Add custom collection view layout example project

examples/CustomCollectionView/Sample/AppDelegate.h

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+/* This file provided by Facebook is for non-commercial testing and evaluation
+ * purposes only.  Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#import <UIKit/UIKit.h>
+
+@interface AppDelegate : UIResponder <UIApplicationDelegate>
+
+@property (strong, nonatomic) UIWindow *window;
+
+@end

examples/CustomCollectionView/Sample/AppDelegate.m

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+/* This file provided by Facebook is for non-commercial testing and evaluation
+ * purposes only.  Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#import "AppDelegate.h"
+
+#import "ViewController.h"
+
+@implementation AppDelegate
+
+- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
+{
+  self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
+  self.window.backgroundColor = [UIColor whiteColor];
+  self.window.rootViewController = [[ViewController alloc] init];
+  
+  [self.window makeKeyAndVisible];
+  
+  return YES;
+}
+
+@end

examples/CustomCollectionView/Sample/ImageCellNode.h

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+//
+//  ImageCellNode.h
+//  Sample
+//
+//  Created by McCallum, Levi on 11/22/15.
+//  Copyright (c) 2015 Facebook. All rights reserved.
+//
+
+#import <AsyncDisplayKit/AsyncDisplayKit.h>
+
+@interface ImageCellNode : ASCellNode
+
+- (instancetype)initWithImage:(UIImage *)image;
+
+@end

examples/CustomCollectionView/Sample/ImageCellNode.m

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+//
+//  ImageCellNode.m
+//  Sample
+//
+//  Created by McCallum, Levi on 11/22/15.
+//  Copyright (c) 2015 Facebook. All rights reserved.
+//
+
+#import "ImageCellNode.h"
+
+@implementation ImageCellNode {
+  ASImageNode *_imageNode;
+}
+
+- (id)initWithImage:(UIImage *)image
+{
+  self = [super init];
+  if (self != nil) {
+    _imageNode = [[ASImageNode alloc] init];
+    _imageNode.image = image;
+    [self addSubnode:_imageNode];
+  }
+  return self;
+}
+
+- (CGSize)calculateSizeThatFits:(CGSize)constrainedSize
+{
+  [_imageNode measure:constrainedSize];
+  return constrainedSize;
+}
+
+- (void)layout
+{
+  _imageNode.frame = CGRectMake(0, 0, _imageNode.calculatedSize.width, _imageNode.calculatedSize.height);
+}
+
+@end

examples/CustomCollectionView/Sample/Images.xcassets/LaunchImage.launchimage/Contents.json

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+{
+  "images" : [
+    {
+      "orientation" : "portrait",
+      "idiom" : "iphone",
+      "filename" : "Default-568h@2x.png",
+      "minimum-system-version" : "7.0",
+      "subtype" : "retina4",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "iphone",
+      "scale" : "1x",
+      "orientation" : "portrait"
+    },
+    {
+      "idiom" : "iphone",
+      "scale" : "2x",
+      "orientation" : "portrait"
+    },
+    {
+      "orientation" : "portrait",
+      "idiom" : "iphone",
+      "filename" : "Default-568h@2x.png",
+      "subtype" : "retina4",
+      "scale" : "2x"
+    },
+    {
+      "orientation" : "portrait",
+      "idiom" : "iphone",
+      "minimum-system-version" : "7.0",
+      "scale" : "2x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

examples/CustomCollectionView/Sample/Images.xcassets/image_0.imageset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x",
+      "filename" : "image_0.jpg"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

examples/CustomCollectionView/Sample/Images.xcassets/image_1.imageset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x",
+      "filename" : "image_1.jpg"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

examples/CustomCollectionView/Sample/Images.xcassets/image_10.imageset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x",
+      "filename" : "image_10.jpg"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

examples/CustomCollectionView/Sample/Images.xcassets/image_11.imageset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x",
+      "filename" : "image_11.jpg"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

examples/CustomCollectionView/Sample/Images.xcassets/image_12.imageset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x",
+      "filename" : "image_12.jpg"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

examples/CustomCollectionView/Sample/Images.xcassets/image_13.imageset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x",
+      "filename" : "image_13.jpg"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

