/
system_param.rs
1748 lines (1574 loc) · 58.4 KB
/
system_param.rs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
pub use crate::change_detection::{NonSendMut, Res, ResMut};
use crate::{
archetype::{Archetype, Archetypes},
bundle::Bundles,
change_detection::{Ticks, TicksMut},
component::{ComponentId, ComponentTicks, Components, Tick},
entity::Entities,
query::{
Access, FilteredAccess, FilteredAccessSet, QueryData, QueryFilter, QueryState,
ReadOnlyQueryData,
},
system::{Query, SystemMeta},
world::{unsafe_world_cell::UnsafeWorldCell, FromWorld, World},
};
use bevy_ecs_macros::impl_param_set;
pub use bevy_ecs_macros::Resource;
pub use bevy_ecs_macros::SystemParam;
use bevy_ptr::UnsafeCellDeref;
use bevy_utils::{all_tuples, synccell::SyncCell};
use std::{
fmt::Debug,
marker::PhantomData,
ops::{Deref, DerefMut},
};
/// A parameter that can be used in a [`System`](super::System).
///
/// # Derive
///
/// This trait can be derived with the [`derive@super::SystemParam`] macro.
/// This macro only works if each field on the derived struct implements [`SystemParam`].
/// Note: There are additional requirements on the field types.
/// See the *Generic `SystemParam`s* section for details and workarounds of the probable
/// cause if this derive causes an error to be emitted.
///
/// Derived `SystemParam` structs may have two lifetimes: `'w` for data stored in the [`World`],
/// and `'s` for data stored in the parameter's state.
///
/// The following list shows the most common [`SystemParam`]s and which lifetime they require
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # #[derive(Resource)]
/// # struct SomeResource;
/// # #[derive(Event)]
/// # struct SomeEvent;
/// # #[derive(Resource)]
/// # struct SomeOtherResource;
/// # use bevy_ecs::system::SystemParam;
/// # #[derive(SystemParam)]
/// # struct ParamsExample<'w, 's> {
/// # query:
/// Query<'w, 's, Entity>,
/// # res:
/// Res<'w, SomeResource>,
/// # res_mut:
/// ResMut<'w, SomeOtherResource>,
/// # local:
/// Local<'s, u8>,
/// # commands:
/// Commands<'w, 's>,
/// # eventreader:
/// EventReader<'w, 's, SomeEvent>,
/// # eventwriter:
/// EventWriter<'w, SomeEvent>
/// # }
///```
/// ## `PhantomData`
///
/// [`PhantomData`] is a special type of `SystemParam` that does nothing.
/// This is useful for constraining generic types or lifetimes.
///
/// # Example
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # #[derive(Resource)]
/// # struct SomeResource;
/// use std::marker::PhantomData;
/// use bevy_ecs::system::SystemParam;
///
/// #[derive(SystemParam)]
/// struct MyParam<'w, Marker: 'static> {
/// foo: Res<'w, SomeResource>,
/// marker: PhantomData<Marker>,
/// }
///
/// fn my_system<T: 'static>(param: MyParam<T>) {
/// // Access the resource through `param.foo`
/// }
///
/// # bevy_ecs::system::assert_is_system(my_system::<()>);
/// ```
///
/// # Generic `SystemParam`s
///
/// When using the derive macro, you may see an error in the form of:
///
/// ```text
/// expected ... [ParamType]
/// found associated type `<[ParamType] as SystemParam>::Item<'_, '_>`
/// ```
/// where `[ParamType]` is the type of one of your fields.
/// To solve this error, you can wrap the field of type `[ParamType]` with [`StaticSystemParam`]
/// (i.e. `StaticSystemParam<[ParamType]>`).
///
/// ## Details
///
/// The derive macro requires that the [`SystemParam`] implementation of
/// each field `F`'s [`Item`](`SystemParam::Item`)'s is itself `F`
/// (ignoring lifetimes for simplicity).
/// This assumption is due to type inference reasons, so that the derived [`SystemParam`] can be
/// used as an argument to a function system.
/// If the compiler cannot validate this property for `[ParamType]`, it will error in the form shown above.
///
/// This will most commonly occur when working with `SystemParam`s generically, as the requirement
/// has not been proven to the compiler.
///
/// # Safety
///
/// The implementor must ensure the following is true.
