🤘 metal: Migrate to objc2 architecture with objc2-metal bindings (#225)

* metal: Migrate to `objc2` architecture with `objc2-metal` bindings

The current `objc` crate stack is completely unmaintained and has
severely fallen out of date with no updates for over 4 years.  The
`metal-rs` crate, built on top of this architecture, is completely
written by hand which is tedious to keep up-to-date, not to mention
has inconsistencies in its implementation.

All of this is superseded by the new `objc2` crate stack built by
@madsmtm.  Beyond providing what seems like a better, safer abstraction
over Objective-C, _all_ bindings are completely autogenerated meaning
we'll no longer lag behind upstream bindings (requiring painstaking
manual patching) or have inconsistencies in the implementations, as long
as the generator is properly able to represent the bindings.

* Use `target_vendor = "apple"` instead of many custom `target_os`es

* Work around unused_qualifications lint for Rust 1.80 prelude extension

`size_of(_val)()` was added to the prelude in Rust 1.80, causing
`unused_qualifications` warnings whenever we qualify a call to it with
via `std::mem::size_of_val()`.

The easiest workaround is to remove the prefix and explicitly import the
function in scope.  We annotate the import with a `TODO` to remove it
once bumping our MSRV on or past 1.80.

Author: MarijnS95

.github/workflows/ci.yml

@@ -69,15 +69,6 @@ jobs:
         uses: dtolnay/rust-toolchain@nightly
       - name: Generate lockfile with minimal dependency versions
         run: cargo +nightly generate-lockfile -Zminimal-versions
-      - name: Bump `libc 0.1` version to `0.2` via `malloc_buf 0.0.6`
-        if: ${{ runner.os == 'macOS' }}
-        run: |
-          # The 7-year-unmaintained malloc_buf (depended on via metal-rs->objc)
-          # only allows using libc 0.2 since the 0.0.6 release, which is necessary
-          # since the libc 0.1 range no longer compiles.  Fortunately objc which
-          # is also unmaintained for 4 years depends on malloc_buf >=0.0,<0.1.0,
-          # allowing the 0.0.6 release to be used (but not the 1.0.0 release).
-          cargo update -p malloc_buf --precise 0.0.6
       - name: Cargo clippy with minimal-versions
         run: cargo +stable clippy --workspace --features ${{ matrix.features }} --no-default-features -- -D warnings
 

Cargo.toml

@@ -33,8 +33,18 @@ ash = { version = "0.38", optional = true, default-features = false, features =
 egui = { version = ">=0.24, <=0.27", optional = true, default-features = false }
 egui_extras = { version = ">=0.24, <=0.27", optional = true, default-features = false }
 
-[target.'cfg(any(target_os = "macos", target_os = "ios"))'.dependencies]
-metal = { version = "0.29.0", default-features = false, features = ["link", "dispatch"], optional = true }
+[target.'cfg(target_vendor = "apple")'.dependencies]
+objc2 = { version = "0.5.2", default-features = false, optional = true }
+objc2-foundation = { version = "0.2", default-features = false, optional = true }
+objc2-metal = { version = "0.2.1", default-features = false, features = [
+    "MTLAccelerationStructure",
+    "MTLBuffer",
+    "MTLDevice",
+    "MTLHeap",
+    "MTLResource",
+    "MTLTexture",
+    "std",
+], optional = true }
 
 [target.'cfg(windows)'.dependencies]
 # Only needed for public-winapi interop helpers
@@ -65,6 +75,11 @@ features = [
     "Win32_Graphics_Dxgi_Common",
 ]
 
+[target.'cfg(target_vendor = "apple")'.dev-dependencies]
+objc2-metal = { version = "0.2.1", default-features = false, features = [
+    "MTLPixelFormat",
+] }
+
 [[example]]
 name = "vulkan-buffer"
 required-features = ["vulkan", "ash/loaded"]
@@ -85,8 +100,8 @@ required-features = ["metal"]
 visualizer = ["dep:egui", "dep:egui_extras"]
 vulkan = ["dep:ash"]
 d3d12 = ["dep:windows"]
-metal = ["dep:metal"]
+metal = ["dep:objc2", "dep:objc2-metal", "dep:objc2-foundation"]
 # Expose helper functionality for winapi types to interface with gpu-allocator, which is primarily windows-rs driven
 public-winapi = ["dep:winapi"]
 
