From 039790909b681237dd9e63494ce2c2cd29b220c3 Mon Sep 17 00:00:00 2001
From: Jerzy Wilczek <jerzy.wilczek@swmansion.com>
Date: Thu, 31 Oct 2024 13:35:28 +0100
Subject: [PATCH] Change the `DropCallback` API to use `FnOnce` instead of
 `FnMut`

---
 CHANGELOG.md        |  6 ++++++
 wgpu-hal/src/lib.rs | 12 ++++++++----
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f1d130b0ee..b3999f0cfa 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -46,6 +46,12 @@ Bottom level categories:
 
 - Parse `diagnostic(…)` directives, but don't implement any triggering rules yet. By @ErichDonGubler in [#6456](https://github.com/gfx-rs/wgpu/pull/6456).
 
+### Changes
+
+#### HAL
+
+- Change the `DropCallback` API to use `FnOnce` instead of `FnMut`. By @jerzywilczek in [#6482](https://github.com/gfx-rs/wgpu/pull/6482)
+
 ## 23.0.0 (2024-10-25)
 
 ### Themes of this release
diff --git a/wgpu-hal/src/lib.rs b/wgpu-hal/src/lib.rs
index 6578252c1a..0cddb69976 100644
--- a/wgpu-hal/src/lib.rs
+++ b/wgpu-hal/src/lib.rs
@@ -305,24 +305,28 @@ pub type AtomicFenceValue = std::sync::atomic::AtomicU64;
 
 /// A callback to signal that wgpu is no longer using a resource.
 #[cfg(any(gles, vulkan))]
-pub type DropCallback = Box<dyn FnMut() + Send + Sync + 'static>;
+pub type DropCallback = Box<dyn FnOnce() + Send + Sync + 'static>;
 
 #[cfg(any(gles, vulkan))]
 pub struct DropGuard {
-    callback: DropCallback,
+    callback: Option<DropCallback>,
 }
 
 #[cfg(all(any(gles, vulkan), any(native, Emscripten)))]
 impl DropGuard {
     fn from_option(callback: Option<DropCallback>) -> Option<Self> {
-        callback.map(|callback| Self { callback })
+        callback.map(|callback| Self {
+            callback: Some(callback),
+        })
     }
 }
 
 #[cfg(any(gles, vulkan))]
 impl Drop for DropGuard {
     fn drop(&mut self) {
-        (self.callback)();
+        if let Some(cb) = self.callback.take() {
+            (cb)();
+        }
     }
 }