/*

    Copyright (C) 2015 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    This is the "SlideLayout" class implementation.

*/

#import "AAPLSlideLayout.h"

#import "AAPLSlideCarrierView.h"    // for SLIDE_WIDTH, SLIDE_HEGIHT

@implementation AAPLSlideLayout

- (instancetype)init {

    self = [super init];

    if (self) {

        itemSize = NSMakeSize(SLIDE_WIDTH, SLIDE_HEIGHT);

    }

    return self;

}

- (NSSize)collectionViewContentSize {

    NSRect clipBounds = [[[self collectionView] superview] bounds];

    return clipBounds.size; // Lay our slides out within the available area.

}

- (BOOL)shouldInvalidateLayoutForBoundsChange:(NSRect)newBounds {

    return YES; // Our custom SlideLayouts show all items within the CollectionView's visible rect, and must recompute their layouts for a good fit when that rect changes.

}

- (void)prepareLayout {

    [super prepareLayout];

    // Inset by (X_PADDING,Y_PADDING) to precompute the box we need to fix the slides in.

    CGSize collectionViewContentSize = [self collectionViewContentSize];

    box = NSInsetRect(NSMakeRect(0, 0, collectionViewContentSize.width, collectionViewContentSize.height), X_PADDING, Y_PADDING);

}

// A layout derived from this base class always displays all items, within the visible rectangle.  So we can implement -layoutAttributesForElementsInRect: quite simply, by enumerating all item index paths and obtaining the -layoutAttributesForItemAtIndexPath: for each.  Our subclasses then just have to implement -layoutAttributesForItemAtIndexPath:.

- (NSArray *)layoutAttributesForElementsInRect:(NSRect)rect {

    NSInteger itemCount = [[self collectionView] numberOfItemsInSection:0];

    NSMutableArray *layoutAttributesArray = [NSMutableArray arrayWithCapacity:itemCount];

    for (NSInteger index = 0; index < itemCount; index++) {

        NSIndexPath *indexPath = [NSIndexPath indexPathForItem:index inSection:0];

        NSCollectionViewLayoutAttributes *layoutAttributes = [self layoutAttributesForItemAtIndexPath:indexPath];

        if (layoutAttributes) {

            [layoutAttributesArray addObject:layoutAttributes];

        }

    }

    return layoutAttributesArray;

}

@end