Merge pull request #689 from facebook/Synchrotron

Implementation of Synchronous Concurrency features for AsyncDisplayKit 2.0

AsyncDisplayKit/ASCellNode.h

@@ -14,6 +14,29 @@
  */
 @interface ASCellNode : ASDisplayNode
 
+/**
+ * @abstract When enabled, ensures that the cell is completely displayed before allowed onscreen.
+ *
+ * @default NO
+ * @discussion Normally, ASCellNodes are preloaded and have finished display before they are onscreen.
+ * However, if the Table or Collection's rangeTuningParameters are set to small values (or 0),
+ * or if the user is scrolling rapidly on a slow device, it is possible for a cell's display to
+ * be incomplete when it becomes visible.
+ *
+ * In this case, normally placeholder states are shown and scrolling continues uninterrupted.
+ * The finished, drawn content is then shown as soon as it is ready.
+ *
+ * With this property set to YES, the main thread will be blocked until display is complete for
+ * the cell.  This is more similar to UIKit, and in fact makes AsyncDisplayKit scrolling visually
+ * indistinguishible from UIKit's, except being faster.
+ *
+ * Using this option does not eliminate all of the performance advantages of AsyncDisplayKit.
+ * Normally, a cell has been preloading and is almost done when it reaches the screen, so the
+ * blocking time is very short.  If the rangeTuningParameters are set to 0, still this option
+ * outperforms UIKit: while the main thread is waiting, subnode display executes concurrently.
+ */
+@property (nonatomic, assign) BOOL neverShowPlaceholders;
+
 /*
  * ASTableView uses these properties when configuring UITableViewCells that host ASCellNodes.
  */

AsyncDisplayKit/ASCollectionView.h

@@ -212,6 +212,15 @@
  */
 - (ASCellNode *)nodeForItemAtIndexPath:(NSIndexPath *)indexPath;
 
+/**
+ * Similar to -indexPathForCell:.
+ *
+ * @param cellNode a cellNode part of the table view
+ *
+ * @returns an indexPath for this cellNode
+ */
+- (NSIndexPath *)indexPathForNode:(ASCellNode *)cellNode;
+
 /**
  * Similar to -visibleCells.
  *

AsyncDisplayKit/ASCollectionView.mm

@@ -17,6 +17,9 @@
 #import "UICollectionViewLayout+ASConvenience.h"
 #import "ASInternalHelpers.h"
 
+// FIXME: Temporary nonsense import until method names are finalized and exposed
+#import "ASDisplayNode+Subclasses.h"
+
 const static NSUInteger kASCollectionViewAnimationNone = UITableViewRowAnimationNone;
 
 
@@ -315,6 +318,16 @@ static BOOL _isInterceptedSelector(SEL sel)
   return [[_dataController nodeAtIndexPath:indexPath] calculatedSize];
 }
 
+- (ASCellNode *)nodeForItemAtIndexPath:(NSIndexPath *)indexPath
+{
+  return [_dataController nodeAtIndexPath:indexPath];
+}
+
+- (NSIndexPath *)indexPathForNode:(ASCellNode *)cellNode
+{
+  return [_dataController indexPathForNode:cellNode];
+}
+
 - (NSArray *)visibleNodes
 {
   NSArray *indexPaths = [self indexPathsForVisibleItems];
@@ -392,11 +405,6 @@ static BOOL _isInterceptedSelector(SEL sel)
   [_dataController moveRowAtIndexPath:indexPath toIndexPath:newIndexPath withAnimationOptions:kASCollectionViewAnimationNone];
 }
 
-- (ASCellNode *)nodeForItemAtIndexPath:(NSIndexPath *)indexPath
-{
-  return [_dataController nodeAtIndexPath:indexPath];
-}
-
 #pragma mark -
 #pragma mark Intercepted selectors.
 
@@ -490,6 +498,11 @@ static BOOL _isInterceptedSelector(SEL sel)
   if ([_asyncDelegate respondsToSelector:@selector(collectionView:willDisplayNodeForItemAtIndexPath:)]) {
     [_asyncDelegate collectionView:self willDisplayNodeForItemAtIndexPath:indexPath];
   }
+  
+  ASCellNode *cellNode = [self nodeForItemAtIndexPath:indexPath];
+  if (cellNode.neverShowPlaceholders) {
+    [cellNode recursivelyEnsureDisplay];
+  }
 }
 
 - (void)collectionView:(UICollectionView *)collectionView didEndDisplayingCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath

