1use crate::{App, AppContext, GpuiBorrow, VisualContext, Window, seal::Sealed};
2use anyhow::{Context as _, Result};
3use collections::FxHashSet;
4use derive_more::{Deref, DerefMut};
5use parking_lot::{RwLock, RwLockUpgradableReadGuard};
6use slotmap::{KeyData, SecondaryMap, SlotMap};
7use std::{
8 any::{Any, TypeId, type_name},
9 cell::RefCell,
10 cmp::Ordering,
11 fmt::{self, Display},
12 hash::{Hash, Hasher},
13 marker::PhantomData,
14 mem,
15 num::NonZeroU64,
16 sync::{
17 Arc, Weak,
18 atomic::{AtomicU64, AtomicUsize, Ordering::SeqCst},
19 },
20 thread::panicking,
21};
22
23use super::Context;
24use crate::util::atomic_incr_if_not_zero;
25#[cfg(any(test, feature = "leak-detection"))]
26use collections::HashMap;
27
28slotmap::new_key_type! {
29 /// A unique identifier for a entity across the application.
30 pub struct EntityId;
31}
32
33impl From<u64> for EntityId {
34 fn from(value: u64) -> Self {
35 Self(KeyData::from_ffi(value))
36 }
37}
38
39impl EntityId {
40 /// Converts this entity id to a [NonZeroU64]
41 pub fn as_non_zero_u64(self) -> NonZeroU64 {
42 NonZeroU64::new(self.0.as_ffi()).unwrap()
43 }
44
45 /// Converts this entity id to a [u64]
46 pub fn as_u64(self) -> u64 {
47 self.0.as_ffi()
48 }
49}
50
51impl Display for EntityId {
52 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
53 write!(f, "{}", self.as_u64())
54 }
55}
56
57pub(crate) struct EntityMap {
58 entities: SecondaryMap<EntityId, Box<dyn Any>>,
59 pub accessed_entities: RefCell<FxHashSet<EntityId>>,
60 ref_counts: Arc<RwLock<EntityRefCounts>>,
61}
62
63struct EntityRefCounts {
64 counts: SlotMap<EntityId, AtomicUsize>,
65 dropped_entity_ids: Vec<EntityId>,
66 #[cfg(any(test, feature = "leak-detection"))]
67 leak_detector: LeakDetector,
68}
69
70impl EntityMap {
71 pub fn new() -> Self {
72 Self {
73 entities: SecondaryMap::new(),
74 accessed_entities: RefCell::new(FxHashSet::default()),
75 ref_counts: Arc::new(RwLock::new(EntityRefCounts {
76 counts: SlotMap::with_key(),
77 dropped_entity_ids: Vec::new(),
78 #[cfg(any(test, feature = "leak-detection"))]
79 leak_detector: LeakDetector {
80 next_handle_id: 0,
81 entity_handles: HashMap::default(),
82 },
83 })),
84 }
85 }
86
87 /// Reserve a slot for an entity, which you can subsequently use with `insert`.
88 pub fn reserve<T: 'static>(&self) -> Slot<T> {
89 let id = self.ref_counts.write().counts.insert(1.into());
90 Slot(Entity::new(id, Arc::downgrade(&self.ref_counts)))
91 }
92
93 /// Insert an entity into a slot obtained by calling `reserve`.
94 pub fn insert<T>(&mut self, slot: Slot<T>, entity: T) -> Entity<T>
95 where
96 T: 'static,
97 {
98 let mut accessed_entities = self.accessed_entities.borrow_mut();
99 accessed_entities.insert(slot.entity_id);
100
101 let handle = slot.0;
102 self.entities.insert(handle.entity_id, Box::new(entity));
103 handle
104 }
105
106 /// Move an entity to the stack.
