Add most of a CPAL standalone backend

For ALSA, CoreAudio, and WASAPI.

Cargo.lock

@@ -62,6 +62,28 @@ version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "250f629c0161ad8107cf89319e990051fae62832fd343083bea452d93e2205fd"
 
+[[package]]
+name = "alsa"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5915f52fe2cf65e83924d037b6c5290b7cee097c6b5c8700746e6168a343fd6b"
+dependencies = [
+ "alsa-sys",
+ "bitflags",
+ "libc",
+ "nix 0.23.1",
+]
+
+[[package]]
+name = "alsa-sys"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "db8fee663d06c4e303404ef5f40488a53e062f89ba8bfed81f42325aafad1527"
+dependencies = [
+ "libc",
+ "pkg-config",
+]
+
 [[package]]
 name = "android_glue"
 version = "0.2.3"
@@ -330,7 +352,7 @@ dependencies = [
  "cocoa",
  "core-foundation 0.9.3",
  "keyboard-types",
- "nix",
+ "nix 0.22.3",
  "objc",
  "raw-window-handle",
  "uuid",
@@ -348,7 +370,7 @@ dependencies = [
  "cocoa",
  "core-foundation 0.9.3",
  "keyboard-types",
- "nix",
+ "nix 0.22.3",
  "objc",
  "raw-window-handle",
  "uuid",
@@ -358,6 +380,25 @@ dependencies = [
  "xcb-util",
 ]
 
+[[package]]
+name = "bindgen"
+version = "0.59.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2bd2a9a458e8f4304c52c43ebb0cfbd520289f8379a52e329a38afda99bf8eb8"
+dependencies = [
+ "bitflags",
+ "cexpr",
+ "clang-sys",
+ "lazy_static",
+ "lazycell",
+ "peeking_take_while",
+ "proc-macro2",
+ "quote",
+ "regex",
+ "rustc-hash",
+ "shlex",
+]
+
 [[package]]
 name = "bit-set"
 version = "0.5.2"
@@ -431,6 +472,12 @@ version = "1.4.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "14c189c53d098945499cdfa7ecc63567cf3886b3332b312a5b4585d8d3a6a610"
 
+[[package]]
+name = "bytes"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec8a7b6a70fde80372154c65702f00a0f56f3e1c36abbc6c440484be248856db"
+
 [[package]]
 name = "cache-padded"
 version = "1.2.0"
@@ -453,6 +500,21 @@ dependencies = [
  "jobserver",
 ]
 
+[[package]]
+name = "cesu8"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6d43a04d8753f35258c91f8ec639f792891f748a1edbd759cf1dcea3382ad83c"
+
+[[package]]
+name = "cexpr"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6fac387a98bb7c37292057cffc56d62ecb629900026402633ae9160df93a8766"
+dependencies = [
+ "nom",
+]
+
 [[package]]
 name = "cfg-if"
 version = "0.1.10"
@@ -486,6 +548,17 @@ version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "17cc5e6b5ab06331c33589842070416baa137e8b0eb912b008cfd4a78ada7919"
 
+[[package]]
+name = "clang-sys"
+version = "1.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a050e2153c5be08febd6734e29298e844fdb0fa21aeddd63b4eb7baa106c69b"
+dependencies = [
+ "glob",
+ "libc",
+ "libloading",
+]
+
 [[package]]
 name = "clap"
 version = "3.2.5"
@@ -597,6 +670,16 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3d7b894f5411737b7867f4827955924d7c254fc9f4d91a6aad6b097804b1018b"
 
+[[package]]
+name = "combine"
+version = "4.6.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "35ed6e9d84f0b51a7f52daf1c7d71dd136fd7a3f41a8462b8cdb8c78d920fad4"
+dependencies = [
+ "bytes",
+ "memchr",
+]
+
 [[package]]
 name = "concurrent-queue"
 version = "1.2.2"
@@ -730,6 +813,50 @@ dependencies = [
  "objc",
 ]
 