AsyncDisplayKit/ASDisplayNode+Subclasses.h

@@ -429,6 +429,38 @@
 // This method has proven helpful in a few rare scenarios, similar to a category extension on UIView,
 // but it's considered private API for now and its use should not be encouraged.
 - (ASDisplayNode *)_supernodeWithClass:(Class)supernodeClass;
+
+// The two methods below will eventually be exposed, but their names are subject to change.
+/**
+ * @abstract Ensure that all rendering is complete for this node and its descendents.
+ *
+ * @discussion Calling this method on the main thread after a node is added to the view heirarchy will ensure that
+ * placeholder states are never visible to the user.  It is used by ASTableView, ASCollectionView, and ASViewController
+ * to implement their respective ".neverShowPlaceholders" option.
+ *
+ * If all nodes have layer.contents set and/or their layer does not have -needsDisplay set, the method will return immediately.
+ *
+ * This method is capable of handling a mixed set of nodes, with some not having started display, some in progress on an
+ * asynchronous display operation, and some already finished.
+ *
+ * In order to guarantee against deadlocks, this method should only be called on the main thread.
+ * It may block on the private queue, [_ASDisplayLayer displayQueue]
+ */
+- (void)recursivelyEnsureDisplay;
+
+/**
+ * @abstract Allows a node to bypass all ensureDisplay passes.  Defaults to NO.
+ *
+ * @discussion Nodes that are expensive to draw and expected to have placeholder even with
+ * .neverShowPlaceholders enabled should set this to YES.
+ *
+ * ASImageNode uses the default of NO, as it is often used for UI images that are expected to synchronize with ensureDisplay.
+ *
+ * ASNetworkImageNode and ASMultiplexImageNode set this to YES, because they load data from a database or server,
+ * and are expected to support a placeholder state given that display is often blocked on slow data fetching.
+ */
+@property (nonatomic, assign) BOOL shouldBypassEnsureDisplay;
+
 @end
 
 #define ASDisplayNodeAssertThreadAffinity(viewNode)   ASDisplayNodeAssert(!viewNode || ASDisplayNodeThreadIsMain() || !(viewNode).nodeLoaded, @"Incorrect display node thread affinity")

AsyncDisplayKit/ASDisplayNode.mm

@@ -14,6 +14,7 @@
 #import <objc/runtime.h>
 
 #import "_ASAsyncTransaction.h"
+#import "_ASAsyncTransactionContainer+Private.h"
 #import "_ASPendingState.h"
 #import "_ASDisplayView.h"
 #import "_ASScopeTimer.h"
@@ -1415,6 +1416,68 @@ static NSInteger incrementIfFound(NSInteger i) {
   [_placeholderLayer removeFromSuperlayer];
 }
 
+void recursivelyEnsureDisplayForLayer(CALayer *layer)
+{
+  // This recursion must handle layers in various states:
+  // 1. Just added to hierarchy, CA hasn't yet called -display
+  // 2. Previously in a hierarchy (such as a working window owned by an Intelligent Preloading class, like ASTableView / ASCollectionView / ASViewController)
+  // 3. Has no content to display at all
+  // Specifically for case 1), we need to explicitly trigger a -display call now.
+  // Otherwise, there is no opportunity to block the main thread after CoreAnimation's transaction commit
+  // (even a runloop observer at a late call order will not stop the next frame from compositing, showing placeholders).
+  
+  ASDisplayNode *node = [layer asyncdisplaykit_node];
+  if (!layer.contents && [node _implementsDisplay]) {
+    // For layers that do get displayed here, this immediately kicks off the work on the concurrent -[_ASDisplayLayer displayQueue].
+    // At the same time, it creates an associated _ASAsyncTransaction, which we can use to block on display completion.  See ASDisplayNode+AsyncDisplay.mm.
+    [layer displayIfNeeded];
+  }
+  
+  // Kick off the recursion first, so that all necessary display calls are sent and the displayQueue is full of parallelizable work.
+  for (CALayer *sublayer in layer.sublayers) {
+    recursivelyEnsureDisplayForLayer(sublayer);
+  }
+  
+  // As the recursion unwinds, verify each transaction is complete and block if it is not.
+  // While blocking on one transaction, others may be completing concurrently, so it doesn't matter which blocks first.
+  BOOL waitUntilComplete = (!node.shouldBypassEnsureDisplay);
+  if (waitUntilComplete) {
+    for (_ASAsyncTransaction *transaction in [layer.asyncdisplaykit_asyncLayerTransactions copy]) {
+      // Even if none of the layers have had a chance to start display earlier, they will still be allowed to saturate a multicore CPU while blocking main.
+      // This significantly reduces time on the main thread relative to UIKit.
+      [transaction waitUntilComplete];
+    }
+  }
+}
+
+- (void)recursivelyEnsureDisplay
+{
+  ASDisplayNodeAssertMainThread();
+  ASDisplayNodeAssert(self.isNodeLoaded, @"Node must have layer or view loaded to use -recursivelyEnsureDisplay");
+  ASDisplayNodeAssert(self.inHierarchy && (self.isLayerBacked || self.view.window != nil), @"Node must be in a hierarchy to use -recursivelyEnsureDisplay");
+  
+  CALayer *layer = self.layer;
+  // -layoutIfNeeded is recursive, and even walks up to superlayers to check if they need layout,
+  // so we should call it outside of starting the recursion below.  If our own layer is not marked
+  // as dirty, we can assume layout has run on this subtree before.
+  if ([layer needsLayout]) {
+    [layer layoutIfNeeded];
+  }
+  recursivelyEnsureDisplayForLayer(layer);
+}
+
+- (void)setShouldBypassEnsureDisplay:(BOOL)shouldBypassEnsureDisplay
+{
+  ASDN::MutexLocker l(_propertyLock);
+  _flags.shouldBypassEnsureDisplay = shouldBypassEnsureDisplay;
+}
+
+- (BOOL)shouldBypassEnsureDisplay
+{
+  ASDN::MutexLocker l(_propertyLock);
+  return _flags.shouldBypassEnsureDisplay;
+}
+
 #pragma mark - For Subclasses
 
