bevy_transform/
commands.rs

1//! Extension to [`EntityCommands`] to modify [`bevy_ecs::hierarchy`] hierarchies.
2//! while preserving [`GlobalTransform`].
3
4use crate::prelude::{GlobalTransform, Transform};
5use bevy_ecs::{entity::Entity, hierarchy::ChildOf, system::EntityCommands, world::EntityWorldMut};
6
7/// Collection of methods similar to the built-in parenting methods on [`EntityWorldMut`] and [`EntityCommands`], but preserving each
8/// entity's [`GlobalTransform`].
9pub trait BuildChildrenTransformExt {
10    /// Change this entity's parent while preserving this entity's [`GlobalTransform`]
11    /// by updating its [`Transform`].
12    ///
13    /// Insert the [`ChildOf`] component directly if you don't want to also update the [`Transform`].
14    ///
15    /// Note that both the hierarchy and transform updates will only execute
16    /// the next time commands are applied
17    /// (during [`ApplyDeferred`](bevy_ecs::schedule::ApplyDeferred)).
18    fn set_parent_in_place(&mut self, parent: Entity) -> &mut Self;
19
20    /// Make this entity parentless while preserving this entity's [`GlobalTransform`]
21    /// by updating its [`Transform`] to be equal to its current [`GlobalTransform`].
22    ///
23    /// See [`EntityWorldMut::remove::<ChildOf>`] or [`EntityCommands::remove::<ChildOf>`] for a method that doesn't update the [`Transform`].
24    ///
25    /// Note that both the hierarchy and transform updates will only execute
26    /// the next time commands are applied
27    /// (during [`ApplyDeferred`](bevy_ecs::schedule::ApplyDeferred)).
28    fn remove_parent_in_place(&mut self) -> &mut Self;
29}
30
31impl BuildChildrenTransformExt for EntityCommands<'_> {
32    fn set_parent_in_place(&mut self, parent: Entity) -> &mut Self {
33        self.queue(move |mut entity: EntityWorldMut| {
34            entity.set_parent_in_place(parent);
35        })
36    }
37
38    fn remove_parent_in_place(&mut self) -> &mut Self {
39        self.queue(move |mut entity: EntityWorldMut| {
40            entity.remove_parent_in_place();
41        })
42    }
43}
44
45impl BuildChildrenTransformExt for EntityWorldMut<'_> {
46    fn set_parent_in_place(&mut self, parent: Entity) -> &mut Self {
47        // FIXME: Replace this closure with a `try` block. See: https://github.com/rust-lang/rust/issues/31436.
48        let mut update_transform = || {
49            let child = self.id();
50            let parent_global = self.world_scope(|world| {
51                world
52                    .get_entity_mut(parent)
53                    .ok()?
54                    .add_child(child)
55                    .get::<GlobalTransform>()
56                    .copied()
57            })?;
58            let child_global = self.get::<GlobalTransform>()?;
59            let new_child_local = child_global.reparented_to(&parent_global);
60            let mut child_local = self.get_mut::<Transform>()?;
61            *child_local = new_child_local;
62            Some(())
63        };
64        update_transform();
65        self
66    }
67
68    fn remove_parent_in_place(&mut self) -> &mut Self {
69        self.remove::<ChildOf>();
70        // FIXME: Replace this closure with a `try` block. See: https://github.com/rust-lang/rust/issues/31436.
71        let mut update_transform = || {
72            let global = self.get::<GlobalTransform>()?;
73            let new_local = global.compute_transform();
74            let mut local = self.get_mut::<Transform>()?;
75            *local = new_local;
76            Some(())
77        };
78        update_transform();
79        self
80    }
81}
bevy_transform/commands.rs

bevy_transform/
commands.rs
