fix: `onGestureEnd` -> `endWithSpring` uses outdated data via `useSharedValue`

Open nmassey opened this issue 11 months ago • 3 comments

What: the bug

When endWithSpring is called, it is using the previous values for scrollEndVelocity and scrollEndTranslation (rather than the values just set in onGestureEnd). This seems to cause strange carousel behavior for the user: the function isn't using the values from the most recent pan.

From the user's standpoint, the problem is very obvious (and potentially frustrating) when the user pans one direction, then reverses direction for their next pan. (Please see video demonstration below.)

Why

This is due to updates to shared values created via useSharedValue() updating asynchronously (see https://docs.swmansion.com/react-native-reanimated/docs/core/useSharedValue#remarks ).

What: proposed fix

Rather than relying on the shared data variable between function calls, let's explicitly pass the values as arguments to endWithSpring.

May resolve the following issues

https://github.com/dohooo/react-native-reanimated-carousel/issues/535
https://github.com/dohooo/react-native-reanimated-carousel/issues/568
#579

Screengrab video recordings

buggy behavior on `4.0.0-alpha.10` (unpatched)

Notice, panning the same direction works OK, but panning alternate direction fails.

https://github.com/dohooo/react-native-reanimated-carousel/assets/589004/af7ce523-57d0-4fbf-a338-741b55056c7a

improved behavior with patch

https://github.com/dohooo/react-native-reanimated-carousel/assets/589004/55fad5c5-d702-48c8-8956-06613b014e0c

Mar 23 '24 06:03 nmassey

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