 - (ASLayout *)calculateLayoutThatFits:(ASSizeRange)constrainedSize
@@ -1484,6 +1547,7 @@ static NSInteger incrementIfFound(NSInteger i) {
   ASDN::MutexLocker l(_propertyLock);
   return _preferredFrameSize;
 }
+
 - (UIImage *)placeholderImage
 {
   return nil;

AsyncDisplayKit/ASMultiplexImageNode.mm

@@ -158,6 +158,7 @@ typedef void(^ASMultiplexImageLoadCompletionBlock)(UIImage *image, id imageIdent
 
   _cache = cache;
   _downloader = downloader;
+  self.shouldBypassEnsureDisplay = YES;
 
   return self;
 }

AsyncDisplayKit/ASNetworkImageNode.mm

@@ -44,6 +44,7 @@
   _cache = cache;
   _downloader = downloader;
   _shouldCacheImage = YES;
+  self.shouldBypassEnsureDisplay = YES;
 
   return self;
 }

AsyncDisplayKit/ASTableView.h

@@ -27,8 +27,28 @@
  */
 @interface ASTableView : UITableView
 
-@property (nonatomic, weak) id<ASTableViewDataSource> asyncDataSource;
 @property (nonatomic, weak) id<ASTableViewDelegate> asyncDelegate;      // must not be nil
+@property (nonatomic, weak) id<ASTableViewDataSource> asyncDataSource;
+
+/**
+ * Initializer.
+ *
+ * @param frame A rectangle specifying the initial location and size of the table view in its superview’€™s coordinates.
+ * The frame of the table view changes as table cells are added and deleted.
+ *
+ * @param style A constant that specifies the style of the table view. See UITableViewStyle for descriptions of valid constants.
+ *
+ * @param asyncDataFetchingEnabled This option is reserved for future use, and currently a no-op.
+ *
+ * @discussion If asyncDataFetching is enabled, the `ASTableView` will fetch data through `tableView:numberOfRowsInSection:` and
+ * `tableView:nodeForRowAtIndexPath:` in async mode from background thread. Otherwise, the methods will be invoked synchronically
+ * from calling thread.
+ * Enabling asyncDataFetching could avoid blocking main thread for `ASCellNode` allocation, which is frequently reported issue for
+ * large scale data. On another hand, the application code need take the responsibility to avoid data inconsistence. Specifically,
+ * we will lock the data source through `tableViewLockDataSource`, and unlock it by `tableViewUnlockDataSource` after the data fetching.
+ * The application should not update the data source while the data source is locked, to keep data consistence.
+ */
+- (instancetype)initWithFrame:(CGRect)frame style:(UITableViewStyle)style asyncDataFetching:(BOOL)asyncDataFetchingEnabled;
 
 /**
  * Tuning parameters for a range.
@@ -50,26 +70,6 @@
  */
 - (void)setTuningParameters:(ASRangeTuningParameters)tuningParameters forRangeType:(ASLayoutRangeType)rangeType;
 
-/**
- * Initializer.
- *
- * @param frame A rectangle specifying the initial location and size of the table view in its superview’€™s coordinates. 
- * The frame of the table view changes as table cells are added and deleted.
- *
- * @param style A constant that specifies the style of the table view. See UITableViewStyle for descriptions of valid constants.
- *
- * @param asyncDataFetchingEnabled Enable the data fetching in async mode.
- * 
- * @discussion If asyncDataFetching is enabled, the `ASTableView` will fetch data through `tableView:numberOfRowsInSection:` and
- * `tableView:nodeForRowAtIndexPath:` in async mode from background thread. Otherwise, the methods will be invoked synchronically 
- * from calling thread.
- * Enabling asyncDataFetching could avoid blocking main thread for `ASCellNode` allocation, which is frequently reported issue for 
- * large scale data. On another hand, the application code need take the responsibility to avoid data inconsistence. Specifically, 
- * we will lock the data source through `tableViewLockDataSource`, and unlock it by `tableViewUnlockDataSource` after the data fetching. 
- * The application should not update the data source while the data source is locked, to keep data consistence.
- */
-- (instancetype)initWithFrame:(CGRect)frame style:(UITableViewStyle)style asyncDataFetching:(BOOL)asyncDataFetchingEnabled;
-
 /**
  * The number of screens left to scroll before the delegate -tableView:beginBatchFetchingWithContext: is called.
  *

AsyncDisplayKit/ASTableView.mm

@@ -18,6 +18,9 @@
 #import "ASInternalHelpers.h"
 #import "ASLayout.h"
 
+// FIXME: Temporary nonsense import until method names are finalized and exposed
+#import "ASDisplayNode+Subclasses.h"
+
 //#define LOG(...) NSLog(__VA_ARGS__)
 #define LOG(...)
 
