Add AsyncExecutor support to ProcessContext

BREAKING_CHANGES.md

@@ -8,6 +8,8 @@ code then it will not be listed here.
 
 ## [2022-10-22]
 
+- The `&mut impl ProcessContext` argument to `Plugin::process()` needs to be
+  changed to `&mut impl ProcessContext<Self>`.
 - The `&mut impl InitContext` argument to `Plugin::initialize()` needs to be
   changed to `&mut impl InitContext<Self>`.
 - NIH-plug has gained support for asynchronously running background tasks in a

README.md

@@ -83,7 +83,7 @@ Scroll down for more information on the underlying plugin framework.
 - Standalone binaries can be made by calling `nih_export_standalone(Foo)` from
   your `main()` function. Standalones come with a CLI for configuration and full
   JACK audio, MIDI, and transport support.
-- Declarative parameter handling without any boilerplate.
+- Rich declarative parameter system without any boilerplate.
   - Define parameters for your plugin by adding `FloatParam`, `IntParam`,
     `BoolParam`, and `EnumParam<T>` fields to your parameter struct, assign
     stable IDs to them with the `#[id = "foobar"]`, and a `#[derive(Params)]`
@@ -107,6 +107,8 @@ Scroll down for more information on the underlying plugin framework.
     trait to enable compile time generated parameters and other bespoke
     functionality.
 - Stateful. Behaves mostly like JUCE, just without all of the boilerplate.
+- Comes with a simple yet powerful way to asynchronously run background tasks
+  from a plugin that's both type-safe and realtime-safe.
 - Does not make any assumptions on how you want to process audio, but does come
   with utilities and adapters to help with common access patterns.
   - Efficiently iterate over an audio buffer either per-sample per-channel,

plugins/crisp/src/lib.rs

@@ -356,7 +356,7 @@ impl Plugin for Crisp {
         &mut self,
         buffer: &mut Buffer,
         _aux: &mut AuxiliaryBuffers,
-        _context: &mut impl ProcessContext,
+        _context: &mut impl ProcessContext<Self>,
     ) -> ProcessStatus {
         for (_, mut block) in buffer.iter_blocks(BLOCK_SIZE) {
             let mut rm_outputs = [[0.0; NUM_CHANNELS as usize]; BLOCK_SIZE];

plugins/crossover/src/lib.rs

@@ -228,7 +228,7 @@ impl Plugin for Crossover {
         &mut self,
         buffer: &mut Buffer,
         aux: &mut AuxiliaryBuffers,
-        context: &mut impl ProcessContext,
+        context: &mut impl ProcessContext<Self>,
     ) -> ProcessStatus {
         // Right now both crossover types only do 24 dB/octave Linkwitz-Riley style crossovers
         match self.params.crossover_type.value() {

plugins/diopser/src/lib.rs

@@ -288,7 +288,7 @@ impl Plugin for Diopser {
         &mut self,
         buffer: &mut Buffer,
         _aux: &mut AuxiliaryBuffers,
-        _context: &mut impl ProcessContext,
+        _context: &mut impl ProcessContext<Self>,
     ) -> ProcessStatus {
         // Since this is an expensive operation, only update the filters when it's actually
         // necessary, and allow smoothing only every n samples using the automation precision

plugins/examples/gain/src/lib.rs

@@ -156,7 +156,7 @@ impl Plugin for Gain {
         &mut self,
         buffer: &mut Buffer,
         _aux: &mut AuxiliaryBuffers,
-        _context: &mut impl ProcessContext,
+        _context: &mut impl ProcessContext<Self>,
     ) -> ProcessStatus {
         for channel_samples in buffer.iter_samples() {
             // Smoothing is optionally built into the parameters themselves

plugins/examples/gain_gui_egui/src/lib.rs

@@ -174,7 +174,7 @@ impl Plugin for Gain {
         &mut self,
         buffer: &mut Buffer,
         _aux: &mut AuxiliaryBuffers,
-        _context: &mut impl ProcessContext,
+        _context: &mut impl ProcessContext<Self>,
     ) -> ProcessStatus {
         for channel_samples in buffer.iter_samples() {
             let mut amplitude = 0.0;