/// - [`SystemParam::init_state`] correctly registers all [`World`] accesses used
/// by [`SystemParam::get_param`] with the provided [`system_meta`](SystemMeta).
/// - None of the world accesses may conflict with any prior accesses registered
/// on `system_meta`.
pub unsafe trait SystemParam: Sized {
/// Used to store data which persists across invocations of a system.
type State: Send + Sync + 'static;
/// The item type returned when constructing this system param.
/// The value of this associated type should be `Self`, instantiated with new lifetimes.
///
/// You could think of `SystemParam::Item<'w, 's>` as being an *operation* that changes the lifetimes bound to `Self`.
type Item<'world, 'state>: SystemParam<State = Self::State>;
/// Registers any [`World`] access used by this [`SystemParam`]
/// and creates a new instance of this param's [`State`](Self::State).
fn init_state(world: &mut World, system_meta: &mut SystemMeta) -> Self::State;
/// For the specified [`Archetype`], registers the components accessed by this [`SystemParam`] (if applicable).
#[inline]
fn new_archetype(
_state: &mut Self::State,
_archetype: &Archetype,
_system_meta: &mut SystemMeta,
) {
}
/// Applies any deferred mutations stored in this [`SystemParam`]'s state.
/// This is used to apply [`Commands`] during [`apply_deferred`](crate::prelude::apply_deferred).
///
/// [`Commands`]: crate::prelude::Commands
#[inline]
#[allow(unused_variables)]
fn apply(state: &mut Self::State, system_meta: &SystemMeta, world: &mut World) {}
/// Creates a parameter to be passed into a [`SystemParamFunction`].
///
/// [`SystemParamFunction`]: super::SystemParamFunction
///
/// # Safety
///
/// - The passed [`UnsafeWorldCell`] must have access to any world data
/// registered in [`init_state`](SystemParam::init_state).
/// - `world` must be the same `World` that was used to initialize [`state`](SystemParam::init_state).
unsafe fn get_param<'world, 'state>(
state: &'state mut Self::State,
system_meta: &SystemMeta,
world: UnsafeWorldCell<'world>,
change_tick: Tick,
) -> Self::Item<'world, 'state>;
}
/// A [`SystemParam`] that only reads a given [`World`].
///
/// # Safety
/// This must only be implemented for [`SystemParam`] impls that exclusively read the World passed in to [`SystemParam::get_param`]
pub unsafe trait ReadOnlySystemParam: SystemParam {}
/// Shorthand way of accessing the associated type [`SystemParam::Item`] for a given [`SystemParam`].
pub type SystemParamItem<'w, 's, P> = <P as SystemParam>::Item<'w, 's>;
// SAFETY: QueryState is constrained to read-only fetches, so it only reads World.
unsafe impl<'w, 's, D: ReadOnlyQueryData + 'static, F: QueryFilter + 'static> ReadOnlySystemParam
for Query<'w, 's, D, F>
{
}
// SAFETY: Relevant query ComponentId and ArchetypeComponentId access is applied to SystemMeta. If
// this Query conflicts with any prior access, a panic will occur.
unsafe impl<D: QueryData + 'static, F: QueryFilter + 'static> SystemParam for Query<'_, '_, D, F> {
type State = QueryState<D, F>;
type Item<'w, 's> = Query<'w, 's, D, F>;
fn init_state(world: &mut World, system_meta: &mut SystemMeta) -> Self::State {
let state = QueryState::new_with_access(world, &mut system_meta.archetype_component_access);
assert_component_access_compatibility(
&system_meta.name,
std::any::type_name::<D>(),
std::any::type_name::<F>(),
&system_meta.component_access_set,
&state.component_access,
world,
);
system_meta
.component_access_set
.add(state.component_access.clone());
state
}
fn new_archetype(state: &mut Self::State, archetype: &Archetype, system_meta: &mut SystemMeta) {
state.new_archetype(archetype, &mut system_meta.archetype_component_access);
}
#[inline]
unsafe fn get_param<'w, 's>(
state: &'s mut Self::State,
system_meta: &SystemMeta,
world: UnsafeWorldCell<'w>,
change_tick: Tick,
) -> Self::Item<'w, 's> {
// SAFETY: We have registered all of the query's world accesses,
// so the caller ensures that `world` has permission to access any
// world data that the query needs.