@@ -569,6 +572,11 @@ void ASPerformBlockWithoutAnimation(BOOL withoutAnimation, void (^block)()) {
   if ([_asyncDelegate respondsToSelector:@selector(tableView:willDisplayNodeForRowAtIndexPath:)]) {
     [_asyncDelegate tableView:self willDisplayNodeForRowAtIndexPath:indexPath];
   }
+
+  ASCellNode *cellNode = [self nodeForRowAtIndexPath:indexPath];
+  if (cellNode.neverShowPlaceholders) {
+    [cellNode recursivelyEnsureDisplay];
+  }
 }
 
 - (void)tableView:(UITableView *)tableView didEndDisplayingCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath*)indexPath

AsyncDisplayKit/ASViewController.h

@@ -13,7 +13,11 @@
 
 @property (nonatomic, strong, readonly) ASDisplayNode *node;
 
-//TODO Use nonnull annotation late on. Travis doesn't recognize it (yet).
+// AsyncDisplayKit 2.0 BETA: This property is still being tested, but it allows
+// blocking as a view controller becomes visible to ensure no placeholders flash onscreen.
+// Refer to examples/SynchronousConcurrency, AsyncViewController.m
+@property (nonatomic, assign) BOOL neverShowPlaceholders;
+
 - (instancetype)initWithNode:(ASDisplayNode *)node;
 
 @end

AsyncDisplayKit/ASViewController.m

@@ -10,7 +10,13 @@
 #import "ASAssert.h"
 #import "ASDimension.h"
 
+// FIXME: Temporary nonsense import until method names are finalized and exposed
+#import "ASDisplayNode+Subclasses.h"
+
 @implementation ASViewController
+{
+  BOOL _ensureDisplayed;
+}
 
 - (instancetype)initWithNode:(ASDisplayNode *)node
 {
@@ -33,15 +39,25 @@
 
 - (void)viewWillLayoutSubviews
 {
+  [super viewWillLayoutSubviews];
   CGSize viewSize = self.view.bounds.size;
   ASSizeRange constrainedSize = ASSizeRangeMake(viewSize, viewSize);
   [_node measureWithSizeRange:constrainedSize];
-  [super viewWillLayoutSubviews];
+}
+
+- (void)viewDidLayoutSubviews
+{
+  if (_ensureDisplayed && self.neverShowPlaceholders) {
+    _ensureDisplayed = NO;
+    [self.node recursivelyEnsureDisplay];
+  }
+  [super viewDidLayoutSubviews];
 }
 
 - (void)viewWillAppear:(BOOL)animated
 {
   [super viewWillAppear:animated];
+  _ensureDisplayed = YES;
   [_node recursivelyFetchData];
 }
 

AsyncDisplayKit/Details/Transactions/_ASAsyncTransaction.h

@@ -26,6 +26,7 @@ typedef NS_ENUM(NSUInteger, ASAsyncTransactionState) {
   ASAsyncTransactionStateOpen = 0,
   ASAsyncTransactionStateCommitted,
   ASAsyncTransactionStateCanceled,
+  ASAsyncTransactionStateComplete
 };
 
 /**
@@ -54,6 +55,13 @@ typedef NS_ENUM(NSUInteger, ASAsyncTransactionState) {
 - (id)initWithCallbackQueue:(dispatch_queue_t)callbackQueue
             completionBlock:(asyncdisplaykit_async_transaction_completion_block_t)completionBlock;
 
+/**
+ @summary Block the main thread until the transaction is complete, including callbacks.
+ 
+ @desc This must be called on the main thread.
+ */
+- (void)waitUntilComplete;
+
 /**
  The dispatch queue that the completion blocks will be called on.
  */

AsyncDisplayKit/Details/Transactions/_ASAsyncTransaction.m

@@ -7,7 +7,7 @@
  */
 
 #import "_ASAsyncTransaction.h"
-
+#import "_ASAsyncTransactionGroup.h"
 #import "ASAssert.h"
 
 @interface ASDisplayNodeAsyncTransactionOperation : NSObject
@@ -40,6 +40,11 @@
   }
 }
 
+- (NSString *)description
+{
+  return [NSString stringWithFormat:@"<ASDisplayNodeAsyncTransactionOperation: %p - value = %@", self, self.value];
+}
+
 @end
 
 @implementation _ASAsyncTransaction
@@ -140,7 +145,7 @@
   ASDisplayNodeAssertMainThread();
   ASDisplayNodeAssert(_state == ASAsyncTransactionStateOpen, @"You cannot double-commit a transaction");
   _state = ASAsyncTransactionStateCommitted;
-
+  
   if ([_operations count] == 0) {
     // Fast path: if a transaction was opened, but no operations were added, execute completion block synchronously.
     if (_completionBlock) {
@@ -148,18 +153,59 @@
     }
   } else {
     ASDisplayNodeAssert(_group != NULL, @"If there are operations, dispatch group should have been created");
+    
     dispatch_group_notify(_group, _callbackQueue, ^{
-      BOOL isCanceled = (_state == ASAsyncTransactionStateCanceled);
-      for (ASDisplayNodeAsyncTransactionOperation *operation in _operations) {
-        [operation callAndReleaseCompletionBlock:isCanceled];
-      }
-      if (_completionBlock) {
-        _completionBlock(self, isCanceled);
-      }
+      // _callbackQueue is the main queue in current practice (also asserted in -waitUntilComplete).
+      // This code should be reviewed before taking on significantly different use cases.
+      ASDisplayNodeAssertMainThread();
+      [self completeTransaction];
     });
   }
 }
 
