[ASCollectionLayout] Add ASCollectionGalleryLayoutSizeProviding (#451)

* Add ASCollectionGalleryLayoutSizeProviding
- This allows users to return different sizes based on certain conditions, such as the collection node's bounds or grid constants.
- ASPagerNode will also act as a size provider to ensure all pages have an up-to-date size that is its bounds.

* Update CHANGELOG

* ASPagerNode to use gallery layout delegate if told to

AsyncDisplayKit.xcodeproj/project.pbxproj

@@ -425,6 +425,7 @@
 		DECBD6EA1BE56E1900CF4905 /* ASButtonNode.mm in Sources */ = {isa = PBXBuildFile; fileRef = DECBD6E61BE56E1900CF4905 /* ASButtonNode.mm */; };
 		DEFAD8131CC48914000527C4 /* ASVideoNode.mm in Sources */ = {isa = PBXBuildFile; fileRef = AEEC47E01C20C2DD00EC1693 /* ASVideoNode.mm */; };
 		E51B78BF1F028ABF00E32604 /* ASLayoutFlatteningTests.m in Sources */ = {isa = PBXBuildFile; fileRef = E51B78BD1F01A0EE00E32604 /* ASLayoutFlatteningTests.m */; };
+		E54E00721F1D3828000B30D7 /* ASPagerNode+Beta.h in Headers */ = {isa = PBXBuildFile; fileRef = E54E00711F1D3828000B30D7 /* ASPagerNode+Beta.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		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 */; };
@@ -912,6 +913,7 @@
 		E51B78BD1F01A0EE00E32604 /* ASLayoutFlatteningTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = ASLayoutFlatteningTests.m; sourceTree = "<group>"; };
 		E52405B21C8FEF03004DC8E7 /* ASLayoutTransition.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = ASLayoutTransition.mm; sourceTree = "<group>"; };
 		E52405B41C8FEF16004DC8E7 /* ASLayoutTransition.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ASLayoutTransition.h; sourceTree = "<group>"; };
+		E54E00711F1D3828000B30D7 /* ASPagerNode+Beta.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "ASPagerNode+Beta.h"; sourceTree = "<group>"; };
 		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>"; };
@@ -1101,6 +1103,7 @@
 				698371DA1E4379CD00437585 /* ASNodeController+Beta.m */,
 				25E327541C16819500A2170C /* ASPagerNode.h */,
 				25E327551C16819500A2170C /* ASPagerNode.m */,
+				E54E00711F1D3828000B30D7 /* ASPagerNode+Beta.h */,
 				A2763D771CBDD57D00A9ADBD /* ASPINRemoteImageDownloader.h */,
 				A2763D781CBDD57D00A9ADBD /* ASPINRemoteImageDownloader.m */,
 				CCBBBF5C1EB161760069AA91 /* ASRangeManagingNode.h */,
@@ -1708,6 +1711,7 @@
 			isa = PBXHeadersBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				E54E00721F1D3828000B30D7 /* ASPagerNode+Beta.h in Headers */,
 				E5B225281F1790D6001E1431 /* ASHashing.h in Headers */,
 				CC034A131E649F1300626263 /* AsyncDisplayKit+IGListKitMethods.h in Headers */,
 				693A1DCA1ECC944E00D0C9D2 /* IGListAdapter+AsyncDisplayKit.h in Headers */,

CHANGELOG.md

@@ -4,7 +4,7 @@
 - [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)
+ - 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)
 
 ##2.3.5
 - Fix an issue where inserting/deleting sections could lead to inconsistent supplementary element behavior. [Adlai Holler](https://github.com/Adlai-Holler)

Source/ASPagerNode+Beta.h

@@ -0,0 +1,19 @@
+//
+//  ASPagerNode+Beta.h
+//  Texture
+//
+//  Copyright (c) 2017-present, Pinterest, Inc.  All rights reserved.
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+
+#import <AsyncDisplayKit/ASPagerNode.h>
+
+@interface ASPagerNode (Beta)
+
+- (instancetype)initUsingAsyncCollectionLayout;
+
+@end

