Improvements in ASCollectionGalleryLayoutDelegate (#496)

* Improvements in ASCollectionGalleryLayoutDelegate
- It now can handle section inset, as well as interitem and line spacings
- Other small changes

* Fix build failure and update file licenses

* Update CHANGELOG

* Minor change

* Another assertion on scrollable directions of gallery layout delegate

AsyncDisplayKit.xcodeproj/project.pbxproj

@@ -429,9 +429,11 @@
 		E54E81FC1EB357BD00FFE8E1 /* ASPageTable.h in Headers */ = {isa = PBXBuildFile; fileRef = E54E81FA1EB357BD00FFE8E1 /* ASPageTable.h */; };
 		E54E81FD1EB357BD00FFE8E1 /* ASPageTable.m in Sources */ = {isa = PBXBuildFile; fileRef = E54E81FB1EB357BD00FFE8E1 /* ASPageTable.m */; };
 		E55D86331CA8A14000A0C26F /* ASLayoutElement.mm in Sources */ = {isa = PBXBuildFile; fileRef = E55D86311CA8A14000A0C26F /* ASLayoutElement.mm */; };
+		E5667E8C1F33871300FA6FC0 /* _ASCollectionGalleryLayoutInfo.h in Headers */ = {isa = PBXBuildFile; fileRef = E5667E8B1F33871300FA6FC0 /* _ASCollectionGalleryLayoutInfo.h */; settings = {ATTRIBUTES = (Private, ); }; };
+		E5667E8E1F33872700FA6FC0 /* _ASCollectionGalleryLayoutInfo.m in Sources */ = {isa = PBXBuildFile; fileRef = E5667E8D1F33872700FA6FC0 /* _ASCollectionGalleryLayoutInfo.m */; };
 		E5711A2C1C840C81009619D4 /* ASCollectionElement.h in Headers */ = {isa = PBXBuildFile; fileRef = E5711A2A1C840C81009619D4 /* ASCollectionElement.h */; settings = {ATTRIBUTES = (Private, ); }; };
 		E5711A301C840C96009619D4 /* ASCollectionElement.mm in Sources */ = {isa = PBXBuildFile; fileRef = E5711A2D1C840C96009619D4 /* ASCollectionElement.mm */; };
-		E5775AFC1F13CE9F00CAC9BC /* _ASCollectionGalleryLayoutItem.h in Headers */ = {isa = PBXBuildFile; fileRef = E5775AFB1F13CE9F00CAC9BC /* _ASCollectionGalleryLayoutItem.h */; };
+		E5775AFC1F13CE9F00CAC9BC /* _ASCollectionGalleryLayoutItem.h in Headers */ = {isa = PBXBuildFile; fileRef = E5775AFB1F13CE9F00CAC9BC /* _ASCollectionGalleryLayoutItem.h */; settings = {ATTRIBUTES = (Private, ); }; };
 		E5775AFE1F13CF7400CAC9BC /* _ASCollectionGalleryLayoutItem.mm in Sources */ = {isa = PBXBuildFile; fileRef = E5775AFD1F13CF7400CAC9BC /* _ASCollectionGalleryLayoutItem.mm */; };
 		E5775B001F13D25400CAC9BC /* ASCollectionLayoutState+Private.h in Headers */ = {isa = PBXBuildFile; fileRef = E5775AFF1F13D25400CAC9BC /* ASCollectionLayoutState+Private.h */; settings = {ATTRIBUTES = (Private, ); }; };
 		E5775B021F16759300CAC9BC /* ASCollectionLayoutCache.h in Headers */ = {isa = PBXBuildFile; fileRef = E5775B011F16759300CAC9BC /* ASCollectionLayoutCache.h */; settings = {ATTRIBUTES = (Private, ); }; };
@@ -458,7 +460,7 @@
 		E5E281741E71C833006B67C2 /* ASCollectionLayoutState.h in Headers */ = {isa = PBXBuildFile; fileRef = E5E281731E71C833006B67C2 /* ASCollectionLayoutState.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		E5E281761E71C845006B67C2 /* ASCollectionLayoutState.mm in Sources */ = {isa = PBXBuildFile; fileRef = E5E281751E71C845006B67C2 /* ASCollectionLayoutState.mm */; };
 		E5E2D72E1EA780C4005C24C6 /* ASCollectionGalleryLayoutDelegate.h in Headers */ = {isa = PBXBuildFile; fileRef = E5E2D72D1EA780C4005C24C6 /* ASCollectionGalleryLayoutDelegate.h */; settings = {ATTRIBUTES = (Public, ); }; };
-		E5E2D7301EA780DF005C24C6 /* ASCollectionGalleryLayoutDelegate.m in Sources */ = {isa = PBXBuildFile; fileRef = E5E2D72F1EA780DF005C24C6 /* ASCollectionGalleryLayoutDelegate.m */; };
+		E5E2D7301EA780DF005C24C6 /* ASCollectionGalleryLayoutDelegate.mm in Sources */ = {isa = PBXBuildFile; fileRef = E5E2D72F1EA780DF005C24C6 /* ASCollectionGalleryLayoutDelegate.mm */; };
 		F711994E1D20C21100568860 /* ASDisplayNodeExtrasTests.m in Sources */ = {isa = PBXBuildFile; fileRef = F711994D1D20C21100568860 /* ASDisplayNodeExtrasTests.m */; };
 /* End PBXBuildFile section */
 