+- (void)completeTransaction
+{
+  if (_state != ASAsyncTransactionStateComplete) {
+    BOOL isCanceled = (_state == ASAsyncTransactionStateCanceled);
+    for (ASDisplayNodeAsyncTransactionOperation *operation in _operations) {
+      [operation callAndReleaseCompletionBlock:isCanceled];
+    }
+    
+    // Always set _state to Complete, even if we were cancelled, to block any extraneous
+    // calls to this method that may have been scheduled for the next runloop
+    // (e.g. if we needed to force one in this runloop with -waitUntilComplete, but another was already scheduled)
+    _state = ASAsyncTransactionStateComplete;
+
+    if (_completionBlock) {
+      _completionBlock(self, isCanceled);
+    }
+  }
+}
+
+- (void)waitUntilComplete
+{
+  ASDisplayNodeAssertMainThread();
+  if (_state != ASAsyncTransactionStateComplete) {
+    if (_group) {
+      ASDisplayNodeAssertTrue(_callbackQueue == dispatch_get_main_queue());
+      dispatch_group_wait(_group, DISPATCH_TIME_FOREVER);
+      
+      // At this point, the asynchronous operation may have completed, but the runloop
+      // observer has not committed the batch of transactions we belong to.  It's important to
+      // commit ourselves via the group to avoid double-committing the transaction.
+      // This is only necessary when forcing display work to complete before allowing the runloop
+      // to continue, e.g. in the implementation of -[ASDisplayNode recursivelyEnsureDisplay].
+      if (_state == ASAsyncTransactionStateOpen) {
+        [_ASAsyncTransactionGroup commit];
+        ASDisplayNodeAssert(_state != ASAsyncTransactionStateOpen, @"Transaction should not be open after committing group");
+      }
+      // If we needed to commit the group above, -completeTransaction may have already been run.
+      // It is designed to accomodate this by checking _state to ensure it is not complete.
+      [self completeTransaction];
+    }
+  }
+}
+
 #pragma mark -
 #pragma mark Helper Methods
 
@@ -174,4 +220,9 @@
   }
 }
 
+- (NSString *)description
+{
+  return [NSString stringWithFormat:@"<_ASAsyncTransaction: %p - _state = %lu, _group = %@, _operations = %@>", self, (unsigned long)_state, _group, _operations];
+}
+
 @end

AsyncDisplayKit/Details/Transactions/_ASAsyncTransactionGroup.h

@@ -15,6 +15,7 @@
 @interface _ASAsyncTransactionGroup : NSObject
 /// The main transaction group is scheduled to commit on every tick of the main runloop.
 + (instancetype)mainTransactionGroup;
++ (void)commit;
 
 /// Add a transaction container to be committed.
 /// @param containerLayer A layer containing a transaction to be commited. May or may not be a container layer.

AsyncDisplayKit/Details/Transactions/_ASAsyncTransactionGroup.m

@@ -95,6 +95,11 @@ static void _transactionGroupRunLoopObserverCallback(CFRunLoopObserverRef observ
   }
 }
 
++ (void)commit
+{
+  [[_ASAsyncTransactionGroup mainTransactionGroup] commit];
+}
+
 @end
 
 static void _transactionGroupRunLoopObserverCallback(CFRunLoopObserverRef observer, CFRunLoopActivity activity, void *info)

AsyncDisplayKit/Private/ASDisplayNodeInternal.h

@@ -80,6 +80,7 @@ typedef NS_OPTIONS(NSUInteger, ASDisplayNodeMethodOverrides) {
     unsigned layerBacked:1;
     unsigned displaysAsynchronously:1;
     unsigned shouldRasterizeDescendants:1;
+    unsigned shouldBypassEnsureDisplay:1;
     unsigned displaySuspended:1;
 
     // whether custom drawing is enabled

examples/SynchronousConcurrency/Podfile

@@ -0,0 +1,3 @@
+source 'https://github.com/CocoaPods/Specs.git'
+platform :ios, '8.0'
+pod 'AsyncDisplayKit', :path => '../..'

