Several bug fixes for the 1.0 release of AsyncDisplayKit

Fixes:
- Usage of UIScreen in -[ASDisplayNode init]
  (the offending individual will be prosecuted)
- #38: Proper teardown of nodes owned by ASTableView / ASRangeController
- #34: Fix infinite recursion in very rare subclassing scenario
- #30: Avoid animating cell and section additions to ASTableView
- #19: Set a more reasonable default for maximum display concurrency

r=nadi

AsyncDisplayKit/ASDisplayNode.mm

@@ -47,6 +47,22 @@ BOOL ASDisplayNodeSubclassOverridesSelector(Class subclass, SEL selector)
   return (superclassIMP != subclassIMP);
 }
 
+CGFloat ASDisplayNodeScreenScale()
+{
+  static CGFloat screenScale = 0.0;
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    if ([NSThread isMainThread]) {
+      screenScale = [[UIScreen mainScreen] scale];
+    } else {
+      dispatch_sync(dispatch_get_main_queue(), ^{
+        screenScale = [[UIScreen mainScreen] scale];
+      });
+    }
+  });
+  return screenScale;
+}
+
 + (void)initialize
 {
   if (self == [ASDisplayNode class]) {
@@ -74,14 +90,44 @@ BOOL ASDisplayNodeSubclassOverridesSelector(Class subclass, SEL selector)
   return [_ASDisplayLayer class];
 }
 
-#pragma mark - NSObject Overrides
+#pragma mark - Lifecycle
+
+// Avoid recursive loops if a subclass implements an init method that calls -initWith*Class:
+- (void)_initializeInstance
+{
+  _contentsScaleForDisplay = ASDisplayNodeScreenScale();
+  
+  _displaySentinel = [[ASSentinel alloc] init];
+  
+  _flags.inWindow = NO;
+  _flags.displaysAsynchronously = YES;
+  
+  // As an optimization, it may be worth a caching system that performs these checks once per class in +initialize (see above).
+  _flags.implementsDisplay = [[self class] respondsToSelector:@selector(drawRect:withParameters:isCancelled:isRasterizing:)] || [self.class respondsToSelector:@selector(displayWithParameters:isCancelled:)];
+  
+  _flags.hasClassDisplay = ([[self class] respondsToSelector:@selector(displayWithParameters:isCancelled:)] ? 1 : 0);
+  _flags.hasWillDisplayAsyncLayer = ([self respondsToSelector:@selector(willDisplayAsyncLayer:)] ? 1 : 0);
+  _flags.hasDrawParametersForAsyncLayer = ([self respondsToSelector:@selector(drawParametersForAsyncLayer:)] ? 1 : 0);
+}
+
+- (id)init
+{
+  if (!(self = [super init]))
+    return nil;
+  
+  [self _initializeInstance];
+  
+  return self;
+}
 
 - (id)initWithViewClass:(Class)viewClass
 {
-  if (!(self = [self init]))
+  if (!(self = [super init]))
     return nil;
 
   ASDisplayNodeAssert([viewClass isSubclassOfClass:[UIView class]], @"should initialize with a subclass of UIView");
+  
+  [self _initializeInstance];
   _viewClass = viewClass;
   _flags.isSynchronous = ![viewClass isSubclassOfClass:[_ASDisplayView class]];
 
@@ -90,40 +136,19 @@ BOOL ASDisplayNodeSubclassOverridesSelector(Class subclass, SEL selector)
 
 - (id)initWithLayerClass:(Class)layerClass
 {
-  if (!(self = [self init]))
+  if (!(self = [super init]))
     return nil;
-
+  
   ASDisplayNodeAssert([layerClass isSubclassOfClass:[CALayer class]], @"should initialize with a subclass of CALayer");
 
