1use crate::{private::Sealed, AnyBox, AppContext, Context, Entity, ModelContext};
2use anyhow::{anyhow, Result};
3use derive_more::{Deref, DerefMut};
4use parking_lot::{RwLock, RwLockUpgradableReadGuard};
5use slotmap::{SecondaryMap, SlotMap};
6use std::{
7 any::{type_name, TypeId},
8 fmt::{self, Display},
9 hash::{Hash, Hasher},
10 marker::PhantomData,
11 mem,
12 sync::{
13 atomic::{AtomicUsize, Ordering::SeqCst},
14 Arc, Weak,
15 },
16};
17
18slotmap::new_key_type! { pub struct EntityId; }
19
20impl EntityId {
21 pub fn as_u64(self) -> u64 {
22 self.0.as_ffi()
23 }
24}
25
26impl Display for EntityId {
27 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
28 write!(f, "{}", self)
29 }
30}
31
32pub(crate) struct EntityMap {
33 entities: SecondaryMap<EntityId, AnyBox>,
34 ref_counts: Arc<RwLock<EntityRefCounts>>,
35}
36
37struct EntityRefCounts {
38 counts: SlotMap<EntityId, AtomicUsize>,
39 dropped_entity_ids: Vec<EntityId>,
40}
41
42impl EntityMap {
43 pub fn new() -> Self {
44 Self {
45 entities: SecondaryMap::new(),
46 ref_counts: Arc::new(RwLock::new(EntityRefCounts {
47 counts: SlotMap::with_key(),
48 dropped_entity_ids: Vec::new(),
49 })),
50 }
51 }
52
53 /// Reserve a slot for an entity, which you can subsequently use with `insert`.
54 pub fn reserve<T: 'static>(&self) -> Slot<T> {
55 let id = self.ref_counts.write().counts.insert(1.into());
56 Slot(Model::new(id, Arc::downgrade(&self.ref_counts)))
57 }
58
59 /// Insert an entity into a slot obtained by calling `reserve`.
60 pub fn insert<T>(&mut self, slot: Slot<T>, entity: T) -> Model<T>
61 where
62 T: 'static,
63 {
64 let model = slot.0;
65 self.entities.insert(model.entity_id, Box::new(entity));
66 model
67 }
68
69 /// Move an entity to the stack.
70 pub fn lease<'a, T>(&mut self, model: &'a Model<T>) -> Lease<'a, T> {
71 self.assert_valid_context(model);
72 let entity = Some(
73 self.entities
74 .remove(model.entity_id)
75 .expect("Circular entity lease. Is the entity already being updated?"),
76 );
77 Lease {
78 model,
79 entity,
80 entity_type: PhantomData,
81 }
82 }
83
84 /// Return an entity after moving it to the stack.
85 pub fn end_lease<T>(&mut self, mut lease: Lease<T>) {
86 self.entities
87 .insert(lease.model.entity_id, lease.entity.take().unwrap());
88 }
89
90 pub fn read<T: 'static>(&self, model: &Model<T>) -> &T {
91 self.assert_valid_context(model);
92 self.entities[model.entity_id].downcast_ref().unwrap()
93 }
94
95 fn assert_valid_context(&self, model: &AnyModel) {
96 debug_assert!(
97 Weak::ptr_eq(&model.entity_map, &Arc::downgrade(&self.ref_counts)),
98 "used a model with the wrong context"
99 );
100 }
101
102 pub fn take_dropped(&mut self) -> Vec<(EntityId, AnyBox)> {
103 let mut ref_counts = self.ref_counts.write();
104 let dropped_entity_ids = mem::take(&mut ref_counts.dropped_entity_ids);
105
106 dropped_entity_ids
107 .into_iter()
108 .map(|entity_id| {
109 let count = ref_counts.counts.remove(entity_id).unwrap();
110 debug_assert_eq!(
111 count.load(SeqCst),
112 0,
113 "dropped an entity that was referenced"
114 );
115 (entity_id, self.entities.remove(entity_id).unwrap())
116 })
117 .collect()
118 }
119}
120
121pub struct Lease<'a, T> {
122 entity: Option<AnyBox>,
123 pub model: &'a Model<T>,
124 entity_type: PhantomData<T>,
125}
126
127impl<'a, T: 'static> core::ops::Deref for Lease<'a, T> {
128 type Target = T;
129
130 fn deref(&self) -> &Self::Target {
131 self.entity.as_ref().unwrap().downcast_ref().unwrap()
132 }
133}
134
135impl<'a, T: 'static> core::ops::DerefMut for Lease<'a, T> {
136 fn deref_mut(&mut self) -> &mut Self::Target {
137 self.entity.as_mut().unwrap().downcast_mut().unwrap()
138 }
139}
140
141impl<'a, T> Drop for Lease<'a, T> {
142 fn drop(&mut self) {
143 if self.entity.is_some() {
144 // We don't panic here, because other panics can cause us to drop the lease without ending it cleanly.