107 #[track_caller]
108 pub fn lease<T>(&mut self, pointer: &Entity<T>) -> Lease<T> {
109 self.assert_valid_context(pointer);
110 let mut accessed_entities = self.accessed_entities.borrow_mut();
111 accessed_entities.insert(pointer.entity_id);
112
113 let entity = Some(
114 self.entities
115 .remove(pointer.entity_id)
116 .unwrap_or_else(|| double_lease_panic::<T>("update")),
117 );
118 Lease {
119 entity,
120 id: pointer.entity_id,
121 entity_type: PhantomData,
122 }
123 }
124
125 /// Returns an entity after moving it to the stack.
126 pub fn end_lease<T>(&mut self, mut lease: Lease<T>) {
127 self.entities.insert(lease.id, lease.entity.take().unwrap());
128 }
129
130 pub fn read<T: 'static>(&self, entity: &Entity<T>) -> &T {
131 self.assert_valid_context(entity);
132 let mut accessed_entities = self.accessed_entities.borrow_mut();
133 accessed_entities.insert(entity.entity_id);
134
135 self.entities
136 .get(entity.entity_id)
137 .and_then(|entity| entity.downcast_ref())
138 .unwrap_or_else(|| double_lease_panic::<T>("read"))
139 }
140
141 fn assert_valid_context(&self, entity: &AnyEntity) {
142 debug_assert!(
143 Weak::ptr_eq(&entity.entity_map, &Arc::downgrade(&self.ref_counts)),
144 "used a entity with the wrong context"
145 );
146 }
147
148 pub fn extend_accessed(&mut self, entities: &FxHashSet<EntityId>) {
149 self.accessed_entities
150 .borrow_mut()
151 .extend(entities.iter().copied());
152 }
153
154 pub fn clear_accessed(&mut self) {
155 self.accessed_entities.borrow_mut().clear();
156 }
157
158 pub fn take_dropped(&mut self) -> Vec<(EntityId, Box<dyn Any>)> {
159 let mut ref_counts = self.ref_counts.write();
160 let dropped_entity_ids = mem::take(&mut ref_counts.dropped_entity_ids);
161 let mut accessed_entities = self.accessed_entities.borrow_mut();
162
163 dropped_entity_ids
164 .into_iter()
165 .filter_map(|entity_id| {
166 let count = ref_counts.counts.remove(entity_id).unwrap();
167 debug_assert_eq!(
168 count.load(SeqCst),
169 0,
170 "dropped an entity that was referenced"
171 );
172 accessed_entities.remove(&entity_id);
173 // If the EntityId was allocated with `Context::reserve`,
174 // the entity may not have been inserted.
175 Some((entity_id, self.entities.remove(entity_id)?))
176 })
177 .collect()
178 }
179}
180
181#[track_caller]
182fn double_lease_panic<T>(operation: &str) -> ! {
183 panic!(
184 "cannot {operation} {} while it is already being updated",
185 std::any::type_name::<T>()
186 )
187}
188
189pub(crate) struct Lease<T> {
190 entity: Option<Box<dyn Any>>,
191 pub id: EntityId,
192 entity_type: PhantomData<T>,
193}
194
195impl<T: 'static> core::ops::Deref for Lease<T> {
196 type Target = T;
197
198 fn deref(&self) -> &Self::Target {
199 self.entity.as_ref().unwrap().downcast_ref().unwrap()
200 }
201}
202
203impl<T: 'static> core::ops::DerefMut for Lease<T> {
204 fn deref_mut(&mut self) -> &mut Self::Target {
205 self.entity.as_mut().unwrap().downcast_mut().unwrap()
206 }
207}
208
209impl<T> Drop for Lease<T> {
210 fn drop(&mut self) {
211 if self.entity.is_some() && !panicking() {
212 panic!("Leases must be ended with EntityMap::end_lease")
213 }
214 }
215}
216
217#[derive(Deref, DerefMut)]
218pub(crate) struct Slot<T>(Entity<T>);
219
220/// A dynamically typed reference to a entity, which can be downcast into a `Entity<T>`.