examples/CustomCollectionView/Sample/Images.xcassets/image_2.imageset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x",
+      "filename" : "image_2.jpg"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

examples/CustomCollectionView/Sample/Images.xcassets/image_3.imageset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x",
+      "filename" : "image_3.jpg"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

examples/CustomCollectionView/Sample/Images.xcassets/image_4.imageset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x",
+      "filename" : "image_4.jpg"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

examples/CustomCollectionView/Sample/Images.xcassets/image_5.imageset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x",
+      "filename" : "image_5.jpg"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

examples/CustomCollectionView/Sample/Images.xcassets/image_6.imageset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x",
+      "filename" : "image_6.jpg"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

examples/CustomCollectionView/Sample/Images.xcassets/image_7.imageset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x",
+      "filename" : "image_7.jpg"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

examples/CustomCollectionView/Sample/Images.xcassets/image_8.imageset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x",
+      "filename" : "image_8.jpg"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

examples/CustomCollectionView/Sample/Images.xcassets/image_9.imageset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x",
+      "filename" : "image_9.jpg"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

examples/CustomCollectionView/Sample/Info.plist

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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleDevelopmentRegion</key>
+	<string>en</string>
+	<key>CFBundleExecutable</key>
+	<string>$(EXECUTABLE_NAME)</string>
+	<key>CFBundleIcons</key>
+	<dict/>
+	<key>CFBundleIcons~ipad</key>
+	<dict/>
+	<key>CFBundleIdentifier</key>
+	<string>com.facebook.AsyncDisplayKit.$(PRODUCT_NAME:rfc1034identifier)</string>
+	<key>CFBundleInfoDictionaryVersion</key>
+	<string>6.0</string>
+	<key>CFBundleName</key>
+	<string>$(PRODUCT_NAME)</string>
+	<key>CFBundlePackageType</key>
+	<string>APPL</string>
+	<key>CFBundleShortVersionString</key>
+	<string>1.0</string>
+	<key>CFBundleSignature</key>
+	<string>????</string>
+	<key>CFBundleVersion</key>
+	<string>1</string>
+	<key>LSRequiresIPhoneOS</key>
+	<true/>
+	<key>UILaunchStoryboardName</key>
+	<string>Launchboard</string>
+	<key>UIRequiredDeviceCapabilities</key>
+	<array>
+		<string>armv7</string>
+	</array>
+	<key>UISupportedInterfaceOrientations</key>
+	<array>
+		<string>UIInterfaceOrientationPortrait</string>
+		<string>UIInterfaceOrientationLandscapeLeft</string>
+		<string>UIInterfaceOrientationLandscapeRight</string>
+	</array>
+	<key>UISupportedInterfaceOrientations~ipad</key>
+	<array>
+		<string>UIInterfaceOrientationPortrait</string>
+		<string>UIInterfaceOrientationPortraitUpsideDown</string>
+		<string>UIInterfaceOrientationLandscapeLeft</string>
+		<string>UIInterfaceOrientationLandscapeRight</string>
+	</array>
+</dict>
+</plist>

examples/CustomCollectionView/Sample/Launchboard.storyboard

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+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="6211" systemVersion="14A298i" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES">
+    <dependencies>
+        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="6204"/>
+    </dependencies>
+    <scenes/>
+</document>

examples/CustomCollectionView/Sample/MosaicCollectionViewLayout.h

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+//
+//  MosaicCollectionViewLayout.h
+//  Sample
+//
+//  Created by McCallum, Levi on 11/22/15.
+//  Copyright (c) 2015 Facebook. All rights reserved.
+//
+
+#import <UIKit/UIKit.h>
+#import <AsyncDisplayKit/AsyncDisplayKit.h>
+
+@interface MosaicCollectionViewLayout : UICollectionViewLayout
+
+@property (assign, nonatomic) NSUInteger numberOfColumns;
+@property (assign, nonatomic) CGFloat columnSpacing;
+@property (assign, nonatomic) UIEdgeInsets sectionInset;
+@property (assign, nonatomic) UIEdgeInsets interItemSpacing;
+@property (assign, nonatomic) CGFloat headerHeight;
+
+@end
+
+@protocol MosaicCollectionViewLayoutDelegate <ASCollectionViewDelegate>
+
+- (CGSize)collectionView:(UICollectionView *)collectionView layout:(MosaicCollectionViewLayout *)layout originalItemSizeAtIndexPath:(NSIndexPath *)indexPath;
+
+@end
+
+@interface MosaicCollectionViewLayoutInspector : NSObject <ASCollectionViewLayoutInspecting>
+
+@end