145 log::error!("Leases must be ended with EntityMap::end_lease")
146 }
147 }
148}
149
150#[derive(Deref, DerefMut)]
151pub struct Slot<T>(Model<T>);
152
153pub struct AnyModel {
154 pub(crate) entity_id: EntityId,
155 pub(crate) entity_type: TypeId,
156 entity_map: Weak<RwLock<EntityRefCounts>>,
157}
158
159impl AnyModel {
160 fn new(id: EntityId, entity_type: TypeId, entity_map: Weak<RwLock<EntityRefCounts>>) -> Self {
161 Self {
162 entity_id: id,
163 entity_type,
164 entity_map,
165 }
166 }
167
168 pub fn entity_id(&self) -> EntityId {
169 self.entity_id
170 }
171
172 // todo!() added for populating `ProjectItemBuilders` in `load_path` method
173 pub fn type_id(&self) -> TypeId {
174 self.entity_type
175 }
176
177 pub fn downgrade(&self) -> AnyWeakModel {
178 AnyWeakModel {
179 entity_id: self.entity_id,
180 entity_type: self.entity_type,
181 entity_ref_counts: self.entity_map.clone(),
182 }
183 }
184
185 pub fn downcast<T: 'static>(self) -> Result<Model<T>, AnyModel> {
186 if TypeId::of::<T>() == self.entity_type {
187 Ok(Model {
188 any_model: self,
189 entity_type: PhantomData,
190 })
191 } else {
192 Err(self)
193 }
194 }
195}
196
197impl Clone for AnyModel {
198 fn clone(&self) -> Self {
199 if let Some(entity_map) = self.entity_map.upgrade() {
200 let entity_map = entity_map.read();
201 let count = entity_map
202 .counts
203 .get(self.entity_id)
204 .expect("detected over-release of a model");
205 let prev_count = count.fetch_add(1, SeqCst);
206 assert_ne!(prev_count, 0, "Detected over-release of a model.");
207 }
208
209 Self {
210 entity_id: self.entity_id,
211 entity_type: self.entity_type,
212 entity_map: self.entity_map.clone(),
213 }
214 }
215}
216
217impl Drop for AnyModel {
218 fn drop(&mut self) {
219 if let Some(entity_map) = self.entity_map.upgrade() {
220 let entity_map = entity_map.upgradable_read();
221 let count = entity_map
222 .counts
223 .get(self.entity_id)
224 .expect("detected over-release of a handle.");
225 let prev_count = count.fetch_sub(1, SeqCst);
226 assert_ne!(prev_count, 0, "Detected over-release of a model.");
227 if prev_count == 1 {
228 // We were the last reference to this entity, so we can remove it.
229 let mut entity_map = RwLockUpgradableReadGuard::upgrade(entity_map);
230 entity_map.dropped_entity_ids.push(self.entity_id);
231 }
232 }
233 }
234}
235
236impl<T> From<Model<T>> for AnyModel {
237 fn from(model: Model<T>) -> Self {
238 model.any_model
239 }
240}
241
242impl Hash for AnyModel {
243 fn hash<H: Hasher>(&self, state: &mut H) {
244 self.entity_id.hash(state);
245 }
246}
247
248impl PartialEq for AnyModel {
249 fn eq(&self, other: &Self) -> bool {
250 self.entity_id == other.entity_id
251 }
252}
253
254impl Eq for AnyModel {}
255
256impl std::fmt::Debug for AnyModel {
257 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
258 f.debug_struct("AnyModel")
259 .field("entity_id", &self.entity_id.as_u64())
260 .finish()
261 }
262}
263
264#[derive(Deref, DerefMut)]
265pub struct Model<T> {
266 #[deref]
267 #[deref_mut]
268 pub(crate) any_model: AnyModel,
269 pub(crate) entity_type: PhantomData<T>,
270}
271
272unsafe impl<T> Send for Model<T> {}
273unsafe impl<T> Sync for Model<T> {}
274impl<T> Sealed for Model<T> {}
275
276impl<T: 'static> Entity<T> for Model<T> {
277 type Weak = WeakModel<T>;
278
279 fn entity_id(&self) -> EntityId {
280 self.any_model.entity_id
281 }
282
283 fn downgrade(&self) -> Self::Weak {
284 WeakModel {
285 any_model: self.any_model.downgrade(),
286 entity_type: self.entity_type,
287 }
288 }
289
290 fn upgrade_from(weak: &Self::Weak) -> Option<Self>
291 where
292 Self: Sized,
293 {
294 Some(Model {
295 any_model: weak.any_model.upgrade()?,
296 entity_type: weak.entity_type,
297 })
298 }
299}
300
301impl<T: 'static> Model<T> {
302 fn new(id: EntityId, entity_map: Weak<RwLock<EntityRefCounts>>) -> Self
303 where
304 T: 'static,
305 {
306 Self {
307 any_model: AnyModel::new(id, TypeId::of::<T>(), entity_map),
308 entity_type: PhantomData,
309 }
310 }
311
312 /// Downgrade the this to a weak model reference
313 pub fn downgrade(&self) -> WeakModel<T> {
314 // Delegate to the trait implementation to keep behavior in one place.
