[ASCollectionNode] Add _ASCollectionReusableView container for supplementary nodes (#3255)

* Add _ASCollectionReusableView container for ASCollectionNode supplementary nodes with applyLayoutAttributes support

• Adds support for -[ASCellNode applyLayoutAttributes:] to supplementary nodes

* Ensure _ASCollectionReusableView has layoutAttributes if the collection view doesn’t set them

* Use correct layoutAttributes accessor for supplementary elements

Author: plarson

AsyncDisplayKit.xcodeproj/project.pbxproj

@@ -93,6 +93,8 @@
 		34EFC7721B701D0300AD841F /* ASStackLayoutSpec.mm in Sources */ = {isa = PBXBuildFile; fileRef = ACF6ED171B17843500DA7C62 /* ASStackLayoutSpec.mm */; };
 		34EFC7731B701D0700AD841F /* ASAbsoluteLayoutSpec.h in Headers */ = {isa = PBXBuildFile; fileRef = ACF6ED181B17843500DA7C62 /* ASAbsoluteLayoutSpec.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		34EFC7741B701D0A00AD841F /* ASAbsoluteLayoutSpec.mm in Sources */ = {isa = PBXBuildFile; fileRef = ACF6ED191B17843500DA7C62 /* ASAbsoluteLayoutSpec.mm */; };
+		3917EBD41E9C2FC400D04A01 /* _ASCollectionReusableView.h in Headers */ = {isa = PBXBuildFile; fileRef = 3917EBD21E9C2FC400D04A01 /* _ASCollectionReusableView.h */; settings = {ATTRIBUTES = (Private, ); }; };
+		3917EBD51E9C2FC400D04A01 /* _ASCollectionReusableView.m in Sources */ = {isa = PBXBuildFile; fileRef = 3917EBD31E9C2FC400D04A01 /* _ASCollectionReusableView.m */; };
 		3C9C128519E616EF00E942A0 /* ASTableViewTests.mm in Sources */ = {isa = PBXBuildFile; fileRef = 3C9C128419E616EF00E942A0 /* ASTableViewTests.mm */; };
 		509E68601B3AED8E009B9150 /* ASScrollDirection.m in Sources */ = {isa = PBXBuildFile; fileRef = 205F0E111B371BD7007741D0 /* ASScrollDirection.m */; };
 		509E68611B3AEDA0009B9150 /* ASAbstractLayoutController.h in Headers */ = {isa = PBXBuildFile; fileRef = 205F0E171B37339C007741D0 /* ASAbstractLayoutController.h */; };
@@ -547,6 +549,8 @@
 		299DA1A71A828D2900162D41 /* ASBatchContext.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ASBatchContext.h; sourceTree = "<group>"; };
 		299DA1A81A828D2900162D41 /* ASBatchContext.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = ASBatchContext.mm; sourceTree = "<group>"; };
 		29CDC2E11AAE70D000833CA4 /* ASBasicImageDownloaderContextTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; lineEnding = 0; path = ASBasicImageDownloaderContextTests.m; sourceTree = "<group>"; xcLanguageSpecificationIdentifier = xcode.lang.objc; };
+		3917EBD21E9C2FC400D04A01 /* _ASCollectionReusableView.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = _ASCollectionReusableView.h; sourceTree = "<group>"; };
+		3917EBD31E9C2FC400D04A01 /* _ASCollectionReusableView.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = _ASCollectionReusableView.m; sourceTree = "<group>"; };
 		3C9C128419E616EF00E942A0 /* ASTableViewTests.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; lineEnding = 0; path = ASTableViewTests.mm; sourceTree = "<group>"; xcLanguageSpecificationIdentifier = xcode.lang.objc; };
 		464052191A3F83C40061C0BA /* ASDataController.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; lineEnding = 0; path = ASDataController.h; sourceTree = "<group>"; };
 		4640521A1A3F83C40061C0BA /* ASDataController.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; lineEnding = 0; path = ASDataController.mm; sourceTree = "<group>"; };
@@ -1089,6 +1093,8 @@
 			children = (
 				CC0F885E1E4280B800576FED /* _ASCollectionViewCell.h */,
 				CC0F885D1E4280B800576FED /* _ASCollectionViewCell.m */,
+				3917EBD21E9C2FC400D04A01 /* _ASCollectionReusableView.h */,
+				3917EBD31E9C2FC400D04A01 /* _ASCollectionReusableView.m */,
 				058D09E2195D050800B7D73C /* _ASDisplayLayer.h */,
 				058D09E3195D050800B7D73C /* _ASDisplayLayer.mm */,
 				058D09E4195D050800B7D73C /* _ASDisplayView.h */,
@@ -1452,6 +1458,7 @@
 				E58E9E421E941D74004CFC59 /* ASCollectionFlowLayoutDelegate.h in Headers */,
 				696F01EC1DD2AF450049FBD5 /* ASEventLog.h in Headers */,
 				690C35641E055C7B00069B91 /* ASDimensionInternal.h in Headers */,
+				3917EBD41E9C2FC400D04A01 /* _ASCollectionReusableView.h in Headers */,
 				690C356B1E05680300069B91 /* ASDimensionDeprecated.h in Headers */,
 				683489281D70DE3400327501 /* ASDisplayNode+Deprecated.h in Headers */,
 				698371DB1E4379CD00437585 /* ASNodeController+Beta.h in Headers */,
@@ -1882,6 +1889,7 @@
 				DEB8ED7C1DD003D300DBDE55 /* ASLayoutTransition.mm in Sources */,
 				9F98C0261DBE29E000476D92 /* ASControlTargetAction.m in Sources */,
 				9C70F2091CDABA36007D6C76 /* ASViewController.mm in Sources */,
+				3917EBD51E9C2FC400D04A01 /* _ASCollectionReusableView.m in Sources */,
 				8BBBAB8D1CEBAF1E00107FC6 /* ASDefaultPlaybackButton.m in Sources */,
 				B30BF6541C59D889004FCD53 /* ASLayoutManager.m in Sources */,
 				690C35671E0567C600069B91 /* ASDimensionDeprecated.mm in Sources */,