Source/ASPagerNode.m

@@ -16,6 +16,10 @@
 //
 
 #import <AsyncDisplayKit/ASPagerNode.h>
+#import <AsyncDisplayKit/ASPagerNode+Beta.h>
+
+#import <AsyncDisplayKit/ASCollectionGalleryLayoutDelegate.h>
+#import <AsyncDisplayKit/ASCollectionNode+Beta.h>
 #import <AsyncDisplayKit/ASDelegateProxy.h>
 #import <AsyncDisplayKit/ASDisplayNode+FrameworkPrivate.h>
 #import <AsyncDisplayKit/ASDisplayNode+Subclasses.h>
@@ -25,7 +29,7 @@
 #import <AsyncDisplayKit/ASCollectionView+Undeprecated.h>
 #import <AsyncDisplayKit/UIResponder+AsyncDisplayKit.h>
 
-@interface ASPagerNode () <ASCollectionDataSource, ASCollectionDelegate, ASCollectionDelegateFlowLayout, ASDelegateProxyInterceptor>
+@interface ASPagerNode () <ASCollectionDataSource, ASCollectionDelegate, ASCollectionDelegateFlowLayout, ASDelegateProxyInterceptor, ASCollectionGalleryLayoutSizeProviding>
 {
   __weak id <ASPagerDataSource> _pagerDataSource;
   ASPagerNodeProxy *_proxyDataSource;
@@ -66,6 +70,16 @@
   return self;
 }
 
+- (instancetype)initUsingAsyncCollectionLayout
+{
+  ASCollectionGalleryLayoutDelegate *layoutDelegate = [[ASCollectionGalleryLayoutDelegate alloc] initWithScrollableDirections:ASScrollDirectionHorizontalDirections];
+  self = [super initWithLayoutDelegate:layoutDelegate layoutFacilitator:nil];
+  if (self) {
+    layoutDelegate.sizeProvider = self;
+  }
+  return self;
+}
+
 #pragma mark - ASDisplayNode
 
 - (void)didLoad
@@ -123,6 +137,14 @@
   return indexPath.row;
 }
 
+#pragma mark - ASCollectionGalleryLayoutSizeProviding
+
+- (CGSize)sizeForElements:(ASElementMap *)elements
+{
+  ASDisplayNodeAssertMainThread();
+  return self.bounds.size;
+}
+
 #pragma mark - ASCollectionDataSource
 
 - (ASCellNodeBlock)collectionNode:(ASCollectionNode *)collectionNode nodeBlockForItemAtIndexPath:(NSIndexPath *)indexPath

Source/Details/ASCollectionFlowLayoutDelegate.m

@@ -46,11 +46,13 @@
 
 - (ASScrollDirection)scrollableDirections
 {
+  ASDisplayNodeAssertMainThread();
   return _scrollableDirections;
 }
 
 - (id)additionalInfoForLayoutWithElements:(ASElementMap *)elements
 {
+  ASDisplayNodeAssertMainThread();
   return nil;
 }
 
@@ -59,9 +61,7 @@
   ASElementMap *elements = context.elements;
   NSMutableArray<ASCellNode *> *children = ASArrayByFlatMapping(elements.itemElements, ASCollectionElement *element, element.node);
   if (children.count == 0) {
-    return [[ASCollectionLayoutState alloc] initWithContext:context
+    return [[ASCollectionLayoutState alloc] initWithContext:context];
-                                                contentSize:CGSizeZero
-                             elementToLayoutAttributesTable:[NSMapTable elementToLayoutAttributesTable]];
   }
   
   ASStackLayoutSpec *stackSpec = [ASStackLayoutSpec stackLayoutSpecWithDirection:ASStackLayoutDirectionHorizontal

Source/Details/ASCollectionGalleryLayoutDelegate.h

@@ -13,8 +13,25 @@
 #import <AsyncDisplayKit/ASCollectionLayoutDelegate.h>
 #import <AsyncDisplayKit/ASScrollDirection.h>
 
+@class ASElementMap;
+
 NS_ASSUME_NONNULL_BEGIN
 
+@protocol ASCollectionGalleryLayoutSizeProviding <NSObject>
+
+/**
+ * Returns the fixed size of each and every element.
+ *
+ * @discussion This method will only be called on main thread.
+ *
+ * @param elements All elements to be sized.
+ *
+ * @return The elements' size
+ */
+- (CGSize)sizeForElements:(ASElementMap *)elements;
+
+@end
+
 /**
  * A thread-safe layout delegate that arranges items with the same size into a flow layout.
  *
@@ -23,7 +40,9 @@ NS_ASSUME_NONNULL_BEGIN
 AS_SUBCLASSING_RESTRICTED
 @interface ASCollectionGalleryLayoutDelegate : NSObject <ASCollectionLayoutDelegate>
 