@@ -917,6 +919,8 @@
 		E54E81FA1EB357BD00FFE8E1 /* ASPageTable.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ASPageTable.h; sourceTree = "<group>"; };
 		E54E81FB1EB357BD00FFE8E1 /* ASPageTable.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = ASPageTable.m; sourceTree = "<group>"; };
 		E55D86311CA8A14000A0C26F /* ASLayoutElement.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = ASLayoutElement.mm; sourceTree = "<group>"; };
+		E5667E8B1F33871300FA6FC0 /* _ASCollectionGalleryLayoutInfo.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = _ASCollectionGalleryLayoutInfo.h; sourceTree = "<group>"; };
+		E5667E8D1F33872700FA6FC0 /* _ASCollectionGalleryLayoutInfo.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = _ASCollectionGalleryLayoutInfo.m; sourceTree = "<group>"; };
 		E5711A2A1C840C81009619D4 /* ASCollectionElement.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ASCollectionElement.h; sourceTree = "<group>"; };
 		E5711A2D1C840C96009619D4 /* ASCollectionElement.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = ASCollectionElement.mm; sourceTree = "<group>"; };
 		E5775AFB1F13CE9F00CAC9BC /* _ASCollectionGalleryLayoutItem.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = _ASCollectionGalleryLayoutItem.h; sourceTree = "<group>"; };
@@ -946,7 +950,7 @@
 		E5E281731E71C833006B67C2 /* ASCollectionLayoutState.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ASCollectionLayoutState.h; sourceTree = "<group>"; };
 		E5E281751E71C845006B67C2 /* ASCollectionLayoutState.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = ASCollectionLayoutState.mm; sourceTree = "<group>"; };
 		E5E2D72D1EA780C4005C24C6 /* ASCollectionGalleryLayoutDelegate.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ASCollectionGalleryLayoutDelegate.h; sourceTree = "<group>"; };
-		E5E2D72F1EA780DF005C24C6 /* ASCollectionGalleryLayoutDelegate.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; lineEnding = 0; path = ASCollectionGalleryLayoutDelegate.m; sourceTree = "<group>"; xcLanguageSpecificationIdentifier = xcode.lang.objcpp; };
+		E5E2D72F1EA780DF005C24C6 /* ASCollectionGalleryLayoutDelegate.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; lineEnding = 0; path = ASCollectionGalleryLayoutDelegate.mm; sourceTree = "<group>"; xcLanguageSpecificationIdentifier = xcode.lang.objcpp; };
 		EFA731F0396842FF8AB635EE /* libPods-AsyncDisplayKitTests.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; includeInIndex = 0; path = "libPods-AsyncDisplayKitTests.a"; sourceTree = BUILT_PRODUCTS_DIR; };
 		F711994D1D20C21100568860 /* ASDisplayNodeExtrasTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = ASDisplayNodeExtrasTests.m; sourceTree = "<group>"; };
 		FB07EABBCF28656C6297BC2D /* Pods-AsyncDisplayKitTests.debug.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-AsyncDisplayKitTests.debug.xcconfig"; path = "Pods/Target Support Files/Pods-AsyncDisplayKitTests/Pods-AsyncDisplayKitTests.debug.xcconfig"; sourceTree = "<group>"; };
@@ -1670,6 +1674,8 @@
 				E5855DEE1EBB4D83003639AE /* ASCollectionLayoutDefines.h */,
 				E5855DED1EBB4D83003639AE /* ASCollectionLayoutDefines.m */,