plugins/examples/gain_gui_iced/src/lib.rs

@@ -119,7 +119,7 @@ impl Plugin for Gain {
         &mut self,
         buffer: &mut Buffer,
         _aux: &mut AuxiliaryBuffers,
-        _context: &mut impl ProcessContext,
+        _context: &mut impl ProcessContext<Self>,
     ) -> ProcessStatus {
         for channel_samples in buffer.iter_samples() {
             let mut amplitude = 0.0;

plugins/examples/gain_gui_vizia/src/lib.rs

@@ -118,7 +118,7 @@ impl Plugin for Gain {
         &mut self,
         buffer: &mut Buffer,
         _aux: &mut AuxiliaryBuffers,
-        _context: &mut impl ProcessContext,
+        _context: &mut impl ProcessContext<Self>,
     ) -> ProcessStatus {
         for channel_samples in buffer.iter_samples() {
             let mut amplitude = 0.0;

plugins/examples/midi_inverter/src/lib.rs

@@ -44,7 +44,7 @@ impl Plugin for MidiInverter {
         &mut self,
         _buffer: &mut Buffer,
         _aux: &mut AuxiliaryBuffers,
-        context: &mut impl ProcessContext,
+        context: &mut impl ProcessContext<Self>,
     ) -> ProcessStatus {
         // We'll invert the channel, note index, velocity, pressure, CC value, pitch bend, and
         // anything else that is invertable for all events we receive

plugins/examples/poly_mod_synth/src/lib.rs

@@ -177,7 +177,7 @@ impl Plugin for PolyModSynth {
         &mut self,
         buffer: &mut Buffer,
         _aux: &mut AuxiliaryBuffers,
-        context: &mut impl ProcessContext,
+        context: &mut impl ProcessContext<Self>,
     ) -> ProcessStatus {
         // NIH-plug has a block-splitting adapter for `Buffer`. While this works great for effect
         // plugins, for polyphonic synths the block size should be `min(MAX_BLOCK_SIZE,
@@ -443,7 +443,7 @@ impl PolyModSynth {
     /// voice will be stolen. Returns a reference to the new voice.
     fn start_voice(
         &mut self,
-        context: &mut impl ProcessContext,
+        context: &mut impl ProcessContext<Self>,
         sample_offset: u32,
         voice_id: Option<i32>,
         channel: u8,
@@ -544,7 +544,7 @@ impl PolyModSynth {
     /// matching voices.
     fn choke_voices(
         &mut self,
-        context: &mut impl ProcessContext,
+        context: &mut impl ProcessContext<Self>,
         sample_offset: u32,
         voice_id: Option<i32>,
         channel: u8,

plugins/examples/sine/src/lib.rs

@@ -145,7 +145,7 @@ impl Plugin for Sine {
         &mut self,
         buffer: &mut Buffer,
         _aux: &mut AuxiliaryBuffers,
-        context: &mut impl ProcessContext,
+        context: &mut impl ProcessContext<Self>,
     ) -> ProcessStatus {
         let mut next_event = context.next_event();
         for (sample_id, channel_samples) in buffer.iter_samples().enumerate() {

plugins/examples/stft/src/lib.rs

@@ -132,7 +132,7 @@ impl Plugin for Stft {
         &mut self,
         buffer: &mut Buffer,
         _aux: &mut AuxiliaryBuffers,
-        _context: &mut impl ProcessContext,
+        _context: &mut impl ProcessContext<Self>,
     ) -> ProcessStatus {
         self.stft
             .process_overlap_add(buffer, 1, |_channel_idx, real_fft_buffer| {

plugins/loudness_war_winner/src/lib.rs

@@ -174,7 +174,7 @@ impl Plugin for LoudnessWarWinner {
         &mut self,
         buffer: &mut Buffer,
         _aux: &mut AuxiliaryBuffers,
-        _context: &mut impl ProcessContext,
+        _context: &mut impl ProcessContext<Self>,
     ) -> ProcessStatus {
         for mut channel_samples in buffer.iter_samples() {
             let output_gain = self.params.output_gain.smoothed.next();

