Add a SysExMessage type to Plugin

This is needed to enable sending and receiving SysEx #54. Because
associated type defaults still are not stable, this requires every
plugin that doesn't need this to set this to the unit type:

```rust
type SysExMessage = ();
```

BREAKING_CHANGES.md

@@ -6,6 +6,18 @@ new and what's changed, this document lists all breaking changes in reverse
 chronological order. If a new feature did not require any changes to existing
 code then it will not be listed here.
 
+## [2023-01-31]
+
+- NIH-plug has gained support MIDI SysEx in a simple, type-safe, and
+  realtime-safe way. This sadly does mean that every `Plugin` instance now needs
+  to define a `SysExMessage` type definition and constructor function as Rust
+  does not yet support defaults for associated types (Rust issue
+  [#29661](https://github.com/rust-lang/rust/issues/29661)):
+
+  ```rust
+  type SysExMessage = ();
+  ```
+
 ## [2023-01-12]
 
 - The Vizia dependency has been updated. This updated version uses a new text

README.md

@@ -141,6 +141,9 @@ Scroll down for more information on the underlying plugin framework.
 - Full support for receiving and outputting both modern polyphonic note
   expression events as well as MIDI CCs, channel pressure, and pitch bend for
   CLAP and VST3.
+  - MIDI SysEx is also supported. Plugins can define their own structs or sum
+    types to wrap around those messages so they don't need to interact with raw
+    byte buffers in the process function.
 - Support for flexible dynamic buffer configurations, including multiple input
   and output busses.
 - A plugin bundler accessible through the

plugins/buffr_glitch/src/lib.rs

@@ -186,6 +186,7 @@ impl Plugin for BuffrGlitch {
 
     const MIDI_INPUT: MidiConfig = MidiConfig::Basic;
 
+    type SysExMessage = ();
     type BackgroundTask = ();
 
     fn params(&self) -> Arc<dyn Params> {

plugins/crisp/src/lib.rs

@@ -306,6 +306,7 @@ impl Plugin for Crisp {
 
     const SAMPLE_ACCURATE_AUTOMATION: bool = true;
 
+    type SysExMessage = ();
     type BackgroundTask = ();
 
     fn params(&self) -> Arc<dyn Params> {

plugins/crossover/src/lib.rs

@@ -183,6 +183,7 @@ impl Plugin for Crossover {
         aux_outputs: Some(&["Band 1", "Band 2", "Band 3", "Band 4", "Band 5"]),
     };
 
+    type SysExMessage = ();
     type BackgroundTask = ();
 
     fn params(&self) -> Arc<dyn Params> {

plugins/diopser/src/lib.rs

@@ -118,6 +118,7 @@ impl Plugin for Diopser {
 
     const SAMPLE_ACCURATE_AUTOMATION: bool = true;
 
+    type SysExMessage = ();
     type BackgroundTask = ();
 
     fn params(&self) -> Arc<dyn Params> {

plugins/examples/gain/src/lib.rs

@@ -134,6 +134,10 @@ impl Plugin for Gain {
     // splits.
     const SAMPLE_ACCURATE_AUTOMATION: bool = true;
 
+    // If the plugin can send or receive SysEx messages, it can define a type to wrap around those
+    // messages here. The type implements the `SysExMessage` trait, which allows conversion to and
+    // from plain byte buffers.
+    type SysExMessage = ();
     // More advanced plugins can use this to run expensive background tasks. See the field's
     // documentation for more information. `()` means that the plugin does not have any background
     // tasks.

plugins/examples/gain_gui_egui/src/lib.rs

@@ -83,6 +83,7 @@ impl Plugin for Gain {
 
     const SAMPLE_ACCURATE_AUTOMATION: bool = true;
 
+    type SysExMessage = ();
     type BackgroundTask = ();
 
     fn params(&self) -> Arc<dyn Params> {

plugins/examples/gain_gui_iced/src/lib.rs

@@ -80,6 +80,7 @@ impl Plugin for Gain {
 
     const SAMPLE_ACCURATE_AUTOMATION: bool = true;
 
+    type SysExMessage = ();
     type BackgroundTask = ();
 
     fn params(&self) -> Arc<dyn Params> {

plugins/examples/gain_gui_vizia/src/lib.rs

@@ -79,6 +79,7 @@ impl Plugin for Gain {
 
     const SAMPLE_ACCURATE_AUTOMATION: bool = true;
 
+    type SysExMessage = ();
     type BackgroundTask = ();
 
     fn params(&self) -> Arc<dyn Params> {

plugins/examples/midi_inverter/src/lib.rs

@@ -33,6 +33,7 @@ impl Plugin for MidiInverter {
     const MIDI_OUTPUT: MidiConfig = MidiConfig::MidiCCs;
     const SAMPLE_ACCURATE_AUTOMATION: bool = true;
 
+    type SysExMessage = ();
     type BackgroundTask = ();
 
     fn params(&self) -> Arc<dyn Params> {

plugins/examples/poly_mod_synth/src/lib.rs

@@ -155,6 +155,7 @@ impl Plugin for PolyModSynth {
     const MIDI_INPUT: MidiConfig = MidiConfig::Basic;
     const SAMPLE_ACCURATE_AUTOMATION: bool = true;
 