+[[package]]
+name = "coreaudio-rs"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "11894b20ebfe1ff903cbdc52259693389eea03b94918a2def2c30c3bf227ad88"
+dependencies = [
+ "bitflags",
+ "coreaudio-sys",
+]
+
+[[package]]
+name = "coreaudio-sys"
+version = "0.2.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3dff444d80630d7073077d38d40b4501fd518bd2b922c2a55edcc8b0f7be57e6"
+dependencies = [
+ "bindgen",
+]
+
+[[package]]
+name = "cpal"
+version = "0.13.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "74117836a5124f3629e4b474eed03e479abaf98988b4bb317e29f08cfe0e4116"
+dependencies = [
+ "alsa",
+ "core-foundation-sys 0.8.3",
+ "coreaudio-rs",
+ "jni",
+ "js-sys",
+ "lazy_static",
+ "libc",
+ "mach",
+ "ndk 0.6.0",
+ "ndk-glue 0.6.2",
+ "nix 0.23.1",
+ "oboe",
+ "parking_lot 0.11.2",
+ "stdweb",
+ "thiserror",
+ "web-sys",
+ "winapi",
+]
+
 [[package]]
 name = "crc32fast"
 version = "1.3.2"
@@ -1504,6 +1631,12 @@ dependencies = [
  "version_check",
 ]
 
+[[package]]
+name = "glob"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9b919933a397b79c37e33b77bb2aa3dc8eb6e165ad809e58ff75bc7db2e34574"
+
 [[package]]
 name = "gloo-timers"
 version = "0.2.4"
@@ -1989,6 +2122,20 @@ dependencies = [
  "pkg-config",
 ]
 
+[[package]]
+name = "jni"
+version = "0.19.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c6df18c2e3db7e453d3c6ac5b3e9d5182664d28788126d39b91f2d1e22b017ec"
+dependencies = [
+ "cesu8",
+ "combine",
+ "jni-sys",
+ "log",
+ "thiserror",
+ "walkdir",
+]
+
 [[package]]
 name = "jni-sys"
 version = "0.3.0"
@@ -2086,6 +2233,12 @@ version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
+[[package]]
+name = "lazycell"
+version = "1.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "830d08ce1d1d941e6b30645f1a0eb5643013d835ce3779a5fc208261dbe10f55"
+
 [[package]]
 name = "libc"
 version = "0.2.126"
@@ -2191,6 +2344,15 @@ dependencies = [
  "lyon_path",
 ]
 
+[[package]]
+name = "mach"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b823e83b2affd8f40a9ee8c29dbc56404c1e34cd2710921f2801e2cf29527afa"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "malloc_buf"
 version = "0.0.6"
@@ -2334,7 +2496,20 @@ checksum = "96d868f654c72e75f8687572699cdabe755f03effbb62542768e995d5b8d699d"
 dependencies = [
  "bitflags",
  "jni-sys",
- "ndk-sys",
+ "ndk-sys 0.2.2",
+ "num_enum",
+ "thiserror",
+]
+
+[[package]]
+name = "ndk"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2032c77e030ddee34a6787a64166008da93f6a352b629261d0fee232b8742dd4"
+dependencies = [
+ "bitflags",
+ "jni-sys",
+ "ndk-sys 0.3.0",
  "num_enum",
  "thiserror",
 ]
@@ -2354,10 +2529,25 @@ dependencies = [
  "lazy_static",
  "libc",
  "log",
- "ndk",
+ "ndk 0.5.0",
  "ndk-context",
  "ndk-macro",
- "ndk-sys",
+ "ndk-sys 0.2.2",
+]
+
+[[package]]
+name = "ndk-glue"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0d0c4a7b83860226e6b4183edac21851f05d5a51756e97a1144b7f5a6b63e65f"
+dependencies = [
+ "lazy_static",
+ "libc",
+ "log",
+ "ndk 0.6.0",
+ "ndk-context",
+ "ndk-macro",
+ "ndk-sys 0.3.0",
 ]
 