221pub struct AnyEntity {
222 pub(crate) entity_id: EntityId,
223 pub(crate) entity_type: TypeId,
224 entity_map: Weak<RwLock<EntityRefCounts>>,
225 #[cfg(any(test, feature = "leak-detection"))]
226 handle_id: HandleId,
227}
228
229impl AnyEntity {
230 fn new(id: EntityId, entity_type: TypeId, entity_map: Weak<RwLock<EntityRefCounts>>) -> Self {
231 Self {
232 entity_id: id,
233 entity_type,
234 #[cfg(any(test, feature = "leak-detection"))]
235 handle_id: entity_map
236 .clone()
237 .upgrade()
238 .unwrap()
239 .write()
240 .leak_detector
241 .handle_created(id),
242 entity_map,
243 }
244 }
245
246 /// Returns the id associated with this entity.
247 #[inline]
248 pub fn entity_id(&self) -> EntityId {
249 self.entity_id
250 }
251
252 /// Returns the [TypeId] associated with this entity.
253 #[inline]
254 pub fn entity_type(&self) -> TypeId {
255 self.entity_type
256 }
257
258 /// Converts this entity handle into a weak variant, which does not prevent it from being released.
259 pub fn downgrade(&self) -> AnyWeakEntity {
260 AnyWeakEntity {
261 entity_id: self.entity_id,
262 entity_type: self.entity_type,
263 entity_ref_counts: self.entity_map.clone(),
264 }
265 }
266
267 /// Converts this entity handle into a strongly-typed entity handle of the given type.
268 /// If this entity handle is not of the specified type, returns itself as an error variant.
269 pub fn downcast<T: 'static>(self) -> Result<Entity<T>, AnyEntity> {
270 if TypeId::of::<T>() == self.entity_type {
271 Ok(Entity {
272 any_entity: self,
273 entity_type: PhantomData,
274 })
275 } else {
276 Err(self)
277 }
278 }
279}
280
281impl Clone for AnyEntity {
282 fn clone(&self) -> Self {
283 if let Some(entity_map) = self.entity_map.upgrade() {
284 let entity_map = entity_map.read();
285 let count = entity_map
286 .counts
287 .get(self.entity_id)
288 .expect("detected over-release of a entity");
289 let prev_count = count.fetch_add(1, SeqCst);
290 assert_ne!(prev_count, 0, "Detected over-release of a entity.");
291 }
292
293 Self {
294 entity_id: self.entity_id,
295 entity_type: self.entity_type,
296 entity_map: self.entity_map.clone(),
297 #[cfg(any(test, feature = "leak-detection"))]
298 handle_id: self
299 .entity_map
300 .upgrade()
301 .unwrap()
302 .write()
303 .leak_detector
304 .handle_created(self.entity_id),
305 }
306 }
307}
308
309impl Drop for AnyEntity {
310 fn drop(&mut self) {
311 if let Some(entity_map) = self.entity_map.upgrade() {
312 let entity_map = entity_map.upgradable_read();
313 let count = entity_map
314 .counts
315 .get(self.entity_id)
316 .expect("detected over-release of a handle.");
317 let prev_count = count.fetch_sub(1, SeqCst);
318 assert_ne!(prev_count, 0, "Detected over-release of a entity.");
319 if prev_count == 1 {
320 // We were the last reference to this entity, so we can remove it.