+  [self _initializeInstance];
   _layerClass = layerClass;
   _flags.isSynchronous = ![layerClass isSubclassOfClass:[_ASDisplayLayer class]];
-
   _flags.isLayerBacked = YES;
 
   return self;
 }
 
-- (id)init
-{
-  self = [super init];
-  if (!self) return nil;
-
-  _contentsScaleForDisplay = [[UIScreen mainScreen] scale];
-
-  _displaySentinel = [[ASSentinel alloc] init];
-
-  _flags.inWindow = NO;
-  _flags.displaysAsynchronously = YES;
-
-  _flags.implementsDisplay = [[self class] respondsToSelector:@selector(drawRect:withParameters:isCancelled:isRasterizing:)] || [self.class respondsToSelector:@selector(displayWithParameters:isCancelled:)];
-
-  _flags.hasWillDisplayAsyncLayer = ([self respondsToSelector:@selector(willDisplayAsyncLayer:)] ? 1 : 0);
-  _flags.hasClassDisplay = ([[self class] respondsToSelector:@selector(displayWithParameters:isCancelled:)] ? 1 : 0);
-  _flags.hasDrawParametersForAsyncLayer = ([self respondsToSelector:@selector(drawParametersForAsyncLayer:)] ? 1 : 0);
-
-  return self;
-}
-
 - (void)dealloc
 {
   ASDisplayNodeAssertMainThread();
@@ -142,9 +167,8 @@ BOOL ASDisplayNodeSubclassOverridesSelector(Class subclass, SEL selector)
 
   _view = nil;
   _subnodes = nil;
-  if (_flags.isLayerBacked) {
+  if (_flags.isLayerBacked)
     _layer.delegate = nil;
-  }
   _layer = nil;
 
   [self __setSupernode:nil];

AsyncDisplayKit/ASTableView.m

@@ -355,10 +355,10 @@ static BOOL _isInterceptedSelector(SEL sel)
   if (newSectionCount > sectionCount) {
     NSRange range = NSMakeRange(sectionCount, newSectionCount - sectionCount);
     NSIndexSet *sections = [NSIndexSet indexSetWithIndexesInRange:range];
-    [super insertSections:sections withRowAnimation:UITableViewRowAnimationAutomatic];
+    [super insertSections:sections withRowAnimation:UITableViewRowAnimationNone];
   }
 
-  [super insertRowsAtIndexPaths:indexPaths withRowAnimation:UITableViewRowAnimationAutomatic];
+  [super insertRowsAtIndexPaths:indexPaths withRowAnimation:UITableViewRowAnimationNone];
 
   [super endUpdates];
 }

AsyncDisplayKit/Details/ASRangeController.mm

@@ -65,6 +65,22 @@ typedef NS_ENUM(NSInteger, ASScrollDirection) {
   return self;
 }
 
+- (void)dealloc
+{
+  [self teardownAllNodes];
+}
+
+- (void)teardownAllNodes
+{
+  for (ASCellNode *node in _nodes.allValues) {
+    [node removeFromSupernode];
+    [node.view removeFromSuperview];
+  }
+  [_nodes removeAllObjects];
+  _nodes = nil;
+
+}
+
 + (dispatch_queue_t)sizingQueue
 {
   static dispatch_queue_t sizingQueue = NULL;
@@ -255,16 +271,7 @@ static BOOL ASRangeIsValid(NSRange range)
   /*
    * teardown
    */
-  for (ASCellNode *node in _nodes.objectEnumerator) {
-    [node removeFromSupernode];
-    [node.view removeFromSuperview];
-  }
-  [_nodes removeAllObjects];
-  _nodes = nil;
-
-  for (UIView *view in [[ASRangeController workingView] subviews]) {
-    [view removeFromSuperview];
-  }
+  [self teardownAllNodes];
 
   /*
    * setup

AsyncDisplayKit/Private/ASDisplayNode+AsyncDisplay.mm

@@ -23,7 +23,9 @@
 #if ASDISPLAYNODE_DELAY_DISPLAY
 static long __ASDisplayLayerMaxConcurrentDisplayCount = 1;
 #else
-static long __ASDisplayLayerMaxConcurrentDisplayCount = 1024; // essentially no limit until we determine a good value.
+// Basing this off of CPU core count would make sense, but first some experimentation should be done to understand
+// if having more ready-to-run work keeps the CPU clock up (or other interesting scheduler effects).
+static long __ASDisplayLayerMaxConcurrentDisplayCount = 8;
 #endif
 static dispatch_semaphore_t __ASDisplayLayerConcurrentDisplaySemaphore;