 				E5775AFF1F13D25400CAC9BC /* ASCollectionLayoutState+Private.h */,
+				E5667E8B1F33871300FA6FC0 /* _ASCollectionGalleryLayoutInfo.h */,
+				E5667E8D1F33872700FA6FC0 /* _ASCollectionGalleryLayoutInfo.m */,
 				E5775AFB1F13CE9F00CAC9BC /* _ASCollectionGalleryLayoutItem.h */,
 				E5775AFD1F13CF7400CAC9BC /* _ASCollectionGalleryLayoutItem.mm */,
 			);
@@ -1687,7 +1693,7 @@
 				E58E9E3D1E941D74004CFC59 /* ASCollectionFlowLayoutDelegate.h */,
 				E58E9E3E1E941D74004CFC59 /* ASCollectionFlowLayoutDelegate.m */,
 				E5E2D72D1EA780C4005C24C6 /* ASCollectionGalleryLayoutDelegate.h */,
-				E5E2D72F1EA780DF005C24C6 /* ASCollectionGalleryLayoutDelegate.m */,
+				E5E2D72F1EA780DF005C24C6 /* ASCollectionGalleryLayoutDelegate.mm */,
 				E54E81FA1EB357BD00FFE8E1 /* ASPageTable.h */,
 				E54E81FB1EB357BD00FFE8E1 /* ASPageTable.m */,
 			);
@@ -1824,6 +1830,8 @@
 				CC87BB951DA8193C0090E380 /* ASCellNode+Internal.h in Headers */,
 				E5775B021F16759300CAC9BC /* ASCollectionLayoutCache.h in Headers */,
 				E5775B001F13D25400CAC9BC /* ASCollectionLayoutState+Private.h in Headers */,
+				E5667E8C1F33871300FA6FC0 /* _ASCollectionGalleryLayoutInfo.h in Headers */,
+				E5775AFC1F13CE9F00CAC9BC /* _ASCollectionGalleryLayoutItem.h in Headers */,
 				E5855DF01EBB4D83003639AE /* ASCollectionLayoutDefines.h in Headers */,
 				E5B5B9D11E9BAD9800A6B726 /* ASCollectionLayoutContext+Private.h in Headers */,
 				9C8898BD1C738BB800D6B02E /* ASTextKitFontSizeAdjuster.h in Headers */,
@@ -1896,7 +1904,6 @@
 				254C6B751BF94DF4003EC431 /* ASTextKitComponents.h in Headers */,
 				B35062081B010EFD0018CF92 /* ASScrollNode.h in Headers */,
 				CCA282CC1E9EB73E0037E8B7 /* ASTipNode.h in Headers */,
-				E5775AFC1F13CE9F00CAC9BC /* _ASCollectionGalleryLayoutItem.h in Headers */,
 				25E327571C16819500A2170C /* ASPagerNode.h in Headers */,
 				CCCCCCDB1EC3EF060087FE10 /* ASTextLine.h in Headers */,
 				9C70F20E1CDBE9E5007D6C76 /* NSArray+Diffing.h in Headers */,
@@ -2251,6 +2258,7 @@
 				CCCCCCD61EC3EF060087FE10 /* ASTextDebugOption.m in Sources */,
 				34EFC75C1B701BD200AD841F /* ASDimension.mm in Sources */,
 				B350624E1B010EFD0018CF92 /* ASDisplayNode+AsyncDisplay.mm in Sources */,
+				E5667E8E1F33872700FA6FC0 /* _ASCollectionGalleryLayoutInfo.m in Sources */,
 				25E327591C16819500A2170C /* ASPagerNode.m in Sources */,
 				636EA1A41C7FF4EC00EE152F /* NSArray+Diffing.m in Sources */,
 				B35062501B010EFD0018CF92 /* ASDisplayNode+DebugTiming.mm in Sources */,
@@ -2286,7 +2294,7 @@
 				CCCCCCE01EC3EF060087FE10 /* ASTextRunDelegate.m in Sources */,
 				CCCCCCDA1EC3EF060087FE10 /* ASTextLayout.m in Sources */,
 				254C6B841BF94F8A003EC431 /* ASTextNodeWordKerner.m in Sources */,
-				E5E2D7301EA780DF005C24C6 /* ASCollectionGalleryLayoutDelegate.m in Sources */,
+				E5E2D7301EA780DF005C24C6 /* ASCollectionGalleryLayoutDelegate.mm in Sources */,
 				34EFC76B1B701CEB00AD841F /* ASLayoutSpec.mm in Sources */,
 				CC3B20861C3F76D600798563 /* ASPendingStateController.mm in Sources */,
 				254C6B8C1BF94F8A003EC431 /* ASTextKitTailTruncater.mm in Sources */,