 [[package]]
@@ -2379,6 +2569,15 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e1bcdd74c20ad5d95aacd60ef9ba40fdf77f767051040541df557b7a9b2a2121"
 
+[[package]]
+name = "ndk-sys"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6e5a6ae77c8ee183dcbbba6150e2e6b9f3f4196a7666c02a715a95692ec1fa97"
+dependencies = [
+ "jni-sys",
+]
+
 [[package]]
 name = "nih_plug"
 version = "0.0.0"
@@ -2393,6 +2592,7 @@ dependencies = [
  "cfg-if 1.0.0",
  "clap",
  "clap-sys",
+ "cpal",
  "crossbeam",
  "jack",
  "lazy_static",
@@ -2488,6 +2688,19 @@ dependencies = [
  "memoffset",
 ]
 
+[[package]]
+name = "nix"
+version = "0.23.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9f866317acbd3a240710c63f065ffb1e4fd466259045ccb504130b7f668f35c6"
+dependencies = [
+ "bitflags",
+ "cc",
+ "cfg-if 1.0.0",
+ "libc",
+ "memoffset",
+]
+
 [[package]]
 name = "nohash-hasher"
 version = "0.2.0"
@@ -2513,6 +2726,17 @@ dependencies = [
  "num-traits",
 ]
 
+[[package]]
+name = "num-derive"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "876a53fff98e03a936a674b29568b0e605f06b29372c2489ff4de23f1949743d"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "num-integer"
 version = "0.1.45"
@@ -2653,6 +2877,29 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "oboe"
+version = "0.4.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "27f63c358b4fa0fbcfefd7c8be5cfc39c08ce2389f5325687e7762a48d30a5c1"
+dependencies = [
+ "jni",
+ "ndk 0.6.0",
+ "ndk-context",
+ "num-derive",
+ "num-traits",
+ "oboe-sys",
+]
+
+[[package]]
+name = "oboe-sys"
+version = "0.4.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3370abb7372ed744232c12954d920d1a40f1c4686de9e79e800021ef492294bd"
+dependencies = [
+ "cc",
+]
+
 [[package]]
 name = "once_cell"
 version = "1.12.0"
@@ -2813,6 +3060,12 @@ dependencies = [
  "rustc_version",
 ]
 
+[[package]]
+name = "peeking_take_while"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "19b17cddbe7ec3f8bc800887bab5e717348c95ea2ca0b1bf0837fb964dc67099"
+
 [[package]]
 name = "percent-encoding"
 version = "2.1.0"
@@ -3236,6 +3489,21 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "regex"
+version = "1.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4c4eb3267174b8c6c2f654116623910a0fef09c4753f8dd83db29c48a0df988b"
+dependencies = [
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-syntax"
+version = "0.6.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a3f87b73ce11b1619a3c6332f45341e0047173771e8b8b73f87bfeefb7b56244"
+
 [[package]]
 name = "renderdoc-sys"
 version = "0.7.1"
@@ -3492,6 +3760,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "shlex"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "43b2853a4d09f215c24cc5489c992ce46052d359b5109343cbafbf26bc62f8a3"
+
 [[package]]
 name = "sid"
 version = "0.6.1"
@@ -3585,7 +3859,7 @@ dependencies = [
  "lazy_static",
  "log",
  "memmap2",
- "nix",
+ "nix 0.22.3",
  "pkg-config",
  "wayland-client",
  "wayland-cursor",
@@ -3661,6 +3935,12 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a2eb9349b6444b326872e140eb1cf5e7c522154d69e7a0ffb0fb81c06b37543f"
 