examples/CustomCollectionView/Sample/MosaicCollectionViewLayout.m

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+//
+//  MosaicCollectionViewLayout.m
+//  Sample
+//
+//  Created by McCallum, Levi on 11/22/15.
+//  Copyright (c) 2015 Facebook. All rights reserved.
+//
+
+#import "MosaicCollectionViewLayout.h"
+
+@implementation MosaicCollectionViewLayout {
+  NSMutableArray *_columnHeights;
+  NSMutableArray *_itemAttributes;
+  NSMutableDictionary *_headerAttributes;
+  NSMutableArray *_allAttributes;
+}
+
+- (instancetype)init
+{
+  self = [super init];
+  if (self != nil) {
+    self.numberOfColumns = 3;
+    self.columnSpacing = 10.0;
+    self.sectionInset = UIEdgeInsetsMake(10.0, 10.0, 10.0, 10.0);
+    self.interItemSpacing = UIEdgeInsetsMake(10.0, 0, 10.0, 0);
+  }
+  return self;
+}
+
+- (void)prepareLayout
+{
+  _itemAttributes = [NSMutableArray array];
+  _columnHeights = [NSMutableArray array];
+  _allAttributes = [NSMutableArray array];
+  _headerAttributes = [NSMutableDictionary dictionary];
+  
+  CGFloat top = 0;
+  
+  NSInteger numberOfSections = [self.collectionView numberOfSections];
+  for (NSUInteger section = 0; section < numberOfSections; section++) {
+    NSInteger numberOfItems = [self.collectionView numberOfItemsInSection:section];
+    
+    top += _sectionInset.top;
+    
+    if (_headerHeight > 0) {
+      CGSize headerSize = [self _headerSizeForSection:section];
+      UICollectionViewLayoutAttributes *attributes = [UICollectionViewLayoutAttributes
+                                                      layoutAttributesForSupplementaryViewOfKind:UICollectionElementKindSectionHeader
+                                                      withIndexPath:[NSIndexPath indexPathForItem:0 inSection:section]];
+      attributes.frame = CGRectMake(_sectionInset.left, top, headerSize.width, headerSize.height);
+      _headerAttributes[@(section)] = attributes;
+      [_allAttributes addObject:attributes];
+      top = CGRectGetMaxY(attributes.frame);
+    }
+    
+    [_columnHeights addObject:[NSMutableArray array]];
+    for (NSUInteger idx = 0; idx < self.numberOfColumns; idx++) {
+      [_columnHeights[section] addObject:@(top)];
+    }
+    
+    CGFloat columnWidth = [self _columnWidthForSection:section];
+    [_itemAttributes addObject:[NSMutableArray array]];
+    for (NSUInteger idx = 0; idx < numberOfItems; idx++) {
+      NSUInteger columnIndex = [self _shortestColumnIndexInSection:section];
+      NSIndexPath *indexPath = [NSIndexPath indexPathForItem:idx inSection:section];
+      
+      CGSize itemSize = [self _itemSizeAtIndexPath:indexPath];
+      CGFloat xOffset = _sectionInset.left + (columnWidth + _columnSpacing) * columnIndex;
+      CGFloat yOffset = [_columnHeights[section][columnIndex] floatValue];
+      
+      UICollectionViewLayoutAttributes *attributes = [UICollectionViewLayoutAttributes
+                                                      layoutAttributesForCellWithIndexPath:indexPath];
+      attributes.frame = CGRectMake(xOffset, yOffset, itemSize.width, itemSize.height);
+      
+      _columnHeights[section][columnIndex] = @(CGRectGetMaxY(attributes.frame) + _interItemSpacing.bottom);
+      
+      [_itemAttributes[section] addObject:attributes];
+      [_allAttributes addObject:attributes];
+    }
+    
+    NSUInteger columnIndex = [self _tallestColumnIndexInSection:section];
+    top = [_columnHeights[section][columnIndex] floatValue] - _interItemSpacing.bottom + _sectionInset.bottom;
+    
+    for (NSUInteger idx = 0; idx < [_columnHeights[section] count]; idx++) {
+      _columnHeights[section][idx] = @(top);
+    }
+  }
+}
+
+- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
+{
+  NSMutableArray *includedAttributes = [NSMutableArray array];
+  // Slow search for small batches
+  for (UICollectionViewLayoutAttributes *attributes in _allAttributes) {
+    if (CGRectIntersectsRect(attributes.frame, rect)) {
+      [includedAttributes addObject:attributes];
+    }
+  }
+  return includedAttributes;
+}
+
+- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
+{
+  if (indexPath.section >= _itemAttributes.count) {
+    return nil;