CHANGELOG.md

@@ -7,7 +7,7 @@
 - [ASCollectionView] Add delegate bridging and index space translation for missing UICollectionViewLayout properties. [Scott Goodson](https://github.com/appleguy)
 - [ASTextNode2] Add initial implementation for link handling. [Scott Goodson](https://github.com/appleguy) [#396](https://github.com/TextureGroup/Texture/pull/396)
 - [ASTextNode2] Provide compile flag to globally enable new implementation of ASTextNode: ASTEXTNODE_EXPERIMENT_GLOBAL_ENABLE. [Scott Goodson](https://github.com/appleguy) [#396](https://github.com/TextureGroup/Texture/pull/410)
-- Add ASCollectionGalleryLayoutDelegate - an async collection layout that makes same-size collections (e.g photo galleries, pagers, etc) fast and lightweight! [Huy Nguyen](https://github.com/nguyenhuy/) [#76](https://github.com/TextureGroup/Texture/pull/76) [#451](https://github.com/TextureGroup/Texture/pull/451)
+- Add ASCollectionGalleryLayoutDelegate - an async collection layout that makes same-size collections (e.g photo galleries, pagers, etc) fast and lightweight! [Huy Nguyen](https://github.com/nguyenhuy/) [#76](https://github.com/TextureGroup/Texture/pull/76) [#451](https://github.com/TextureGroup/Texture/pull/451) [#496](https://github.com/TextureGroup/Texture/pull/496)
 - Fix an issue that causes infinite layout loop in ASDisplayNode after [#428](https://github.com/TextureGroup/Texture/pull/428) [Huy Nguyen](https://github.com/nguyenhuy) [#455](https://github.com/TextureGroup/Texture/pull/455) 
 - Fix an issue in layout transition that causes it to unexpectedly use the old layout [Huy Nguyen](https://github.com/nguyenhuy) [#464](https://github.com/TextureGroup/Texture/pull/464)
 - Add -[ASDisplayNode detailedLayoutDescription] property to aid debugging. [Adlai Holler](https://github.com/Adlai-Holler) [#476](https://github.com/TextureGroup/Texture/pull/476)

Source/ASPagerNode.m

@@ -29,7 +29,7 @@
 #import <AsyncDisplayKit/ASCollectionView+Undeprecated.h>
 #import <AsyncDisplayKit/UIResponder+AsyncDisplayKit.h>
 
-@interface ASPagerNode () <ASCollectionDataSource, ASCollectionDelegate, ASCollectionDelegateFlowLayout, ASDelegateProxyInterceptor, ASCollectionGalleryLayoutSizeProviding>
+@interface ASPagerNode () <ASCollectionDataSource, ASCollectionDelegate, ASCollectionDelegateFlowLayout, ASDelegateProxyInterceptor, ASCollectionGalleryLayoutPropertiesProviding>
 {
   __weak id <ASPagerDataSource> _pagerDataSource;
   ASPagerNodeProxy *_proxyDataSource;
@@ -75,7 +75,7 @@ - (instancetype)initUsingAsyncCollectionLayout
   ASCollectionGalleryLayoutDelegate *layoutDelegate = [[ASCollectionGalleryLayoutDelegate alloc] initWithScrollableDirections:ASScrollDirectionHorizontalDirections];
   self = [super initWithLayoutDelegate:layoutDelegate layoutFacilitator:nil];
   if (self) {
-    layoutDelegate.sizeProvider = self;
+    layoutDelegate.propertiesProvider = self;
   }
   return self;
 }
@@ -137,7 +137,7 @@ - (NSInteger)indexOfPageWithNode:(ASCellNode *)node
   return indexPath.row;
 }
 
