Check for batch fetching on scroll #2124
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## Summary For collection views, we do not currently check for batch fetching on scroll. This appears to be a bug, as `scrollViewDidScroll:` does call `_checkForBatchFetching`, and [the commit that added it states it's trying to check on each scroll](TextureGroup@df497b8). Unfortunately, `_checkForBatchFetching` checks for `isTracking` and `isDragging` first and returns if either are `YES`. Since we're in a scroll, they are `YES`. So the call is effectively a no-op. This bug has been around for 9 years and I'm unsure of the performance implications of turning the batch fetching check on for each scroll tick. Therefore, put the fix behind an experiment feature flag _and_ only call it on the first scroll tick for the scroll session, instead of every scroll tick. Finally, I moved the check after the delegate call, in case the delegate has logic in it to turn on or off the batch fetching. ## Test plan Ran the app and manually tested batching getting called or not. Also ran `build.sh tests`.
raycsh017
approved these changes
May 22, 2025
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Summary
For collection views, we do not currently check for batch fetching on scroll. This appears to be a bug, as
scrollViewDidScroll:does call_checkForBatchFetching, and the commit that added it states it's trying to check on each scroll. Unfortunately,_checkForBatchFetchingchecks forisTrackingandisDraggingfirst and returns if either areYES. Since we're in a scroll, they areYES. So the call is effectively a no-op.This bug has been around for 9 years and I'm unsure of the performance implications of turning the batch fetching check on for each scroll tick. Therefore, put the fix behind an experiment feature flag and only call it on the first scroll tick for the scroll session, instead of every scroll tick. Finally, I moved the check after the delegate call, in case the delegate has logic in it to turn on or off the batch fetching.
Test plan
Ran the app and manually tested batching getting called or not. Also ran
build.sh tests.