Handle predefined VST3 note expressions

src/wrapper/vst3.rs

@@ -4,6 +4,7 @@ mod util;
 mod context;
 mod factory;
 mod inner;
+mod note_expressions;
 mod param_units;
 mod view;
 mod wrapper;

src/wrapper/vst3/inner.rs

@@ -12,6 +12,7 @@ use vst3_sys::base::{kInvalidArgument, kResultOk, tresult};
 use vst3_sys::vst::{IComponentHandler, RestartFlags};
 
 use super::context::{WrapperGuiContext, WrapperProcessContext};
+use super::note_expressions::NoteExpressionController;
 use super::param_units::ParamUnits;
 use super::util::{ObjectPtr, VstPtr};
 use super::view::WrapperView;
@@ -82,6 +83,11 @@ pub(crate) struct WrapperInner<P: Vst3Plugin> {
     ///       interleave parameter changes and note events, this queue has to be sorted when
     ///       creating the process context
     pub input_events: AtomicRefCell<VecDeque<NoteEvent>>,
+    /// VST3 has several useful predefined note expressions, but for some reason they are the only
+    /// note event type that don't have MIDI note ID and channel fields. So we need to keep track of
+    /// the msot recent VST3 note IDs we've seen, and then map those back to MIDI note IDs and
+    /// channels as needed.
+    pub note_expression_controller: AtomicRefCell<NoteExpressionController>,
     /// Unprocessed parameter changes sent by the host as pairs of `(sample_idx_in_buffer, change)`.
     /// Needed because VST3 does not have a single queue containing all parameter changes. If
     /// `P::SAMPLE_ACCURATE_AUTOMATION` is set, then all parameter changes will be read into this
@@ -248,6 +254,7 @@ impl<P: Vst3Plugin> WrapperInner<P> {
             current_latency: AtomicU32::new(0),
             output_buffer: AtomicRefCell::new(Buffer::default()),
             input_events: AtomicRefCell::new(VecDeque::with_capacity(1024)),
+            note_expression_controller: AtomicRefCell::new(NoteExpressionController::default()),
             input_param_changes: AtomicRefCell::new(BinaryHeap::with_capacity(
                 if P::SAMPLE_ACCURATE_AUTOMATION {
                     4096

src/wrapper/vst3/note_expressions.rs

@@ -0,0 +1,101 @@
+//! Special handling for note expressions, because VST3 makes this a lot more complicated than it
+//! needs to be. We only support the predefined expressions.
+
+use vst3_sys::vst::{NoteExpressionValueEvent, NoteOnEvent};
+
+use crate::midi::NoteEvent;
+
+type MidiNote = u8;
+type MidiChannel = u8;
+type NoteId = i32;
+
+/// The number of notes we'll keep track of for mapping note IDs to channel+note combinations.
+const NOTE_IDS_LEN: usize = 32;
+
+/// VST3 has predefined note expressions just like CLAP, but unlike the other note events these
+/// expressions are identified only with a note ID. To account for that, we'll keep track of the
+/// most recent note IDs we've encountered so we can later map those IDs back to a note and channel
+/// combination.
+#[derive(Debug, Default)]
+pub struct NoteExpressionController {
+    /// The last 32 note IDs we've seen. We'll do a linear search every time we receive a note
+    /// expression value event to find the matching note and channel.
+    note_ids: [(NoteId, MidiNote, MidiChannel); NOTE_IDS_LEN],
+    /// The index in the `note_ids` ring buffer the next event should be inserted at, wraps back
+    /// around to 0 when reaching the end.
+    note_ids_idx: usize,
+}
+
+impl NoteExpressionController {
+    /// Register the note ID from a note on event so it can later be retrieved when handling a note
+    /// expression value event.
+    pub fn register_note(&mut self, event: &NoteOnEvent) {
+        self.note_ids[self.note_ids_idx] = (event.note_id, event.pitch as u8, event.channel as u8);
+        self.note_ids_idx = (self.note_ids_idx + 1) % NOTE_IDS_LEN;
+    }
+
+    /// Translate the note expression value event into an internal NIH-plug event, if we handle the
+    /// expression type from the note expression value event. The timing is provided here because we
+    /// may be splitting buffers on inter-buffer parameter changes.
+    pub fn translate_event(
+        &self,
+        timing: u32,
+        event: &NoteExpressionValueEvent,
+    ) -> Option<NoteEvent> {
+        let (_, note, channel) = *self
+            .note_ids
+            .iter()
+            .find(|(note_id, _, _)| *note_id == event.note_id)?;
+
+        match event.type_id {
+            // kVolumeTypeID
+            0 => Some(NoteEvent::Volume {
+                timing,
+                channel,
+                note,
+                // Because expression values in VST3 are always in the `[0, 1]` range, they added a
+                // 4x scaling factor here to allow the values to go from -infinity to +12 dB
+                gain: event.value as f32 * 4.0,
+            }),
+            // kPanTypeId
+            1 => Some(NoteEvent::Pan {
+                timing,
+                channel,
+                note,
+                // Our panning expressions are symmetrical around 0
+                pan: (event.value as f32 * 2.0) - 1.0,
+            }),
+            // kTuningTypeID
+            2 => Some(NoteEvent::Tuning {
+                timing,
+                channel,
+                note,
+                // This denormalized to the same [-120, 120] range used by CLAP and our expression
+                // events
+                tuning: 240.0 * (event.value as f32 - 0.5),
+            }),
+            // kVibratoTypeID
+            3 => Some(NoteEvent::Vibrato {
+                timing,
+                channel,
+                note,
+                vibrato: event.value as f32,
+            }),
+            // kExpressionTypeID
+            4 => Some(NoteEvent::Brightness {
+                timing,
+                channel,
+                note,
+                brightness: event.value as f32,
+            }),
+            // kBrightnessTypeID
+            5 => Some(NoteEvent::Expression {
+                timing,
+                channel,
+                note,
+                expression: event.value as f32,
+            }),
+            _ => None,
+        }
+    }
+}