unsafe { Query::new(world, state, system_meta.last_run, change_tick) }
}
}
fn assert_component_access_compatibility(
system_name: &str,
query_type: &'static str,
filter_type: &'static str,
system_access: &FilteredAccessSet<ComponentId>,
current: &FilteredAccess<ComponentId>,
world: &World,
) {
let conflicts = system_access.get_conflicts_single(current);
if conflicts.is_empty() {
return;
}
let conflicting_components = conflicts
.into_iter()
.map(|component_id| world.components.get_info(component_id).unwrap().name())
.collect::<Vec<&str>>();
let accesses = conflicting_components.join(", ");
panic!("error[B0001]: Query<{query_type}, {filter_type}> in system {system_name} accesses component(s) {accesses} in a way that conflicts with a previous system parameter. Consider using `Without<T>` to create disjoint Queries or merging conflicting Queries into a `ParamSet`. See: https://bevyengine.org/learn/errors/#b0001");
}
/// A collection of potentially conflicting [`SystemParam`]s allowed by disjoint access.
///
/// Allows systems to safely access and interact with up to 8 mutually exclusive [`SystemParam`]s, such as
/// two queries that reference the same mutable data or an event reader and writer of the same type.
///
/// Each individual [`SystemParam`] can be accessed by using the functions `p0()`, `p1()`, ..., `p7()`,
/// according to the order they are defined in the `ParamSet`. This ensures that there's either
/// only one mutable reference to a parameter at a time or any number of immutable references.
///
/// # Examples
///
/// The following system mutably accesses the same component two times,
/// which is not allowed due to rust's mutability rules.
///
/// ```should_panic
/// # use bevy_ecs::prelude::*;
/// #
/// # #[derive(Component)]
/// # struct Health;
/// #
/// # #[derive(Component)]
/// # struct Enemy;
/// #
/// # #[derive(Component)]
/// # struct Ally;
/// #
/// // This will panic at runtime when the system gets initialized.
/// fn bad_system(
/// mut enemies: Query<&mut Health, With<Enemy>>,
/// mut allies: Query<&mut Health, With<Ally>>,
/// ) {
/// // ...
/// }
/// #
/// # let mut bad_system_system = IntoSystem::into_system(bad_system);
/// # let mut world = World::new();
/// # bad_system_system.initialize(&mut world);
/// # bad_system_system.run((), &mut world);
/// ```
///
/// Conflicting `SystemParam`s like these can be placed in a `ParamSet`,
/// which leverages the borrow checker to ensure that only one of the contained parameters are accessed at a given time.
///
/// ```
/// # use bevy_ecs::prelude::*;
/// #
/// # #[derive(Component)]
/// # struct Health;
/// #
/// # #[derive(Component)]
/// # struct Enemy;
/// #
/// # #[derive(Component)]
/// # struct Ally;
/// #
/// // Given the following system
/// fn fancy_system(
/// mut set: ParamSet<(
/// Query<&mut Health, With<Enemy>>,
/// Query<&mut Health, With<Ally>>,
/// )>
/// ) {
/// // This will access the first `SystemParam`.
/// for mut health in set.p0().iter_mut() {
/// // Do your fancy stuff here...
/// }
///
/// // The second `SystemParam`.
/// // This would fail to compile if the previous parameter was still borrowed.
/// for mut health in set.p1().iter_mut() {
/// // Do even fancier stuff here...
/// }
/// }
/// # bevy_ecs::system::assert_is_system(fancy_system);
/// ```
///
/// Of course, `ParamSet`s can be used with any kind of `SystemParam`, not just [queries](Query).
///
/// ```
/// # use bevy_ecs::prelude::*;
/// #
/// # #[derive(Event)]
/// # struct MyEvent;
/// # impl MyEvent {
/// # pub fn new() -> Self { Self }
/// # }
/// fn event_system(
/// mut set: ParamSet<(
/// // `EventReader`s and `EventWriter`s conflict with each other,
/// // since they both access the event queue resource for `MyEvent`.
/// EventReader<MyEvent>,
/// EventWriter<MyEvent>,
/// // `&World` reads the entire world, so a `ParamSet` is the only way
/// // that it can be used in the same system as any mutable accesses.
/// &World,
/// )>,
/// ) {
/// for event in set.p0().read() {
/// // ...
/// # let _event = event;
/// }
/// set.p1().send(MyEvent::new());
///
/// let entities = set.p2().entities();
/// // ...
