Make wgpu-core users responsible for choosing back ends.

.github/workflows/ci.yml

@@ -159,11 +159,18 @@ jobs:
  # check with no features
  cargo clippy --target ${{ matrix.target }} -p wgpu -p wgpu-core -p wgpu-info -p player --no-default-features
 
- # check with all features
- cargo clippy --target ${{ matrix.target }} -p wgpu -p wgpu-core -p wgpu-info -p player --tests --all-features
+ # Check with all features.
+ # (But watch out for backend-selection features in wgpu-core; some of
+ # those only build on the right platforms.)
+ cargo clippy --target ${{ matrix.target }} -p wgpu -p wgpu-info -p player --tests --all-features
+ cargo clippy --target ${{ matrix.target }} -p wgpu-core --tests \
+ --features="portable_features"
 
  # build docs
- cargo doc --target ${{ matrix.target }} -p wgpu -p wgpu-core -p wgpu-info -p player --all-features --no-deps
+ # (Watch out for backend-selection features in wgpu-core; some of
+ # those only build on the right platforms.)
+ cargo doc --target ${{ matrix.target }} -p wgpu -p wgpu-info -p player --all-features --no-deps
+ cargo doc --target ${{ matrix.target }} -p wgpu-core --no-deps --features="portable_features"
 
  gpu-test:
  strategy:

CHANGELOG.md

@@ -42,6 +42,42 @@ Bottom level categories:
 
 ### Major Changes
 
+#### Backend selection by features
+
+Whereas `wgpu-core` used to automatically select backends to enable
+based on the target OS and architecture, it now has separate features
+to enable each backend:
+
+- "metal", for the Metal API on macOS and iOS
+- "vulkan", for the Vulkan API (Linux, some Android, and occasionally Windows)
+- "dx12", for Microsoft's Direct3D 12 API
+- "gles", OpenGL ES, available on many systems
+- "dx11", for Microsoft's Direct3D 11 API
+
+None are enabled by default, but the `wgpu` crate automatically
+selects these features based on the target operating system and
+architecture, using the same rules that `wgpu-core` used to, so users
+of `wgpu` should be unaffected by this change. However, other crates
+using `wgpu-core` directly will need to copy `wgpu`'s logic or write
+their own. See the `[target]` section of `wgpu/Cargo.toml` for
+details.
+
+Similarly, `wgpu-core` now has `emscripten` and `renderdoc` features
+that `wgpu` enables on appropriate platforms.
+
+In previous releases, the `wgpu-core` crate decided which backends to
+support. However, this left `wgpu-core`'s users with no way to
+override those choices. (Firefox doesn't want the GLES back end, for
+example.) There doesn't seem to be any way to have a crate select
+backends based on target OS and architecture that users of that crate
+can still override. Default features can't be selected based on the
+target, for example. That implies that we should do the selection as
+late in the dependency DAG as feasible. Having `wgpu` (and
+`wgpu-core`'s other dependents) choose backends seems like the best
+option.
+
+By @jimblandy in [#3254](https://github.com/gfx-rs/wgpu/pull/3254).
+
 #### Surface Capabilities API
 
 The various surface capability functions were combined into a single call that gives you all the capabilities.

deno_webgpu/Cargo.toml

@@ -14,5 +14,23 @@ description = "WebGPU implementation for Deno"
 deno_core.workspace = true
 serde = { workspace = true, features = ["derive"] }
 tokio = { workspace = true, features = ["full"] }
-wgpu-core = { workspace = true, features = ["trace", "replay", "serde", "strict_asserts", "wgsl"] }
 wgpu-types = { workspace = true, features = ["trace", "replay", "serde"] }
+
+[dependencies.wgpu-core]
+workspace = true
+features = ["trace", "replay", "serde", "strict_asserts", "wgsl", "gles"]
+
+# We want the wgpu-core Metal backend on macOS and iOS.
+[target.'cfg(any(target_os = "macos", target_os = "ios"))'.dependencies.wgpu-core]
+workspace = true
+features = ["metal"]
+
+# We want the wgpu-core Direct3D backends on Windows.
+[target.'cfg(windows)'.dependencies.wgpu-core]
+workspace = true
+features = ["dx11", "dx12"]
+
+# We want the wgpu-core Vulkan backend on Unix (but not Emscripten) and Windows.
+[target.'cfg(any(windows, all(unix, not(target_arch = "emscripten"))))'.dependencies.wgpu-core]
+workspace = true
+features = ["vulkan"]

wgpu-core/Cargo.toml

@@ -17,6 +17,21 @@ rustdoc-args = ["--cfg", "docsrs"]
 
