`PickingInteraction` change detection is triggered continuously

[djeedai]

Bevy version

0.16

What you did

mut query: Query<(&PickingInteraction, &Transform), Changed<PickingInteraction>>,

What went wrong

Triggers continuously instead of when mouse hovers/leaves.

Additional information

bevy_picking::hover::update_interactions() starts by clearing all components to PickingInteraction::None before recomputing. So even if the value didn't change, mutation has been recorded and it's too late. This makes it impossible to write systems which act on the first/last hover, which should be an extremely common pattern especially in UI (highlight a button, etc.).