Initial Work for Range Controller to Support Supplementary Elements (#3140)

* Initial work supporting supplementaries in range controller * Rename indexPathForElementIfItem
2026-01-01 02:40:27 +00:00 · 2017-03-06 10:11:00 -08:00
parent d0ad24808b
commit d59ea3902d
12 changed files with 172 additions and 69 deletions
--- a/Source/Details/ASCollectionViewLayoutController.m
+++ b/Source/Details/ASCollectionViewLayoutController.m
@@ -0,0 +1,129 @@
+//
+//  ASCollectionViewLayoutController.mm
+//  AsyncDisplayKit
+//
+//  Copyright (c) 2014-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under the BSD-style license found in the
+//  LICENSE file in the root directory of this source tree. An additional grant
+//  of patent rights can be found in the PATENTS file in the same directory.
+//
+
+#import <AsyncDisplayKit/ASCollectionViewLayoutController.h>
+
+#import <AsyncDisplayKit/ASAssert.h>
+#import <AsyncDisplayKit/ASCollectionView.h>
+#import <AsyncDisplayKit/ASElementMap.h>
+#import <AsyncDisplayKit/CoreGraphics+ASConvenience.h>
+#import <AsyncDisplayKit/UICollectionViewLayout+ASConvenience.h>
+
+struct ASRangeGeometry {
+  CGRect rangeBounds;
+  CGRect updateBounds;
+};
+typedef struct ASRangeGeometry ASRangeGeometry;
+
+
+#pragma mark -
+#pragma mark ASCollectionViewLayoutController
+
+@interface ASCollectionViewLayoutController ()
+{
+  @package
+  ASCollectionView * __weak _collectionView;
+  UICollectionViewLayout * __strong _collectionViewLayout;
+}
+@end
+
+@implementation ASCollectionViewLayoutController
+
+- (instancetype)initWithCollectionView:(ASCollectionView *)collectionView
+{
+  if (!(self = [super init])) {
+    return nil;
+  }
+  
+  _collectionView = collectionView;
+  _collectionViewLayout = [collectionView collectionViewLayout];
+  return self;
+}
+
+- (NSSet<ASCollectionElement *> *)elementsForScrolling:(ASScrollDirection)scrollDirection rangeMode:(ASLayoutRangeMode)rangeMode rangeType:(ASLayoutRangeType)rangeType map:(ASElementMap *)map
+{
+  ASRangeTuningParameters tuningParameters = [self tuningParametersForRangeMode:rangeMode rangeType:rangeType];
+  CGRect rangeBounds = [self rangeBoundsWithScrollDirection:scrollDirection rangeTuningParameters:tuningParameters];
+  return [self elementsWithinRangeBounds:rangeBounds map:map];
+}
+
+- (void)allElementsForScrolling:(ASScrollDirection)scrollDirection rangeMode:(ASLayoutRangeMode)rangeMode displaySet:(NSSet<ASCollectionElement *> *__autoreleasing  _Nullable *)displaySet preloadSet:(NSSet<ASCollectionElement *> *__autoreleasing  _Nullable *)preloadSet map:(ASElementMap *)map
+{
+  if (displaySet == NULL || preloadSet == NULL) {
+    return;
+  }
+  
+  ASRangeTuningParameters displayParams = [self tuningParametersForRangeMode:rangeMode rangeType:ASLayoutRangeTypeDisplay];
+  ASRangeTuningParameters preloadParams = [self tuningParametersForRangeMode:rangeMode rangeType:ASLayoutRangeTypePreload];
+  CGRect displayBounds = [self rangeBoundsWithScrollDirection:scrollDirection rangeTuningParameters:displayParams];
+  CGRect preloadBounds = [self rangeBoundsWithScrollDirection:scrollDirection rangeTuningParameters:preloadParams];
+  
+  CGRect unionBounds = CGRectUnion(displayBounds, preloadBounds);
+  NSArray *layoutAttributes = [_collectionViewLayout layoutAttributesForElementsInRect:unionBounds];
+
+  NSMutableSet<ASCollectionElement *> *display = [NSMutableSet setWithCapacity:layoutAttributes.count];
+  NSMutableSet<ASCollectionElement *> *preload = [NSMutableSet setWithCapacity:layoutAttributes.count];
+
+  for (UICollectionViewLayoutAttributes *la in layoutAttributes) {
+    // Manually filter out elements that don't intersect the range bounds.
+    // See comment in elementsForItemsWithinRangeBounds:
+    // This is re-implemented here so that the iteration over layoutAttributes can be done once to check both ranges.
+    CGRect frame = la.frame;
+    BOOL intersectsDisplay = CGRectIntersectsRect(displayBounds, frame);
+    BOOL intersectsPreload = CGRectIntersectsRect(preloadBounds, frame);
+    if (intersectsDisplay == NO && intersectsPreload == NO && CATransform3DIsIdentity(la.transform3D) == YES) {
+      // Questionable why the element would be included here, but it doesn't belong.
+      continue;
+    }
+    
+    // Avoid excessive retains and releases, as well as property calls. We know the element is kept alive by map.
+    __unsafe_unretained ASCollectionElement *e = [map elementForLayoutAttributes:la];
+    if (intersectsDisplay) {
+      [display addObject:e];
+    }
+    if (intersectsPreload) {
+      [preload addObject:e];
+    }
+  }
+
+  *displaySet = display;
+  *preloadSet = preload;
+  return;
+}
+
+- (NSSet<ASCollectionElement *> *)elementsWithinRangeBounds:(CGRect)rangeBounds map:(ASElementMap *)map
+{
+  NSArray *layoutAttributes = [_collectionViewLayout layoutAttributesForElementsInRect:rangeBounds];
+  NSMutableSet<ASCollectionElement *> *elementSet = [NSMutableSet setWithCapacity:layoutAttributes.count];
+  
+  for (UICollectionViewLayoutAttributes *la in layoutAttributes) {
+    // Manually filter out elements that don't intersect the range bounds.
+    // If a layout returns elements outside the requested rect this can be a huge problem.
+    // For instance in a paging flow, you may only want to preload 3 pages (one center, one on each side)
+    // but if flow layout includes the 4th page (which it does! as of iOS 9&10), you will preload a 4th
+    // page as well.
+    if (CATransform3DIsIdentity(la.transform3D) && CGRectIntersectsRect(la.frame, rangeBounds) == NO) {
+      continue;
+    }
+    [elementSet addObject:[map elementForLayoutAttributes:la]];
+  }
+
+  return elementSet;
+}
+
+- (CGRect)rangeBoundsWithScrollDirection:(ASScrollDirection)scrollDirection
+                   rangeTuningParameters:(ASRangeTuningParameters)tuningParameters
+{
+  CGRect rect = _collectionView.bounds;
+  
+  return CGRectExpandToRangeWithScrollableDirections(rect, tuningParameters, [_collectionView scrollableDirections], scrollDirection);
+}
+
+@end