Further implement data controller support and layout introspection

AsyncDisplayKit/ASCollectionView.h

@@ -17,7 +17,7 @@
 @class ASCellNode;
 @protocol ASCollectionViewDataSource;
 @protocol ASCollectionViewDelegate;
-
+@protocol ASCollectionViewLayoutInspecting;
 
 /**
  * Node-based collection view.
@@ -80,6 +80,13 @@
  */
 @property (nonatomic, assign) CGFloat leadingScreensForBatching;
 
+/**
+ * Optional introspection object for the collection view's layout.
+ *
+ * TODO: Discuss more about this delegate
+ */
+@property (nonatomic, weak) id<ASCollectionViewLayoutInspecting> layoutDelegate;
+
 /**
  *  Perform a batch of updates asynchronously, optionally disabling all animations in the batch. This method must be called from the main thread. 
  *  The asyncDataSource must be updated to reflect the changes before the update block completes.
@@ -119,7 +126,7 @@
  */
 - (void)reloadData;
 
-- (void)registerSupplementaryViewOfKind:(NSString *)elementKind;
+- (void)registerSupplementaryNodeOfKind:(NSString *)elementKind;
 
 /**
  * Inserts one or more sections.

AsyncDisplayKit/ASCollectionView.mm

@@ -16,6 +16,7 @@
 #import "ASBatchFetching.h"
 #import "UICollectionViewLayout+ASConvenience.h"
 #import "ASInternalHelpers.h"
+#import "ASCollectionViewFlowLayoutInspector.h"
 
 // FIXME: Temporary nonsense import until method names are finalized and exposed
 #import "ASDisplayNode+Subclasses.h"
@@ -137,6 +138,7 @@ static BOOL _isInterceptedSelector(SEL sel)
   ASCollectionDataController *_dataController;
   ASRangeController *_rangeController;
   ASCollectionViewLayoutController *_layoutController;
+  ASCollectionViewFlowLayoutInspector *_flowLayoutInspector;
 
   BOOL _performingBatchUpdates;
   NSMutableArray *_batchUpdateBlocks;
@@ -203,6 +205,10 @@ static BOOL _isInterceptedSelector(SEL sel)
   _dataController.delegate = _rangeController;
   _dataController.dataSource = self;
   
+  _flowLayoutInspector = [[ASCollectionViewFlowLayoutInspector alloc] init];
+  // TODO: Implement a better path of falling-back to a flow layout
+  _flowLayoutInspector.layout = (UICollectionViewFlowLayout *)layout;
+  
   _batchContext = [[ASBatchContext alloc] init];
 
   _leadingScreensForBatching = 1.0;
@@ -377,7 +383,7 @@ static BOOL _isInterceptedSelector(SEL sel)
   [self performBatchAnimated:YES updates:updates completion:completion];
 }
 
-- (void)registerSupplementaryViewOfKind:(NSString *)elementKind
+- (void)registerSupplementaryNodeOfKind:(NSString *)elementKind
 {
   [self registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:elementKind
                                             withReuseIdentifier:[self __reuseIdentifierForKind:elementKind]];
@@ -677,6 +683,11 @@ static BOOL _isInterceptedSelector(SEL sel)
   return constrainedSize;
 }
 
+- (ASSizeRange)dataController:(ASCollectionDataController *)dataController constrainedSizeForSupplementaryNodeOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
+{
+  return [self.layoutDelegate collectionView:self constrainedSizeForSupplementaryNodeOfKind:kind atIndexPath:indexPath];
+}
+
 - (NSUInteger)dataController:(ASDataController *)dataController rowsInSection:(NSUInteger)section
 {
   return [_asyncDataSource collectionView:self numberOfItemsInSection:section];

AsyncDisplayKit/Details/ASCollectionDataController.h

@@ -17,9 +17,14 @@
 
 @protocol ASCollectionDataControllerSource <ASDataControllerSource>
 
-- (ASDisplayNode *)dataController:(ASDataController *)dataController supplementaryNodeOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath;
+- (ASDisplayNode *)dataController:(ASCollectionDataController *)dataController supplementaryNodeOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath;
 
