gpui: Remove some unnecessay heap allocations in entity handling (#49579)

Release Notes:

- N/A *or* Added/Fixed/Improved ...

crates/gpui/src/app.rs

@@ -869,10 +869,12 @@ impl App {
         &mut self,
         callback: impl FnOnce(&mut App) -> R,
     ) -> (R, FxHashSet<EntityId>) {
-        let accessed_entities_start = self.entities.accessed_entities.borrow().clone();
+        let accessed_entities_start = self.entities.accessed_entities.get_mut().clone();
         let result = callback(self);
-        let accessed_entities_end = self.entities.accessed_entities.borrow().clone();
-        let entities_accessed_in_callback = accessed_entities_end
+        let entities_accessed_in_callback = self
+            .entities
+            .accessed_entities
+            .get_mut()
             .difference(&accessed_entities_start)
             .copied()
             .collect::<FxHashSet<EntityId>>();

crates/gpui/src/app/entity_map.rs

@@ -11,7 +11,6 @@ use std::{
     fmt::{self, Display},
     hash::{Hash, Hasher},
     marker::PhantomData,
-    mem,
     num::NonZeroU64,
     sync::{
         Arc, Weak,
@@ -95,7 +94,7 @@ impl EntityMap {
     where
         T: 'static,
     {
-        let mut accessed_entities = self.accessed_entities.borrow_mut();
+        let mut accessed_entities = self.accessed_entities.get_mut();
         accessed_entities.insert(slot.entity_id);
 
         let handle = slot.0;
@@ -107,7 +106,7 @@ impl EntityMap {
     #[track_caller]
     pub fn lease<T>(&mut self, pointer: &Entity<T>) -> Lease<T> {
         self.assert_valid_context(pointer);
-        let mut accessed_entities = self.accessed_entities.borrow_mut();
+        let mut accessed_entities = self.accessed_entities.get_mut();
         accessed_entities.insert(pointer.entity_id);
 
         let entity = Some(
@@ -147,21 +146,20 @@ impl EntityMap {
 
     pub fn extend_accessed(&mut self, entities: &FxHashSet<EntityId>) {
         self.accessed_entities
-            .borrow_mut()
+            .get_mut()
             .extend(entities.iter().copied());
     }
 
     pub fn clear_accessed(&mut self) {
-        self.accessed_entities.borrow_mut().clear();
+        self.accessed_entities.get_mut().clear();
     }
 
     pub fn take_dropped(&mut self) -> Vec<(EntityId, Box<dyn Any>)> {
-        let mut ref_counts = self.ref_counts.write();
-        let dropped_entity_ids = mem::take(&mut ref_counts.dropped_entity_ids);
-        let mut accessed_entities = self.accessed_entities.borrow_mut();
+        let mut ref_counts = &mut *self.ref_counts.write();
+        let dropped_entity_ids = ref_counts.dropped_entity_ids.drain(..);
+        let mut accessed_entities = self.accessed_entities.get_mut();
 
         dropped_entity_ids
-            .into_iter()
             .filter_map(|entity_id| {
                 let count = ref_counts.counts.remove(entity_id).unwrap();
                 debug_assert_eq!(

crates/gpui/src/window.rs

@@ -2236,9 +2236,8 @@ impl Window {
     }
 
     fn record_entities_accessed(&mut self, cx: &mut App) {
-        let mut entities_ref = cx.entities.accessed_entities.borrow_mut();
+        let mut entities_ref = cx.entities.accessed_entities.get_mut();
         let mut entities = mem::take(entities_ref.deref_mut());
-        drop(entities_ref);
         let handle = self.handle;
         cx.record_entities_accessed(
             handle,
@@ -2246,7 +2245,7 @@ impl Window {
             self.invalidator.clone(),
             &entities,
         );
-        let mut entities_ref = cx.entities.accessed_entities.borrow_mut();
+        let mut entities_ref = cx.entities.accessed_entities.get_mut();
         mem::swap(&mut entities, entities_ref.deref_mut());
     }