plugins/puberty_simulator/src/lib.rs

@@ -224,7 +224,7 @@ impl Plugin for PubertySimulator {
         &mut self,
         buffer: &mut Buffer,
         _aux: &mut AuxiliaryBuffers,
-        context: &mut impl ProcessContext,
+        context: &mut impl ProcessContext<Self>,
     ) -> ProcessStatus {
         // Compensate for the window function, the overlap, and the extra gain introduced by the
         // IDFT operation

plugins/safety_limiter/src/lib.rs

@@ -200,7 +200,7 @@ impl Plugin for SafetyLimiter {
         &mut self,
         buffer: &mut Buffer,
         _aux: &mut AuxiliaryBuffers,
-        _context: &mut impl ProcessContext,
+        _context: &mut impl ProcessContext<Self>,
     ) -> ProcessStatus {
         // Don't do anything when bouncing
         if self.buffer_config.process_mode == ProcessMode::Offline {

plugins/spectral_compressor/src/lib.rs

@@ -346,7 +346,7 @@ impl Plugin for SpectralCompressor {
         &mut self,
         buffer: &mut Buffer,
         aux: &mut AuxiliaryBuffers,
-        context: &mut impl ProcessContext,
+        context: &mut impl ProcessContext<Self>,
     ) -> ProcessStatus {
         // If the window size has changed since the last process call, reset the buffers and chance
         // our latency. All of these buffers already have enough capacity so this won't allocate.

src/context.rs

@@ -50,7 +50,11 @@ pub trait InitContext<P: Plugin> {
 //
 // The implementing wrapper needs to be able to handle concurrent requests, and it should perform
 // the actual callback within [MainThreadQueue::do_maybe_async].
-pub trait ProcessContext {
+pub trait ProcessContext<P: Plugin> {
+    /// Run a task on a background thread. This allows defering expensive background tasks for
+    /// alter. As long as creating the `task` is realtime-safe, this operation is too.
+    fn execute_async(&self, task: <P::AsyncExecutor as AsyncExecutor>::Task);
+
     /// Get the current plugin API.
     fn plugin_api(&self) -> PluginApi;
 

src/event_loop.rs

@@ -10,6 +10,8 @@ mod linux;
 #[cfg(target_os = "windows")]
 mod windows;
 
+use crate::prelude::AsyncExecutor;
+
 #[cfg(all(target_family = "unix", not(target_os = "macos")))]
 pub(crate) use self::linux::LinuxEventLoop as OsEventLoop;
 // For now, also use the Linux event loop on macOS so it at least compiles
@@ -38,6 +40,9 @@ where
 {
     /// Create and start a new event loop. The thread this is called on will be designated as the
     /// main thread, so this should be called when constructing the wrapper.
+    //
+    // TODO: This use of `Weak` is a bit weird outside the context of the VST3 wrapper, but the
+    //       alternatives didn't feel right either.
     fn new_and_spawn(executor: Weak<E>) -> Self;
 
     /// Either post the function to the task queue so it can be delegated to the main thread, or
@@ -63,3 +68,11 @@ pub(crate) trait MainThreadExecutor<T>: Send + Sync {
     /// assume (and can only assume) that this is called from the main thread.
     unsafe fn execute(&self, task: T);
 }
+
+/// An adapter implementation to allow any [`AsyncExecutor`] to function as a
+/// [`MainThreadExecutor`]. Used only in the standalone wrapper.
+impl<T: Send, E: AsyncExecutor<Task = T>> MainThreadExecutor<T> for E {
+    unsafe fn execute(&self, task: T) {
+        AsyncExecutor::execute(self, task);
+    }
+}

src/plugin.rs

@@ -195,7 +195,7 @@ pub trait Plugin: Default + Send + 'static {
         &mut self,
         buffer: &mut Buffer,
         aux: &mut AuxiliaryBuffers,
-        context: &mut impl ProcessContext,
+        context: &mut impl ProcessContext<Self>,
     ) -> ProcessStatus;
 
     /// Called when the plugin is deactivated. The host will call

src/wrapper/clap/context.rs

@@ -2,9 +2,10 @@ use atomic_refcell::AtomicRefMut;
 use std::collections::VecDeque;
 use std::sync::Arc;
 
