Complete overhaul of ASFlowLayoutController.

Introduced ASIndexPath for efficient handling of index paths in C++ vectors,
while maintaining the readability of ".section" and ".row" instead of
".first" and ".second" inside of complicated business logic.

Confirmed that the working range calls are firing appropriately during
ASTableViewStressTest, including the deallocation of the rich text placeholders
provided by ASTextNode.

Author: appleguy

AsyncDisplayKit/ASDisplayNode.mm

@@ -1337,6 +1337,7 @@ - (void)clearContents
 {
   self.layer.contents = nil;
   _placeholderLayer.contents = nil;
+  _placeholderImage = nil;
 }
 
 - (void)recursivelyClearContents

AsyncDisplayKit/ASTableView.mm

@@ -117,7 +117,7 @@ @interface ASTableView () <ASRangeControllerDelegate, ASDataControllerSource> {
   _ASTableViewProxy *_proxyDelegate;
 
   ASDataController *_dataController;
-  ASCollectionViewLayoutController *_layoutController;
+  ASFlowLayoutController *_layoutController;
 
   ASRangeController *_rangeController;
 
@@ -159,16 +159,17 @@ void ASPerformBlockWithoutAnimation(BOOL withoutAnimation, void (^block)()) {
 
 - (void)configureWithAsyncDataFetching:(BOOL)asyncDataFetchingEnabled
 {
-  UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
-  _layoutController = [[ASCollectionViewLayoutController alloc] initWithScrollView:self collectionViewLayout:flowLayout];
-
+  _layoutController = [[ASFlowLayoutController alloc] initWithScrollOption:ASFlowLayoutDirectionVertical];
+  
   _rangeController = [[ASRangeController alloc] init];
   _rangeController.layoutController = _layoutController;
   _rangeController.delegate = self;
 
   _dataController = [[ASDataController alloc] initWithAsyncDataFetching:asyncDataFetchingEnabled];
   _dataController.dataSource = self;
   _dataController.delegate = _rangeController;
+  
+  _layoutController.dataSource = _dataController;
 
   _asyncDataFetchingEnabled = asyncDataFetchingEnabled;
   _asyncDataSourceLocked = NO;

AsyncDisplayKit/Details/ASCollectionViewLayoutController.h

@@ -14,6 +14,5 @@
 @interface ASCollectionViewLayoutController : ASAbstractLayoutController
 
 - (instancetype)initWithCollectionView:(ASCollectionView *)collectionView;
-- (instancetype)initWithScrollView:(UIScrollView *)scrollView collectionViewLayout:(UICollectionViewLayout *)layout;
 
 @end

AsyncDisplayKit/Details/ASCollectionViewLayoutController.mm

@@ -78,20 +78,6 @@ - (instancetype)initWithCollectionView:(ASCollectionView *)collectionView
   return self;
 }
 
-- (instancetype)initWithScrollView:(UIScrollView *)scrollView collectionViewLayout:(UICollectionViewLayout *)layout
-{
-  if (!(self = [super init])) {
-    return nil;
-  }
-  
-  _scrollableDirections = ASScrollDirectionVerticalDirections;
-  _scrollView = scrollView;
-  _collectionViewLayout = layout;
-  _updateRangeBoundsIndexedByRangeType = std::vector<CGRect>(ASLayoutRangeTypeCount);
-  return self;
-}
-
-
 #pragma mark -
 #pragma mark Index Paths in Range
 

AsyncDisplayKit/Details/ASDataController.h

@@ -8,7 +8,7 @@
 
 #import <UIKit/UIKit.h>
 #import <AsyncDisplayKit/ASDealloc2MainObject.h>
-
+#import "ASFlowLayoutController.h"
 
 @class ASCellNode;
 @class ASDataController;
@@ -97,7 +97,8 @@ typedef NSUInteger ASDataControllerAnimationOptions;
  * will be updated asynchronously. The dataSource must be updated to reflect the changes before these methods has been called.
  * For each data updatin, the corresponding methods in delegate will be called.
  */
-@interface ASDataController : ASDealloc2MainObject
+@protocol ASFlowLayoutControllerDataSource;
+@interface ASDataController : ASDealloc2MainObject <ASFlowLayoutControllerDataSource>
 
 /**
  Data source for fetching data info.
@@ -167,4 +168,6 @@ typedef NSUInteger ASDataControllerAnimationOptions;
 
 - (NSArray *)nodesAtIndexPaths:(NSArray *)indexPaths;
 
+- (NSArray *)completedNodes;  // This provides efficient access to the entire _completedNodes multidimensional array.
+
 @end

AsyncDisplayKit/Details/ASDataController.mm

@@ -54,7 +54,6 @@ - (instancetype)initWithAsyncDataFetching:(BOOL)asyncDataFetchingEnabled
   _pendingEditCommandBlocks = [NSMutableArray array];
 
   _editingTransactionQueue = [[NSOperationQueue alloc] init];
-  _editingTransactionQueue.qualityOfService = NSQualityOfServiceUserInitiated;
   _editingTransactionQueue.maxConcurrentOperationCount = 1; // Serial queue
   _editingTransactionQueue.name = @"org.AsyncDisplayKit.ASDataController.editingTransactionQueue";
 
@@ -553,17 +552,15 @@ - (ASCellNode *)nodeAtIndexPath:(NSIndexPath *)indexPath
 - (NSArray *)nodesAtIndexPaths:(NSArray *)indexPaths
 {
   ASDisplayNodeAssertMainThread();
-  
-  // Make sure that any asynchronous layout operations have finished so that those nodes are present.
-  // Otherwise a failure case could be:
-  // - Reload section 2, deleting all current nodes in that section.
-  // - New nodes are created and sizing is triggered, but they are not yet added to _completedNodes.
-  // - This method is called and includes an indexPath in section 2.
-  // - Unless we wait for the layout group to finish, we will crash with array out of bounds looking for the index in _completedNodes.
-
   return ASFindElementsInMultidimensionalArrayAtIndexPaths(_completedNodes, [indexPaths sortedArrayUsingSelector:@selector(compare:)]);
 }
 
+- (NSArray *)completedNodes
+{
+  ASDisplayNodeAssertMainThread();
+  return _completedNodes;
+}
+
 #pragma mark - Dealloc
 
 - (void)dealloc

AsyncDisplayKit/Details/ASFlowLayoutController.h

@@ -15,12 +15,20 @@ typedef NS_ENUM(NSUInteger, ASFlowLayoutDirection) {
   ASFlowLayoutDirectionHorizontal,
 };
 
+@protocol ASFlowLayoutControllerDataSource
+
+- (NSArray *)completedNodes;  // This provides access to ASDataController's _completedNodes multidimensional array.
+
+@end
+
 /**
- * The controller for flow layout.
+ *  An optimized flow layout controller that supports only vertical or horizontal scrolling, not simultaneously two-dimensional scrolling.
+ *  It is used for all ASTableViews, and may be used with ASCollectionView.
  */
 @interface ASFlowLayoutController : ASAbstractLayoutController
 
 @property (nonatomic, readonly, assign) ASFlowLayoutDirection layoutDirection;
+@property (nonatomic) id <ASFlowLayoutControllerDataSource> dataSource;
 
 - (instancetype)initWithScrollOption:(ASFlowLayoutDirection)layoutDirection;