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//! Extension to [`EntityCommands`] to modify `bevy_hierarchy` hierarchies
//! while preserving [`GlobalTransform`].
use crate::prelude::{GlobalTransform, Transform};
use bevy_ecs::{prelude::Entity, system::EntityCommands, world::Command, world::World};
use bevy_hierarchy::{PushChild, RemoveParent};
/// Command similar to [`PushChild`], but updating the child transform to keep
/// it at the same [`GlobalTransform`].
///
/// You most likely want to use [`BuildChildrenTransformExt::set_parent_in_place`]
/// method on [`EntityCommands`] instead.
pub struct PushChildInPlace {
/// Parent entity to add the child to.
pub parent: Entity,
/// Child entity to add.
pub child: Entity,
}
impl Command for PushChildInPlace {
fn apply(self, world: &mut World) {
let hierarchy_command = PushChild {
child: self.child,
parent: self.parent,
};
hierarchy_command.apply(world);
// FIXME: Replace this closure with a `try` block. See: https://github.com/rust-lang/rust/issues/31436.
let mut update_transform = || {
let parent = *world.get_entity(self.parent)?.get::<GlobalTransform>()?;
let child_global = *world.get_entity(self.child)?.get::<GlobalTransform>()?;
let mut child_entity = world.get_entity_mut(self.child)?;
let mut child = child_entity.get_mut::<Transform>()?;
*child = child_global.reparented_to(&parent);
Some(())
};
update_transform();
}
}
/// Command similar to [`RemoveParent`], but updating the child transform to keep
/// it at the same [`GlobalTransform`].
///
/// You most likely want to use [`BuildChildrenTransformExt::remove_parent_in_place`]
/// method on [`EntityCommands`] instead.
pub struct RemoveParentInPlace {
/// [`Entity`] whose parent must be removed.
pub child: Entity,
}
impl Command for RemoveParentInPlace {
fn apply(self, world: &mut World) {
let hierarchy_command = RemoveParent { child: self.child };
hierarchy_command.apply(world);
// FIXME: Replace this closure with a `try` block. See: https://github.com/rust-lang/rust/issues/31436.
let mut update_transform = || {
let child_global = *world.get_entity(self.child)?.get::<GlobalTransform>()?;
let mut child_entity = world.get_entity_mut(self.child)?;
let mut child = child_entity.get_mut::<Transform>()?;
*child = child_global.compute_transform();
Some(())
};
update_transform();
}
}
/// Collection of methods similar to [`BuildChildren`](bevy_hierarchy::BuildChildren), but preserving each
/// entity's [`GlobalTransform`].
pub trait BuildChildrenTransformExt {
/// Change this entity's parent while preserving this entity's [`GlobalTransform`]
/// by updating its [`Transform`].
///
/// See [`BuildChildren::set_parent`](bevy_hierarchy::BuildChildren::set_parent) for a method that doesn't update the
/// [`Transform`].
///
/// Note that both the hierarchy and transform updates will only execute
/// the next time commands are applied
/// (during [`apply_deferred`](bevy_ecs::schedule::apply_deferred)).
fn set_parent_in_place(&mut self, parent: Entity) -> &mut Self;
/// Make this entity parentless while preserving this entity's [`GlobalTransform`]
/// by updating its [`Transform`] to be equal to its current [`GlobalTransform`].
///
/// See [`BuildChildren::remove_parent`](bevy_hierarchy::BuildChildren::remove_parent) for a method that doesn't update the
/// [`Transform`].
///
/// Note that both the hierarchy and transform updates will only execute
/// the next time commands are applied
/// (during [`apply_deferred`](bevy_ecs::schedule::apply_deferred)).
fn remove_parent_in_place(&mut self) -> &mut Self;
}
impl BuildChildrenTransformExt for EntityCommands<'_> {
fn set_parent_in_place(&mut self, parent: Entity) -> &mut Self {
let child = self.id();
self.commands().add(PushChildInPlace { child, parent });
self
}
fn remove_parent_in_place(&mut self) -> &mut Self {
let child = self.id();
self.commands().add(RemoveParentInPlace { child });
self
}
}