Support drop guard for session

openxr/src/instance.rs

@@ -368,7 +368,26 @@ impl Instance {
         info: &G::SessionCreateInfo,
     ) -> Result<(Session<G>, FrameWaiter, FrameStream<G>)> {
         let handle = G::create_session(self, system, info)?;
-        Ok(Session::from_raw(self.clone(), handle))
+        Ok(Session::from_raw(self.clone(), handle, Box::new(())))
+    }
+
+    /// Refer to [`Instance::create_session()`]. The extra `drop_guard` argument is dropped after
+    /// the session is destroyed and this can be used to ensure safety.
+    ///
+    /// # Safety
+    ///
+    /// The requirements documented by the graphics API extension must be respected. Among other
+    /// requirements, `info` must contain valid handles, and certain operations must be externally
+    /// synchronized.
+    #[inline]
+    pub unsafe fn create_session_with_guard<G: Graphics>(
+        &self,
+        system: SystemId,
+        info: &G::SessionCreateInfo,
+        drop_guard: DropGuard,
+    ) -> Result<(Session<G>, FrameWaiter, FrameStream<G>)> {
+        let handle = G::create_session(self, system, info)?;
+        Ok(Session::from_raw(self.clone(), handle, drop_guard))
     }
 
     /// Get the next event, if available

openxr/src/session.rs

@@ -3,6 +3,8 @@ use std::{marker::PhantomData, ptr, sync::Arc};
 
 use crate::*;
 
+pub(crate) type DropGuard = Box<dyn std::any::Any + Send + Sync>;
+
 /// A rendering session using a particular graphics API `G`
 ///
 /// Convertible into an API-agnostic session using [`Session::into_any_graphics`].
@@ -382,9 +384,14 @@ impl<G: Graphics> Session<G> {
     pub unsafe fn from_raw(
         instance: Instance,
         handle: sys::Session,
+        drop_guard: DropGuard,
     ) -> (Self, FrameWaiter, FrameStream<G>) {
         let session = Self {
-            inner: Arc::new(SessionInner { instance, handle }),
+            inner: Arc::new(SessionInner {
+                instance,
+                handle,
+                _drop_guard: drop_guard,
+            }),
             _marker: PhantomData,
         };
         (
@@ -448,6 +455,7 @@ impl<G> Clone for Session<G> {
 pub(crate) struct SessionInner {
     pub(crate) instance: Instance,
     pub(crate) handle: sys::Session,
+    pub(crate) _drop_guard: DropGuard,
 }
 
 impl Drop for SessionInner {