From 5eb75d6bc79390c9b2f650bd6e40b68e92394185 Mon Sep 17 00:00:00 2001
From: Levi McCallum <levi.mccallum@nfl.com>
Date: Mon, 3 Aug 2015 14:36:29 -0700
Subject: [PATCH] Add support for sectionInset in ASCollectionView in property
 and delegate form

---
 AsyncDisplayKit/ASCollectionView.h                | 13 +++++++++++++
 AsyncDisplayKit/ASCollectionView.mm               | 12 ++++++++++--
 examples/ASCollectionView/Sample/ViewController.m |  4 ++++
 3 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/AsyncDisplayKit/ASCollectionView.h b/AsyncDisplayKit/ASCollectionView.h
index a47765bbfa..7af28f96e3 100644
--- a/AsyncDisplayKit/ASCollectionView.h
+++ b/AsyncDisplayKit/ASCollectionView.h
@@ -320,6 +320,19 @@
  */
 - (BOOL)shouldBatchFetchForCollectionView:(ASCollectionView *)collectionView;
 
+/**
+ * Passthrough support to UICollectionViewDelegateFlowLayout sectionInset behavior.
+ *
+ * @param collectionView The sender.
+ * @param collectionViewLayout The layout object requesting the information.
+ * #param section The index number of the section whose insets are needed.
+ *
+ * @discussion The same rules apply as the UICollectionView implementation, but this can also be used without a UICollectionViewFlowLayout.
+ * https://developer.apple.com/library/ios/documentation/UIKit/Reference/UICollectionViewDelegateFlowLayout_protocol/index.html#//apple_ref/occ/intfm/UICollectionViewDelegateFlowLayout/collectionView:layout:insetForSectionAtIndex:
+ *
+ */
+- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section;
+
 @end
 
 @interface ASCollectionView (Deprecated)
diff --git a/AsyncDisplayKit/ASCollectionView.mm b/AsyncDisplayKit/ASCollectionView.mm
index e13c0d5167..b5b132dca8 100644
--- a/AsyncDisplayKit/ASCollectionView.mm
+++ b/AsyncDisplayKit/ASCollectionView.mm
@@ -118,6 +118,7 @@ static BOOL _isInterceptedSelector(SEL sel)
   NSMutableArray *_batchUpdateBlocks;
 
   BOOL _asyncDataFetchingEnabled;
+  BOOL _implementsInsetSection;
 
   ASBatchContext *_batchContext;
 }
@@ -164,6 +165,8 @@ static BOOL _isInterceptedSelector(SEL sel)
 
   _performingBatchUpdates = NO;
   _batchUpdateBlocks = [NSMutableArray array];
+  
+  _implementsInsetSection = ([_asyncDelegate respondsToSelector:@selector(collectionView:layout:insetForSectionAtIndex:)] ? 1 : 0);
 
   [self registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"_ASCollectionViewCell"];
   
@@ -511,11 +514,16 @@ static BOOL _isInterceptedSelector(SEL sel)
 - (CGSize)dataController:(ASDataController *)dataController constrainedSizeForNodeAtIndexPath:(NSIndexPath *)indexPath
 {
   CGSize restrainedSize = self.bounds.size;
+  UIEdgeInsets sectionInset = [(UICollectionViewFlowLayout *)self.collectionViewLayout sectionInset];
+  
+  if (_implementsInsetSection) {
+    sectionInset = [_asyncDelegate collectionView:self layout:self.collectionViewLayout insetForSectionAtIndex:indexPath.section];
+  }
 
   if (ASScrollDirectionContainsHorizontalDirection([self scrollableDirections])) {
-    restrainedSize.width = FLT_MAX;
+    restrainedSize.width = MAX(0, FLT_MAX - sectionInset.left - sectionInset.right);
   } else {
-    restrainedSize.height = FLT_MAX;
+    restrainedSize.height = MAX(0, FLT_MAX - sectionInset.top - sectionInset.bottom);
   }
 
   return restrainedSize;
diff --git a/examples/ASCollectionView/Sample/ViewController.m b/examples/ASCollectionView/Sample/ViewController.m
index 5e2ab4292a..f87e26f9d7 100644
--- a/examples/ASCollectionView/Sample/ViewController.m
+++ b/examples/ASCollectionView/Sample/ViewController.m
@@ -95,4 +95,8 @@
   [context completeBatchFetching:YES];
 }
 
+- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section {
+  return UIEdgeInsetsMake(20.0, 20.0, 20.0, 20.0);
+}
+
 @end