-- (instancetype)initWithScrollableDirections:(ASScrollDirection)scrollableDirections itemSize:(CGSize)itemSize NS_DESIGNATED_INITIALIZER;
+@property (nonatomic, weak) id<ASCollectionGalleryLayoutSizeProviding> sizeProvider;
+
+- (instancetype)initWithScrollableDirections:(ASScrollDirection)scrollableDirections NS_DESIGNATED_INITIALIZER;
 
 - (instancetype)init __unavailable;
 

Source/Details/ASCollectionGalleryLayoutDelegate.m

@@ -31,40 +31,47 @@
   CGSize _itemSize;
 }
 
-- (instancetype)initWithScrollableDirections:(ASScrollDirection)scrollableDirections itemSize:(CGSize)itemSize
+- (instancetype)initWithScrollableDirections:(ASScrollDirection)scrollableDirections
 {
   self = [super init];
   if (self) {
-    ASDisplayNodeAssertFalse(CGSizeEqualToSize(CGSizeZero, itemSize));
     _scrollableDirections = scrollableDirections;
-    _itemSize = itemSize;
   }
   return self;
 }
 
 - (ASScrollDirection)scrollableDirections
 {
+  ASDisplayNodeAssertMainThread();
   return _scrollableDirections;
 }
 
 - (id)additionalInfoForLayoutWithElements:(ASElementMap *)elements
 {
-  return [NSValue valueWithCGSize:_itemSize];
+  ASDisplayNodeAssertMainThread();
+  if (_sizeProvider == nil) {
+    return nil;
+  }
+
+  return [NSValue valueWithCGSize:[_sizeProvider sizeForElements:elements]];
 }
 
 + (ASCollectionLayoutState *)calculateLayoutWithContext:(ASCollectionLayoutContext *)context
 {
   ASElementMap *elements = context.elements;
   CGSize pageSize = context.viewportSize;
-  CGSize itemSize = ((NSValue *)context.additionalInfo).CGSizeValue;
   ASScrollDirection scrollableDirections = context.scrollableDirections;
+
+  CGSize itemSize = context.additionalInfo ? ((NSValue *)context.additionalInfo).CGSizeValue : CGSizeZero;
+  if (CGSizeEqualToSize(CGSizeZero, itemSize)) {
+    return [[ASCollectionLayoutState alloc] initWithContext:context];
+  }
+
   NSMutableArray<_ASGalleryLayoutItem *> *children = ASArrayByFlatMapping(elements.itemElements,
                                                                           ASCollectionElement *element,
                                                                           [[_ASGalleryLayoutItem alloc] initWithItemSize:itemSize collectionElement:element]);
   if (children.count == 0) {
-    return [[ASCollectionLayoutState alloc] initWithContext:context
+    return [[ASCollectionLayoutState alloc] initWithContext:context];
-                                                contentSize:CGSizeZero
-                             elementToLayoutAttributesTable:[NSMapTable weakToStrongObjectsMapTable]];
   }
   
   // Use a stack spec to calculate layout content size and frames of all elements without actually measuring each element

Source/Details/ASCollectionLayoutContext.m

@@ -37,7 +37,6 @@
 {
   self = [super init];
   if (self) {
-    ASDisplayNodeAssertTrue([layoutDelegateClass conformsToProtocol:@protocol(ASCollectionLayoutDelegate)]);
     _viewportSize = viewportSize;
     _scrollableDirections = scrollableDirections;
     _elements = elements;

Source/Details/ASCollectionLayoutDelegate.h

@@ -30,6 +30,8 @@ NS_ASSUME_NONNULL_BEGIN
  * It will be available in the context parameter in +calculateLayoutWithContext:
  *
  * @return The scrollable directions.
+ *
+ * @discusstion This method will be called on main thread.
  */
 - (ASScrollDirection)scrollableDirections;
 

Source/Details/ASCollectionLayoutState.h

@@ -56,6 +56,13 @@ AS_SUBCLASSING_RESTRICTED
                     contentSize:(CGSize)contentSize
  elementToLayoutAttributesTable:(NSMapTable<ASCollectionElement *, UICollectionViewLayoutAttributes *> *)table NS_DESIGNATED_INITIALIZER;
 
