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Implement opt-in change detection bypass #2363

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Implement opt-in change detection bypass #2363

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6591742
Implement opt-in change detection
TheRawMeatball Jun 19, 2021
958f32e
Merge remote-tracking branch 'upstream/main' into get-untracked
TheRawMeatball Apr 4, 2022
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28 changes: 28 additions & 0 deletions crates/bevy_ecs/src/change_detection.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,9 @@ pub trait DetectChanges {
fn set_changed(&mut self);
}

// TODO: Add some nice docs here
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If someone would contribute to this point, it'd be highly appreciated

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/// When implemented for a component or resource type, this trait allows end users to manually bypass change detection within the ECS using the [`get_untracked`] method on `Query` and `World`.

I think that's where those methods live?

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I don't see the get_untracked methods in Query or World.

Are they found elsewhere? Or are they part of an unmerged PR?

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It was a "please add these methods too" comment for @TheRawMeatball ;)

pub trait AllowGetUntracked<Marker = ()> {}

macro_rules! change_detection_impl {
($name:ident < $( $generics:tt ),+ >, $target:ty, $($traits:ident)?) => {
impl<$($generics),* $(: $traits)?> DetectChanges for $name<$($generics),*> {
Expand Down Expand Up @@ -116,6 +119,28 @@ macro_rules! impl_into_inner {
};
}

macro_rules! impl_change_detection_circumvention {
($name:ident < $( $generics:tt ),+ >, $target:ty, $($traits:ident)?) => {
impl<$($generics),* $(: $traits)?> $name<$($generics),*> {
#[inline]
pub fn get_untracked(&mut self) -> &mut T
where
T: AllowGetUntracked,
{
self.value
}

#[inline]
pub fn get_untracked_with_token<Token>(&mut self, _: Token) -> &mut T
where
T: AllowGetUntracked<Token>,
{
self.value
}
}
};
}

macro_rules! impl_debug {
($name:ident < $( $generics:tt ),+ >, $($traits:ident)?) => {
impl<$($generics),* $(: $traits)?> std::fmt::Debug for $name<$($generics),*>
Expand Down Expand Up @@ -155,6 +180,7 @@ pub struct ResMut<'a, T: Resource> {

change_detection_impl!(ResMut<'a, T>, T, Resource);
impl_into_inner!(ResMut<'a, T>, T, Resource);
impl_change_detection_circumvention!(ResMut<'a, T>, T, Resource);
impl_debug!(ResMut<'a, T>, Resource);

/// Unique borrow of a non-[`Send`] resource.
Expand All @@ -176,6 +202,7 @@ pub struct NonSendMut<'a, T: 'static> {

change_detection_impl!(NonSendMut<'a, T>, T,);
impl_into_inner!(NonSendMut<'a, T>, T,);
impl_change_detection_circumvention!(NonSendMut<'a, T>, T,);
impl_debug!(NonSendMut<'a, T>,);

/// Unique mutable borrow of an entity's component
Expand All @@ -186,6 +213,7 @@ pub struct Mut<'a, T> {

change_detection_impl!(Mut<'a, T>, T,);
impl_into_inner!(Mut<'a, T>, T,);
impl_change_detection_circumvention!(Mut<'a, T>, T,);
impl_debug!(Mut<'a, T>,);

/// Unique mutable borrow of a Reflected component
Expand Down