# Objective
- Fix#7263
This has nothing to do with #7024. This is for the case where the
user opted to **not** keep the same global transform on update.
## Solution
- Add a `RemovedComponent<Parent>` to `propagate_transforms`
- Add a `RemovedComponent<Parent>` and `Local<Vec<Entity>>` to
`sync_simple_transforms`
- Add test to make sure all of this works.
### Performance note
This should only incur a cost in cases where a parent is removed.
A minimal overhead (one look up in the `removed_components`
sparse set) per root entities without children which transform didn't
change. A `Vec` the size of the largest number of entities removed
with a `Parent` component in a single frame, and a binary search on
a `Vec` per root entities.
It could slow up considerably in situations where a lot of entities are
orphaned consistently during every frame, since
`sync_simple_transforms` is not parallel. But in this situation,
it is likely that the overhead of archetype updates overwhelms
everything.
---
## Changelog
- Fix the `GlobalTransform` not getting updated when `Parent` is removed
## Migration Guide
- If you called `bevy_transform::systems::sync_simple_transforms` and
`bevy_transform::systems::propagate_transforms` (which is not
re-exported by bevy) you need to account for the additional
`RemovedComponents<Parent>` parameter.
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Co-authored-by: vyb <vyb@users.noreply.github.com>
Co-authored-by: JoJoJet <21144246+JoJoJet@users.noreply.github.com>
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