/// # let _entities = entities;
/// }
/// # bevy_ecs::system::assert_is_system(event_system);
/// ```
pub struct ParamSet<'w, 's, T: SystemParam> {
param_states: &'s mut T::State,
world: UnsafeWorldCell<'w>,
system_meta: SystemMeta,
change_tick: Tick,
}
impl_param_set!();
/// A type that can be inserted into a [`World`] as a singleton.
///
/// You can access resource data in systems using the [`Res`] and [`ResMut`] system parameters
///
/// Only one resource of each type can be stored in a [`World`] at any given time.
///
/// # Examples
///
/// ```
/// # let mut world = World::default();
/// # let mut schedule = Schedule::default();
/// # use bevy_ecs::prelude::*;
/// #[derive(Resource)]
/// struct MyResource { value: u32 }
///
/// world.insert_resource(MyResource { value: 42 });
///
/// fn read_resource_system(resource: Res<MyResource>) {
/// assert_eq!(resource.value, 42);
/// }
///
/// fn write_resource_system(mut resource: ResMut<MyResource>) {
/// assert_eq!(resource.value, 42);
/// resource.value = 0;
/// assert_eq!(resource.value, 0);
/// }
/// # schedule.add_systems((read_resource_system, write_resource_system).chain());
/// # schedule.run(&mut world);
/// ```
///
/// # `!Sync` Resources
/// A `!Sync` type cannot implement `Resource`. However, it is possible to wrap a `Send` but not `Sync`
/// type in [`SyncCell`] or the currently unstable [`Exclusive`] to make it `Sync`. This forces only
/// having mutable access (`&mut T` only, never `&T`), but makes it safe to reference across multiple
/// threads.
///
/// This will fail to compile since `RefCell` is `!Sync`.
/// ```compile_fail
/// # use std::cell::RefCell;
/// # use bevy_ecs::system::Resource;
///
/// #[derive(Resource)]
/// struct NotSync {
/// counter: RefCell<usize>,
/// }
/// ```
///
/// This will compile since the `RefCell` is wrapped with `SyncCell`.
/// ```
/// # use std::cell::RefCell;
/// # use bevy_ecs::system::Resource;
/// use bevy_utils::synccell::SyncCell;
///
/// #[derive(Resource)]
/// struct ActuallySync {
/// counter: SyncCell<RefCell<usize>>,
/// }
/// ```
///
/// [`Exclusive`]: https://doc.rust-lang.org/nightly/std/sync/struct.Exclusive.html
pub trait Resource: Send + Sync + 'static {}
// SAFETY: Res only reads a single World resource
unsafe impl<'a, T: Resource> ReadOnlySystemParam for Res<'a, T> {}
// SAFETY: Res ComponentId and ArchetypeComponentId access is applied to SystemMeta. If this Res
// conflicts with any prior access, a panic will occur.
unsafe impl<'a, T: Resource> SystemParam for Res<'a, T> {
type State = ComponentId;
type Item<'w, 's> = Res<'w, T>;
fn init_state(world: &mut World, system_meta: &mut SystemMeta) -> Self::State {
let component_id = world.components.init_resource::<T>();
world.initialize_resource_internal(component_id);
let combined_access = system_meta.component_access_set.combined_access();
assert!(
!combined_access.has_write(component_id),
"error[B0002]: Res<{}> in system {} conflicts with a previous ResMut<{0}> access. Consider removing the duplicate access. See: https://bevyengine.org/learn/errors/#b0002",
std::any::type_name::<T>(),
system_meta.name,
);
system_meta
.component_access_set
.add_unfiltered_read(component_id);
let archetype_component_id = world
.get_resource_archetype_component_id(component_id)
.unwrap();
system_meta
.archetype_component_access
.add_read(archetype_component_id);
component_id
}
#[inline]
unsafe fn get_param<'w, 's>(
&mut component_id: &'s mut Self::State,
system_meta: &SystemMeta,
world: UnsafeWorldCell<'w>,
change_tick: Tick,
) -> Self::Item<'w, 's> {
let (ptr, ticks) = world
.get_resource_with_ticks(component_id)
.unwrap_or_else(|| {
panic!(
"Resource requested by {} does not exist: {}",
system_meta.name,
std::any::type_name::<T>()
)
});
Res {
value: ptr.deref(),
ticks: Ticks {
added: ticks.added.deref(),
changed: ticks.changed.deref(),
last_run: system_meta.last_run,
this_run: change_tick,
},
}
}
}
// SAFETY: Only reads a single World resource
unsafe impl<'a, T: Resource> ReadOnlySystemParam for Option<Res<'a, T>> {}
// SAFETY: this impl defers to `Res`, which initializes and validates the correct world access.
