Add MTLResourceID::from_raw and MTLResourceID::as_raw

Fixes #660

crates/objc2/src/topics/about_generated/CHANGELOG.md

@@ -17,6 +17,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 * Added `Eq` implementation for `NSValue` and subclasses.
 * Added `CopyingHelper` and `MutableCopyingHelper`, which are used to specify
   the types returned from `NSCopying` and `NSMutableCopying`.
+* Added `MTLResourceID::from_raw` and `MTLResourceID::as_raw` to allow
+  querying the underlying data.
 
 ### Changed
 * Allow using `MainThreadBound` without the `NSThread` feature flag.

framework-crates/objc2-metal/src/lib.rs

@@ -61,6 +61,8 @@ mod resource;
 mod slice;
 #[cfg(feature = "MTLTexture")]
 mod texture;
+#[cfg(feature = "MTLTypes")]
+mod types;
 
 #[cfg(feature = "MTLCounters")]
 pub use self::counters::*;

framework-crates/objc2-metal/src/types.rs

@@ -0,0 +1,30 @@
+use crate::MTLResourceID;
+
+impl MTLResourceID {
+    /// Construct a `MTLResourceID` from an ID previously gotten via.
+    /// `to_raw`.
+    ///
+    /// # Safety
+    ///
+    /// The documentation for `MTLResourceID` says:
+    ///
+    /// > A MTLResourceID represents a specific GPU resource, mutating this
+    /// > handle is undefined unless the mutation results in the value
+    /// > equalling an already existing handle of the same resource type.
+    ///
+    /// So we've tentatively marked this method as `unsafe`, with the safety
+    /// requirement that the ID must be valid, i.e. have previously come from
+    /// [`to_raw`][Self::to_raw] or similar.
+    ///
+    /// If you disagree with this assessment, feel free to open an issue!
+    pub const unsafe fn from_raw(id: u64) -> Self {
+        Self { _impl: id }
+    }
+
+    /// Get the underlying data of the ID.
+    ///
+    /// May be useful for FFI purposes.
+    pub const fn to_raw(self) -> u64 {
+        self._impl
+    }
+}