Fix scrollToObject: bug when scrolling to bottom with content inset

Instagram · Sep 20, 2017 · f7faca6 · f7faca6
1 parent d322c2e
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -9,6 +9,7 @@ The changelog for `IGListKit`. Also see the [releases](https://github.com/instag
 
 - Weakly reference the `UICollectionView` in coalescence so that it can be released if the rest of system is destroyed. [Ryan Nystrom](https://github.com/rnystrom) [(#tbd)](https://github.com/Instagram/IGListKit/pull/tbd)
 
+- Fix bug with `-[IGListAdapter scrollToObject:supplementaryKinds:scrollDirection:scrollPosition:animated:]` where the content inset of the collection view was incorrectly being applied to the final offset. [Ryan Nystrom](https://github.com/rnystrom) [(#tbd)](https://github.com/Instagram/IGListKit/pull/tbd)
 
 3.1.1
 -----

diff --git a/Source/IGListAdapter.m b/Source/IGListAdapter.m
@@ -273,7 +273,7 @@ - (void)scrollToObject:(id)object
         case UICollectionViewScrollDirectionVertical: {
             switch (scrollPosition) {
                 case UICollectionViewScrollPositionBottom:
-                    contentOffset.y = offsetMax - collectionViewHeight - contentInset.top;
+                    contentOffset.y = offsetMax - collectionViewHeight;
                     break;
                 case UICollectionViewScrollPositionCenteredVertically: {
                     const CGFloat insets = (contentInset.top - contentInset.bottom) / 2.0;

diff --git a/Tests/IGListAdapterTests.m b/Tests/IGListAdapterTests.m
@@ -714,6 +714,34 @@ - (void)test_whenScrollVerticallyToItemWithPositionning {
     IGAssertEqualPoint([self.collectionView contentOffset], 0, self.collectionView.contentSize.height - self.collectionView.frame.size.height);
 }
 
+- (void)test_whenScrollVerticallyToBottom_withContentInsets_thatBottomFlushWithCollectionViewBounds {
+    self.dataSource.objects = @[@100];
+    [self.adapter reloadDataWithCompletion:nil];
+
+    // no insets
+    self.collectionView.contentInset = UIEdgeInsetsMake(0, 0, 0, 0);
+    [self.collectionView layoutIfNeeded];
+    [self.adapter scrollToObject:@100 supplementaryKinds:nil scrollDirection:UICollectionViewScrollDirectionVertical scrollPosition:UICollectionViewScrollPositionBottom animated:NO];
+    IGAssertEqualPoint([self.collectionView contentOffset], 0, 900);
+
+    // top 100
+    self.collectionView.contentInset = UIEdgeInsetsMake(100, 0, 0, 0);
+    [self.adapter scrollToObject:@100 supplementaryKinds:nil scrollDirection:UICollectionViewScrollDirectionVertical scrollPosition:UICollectionViewScrollPositionBottom animated:NO];
+    IGAssertEqualPoint([self.collectionView contentOffset], 0, 900);
+
+    // bottom 100
+    self.collectionView.contentInset = UIEdgeInsetsMake(0, 0, 100, 0);
+    [self.collectionView layoutIfNeeded];
+    [self.adapter scrollToObject:@100 supplementaryKinds:nil scrollDirection:UICollectionViewScrollDirectionVertical scrollPosition:UICollectionViewScrollPositionBottom animated:NO];
+    IGAssertEqualPoint([self.collectionView contentOffset], 0, 900);
+
+    // top 50, bottom 100
+    self.collectionView.contentInset = UIEdgeInsetsMake(50, 0, 100, 0);
+    [self.collectionView layoutIfNeeded];
+    [self.adapter scrollToObject:@100 supplementaryKinds:nil scrollDirection:UICollectionViewScrollDirectionVertical scrollPosition:UICollectionViewScrollPositionBottom animated:NO];
+    IGAssertEqualPoint([self.collectionView contentOffset], 0, 900);
+}
+
 - (void)test_whenScrollHorizontallyToItem {
     // # of items for each object == [item integerValue], so @2 has 2 items (cells)
     IGListTestAdapterHorizontalDataSource *dataSource = [[IGListTestAdapterHorizontalDataSource alloc] init];