examples/SynchronousConcurrency/Sample.xcodeproj/project.pbxproj

@@ -0,0 +1,361 @@
+// !$*UTF8*$!
+{
+	archiveVersion = 1;
+	classes = {
+	};
+	objectVersion = 46;
+	objects = {
+
+/* Begin PBXBuildFile section */
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+/* End PBXBuildFile section */
+
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+		05E2128519D4DB510098F589 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
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+				GCC_PREPROCESSOR_DEFINITIONS = (
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+					"$(inherited)",
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+				GCC_SYMBOLS_PRIVATE_EXTERN = NO;
+				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
+				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;
+				GCC_WARN_UNDECLARED_SELECTOR = YES;
+				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
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+				MTL_ENABLE_DEBUG_INFO = YES;
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+			buildSettings = {
+				ALWAYS_SEARCH_USER_PATHS = NO;
+				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
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+				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
+				INFOPLIST_FILE = Sample/Info.plist;
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+/* Begin XCConfigurationList section */
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+}

examples/SynchronousConcurrency/Sample.xcodeproj/project.xcworkspace/contents.xcworkspacedata

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Workspace
+   version = "1.0">
+   <FileRef
+      location = "self:Sample.xcodeproj">
+   </FileRef>
+</Workspace>

examples/SynchronousConcurrency/Sample.xcodeproj/xcshareddata/xcschemes/Sample.xcscheme

@@ -0,0 +1,88 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Scheme
+   LastUpgradeVersion = "0620"
+   version = "1.3">
+   <BuildAction
+      parallelizeBuildables = "YES"
+      buildImplicitDependencies = "YES">
+      <BuildActionEntries>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "YES"
+            buildForProfiling = "YES"
+            buildForArchiving = "YES"
+            buildForAnalyzing = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "05E2128019D4DB510098F589"
+               BuildableName = "Sample.app"
+               BlueprintName = "Sample"
+               ReferencedContainer = "container:Sample.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
+      </BuildActionEntries>
+   </BuildAction>
+   <TestAction
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      shouldUseLaunchSchemeArgsEnv = "YES"
+      buildConfiguration = "Debug">
+      <Testables>
+      </Testables>
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "05E2128019D4DB510098F589"
+            BuildableName = "Sample.app"
+            BlueprintName = "Sample"
+            ReferencedContainer = "container:Sample.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
+   </TestAction>
+   <LaunchAction
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      launchStyle = "0"
+      useCustomWorkingDirectory = "NO"
+      buildConfiguration = "Debug"
+      ignoresPersistentStateOnLaunch = "NO"
+      debugDocumentVersioning = "YES"
+      allowLocationSimulation = "YES">
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+         runnableDebuggingMode = "0">
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+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "05E2128019D4DB510098F589"
+            BuildableName = "Sample.app"
+            BlueprintName = "Sample"
+            ReferencedContainer = "container:Sample.xcodeproj">
+         </BuildableReference>
+      </BuildableProductRunnable>
+      <AdditionalOptions>
+      </AdditionalOptions>
+   </LaunchAction>
+   <ProfileAction
+      shouldUseLaunchSchemeArgsEnv = "YES"
+      savedToolIdentifier = ""
+      useCustomWorkingDirectory = "NO"
+      buildConfiguration = "Release"
+      debugDocumentVersioning = "YES">
+      <BuildableProductRunnable
+         runnableDebuggingMode = "0">
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "05E2128019D4DB510098F589"
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+            BlueprintName = "Sample"
+            ReferencedContainer = "container:Sample.xcodeproj">
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examples/SynchronousConcurrency/Sample.xcworkspace/contents.xcworkspacedata

@@ -0,0 +1 @@
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examples/SynchronousConcurrency/Sample/AppDelegate.h

@@ -0,0 +1,20 @@
+/* This file provided by Facebook is for non-commercial testing and evaluation
+ * purposes only.  Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#import <UIKit/UIKit.h>
+
+#define UseAutomaticLayout 1
+
+@interface AppDelegate : UIResponder <UIApplicationDelegate>
+
+@property (strong, nonatomic) UIWindow *window;
+
+@end

examples/SynchronousConcurrency/Sample/AppDelegate.m

@@ -0,0 +1,33 @@
+/* This file provided by Facebook is for non-commercial testing and evaluation
+ * purposes only.  Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#import "AppDelegate.h"
+
+#import "AsyncTableViewController.h"
+#import "AsyncViewController.h"
+
+@implementation AppDelegate
+
+- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
+{
+  self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
+  self.window.backgroundColor = [UIColor whiteColor];
+  
+  UITabBarController *tabBarController = [[UITabBarController alloc] initWithNibName:nil bundle:nil];
+  self.window.rootViewController = tabBarController;
+  
+  [tabBarController setViewControllers:@[[[AsyncTableViewController alloc] init], [[AsyncViewController alloc] init]]];
+  
+  [self.window makeKeyAndVisible];
+  return YES;
+}
+
+@end

examples/SynchronousConcurrency/Sample/AsyncTableViewController.h

@@ -0,0 +1,16 @@
+/* This file provided by Facebook is for non-commercial testing and evaluation
+ * purposes only.  Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#import <UIKit/UIKit.h>
+
+@interface AsyncTableViewController : UIViewController
+
+@end