321 let mut entity_map = RwLockUpgradableReadGuard::upgrade(entity_map);
322 entity_map.dropped_entity_ids.push(self.entity_id);
323 }
324 }
325
326 #[cfg(any(test, feature = "leak-detection"))]
327 if let Some(entity_map) = self.entity_map.upgrade() {
328 entity_map
329 .write()
330 .leak_detector
331 .handle_released(self.entity_id, self.handle_id)
332 }
333 }
334}
335
336impl<T> From<Entity<T>> for AnyEntity {
337 #[inline]
338 fn from(entity: Entity<T>) -> Self {
339 entity.any_entity
340 }
341}
342
343impl Hash for AnyEntity {
344 #[inline]
345 fn hash<H: Hasher>(&self, state: &mut H) {
346 self.entity_id.hash(state);
347 }
348}
349
350impl PartialEq for AnyEntity {
351 #[inline]
352 fn eq(&self, other: &Self) -> bool {
353 self.entity_id == other.entity_id
354 }
355}
356
357impl Eq for AnyEntity {}
358
359impl Ord for AnyEntity {
360 #[inline]
361 fn cmp(&self, other: &Self) -> Ordering {
362 self.entity_id.cmp(&other.entity_id)
363 }
364}
365
366impl PartialOrd for AnyEntity {
367 #[inline]
368 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
369 Some(self.cmp(other))
370 }
371}
372
373impl std::fmt::Debug for AnyEntity {
374 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
375 f.debug_struct("AnyEntity")
376 .field("entity_id", &self.entity_id.as_u64())
377 .finish()
378 }
379}
380
381/// A strong, well-typed reference to a struct which is managed
382/// by GPUI
383#[derive(Deref, DerefMut)]
384pub struct Entity<T> {
385 #[deref]
386 #[deref_mut]
387 pub(crate) any_entity: AnyEntity,
388 pub(crate) entity_type: PhantomData<fn(T) -> T>,
389}
390
391impl<T> Sealed for Entity<T> {}
392
393impl<T: 'static> Entity<T> {
394 #[inline]
395 fn new(id: EntityId, entity_map: Weak<RwLock<EntityRefCounts>>) -> Self
396 where
397 T: 'static,
398 {
399 Self {
400 any_entity: AnyEntity::new(id, TypeId::of::<T>(), entity_map),
401 entity_type: PhantomData,
402 }
403 }
404
405 /// Get the entity ID associated with this entity
406 #[inline]
407 pub fn entity_id(&self) -> EntityId {
408 self.any_entity.entity_id
409 }
410
411 /// Downgrade this entity pointer to a non-retaining weak pointer
412 #[inline]
413 pub fn downgrade(&self) -> WeakEntity<T> {
414 WeakEntity {
415 any_entity: self.any_entity.downgrade(),
416 entity_type: self.entity_type,
417 }
418 }
419
420 /// Convert this into a dynamically typed entity.
421 #[inline]
422 pub fn into_any(self) -> AnyEntity {
423 self.any_entity
424 }
425
426 /// Grab a reference to this entity from the context.
427 #[inline]
428 pub fn read<'a>(&self, cx: &'a App) -> &'a T {
429 cx.entities.read(self)
430 }
431
432 /// Read the entity referenced by this handle with the given function.
433 #[inline]
434 pub fn read_with<R, C: AppContext>(
435 &self,
436 cx: &C,
437 f: impl FnOnce(&T, &App) -> R,
438 ) -> C::Result<R> {
439 cx.read_entity(self, f)
440 }
441
442 /// Updates the entity referenced by this handle with the given function.
443 #[inline]
444 pub fn update<R, C: AppContext>(
445 &self,
446 cx: &mut C,
447 update: impl FnOnce(&mut T, &mut Context<T>) -> R,
448 ) -> C::Result<R> {
449 cx.update_entity(self, update)
450 }
451
452 /// Updates the entity referenced by this handle with the given function.
453 #[inline]
454 pub fn as_mut<'a, C: AppContext>(&self, cx: &'a mut C) -> C::Result<GpuiBorrow<'a, T>> {
455 cx.as_mut(self)
456 }
457
458 /// Updates the entity referenced by this handle with the given function.
