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87 lines
3.0 KiB
Plaintext
87 lines
3.0 KiB
Plaintext
//
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// ASCollectionViewLayoutController.mm
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// AsyncDisplayKit
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//
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// Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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#import <AsyncDisplayKit/ASCollectionViewLayoutController.h>
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#import <AsyncDisplayKit/ASAssert.h>
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#import <AsyncDisplayKit/ASCollectionView.h>
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#import <AsyncDisplayKit/CoreGraphics+ASConvenience.h>
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#import <AsyncDisplayKit/UICollectionViewLayout+ASConvenience.h>
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struct ASRangeGeometry {
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CGRect rangeBounds;
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CGRect updateBounds;
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};
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typedef struct ASRangeGeometry ASRangeGeometry;
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#pragma mark -
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#pragma mark ASCollectionViewLayoutController
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@interface ASCollectionViewLayoutController ()
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{
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@package
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ASCollectionView * __weak _collectionView;
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UICollectionViewLayout * __strong _collectionViewLayout;
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}
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@end
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@implementation ASCollectionViewLayoutController
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- (instancetype)initWithCollectionView:(ASCollectionView *)collectionView
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{
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if (!(self = [super init])) {
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return nil;
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}
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_collectionView = collectionView;
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_collectionViewLayout = [collectionView collectionViewLayout];
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return self;
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}
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- (NSSet *)indexPathsForScrolling:(ASScrollDirection)scrollDirection rangeMode:(ASLayoutRangeMode)rangeMode rangeType:(ASLayoutRangeType)rangeType
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{
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ASRangeTuningParameters tuningParameters = [self tuningParametersForRangeMode:rangeMode rangeType:rangeType];
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CGRect rangeBounds = [self rangeBoundsWithScrollDirection:scrollDirection rangeTuningParameters:tuningParameters];
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return [self indexPathsForItemsWithinRangeBounds:rangeBounds];
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}
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- (NSSet *)indexPathsForItemsWithinRangeBounds:(CGRect)rangeBounds
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{
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NSArray *layoutAttributes = [_collectionViewLayout layoutAttributesForElementsInRect:rangeBounds];
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NSMutableSet *indexPathSet = [NSMutableSet setWithCapacity:layoutAttributes.count];
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for (UICollectionViewLayoutAttributes *la in layoutAttributes) {
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//ASDisplayNodeAssert(![indexPathSet containsObject:la.indexPath], @"Shouldn't already contain indexPath");
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// Manually filter out elements that don't intersect the range bounds.
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// If a layout returns elements outside the requested rect this can be a huge problem.
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// For instance in a paging flow, you may only want to preload 3 pages (one center, one on each side)
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// but if flow layout includes the 4th page (which it does! as of iOS 9&10), you will preload a 4th
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// page as well.
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if (CATransform3DIsIdentity(la.transform3D) && CGRectIntersectsRect(la.frame, rangeBounds) == NO) {
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continue;
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}
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[indexPathSet addObject:la.indexPath];
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}
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return indexPathSet;
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}
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- (CGRect)rangeBoundsWithScrollDirection:(ASScrollDirection)scrollDirection
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rangeTuningParameters:(ASRangeTuningParameters)tuningParameters
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{
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CGRect rect = _collectionView.bounds;
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return CGRectExpandToRangeWithScrollableDirections(rect, tuningParameters, [_collectionView scrollableDirections], scrollDirection);
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}
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@end
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