-default = ["d3d12", "vulkan"]
+default = ["d3d12", "vulkan", "metal"]

README.md

@@ -134,7 +134,7 @@ allocator.free(allocation).unwrap();
 
 ```rust
 use gpu_allocator::metal::*;
-
+use objc2_metal as metal;
 let mut allocator = Allocator::new(&AllocatorCreateDesc {
     device: device.clone(),
     debug_settings: Default::default(),
@@ -146,12 +146,12 @@ let mut allocator = Allocator::new(&AllocatorCreateDesc {
 ```rust
 use gpu_allocator::metal::*;
 use gpu_allocator::MemoryLocation;
-
+use objc2_metal as metal;
 let allocation_desc = AllocationCreateDesc::buffer(
     &device,
     "Example allocation",
     512, // size in bytes
-    gpu_allocator::MemoryLocation::GpuOnly,
+    MemoryLocation::GpuOnly,
 );
 let allocation = allocator.allocate(&allocation_desc).unwrap();
 let resource = allocation.make_buffer().unwrap();

examples/metal-buffer.rs

@@ -1,12 +1,20 @@
-use std::sync::Arc;
-
 use gpu_allocator::metal::{AllocationCreateDesc, Allocator, AllocatorCreateDesc};
 use log::info;
+use metal::MTLDevice as _;
+use objc2::rc::Id;
+use objc2_foundation::NSArray;
+use objc2_metal as metal;
 
 fn main() {
     env_logger::Builder::from_env(env_logger::Env::default().default_filter_or("trace")).init();
 
-    let device = Arc::new(metal::Device::system_default().unwrap());
+    // Allow the innards of objc2-metal to link the static function below:
+    // https://docs.rs/objc2-metal/0.2.2/objc2_metal/index.html
+    #[link(name = "CoreGraphics", kind = "framework")]
+    extern "C" {}
+
+    let device =
+        unsafe { Id::from_raw(metal::MTLCreateSystemDefaultDevice()) }.expect("No MTLDevice found");
 
     // Setting up the allocator
     let mut allocator = Allocator::new(&AllocatorCreateDesc {
@@ -60,11 +68,11 @@ fn main() {
 
     // Test allocating texture
     {
-        let texture_desc = metal::TextureDescriptor::new();
-        texture_desc.set_pixel_format(metal::MTLPixelFormat::RGBA8Unorm);
-        texture_desc.set_width(64);
-        texture_desc.set_height(64);
-        texture_desc.set_storage_mode(metal::MTLStorageMode::Private);
+        let texture_desc = unsafe { metal::MTLTextureDescriptor::new() };
+        texture_desc.setPixelFormat(metal::MTLPixelFormat::RGBA8Unorm);
+        unsafe { texture_desc.setWidth(64) };
+        unsafe { texture_desc.setHeight(64) };
+        texture_desc.setStorageMode(metal::MTLStorageMode::Private);
         let allocation_desc =
             AllocationCreateDesc::texture(&device, "Test allocation (Texture)", &texture_desc);
         let allocation = allocator.allocate(&allocation_desc).unwrap();
@@ -75,14 +83,14 @@ fn main() {
 