315 // This method was included to improve method resolution in the presence of
316 // the Model's deref
317 Entity::downgrade(self)
318 }
319
320 /// Convert this into a dynamically typed model.
321 pub fn into_any(self) -> AnyModel {
322 self.any_model
323 }
324
325 pub fn read<'a>(&self, cx: &'a AppContext) -> &'a T {
326 cx.entities.read(self)
327 }
328
329 /// Update the entity referenced by this model with the given function.
330 ///
331 /// The update function receives a context appropriate for its environment.
332 /// When updating in an `AppContext`, it receives a `ModelContext`.
333 /// When updating an a `WindowContext`, it receives a `ViewContext`.
334 pub fn update<C, R>(
335 &self,
336 cx: &mut C,
337 update: impl FnOnce(&mut T, &mut ModelContext<'_, T>) -> R,
338 ) -> C::Result<R>
339 where
340 C: Context,
341 {
342 cx.update_model(self, update)
343 }
344}
345
346impl<T> Clone for Model<T> {
347 fn clone(&self) -> Self {
348 Self {
349 any_model: self.any_model.clone(),
350 entity_type: self.entity_type,
351 }
352 }
353}
354
355impl<T> std::fmt::Debug for Model<T> {
356 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
357 write!(
358 f,
359 "Model {{ entity_id: {:?}, entity_type: {:?} }}",
360 self.any_model.entity_id,
361 type_name::<T>()
362 )
363 }
364}
365
366impl<T> Hash for Model<T> {
367 fn hash<H: Hasher>(&self, state: &mut H) {
368 self.any_model.hash(state);
369 }
370}
371
372impl<T> PartialEq for Model<T> {
373 fn eq(&self, other: &Self) -> bool {
374 self.any_model == other.any_model
375 }
376}
377
378impl<T> Eq for Model<T> {}
379
380impl<T> PartialEq<WeakModel<T>> for Model<T> {
381 fn eq(&self, other: &WeakModel<T>) -> bool {
382 self.any_model.entity_id() == other.entity_id()
383 }
384}
385
386#[derive(Clone)]
387pub struct AnyWeakModel {
388 pub(crate) entity_id: EntityId,
389 entity_type: TypeId,
390 entity_ref_counts: Weak<RwLock<EntityRefCounts>>,
391}
392
393impl AnyWeakModel {
394 pub fn entity_id(&self) -> EntityId {
395 self.entity_id
396 }
397
398 pub fn is_upgradable(&self) -> bool {
399 let ref_count = self
400 .entity_ref_counts
401 .upgrade()
402 .and_then(|ref_counts| Some(ref_counts.read().counts.get(self.entity_id)?.load(SeqCst)))
403 .unwrap_or(0);
404 ref_count > 0
405 }
406
407 pub fn upgrade(&self) -> Option<AnyModel> {
408 let ref_counts = &self.entity_ref_counts.upgrade()?;
409 let ref_counts = ref_counts.read();
410 let ref_count = ref_counts.counts.get(self.entity_id)?;
411
412 // entity_id is in dropped_entity_ids
413 if ref_count.load(SeqCst) == 0 {
414 return None;
415 }
416 ref_count.fetch_add(1, SeqCst);
417
418 Some(AnyModel {
419 entity_id: self.entity_id,
420 entity_type: self.entity_type,
421 entity_map: self.entity_ref_counts.clone(),
422 })
423 }
424}
425
426impl<T> From<WeakModel<T>> for AnyWeakModel {
427 fn from(model: WeakModel<T>) -> Self {
428 model.any_model
429 }
430}
431
432impl Hash for AnyWeakModel {
433 fn hash<H: Hasher>(&self, state: &mut H) {
434 self.entity_id.hash(state);
435 }
436}
437
438impl PartialEq for AnyWeakModel {
439 fn eq(&self, other: &Self) -> bool {
440 self.entity_id == other.entity_id
441 }
442}
443
444impl Eq for AnyWeakModel {}
445
446#[derive(Deref, DerefMut)]
447pub struct WeakModel<T> {
448 #[deref]
449 #[deref_mut]
450 any_model: AnyWeakModel,
451 entity_type: PhantomData<T>,
452}
453
454impl<T> Clone for WeakModel<T> {
455 fn clone(&self) -> Self {
456 Self {
457 any_model: self.any_model.clone(),
458 entity_type: self.entity_type,
459 }
460 }
461}
462
463impl<T: 'static> WeakModel<T> {
464 /// Upgrade this weak model reference into a strong model reference
465 pub fn upgrade(&self) -> Option<Model<T>> {
466 // Delegate to the trait implementation to keep behavior in one place.