-use super::wrapper::{OutputParamEvent, Wrapper};
+use super::wrapper::{OutputParamEvent, Task, Wrapper};
 use crate::async_executor::AsyncExecutor;
 use crate::context::{GuiContext, InitContext, PluginApi, ProcessContext, Transport};
+use crate::event_loop::EventLoop;
 use crate::midi::NoteEvent;
 use crate::params::internals::ParamPtr;
 use crate::plugin::ClapPlugin;
@@ -131,7 +132,15 @@ impl<P: ClapPlugin> InitContext<P> for WrapperInitContext<'_, P> {
     }
 }
 
-impl<P: ClapPlugin> ProcessContext for WrapperProcessContext<'_, P> {
+impl<P: ClapPlugin> ProcessContext<P> for WrapperProcessContext<'_, P> {
+    fn execute_async(
+        &self,
+        task: <<P as crate::prelude::Plugin>::AsyncExecutor as AsyncExecutor>::Task,
+    ) {
+        let task_posted = self.wrapper.do_maybe_async(Task::PluginTask(task));
+        nih_debug_assert!(task_posted, "The task queue is full, dropping task...");
+    }
+
     fn plugin_api(&self) -> PluginApi {
         PluginApi::Clap
     }

src/wrapper/clap/wrapper.rs

@@ -76,6 +76,7 @@ use std::time::Duration;
 use super::context::{WrapperGuiContext, WrapperInitContext, WrapperProcessContext};
 use super::descriptor::PluginDescriptor;
 use super::util::ClapPtr;
+use crate::async_executor::AsyncExecutor;
 use crate::buffer::Buffer;
 use crate::context::Transport;
 use crate::editor::{Editor, ParentWindowHandle};
@@ -84,7 +85,7 @@ use crate::midi::{MidiConfig, NoteEvent};
 use crate::params::internals::ParamPtr;
 use crate::params::{ParamFlags, Params};
 use crate::plugin::{
-    AuxiliaryBuffers, BufferConfig, BusConfig, ClapPlugin, ProcessMode, ProcessStatus,
+    AuxiliaryBuffers, BufferConfig, BusConfig, ClapPlugin, Plugin, ProcessMode, ProcessStatus,
 };
 use crate::util::permit_alloc;
 use crate::wrapper::clap::util::{read_stream, write_stream};
@@ -257,7 +258,7 @@ pub struct Wrapper<P: ClapPlugin> {
     /// implementations. Instead, we'll post tasks to this queue, ask the host to call
     /// [`on_main_thread()`][Self::on_main_thread()] on the main thread, and then continue to pop
     /// tasks off this queue there until it is empty.
-    tasks: ArrayQueue<Task>,
+    tasks: ArrayQueue<Task<P>>,
     /// The ID of the main thread. In practice this is the ID of the thread that created this
     /// object. If the host supports the thread check extension (and
     /// [`host_thread_check`][Self::host_thread_check] thus contains a value), then that extension
@@ -268,8 +269,10 @@ pub struct Wrapper<P: ClapPlugin> {
 /// Tasks that can be sent from the plugin to be executed on the main thread in a non-blocking
 /// realtime-safe way. Instead of using a random thread or the OS' event loop like in the Linux
 /// implementation, this uses [`clap_host::request_callback()`] instead.
-#[derive(Debug)]
+#[allow(clippy::enum_variant_names)]
-pub enum Task {
+pub enum Task<P: Plugin> {
+    /// Execute one of the plugin's background tasks.
+    PluginTask(<P::AsyncExecutor as AsyncExecutor>::Task),
     /// Inform the host that the latency has changed.
     LatencyChanged,
     /// Inform the host that the voice info has changed.
@@ -311,12 +314,12 @@ pub enum OutputParamEvent {
 
 /// Because CLAP has this [`clap_host::request_host_callback()`] function, we don't need to use
 /// `OsEventLoop` and can instead just request a main thread callback directly.
-impl<P: ClapPlugin> EventLoop<Task, Wrapper<P>> for Wrapper<P> {
+impl<P: ClapPlugin> EventLoop<Task<P>, Wrapper<P>> for Wrapper<P> {
     fn new_and_spawn(_executor: std::sync::Weak<Self>) -> Self {
         panic!("What are you doing");
     }
 