Source/ASCollectionView.mm

@@ -27,6 +27,7 @@
 #import <AsyncDisplayKit/ASRangeController.h>
 #import <AsyncDisplayKit/_ASCollectionViewCell.h>
 #import <AsyncDisplayKit/_ASDisplayLayer.h>
+#import <AsyncDisplayKit/_ASCollectionReusableView.h>
 #import <AsyncDisplayKit/ASPagerNode.h>
 #import <AsyncDisplayKit/ASSectionContext.h>
 #import <AsyncDisplayKit/ASCollectionView+Undeprecated.h>
@@ -838,7 +839,7 @@ - (void)registerSupplementaryNodeOfKind:(NSString *)elementKind
 {
   ASDisplayNodeAssert(elementKind != nil, @"A kind is needed for supplementary node registration");
   [_registeredSupplementaryKinds addObject:elementKind];
-  [self registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:elementKind withReuseIdentifier:kReuseIdentifier];
+  [self registerClass:[_ASCollectionReusableView class] forSupplementaryViewOfKind:elementKind withReuseIdentifier:kReuseIdentifier];
 }
 
 - (void)insertSections:(NSIndexSet *)sections
@@ -997,7 +998,11 @@ - (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView
     ASDisplayNodeAssert(node != nil, @"Supplementary node should exist.  Kind = %@, indexPath = %@, collectionDataSource = %@", kind, indexPath, self);
     view = [self dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:kReuseIdentifier forIndexPath:indexPath];
   }
-
+  
+  if (_ASCollectionReusableView *reusableView = ASDynamicCast(view, _ASCollectionReusableView)) {
+    reusableView.node = node;
+  }
+  
   if (node) {
     [_rangeController configureContentView:view forCellNode:node];
   }
@@ -1111,8 +1116,14 @@ - (void)collectionView:(UICollectionView *)collectionView didEndDisplayingCell:(
   cell.layoutAttributes = nil;
 }
 