467 Model::upgrade_from(self)
468 }
469
470 /// Update the entity referenced by this model with the given function if
471 /// the referenced entity still exists. Returns an error if the entity has
472 /// been released.
473 ///
474 /// The update function receives a context appropriate for its environment.
475 /// When updating in an `AppContext`, it receives a `ModelContext`.
476 /// When updating an a `WindowContext`, it receives a `ViewContext`.
477 pub fn update<C, R>(
478 &self,
479 cx: &mut C,
480 update: impl FnOnce(&mut T, &mut ModelContext<'_, T>) -> R,
481 ) -> Result<R>
482 where
483 C: Context,
484 Result<C::Result<R>>: crate::Flatten<R>,
485 {
486 crate::Flatten::flatten(
487 self.upgrade()
488 .ok_or_else(|| anyhow!("entity release"))
489 .map(|this| cx.update_model(&this, update)),
490 )
491 }
492}
493
494impl<T> Hash for WeakModel<T> {
495 fn hash<H: Hasher>(&self, state: &mut H) {
496 self.any_model.hash(state);
497 }
498}
499
500impl<T> PartialEq for WeakModel<T> {
501 fn eq(&self, other: &Self) -> bool {
502 self.any_model == other.any_model
503 }
504}
505
506impl<T> Eq for WeakModel<T> {}
507
508impl<T> PartialEq<Model<T>> for WeakModel<T> {
509 fn eq(&self, other: &Model<T>) -> bool {
510 self.entity_id() == other.any_model.entity_id()
511 }
512}
513
514#[cfg(test)]
515mod test {
516 use crate::EntityMap;
517
518 struct TestEntity {
519 pub i: i32,
520 }
521
522 #[test]
523 fn test_entity_map_slot_assignment_before_cleanup() {
524 // Tests that slots are not re-used before take_dropped.
525 let mut entity_map = EntityMap::new();
526
527 let slot = entity_map.reserve::<TestEntity>();
528 entity_map.insert(slot, TestEntity { i: 1 });
529
530 let slot = entity_map.reserve::<TestEntity>();
531 entity_map.insert(slot, TestEntity { i: 2 });
532
533 let dropped = entity_map.take_dropped();
534 assert_eq!(dropped.len(), 2);
535
536 assert_eq!(
537 dropped
538 .into_iter()
539 .map(|(_, entity)| entity.downcast::<TestEntity>().unwrap().i)
540 .collect::<Vec<i32>>(),
541 vec![1, 2],
542 );
543 }
544
545 #[test]
546 fn test_entity_map_weak_upgrade_before_cleanup() {
547 // Tests that weak handles are not upgraded before take_dropped
548 let mut entity_map = EntityMap::new();
549
550 let slot = entity_map.reserve::<TestEntity>();
551 let handle = entity_map.insert(slot, TestEntity { i: 1 });
552 let weak = handle.downgrade();
553 drop(handle);
554
555 let strong = weak.upgrade();
556 assert_eq!(strong, None);
557
558 let dropped = entity_map.take_dropped();
559 assert_eq!(dropped.len(), 1);
560
561 assert_eq!(
562 dropped
563 .into_iter()
564 .map(|(_, entity)| entity.downcast::<TestEntity>().unwrap().i)
565 .collect::<Vec<i32>>(),
566 vec![1],
567 );
568 }
569}