+[[package]]
+name = "stdweb"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ef5430c8e36b713e13b48a9f709cc21e046723fe44ce34587b73a830203b533e"
+
 [[package]]
 name = "stft"
 version = "0.1.0"
@@ -4235,7 +4515,7 @@ dependencies = [
  "bitflags",
  "downcast-rs",
  "libc",
- "nix",
+ "nix 0.22.3",
  "scoped-tls",
  "wayland-commons",
  "wayland-scanner",
@@ -4248,7 +4528,7 @@ version = "0.29.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "94f6e5e340d7c13490eca867898c4cec5af56c27a5ffe5c80c6fc4708e22d33e"
 dependencies = [
- "nix",
+ "nix 0.22.3",
  "once_cell",
  "smallvec",
  "wayland-sys",
@@ -4260,7 +4540,7 @@ version = "0.29.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c52758f13d5e7861fc83d942d3d99bf270c83269575e52ac29e5b73cb956a6bd"
 dependencies = [
- "nix",
+ "nix 0.22.3",
  "wayland-client",
  "xcursor",
 ]
@@ -4576,9 +4856,9 @@ dependencies = [
  "libc",
  "log",
  "mio",
- "ndk",
+ "ndk 0.5.0",
- "ndk-glue",
+ "ndk-glue 0.5.2",
- "ndk-sys",
+ "ndk-sys 0.2.2",
  "objc",
  "parking_lot 0.11.2",
  "percent-encoding",

Cargo.toml

@@ -49,7 +49,7 @@ assert_process_allocs = ["dep:assert_no_alloc"]
 # Enables an export target for standalone binaries through the
 # `nih_export_standalone()` function. Disabled by default as this requires
 # building additional dependencies for audio and MIDI handling.
-standalone = ["dep:baseview", "dep:clap", "dep:jack"]
+standalone = ["dep:baseview", "dep:clap", "dep:cpal", "dep:jack"]
 # Enables the `nih_export_vst3!()` macro. Enabled by default. This feature
 # exists mostly for GPL-compliance reasons, since even if you don't use the VST3
 # wrapper you might otherwise still include a couple (unused) symbols from the
@@ -97,6 +97,7 @@ assert_no_alloc = { version = "1.1", optional = true }
 baseview = { git = "https://github.com/robbert-vdh/baseview.git", branch = "feature/resize", features = ["opengl"], optional = true }
 # All the claps!
 clap = { version = "3.2", features = ["derive"], optional = true }
+cpal = { version = "0.13.5", optional = true }
 # The current upstream jack panics when it can't load the JACK library, which breaks the backend fallback
 jack = { git = "https://github.com/robbert-vdh/rust-jack.git", branch = "feature/handle-library-failure", optional = true }
 

src/wrapper/standalone.rs

@@ -70,16 +70,66 @@ pub fn nih_export_standalone_with_args<P: Plugin, Args: IntoIterator<Item = Stri
     .unwrap_or_else(|err| err.exit());
 