-- (void)collectionView:(UICollectionView *)collectionView willDisplaySupplementaryView:(UICollectionReusableView *)view forElementKind:(NSString *)elementKind atIndexPath:(NSIndexPath *)indexPath
+- (void)collectionView:(UICollectionView *)collectionView willDisplaySupplementaryView:(_ASCollectionReusableView *)view forElementKind:(NSString *)elementKind atIndexPath:(NSIndexPath *)indexPath
 {
+  // This is a safeguard similar to the behavior for cells in -[ASCollectionView collectionView:willDisplayCell:forItemAtIndexPath:]
+  // It ensures _ASCollectionReusableView receives layoutAttributes and calls applyLayoutAttributes.
+  if (view.layoutAttributes == nil) {
+    view.layoutAttributes = [collectionView layoutAttributesForSupplementaryElementOfKind:elementKind atIndexPath:indexPath];
+  }
+  
   if (_asyncDelegateFlags.collectionNodeWillDisplaySupplementaryElement) {
     GET_COLLECTIONNODE_OR_RETURN(collectionNode, (void)0);
     ASCellNode *node = [self supplementaryNodeForElementKind:elementKind atIndexPath:indexPath];

Source/Details/_ASCollectionReusableView.h

@@ -0,0 +1,22 @@
+//
+//  _ASCollectionReusableView.h
+//  AsyncDisplayKit
+//
+//  Created by Phil Larson on 4/10/17.
+//  Copyright © 2017 Facebook. All rights reserved.
+//
+
+#import <UIKit/UIKit.h>
+#import <AsyncDisplayKit/ASBaseDefines.h>
+
+@class ASCellNode;
+
+NS_ASSUME_NONNULL_BEGIN
+
+AS_SUBCLASSING_RESTRICTED
+@interface _ASCollectionReusableView : UICollectionReusableView
+@property (nonatomic, weak) ASCellNode *node;
+@property (nonatomic, strong, nullable) UICollectionViewLayoutAttributes *layoutAttributes;
+@end
+
+NS_ASSUME_NONNULL_END

Source/Details/_ASCollectionReusableView.m

@@ -0,0 +1,82 @@
+//
+//  _ASCollectionReusableView.m
+//  AsyncDisplayKit
+//
+//  Created by Phil Larson on 4/10/17.
+//  Copyright © 2017 Facebook. All rights reserved.
+//
+
+#import "_ASCollectionReusableView.h"
+#import "ASCellNode+Internal.h"
+#import <AsyncDisplayKit/AsyncDisplayKit.h>
+
+@implementation _ASCollectionReusableView
+
+- (void)setNode:(ASCellNode *)node
+{
+  ASDisplayNodeAssertMainThread();
+  node.layoutAttributes = _layoutAttributes;
+  _node = node;
+}
+
+- (void)setLayoutAttributes:(UICollectionViewLayoutAttributes *)layoutAttributes
+{
+  _layoutAttributes = layoutAttributes;
+  _node.layoutAttributes = layoutAttributes;
+}
+
+- (void)prepareForReuse
+{
+  self.layoutAttributes = nil;
+  
+  // Need to clear node pointer before UIKit calls setSelected:NO / setHighlighted:NO on its cells
+  self.node = nil;
+  [super prepareForReuse];
+}
+
+/**
+ * In the initial case, this is called by UICollectionView during cell dequeueing, before
+ *   we get a chance to assign a node to it, so we must be sure to set these layout attributes
+ *   on our node when one is next assigned to us in @c setNode: . Since there may be cases when we _do_ already
+ *   have our node assigned e.g. during a layout update for existing cells, we also attempt
+ *   to update it now.
+ */
+- (void)applyLayoutAttributes:(UICollectionViewLayoutAttributes *)layoutAttributes
+{
+  self.layoutAttributes = layoutAttributes;
+}
+
+/**
+ * Keep our node filling our content view.
+ */
+- (void)layoutSubviews
+{
+  [super layoutSubviews];
+  self.node.frame = self.bounds;
+}
+
+@end
+
+/**
+ * A category that makes _ASCollectionReusableView conform to IGListBindable.
+ *
+ * We don't need to do anything to bind the view model – the cell node
+ * serves the same purpose.
+ */
+#if __has_include(<IGListKit/IGListBindable.h>)
+
+#import <IGListKit/IGListBindable.h>
+
+@interface _ASCollectionReusableView (IGListBindable) <IGListBindable>
+@end
+
+@implementation _ASCollectionReusableView (IGListBindable)
+
+- (void)bindViewModel:(id)viewModel
+{
+  // nop
+}
+
+@end
+
+#endif