+/**
+ * Convenience initializer. Returns an object with zero content size and an empty table.
+ *
+ * @param context The context used to calculate this object
+ */
+- (instancetype)initWithContext:(ASCollectionLayoutContext *)context;
+
 /**
  * Convenience initializer.
  *

Source/Details/ASCollectionLayoutState.mm

@@ -39,6 +39,13 @@
   ASPageToLayoutAttributesTable *_unmeasuredPageToLayoutAttributesTable;
 }
 
+- (instancetype)initWithContext:(ASCollectionLayoutContext *)context
+{
+  return [self initWithContext:context
+                   contentSize:CGSizeZero
+elementToLayoutAttributesTable:[NSMapTable elementToLayoutAttributesTable]];
+}
+
 - (instancetype)initWithContext:(ASCollectionLayoutContext *)context
                          layout:(ASLayout *)layout
                 getElementBlock:(ASCollectionElement *(^)(ASLayout *))getElementBlock

Source/Private/ASCollectionLayout.mm

@@ -85,12 +85,9 @@ static const ASScrollDirection kASStaticScrollDirection = (ASScrollDirectionRigh
 + (ASCollectionLayoutState *)calculateLayoutWithContext:(ASCollectionLayoutContext *)context
 {
   if (context.elements == nil) {
-    return [[ASCollectionLayoutState alloc] initWithContext:context
+    return [[ASCollectionLayoutState alloc] initWithContext:context];
-                                                contentSize:CGSizeZero
-                             elementToLayoutAttributesTable:[NSMapTable elementToLayoutAttributesTable]];
   }
 
-  ASDisplayNodeAssertTrue([context.layoutDelegateClass conformsToProtocol:@protocol(ASCollectionLayoutDelegate)]);
   ASCollectionLayoutState *layout = [context.layoutDelegateClass calculateLayoutWithContext:context];
   [context.layoutCache setLayout:layout forContext:context];
 

examples/ASCollectionView/Sample/ViewController.m

@@ -23,7 +23,7 @@
 
 #define ASYNC_COLLECTION_LAYOUT 0
 
-@interface ViewController () <ASCollectionDataSource, ASCollectionDelegateFlowLayout>
+@interface ViewController () <ASCollectionDataSource, ASCollectionDelegateFlowLayout, ASCollectionGalleryLayoutSizeProviding>
 
 @property (nonatomic, strong) ASCollectionNode *collectionNode;
 @property (nonatomic, strong) NSArray *data;
@@ -47,8 +47,8 @@
   [super viewDidLoad];
 
 #if ASYNC_COLLECTION_LAYOUT
-  id<ASCollectionLayoutDelegate> layoutDelegate = [[ASCollectionGalleryLayoutDelegate alloc] initWithScrollableDirections:ASScrollDirectionVerticalDirections
+  ASCollectionGalleryLayoutDelegate *layoutDelegate = [[ASCollectionGalleryLayoutDelegate alloc] initWithScrollableDirections:ASScrollDirectionVerticalDirections];
-                                                                                                                 itemSize:CGSizeMake(180, 90)];
+  layoutDelegate.sizeProvider = self;
   self.collectionNode = [[ASCollectionNode alloc] initWithLayoutDelegate:layoutDelegate layoutFacilitator:nil];
 #else
   UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];
@@ -108,6 +108,14 @@
   [self.collectionNode reloadData];
 }
 
+#pragma mark - ASCollectionGalleryLayoutSizeProviding
+
+- (CGSize)sizeForElements:(ASElementMap *)elements
+{
+  ASDisplayNodeAssertMainThread();
+  return CGSizeMake(180, 90);
+}
+
 #pragma mark - ASCollectionView Data Source
 
 - (ASCellNodeBlock)collectionNode:(ASCollectionNode *)collectionNode nodeBlockForItemAtIndexPath:(NSIndexPath *)indexPath;

examples/CustomCollectionView/Sample/MosaicCollectionLayoutDelegate.m

@@ -36,11 +36,13 @@
 
 - (ASScrollDirection)scrollableDirections
 {
+  ASDisplayNodeAssertMainThread();
   return ASScrollDirectionVerticalDirections;
 }
 
 - (id)additionalInfoForLayoutWithElements:(ASElementMap *)elements
 {
+  ASDisplayNodeAssertMainThread();
   return _info;
 }