Initialize the standalone target

src/context.rs

@@ -200,6 +200,7 @@ pub struct ParamSetter<'a> {
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum PluginApi {
     Clap,
+    Standalone,
     Vst3,
 }
 
@@ -207,6 +208,7 @@ impl Display for PluginApi {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
             PluginApi::Clap => write!(f, "CLAP"),
+            PluginApi::Standalone => write!(f, "standalone"),
             PluginApi::Vst3 => write!(f, "VST3"),
         }
     }

src/wrapper/standalone.rs

@@ -1,9 +1,10 @@
 //! 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 self::wrapper::{Wrapper, WrapperConfig};
 use crate::plugin::Plugin;
 
+mod context;
 mod wrapper;
 
 /// Open an NIH-plug plugin as a standalone application. If the plugin has an editor, this will open
@@ -50,7 +51,19 @@ pub fn nih_export_standalone<P: Plugin>() {
 pub fn nih_export_standalone_with_args<P: Plugin, Args: IntoIterator<Item = String>>(args: Args) {
     // TODO: Do something with the arguments
 
-    Wrapper::<P>::new();
+    // FIXME: The configuration should be set based on the command line arguments
+    let config = WrapperConfig {
+        input_channels: 2,
+        output_channels: 2,
+        sample_rate: 44100.0,
+        period_size: 512,
+
+        tempo: 120.0,
+        timesig_num: 4,
+        timesig_denom: 4,
+    };
+
+    Wrapper::<P>::new(config);
 
     // TODO: Open the editor if available, do IO things
     // TODO: If the plugin has an editor, block until the editor is closed. Otherwise block

src/wrapper/standalone/context.rs

@@ -0,0 +1,42 @@
+use super::wrapper::Wrapper;
+use crate::context::{PluginApi, ProcessContext, Transport};
+use crate::midi::NoteEvent;
+use crate::plugin::Plugin;
+
+/// A [`ProcessContext`] implementation for the standalone wrapper. This is a separate object so it
+/// can hold on to lock guards for event queues. Otherwise reading these events would require
+/// constant unnecessary atomic operations to lock the uncontested RwLocks.
+pub(crate) struct WrapperProcessContext<'a, P: Plugin> {
+    pub(super) wrapper: &'a Wrapper<P>,
+    // TODO: Events
+    // pub(super) input_events_guard: AtomicRefMut<'a, VecDeque<NoteEvent>>,
+    // pub(super) output_events_guard: AtomicRefMut<'a, VecDeque<NoteEvent>>,
+    pub(super) transport: Transport,
+}
+
+impl<P: Plugin> ProcessContext for WrapperProcessContext<'_, P> {
+    fn plugin_api(&self) -> PluginApi {
+        PluginApi::Standalone
+    }
+
+    fn transport(&self) -> &Transport {
+        &self.transport
+    }
+
+    fn next_event(&mut self) -> Option<NoteEvent> {
+        nih_debug_assert_failure!("TODO: WrapperProcessContext::next_event()");
+
+        // self.input_events_guard.pop_front()
+        None
+    }
+
+    fn send_event(&mut self, event: NoteEvent) {
+        nih_debug_assert_failure!("TODO: WrapperProcessContext::send_event()");
+
+        // self.output_events_guard.push_back(event);
+    }
+
+    fn set_latency_samples(&self, samples: u32) {
+        nih_debug_assert_failure!("TODO: WrapperProcessContext::set_latency_samples()");
+    }
+}

src/wrapper/standalone/wrapper.rs

@@ -1,19 +1,89 @@
 use parking_lot::RwLock;
+use std::sync::Arc;
 
-use crate::plugin::Plugin;
+use super::context::WrapperProcessContext;
+use crate::context::Transport;
+use crate::plugin::{BufferConfig, BusConfig, Plugin};
+
+/// Configuration for a standalone plugin that would normally be provided by the DAW.
+pub struct WrapperConfig {
+    /// The number of input channels.
+    pub input_channels: u32,
+    /// The number of output channels.
+    pub output_channels: u32,
+    /// The audio backend's sample rate.
+    pub sample_rate: f32,
+    /// The audio backend's period size.
+    pub period_size: u32,
+
+    /// The current tempo.
+    pub tempo: f32,
+    /// The time signature's numerator.
+    pub timesig_num: u32,
+    /// The time signature's denominator.
+    pub timesig_denom: u32,
+}
 
 pub struct Wrapper<P: Plugin> {
     /// The wrapped plugin instance.
     plugin: RwLock<P>,
+
+    config: WrapperConfig,
+
+    /// The bus and buffer configurations are static for the standalone target.
+    bus_config: BusConfig,
+    buffer_config: BufferConfig,
+}
+
+/// Errors that may arise while initializing the wrapped plugins.
+pub enum WrapperError {
+    /// The plugin does not accept the IO configuration from the config.
+    IncompatibleConfig,
+    /// The plugin returned `false` during initialization.
+    InitializationFailed,
 }
 
 impl<P: Plugin> Wrapper<P> {
-    /// Instantiate a new instance of the standalone wrapper.
+    /// Instantiate a new instance of the standalone wrapper. Returns an error if the plugin does
-    //
+    /// not accept the IO configuration from the wrapper config.
-    // TODO: This should take some arguments for the audio and MIDI IO.
+    pub fn new(config: WrapperConfig) -> Result<Arc<Self>, WrapperError> {
-    pub fn new() -> Self {
+        let wrapper = Arc::new(Wrapper {
-        Wrapper {
             plugin: RwLock::new(P::default()),
+            bus_config: BusConfig {
+                num_input_channels: config.input_channels,
+                num_output_channels: config.output_channels,
+            },
+            buffer_config: BufferConfig {
+                sample_rate: config.sample_rate,
+                max_buffer_size: config.period_size,
+            },
+            config,
+        });
+
+        // Right now the IO configuration is fixed in the standalone target, so if the plugin cannot
+        // work with this then we cannot initialize the plugin at all.
+        {
+            let mut plugin = wrapper.plugin.write();
+            if !plugin.accepts_bus_config(&wrapper.bus_config) {
+                return Err(WrapperError::IncompatibleConfig);
+            }
+
+            if !plugin.initialize(
+                &wrapper.bus_config,
+                &wrapper.buffer_config,
+                &mut wrapper.make_process_context(Transport::new(wrapper.config.sample_rate)),
+            ) {
+                return Err(WrapperError::InitializationFailed);
+            }
+        }
+
+        Ok(wrapper)
+    }
+
+    fn make_process_context(&self, transport: Transport) -> WrapperProcessContext<'_, P> {
+        WrapperProcessContext {
+            wrapper: self,
+            transport,
         }
     }
 }