Tests/ASCollectionViewTests.mm

@@ -114,7 +114,7 @@ - (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollection
 
 - (ASCellNode *)collectionView:(ASCollectionView *)collectionView nodeForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
 {
-  return [[ASCellNode alloc] init];
+  return [[ASTextCellNodeWithSetSelectedCounter alloc] init];
 }
 
 - (void)collectionNode:(ASCollectionNode *)collectionNode willBeginBatchFetchWithContext:(ASBatchContext *)context
@@ -487,12 +487,24 @@ - (void)testCellNodeLayoutAttributes
   updateValidationTestPrologue
   NSSet *nodeBatch1 = [NSSet setWithArray:[cn visibleNodes]];
   XCTAssertGreaterThan(nodeBatch1.count, 0);
+  
+  NSArray<UICollectionViewLayoutAttributes *> *visibleLayoutAttributesBatch1 = [cv.collectionViewLayout layoutAttributesForElementsInRect:cv.bounds];
+  XCTAssertGreaterThan(visibleLayoutAttributesBatch1.count, 0);
 
   // Expect all visible nodes get 1 applyLayoutAttributes and have a non-nil value.
   for (ASTextCellNodeWithSetSelectedCounter *node in nodeBatch1) {
     XCTAssertEqual(node.applyLayoutAttributesCount, 1, @"Expected applyLayoutAttributes to be called exactly once for visible nodes.");
     XCTAssertNotNil(node.layoutAttributes, @"Expected layoutAttributes to be non-nil for visible cell node.");
   }
+  
+  for (UICollectionViewLayoutAttributes *layoutAttributes in visibleLayoutAttributesBatch1) {
+    if (layoutAttributes.representedElementCategory != UICollectionElementCategorySupplementaryView) {
+      continue;
+    }
+    ASTextCellNodeWithSetSelectedCounter *node = (ASTextCellNodeWithSetSelectedCounter *)[cv supplementaryNodeForElementKind:layoutAttributes.representedElementKind atIndexPath:layoutAttributes.indexPath];
+    XCTAssertEqual(node.applyLayoutAttributesCount, 1, @"Expected applyLayoutAttributes to be called exactly once for visible supplementary nodes.");
+    XCTAssertNotNil(node.layoutAttributes, @"Expected layoutAttributes to be non-nil for visible supplementary node.");
+  }
 
   // Scroll to next batch of items.
   NSIndexPath *nextIP = [NSIndexPath indexPathForItem:nodeBatch1.count inSection:0];
@@ -508,6 +520,15 @@ - (void)testCellNodeLayoutAttributes
     XCTAssertEqual(node.applyLayoutAttributesCount, 1, @"Expected applyLayoutAttributes to be called exactly once for visible nodes, even after node is removed.");
     XCTAssertNil(node.layoutAttributes, @"Expected layoutAttributes to be nil for removed cell node.");
   }
+  
+  for (UICollectionViewLayoutAttributes *layoutAttributes in visibleLayoutAttributesBatch1) {
+    if (layoutAttributes.representedElementCategory != UICollectionElementCategorySupplementaryView) {
+      continue;
+    }
+    ASTextCellNodeWithSetSelectedCounter *node = (ASTextCellNodeWithSetSelectedCounter *)[cv supplementaryNodeForElementKind:layoutAttributes.representedElementKind atIndexPath:layoutAttributes.indexPath];
+    XCTAssertEqual(node.applyLayoutAttributesCount, 1, @"Expected applyLayoutAttributes to be called exactly once for visible supplementary nodes, even after node is removed.");
+    XCTAssertNil(node.layoutAttributes, @"Expected layoutAttributes to be nil for removed supplementary node.");
+  }
 }
 
 - (void)testCellNodeIndexPathConsistency