+  } else if (indexPath.item >= [_itemAttributes[indexPath.section] count]) {
+    return nil;
+  }
+  return _itemAttributes[indexPath.section][indexPath.item];
+}
+
+- (UICollectionViewLayoutAttributes *)layoutAttributesForSupplementaryViewOfKind:(NSString *)elementKind atIndexPath:(NSIndexPath *)indexPath
+{
+  if ([elementKind isEqualToString:UICollectionElementKindSectionHeader]) {
+    return _headerAttributes[@(indexPath.section)];
+  }
+  return nil;
+}
+
+- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds
+{
+  if (!CGRectEqualToRect(self.collectionView.bounds, newBounds)) {
+    return YES;
+  }
+  return NO;
+}
+
+- (CGFloat)_widthForSection:(NSUInteger)section
+{
+  return self.collectionView.bounds.size.width - _sectionInset.left - _sectionInset.right;
+}
+
+- (CGFloat)_columnWidthForSection:(NSUInteger)section
+{
+  return ([self _widthForSection:section] - ((_numberOfColumns - 1) * _columnSpacing)) / _numberOfColumns;
+}
+
+- (CGSize)_itemSizeAtIndexPath:(NSIndexPath *)indexPath
+{
+  CGSize size = CGSizeMake([self _columnWidthForSection:indexPath.section], 0);
+  CGSize originalSize = [[self _delegate] collectionView:self.collectionView layout:self originalItemSizeAtIndexPath:indexPath];
+  if (originalSize.height > 0 && originalSize.width > 0) {
+    size.height = originalSize.height / originalSize.width * size.width;
+  }
+  return size;
+}
+
+- (CGSize)_headerSizeForSection:(NSUInteger)section
+{
+  return CGSizeMake([self _widthForSection:section], _headerHeight);
+}
+
+- (CGSize)collectionViewContentSize
+{
+  CGFloat height = [[[_columnHeights lastObject] firstObject] floatValue];
+  return CGSizeMake(self.collectionView.bounds.size.width, height);
+}
+
+- (NSUInteger)_tallestColumnIndexInSection:(NSUInteger)section
+{
+  __block NSUInteger index = 0;
+  __block CGFloat tallestHeight = 0;
+  [_columnHeights[section] enumerateObjectsUsingBlock:^(NSNumber *height, NSUInteger idx, BOOL *stop) {
+    if (height.floatValue > tallestHeight) {
+      index = idx;
+      tallestHeight = height.floatValue;
+    }
+  }];
+  return index;
+}
+
+- (NSUInteger)_shortestColumnIndexInSection:(NSUInteger)section
+{
+  __block NSUInteger index = 0;
+  __block CGFloat shortestHeight = CGFLOAT_MAX;
+  [_columnHeights[section] enumerateObjectsUsingBlock:^(NSNumber *height, NSUInteger idx, BOOL *stop) {
+    if (height.floatValue < shortestHeight) {
+      index = idx;
+      shortestHeight = height.floatValue;
+    }
+  }];
+  return index;
+}
+
+- (id<MosaicCollectionViewLayoutDelegate>)_delegate
+{
+  return (id<MosaicCollectionViewLayoutDelegate>)self.collectionView.delegate;
+}
+
+@end
+
+@implementation MosaicCollectionViewLayoutInspector
+
+- (ASSizeRange)collectionView:(ASCollectionView *)collectionView constrainedSizeForNodeAtIndexPath:(NSIndexPath *)indexPath
+{
+  MosaicCollectionViewLayout *layout = (MosaicCollectionViewLayout *)[collectionView collectionViewLayout];
+  return ASSizeRangeMake(CGSizeZero, [layout _itemSizeAtIndexPath:indexPath]);
+}
+
+- (ASSizeRange)collectionView:(ASCollectionView *)collectionView constrainedSizeForSupplementaryNodeOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
+{
+  MosaicCollectionViewLayout *layout = (MosaicCollectionViewLayout *)[collectionView collectionViewLayout];
+  return ASSizeRangeMake(CGSizeZero, [layout _headerSizeForSection:indexPath.section]);
+}
+
+/**
+ * Asks the inspector for the number of supplementary sections in the collection view for the given kind.
+ */
+- (NSUInteger)collectionView:(ASCollectionView *)collectionView numberOfSectionsForSupplementaryNodeOfKind:(NSString *)kind
+{
+  if ([kind isEqualToString:UICollectionElementKindSectionHeader]) {
+    return [[collectionView asyncDataSource] numberOfSectionsInCollectionView:collectionView];
+  } else {
+    return 0;
+  }
+}
+
+/**
+ * Asks the inspector for the number of supplementary views for the given kind in the specified section.
+ */
+- (NSUInteger)collectionView:(ASCollectionView *)collectionView supplementaryNodesOfKind:(NSString *)kind inSection:(NSUInteger)section
+{
+  if ([kind isEqualToString:UICollectionElementKindSectionHeader]) {
+    return 1;
+  } else {
+    return 0;
+  }
+}
+
+@end