unsafe impl<'a, T: Resource> SystemParam for Option<Res<'a, T>> {
type State = ComponentId;
type Item<'w, 's> = Option<Res<'w, T>>;
fn init_state(world: &mut World, system_meta: &mut SystemMeta) -> Self::State {
Res::<T>::init_state(world, system_meta)
}
#[inline]
unsafe fn get_param<'w, 's>(
&mut component_id: &'s mut Self::State,
system_meta: &SystemMeta,
world: UnsafeWorldCell<'w>,
change_tick: Tick,
) -> Self::Item<'w, 's> {
world
.get_resource_with_ticks(component_id)
.map(|(ptr, ticks)| Res {
value: ptr.deref(),
ticks: Ticks {
added: ticks.added.deref(),
changed: ticks.changed.deref(),
last_run: system_meta.last_run,
this_run: change_tick,
},
})
}
}
// SAFETY: Res ComponentId and ArchetypeComponentId access is applied to SystemMeta. If this Res
// conflicts with any prior access, a panic will occur.
unsafe impl<'a, T: Resource> SystemParam for ResMut<'a, T> {
type State = ComponentId;
type Item<'w, 's> = ResMut<'w, T>;
fn init_state(world: &mut World, system_meta: &mut SystemMeta) -> Self::State {
let component_id = world.components.init_resource::<T>();
world.initialize_resource_internal(component_id);
let combined_access = system_meta.component_access_set.combined_access();
if combined_access.has_write(component_id) {
panic!(
"error[B0002]: ResMut<{}> in system {} conflicts with a previous ResMut<{0}> access. Consider removing the duplicate access. See: https://bevyengine.org/learn/errors/#b0002",
std::any::type_name::<T>(), system_meta.name);
} else if combined_access.has_read(component_id) {
panic!(
"error[B0002]: ResMut<{}> in system {} conflicts with a previous Res<{0}> access. Consider removing the duplicate access. See: https://bevyengine.org/learn/errors/#b0002",
std::any::type_name::<T>(), system_meta.name);
}
system_meta
.component_access_set
.add_unfiltered_write(component_id);
let archetype_component_id = world
.get_resource_archetype_component_id(component_id)
.unwrap();
system_meta
.archetype_component_access
.add_write(archetype_component_id);
component_id
}
#[inline]
unsafe fn get_param<'w, 's>(
&mut component_id: &'s mut Self::State,
system_meta: &SystemMeta,
world: UnsafeWorldCell<'w>,
change_tick: Tick,
) -> Self::Item<'w, 's> {
let value = world
.get_resource_mut_by_id(component_id)
.unwrap_or_else(|| {
panic!(
"Resource requested by {} does not exist: {}",
system_meta.name,
std::any::type_name::<T>()
)
});
ResMut {
value: value.value.deref_mut::<T>(),
ticks: TicksMut {
added: value.ticks.added,
changed: value.ticks.changed,
last_run: system_meta.last_run,
this_run: change_tick,
},
}
}
}
// SAFETY: this impl defers to `ResMut`, which initializes and validates the correct world access.
