## Problem
- The `Query` struct does not provide an easy way to check if it is empty.
- Specifically, users have to use `.iter().peekable()` or `.iter().next().is_none()` which is not very ergonomic.
- Fixes: #2270
## Solution
- Implement an `is_empty` function for queries to more easily check if the query is empty.
This enables `SystemParams` to be used outside of function systems. Anything can create and store `SystemState`, which enables efficient "param state cached" access to `SystemParams`.
It adds a `ReadOnlySystemParamFetch` trait, which enables safe `SystemState::get` calls without unique world access.
I renamed the old `SystemState` to `SystemMeta` to enable us to mirror the `QueryState` naming convention (but I'm happy to discuss alternative names if people have other ideas). I initially pitched this as `ParamState`, but given that it needs to include full system metadata, that doesn't feel like a particularly accurate name.
```rust
#[derive(Eq, PartialEq, Debug)]
struct A(usize);
#[derive(Eq, PartialEq, Debug)]
struct B(usize);
let mut world = World::default();
world.insert_resource(A(42));
world.spawn().insert(B(7));
// we get nice lifetime elision when declaring the type on the left hand side
let mut system_state: SystemState<(Res<A>, Query<&B>)> = SystemState::new(&mut world);
let (a, query) = system_state.get(&world);
assert_eq!(*a, A(42), "returned resource matches initial value");
assert_eq!(
*query.single().unwrap(),
B(7),
"returned component matches initial value"
);
// mutable system params require unique world access
let mut system_state: SystemState<(ResMut<A>, Query<&mut B>)> = SystemState::new(&mut world);
let (a, query) = system_state.get_mut(&mut world);
// static lifetimes are required when declaring inside of structs
struct SomeContainer {
state: SystemState<(Res<'static, A>, Res<'static, B>)>
}
// this can be shortened using type aliases, which will be useful for complex param tuples
type MyParams<'a> = (Res<'a, A>, Res<'a, B>);
struct SomeContainer {
state: SystemState<MyParams<'static>>
}
// It is the user's responsibility to call SystemState::apply(world) for parameters that queue up work
let mut system_state: SystemState<(Commands, Query<&B>)> = SystemState::new(&mut world);
{
let (mut commands, query) = system_state.get(&world);
commands.insert_resource(3.14);
}
system_state.apply(&mut world);
```
## Future Work
* Actually use SystemState inside FunctionSystem. This would be trivial, but it requires FunctionSystem to wrap SystemState in Option in its current form (which complicates system metadata lookup). I'd prefer to hold off until we adopt something like the later designs linked in #1364, which enable us to contruct Systems using a World reference (and also remove the need for `.system`).
* Consider a "scoped" approach to automatically call SystemState::apply when systems params are no longer being used (either a container type with a Drop impl, or a function that takes a closure for user logic operating on params).
When dropping the data, we originally only checked the size of an individual item instead of the size of the allocation. However with a capacity of 0, we attempt to deallocate a pointer which was not the result of allocation. That is, an item of `Layout { size_: 8, align_: 8 }` produces an array of `Layout { size_: 0, align_: 8 }` when `capacity = 0`.
Fixes#2294
## Objective
- Fixes: #2275
- `Assets` were being flagged as 'changed' each frame regardless of if the assets were actually being updated.
## Solution
- Only have `Assets` change detection be triggered when the collection is actually modified.
- This includes utilizing `ResMut` further down the stack instead of a `&mut Assets` directly.
Continuing the work on reducing the safety footguns in the code, I've removed one extra `UnsafeCell` in favour of safe `Cell` usage inisde `ComponentTicks`. That change led to discovery of misbehaving component insert logic, where data wasn't properly dropped when overwritten. Apart from that being fixed, some method names were changed to better convey the "initialize new allocation" and "replace existing allocation" semantic.
Depends on #2221, I will rebase this PR after the dependency is merged. For now, review just the last commit.
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
`ResMut`, `Mut` and `ReflectMut` all share very similar code for change detection.
This PR is a first pass at refactoring these implementation and removing a lot of the duplicated code.
Note, this introduces a new trait `ChangeDetectable`.
Please feel free to comment away and let me know what you think!
I've noticed that we are overusing interior mutability of the Table data, where in many cases we already own a unique reference to it. That prompted a slight refactor aiming to reduce number of safety constraints that must be manually upheld. Now the majority of those are just about avoiding bound checking, which is relatively easy to prove right.
Another aspect is reducing the complexity of Table struct. Notably, we don't ever use archetypes stored there, so this whole thing goes away. Capacity and grow amount were mostly superficial, as we are already using Vecs inside anyway, so I've got rid of those too. Now the overall table capacity is being driven by the internal entity Vec capacity. This has a side effect of automatically implementing exponential growth pattern for BitVecs reallocations inside Table, which to my measurements slightly improves performance in tests that are heavy on inserts. YMMV, but I hope that those tests were at least remotely correct.
The previous implementation of `Events::extend` iterated through each event and manually `sent` it via `Events:;send`.
However, this could be a minor performance hit since calling `Vec::push` in a loop is not optimal.
This refactors the code to use `Vec::extend`.
This new api stems from this [discord conversation](https://discord.com/channels/691052431525675048/742569353878437978/844057268172357663).
This exposes a public facing `set_changed` method on `ResMut` and `Mut`.
As a side note: `ResMut` and `Mut` have a lot of duplicated code, I have a PR I may put up later that refactors these commonalities into a trait.