-    fn do_maybe_async(&self, task: Task) -> bool {
+    fn do_maybe_async(&self, task: Task<P>) -> bool {
         if self.is_main_thread() {
             unsafe { self.execute(task) };
             true
@@ -346,10 +349,11 @@ impl<P: ClapPlugin> EventLoop<Task, Wrapper<P>> for Wrapper<P> {
     }
 }
 
-impl<P: ClapPlugin> MainThreadExecutor<Task> for Wrapper<P> {
+impl<P: ClapPlugin> MainThreadExecutor<Task<P>> for Wrapper<P> {
-    unsafe fn execute(&self, task: Task) {
+    unsafe fn execute(&self, task: Task<P>) {
         // This function is always called from the main thread, from [Self::on_main_thread].
         match task {
+            Task::PluginTask(task) => AsyncExecutor::execute(&self.async_executor, task),
             Task::LatencyChanged => match &*self.host_latency.borrow() {
                 Some(host_latency) => {
                     // XXX: The CLAP docs mention that you should request a restart if this happens

src/wrapper/standalone/context.rs

@@ -5,6 +5,7 @@ use super::backend::Backend;
 use super::wrapper::{GuiTask, Wrapper};
 use crate::async_executor::AsyncExecutor;
 use crate::context::{GuiContext, InitContext, PluginApi, ProcessContext, Transport};
+use crate::event_loop::EventLoop;
 use crate::midi::NoteEvent;
 use crate::params::internals::ParamPtr;
 use crate::plugin::Plugin;
@@ -96,7 +97,12 @@ impl<P: Plugin, B: Backend> InitContext<P> for WrapperInitContext<'_, P, B> {
     }
 }
 
-impl<P: Plugin, B: Backend> ProcessContext for WrapperProcessContext<'_, P, B> {
+impl<P: Plugin, B: Backend> ProcessContext<P> for WrapperProcessContext<'_, P, B> {
+    fn execute_async(&self, task: <P::AsyncExecutor as AsyncExecutor>::Task) {
+        let task_posted = self.wrapper.event_loop.do_maybe_async(task);
+        nih_debug_assert!(task_posted, "The task queue is full, dropping task...");
+    }
+
     fn plugin_api(&self) -> PluginApi {
         PluginApi::Standalone
     }

src/wrapper/standalone/wrapper.rs

@@ -13,8 +13,10 @@ use std::thread;
 use super::backend::Backend;
 use super::config::WrapperConfig;
 use super::context::{WrapperGuiContext, WrapperInitContext, WrapperProcessContext};
+use crate::async_executor::AsyncExecutor;
 use crate::context::Transport;
 use crate::editor::{Editor, ParentWindowHandle};
+use crate::event_loop::{EventLoop, OsEventLoop};
 use crate::midi::NoteEvent;
 use crate::params::internals::ParamPtr;
 use crate::params::{ParamFlags, Params};
@@ -36,7 +38,7 @@ pub struct Wrapper<P: Plugin, B: Backend> {
     /// The wrapped plugin instance.
     plugin: Mutex<P>,
     /// The plugin's background task executor.
-    pub async_executor: P::AsyncExecutor,
+    pub async_executor: Arc<P::AsyncExecutor>,
     /// The plugin's parameters. These are fetched once during initialization. That way the
     /// `ParamPtr`s are guaranteed to live at least as long as this object and we can interact with
     /// the `Params` object without having to acquire a lock on `plugin`.
@@ -52,6 +54,14 @@ pub struct Wrapper<P: Plugin, B: Backend> {
     /// creating an editor.
     pub editor: Option<Arc<Mutex<Box<dyn Editor>>>>,
 
+    /// A realtime-safe task queue so the plugin can schedule tasks that need to be run later on the
+    /// GUI thread. See the same field in the VST3 wrapper for more information on why this looks
+    /// the way it does.
+    ///
+    /// This is only used for executing [`AsyncExecutor`] tasks, so it's parameterized directly over
+    /// that using a special `MainThreadExecutor` wrapper around `AsyncExecutor`.
+    pub(crate) event_loop: OsEventLoop<<P::AsyncExecutor as AsyncExecutor>::Task, P::AsyncExecutor>,
+
     config: WrapperConfig,
 