459 pub fn write<C: AppContext>(&self, cx: &mut C, value: T) -> C::Result<()> {
460 self.update(cx, |entity, cx| {
461 *entity = value;
462 cx.notify();
463 })
464 }
465
466 /// Updates the entity referenced by this handle with the given function if
467 /// the referenced entity still exists, within a visual context that has a window.
468 /// Returns an error if the entity has been released.
469 #[inline]
470 pub fn update_in<R, C: VisualContext>(
471 &self,
472 cx: &mut C,
473 update: impl FnOnce(&mut T, &mut Window, &mut Context<T>) -> R,
474 ) -> C::Result<R> {
475 cx.update_window_entity(self, update)
476 }
477}
478
479impl<T> Clone for Entity<T> {
480 #[inline]
481 fn clone(&self) -> Self {
482 Self {
483 any_entity: self.any_entity.clone(),
484 entity_type: self.entity_type,
485 }
486 }
487}
488
489impl<T> std::fmt::Debug for Entity<T> {
490 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
491 f.debug_struct("Entity")
492 .field("entity_id", &self.any_entity.entity_id)
493 .field("entity_type", &type_name::<T>())
494 .finish()
495 }
496}
497
498impl<T> Hash for Entity<T> {
499 #[inline]
500 fn hash<H: Hasher>(&self, state: &mut H) {
501 self.any_entity.hash(state);
502 }
503}
504
505impl<T> PartialEq for Entity<T> {
506 #[inline]
507 fn eq(&self, other: &Self) -> bool {
508 self.any_entity == other.any_entity
509 }
510}
511
512impl<T> Eq for Entity<T> {}
513
514impl<T> PartialEq<WeakEntity<T>> for Entity<T> {
515 #[inline]
516 fn eq(&self, other: &WeakEntity<T>) -> bool {
517 self.any_entity.entity_id() == other.entity_id()
518 }
519}
520
521impl<T: 'static> Ord for Entity<T> {
522 #[inline]
523 fn cmp(&self, other: &Self) -> std::cmp::Ordering {
524 self.entity_id().cmp(&other.entity_id())
525 }
526}
527
528impl<T: 'static> PartialOrd for Entity<T> {
529 #[inline]
530 fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
531 Some(self.cmp(other))
532 }
533}
534
535/// A type erased, weak reference to a entity.
536#[derive(Clone)]
537pub struct AnyWeakEntity {
538 pub(crate) entity_id: EntityId,
539 entity_type: TypeId,
540 entity_ref_counts: Weak<RwLock<EntityRefCounts>>,
541}
542
543impl AnyWeakEntity {
544 /// Get the entity ID associated with this weak reference.
545 #[inline]
546 pub fn entity_id(&self) -> EntityId {
547 self.entity_id
548 }
549
550 /// Check if this weak handle can be upgraded, or if the entity has already been dropped
551 pub fn is_upgradable(&self) -> bool {
552 let ref_count = self
553 .entity_ref_counts
554 .upgrade()
555 .and_then(|ref_counts| Some(ref_counts.read().counts.get(self.entity_id)?.load(SeqCst)))
556 .unwrap_or(0);
557 ref_count > 0
558 }
559
560 /// Upgrade this weak entity reference to a strong reference.
561 pub fn upgrade(&self) -> Option<AnyEntity> {
562 let ref_counts = &self.entity_ref_counts.upgrade()?;
563 let ref_counts = ref_counts.read();
564 let ref_count = ref_counts.counts.get(self.entity_id)?;
565
566 if atomic_incr_if_not_zero(ref_count) == 0 {
567 // entity_id is in dropped_entity_ids
568 return None;
569 }
570 drop(ref_counts);
571
572 Some(AnyEntity {
573 entity_id: self.entity_id,
574 entity_type: self.entity_type,
575 entity_map: self.entity_ref_counts.clone(),
576 #[cfg(any(test, feature = "leak-detection"))]
577 handle_id: self
578 .entity_ref_counts
579 .upgrade()
580 .unwrap()
581 .write()
582 .leak_detector
583 .handle_created(self.entity_id),
584 })
585 }
586
587 /// Assert that entity referenced by this weak handle has been released.
