Checkpoint

crates/gpui3/src/app.rs

@@ -67,6 +67,7 @@ impl App {
                 pending_effects: Default::default(),
                 observers: SubscriberSet::new(),
                 event_handlers: SubscriberSet::new(),
+                release_handlers: SubscriberSet::new(),
                 layout_id_buffer: Default::default(),
             })
         }))
@@ -88,6 +89,7 @@ impl App {
 
 type Handler = Box<dyn Fn(&mut AppContext) -> bool + Send + Sync + 'static>;
 type EventHandler = Box<dyn Fn(&dyn Any, &mut AppContext) -> bool + Send + Sync + 'static>;
+type ReleaseHandler = Box<dyn Fn(&mut dyn Any, &mut AppContext) + Send + Sync + 'static>;
 type FrameCallback = Box<dyn FnOnce(&mut WindowContext) + Send>;
 
 pub struct AppContext {
@@ -107,6 +109,7 @@ pub struct AppContext {
     pub(crate) pending_effects: VecDeque<Effect>,
     pub(crate) observers: SubscriberSet<EntityId, Handler>,
     pub(crate) event_handlers: SubscriberSet<EntityId, EventHandler>,
+    pub(crate) release_handlers: SubscriberSet<EntityId, ReleaseHandler>,
     pub(crate) layout_id_buffer: Vec<LayoutId>, // We recycle this memory across layout requests.
 }
 
@@ -146,10 +149,15 @@ impl AppContext {
     }
 
     fn flush_effects(&mut self) {
-        while let Some(effect) = self.pending_effects.pop_front() {
-            match effect {
-                Effect::Notify { emitter } => self.apply_notify_effect(emitter),
-                Effect::Emit { emitter, event } => self.apply_emit_effect(emitter, event),
+        loop {
+            self.release_dropped_entities();
+            if let Some(effect) = self.pending_effects.pop_front() {
+                match effect {
+                    Effect::Notify { emitter } => self.apply_notify_effect(emitter),
+                    Effect::Emit { emitter, event } => self.apply_emit_effect(emitter, event),
+                }
+            } else {
+                break;
             }
         }
 
@@ -171,6 +179,23 @@ impl AppContext {
         }
     }
 
+    fn release_dropped_entities(&mut self) {
+        loop {
+            let dropped = self.entities.take_dropped();
+            if dropped.is_empty() {
+                break;
+            }
+
+            for (entity_id, mut entity) in dropped {
+                self.observers.remove(&entity_id);
+                self.event_handlers.remove(&entity_id);
+                for release_callback in self.release_handlers.remove(&entity_id) {
+                    release_callback(&mut entity, self);
+                }
+            }
+        }
+    }
+
     fn apply_notify_effect(&mut self, emitter: EntityId) {
         self.observers
             .clone()

crates/gpui3/src/app/entity_map.rs

@@ -1,11 +1,12 @@
 use crate::Context;
 use anyhow::{anyhow, Result};
 use derive_more::{Deref, DerefMut};
-use parking_lot::{Mutex, RwLock};
+use parking_lot::{RwLock, RwLockUpgradableReadGuard};
 use slotmap::{SecondaryMap, SlotMap};
 use std::{
     any::Any,
     marker::PhantomData,
+    mem,
     sync::{
         atomic::{AtomicUsize, Ordering::SeqCst},
         Arc, Weak,
@@ -14,29 +15,33 @@ use std::{
 
 slotmap::new_key_type! { pub struct EntityId; }
 
-pub(crate) struct EntityMap {
-    ref_counts: Arc<RwLock<RefCounts>>,
-    entities: Arc<Mutex<SecondaryMap<EntityId, Box<dyn Any + Send + Sync>>>>,
+pub(crate) struct EntityMap(Arc<RwLock<EntityMapState>>);
+
+struct EntityMapState {
+    ref_counts: SlotMap<EntityId, AtomicUsize>,
+    entities: SecondaryMap<EntityId, Box<dyn Any + Send + Sync>>,
+    dropped_entities: Vec<(EntityId, Box<dyn Any + Send + Sync>)>,
 }
 
 impl EntityMap {
     pub fn new() -> Self {
-        Self {
-            ref_counts: Arc::new(RwLock::new(SlotMap::with_key())),
-            entities: Arc::new(Mutex::new(SecondaryMap::new())),
-        }
+        Self(Arc::new(RwLock::new(EntityMapState {
+            ref_counts: SlotMap::with_key(),
+            entities: SecondaryMap::new(),
+            dropped_entities: Vec::new(),
+        })))
     }
 
     /// Reserve a slot for an entity, which you can subsequently use with `insert`.
     pub fn reserve<T: 'static + Send + Sync>(&self) -> Slot<T> {
-        let id = self.ref_counts.write().insert(1.into());
-        Slot(Handle::new(id, Arc::downgrade(&self.ref_counts)))
+        let id = self.0.write().ref_counts.insert(1.into());
+        Slot(Handle::new(id, Arc::downgrade(&self.0)))
     }
 
