cgl: relax encoding requirements for CGLContextObj

The issue is that CGLContextObj changed its encoding in macOS Sonoma
14.0. The encoding of a type is something that objc2 uses to
debug-assert that the definition is written correctly, but of course, if
the Rust code assumes that the encoding is one thing, and it then
changes, then the debug assertion will now fail.

Fixes #1640.

CHANGELOG.md

@@ -1,5 +1,7 @@
 # Unreleased
 
+- Fixed `CGLContextObj` having an invalid encoding on newer macOS versions.
+
 # Version 0.31.0
 
 - Bump MSRV from `1.60` to `1.65`.

glutin/Cargo.toml

@@ -52,7 +52,8 @@ x11-dl = { version = "2.20.0", optional = true }
 [target.'cfg(any(target_os = "macos"))'.dependencies]
 cgl = "0.3.2"
 core-foundation = "0.9.3"
-objc2 = "0.4.1"
+# Enable `relax-void-encoding` until https://github.com/madsmtm/objc2/pull/526 is resolved
+objc2 = { version = "0.4.1", features = ["relax-void-encoding"] }
 dispatch = "0.2.0"
 
 [target.'cfg(any(target_os = "macos"))'.dependencies.icrate]

glutin/src/api/cgl/appkit.rs

@@ -17,7 +17,7 @@ pub struct CGLContextObj {
 }
 
 unsafe impl RefEncode for CGLContextObj {
-    const ENCODING_REF: Encoding = Encoding::Pointer(&Encoding::Struct("_CGLContextObject", &[]));
+    const ENCODING_REF: Encoding = Encoding::Pointer(&Encoding::Void);
 }
 
 extern_class!(