-- (NSArray *)supplementaryKindsInDataController:(ASCollectionDataController *)dataController;
+/**
+ The constrained size range for layout.
+ */
+- (ASSizeRange)dataController:(ASCollectionDataController *)dataController constrainedSizeForSupplementaryNodeOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath;
+
+- (NSArray *)supplementaryNodeKindsInDataController:(ASCollectionDataController *)dataController;
 
 - (NSUInteger)dataController:(ASCollectionDataController *)dataController numberOfSectionsForSupplementaryKind:(NSString *)kind;
 

AsyncDisplayKit/Details/ASCollectionDataController.mm

@@ -14,6 +14,12 @@
 #import "ASDisplayNodeInternal.h"
 #import "ASDataController+Subclasses.h"
 
+@interface ASCollectionDataController ()
+
+- (id<ASCollectionDataControllerSource>)collectionDataSource;
+
+@end
+
 @implementation ASCollectionDataController {
   NSMutableDictionary *_completedSupplementaryNodes;
   NSMutableDictionary *_editingSupplementaryNodes;
@@ -24,21 +30,23 @@
   [self performEditCommandWithBlock:^{
     ASDisplayNodeAssertMainThread();
     [self accessDataSourceWithBlock:^{
-      NSArray *elementKinds = [self.collectionDataSource supplementaryKindsInDataController:self];
+      NSArray *elementKinds = [self.collectionDataSource supplementaryNodeKindsInDataController:self];
       [elementKinds enumerateObjectsUsingBlock:^(NSString *kind, NSUInteger idx, BOOL * _Nonnull stop) {
         _completedSupplementaryNodes[kind] = [NSMutableArray array];
         _editingSupplementaryNodes[kind] = [NSMutableArray array];
         
         NSMutableArray *indexPaths = [NSMutableArray array];
         NSMutableArray *nodes = [NSMutableArray array];
-        [self _populateAllNodesOfKind:kind withMutableNodes:nodes mutableIndexPaths:indexPaths];
-        [self batchLayoutNodes:nodes atIndexPaths:indexPaths completion:nil];
+        [self _populateSupplementaryNodesOfKind:kind withMutableNodes:nodes mutableIndexPaths:indexPaths];
+        [self batchLayoutNodes:nodes atIndexPaths:indexPaths constrainedSize:^ASSizeRange(NSIndexPath *indexPath) {
+          return [self.collectionDataSource dataController:self constrainedSizeForSupplementaryNodeOfKind:kind atIndexPath:indexPath];
+        } completion:nil];
       }];
     }];
   }];
 }
        
-- (void)_populateAllNodesOfKind:(NSString *)kind withMutableNodes:(NSMutableArray *)nodes mutableIndexPaths:(NSMutableArray *)indexPaths
+- (void)_populateSupplementaryNodesOfKind:(NSString *)kind withMutableNodes:(NSMutableArray *)nodes mutableIndexPaths:(NSMutableArray *)indexPaths
 {
   NSUInteger sectionCount = [self.collectionDataSource dataController:self numberOfSectionsForSupplementaryKind:kind];
   for (NSUInteger i = 0; i < sectionCount; i++) {
@@ -65,6 +73,7 @@
 
 #pragma mark - Internal Data Querying
 
+// TODO: Reduce code duplication by exposing generic insert/delete helpers from ASDataController
 - (void)_insertNodes:(NSArray *)nodes ofKind:(NSString *)kind atIndexPaths:(NSArray *)indexPaths
 {
   if (indexPaths.count == 0)
@@ -78,6 +87,7 @@
   });
 }
 
+// TODO: Reduce code duplication by exposing generic insert/delete helpers from ASDataController
 - (void)_deleteNodesOfKind:(NSString *)kind atIndexPaths:(NSArray *)indexPaths
 {
   if (indexPaths.count == 0)

