CHTCollectionViewWaterfallLayout
================================

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**CHTCollectionViewWaterfallLayout** is a subclass of [UICollectionViewLayout], and it trys to imitate [UICollectionViewFlowLayout]'s usage as much as possible.

This layout is inspired by [Pinterest].

Screen Shots
------------
![2 columns](https://cloud.githubusercontent.com/assets/474/3419095/25b4de9e-fe56-11e3-9b98-690319d736ce.png)

Features
--------
* Easy to use, it tries to imitate [UICollectionViewFlowLayout]'s usage as much as possible.
* Highly customizable.
* Outstanding performance, try 10,000+ items and see the smoothness for yourself.
* Support header and footer views.
* Different column counts in different sections.

Requirements
------------
* iOS 9+ / tvOS 9+
* Objective-C or Swift 4.2

How to install
--------------
* [CocoaPods]
  - Add `pod 'CHTCollectionViewWaterfallLayout'` to your Podfile.
  - If you prefer Objective-C, `pod 'CHTCollectionViewWaterfallLayout/ObjC'` is ready for you.

* [Carthage]
  - Add `github chiahsien/CHTCollectionViewWaterfallLayout` to your Cartfile.

* [Swift Package Manager]
  - Add it to the `dependencies` value of your `Package.swift`.
  ```
  dependencies: [
    .package(url: "https://github.com/chiahsien/CHTCollectionViewWaterfallLayout.git", from: "0.9.9")
  ]
  ```

* Manual
  - Copy `CHTCollectionViewWaterfallLayout.h/m` or `CHTCollectionViewWaterfallLayout.swift` to your project.

How to Use
----------
Read the demo codes and `CHTCollectionViewWaterfallLayout.h` header file for more information.

#### Step 1
Below lists the properties for you to customize the layout. Although they have default values, I strongly recommend you to set up at least the `columnCount` property to suit your needs.
The `itemRenderDirection` property is an enum which decides the order in which your items will be rendered in subsequent rows. For eg. Left-Right | Right-Left | Shortest column filling up first.

``` objc
@property (nonatomic, assign) NSInteger columnCount;
@property (nonatomic, assign) CGFloat minimumColumnSpacing;
@property (nonatomic, assign) CGFloat minimumInteritemSpacing;
@property (nonatomic, assign) CGFloat headerHeight;
@property (nonatomic, assign) CGFloat footerHeight;
@property (nonatomic, assign) UIEdgeInsets sectionInset;
@property (nonatomic, assign) ItemRenderDirection itemRenderDirection;
```

#### Step 2
Your collection view's delegate (which often is your view controller) must conforms to `CHTCollectionViewDelegateWaterfallLayout` protocol and implements the required method, all you need to do is return the original size of the item:

``` objc
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath;
```

Limitation
----------
* Only vertical scrolling is supported.
* No decoration view.

Who is using it
---------------
Please let me know if your app is using this library. I'm glad to put your app on the list :-)

* [F3PiX](https://itunes.apple.com/us/app/samenwerken-f3pix/id897714553?mt=8)
F3PiX is a series of apps which gives you a concise, curated collection of pictures by professional (Dutch) photographers according to a specific theme. You can use the pictures freely for your own work.
* [GroupMe for iOS](https://itunes.apple.com/us/app/groupme/id392796698?mt=8)
GroupMe - A Home for All the Groups in Your Life.
* [Flickr](https://itunes.apple.com/us/app/id328407587)
Access and organize your photos from anywhere.
* [Tumblr](https://www.tumblr.com/policy/en/ios-credits)
Post whatever you want to your Tumblr. Follow other people who are doing the same. You’ll probably never be bored again.
* [Funliday](https://itunes.apple.com/us/app/funlidays-lu-you-gui-hua/id905768387)
The best trip planning app in the world!
* [Imgur](https://itunes.apple.com/us/app/imgur-funny-gifs-memes-images/id639881495?mt=8)
Funny GIFs, Memes, and Images!
* [DealPad](https://itunes.apple.com/us/app/dealpad-bargains-freebies/id949294107?mt=8)
DealPad gives you access to the UK’s hottest Deals, Voucher Codes and Freebies in the palm of your hand.
* [Teespring Shopping](https://itunes.apple.com/app/apple-store/id1144693237?pt=117854047&ct=CHTCollectionViewWaterfallLayout%20README&mt=8)
Browse and purchase shirts, mugs, totes and more!

License
-------
CHTCollectionViewWaterfallLayout is available under the MIT license. See the LICENSE file for more info.

Changelog
---------
Refer to the [Releases page](https://github.com/chiahsien/CHTCollectionViewWaterfallLayout/releases).

[UICollectionViewLayout]: http://developer.apple.com/library/ios/#documentation/uikit/reference/UICollectionViewLayout_class/Reference/Reference.html
[UICollectionViewFlowLayout]: https://developer.apple.com/library/ios/documentation/uikit/reference/UICollectionViewFlowLayout_class/Reference/Reference.html
[Pinterest]: http://pinterest.com/
[CocoaPods]: http://cocoapods.org/
[Carthage]: https://github.com/Carthage/Carthage
[Swift Package Manager]: https://swift.org/package-manager/