`onViewableItemsChanged` doesn't work

[vojto]

Describe the bug

Using onViewableItemsChanged shows 12-13 items while you're at the top of the list. As soon as you scroll down a bit, it shows 1-2 visible items, which is not accurate.

To Reproduce

Run this snack and watch the console. You'll see the number of visible items is not accurate.

If you use regular FlatList, everything works fine.

Platform & Dependencies

• react-native-draggable-flatlist version: 3.1.1
• Platform: iOS
• React Native or Expo version: expo 45.0.0, React Native 0.68.2
• Reanimated version: 2.8.0
• React Native Gesture Handler version: 2.2.1