588 #[cfg(any(test, feature = "leak-detection"))]
589 pub fn assert_released(&self) {
590 self.entity_ref_counts
591 .upgrade()
592 .unwrap()
593 .write()
594 .leak_detector
595 .assert_released(self.entity_id);
596
597 if self
598 .entity_ref_counts
599 .upgrade()
600 .and_then(|ref_counts| Some(ref_counts.read().counts.get(self.entity_id)?.load(SeqCst)))
601 .is_some()
602 {
603 panic!(
604 "entity was recently dropped but resources are retained until the end of the effect cycle."
605 )
606 }
607 }
608
609 /// Creates a weak entity that can never be upgraded.
610 pub fn new_invalid() -> Self {
611 /// To hold the invariant that all ids are unique, and considering that slotmap
612 /// increases their IDs from `0`, we can decrease ours from `u64::MAX` so these
613 /// two will never conflict (u64 is way too large).
614 static UNIQUE_NON_CONFLICTING_ID_GENERATOR: AtomicU64 = AtomicU64::new(u64::MAX);
615 let entity_id = UNIQUE_NON_CONFLICTING_ID_GENERATOR.fetch_sub(1, SeqCst);
616
617 Self {
618 // Safety:
619 // Docs say this is safe but can be unspecified if slotmap changes the representation
620 // after `1.0.7`, that said, providing a valid entity_id here is not necessary as long
621 // as we guarantee that `entity_id` is never used if `entity_ref_counts` equals
622 // to `Weak::new()` (that is, it's unable to upgrade), that is the invariant that
623 // actually needs to be hold true.
624 //
625 // And there is no sane reason to read an entity slot if `entity_ref_counts` can't be
626 // read in the first place, so we're good!
627 entity_id: entity_id.into(),
628 entity_type: TypeId::of::<()>(),
629 entity_ref_counts: Weak::new(),
630 }
631 }
632}
633
634impl std::fmt::Debug for AnyWeakEntity {
635 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
636 f.debug_struct(type_name::<Self>())
637 .field("entity_id", &self.entity_id)
638 .field("entity_type", &self.entity_type)
639 .finish()
640 }
641}
642
643impl<T> From<WeakEntity<T>> for AnyWeakEntity {
644 #[inline]
645 fn from(entity: WeakEntity<T>) -> Self {
646 entity.any_entity
647 }
648}
649
650impl Hash for AnyWeakEntity {
651 #[inline]
652 fn hash<H: Hasher>(&self, state: &mut H) {
653 self.entity_id.hash(state);
654 }
655}
656
657impl PartialEq for AnyWeakEntity {
658 #[inline]
659 fn eq(&self, other: &Self) -> bool {
660 self.entity_id == other.entity_id
661 }
662}
663
664impl Eq for AnyWeakEntity {}
665
666impl Ord for AnyWeakEntity {
667 #[inline]
668 fn cmp(&self, other: &Self) -> Ordering {
669 self.entity_id.cmp(&other.entity_id)
670 }
671}
672
673impl PartialOrd for AnyWeakEntity {
674 #[inline]
675 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
676 Some(self.cmp(other))
677 }
678}
679
680/// A weak reference to a entity of the given type.