+    type SysExMessage = ();
     type BackgroundTask = ();
 
     fn params(&self) -> Arc<dyn Params> {

plugins/examples/sine/src/lib.rs

@@ -111,6 +111,7 @@ impl Plugin for Sine {
     const MIDI_INPUT: MidiConfig = MidiConfig::Basic;
     const SAMPLE_ACCURATE_AUTOMATION: bool = true;
 
+    type SysExMessage = ();
     type BackgroundTask = ();
 
     fn params(&self) -> Arc<dyn Params> {

plugins/examples/stft/src/lib.rs

@@ -95,6 +95,7 @@ impl Plugin for Stft {
 
     const SAMPLE_ACCURATE_AUTOMATION: bool = true;
 
+    type SysExMessage = ();
     type BackgroundTask = ();
 
     fn params(&self) -> Arc<dyn Params> {

plugins/loudness_war_winner/src/lib.rs

@@ -123,6 +123,7 @@ impl Plugin for LoudnessWarWinner {
     const DEFAULT_INPUT_CHANNELS: u32 = 2;
     const DEFAULT_OUTPUT_CHANNELS: u32 = 2;
 
+    type SysExMessage = ();
     type BackgroundTask = ();
 
     fn params(&self) -> Arc<dyn Params> {

plugins/puberty_simulator/src/lib.rs

@@ -168,6 +168,7 @@ impl Plugin for PubertySimulator {
     const DEFAULT_INPUT_CHANNELS: u32 = 2;
     const DEFAULT_OUTPUT_CHANNELS: u32 = 2;
 
+    type SysExMessage = ();
     type BackgroundTask = ();
 
     fn params(&self) -> Arc<dyn Params> {

plugins/safety_limiter/src/lib.rs

@@ -158,6 +158,7 @@ impl Plugin for SafetyLimiter {
     const DEFAULT_INPUT_CHANNELS: u32 = 2;
     const DEFAULT_OUTPUT_CHANNELS: u32 = 2;
 
+    type SysExMessage = ();
     type BackgroundTask = ();
 
     fn params(&self) -> Arc<dyn Params> {

plugins/spectral_compressor/src/lib.rs

@@ -265,6 +265,7 @@ impl Plugin for SpectralCompressor {
 
     const SAMPLE_ACCURATE_AUTOMATION: bool = true;
 
+    type SysExMessage = ();
     type BackgroundTask = ();
 
     fn params(&self) -> Arc<dyn Params> {

src/plugin.rs

@@ -3,12 +3,13 @@
 use std::sync::Arc;
 
 use crate::buffer::Buffer;
+use crate::context::gui::AsyncExecutor;
 use crate::context::init::InitContext;
 use crate::context::process::ProcessContext;
 use crate::editor::Editor;
+use crate::midi::sysex::SysExMessage;
 use crate::midi::MidiConfig;
 use crate::params::Params;
-use crate::prelude::AsyncExecutor;
 use crate::wrapper::clap::features::ClapFeature;
 use crate::wrapper::state::PluginState;
 
@@ -26,7 +27,7 @@ pub type TaskExecutor<P> = Box<dyn Fn(<P as Plugin>::BackgroundTask) + Send>;
 ///
 /// Some notable not yet implemented features include:
 ///
-/// - MIDI SysEx and MIDI2 for CLAP, note expressions, polyphonic modulation and MIDI1 are already
+/// - MIDI2 for CLAP, note expressions, polyphonic modulation and MIDI1, and MIDI SysEx are already
 ///   supported
 /// - Audio thread thread pools (with host integration in CLAP)
 #[allow(unused_variables)]
@@ -96,6 +97,12 @@ pub trait Plugin: Default + Send + 'static {
     /// to do offline processing.
     const HARD_REALTIME_ONLY: bool = false;
 
+    /// The plugin's SysEx message type if it supports sending or receiving MIDI SysEx messages, or
+    /// `()` if it does not. This type can be a struct or enum wrapping around one or more message
+    /// types, and the [`SysExMessage`] trait is then used to convert between this type and basic
+    /// byte buffers.
+    type SysExMessage: SysExMessage;
+
     /// A type encoding the different background tasks this plugin wants to run, or `()` if it
     /// doesn't have any background tasks. This is usually set to an enum type. The task type should
     /// not contain any heap allocated data like [`Vec`]s and [`Box`]es. Tasks can be send using the

src/prelude.rs

@@ -16,6 +16,7 @@ pub use crate::context::init::InitContext;
 pub use crate::context::process::ProcessContext;
 // This also includes the derive macro
 pub use crate::editor::{Editor, ParentWindowHandle};
+pub use crate::midi::sysex::SysExMessage;
 pub use crate::midi::{control_change, MidiConfig, NoteEvent};
 pub use crate::params::enums::{Enum, EnumParam};
 pub use crate::params::internals::ParamPtr;