examples/CustomCollectionView/Sample/SupplementaryNode.h

@@ -0,0 +1,18 @@
+/* This file provided by Facebook is for non-commercial testing and evaluation
+ * purposes only.  Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#import <AsyncDisplayKit/AsyncDisplayKit.h>
+
+@interface SupplementaryNode : ASCellNode
+
+- (instancetype)initWithText:(NSString *)text;
+
+@end

examples/CustomCollectionView/Sample/SupplementaryNode.m

@@ -0,0 +1,52 @@
+/* This file provided by Facebook is for non-commercial testing and evaluation
+ * purposes only.  Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#import "SupplementaryNode.h"
+
+#import <AsyncDisplayKit/ASDisplayNode+Subclasses.h>
+#import <AsyncDisplayKit/ASInsetLayoutSpec.h>
+#import <AsyncDisplayKit/ASCenterLayoutSpec.h>
+
+@implementation SupplementaryNode {
+  ASTextNode *_textNode;
+}
+
+- (instancetype)initWithText:(NSString *)text
+{
+  self = [super init];
+  if (self != nil) {
+    _textNode = [[ASTextNode alloc] init];
+    _textNode.attributedString = [[NSAttributedString alloc] initWithString:text
+                                                                 attributes:[self textAttributes]];
+    [self addSubnode:_textNode];
+  }
+  return self;
+}
+
+- (ASLayoutSpec *)layoutSpecThatFits:(ASSizeRange)constrainedSize
+{
+  ASCenterLayoutSpec *center = [[ASCenterLayoutSpec alloc] init];
+  center.centeringOptions = ASCenterLayoutSpecCenteringY;
+  center.child = _textNode;
+  return center;
+}
+
+#pragma mark - Text Formatting
+
+- (NSDictionary *)textAttributes
+{
+  return @{
+    NSFontAttributeName: [UIFont preferredFontForTextStyle:UIFontTextStyleHeadline],
+    NSForegroundColorAttributeName: [UIColor grayColor],
+  };
+}
+
+@end

examples/CustomCollectionView/Sample/ViewController.h

@@ -0,0 +1,16 @@
+/* This file provided by Facebook is for non-commercial testing and evaluation
+ * purposes only.  Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#import <UIKit/UIKit.h>
+
+@interface ViewController : UIViewController
+
+@end