681#[derive(Deref, DerefMut)]
682pub struct WeakEntity<T> {
683 #[deref]
684 #[deref_mut]
685 any_entity: AnyWeakEntity,
686 entity_type: PhantomData<fn(T) -> T>,
687}
688
689impl<T> std::fmt::Debug for WeakEntity<T> {
690 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
691 f.debug_struct(type_name::<Self>())
692 .field("entity_id", &self.any_entity.entity_id)
693 .field("entity_type", &type_name::<T>())
694 .finish()
695 }
696}
697
698impl<T> Clone for WeakEntity<T> {
699 fn clone(&self) -> Self {
700 Self {
701 any_entity: self.any_entity.clone(),
702 entity_type: self.entity_type,
703 }
704 }
705}
706
707impl<T: 'static> WeakEntity<T> {
708 /// Upgrade this weak entity reference into a strong entity reference
709 pub fn upgrade(&self) -> Option<Entity<T>> {
710 Some(Entity {
711 any_entity: self.any_entity.upgrade()?,
712 entity_type: self.entity_type,
713 })
714 }
715
716 /// Updates the entity referenced by this handle with the given function if
717 /// the referenced entity still exists. Returns an error if the entity has
718 /// been released.
719 pub fn update<C, R>(
720 &self,
721 cx: &mut C,
722 update: impl FnOnce(&mut T, &mut Context<T>) -> R,
723 ) -> Result<R>
724 where
725 C: AppContext,
726 Result<C::Result<R>>: crate::Flatten<R>,
727 {
728 crate::Flatten::flatten(
729 self.upgrade()
730 .context("entity released")
731 .map(|this| cx.update_entity(&this, update)),
732 )
733 }
734
735 /// Updates the entity referenced by this handle with the given function if
736 /// the referenced entity still exists, within a visual context that has a window.
737 /// Returns an error if the entity has been released.
738 pub fn update_in<C, R>(
739 &self,
740 cx: &mut C,
741 update: impl FnOnce(&mut T, &mut Window, &mut Context<T>) -> R,
742 ) -> Result<R>
743 where
744 C: VisualContext,
745 Result<C::Result<R>>: crate::Flatten<R>,
746 {
747 let window = cx.window_handle();
748 let this = self.upgrade().context("entity released")?;
749
750 crate::Flatten::flatten(window.update(cx, |_, window, cx| {
751 this.update(cx, |entity, cx| update(entity, window, cx))
752 }))
753 }
754
755 /// Reads the entity referenced by this handle with the given function if
756 /// the referenced entity still exists. Returns an error if the entity has
757 /// been released.
758 pub fn read_with<C, R>(&self, cx: &C, read: impl FnOnce(&T, &App) -> R) -> Result<R>
759 where
760 C: AppContext,
761 Result<C::Result<R>>: crate::Flatten<R>,
762 {
763 crate::Flatten::flatten(
764 self.upgrade()
765 .context("entity released")
766 .map(|this| cx.read_entity(&this, read)),
767 )
768 }
769
770 /// Create a new weak entity that can never be upgraded.
771 #[inline]
772 pub fn new_invalid() -> Self {
773 Self {
774 any_entity: AnyWeakEntity::new_invalid(),
775 entity_type: PhantomData,
776 }
777 }
778}
779
780impl<T> Hash for WeakEntity<T> {
781 #[inline]
782 fn hash<H: Hasher>(&self, state: &mut H) {
783 self.any_entity.hash(state);
784 }
785}
786
787impl<T> PartialEq for WeakEntity<T> {
788 #[inline]
789 fn eq(&self, other: &Self) -> bool {
790 self.any_entity == other.any_entity
791 }
792}
793
794impl<T> Eq for WeakEntity<T> {}
795
796impl<T> PartialEq<Entity<T>> for WeakEntity<T> {
797 #[inline]
798 fn eq(&self, other: &Entity<T>) -> bool {
799 self.entity_id() == other.any_entity.entity_id()
800 }
801}
802
803impl<T: 'static> Ord for WeakEntity<T> {
804 #[inline]