     // Test allocating acceleration structure
     {
-        let empty_array = metal::Array::from_slice(&[]);
-        let acc_desc = metal::PrimitiveAccelerationStructureDescriptor::descriptor();
-        acc_desc.set_geometry_descriptors(empty_array);
-        let sizes = device.acceleration_structure_sizes_with_descriptor(&acc_desc);
+        let empty_array = NSArray::from_slice(&[]);
+        let acc_desc = metal::MTLPrimitiveAccelerationStructureDescriptor::descriptor();
+        acc_desc.setGeometryDescriptors(Some(&empty_array));
+        let sizes = device.accelerationStructureSizesWithDescriptor(&acc_desc);
         let allocation_desc = AllocationCreateDesc::acceleration_structure_with_size(
             &device,
             "Test allocation (Acceleration structure)",
-            sizes.acceleration_structure_size,
+            sizes.accelerationStructureSize as u64,
             gpu_allocator::MemoryLocation::GpuOnly,
         );
         let allocation = allocator.allocate(&allocation_desc).unwrap();

src/d3d12/mod.rs

@@ -1,4 +1,10 @@
-use std::{backtrace::Backtrace, fmt, sync::Arc};
+use std::{
+    backtrace::Backtrace,
+    fmt,
+    // TODO: Remove when bumping MSRV to 1.80
+    mem::size_of_val,
+    sync::Arc,
+};
 
 use log::{debug, warn, Level};
 use windows::Win32::{
@@ -628,7 +634,7 @@ impl Allocator {
             device.CheckFeatureSupport(
                 D3D12_FEATURE_D3D12_OPTIONS,
                 <*mut D3D12_FEATURE_DATA_D3D12_OPTIONS>::cast(&mut options),
-                std::mem::size_of_val(&options) as u32,
+                size_of_val(&options) as u32,
             )
         }
         .map_err(|e| {

src/lib.rs

@@ -161,10 +161,11 @@
 //! ```no_run
 //! # #[cfg(feature = "metal")]
 //! # fn main() {
-//! # use std::sync::Arc;
 //! use gpu_allocator::metal::*;
-//!
-//! # let device = Arc::new(metal::Device::system_default().unwrap());
+//! # use objc2::rc::Id;
+//! use objc2_metal as metal;
+//! # let device = unsafe { metal::MTLCreateSystemDefaultDevice() };
+//! # let device = unsafe { Id::from_raw(device) }.expect("No MTLDevice found");
 //! let mut allocator = Allocator::new(&AllocatorCreateDesc {
 //!     device: device.clone(),
 //!     debug_settings: Default::default(),
@@ -179,22 +180,23 @@
 //! ```no_run
 //! # #[cfg(feature = "metal")]
 //! # fn main() {
-//! # use std::sync::Arc;
 //! use gpu_allocator::metal::*;
 //! use gpu_allocator::MemoryLocation;
-//! # let device = Arc::new(metal::Device::system_default().unwrap());
+//! # use objc2::rc::Id;
+//! use objc2_metal as metal;
+//! # let device = unsafe { metal::MTLCreateSystemDefaultDevice() };
+//! # let device = unsafe { Id::from_raw(device) }.expect("No MTLDevice found");
 //! # let mut allocator = Allocator::new(&AllocatorCreateDesc {
 //! #     device: device.clone(),
 //! #     debug_settings: Default::default(),
 //! #     allocation_sizes: Default::default(),
 //! # })
 //! # .unwrap();
-//!
 //! let allocation_desc = AllocationCreateDesc::buffer(
 //!     &device,
 //!     "Example allocation",
 //!     512, // size in bytes
-//!     gpu_allocator::MemoryLocation::GpuOnly,
+//!     MemoryLocation::GpuOnly,
 //! );
 //! let allocation = allocator.allocate(&allocation_desc).unwrap();
 //! let resource = allocation.make_buffer().unwrap();
@@ -206,6 +208,7 @@
 //! # #[cfg(not(feature = "metal"))]
 //! # fn main() {}
 //! ```
+#![deny(clippy::unimplemented, clippy::unwrap_used, clippy::ok_expect)]
 
 mod result;
 pub use result::*;
@@ -223,7 +226,7 @@ pub mod vulkan;
 #[cfg(all(windows, feature = "d3d12"))]
 pub mod d3d12;
 
-#[cfg(all(any(target_os = "macos", target_os = "ios"), feature = "metal"))]
+#[cfg(all(target_vendor = "apple", feature = "metal"))]
 pub mod metal;
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]