-#pragma mark - ASCollectionGalleryLayoutSizeProviding
+#pragma mark - ASCollectionGalleryLayoutPropertiesProviding
 
 - (CGSize)sizeForElements:(ASElementMap *)elements
 {

Source/Details/ASCollectionFlowLayoutDelegate.m

@@ -76,8 +76,9 @@ + (ASCollectionLayoutState *)calculateLayoutWithContext:(ASCollectionLayoutConte
   ASSizeRange sizeRange = ASSizeRangeForCollectionLayoutThatFitsViewportSize(context.viewportSize, context.scrollableDirections);
   ASLayout *layout = [stackSpec layoutThatFits:sizeRange];
 
-  return [[ASCollectionLayoutState alloc] initWithContext:context layout:layout getElementBlock:^ASCollectionElement * _Nonnull(ASLayout * _Nonnull sublayout) {
-    return ((ASCellNode *)sublayout.layoutElement).collectionElement;
+  return [[ASCollectionLayoutState alloc] initWithContext:context layout:layout getElementBlock:^ASCollectionElement * _Nullable(ASLayout * _Nonnull sublayout) {
+    ASCellNode *node = ASDynamicCast(sublayout.layoutElement, ASCellNode);
+    return node ? node.collectionElement : nil;
   }];
 }
 

Source/Details/ASCollectionGalleryLayoutDelegate.h

@@ -17,7 +17,7 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
-@protocol ASCollectionGalleryLayoutSizeProviding <NSObject>
+@protocol ASCollectionGalleryLayoutPropertiesProviding <NSObject>
 
 /**
  * Returns the fixed size of each and every element.
@@ -30,6 +30,51 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (CGSize)sizeForElements:(ASElementMap *)elements;
 
+@optional
+
+/**
+ * Returns the minumum spacing to use between lines of items.
+ *
+ * @discussion This method will only be called on main thread.
+ *
+ * @discussion For a vertically scrolling layout, this value represents the minimum spacing between rows.
+ * For a horizontally scrolling one, it represents the minimum spacing between columns.
+ * It is not applied between the first line and the header, or between the last line and the footer.
+ * This is the same behavior as UICollectionViewFlowLayout's minimumLineSpacing.
+ *
+ * @param elements All elements in the layout.
+ *
+ * @return The interitem spacing
+ */
+- (CGFloat)minimumLineSpacingForElements:(ASElementMap *)elements;
+
+/**
+ * Returns the minumum spacing to use between items in the same row or column, depending on the scroll directions.
+ *
+ * @discussion This method will only be called on main thread.
+ *
+ * @discussion For a vertically scrolling layout, this value represents the minimum spacing between items in the same row. 
+ * For a horizontally scrolling one, it represents the minimum spacing between items in the same column.
+ * It is considered while fitting items into lines, but the actual final spacing between some items might be larger.
+ * This is the same behavior as UICollectionViewFlowLayout's minimumInteritemSpacing.
+ *
+ * @param elements All elements in the layout.
+ *
+ * @return The interitem spacing
+ */
+- (CGFloat)minimumInteritemSpacingForElements:(ASElementMap *)elements;
+
+/**
+ * Returns the margins of each section.
+ *
+ * @discussion This method will only be called on main thread.
+ *
+ * @param elements All elements in the layout.
+ *
+ * @return The margins used to layout content in a section
+ */
+- (UIEdgeInsets)sectionInsetForElements:(ASElementMap *)elements;
+
 @end
 
 /**
@@ -40,8 +85,13 @@ NS_ASSUME_NONNULL_BEGIN
 AS_SUBCLASSING_RESTRICTED
 @interface ASCollectionGalleryLayoutDelegate : NSObject <ASCollectionLayoutDelegate>
 
-@property (nonatomic, weak) id<ASCollectionGalleryLayoutSizeProviding> sizeProvider;
+@property (nonatomic, weak) id<ASCollectionGalleryLayoutPropertiesProviding> propertiesProvider;
 
+/**
+ * Designated initializer.
+ *
+ * @param scrollableDirections The scrollable directions of this layout. Must be either vertical or horizontal directions.
+ */
 - (instancetype)initWithScrollableDirections:(ASScrollDirection)scrollableDirections NS_DESIGNATED_INITIALIZER;
 
 - (instancetype)init __unavailable;