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use bevy_ecs::bundle::Bundle;
use crate::prelude::{GlobalTransform, Transform};
/// A [`Bundle`] of the [`Transform`] and [`GlobalTransform`]
/// [`Component`]s, which describe the position of an entity.
///
/// * To place or move an entity, you should set its [`Transform`].
/// * To get the global transform of an entity, you should get its [`GlobalTransform`].
/// * For transform hierarchies to work correctly, you must have both a [`Transform`] and a [`GlobalTransform`].
/// * You may use the [`TransformBundle`] to guarantee this.
///
/// ## [`Transform`] and [`GlobalTransform`]
///
/// [`Transform`] is the position of an entity relative to its parent position, or the reference
/// frame if it doesn't have a parent.
///
/// [`GlobalTransform`] is the position of an entity relative to the reference frame.
///
/// [`GlobalTransform`] is updated from [`Transform`] by systems in the system set
/// [`TransformPropagate`](TransformSystem::TransformPropagate).
///
/// This system runs during [`PostUpdate`]. If you
/// update the [`Transform`] of an entity in this schedule or after, you will notice a 1 frame lag
/// before the [`GlobalTransform`] is updated.
#[derive(Clone, Copy, Debug, Default, Bundle)]
pub struct TransformBundle {
/// The transform of the entity.
pub local: Transform,
/// The global transform of the entity.
pub global: GlobalTransform,
}
impl TransformBundle {
/// An identity [`TransformBundle`] with no translation, rotation, and a scale of 1 on all axes.
pub const IDENTITY: Self = TransformBundle {
local: Transform::IDENTITY,
global: GlobalTransform::IDENTITY,
};
/// Creates a new [`TransformBundle`] from a [`Transform`].
///
/// This initializes [`GlobalTransform`] as identity, to be updated later by the
/// [`PostUpdate`] schedule.
#[inline]
pub const fn from_transform(transform: Transform) -> Self {
TransformBundle {
local: transform,
..Self::IDENTITY
}
}
}
impl From<Transform> for TransformBundle {
#[inline]
fn from(transform: Transform) -> Self {
Self::from_transform(transform)
}
}