805 fn cmp(&self, other: &Self) -> Ordering {
806 self.entity_id().cmp(&other.entity_id())
807 }
808}
809
810impl<T: 'static> PartialOrd for WeakEntity<T> {
811 #[inline]
812 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
813 Some(self.cmp(other))
814 }
815}
816
817#[cfg(any(test, feature = "leak-detection"))]
818static LEAK_BACKTRACE: std::sync::LazyLock<bool> =
819 std::sync::LazyLock::new(|| std::env::var("LEAK_BACKTRACE").is_ok_and(|b| !b.is_empty()));
820
821#[cfg(any(test, feature = "leak-detection"))]
822#[derive(Clone, Copy, Debug, Default, Hash, PartialEq, Eq)]
823pub(crate) struct HandleId {
824 id: u64, // id of the handle itself, not the pointed at object
825}
826
827#[cfg(any(test, feature = "leak-detection"))]
828pub(crate) struct LeakDetector {
829 next_handle_id: u64,
830 entity_handles: HashMap<EntityId, HashMap<HandleId, Option<backtrace::Backtrace>>>,
831}
832
833#[cfg(any(test, feature = "leak-detection"))]
834impl LeakDetector {
835 #[track_caller]
836 pub fn handle_created(&mut self, entity_id: EntityId) -> HandleId {
837 let id = util::post_inc(&mut self.next_handle_id);
838 let handle_id = HandleId { id };
839 let handles = self.entity_handles.entry(entity_id).or_default();
840 handles.insert(
841 handle_id,
842 LEAK_BACKTRACE.then(backtrace::Backtrace::new_unresolved),
843 );
844 handle_id
845 }
846
847 pub fn handle_released(&mut self, entity_id: EntityId, handle_id: HandleId) {
848 let handles = self.entity_handles.entry(entity_id).or_default();
849 handles.remove(&handle_id);
850 }
851
852 pub fn assert_released(&mut self, entity_id: EntityId) {
853 let handles = self.entity_handles.entry(entity_id).or_default();
854 if !handles.is_empty() {
855 for backtrace in handles.values_mut() {
856 if let Some(mut backtrace) = backtrace.take() {
857 backtrace.resolve();
858 eprintln!("Leaked handle: {:#?}", backtrace);
859 } else {
860 eprintln!("Leaked handle: export LEAK_BACKTRACE to find allocation site");
861 }
862 }
863 panic!();
864 }
865 }
866}
867
868#[cfg(test)]
869mod test {
870 use crate::EntityMap;
871
872 struct TestEntity {
873 pub i: i32,
874 }
875
876 #[test]
877 fn test_entity_map_slot_assignment_before_cleanup() {
878 // Tests that slots are not re-used before take_dropped.
879 let mut entity_map = EntityMap::new();
880
881 let slot = entity_map.reserve::<TestEntity>();
882 entity_map.insert(slot, TestEntity { i: 1 });
883
884 let slot = entity_map.reserve::<TestEntity>();
885 entity_map.insert(slot, TestEntity { i: 2 });
886
887 let dropped = entity_map.take_dropped();
888 assert_eq!(dropped.len(), 2);
889
890 assert_eq!(
891 dropped
892 .into_iter()
893 .map(|(_, entity)| entity.downcast::<TestEntity>().unwrap().i)
894 .collect::<Vec<i32>>(),
895 vec![1, 2],
896 );
897 }
898
899 #[test]
900 fn test_entity_map_weak_upgrade_before_cleanup() {
901 // Tests that weak handles are not upgraded before take_dropped
902 let mut entity_map = EntityMap::new();
903
904 let slot = entity_map.reserve::<TestEntity>();
905 let handle = entity_map.insert(slot, TestEntity { i: 1 });
906 let weak = handle.downgrade();
907 drop(handle);
908
909 let strong = weak.upgrade();
910 assert_eq!(strong, None);
911
912 let dropped = entity_map.take_dropped();
913 assert_eq!(dropped.len(), 1);
914
915 assert_eq!(
916 dropped
917 .into_iter()
918 .map(|(_, entity)| entity.downcast::<TestEntity>().unwrap().i)
919 .collect::<Vec<i32>>(),
920 vec![1],
921 );
922 }
923}