     /// The bus and buffer configurations are static for the standalone target.
@@ -134,7 +144,7 @@ impl<P: Plugin, B: Backend> Wrapper<P, B> {
     /// not accept the IO configuration from the wrapper config.
     pub fn new(backend: B, config: WrapperConfig) -> Result<Arc<Self>, WrapperError> {
         let plugin = P::default();
-        let async_executor = plugin.async_executor();
+        let async_executor = Arc::new(plugin.async_executor());
         let params = plugin.params();
         let editor = plugin.editor().map(|editor| Arc::new(Mutex::new(editor)));
 
@@ -181,7 +191,7 @@ impl<P: Plugin, B: Backend> Wrapper<P, B> {
             backend: AtomicRefCell::new(backend),
 
             plugin: Mutex::new(plugin),
-            async_executor,
+            async_executor: async_executor.clone(),
             params,
             known_parameters: param_map.iter().map(|(_, ptr, _)| *ptr).collect(),
             param_map: param_map
@@ -190,6 +200,8 @@ impl<P: Plugin, B: Backend> Wrapper<P, B> {
                 .collect(),
             editor,
 
+            event_loop: OsEventLoop::new_and_spawn(Arc::downgrade(&async_executor)),
+
             bus_config: BusConfig {
                 num_input_channels: config.input_channels.unwrap_or(P::DEFAULT_INPUT_CHANNELS),
                 num_output_channels: config.output_channels.unwrap_or(P::DEFAULT_OUTPUT_CHANNELS),

src/wrapper/vst3/context.rs

@@ -134,7 +134,12 @@ impl<P: Vst3Plugin> InitContext<P> for WrapperInitContext<'_, P> {
     }
 }
 
-impl<P: Vst3Plugin> ProcessContext for WrapperProcessContext<'_, P> {
+impl<P: Vst3Plugin> ProcessContext<P> for WrapperProcessContext<'_, P> {
+    fn execute_async(&self, task: <P::AsyncExecutor as AsyncExecutor>::Task) {
+        let task_posted = self.inner.do_maybe_async(Task::PluginTask(task));
+        nih_debug_assert!(task_posted, "The task queue is full, dropping task...");
+    }
+
     fn plugin_api(&self) -> PluginApi {
         PluginApi::Vst3
     }

src/wrapper/vst3/inner.rs

@@ -14,6 +14,7 @@ use super::note_expressions::NoteExpressionController;
 use super::param_units::ParamUnits;
 use super::util::{ObjectPtr, VstPtr, VST3_MIDI_PARAMS_END, VST3_MIDI_PARAMS_START};
 use super::view::WrapperView;
+use crate::async_executor::AsyncExecutor;
 use crate::buffer::Buffer;
 use crate::context::Transport;
 use crate::editor::Editor;
@@ -21,7 +22,7 @@ use crate::event_loop::{EventLoop, MainThreadExecutor, OsEventLoop};
 use crate::midi::{MidiConfig, NoteEvent};
 use crate::params::internals::ParamPtr;
 use crate::params::{ParamFlags, Params};
-use crate::plugin::{BufferConfig, BusConfig, ProcessMode, ProcessStatus, Vst3Plugin};
+use crate::plugin::{BufferConfig, BusConfig, Plugin, ProcessMode, ProcessStatus, Vst3Plugin};
 use crate::wrapper::state::{self, PluginState};
 use crate::wrapper::util::{hash_param_id, process_wrapper};
 
@@ -59,7 +60,7 @@ pub(crate) struct WrapperInner<P: Vst3Plugin> {
     /// reason to mutably borrow the event loop, so reads will never be contested.
     ///
     /// TODO: Is there a better type for Send+Sync late initialization?
-    pub event_loop: AtomicRefCell<Option<OsEventLoop<Task, Self>>>,
+    pub event_loop: AtomicRefCell<Option<OsEventLoop<Task<P>, Self>>>,
 