examples/SynchronousConcurrency/Sample/AsyncTableViewController.m

@@ -0,0 +1,91 @@
+/* This file provided by Facebook is for non-commercial testing and evaluation
+ * purposes only.  Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#import <AsyncDisplayKit/AsyncDisplayKit.h>
+#import <AsyncDisplayKit/ASAssert.h>
+
+#import "AsyncTableViewController.h"
+#import "RandomCoreGraphicsNode.h"
+
+@interface AsyncTableViewController () <ASTableViewDataSource, ASTableViewDelegate>
+{
+  ASTableView *_tableView;
+}
+
+@end
+
+@implementation AsyncTableViewController
+
+#pragma mark -
+#pragma mark UIViewController.
+
+- (instancetype)init
+{
+  if (!(self = [super init]))
+    return nil;
+
+  _tableView = [[ASTableView alloc] initWithFrame:CGRectZero style:UITableViewStylePlain];
+  _tableView.separatorStyle = UITableViewCellSeparatorStyleNone;
+  _tableView.asyncDataSource = self;
+  _tableView.asyncDelegate = self;
+  
+  ASRangeTuningParameters tuningParameters;
+  tuningParameters.leadingBufferScreenfuls = 0.5;
+  tuningParameters.trailingBufferScreenfuls = 1.0;
+  [_tableView setTuningParameters:tuningParameters forRangeType:ASLayoutRangeTypePreload];
+  [_tableView setTuningParameters:tuningParameters forRangeType:ASLayoutRangeTypeRender];
+  
+  self.tabBarItem = [[UITabBarItem alloc] initWithTabBarSystemItem:UITabBarSystemItemFeatured tag:0];
+  self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemRedo
+                                                                                         target:self
+                                                                                         action:@selector(reloadEverything)];
+
+  return self;
+}
+
+- (void)reloadEverything
+{
+  [_tableView reloadData];
+}
+
+- (void)viewDidLoad
+{
+  [super viewDidLoad];
+
+  [self.view addSubview:_tableView];
+}
+
+- (void)viewWillLayoutSubviews
+{
+  _tableView.frame = self.view.bounds;
+}
+
+- (BOOL)prefersStatusBarHidden
+{
+  return YES;
+}
+
+#pragma mark -
+#pragma mark ASTableView.
+
+- (ASCellNode *)tableView:(ASTableView *)tableView nodeForRowAtIndexPath:(NSIndexPath *)indexPath
+{
+  RandomCoreGraphicsNode *elementNode = [[RandomCoreGraphicsNode alloc] init];
+  elementNode.preferredFrameSize = CGSizeMake(320, 100);
+  return elementNode;
+}
+
+- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
+{
+  return 100;
+}
+
+@end

examples/SynchronousConcurrency/Sample/AsyncViewController.h

@@ -0,0 +1,13 @@
+//
+//  AsyncViewController.h
+//  Sample
+//
+//  Created by Scott Goodson on 9/26/15.
+//  Copyright © 2015 Facebook. All rights reserved.
+//
+
+#import "ASViewController.h"
+
+@interface AsyncViewController : ASViewController <UITabBarControllerDelegate>
+
+@end

examples/SynchronousConcurrency/Sample/AsyncViewController.m

@@ -0,0 +1,37 @@
+//
+//  AsyncViewController.m
+//  Sample
+//
+//  Created by Scott Goodson on 9/26/15.
+//  Copyright © 2015 Facebook. All rights reserved.
+//
+
+#import "AsyncViewController.h"
+#import "RandomCoreGraphicsNode.h"
+
+@implementation AsyncViewController
+
+- (instancetype)init
+{
+  if (!(self = [super initWithNode:[[RandomCoreGraphicsNode alloc] init]])) {
+    return nil;
+  }
+
+  self.neverShowPlaceholders = YES;
+  self.tabBarItem = [[UITabBarItem alloc] initWithTabBarSystemItem:UITabBarSystemItemFavorites tag:0];
+  return self;
+}
+
+- (void)viewWillAppear:(BOOL)animated
+{
+  // FIXME: This is only being called on the first time the UITabBarController shows us.
+  [super viewWillAppear:animated];
+}
+
+- (void)viewDidDisappear:(BOOL)animated
+{
+  [self.node recursivelyClearContents];
+  [super viewDidDisappear:animated];
+}
+
+@end

examples/SynchronousConcurrency/Sample/Info.plist

@@ -0,0 +1,36 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleDevelopmentRegion</key>
+	<string>en</string>
+	<key>CFBundleExecutable</key>
+	<string>$(EXECUTABLE_NAME)</string>
+	<key>CFBundleIdentifier</key>
+	<string>com.facebook.AsyncDisplayKit.$(PRODUCT_NAME:rfc1034identifier)</string>
+	<key>CFBundleInfoDictionaryVersion</key>
+	<string>6.0</string>
+	<key>CFBundleName</key>
+	<string>$(PRODUCT_NAME)</string>
+	<key>CFBundlePackageType</key>
+	<string>APPL</string>
+	<key>CFBundleShortVersionString</key>
+	<string>1.0</string>
+	<key>CFBundleSignature</key>
+	<string>????</string>
+	<key>CFBundleVersion</key>
+	<string>1</string>
+	<key>LSRequiresIPhoneOS</key>
+	<true/>
+	<key>UIRequiredDeviceCapabilities</key>
+	<array>
+		<string>armv7</string>
+	</array>
+	<key>UISupportedInterfaceOrientations</key>
+	<array>
+		<string>UIInterfaceOrientationPortrait</string>
+		<string>UIInterfaceOrientationLandscapeLeft</string>
+		<string>UIInterfaceOrientationLandscapeRight</string>
+	</array>
+</dict>
+</plist>