unsafe impl<'a, T: Resource> SystemParam for Option<ResMut<'a, T>> {
type State = ComponentId;
type Item<'w, 's> = Option<ResMut<'w, T>>;
fn init_state(world: &mut World, system_meta: &mut SystemMeta) -> Self::State {
ResMut::<T>::init_state(world, system_meta)
}
#[inline]
unsafe fn get_param<'w, 's>(
&mut component_id: &'s mut Self::State,
system_meta: &SystemMeta,
world: UnsafeWorldCell<'w>,
change_tick: Tick,
) -> Self::Item<'w, 's> {
world
.get_resource_mut_by_id(component_id)
.map(|value| ResMut {
value: value.value.deref_mut::<T>(),
ticks: TicksMut {
added: value.ticks.added,
changed: value.ticks.changed,
last_run: system_meta.last_run,
this_run: change_tick,
},
})
}
}
/// SAFETY: only reads world
unsafe impl<'w> ReadOnlySystemParam for &'w World {}
// SAFETY: `read_all` access is set and conflicts result in a panic
unsafe impl SystemParam for &'_ World {
type State = ();
type Item<'w, 's> = &'w World;
fn init_state(_world: &mut World, system_meta: &mut SystemMeta) -> Self::State {
let mut access = Access::default();
access.read_all();
if !system_meta
.archetype_component_access
.is_compatible(&access)
{
panic!("&World conflicts with a previous mutable system parameter. Allowing this would break Rust's mutability rules");
}
system_meta.archetype_component_access.extend(&access);
let mut filtered_access = FilteredAccess::default();
filtered_access.read_all();
if !system_meta
.component_access_set
.get_conflicts_single(&filtered_access)
.is_empty()
{
panic!("&World conflicts with a previous mutable system parameter. Allowing this would break Rust's mutability rules");
}
system_meta.component_access_set.add(filtered_access);
}
unsafe fn get_param<'w, 's>(
_state: &'s mut Self::State,
_system_meta: &SystemMeta,
world: UnsafeWorldCell<'w>,
_change_tick: Tick,
) -> Self::Item<'w, 's> {
// SAFETY: Read-only access to the entire world was registered in `init_state`.
unsafe { world.world() }
}
}
/// A system local [`SystemParam`].
///
/// A local may only be accessed by the system itself and is therefore not visible to other systems.
/// If two or more systems specify the same local type each will have their own unique local.
/// If multiple [`SystemParam`]s within the same system each specify the same local type
/// each will get their own distinct data storage.
///
/// The supplied lifetime parameter is the [`SystemParam`]s `'s` lifetime.
///
/// # Examples
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # let world = &mut World::default();
/// fn write_to_local(mut local: Local<usize>) {
/// *local = 42;
/// }
/// fn read_from_local(local: Local<usize>) -> usize {
/// *local
/// }
/// let mut write_system = IntoSystem::into_system(write_to_local);
/// let mut read_system = IntoSystem::into_system(read_from_local);
/// write_system.initialize(world);
/// read_system.initialize(world);
///
/// assert_eq!(read_system.run((), world), 0);
/// write_system.run((), world);
/// // Note how the read local is still 0 due to the locals not being shared.
/// assert_eq!(read_system.run((), world), 0);
/// ```
///
/// N.B. A [`Local`]s value cannot be read or written to outside of the containing system.
/// To add configuration to a system, convert a capturing closure into the system instead:
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # use bevy_ecs::system::assert_is_system;
/// struct Config(u32);
/// #[derive(Resource)]
/// struct MyU32Wrapper(u32);
/// fn reset_to_system(value: Config) -> impl FnMut(ResMut<MyU32Wrapper>) {
/// move |mut val| val.0 = value.0
/// }
///
/// // .add_systems(reset_to_system(my_config))
/// # assert_is_system(reset_to_system(Config(10)));
/// ```
#[derive(Debug)]
pub struct Local<'s, T: FromWorld + Send + 'static>(pub(crate) &'s mut T);
// SAFETY: Local only accesses internal state
unsafe impl<'s, T: FromWorld + Send + 'static> ReadOnlySystemParam for Local<'s, T> {}
impl<'s, T: FromWorld + Send + 'static> Deref for Local<'s, T> {
type Target = T;
#[inline]
fn deref(&self) -> &Self::Target {
self.0
}
}
impl<'s, T: FromWorld + Send + 'static> DerefMut for Local<'s, T> {
#[inline]
fn deref_mut(&mut self) -> &mut Self::Target {
self.0
}
}
impl<'s, 'a, T: FromWorld + Send + 'static> IntoIterator for &'a Local<'s, T>
where
&'a T: IntoIterator,
{
type Item = <&'a T as IntoIterator>::Item;
type IntoIter = <&'a T as IntoIterator>::IntoIter;
fn into_iter(self) -> Self::IntoIter {
self.0.into_iter()
}
}
impl<'s, 'a, T: FromWorld + Send + 'static> IntoIterator for &'a mut Local<'s, T>
where
&'a mut T: IntoIterator,
{
type Item = <&'a mut T as IntoIterator>::Item;
type IntoIter = <&'a mut T as IntoIterator>::IntoIter;
fn into_iter(self) -> Self::IntoIter {
self.0.into_iter()
}
}
// SAFETY: only local state is accessed
unsafe impl<'a, T: FromWorld + Send + 'static> SystemParam for Local<'a, T> {
type State = SyncCell<T>;
type Item<'w, 's> = Local<'s, T>;
fn init_state(world: &mut World, _system_meta: &mut SystemMeta) -> Self::State {
SyncCell::new(T::from_world(world))
}
#[inline]
unsafe fn get_param<'w, 's>(
state: &'s mut Self::State,
_system_meta: &SystemMeta,
_world: UnsafeWorldCell<'w>,
_change_tick: Tick,
) -> Self::Item<'w, 's> {
Local(state.get())
}
}
/// Types that can be used with [`Deferred<T>`] in systems.