     /// Insert an entity into a slot obtained by calling `reserve`.
     pub fn insert<T: 'static + Any + Send + Sync>(&self, slot: Slot<T>, entity: T) -> Handle<T> {
         let handle = slot.0;
-        self.entities.lock().insert(handle.id, Box::new(entity));
+        self.0.write().entities.insert(handle.id, Box::new(entity));
         handle
     }
 
@@ -44,8 +49,9 @@ impl EntityMap {
     pub fn lease<T: 'static + Send + Sync>(&self, handle: &Handle<T>) -> Lease<T> {
         let id = handle.id;
         let entity = Some(
-            self.entities
-                .lock()
+            self.0
+                .write()
+                .entities
                 .remove(id)
                 .expect("Circular entity lease. Is the entity already being updated?")
                 .downcast::<T>()
@@ -56,8 +62,9 @@ impl EntityMap {
 
     /// Return an entity after moving it to the stack.
     pub fn end_lease<T: 'static + Send + Sync>(&mut self, mut lease: Lease<T>) {
-        self.entities
-            .lock()
+        self.0
+            .write()
+            .entities
             .insert(lease.id, lease.entity.take().unwrap());
     }
 
@@ -65,9 +72,13 @@ impl EntityMap {
         WeakHandle {
             id,
             entity_type: PhantomData,
-            ref_counts: Arc::downgrade(&self.ref_counts),
+            entity_map: Arc::downgrade(&self.0),
         }
     }
+
+    pub fn take_dropped(&self) -> Vec<(EntityId, Box<dyn Any + Send + Sync>)> {
+        mem::take(&mut self.0.write().dropped_entities)
+    }
 }
 
 pub struct Lease<T> {
@@ -104,17 +115,15 @@ pub struct Slot<T: Send + Sync + 'static>(Handle<T>);
 pub struct Handle<T: Send + Sync> {
     pub(crate) id: EntityId,
     entity_type: PhantomData<T>,
-    ref_counts: Weak<RwLock<RefCounts>>,
+    entity_map: Weak<RwLock<EntityMapState>>,
 }
 
-type RefCounts = SlotMap<EntityId, AtomicUsize>;
-
 impl<T: 'static + Send + Sync> Handle<T> {
-    pub fn new(id: EntityId, ref_counts: Weak<RwLock<RefCounts>>) -> Self {
+    fn new(id: EntityId, entity_map: Weak<RwLock<EntityMapState>>) -> Self {
         Self {
             id,
             entity_type: PhantomData,
-            ref_counts,
+            entity_map,
         }
     }
 
@@ -122,7 +131,7 @@ impl<T: 'static + Send + Sync> Handle<T> {
         WeakHandle {
             id: self.id,
             entity_type: self.entity_type,
-            ref_counts: self.ref_counts.clone(),
+            entity_map: self.entity_map.clone(),
         }
     }
 
@@ -142,40 +151,66 @@ impl<T: 'static + Send + Sync> Handle<T> {
 
 impl<T: Send + Sync> Clone for Handle<T> {
     fn clone(&self) -> Self {
+        if let Some(entity_map) = self.entity_map.upgrade() {
+            let entity_map = entity_map.read();
+            let count = entity_map
+                .ref_counts
+                .get(self.id)
+                .expect("detected over-release of a handle");
+            let prev_count = count.fetch_add(1, SeqCst);
+            assert_ne!(prev_count, 0, "Detected over-release of a handle.");
+        }
+
         Self {
             id: self.id,
             entity_type: PhantomData,
-            ref_counts: self.ref_counts.clone(),
+            entity_map: self.entity_map.clone(),
         }
     }
 }
 
 impl<T: Send + Sync> Drop for Handle<T> {
     fn drop(&mut self) {
-        if let Some(_ref_counts) = self.ref_counts.upgrade() {
-            // todo!()
-            // if let Some(count) = ref_counts.read().get(self.id) {
-            //     let prev_count = count.fetch_sub(1, SeqCst);
-            //     assert_ne!(prev_count, 0, "Detected over-release of a handle.");
-            // }
+        if let Some(entity_map) = self.entity_map.upgrade() {
+            let entity_map = entity_map.upgradable_read();
+            let count = entity_map
+                .ref_counts
+                .get(self.id)
+                .expect("Detected over-release of a handle.");
+            let prev_count = count.fetch_sub(1, SeqCst);
+            assert_ne!(prev_count, 0, "Detected over-release of a handle.");
+            if prev_count == 1 {
+                // We were the last reference to this entity, so we can remove it.
+                let mut entity_map = RwLockUpgradableReadGuard::upgrade(entity_map);
+                let entity = entity_map
+                    .entities
+                    .remove(self.id)
+                    .expect("entity was removed twice");
+                entity_map.ref_counts.remove(self.id);
+                entity_map.dropped_entities.push((self.id, entity));
+            }
         }
     }
 }
 