     match config.backend {
-        config::BackendType::Auto => match backend::Jack::new::<P>(config.clone()) {
+        config::BackendType::Auto => {
-            Ok(backend) => {
+            let result = backend::Jack::new::<P>(config.clone()).map(|backend| {
                 nih_log!("Using the JACK backend");
-                run_wrapper::<P, _>(backend, config)
+                run_wrapper::<P, _>(backend, config.clone())
+            });
+
+            #[cfg(target_os = "linux")]
+            let result = result.or_else(|_| {
+                match backend::Cpal::new::<P>(config.clone(), cpal::HostId::Alsa) {
+                    Ok(backend) => {
+                        nih_log!("Using the ALSA backend");
+                        Ok(run_wrapper::<P, _>(backend, config.clone()))
                     }
-            Err(_) => {
+                    Err(err) => {
-                nih_log!("Could not initialize JACK, falling back to the dummy audio backend");
+                        nih_error!(
+                            "Could not initialize either the JACK or the ALSA backends, falling \
+                             back to the dummy audio backend"
+                        );
+                        Err(err)
+                    }
+                }
+            });
+            #[cfg(target_os = "macos")]
+            let result = result.or_else(|_| {
+                match backend::Cpal::new::<P>(config.clone(), cpal::HostId::CoreAudio) {
+                    Ok(backend) => {
+                        nih_log!("Using the CoreAudio backend");
+                        Ok(run_wrapper::<P, _>(backend, config.clone()))
+                    }
+                    Err(err) => {
+                        nih_error!(
+                            "Could not initialize either the JACK or the CoreAudio backends, \
+                             falling back to the dummy audio backend"
+                        );
+                        Err(err)
+                    }
+                }
+            });
+            #[cfg(target_os = "windows")]
+            let result = result.or_else(|_| {
+                match backend::Cpal::new::<P>(config.clone(), cpal::HostId::Wasapi) {
+                    Ok(backend) => {
+                        nih_log!("Using the WASAPI backend");
+                        Ok(run_wrapper::<P, _>(backend, config.clone()))
+                    }
+                    Err(err) => {
+                        nih_error!(
+                            "Could not initialize either the JACK or the WASAPI backends, falling \
+                             back to the dummy audio backend"
+                        );
+                        Err(err)
+                    }
+                }
+            });
+
+            result.unwrap_or_else(|_| {
+                nih_error!("Falling back to the dummy audio backend, audio and MIDI will not work");
                 run_wrapper::<P, _>(backend::Dummy::new::<P>(config.clone()), config)
+            })
         }
-        },
         config::BackendType::Jack => match backend::Jack::new::<P>(config.clone()) {
             Ok(backend) => run_wrapper::<P, _>(backend, config),
             Err(err) => {
@@ -87,6 +137,36 @@ pub fn nih_export_standalone_with_args<P: Plugin, Args: IntoIterator<Item = Stri
                 false
             }
         },
+        #[cfg(target_os = "linux")]
+        config::BackendType::Alsa => {
+            match backend::Cpal::new::<P>(config.clone(), cpal::HostId::Alsa) {
+                Ok(backend) => run_wrapper::<P, _>(backend, config),
+                Err(err) => {
+                    nih_error!("Could not initialize the ALSA backend: {:#}", err);
+                    false
+                }
+            }
+        }
+        #[cfg(target_os = "macos")]
+        config::BackendType::CoreAudio => {
+            match backend::Cpal::new::<P>(config.clone(), cpal::HostId::CoreAudio) {
+                Ok(backend) => run_wrapper::<P, _>(backend, config),
+                Err(err) => {
+                    nih_error!("Could not initialize the CoreAudio backend: {:#}", err);
+                    false
+                }
+            }
+        }
+        #[cfg(target_os = "windows")]
+        config::BackendType::Wasapi => {
+            match backend::Cpal::new::<P>(config.clone(), cpal::HostId::Wasapi) {
+                Ok(backend) => run_wrapper::<P, _>(backend, config),
+                Err(err) => {
+                    nih_error!("Could not initialize the WASAPI backend: {:#}", err);
+                    false
+                }
+            }
+        }
         config::BackendType::Dummy => {
             run_wrapper::<P, _>(backend::Dummy::new::<P>(config.clone()), config)
         }

src/wrapper/standalone/backend.rs

@@ -1,12 +1,15 @@
-pub use self::dummy::Dummy;
-pub use self::jack::Jack;
-pub use crate::buffer::Buffer;
 use crate::context::Transport;
 use crate::midi::NoteEvent;
 
+mod cpal;
 mod dummy;
 mod jack;
 
+pub use self::cpal::Cpal;
+pub use self::dummy::Dummy;
+pub use self::jack::Jack;
+pub use crate::buffer::Buffer;
+
 /// An audio+MIDI backend for the standalone wrapper.
 pub trait Backend: 'static + Send + Sync {
     /// Start processing audio and MIDI on this thread. The process callback will be called whenever