AsyncDisplayKit/Details/ASCollectionViewFlowLayoutInspector.h

@@ -0,0 +1,31 @@
+//
+//  ASCollectionViewFlowLayoutInspector.h
+//  Pods
+//
+//  Created by Levi McCallum on 9/29/15.
+//
+//
+
+#import <Foundation/Foundation.h>
+
+#import <AsyncDisplayKit/ASDimension.h>
+
+@class ASCollectionView;
+
+@protocol ASCollectionViewLayoutInspecting <NSObject>
+
+- (ASSizeRange)collectionView:(ASCollectionView *)collectionView constrainedSizeForSupplementaryNodeOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath;
+
+- (NSUInteger)collectionView:(ASCollectionView *)collectionView supplementaryViewsOfKind:(NSString *)kind inSection:(NSUInteger)section;
+
+@end
+
+@interface ASCollectionViewFlowLayoutInspector : NSObject <ASCollectionViewLayoutInspecting>
+
+@property (nonatomic, weak) UICollectionViewFlowLayout *layout;
+
+- (ASSizeRange)collectionView:(ASCollectionView *)collectionView constrainedSizeForSupplementaryNodeOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath;
+
+- (NSUInteger)collectionView:(ASCollectionView *)collectionView supplementaryViewsOfKind:(NSString *)kind inSection:(NSUInteger)section;
+
+@end

AsyncDisplayKit/Details/ASCollectionViewFlowLayoutInspector.m

@@ -0,0 +1,33 @@
+//
+//  ASCollectionViewFlowLayoutInspector.m
+//  Pods
+//
+//  Created by Levi McCallum on 9/29/15.
+//
+//
+
+#import "ASCollectionViewFlowLayoutInspector.h"
+
+#import "ASCollectionView.h"
+
+@implementation ASCollectionViewFlowLayoutInspector
+
+- (ASSizeRange)collectionView:(ASCollectionView *)collectionView constrainedSizeForSupplementaryNodeOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
+{
+  // TODO: Implement some heuristic that follows the width/height constraints of header and footer supplementary views
+  return ASSizeRangeMake(CGSizeZero, CGSizeMake(FLT_MAX, FLT_MAX));
+}
+
+- (NSUInteger)collectionView:(ASCollectionView *)collectionView supplementaryViewsOfKind:(NSString *)kind inSection:(NSUInteger)section
+{
+  NSUInteger count = 0;
+  if (self.layout.headerReferenceSize.width > 0 || self.layout.headerReferenceSize.height > 0) {
+    count++;
+  }
+  if (self.layout.footerReferenceSize.width > 0 || self.layout.footerReferenceSize.height > 0) {
+    count++;
+  }
+  return count;
+}
+
+@end

AsyncDisplayKit/Details/ASDataController+Subclasses.h

@@ -25,6 +25,9 @@
  */
 - (void)accessDataSourceWithBlock:(dispatch_block_t)block;
 
-- (void)batchLayoutNodes:(NSArray *)nodes atIndexPaths:(NSArray *)indexPaths completion:(void (^)(NSArray *nodes, NSArray *indexPaths))block;
+/**
+ * Measure and layout the given nodes in optimized batches, constraining each to a given size.
+ */
+- (void)batchLayoutNodes:(NSArray *)nodes atIndexPaths:(NSArray *)indexPaths constrainedSize:(ASSizeRange (^)(NSIndexPath *indexPath))constraintedSizeBlock completion:(void (^)(NSArray *nodes, NSArray *indexPaths))completionBlock;
 
 @end

AsyncDisplayKit/Details/ASDataController.mm

@@ -113,7 +113,7 @@ static void *kASSizingQueueContext = &kASSizingQueueContext;
   }];
 }
 