examples/SynchronousConcurrency/Sample/RandomCoreGraphicsNode.h

@@ -0,0 +1,16 @@
+//
+//  RandomCoreGraphicsNode.h
+//  Sample
+//
+//  Created by Scott Goodson on 9/5/15.
+//  Copyright (c) 2015 Facebook. All rights reserved.
+//
+
+#import <AsyncDisplayKit/AsyncDisplayKit.h>
+
+@interface RandomCoreGraphicsNode : ASCellNode
+{
+  ASTextNode *_textNode;
+}
+
+@end

examples/SynchronousConcurrency/Sample/RandomCoreGraphicsNode.m

@@ -0,0 +1,93 @@
+//
+//  RandomCoreGraphicsNode.m
+//  Sample
+//
+//  Created by Scott Goodson on 9/5/15.
+//  Copyright (c) 2015 Facebook. All rights reserved.
+//
+
+#import "RandomCoreGraphicsNode.h"
+#import <AsyncDisplayKit/ASDisplayNode+Subclasses.h>
+
+@implementation RandomCoreGraphicsNode
+
++ (UIColor *)randomColor
+{
+  CGFloat hue = ( arc4random() % 256 / 256.0 );  //  0.0 to 1.0
+  CGFloat saturation = ( arc4random() % 128 / 256.0 ) + 0.5;  //  0.5 to 1.0, away from white
+  CGFloat brightness = ( arc4random() % 128 / 256.0 ) + 0.5;  //  0.5 to 1.0, away from black
+  return [UIColor colorWithHue:hue saturation:saturation brightness:brightness alpha:1];
+}
+
++ (void)drawRect:(CGRect)bounds withParameters:(id<NSObject>)parameters isCancelled:(asdisplaynode_iscancelled_block_t)isCancelledBlock isRasterizing:(BOOL)isRasterizing
+{
+  CGFloat locations[3];
+  NSMutableArray *colors = [NSMutableArray arrayWithCapacity:3];
+  [colors addObject:(id)[[RandomCoreGraphicsNode randomColor] CGColor]];
+  locations[0] = 0.0;
+  [colors addObject:(id)[[RandomCoreGraphicsNode randomColor] CGColor]];
+  locations[1] = 1.0;
+  [colors addObject:(id)[[RandomCoreGraphicsNode randomColor] CGColor]];
+  locations[2] = ( arc4random() % 256 / 256.0 );
+
+  
+  CGContextRef ctx = UIGraphicsGetCurrentContext();
+  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
+  CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (CFArrayRef)colors, locations);
+  
+  CGGradientDrawingOptions drawingOptions;
+  CGContextDrawLinearGradient(ctx, gradient, CGPointZero, CGPointMake(bounds.size.width, bounds.size.height), drawingOptions);
+  
+  CGColorSpaceRelease(colorSpace);
+}
+
+- (NSObject *)drawParametersForAsyncLayer:(_ASDisplayLayer *)layer
+{
+  return [self description];
+}
+
+- (NSDictionary *)textStyle
+{
+  UIFont *font = [UIFont fontWithName:@"HelveticaNeue" size:36.0f];
+  
+  NSMutableParagraphStyle *style = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
+  style.paragraphSpacing = 0.5 * font.lineHeight;
+  style.hyphenationFactor = 1.0;
+  
+  return @{ NSFontAttributeName: font,
+            NSParagraphStyleAttributeName: style };
+}
+
+- (instancetype)init
+{
+  if (!(self = [super init])) {
+    return nil;
+  }
+  
+  _textNode = [[ASTextNode alloc] init];
+  _textNode.placeholderEnabled = NO;
+  _textNode.attributedString = [[NSAttributedString alloc] initWithString:@"Hello, ASDK!"
+                                                               attributes:[self textStyle]];
+  [self addSubnode:_textNode];
+  
+  return self;
+}
+
+- (CGSize)calculateSizeThatFits:(CGSize)constrainedSize
+{
+  [_textNode measure:constrainedSize];
+  return CGSizeMake(constrainedSize.width, 100);
+}
+
+- (void)layout
+{
+  CGSize boundsSize = self.bounds.size;
+  CGSize textSize = _textNode.calculatedSize;
+  CGRect textRect = CGRectMake(roundf((boundsSize.width - textSize.width) / 2.0),
+                               roundf((boundsSize.height - textSize.height) / 2.0),
+                               textSize.width,
+                               textSize.height);
+  _textNode.frame = textRect;
+}
+
+@end

examples/SynchronousConcurrency/Sample/main.m

@@ -0,0 +1,20 @@
+/* This file provided by Facebook is for non-commercial testing and evaluation
+ * purposes only.  Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#import <UIKit/UIKit.h>
+
+#import "AppDelegate.h"
+
+int main(int argc, char * argv[]) {
+  @autoreleasepool {
+      return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
+  }
+}