From c2239f8d149776552155ae3506f322a3571b7990 Mon Sep 17 00:00:00 2001
From: IS2511 <is2511@bk.ru>
Date: Wed, 15 Feb 2023 21:38:56 +0300
Subject: [PATCH 1/4] Make `IdTypeMap::get_temp` use immutable `self`

---
 crates/egui/src/util/id_type_map.rs | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/crates/egui/src/util/id_type_map.rs b/crates/egui/src/util/id_type_map.rs
index c5fcae0d1a6..6f75ff25040 100644
--- a/crates/egui/src/util/id_type_map.rs
+++ b/crates/egui/src/util/id_type_map.rs
@@ -169,6 +169,14 @@ impl Element {
         }
     }
 
+    #[inline]
+    pub(crate) fn get_temp<T: 'static>(&self) -> Option<&T> {
+        match self {
+            Self::Value { value, .. } => value.downcast_ref(),
+            Self::Serialized { .. } => None,
+        }
+    }
+
     #[inline]
     pub(crate) fn get_mut_temp<T: 'static>(&mut self) -> Option<&mut T> {
         match self {
@@ -355,11 +363,11 @@ impl IdTypeMap {
     ///
     /// The call clones the value (if found), so make sure it is cheap to clone!
     #[inline]
-    pub fn get_temp<T: 'static + Clone>(&mut self, id: Id) -> Option<T> {
+    pub fn get_temp<T: 'static + Clone>(&self, id: Id) -> Option<T> {
         let hash = hash(TypeId::of::<T>(), id);
         self.0
-            .get_mut(&hash)
-            .and_then(|x| x.get_mut_temp())
+            .get(&hash)
+            .and_then(|x| x.get_temp())
             .cloned()
     }
 

From e76c7918ea677e009f1916fe49652c5594e58eed Mon Sep 17 00:00:00 2001
From: IS2511 <is2511@bk.ru>
Date: Wed, 15 Feb 2023 21:41:00 +0300
Subject: [PATCH 2/4] Add note to `IdTypeMap::get_persisted` about mutability

---
 crates/egui/src/util/id_type_map.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/crates/egui/src/util/id_type_map.rs b/crates/egui/src/util/id_type_map.rs
index 6f75ff25040..ce5e6d3cefc 100644
--- a/crates/egui/src/util/id_type_map.rs
+++ b/crates/egui/src/util/id_type_map.rs
@@ -373,6 +373,9 @@ impl IdTypeMap {
 
     /// Read a value, optionally deserializing it if available.
     ///
+    /// NOTE: A mutable `self` is needed because internally this deserializes on first call
+    /// and caches the result (caching requires self-mutability).
+    ///
     /// The call clones the value (if found), so make sure it is cheap to clone!
     #[inline]
     pub fn get_persisted<T: SerializableAny>(&mut self, id: Id) -> Option<T> {

From 215897b9d51249a87d65611702e7454e37440f6c Mon Sep 17 00:00:00 2001
From: IS2511 <is2511@bk.ru>
Date: Wed, 15 Feb 2023 21:45:46 +0300
Subject: [PATCH 3/4] Add mention of `ArcSwap` in `IdTypeMap` docs

---
 crates/egui/src/util/id_type_map.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/crates/egui/src/util/id_type_map.rs b/crates/egui/src/util/id_type_map.rs
index ce5e6d3cefc..d4aa938e09e 100644
--- a/crates/egui/src/util/id_type_map.rs
+++ b/crates/egui/src/util/id_type_map.rs
@@ -309,6 +309,7 @@ use crate::Id;
 ///
 /// Values are cloned when read, so keep them small and light.
 /// If you want to store something bigger, wrap them in `Arc<Mutex<…>>`.
+/// Also try `Arc<ArcSwap<…>>`.
 ///
 /// Values can either be "persisted" (serializable) or "temporary" (cleared when egui is shut down).
 ///

From 1844b64646c2a834b6dbdd2f528b534c33eff192 Mon Sep 17 00:00:00 2001
From: IS2511 <is2511@bk.ru>
Date: Sun, 5 Mar 2023 13:49:56 +0300
Subject: [PATCH 4/4] Fix formatting with `cargo fmt`

---
 crates/egui/src/util/id_type_map.rs | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/crates/egui/src/util/id_type_map.rs b/crates/egui/src/util/id_type_map.rs
index d4aa938e09e..77e70a2ba28 100644
--- a/crates/egui/src/util/id_type_map.rs
+++ b/crates/egui/src/util/id_type_map.rs
@@ -366,10 +366,7 @@ impl IdTypeMap {
     #[inline]
     pub fn get_temp<T: 'static + Clone>(&self, id: Id) -> Option<T> {
         let hash = hash(TypeId::of::<T>(), id);
-        self.0
-            .get(&hash)
-            .and_then(|x| x.get_temp())
-            .cloned()
+        self.0.get(&hash).and_then(|x| x.get_temp()).cloned()
     }
 
     /// Read a value, optionally deserializing it if available.