/// This allows storing system-local data which is used to defer [`World`] mutations.
///
/// Types that implement `SystemBuffer` should take care to perform as many
/// computations up-front as possible. Buffers cannot be applied in parallel,
/// so you should try to minimize the time spent in [`SystemBuffer::apply`].
pub trait SystemBuffer: FromWorld + Send + 'static {
/// Applies any deferred mutations to the [`World`].
fn apply(&mut self, system_meta: &SystemMeta, world: &mut World);
}
/// A [`SystemParam`] that stores a buffer which gets applied to the [`World`] during
/// [`apply_deferred`](crate::schedule::apply_deferred).
/// This is used internally by [`Commands`] to defer `World` mutations.
///
/// [`Commands`]: crate::system::Commands
///
/// # Examples
///
/// By using this type to defer mutations, you can avoid mutable `World` access within
/// a system, which allows it to run in parallel with more systems.
///
/// Note that deferring mutations is *not* free, and should only be used if
/// the gains in parallelization outweigh the time it takes to apply deferred mutations.
/// In general, [`Deferred`] should only be used for mutations that are infrequent,
/// or which otherwise take up a small portion of a system's run-time.
///
/// ```
/// # use bevy_ecs::prelude::*;
/// // Tracks whether or not there is a threat the player should be aware of.
/// #[derive(Resource, Default)]
/// pub struct Alarm(bool);
///
/// #[derive(Component)]
/// pub struct Settlement {
/// // ...
/// }
///
/// // A threat from inside the settlement.
/// #[derive(Component)]
/// pub struct Criminal;
///
/// // A threat from outside the settlement.
/// #[derive(Component)]
/// pub struct Monster;
///
/// # impl Criminal { pub fn is_threat(&self, _: &Settlement) -> bool { true } }
///
/// use bevy_ecs::system::{Deferred, SystemBuffer, SystemMeta};
///
/// // Uses deferred mutations to allow signalling the alarm from multiple systems in parallel.
/// #[derive(Resource, Default)]
/// struct AlarmFlag(bool);
///
/// impl AlarmFlag {
/// /// Sounds the alarm the next time buffers are applied via apply_deferred.
/// pub fn flag(&mut self) {
/// self.0 = true;
/// }
/// }
///
/// impl SystemBuffer for AlarmFlag {
/// // When `AlarmFlag` is used in a system, this function will get
/// // called the next time buffers are applied via apply_deferred.
/// fn apply(&mut self, system_meta: &SystemMeta, world: &mut World) {
/// if self.0 {
/// world.resource_mut::<Alarm>().0 = true;
/// self.0 = false;
/// }
/// }
/// }
///
/// // Sound the alarm if there are any criminals who pose a threat.
/// fn alert_criminal(
/// settlements: Query<&Settlement>,
/// criminals: Query<&Criminal>,
/// mut alarm: Deferred<AlarmFlag>
/// ) {
/// let settlement = settlements.single();
/// for criminal in &criminals {
/// // Only sound the alarm if the criminal is a threat.
/// // For this example, assume that this check is expensive to run.
/// // Since the majority of this system's run-time is dominated
/// // by calling `is_threat()`, we defer sounding the alarm to
/// // allow this system to run in parallel with other alarm systems.
/// if criminal.is_threat(settlement) {
/// alarm.flag();
/// }
/// }
/// }
///
/// // Sound the alarm if there is a monster.
/// fn alert_monster(
/// monsters: Query<&Monster>,
/// mut alarm: ResMut<Alarm>
/// ) {
/// if monsters.iter().next().is_some() {
/// // Since this system does nothing except for sounding the alarm,
/// // it would be pointless to defer it, so we sound the alarm directly.
