fix load previous messages UI flashing bug

Summary:
More reliably prevent animations in `-[IGListAdapter performUpdatesAnimated: completion:]`.

Fixes potential UI flashing and glitches in `performUpdatesAnimated:` when suppressing animations by passing `NO`.

Reviewed By: rnystrom

Differential Revision: D4453115

fbshipit-source-id: a9418b4bc0e11a14d6a5037178bade424ef9617d

CHANGELOG.md

@@ -32,9 +32,13 @@ This release closes the [2.2.0 milestone](https://github.com/Instagram/IGListKit
 ### Fixes
 
 - Fix bug where emptyView's hidden status is not updated after the number of items is changed with `insertInSectionController:atIndexes:` or related methods. [Peter Edmonston](https://github.com/edmonston) [(#395)](https://github.com/Instagram/IGListKit/pull/395)
+
 - Fix bug where `IGListStackedSectionController`'s children need to know `numberOrItems` before didUpdate is called. [(#348)](https://github.com/Instagram/IGListKit/pull/390)
+
 - Fix bug where `-[UICollectionViewCell ig_setStackedSectionControllerIndex:]` should use `OBJC_ASSOCIATION_COPY_NONATOMIC` for NSNumber. [PhilCai](https://github.com/PhilCai1993) [(#424)](https://github.com/Instagram/IGListKit/pull/426)
 
+- Fix potential bug with suppressing animations (by passing `NO`) during `-[IGListAdapter performUpdatesAnimated: completion:]` where user would see UI glitches/flashing. [Jesse Squires](https://github.com/jessesquires) [(tbd)]()
+
 2.1.0
 -----
 

Source/IGListAdapterUpdater.m

@@ -211,8 +211,11 @@ - (void)performBatchUpdatesWithCollectionView:(UICollectionView *)collectionView
  if (animated) {
  [collectionView performBatchUpdates:updateBlock completion:completionBlock];
  } else {
- [UIView performWithoutAnimation:^{
- [collectionView performBatchUpdates:updateBlock completion:completionBlock];
+ [CATransaction begin];
+ [CATransaction setDisableActions:YES];
+ [collectionView performBatchUpdates:updateBlock completion:^(BOOL finished) {
+ completionBlock(finished);
+ [CATransaction commit];
  }];
  }
  } @catch (NSException *exception) {