Add a (not yet functional) standalone exporter

.github/workflows/test.yml

@@ -61,7 +61,7 @@ jobs:
           command: build
           # Don't use --all-features as that will enable a whole bunch of
           # conflicting iced features
-          args: --workspace --features "simd"
+          args: --workspace --features "simd,standalone"
       - name: Run the tests
         uses: actions-rs/cargo@v1
         with:

Cargo.toml

@@ -35,13 +35,18 @@ members = [
 
 [features]
 default = ["vst3"]
+
 # Enabling this feature will cause the plugin to terminate when allocations
 # occur in the processing function while compiling in debug mode. Keep in mind
 # that most panic handlers will also allocate, so temporarily disabling this
 # feature may be necessary when debugging panics in DSP code.
 assert_process_allocs = ["dep:assert_no_alloc"]
-# Enables the `nih_export_vst3()` macro. Enabled by default. This feature exists
+# Enables an export target for standalone binaries through the
-# mostly for GPL-compliance reasons, since even if you don't use the VST3
+# `nih_export_standalone()` function. Disabled by default, as this requires
+# building additional dependencies for audio and MIDI handling.
+standalone = []
+# 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
 # `vst3-sys` create.
 vst3 = ["dep:vst3-sys"]

README.md

@@ -54,6 +54,8 @@ for download links.
 - Supports both VST3 and [CLAP](https://github.com/free-audio/clap) by simply
   adding the corresponding `nih_export_<api>!(Foo)` macro to your plugin's
   library.
+- Standalone binaries can be made by calling `nih_export_standalone(Foo)` from
+  your `main()` function.
 - Declarative parameter handling without any boilerplate.
   - Define parameters for your plugin by adding `FloatParam`, `IntParam`,
     `BoolParam`, and `EnumParam<T>` fields to your parameter struct, assign

nih_plug_xtask/src/lib.rs

@@ -175,6 +175,8 @@ pub fn bundle(package: &str, args: &[String]) -> Result<()> {
         }
     }
 
+    // TODO: Add support for binary targets. This would simply copy/reflink the binary to the
+    //       `bundled` directory to make it easier to ship all versions of a plugin.
     let compilation_target = compilation_target(cross_compile_target.as_deref())?;
     let lib_path = target_base(cross_compile_target.as_deref())?
         .join(if is_release_build { "release" } else { "debug" })

src/plugin.rs

@@ -22,7 +22,6 @@ use crate::param::internals::Params;
 /// - Multiple output busses
 /// - Special handling for offline processing
 /// - MIDI SysEx and MIDI2 for CLAP, note expressions and MIDI1 are already supported
-/// - An export target for a standalone application
 #[allow(unused_variables)]
 pub trait Plugin: Default + Send + Sync + 'static {
     const NAME: &'static str;

src/prelude.rs

@@ -9,6 +9,8 @@ pub use crate::nih_trace;
 
 #[cfg(feature = "vst3")]
 pub use crate::nih_export_vst3;
+#[cfg(feature = "standalone")]
+pub use crate::wrapper::standalone::{nih_export_standalone, nih_export_standalone_with_args};
 
 pub use crate::formatters;
 pub use crate::util;

src/wrapper.rs

@@ -5,6 +5,8 @@ pub mod clap;
 pub mod state;
 pub(crate) mod util;
 
+#[cfg(feature = "standalone")]
+pub mod standalone;
 #[cfg(feature = "vst3")]
 pub mod vst3;
 

src/wrapper/standalone.rs

@@ -0,0 +1,35 @@
+//! A standalone plugin target that directly connects to the system's audio and MIDI ports instead
+//! of relying on a plugin host. This is mostly useful for quickly testing GUI changes.
+
+use self::wrapper::Wrapper;
+use crate::plugin::Plugin;
+
+mod wrapper;
+
+/// Open an NIH-plug plugin as a standalone application. If the plugin has an editor, this will open
+/// the editor and block until the editor is closed. Otherwise this will block until SIGINT is
+/// received. This is mainly useful for quickly testing plugin GUIs. You should call this function
+/// from a `main()` function.
+///
+/// By default this will connect to the 'default' audio and MIDI ports. Use the command line options
+/// to change this. `--help` lists all available options.
+///
+/// # TODO
+///
+/// The aforementioned command line options have not yet been implemented.
+//
+// TODO: Actually implement command line flags for changing the IO configuration
+// TODO: Add a way to set the IO configuration at runtime, for instance through the plugin's GUI
+pub fn nih_export_standalone<P: Plugin>() {
+    nih_export_standalone_with_args::<P, _>(std::env::args())
+}
+
+pub fn nih_export_standalone_with_args<P: Plugin, Args: IntoIterator<Item = String>>(args: Args) {
+    // TODO: Do something with the arguments
+
+    Wrapper::<P>::new();
+
+    // TODO: Open the editor if available, do IO things
+    // TODO: If the plugin has an editor, block until the editor is closed. Otherwise block
+    //       indefinitely or until SIGINT (how do signal handlers work in Rust?)
+}

src/wrapper/standalone/wrapper.rs

@@ -0,0 +1,19 @@
+use parking_lot::RwLock;
+
+use crate::plugin::Plugin;
+
+pub struct Wrapper<P: Plugin> {
+    /// The wrapped plugin instance.
+    plugin: RwLock<P>,
+}
+
+impl<P: Plugin> Wrapper<P> {
+    /// Instantiate a new instance of the standalone wrapper.
+    //
+    // TODO: This should take some arguments for the audio and MIDI IO.
+    pub fn new() -> Self {
+        Wrapper {
+            plugin: RwLock::new(P::default()),
+        }
+    }
+}