 pub struct WeakHandle<T> {
     pub(crate) id: EntityId,
-    pub(crate) entity_type: PhantomData<T>,
-    pub(crate) ref_counts: Weak<RwLock<RefCounts>>,
+    entity_type: PhantomData<T>,
+    entity_map: Weak<RwLock<EntityMapState>>,
 }
 
 impl<T: Send + Sync + 'static> WeakHandle<T> {
     pub fn upgrade(&self, _: &impl Context) -> Option<Handle<T>> {
-        let ref_counts = self.ref_counts.upgrade()?;
-        ref_counts.read().get(self.id).unwrap().fetch_add(1, SeqCst);
+        let entity_map = &self.entity_map.upgrade()?;
+        entity_map
+            .read()
+            .ref_counts
+            .get(self.id)?
+            .fetch_add(1, SeqCst);
         Some(Handle {
             id: self.id,
             entity_type: self.entity_type,
-            ref_counts: self.ref_counts.clone(),
+            entity_map: self.entity_map.clone(),
         })
     }
 

crates/gpui3/src/app/model_context.rs

@@ -85,6 +85,36 @@ impl<'a, T: Send + Sync + 'static> ModelContext<'a, T> {
         )
     }
 
+    pub fn on_release(
+        &mut self,
+        on_release: impl Fn(&mut T, &mut AppContext) + Send + Sync + 'static,
+    ) -> Subscription {
+        self.app.release_handlers.insert(
+            self.entity_id,
+            Box::new(move |this, cx| {
+                let this = this.downcast_mut().expect("invalid entity type");
+                on_release(this, cx);
+            }),
+        )
+    }
+
+    pub fn observe_release<E: Send + Sync + 'static>(
+        &mut self,
+        handle: &Handle<E>,
+        on_release: impl Fn(&mut T, &mut E, &mut ModelContext<'_, T>) + Send + Sync + 'static,
+    ) -> Subscription {
+        let this = self.handle();
+        self.app.release_handlers.insert(
+            handle.id,
+            Box::new(move |entity, cx| {
+                let entity = entity.downcast_mut().expect("invalid entity type");
+                if let Some(this) = this.upgrade(cx) {
+                    this.update(cx, |this, cx| on_release(this, entity, cx));
+                }
+            }),
+        )
+    }
+
     pub fn notify(&mut self) {
         self.app.pending_effects.push_back(Effect::Notify {
             emitter: self.entity_id,

crates/gpui3/src/subscription.rs

@@ -59,6 +59,11 @@ where
         }
     }
 
+    pub fn remove(&self, emitter: &EmitterKey) -> impl IntoIterator<Item = Callback> {
+        let subscribers = self.0.lock().subscribers.remove(&emitter);
+        subscribers.unwrap_or_default().into_values()
+    }
+
     pub fn retain<F>(&self, emitter: &EmitterKey, mut f: F)
     where
         F: FnMut(&mut Callback) -> bool,

crates/gpui3/src/window.rs

@@ -961,6 +961,40 @@ impl<'a, 'w, S: Send + Sync + 'static> ViewContext<'a, 'w, S> {
         )
     }
 
+    pub fn on_release(
+        &mut self,
+        on_release: impl Fn(&mut S, &mut WindowContext) + Send + Sync + 'static,
+    ) -> Subscription {
+        let window_handle = self.window.handle;
+        self.app.release_handlers.insert(
+            self.entity_id,
+            Box::new(move |this, cx| {
+                let this = this.downcast_mut().expect("invalid entity type");
+                // todo!("are we okay with silently swallowing the error?")
+                let _ = cx.update_window(window_handle.id, |cx| on_release(this, cx));
+            }),
+        )
+    }
+
+    pub fn observe_release<E: Send + Sync + 'static>(
+        &mut self,
+        handle: &Handle<E>,
+        on_release: impl Fn(&mut S, &mut E, &mut ViewContext<'_, '_, S>) + Send + Sync + 'static,
+    ) -> Subscription {
+        let this = self.handle();
+        let window_handle = self.window.handle;
+        self.app.release_handlers.insert(
+            handle.id,
+            Box::new(move |entity, cx| {
+                let entity = entity.downcast_mut().expect("invalid entity type");
+                // todo!("are we okay with silently swallowing the error?")
+                let _ = cx.update_window(window_handle.id, |cx| {
+                    this.update(cx, |this, cx| on_release(this, entity, cx))
+                });
+            }),
+        )
+    }
+
     pub fn notify(&mut self) {
         self.window_cx.notify();
         self.window_cx