//
//  UICollectionViewFlowLayout.h
//  UIKit
//
//  Copyright (c) 2011-2015 Apple Inc. All rights reserved.
//

#import <UIKit/UICollectionViewLayout.h>
#import <UIKit/UICollectionView.h>
#import <UIKit/UIKitDefines.h>
#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

UIKIT_EXTERN NSString *const UICollectionElementKindSectionHeader NS_AVAILABLE_IOS(6_0);
UIKIT_EXTERN NSString *const UICollectionElementKindSectionFooter NS_AVAILABLE_IOS(6_0);

typedef NS_ENUM(NSInteger, UICollectionViewScrollDirection) {
    UICollectionViewScrollDirectionVertical,
    UICollectionViewScrollDirectionHorizontal
};

NS_CLASS_AVAILABLE_IOS(7_0) @interface UICollectionViewFlowLayoutInvalidationContext : UICollectionViewLayoutInvalidationContext

@property (nonatomic) BOOL invalidateFlowLayoutDelegateMetrics; // if set to NO, flow layout will not requery the collection view delegate for size information etc.
@property (nonatomic) BOOL invalidateFlowLayoutAttributes; // if set to NO, flow layout will keep all layout information, effectively not invalidating - useful for a subclass which invalidates only a piece of itself

@end

@protocol UICollectionViewDelegateFlowLayout <UICollectionViewDelegate>
@optional

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath;
- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section;
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section;
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section;
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section;
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section;

@end

NS_CLASS_AVAILABLE_IOS(6_0) @interface UICollectionViewFlowLayout : UICollectionViewLayout

@property (nonatomic) CGFloat minimumLineSpacing;
@property (nonatomic) CGFloat minimumInteritemSpacing;
@property (nonatomic) CGSize itemSize;
@property (nonatomic) CGSize estimatedItemSize NS_AVAILABLE_IOS(8_0); // defaults to CGSizeZero - setting a non-zero size enables cells that self-size via -preferredLayoutAttributesFittingAttributes:
@property (nonatomic) UICollectionViewScrollDirection scrollDirection; // default is UICollectionViewScrollDirectionVertical
@property (nonatomic) CGSize headerReferenceSize;
@property (nonatomic) CGSize footerReferenceSize;
@property (nonatomic) UIEdgeInsets sectionInset;

// Set these properties to YES to get headers that pin to the top of the screen and footers that pin to the bottom while scrolling (similar to UITableView).
@property (nonatomic) BOOL sectionHeadersPinToVisibleBounds NS_AVAILABLE_IOS(9_0);
@property (nonatomic) BOOL sectionFootersPinToVisibleBounds NS_AVAILABLE_IOS(9_0);

@end

NS_ASSUME_NONNULL_END