-- (void)_layoutNodes:(NSArray *)nodes atIndexPaths:(NSArray *)indexPaths completion:(void (^)(NSArray *, NSArray *))block
+- (void)_layoutNodes:(NSArray *)nodes atIndexPaths:(NSArray *)indexPaths constrainedSize:(ASSizeRange (^)(NSIndexPath *indexPath))constraintedSizeBlock completion:(void (^)(NSArray *nodes, NSArray *indexPaths))completionBlock
 {
   ASDisplayNodeAssert([NSOperationQueue currentQueue] == _editingTransactionQueue, @"Cell node layout must be initiated from edit transaction queue");
   
@@ -129,7 +129,7 @@ static void *kASSizingQueueContext = &kASSizingQueueContext;
     for (NSUInteger k = j; k < j + batchCount; k++) {
       ASCellNode *node = nodes[k];
       if (!node.isNodeLoaded) {
-        nodeBoundSizes[k] = [_dataSource dataController:self constrainedSizeForNodeAtIndexPath:indexPaths[k]];
+        nodeBoundSizes[k] = constraintedSizeBlock(indexPaths[k]);
       }
     }
     
@@ -151,10 +151,10 @@ static void *kASSizingQueueContext = &kASSizingQueueContext;
   dispatch_group_wait(layoutGroup, DISPATCH_TIME_FOREVER);
   free(nodeBoundSizes);
 
-  block(nodes, indexPaths);
+  completionBlock(nodes, indexPaths);
 }
 
-- (void)batchLayoutNodes:(NSArray *)nodes atIndexPaths:(NSArray *)indexPaths completion:(void (^)(NSArray *nodes, NSArray *indexPaths))block
+- (void)batchLayoutNodes:(NSArray *)nodes atIndexPaths:(NSArray *)indexPaths constrainedSize:(ASSizeRange (^)(NSIndexPath *indexPath))constraintedSizeBlock completion:(void (^)(NSArray *nodes, NSArray *indexPaths))completionBlock
 {
   NSUInteger blockSize = [[ASDataController class] parallelProcessorCount] * kASDataControllerSizingCountPerProcessor;
   
@@ -164,14 +164,15 @@ static void *kASSizingQueueContext = &kASSizingQueueContext;
     NSArray *batchedIndexPaths = [indexPaths subarrayWithRange:batchedRange];
     NSArray *batchedNodes = [nodes subarrayWithRange:batchedRange];
     
-    [self _layoutNodes:batchedNodes atIndexPaths:batchedIndexPaths completion:block];
+    [self _layoutNodes:batchedNodes atIndexPaths:batchedIndexPaths constrainedSize:constraintedSizeBlock completion:completionBlock];
   }
 }
 
 - (void)_batchLayoutNodes:(NSArray *)nodes atIndexPaths:(NSArray *)indexPaths withAnimationOptions:(ASDataControllerAnimationOptions)animationOptions
 {
-  
-  [self batchLayoutNodes:nodes atIndexPaths:indexPaths completion:^(NSArray *nodes, NSArray *indexPaths) {
+  [self batchLayoutNodes:nodes atIndexPaths:indexPaths constrainedSize:^ASSizeRange(NSIndexPath *indexPath) {
+    return [_dataSource dataController:self constrainedSizeForNodeAtIndexPath:indexPath];
+  } completion:^(NSArray *nodes, NSArray *indexPaths) {
     // Insert finished nodes into data storage
     [self _insertNodes:nodes atIndexPaths:indexPaths withAnimationOptions:animationOptions];
   }];

examples/ASCollectionView/Sample/ViewController.m

@@ -39,8 +39,8 @@
   _collectionView.asyncDelegate = self;
   _collectionView.backgroundColor = [UIColor whiteColor];
   
-  [_collectionView registerSupplementaryViewOfKind:UICollectionElementKindSectionHeader];
-  [_collectionView registerSupplementaryViewOfKind:UICollectionElementKindSectionFooter];
+  [_collectionView registerSupplementaryNodeOfKind:UICollectionElementKindSectionHeader];
+  [_collectionView registerSupplementaryNodeOfKind:UICollectionElementKindSectionFooter];
   
   return self;
 }