bevy_transform/
commands.rs

1//! Extension to [`EntityCommands`] to modify `bevy_hierarchy` hierarchies
2//! while preserving [`GlobalTransform`].
3
4use crate::prelude::{GlobalTransform, Transform};
5use bevy_ecs::{prelude::Entity, system::EntityCommands, world::Command, world::World};
6use bevy_hierarchy::{PushChild, RemoveParent};
7
8/// Command similar to [`PushChild`], but updating the child transform to keep
9/// it at the same [`GlobalTransform`].
10///
11/// You most likely want to use [`BuildChildrenTransformExt::set_parent_in_place`]
12/// method on [`EntityCommands`] instead.
13pub struct PushChildInPlace {
14    /// Parent entity to add the child to.
15    pub parent: Entity,
16    /// Child entity to add.
17    pub child: Entity,
18}
19impl Command for PushChildInPlace {
20    fn apply(self, world: &mut World) {
21        let hierarchy_command = PushChild {
22            child: self.child,
23            parent: self.parent,
24        };
25        hierarchy_command.apply(world);
26        // FIXME: Replace this closure with a `try` block. See: https://github.com/rust-lang/rust/issues/31436.
27        let mut update_transform = || {
28            let parent = *world.get_entity(self.parent)?.get::<GlobalTransform>()?;
29            let child_global = *world.get_entity(self.child)?.get::<GlobalTransform>()?;
30            let mut child_entity = world.get_entity_mut(self.child)?;
31            let mut child = child_entity.get_mut::<Transform>()?;
32            *child = child_global.reparented_to(&parent);
33            Some(())
34        };
35        update_transform();
36    }
37}
38/// Command similar to [`RemoveParent`], but updating the child transform to keep
39/// it at the same [`GlobalTransform`].
40///
41/// You most likely want to use [`BuildChildrenTransformExt::remove_parent_in_place`]
42/// method on [`EntityCommands`] instead.
43pub struct RemoveParentInPlace {
44    /// [`Entity`] whose parent must be removed.
45    pub child: Entity,
46}
47impl Command for RemoveParentInPlace {
48    fn apply(self, world: &mut World) {
49        let hierarchy_command = RemoveParent { child: self.child };
50        hierarchy_command.apply(world);
51        // FIXME: Replace this closure with a `try` block. See: https://github.com/rust-lang/rust/issues/31436.
52        let mut update_transform = || {
53            let child_global = *world.get_entity(self.child)?.get::<GlobalTransform>()?;
54            let mut child_entity = world.get_entity_mut(self.child)?;
55            let mut child = child_entity.get_mut::<Transform>()?;
56            *child = child_global.compute_transform();
57            Some(())
58        };
59        update_transform();
60    }
61}
62/// Collection of methods similar to [`BuildChildren`](bevy_hierarchy::BuildChildren), but preserving each
63/// entity's [`GlobalTransform`].
64pub trait BuildChildrenTransformExt {
65    /// Change this entity's parent while preserving this entity's [`GlobalTransform`]
66    /// by updating its [`Transform`].
67    ///
68    /// See [`BuildChildren::set_parent`](bevy_hierarchy::BuildChildren::set_parent) for a method that doesn't update the
69    /// [`Transform`].
70    ///
71    /// Note that both the hierarchy and transform updates will only execute
72    /// the next time commands are applied
73    /// (during [`apply_deferred`](bevy_ecs::schedule::apply_deferred)).
74    fn set_parent_in_place(&mut self, parent: Entity) -> &mut Self;
75
76    /// Make this entity parentless while preserving this entity's [`GlobalTransform`]
77    /// by updating its [`Transform`] to be equal to its current [`GlobalTransform`].
78    ///
79    /// See [`BuildChildren::remove_parent`](bevy_hierarchy::BuildChildren::remove_parent) for a method that doesn't update the
80    /// [`Transform`].
81    ///
82    /// Note that both the hierarchy and transform updates will only execute
83    /// the next time commands are applied
84    /// (during [`apply_deferred`](bevy_ecs::schedule::apply_deferred)).
85    fn remove_parent_in_place(&mut self) -> &mut Self;
86}
87impl BuildChildrenTransformExt for EntityCommands<'_> {
88    fn set_parent_in_place(&mut self, parent: Entity) -> &mut Self {
89        let child = self.id();
90        self.commands().add(PushChildInPlace { child, parent });
91        self
92    }
93
94    fn remove_parent_in_place(&mut self) -> &mut Self {
95        let child = self.id();
96        self.commands().add(RemoveParentInPlace { child });
97        self
98    }
99}
bevy_transform/commands.rs

bevy_transform/
commands.rs