src/wrapper/vst3/wrapper.rs

@@ -8,8 +8,8 @@ use vst3_sys::base::{kInvalidArgument, kNoInterface, kResultFalse, kResultOk, tr
 use vst3_sys::base::{IBStream, IPluginBase};
 use vst3_sys::utils::SharedVstPtr;
 use vst3_sys::vst::{
-    kNoProgramListId, kRootUnitId, IAudioProcessor, IComponent, IEditController, IEventList,
-    IParamValueQueue, IParameterChanges, IUnitInfo, ProgramListInfo, TChar, UnitInfo,
+    kNoProgramListId, kRootUnitId, EventTypes, IAudioProcessor, IComponent, IEditController,
+    IEventList, IParamValueQueue, IParameterChanges, IUnitInfo, ProgramListInfo, TChar, UnitInfo,
 };
 use vst3_sys::VST3;
 use widestring::U16CStr;
@@ -746,6 +746,8 @@ impl<P: Vst3Plugin> IAudioProcessor for Wrapper<P> {
 
                 if P::MIDI_INPUT >= MidiConfig::Basic {
                     let mut input_events = self.inner.input_events.borrow_mut();
+                    let mut note_expression_controller =
+                        self.inner.note_expression_controller.borrow_mut();
                     if let Some(events) = data.input_events.upgrade() {
                         let num_events = events.get_event_count();
 
@@ -765,16 +767,20 @@ impl<P: Vst3Plugin> IAudioProcessor for Wrapper<P> {
                             }
 
                             let timing = event.sample_offset as u32 - block_start as u32;
-                            if event.type_ == vst3_sys::vst::EventTypes::kNoteOnEvent as u16 {
+                            if event.type_ == EventTypes::kNoteOnEvent as u16 {
                                 let event = event.event.note_on;
+
+                                // We need to keep track of note IDs to be able to handle not
+                                // expression value events
+                                note_expression_controller.register_note(&event);
+
                                 input_events.push_back(NoteEvent::NoteOn {
                                     timing,
                                     channel: event.channel as u8,
                                     note: event.pitch as u8,
                                     velocity: event.velocity,
                                 });
-                            } else if event.type_ == vst3_sys::vst::EventTypes::kNoteOffEvent as u16
-                            {
+                            } else if event.type_ == EventTypes::kNoteOffEvent as u16 {
                                 let event = event.event.note_off;
                                 input_events.push_back(NoteEvent::NoteOff {
                                     timing,
@@ -782,9 +788,7 @@ impl<P: Vst3Plugin> IAudioProcessor for Wrapper<P> {
                                     note: event.pitch as u8,
                                     velocity: event.velocity,
                                 });
-                            } else if event.type_
-                                == vst3_sys::vst::EventTypes::kPolyPressureEvent as u16
-                            {
+                            } else if event.type_ == EventTypes::kPolyPressureEvent as u16 {
                                 let event = event.event.poly_pressure;
                                 input_events.push_back(NoteEvent::PolyPressure {
                                     timing,
@@ -792,6 +796,17 @@ impl<P: Vst3Plugin> IAudioProcessor for Wrapper<P> {
                                     note: event.pitch as u8,
                                     pressure: event.pressure,
                                 });
+                            } else if event.type_ == EventTypes::kNoteExpressionValueEvent as u16 {
+                                let event = event.event.note_expression_value;
+                                match note_expression_controller.translate_event(timing, &event) {
+                                    Some(translated_event) => {
+                                        input_events.push_back(translated_event)
+                                    }
+                                    None => nih_debug_assert_failure!(
+                                        "Unhandled note expression type: {}",
+                                        event.type_id
+                                    ),
+                                }
                             }
 
                             // TODO: Add note event controllers to support the same expression types