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
- simplified code around archetype generations a little bit, as the special case value is not actually needed
- removed unnecessary UnsafeCell around pointer value that is never updated through shared references
- fixed and added a test for correct drop behaviour when removing sparse components through remove_bundle command
While trying to figure out how to implement a `SystemParam`, I spent a
long time looking for a feature that would do exactly what `Config`
does. I ignored it at first because all the examples I could find used
`()` and I couldn't see a way to modify it.
This is documented in other places, but `Config` is a logical place to
include some breadcrumbs. I've added some text that gives a brief
overview of what `Config` is for, and links to the existing docs on
`FunctionSystem::config` for more details.
This would have saved me from embarrassing myself by filing https://github.com/bevyengine/bevy/issues/2178.
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
During PR #2046 @cart suggested that the `(): ()` notation is less legible than `_input: ()`. The first notation still managed to slip in though. This PR applies the second writing.
Related to [discussion on discord](https://discord.com/channels/691052431525675048/742569353878437978/824731187724681289)
With const generics, it is now possible to write generic iterator over multiple entities at once.
This enables patterns of query iterations like
```rust
for [e1, e2, e3] in query.iter_combinations() {
// do something with relation of all three entities
}
```
The compiler is able to infer the correct iterator for given size of array, so either of those work
```rust
for [e1, e2] in query.iter_combinations() { ... }
for [e1, e2, e3] in query.iter_combinations() { ... }
```
This feature can be very useful for systems like collision detection.
When you ask for permutations of size K of N entities:
- if K == N, you get one result of all entities
- if K < N, you get all possible subsets of N with size K, without repetition
- if K > N, the result set is empty (no permutation of size K exist)
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
This can save users from having to type `&*X` all the time at the cost of some complexity in the type signature. For instance, this allows me to accommodate @jakobhellermann's suggestion in #1799 without requiring users to type `&*windows` 99% of the time.
`ParallelSystemContainer`'s `system` pointer was extracted from box, but it was never deallocated. This change adds missing drop implementation that cleans up that memory.
The first commit monomorphizes `add_system_inner` which I think was intended to be monomorphized anyway. The second commit moves the type argument of `GraphNode` to an associated type.
In response to #2023, here is a draft for a PR.
Fixes#2023
I've added an example to show how to use `WithBundle`, and also to test it out.
Right now there is a bug: If a bundle and a query are "the same", then it doesn't filter out
what it needs to filter out.
Example:
```
Print component initated from bundle.
[examples/ecs/query_bundle.rs:57] x = Dummy( <========= This should not get printed
111,
)
[examples/ecs/query_bundle.rs:57] x = Dummy(
222,
)
Show all components
[examples/ecs/query_bundle.rs:50] x = Dummy(
111,
)
[examples/ecs/query_bundle.rs:50] x = Dummy(
222,
)
```
However, it behaves the right way, if I add one more component to the bundle,
so the query and the bundle doesn't look the same:
```
Print component initated from bundle.
[examples/ecs/query_bundle.rs:57] x = Dummy(
222,
)
Show all components
[examples/ecs/query_bundle.rs:50] x = Dummy(
111,
)
[examples/ecs/query_bundle.rs:50] x = Dummy(
222,
)
```
I hope this helps. I'm definitely up for tinkering with this, and adding anything that I'm asked to add
or change.
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
I'm using Bevy ECS in a project of mine and I'd like to do world changes asynchronously.
The current public API for creating entities, `Commands` , has a lifetime that restricts it from being sent across threads. `CommandQueue` on the other hand is a Vec of commands that can be later ran on a World.
So far this is all public, but the commands themselves are private API. I know the intented use is with `Commands`, but that's not possible for my use case as I mentioned, and so I simply copied over the code for the commands I need and it works. Obviously, this isn't a nice solution, so I'd like to ask if it's not out of scope to make the commands public?
The documentation for `ShouldRun` doesn't completely explain what each of the variants you can return does. For instance, it isn't very clear that looping systems aren't executed again until after all the systems in a stage have had a chance to run.
This PR adds to the documentation for `ShouldRun`, and hopefully clarifies what is happening during a stage's execution when run criteria are checked and systems are being executed.
Some panic messages for systems include the system name, but there's a few panic messages which do not. This PR adds the system name for the remaining panic messages.
This is a continuation of the work done in #1864.
Related: #1846
This shrinks breakout from 316k to 310k when using `--feature dynamic`.
I haven't run the ecs benchmark to test performance as my laptop is too noisy for reliable benchmarking.
We discussed with @alice-i-cecile privately on iterators and agreed that making a custom ordered iterator over query makes no sense since materialization is required anyway and it's better to reuse existing components or code. Therefore, just adding an example to the documentation as requested.
Fixes#1470.
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
This includes a lot of single line comments where either saying more wasn't helpful or due to me not knowing enough about things yet to be able to go more indepth. Proofreading is very much welcome.
Fixes#1846
Got scared of the other "Requested resource does not exist" error at line 395 in `system_param.rs`, under `impl<'a, T: Component> SystemParamFetch<'a> for ResMutState<T> {`. Someone with better knowledge of the code might be able to go in and improve that one.
Fixes#1809. It makes it also possible to use `derive` for `SystemParam` inside ECS and avoid manual implementation. An alternative solution to macro changes is to use `use crate as bevy_ecs;` in `event.rs`.