/// alarm.0 = true;
/// }
/// }
///
/// let mut world = World::new();
/// world.init_resource::<Alarm>();
/// world.spawn(Settlement {
/// // ...
/// });
///
/// let mut schedule = Schedule::default();
/// // These two systems have no conflicts and will run in parallel.
/// schedule.add_systems((alert_criminal, alert_monster));
///
/// // There are no criminals or monsters, so the alarm is not sounded.
/// schedule.run(&mut world);
/// assert_eq!(world.resource::<Alarm>().0, false);
///
/// // Spawn a monster, which will cause the alarm to be sounded.
/// let m_id = world.spawn(Monster).id();
/// schedule.run(&mut world);
/// assert_eq!(world.resource::<Alarm>().0, true);
///
/// // Remove the monster and reset the alarm.
/// world.entity_mut(m_id).despawn();
/// world.resource_mut::<Alarm>().0 = false;
///
/// // Spawn a criminal, which will cause the alarm to be sounded.
/// world.spawn(Criminal);
/// schedule.run(&mut world);
/// assert_eq!(world.resource::<Alarm>().0, true);
/// ```
pub struct Deferred<'a, T: SystemBuffer>(pub(crate) &'a mut T);
impl<'a, T: SystemBuffer> Deref for Deferred<'a, T> {
type Target = T;
#[inline]
fn deref(&self) -> &Self::Target {
self.0
}
}
impl<'a, T: SystemBuffer> DerefMut for Deferred<'a, T> {
#[inline]
fn deref_mut(&mut self) -> &mut Self::Target {
self.0
}
}
impl<T: SystemBuffer> Deferred<'_, T> {
/// Returns a [`Deferred<T>`] with a smaller lifetime.
/// This is useful if you have `&mut Deferred<T>` but need `Deferred<T>`.
pub fn reborrow(&mut self) -> Deferred<T> {
Deferred(self.0)
}
}
// SAFETY: Only local state is accessed.
unsafe impl<T: SystemBuffer> ReadOnlySystemParam for Deferred<'_, T> {}
// SAFETY: Only local state is accessed.
unsafe impl<T: SystemBuffer> SystemParam for Deferred<'_, T> {
type State = SyncCell<T>;
type Item<'w, 's> = Deferred<'s, T>;
fn init_state(world: &mut World, system_meta: &mut SystemMeta) -> Self::State {
system_meta.set_has_deferred();
SyncCell::new(T::from_world(world))
}
fn apply(state: &mut Self::State, system_meta: &SystemMeta, world: &mut World) {
state.get().apply(system_meta, world);
}
unsafe fn get_param<'w, 's>(
state: &'s mut Self::State,
_system_meta: &SystemMeta,
_world: UnsafeWorldCell<'w>,
_change_tick: Tick,
) -> Self::Item<'w, 's> {
Deferred(state.get())
}
}
/// Shared borrow of a non-[`Send`] resource.
///
/// Only `Send` resources may be accessed with the [`Res`] [`SystemParam`]. In case that the
/// resource does not implement `Send`, this `SystemParam` wrapper can be used. This will instruct
/// the scheduler to instead run the system on the main thread so that it doesn't send the resource
/// over to another thread.
///
/// # Panics
///
/// Panics when used as a `SystemParameter` if the resource does not exist.
///
/// Use `Option<NonSend<T>>` instead if the resource might not always exist.
pub struct NonSend<'w, T: 'static> {
pub(crate) value: &'w T,
ticks: ComponentTicks,
last_run: Tick,
this_run: Tick,
}
// SAFETY: Only reads a single World non-send resource
unsafe impl<'w, T> ReadOnlySystemParam for NonSend<'w, T> {}
impl<'w, T> Debug for NonSend<'w, T>
where
T: Debug,
{
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_tuple("NonSend").field(&self.value).finish()
}
}
impl<'w, T: 'static> NonSend<'w, T> {
/// Returns `true` if the resource was added after the system last ran.
pub fn is_added(&self) -> bool {
self.ticks.is_added(self.last_run, self.this_run)
}
/// Returns `true` if the resource was added or mutably dereferenced after the system last ran.
pub fn is_changed(&self) -> bool {
self.ticks.is_changed(self.last_run, self.this_run)
}
}
impl<'w, T> Deref for NonSend<'w, T> {
type Target = T;