 [features]
 default = []
+
+# Backends, passed through to wgpu-hal
+metal = ["hal/metal"]
+vulkan = ["hal/vulkan"]
+gles = ["hal/gles"]
+dx11 = ["hal/dx11"]
+dx12 = ["hal/dx12"]
+
+# Support the Renderdoc graphics debugger:
+# https://renderdoc.org/
+renderdoc = ["hal/renderdoc"]
+
+# Compile for the Emscripten POSIX-in-a-web-page emulation environment.
+emscripten = ["hal/emscripten"]
+
 # Apply run-time checks, even in release builds. These are in addition
 # to the validation carried out at public APIs in all builds.
 strict_asserts = []
@@ -32,6 +47,9 @@ id32 = []
 wgsl = ["naga/wgsl-in"]
 vulkan-portability = ["hal/vulkan"]
 
+# Features that are intended to work on all platforms.
+portable_features = ["gles", "strict_asserts", "trace", "replay", "serial-pass", "id32", "wgsl"]
+
 [dependencies]
 arrayvec.workspace = true
 bitflags.workspace = true
@@ -59,22 +77,3 @@ workspace = true
 
 [target.'cfg(all(target_arch = "wasm32", not(target_os = "emscripten")))'.dependencies]
 web-sys = { workspace = true, features = ["HtmlCanvasElement", "OffscreenCanvas"] }
-
-[target.'cfg(target_arch = "wasm32")'.dependencies]
-hal = { workspace = true, features = ["gles"] }
-
-[target.'cfg(all(not(target_arch = "wasm32"), any(target_os = "ios", target_os = "macos")))'.dependencies]
-hal = { workspace = true, features = ["metal"] }
-#Note: could also enable "vulkan" for Vulkan Portability
-
-[target.'cfg(all(not(target_arch = "wasm32"), unix, not(target_os = "ios"), not(target_os = "macos")))'.dependencies]
-hal = { workspace = true, features = ["vulkan", "gles", "renderdoc"] }
-
-[target.'cfg(all(not(target_arch = "wasm32"), windows))'.dependencies]
-hal = { workspace = true, features = ["vulkan", "dx12", "dx11", "renderdoc"] }
-
-[target.'cfg(target_os = "emscripten")'.dependencies]
-hal = { workspace = true, features = ["emscripten"] }
-
-[build-dependencies]
-cfg_aliases.workspace = true

wgpu-core/src/device/mod.rs

@@ -5407,27 +5407,27 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
  let mut closures = UserClosures::default();
  let mut all_queue_empty = true;
 
- #[cfg(vulkan)]
+ #[cfg(feature = "vulkan")]
  {
  all_queue_empty = self.poll_devices::<hal::api::Vulkan>(force_wait, &mut closures)?
  && all_queue_empty;
  }
- #[cfg(metal)]
+ #[cfg(feature = "metal")]
  {
  all_queue_empty =
  self.poll_devices::<hal::api::Metal>(force_wait, &mut closures)? && all_queue_empty;
  }
- #[cfg(dx12)]
+ #[cfg(feature = "dx12")]
  {
  all_queue_empty =
  self.poll_devices::<hal::api::Dx12>(force_wait, &mut closures)? && all_queue_empty;
  }
- #[cfg(dx11)]
+ #[cfg(feature = "dx11")]
  {
  all_queue_empty =
  self.poll_devices::<hal::api::Dx11>(force_wait, &mut closures)? && all_queue_empty;
  }
- #[cfg(gl)]
+ #[cfg(feature = "gles")]
  {
  all_queue_empty =
  self.poll_devices::<hal::api::Gles>(force_wait, &mut closures)? && all_queue_empty;