNodeAssert(_flags.synchronous == NO, @"Node created using -initWithViewBlock:/-initWithLayerBlock: cannot be added to subtree of node with shouldRasterizeDescendants=YES. Node: %@", self);
+ ASDisplayNodeAssert(checkFlag(Synchronous) == NO, @"Node created using -initWithViewBlock:/-initWithLayerBlock: cannot be added to subtree of node with shouldRasterizeDescendants=YES. Node: %@", self);
  }
 
  // Entered or exited range managed state.
@@ -3907,7 +3906,7 @@ - (void)_locked_applyPendingViewState
  if (_flags.layerBacked) {
  [_pendingViewState applyToLayer:self.layer];
  } else {
- BOOL specialPropertiesHandling = ASDisplayNodeNeedsSpecialPropertiesHandlingForFlags(_flags);
+ BOOL specialPropertiesHandling = ASDisplayNodeNeedsSpecialPropertiesHandling(checkFlag(Synchronous), _flags.layerBacked);
  [_pendingViewState applyToView:self.view withSpecialPropertiesHandling:specialPropertiesHandling];
  }
 

Source/Private/ASDisplayNode+UIViewBridge.mm

@@ -241,7 +241,7 @@ - (void)setFrame:(CGRect)rect
 
  // For classes like ASTableNode, ASCollectionNode, ASScrollNode and similar - make sure UIView gets setFrame:
  struct ASDisplayNodeFlags flags = _flags;
- BOOL specialPropertiesHandling = ASDisplayNodeNeedsSpecialPropertiesHandlingForFlags(flags);
+ BOOL specialPropertiesHandling = ASDisplayNodeNeedsSpecialPropertiesHandling(checkFlag(Synchronous), flags.layerBacked);
 
  BOOL nodeLoaded = __loaded(self);
  BOOL isMainThread = ASDisplayNodeThreadIsMain();
@@ -635,7 +635,7 @@ - (void)setBackgroundColor:(UIColor *)newBackgroundColor
  if (shouldApply) {
  CGColorRef oldBackgroundCGColor = _layer.backgroundColor;
 
- BOOL specialPropertiesHandling = ASDisplayNodeNeedsSpecialPropertiesHandlingForFlags(_flags);
+ BOOL specialPropertiesHandling = ASDisplayNodeNeedsSpecialPropertiesHandling(checkFlag(Synchronous), _flags.layerBacked);
  if (specialPropertiesHandling) {
  _view.backgroundColor = newBackgroundColor;
  } else {

Source/Private/ASDisplayNodeInternal.h

@@ -38,7 +38,7 @@ NS_ASSUME_NONNULL_BEGIN
 struct ASDisplayNodeFlags;
 
 BOOL ASDisplayNodeSubclassOverridesSelector(Class subclass, SEL selector);
-BOOL ASDisplayNodeNeedsSpecialPropertiesHandlingForFlags(ASDisplayNodeFlags flags);
+BOOL ASDisplayNodeNeedsSpecialPropertiesHandling(BOOL isSynchronous, BOOL isLayerBacked);
 
 /// Get the pending view state for the node, creating one if needed.
 _ASPendingState * ASDisplayNodeGetPendingState(ASDisplayNode * node);
@@ -55,6 +55,16 @@ typedef NS_OPTIONS(NSUInteger, ASDisplayNodeMethodOverrides)
  ASDisplayNodeMethodOverrideClearFetchedData = 1 << 6
 };
 
+typedef NS_OPTIONS(uint_least32_t, ASDisplayNodeAtomicFlags)
+{
+ Synchronous = 1 << 0,
+};
+
+#define checkFlag(flag) ((_atomicFlags.load() & flag) != 0)
+// Returns the old value of the flag as a BOOL.
+#define setFlag(flag, x) (((x ? _atomicFlags.fetch_or(flag) \
+ : _atomicFlags.fetch_and(~flag)) & flag) != 0)
+
 FOUNDATION_EXPORT NSString * const ASRenderingEngineDidDisplayScheduledNodesNotification;
 FOUNDATION_EXPORT NSString * const ASRenderingEngineDidDisplayNodesScheduledBeforeTimestamp;
 
@@ -71,9 +81,10 @@ FOUNDATION_EXPORT NSString * const ASRenderingEngineDidDisplayNodesScheduledBefo
  UIView *_view;
  CALayer *_layer;
 
+ std::atomic<ASDisplayNodeAtomicFlags> _atomicFlags;
+
  struct ASDisplayNodeFlags {
  // public properties
- unsigned synchronous:1;
  unsigned viewEverHadAGestureRecognizerAttached:1;
  unsigned layerBacked:1;
  unsigned displaysAsynchronously:1;