     /// Whether the plugin is currently processing audio. In other words, the last state
     /// `IAudioProcessor::setActive()` has been called with.
@@ -150,8 +151,10 @@ pub(crate) struct WrapperInner<P: Vst3Plugin> {
 /// Tasks that can be sent from the plugin to be executed on the main thread in a non-blocking
 /// realtime-safe way (either a random thread or `IRunLoop` on Linux, the OS' message loop on
 /// Windows and macOS).
-#[derive(Debug, Clone)]
+#[allow(clippy::enum_variant_names)]
-pub enum Task {
+pub enum Task<P: Plugin> {
+    /// Execute one of the plugin's background tasks.
+    PluginTask(<P::AsyncExecutor as AsyncExecutor>::Task),
     /// Trigger a restart with the given restart flags. This is a bit set of the flags from
     /// [`vst3_sys::vst::RestartFlags`].
     TriggerRestart(i32),
@@ -353,7 +356,7 @@ impl<P: Vst3Plugin> WrapperInner<P> {
     ///
     /// If the task queue is full, then this will return false.
     #[must_use]
-    pub fn do_maybe_async(&self, task: Task) -> bool {
+    pub fn do_maybe_async(&self, task: Task<P>) -> bool {
         let event_loop = self.event_loop.borrow();
         let event_loop = event_loop.as_ref().unwrap();
         if event_loop.is_main_thread() {
@@ -514,8 +517,8 @@ impl<P: Vst3Plugin> WrapperInner<P> {
     }
 }
 
-impl<P: Vst3Plugin> MainThreadExecutor<Task> for WrapperInner<P> {
+impl<P: Vst3Plugin> MainThreadExecutor<Task<P>> for WrapperInner<P> {
-    unsafe fn execute(&self, task: Task) {
+    unsafe fn execute(&self, task: Task<P>) {
         // This function is always called from the main thread
         // TODO: When we add GUI resizing and context menus, this should propagate those events to
         //       `IRunLoop` on Linux to keep REAPER happy. That does mean a double spool, but we can
@@ -523,6 +526,7 @@ impl<P: Vst3Plugin> MainThreadExecutor<Task> for WrapperInner<P> {
         //       function for checking if a to be scheduled task can be handled right there and
         //       then).
         match task {
+            Task::PluginTask(task) => AsyncExecutor::execute(&self.async_executor, task),
             Task::TriggerRestart(flags) => match &*self.component_handler.borrow() {
                 Some(handler) => {
                     handler.restart_component(flags);

src/wrapper/vst3/view.rs

@@ -96,7 +96,7 @@ struct RunLoopEventHandler<P: Vst3Plugin> {
     /// implementations. Instead, we'll post tasks to this queue, ask the host to call
     /// [`on_main_thread()`][Self::on_main_thread()] on the main thread, and then continue to pop
     /// tasks off this queue there until it is empty.
-    tasks: ArrayQueue<Task>,
+    tasks: ArrayQueue<Task<P>>,
 }
 
 impl<P: Vst3Plugin> WrapperView<P> {
@@ -162,7 +162,7 @@ impl<P: Vst3Plugin> WrapperView<P> {
     /// run on the host's UI thread. If not, then this will return an `Err` value containing the
     /// task so it can be run elsewhere.
     #[cfg(target_os = "linux")]
-    pub fn do_maybe_in_run_loop(&self, task: Task) -> Result<(), Task> {
+    pub fn do_maybe_in_run_loop(&self, task: Task<P>) -> Result<(), Task<P>> {
         match &*self.run_loop_event_handler.0.read() {
             Some(run_loop) => run_loop.post_task(task),
             None => Err(task),
@@ -174,7 +174,7 @@ impl<P: Vst3Plugin> WrapperView<P> {
     /// task so it can be run elsewhere.
     #[cfg(not(target_os = "linux"))]
     #[must_use]
-    pub fn do_maybe_in_run_loop(&self, task: Task) -> Result<(), Task> {
+    pub fn do_maybe_in_run_loop(&self, task: Task<P>) -> Result<(), Task<P>> {
         Err(task)
     }
 }
@@ -222,7 +222,7 @@ impl<P: Vst3Plugin> RunLoopEventHandler<P> {
 
     /// Post a task to the tasks queue so it will be run on the host's GUI thread later. Returns the
     /// task if the queue is full and the task could not be posted.
-    pub fn post_task(&self, task: Task) -> Result<(), Task> {
+    pub fn post_task(&self, task: Task<P>) -> Result<(), Task<P>> {
         self.tasks.push(task)?;
 
         // We need to use a Unix domain socket to let the host know to call our event handler. In