src/wrapper/standalone/backend/cpal.rs

@@ -0,0 +1,82 @@
+use anyhow::{Context, Result};
+use cpal::traits::*;
+
+use super::super::config::WrapperConfig;
+use super::Backend;
+use crate::buffer::Buffer;
+use crate::context::Transport;
+use crate::midi::NoteEvent;
+use crate::plugin::Plugin;
+
+/// Uses CPAL for audio and midir for MIDI.
+pub struct Cpal {
+    // TODO:
+    // TODO: MIDI
+}
+
+impl Backend for Cpal {
+    fn run(
+        &mut self,
+        mut cb: impl FnMut(&mut Buffer, Transport, &[NoteEvent], &mut Vec<NoteEvent>) -> bool
+            + 'static
+            + Send,
+    ) {
+        // TODO:
+    }
+}
+
+impl Cpal {
+    /// Initialize the backend with the specified host. Returns an error if this failed for whatever
+    /// reason.
+    pub fn new<P: Plugin>(config: WrapperConfig, cpal_host_id: cpal::HostId) -> Result<Self> {
+        let host = cpal::host_from_id(cpal_host_id).context("The Audio API is unavailable")?;
+
+        // No input device is connected unless requested by the user to avoid feedback loops
+        let input_device = config
+            .input_device
+            .map(|name| -> Result<cpal::Device> {
+                let device = host
+                    .input_devices()
+                    .context("No audio input devices available")?
+                    // `.name()` returns a `Result` with a non-Eq error type so you can't compare this
+                    // directly
+                    .find(|d| d.name().as_deref().map(|n| n == name).unwrap_or(false))
+                    .with_context(|| {
+                        // This is a bit awkward, but instead of adding a dedicated option we'll just
+                        // list all of the available devices in the error message when the chosen device
+                        // does not exist
+                        let mut message =
+                            format!("Unknown input device '{name}'. Available devices are:");
+                        for device_name in host.input_devices().unwrap().flat_map(|d| d.name()) {
+                            message.push_str(&format!("\n{device_name}"))
+                        }
+
+                        message
+                    })?;
+
+                Ok(device)
+            })
+            .transpose()?;
+
+        let output_device = match config.output_device {
+            Some(name) => host
+                .output_devices()
+                .context("No audio output devices available")?
+                .find(|d| d.name().as_deref().map(|n| n == name).unwrap_or(false))
+                .with_context(|| {
+                    let mut message =
+                        format!("Unknown output device '{name}'. Available devices are:");
+                    for device_name in host.output_devices().unwrap().flat_map(|d| d.name()) {
+                        message.push_str(&format!("\n{device_name}"))
+                    }
+
+                    message
+                })?,
+            None => host
+                .default_output_device()
+                .context("No default audio output device available")?,
+        };
+
+        anyhow::bail!("Not yet implemented");
+    }
+}

src/wrapper/standalone/config.rs

@@ -10,6 +10,17 @@ pub struct WrapperConfig {
     /// no audio input or output if the other backends are not available.
     #[clap(value_parser, short = 'b', long, default_value = "auto")]
     pub backend: BackendType,
+    /// The input device for the ALSA, CoreAudio, and WASAPI backends. No input will be connected if
+    /// this is not specified.
+    ///
+    /// Specifying an empty string or other invalid value will list all available input devices.
+    #[clap(value_parser, long)]
+    pub input_device: Option<String>,
+    /// The output device for the ALSA, CoreAudio, and WASAPI backends.
+    ///
+    /// Specifying an empty string or other invalid value will list all available output devices.
+    #[clap(value_parser, long)]
+    pub output_device: Option<String>,
 
     // These will default to the plugin's default input and output channel count. We could set the
     // default value here to match those, but that would require a custom Args+FromArgMatches
@@ -81,6 +92,15 @@ pub enum BackendType {
     Auto,
     /// Use JACK for audio and MIDI.
     Jack,
+    /// Use ALSA for audio and MIDI.
+    #[cfg(target_os = "linux")]
+    Alsa,
+    /// Use CoreAudio for audio and MIDI.
+    #[cfg(target_os = "macos")]
+    CoreAudio,
+    /// Use WASAPI for audio and MIDI.
+    #[cfg(target_os = "windows")]
+    Wasapi,
     /// Does not playback or receive any audio or MIDI.
     Dummy,
 }