examples/CustomCollectionView/Sample/ViewController.m

@@ -0,0 +1,117 @@
+/* This file provided by Facebook is for non-commercial testing and evaluation
+ * purposes only.  Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#import "ViewController.h"
+
+#import <AsyncDisplayKit/AsyncDisplayKit.h>
+#import "MosaicCollectionViewLayout.h"
+#import "SupplementaryNode.h"
+#import "ImageCellNode.h"
+
+static NSUInteger kNumberOfImages = 14;
+
+@interface ViewController () <ASCollectionViewDataSource, MosaicCollectionViewLayoutDelegate>
+{
+  NSMutableArray *_sections;
+  ASCollectionView *_collectionView;
+  MosaicCollectionViewLayoutInspector *_layoutInspector;
+}
+
+@end
+
+@implementation ViewController
+
+#pragma mark -
+#pragma mark UIViewController.
+
+- (instancetype)init
+{
+  if (!(self = [super init]))
+    return nil;
+  
+  _sections = [NSMutableArray array];
+  [_sections addObject:[NSMutableArray array]];
+  for (NSUInteger idx = 0, section = 0; idx < kNumberOfImages; idx++) {
+    NSString *name = [NSString stringWithFormat:@"image_%lu.jpg", (unsigned long)idx];
+    [_sections[section] addObject:[UIImage imageNamed:name]];
+    if ((idx + 1) % 5 == 0 && idx < kNumberOfImages - 1) {
+      section++;
+      [_sections addObject:[NSMutableArray array]];
+    }
+  }
+  
+  MosaicCollectionViewLayout *layout = [[MosaicCollectionViewLayout alloc] init];
+  layout.numberOfColumns = 2;
+  layout.headerHeight = 44.0;
+  
+  _layoutInspector = [[MosaicCollectionViewLayoutInspector alloc] init];
+  
+  _collectionView = [[ASCollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:layout asyncDataFetching:YES];
+  _collectionView.asyncDataSource = self;
+  _collectionView.asyncDelegate = self;
+  _collectionView.layoutInspector = _layoutInspector;
+  _collectionView.backgroundColor = [UIColor whiteColor];
+  
+  [_collectionView registerSupplementaryNodeOfKind:UICollectionElementKindSectionHeader];
+  
+  return self;
+}
+
+- (void)viewDidLoad
+{
+  [super viewDidLoad];
+  
+  [self.view addSubview:_collectionView];
+}
+
+- (void)viewWillLayoutSubviews
+{
+  _collectionView.frame = self.view.bounds;
+}
+
+- (BOOL)prefersStatusBarHidden
+{
+  return YES;
+}
+
+- (void)reloadTapped
+{
+  [_collectionView reloadData];
+}
+
+#pragma mark -
+#pragma mark ASCollectionView data source.
+
+- (ASCellNode *)collectionView:(ASCollectionView *)collectionView nodeForItemAtIndexPath:(NSIndexPath *)indexPath
+{
+  return [[ImageCellNode alloc] initWithImage:_sections[indexPath.section][indexPath.item]];
+}
+
+- (ASCellNode *)collectionView:(ASCollectionView *)collectionView nodeForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
+{
+  NSString *text = [NSString stringWithFormat:@"Section %d", (int)indexPath.section + 1];
+  return [[SupplementaryNode alloc] initWithText:text];
+}
+
+- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
+  return _sections.count;
+}
+
+- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
+  return [_sections[section] count];
+}
+
+- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout originalItemSizeAtIndexPath:(NSIndexPath *)indexPath
+{
+  return [(UIImage *)_sections[indexPath.section][indexPath.item] size];
+}
+
+@end

examples/CustomCollectionView/Sample/main.m

@@ -0,0 +1,19 @@
+/* This file provided by Facebook is for non-commercial testing and evaluation
+ * purposes only.  Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#import <UIKit/UIKit.h>
+#import "AppDelegate.h"
+
+int main(int argc, char * argv[]) {
+  @autoreleasepool {
+      return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
+  }
+}