OSC messages for column beat tracking

audio_engine/src/column.rs

@@ -118,14 +118,17 @@ impl<const ROWS: usize> Column<ROWS> {
         chunk_factory: &mut impl ChunkFactory,
         controllers: &ColumnControllers,
     ) -> Result<()> {
-        let len = self.len();
+        let old_len = self.len();
+
         if self.idle() {
             if let Some(beat_index) = timing.beat_in_buffer {
-                let idle_time = input_buffer.len() - beat_index as usize;
-                if len == 0 {
-                    self.playback_position = self.frames_per_beat - idle_time;
+                // When starting from idle, always start at beat 0 (beginning of first beat)
+                // regardless of where in the buffer the beat occurs
+                if old_len == 0 {
+                    self.playback_position = 0; // Start at beat 0 for first recording
                 } else {
-                    self.playback_position = len - idle_time;
+                    let idle_time = input_buffer.len() - beat_index as usize;
+                    self.playback_position = old_len - idle_time;
                 }
             }
         }
@@ -147,13 +150,38 @@ impl<const ROWS: usize> Column<ROWS> {
             }
         }
 
-        let len = self.len();
-        if len > 0 {
-            self.playback_position = (self.playback_position + input_buffer.len()) % self.len();
-        } else {
-            self.playback_position =
-                (self.playback_position + input_buffer.len()) % self.frames_per_beat;
+        let new_len = self.len();
+
+        if old_len == 0 && new_len > 0 {
+            let beats = new_len / self.frames_per_beat;
+            controllers.send_column_beats_changed(beats)?;
         }
+
+        // Update playback position
+        if new_len > 0 {
+            self.playback_position = (self.playback_position + input_buffer.len()) % new_len;
+        } else {
+            // During recording of first track, don't use modulo - let position grow
+            // so that beat calculation works correctly
+            self.playback_position += input_buffer.len();
+        }
+
+        // Send beat change message if a beat occurred in this buffer
+        if timing.beat_in_buffer.is_some() {
+            // Calculate which beat we're entering (after the beat that just occurred)
+            let current_beat = if new_len > 0 {
+                // When column has defined length, calculate beat within that loop
+                let column_beats = new_len / self.frames_per_beat;
+                (self.playback_position / self.frames_per_beat) % column_beats
+            } else {
+                // During recording of first track, calculate beat based on absolute position
+                // The beat that just occurred is the beat we're now in
+                self.playback_position / self.frames_per_beat
+            };
+
+            controllers.send_column_beat_changed(current_beat)?;
+        }
+
         Ok(())
     }
 }

audio_engine/src/controllers.rs

@@ -65,6 +65,18 @@ impl<'a> ColumnControllers<'a> {
             row,
         }
     }
+
+    pub fn send_column_beats_changed(&self, beats: usize) -> Result<()> {
+        self.osc.column_beats_changed(self.column, beats)
+    }
+
+    pub fn send_column_beat_changed(&self, beat: usize) -> Result<()> {
+        self.osc.column_beat_changed(self.column, beat)
+    }
+
+    pub fn column(&self) -> usize {
+        self.column
+    }
 }
 
 impl<'a> TrackControllers<'a> {

audio_engine/src/main.rs

@@ -84,10 +84,10 @@ async fn main() {
     let state = persistence_manager.state();
 
     // Calculate tempo from state and jack client
-    let tempo_bpm = (jack_client.sample_rate() as f32 * 60.0) 
-                    / state.borrow().metronome.frames_per_beat as f32;
+    let tempo_bpm =
+        (jack_client.sample_rate() as f32 * 60.0) / state.borrow().metronome.frames_per_beat as f32;
 
-    let (mut osc, osc_controller) = Osc::new(&args.socket, COLS, ROWS, tempo_bpm)
+    let (mut osc, osc_controller) = Osc::<COLS, ROWS>::new(&args.socket, tempo_bpm)
         .await
         .expect("Could not create OSC server");
 

audio_engine/src/osc_server/controller.rs

@@ -62,4 +62,22 @@ impl OscController {
             Err(_) => Err(LooperError::Osc(std::panic::Location::caller())),    // Channel closed
         }
     }
+
+    pub fn column_beats_changed(&self, column: usize, beats: usize) -> Result<()> {
+        let message = osc::Message::ColumnBeatsChanged { column, beats };
+        match self.sender.try_send(message) {
+            Ok(true) => Ok(()),
+            Ok(false) => Err(LooperError::Osc(std::panic::Location::caller())), // Channel full
+            Err(_) => Err(LooperError::Osc(std::panic::Location::caller())),    // Channel closed
+        }
+    }
+
+    pub fn column_beat_changed(&self, column: usize, beat: usize) -> Result<()> {
+        let message = osc::Message::ColumnBeatChanged { column, beat };
+        match self.sender.try_send(message) {
+            Ok(true) => Ok(()),
+            Ok(false) => Err(LooperError::Osc(std::panic::Location::caller())), // Channel full
+            Err(_) => Err(LooperError::Osc(std::panic::Location::caller())),    // Channel closed
+        }
+    }
 }

audio_engine/src/osc_server/server.rs

@@ -3,21 +3,16 @@ use futures::SinkExt;
 
 const CLIENT_BUFFER_SIZE: usize = 32;
 
-pub struct Osc {
+pub struct Osc<const COLS: usize, const ROWS: usize> {
     receiver: kanal::AsyncReceiver<osc::Message>,
     listener: osc_server::platform::PlatformListener,
     broadcaster: tokio::sync::broadcast::Sender<osc::Message>,
-    shadow_state: osc::State,
+    shadow_state: osc::State<COLS, ROWS>,
 }
 
-impl Osc {
-    /// Create new OSC server and controller with configurable matrix size and tempo
-    pub async fn new(
-        socket_path: &str,
-        columns: usize,
-        rows: usize,
-        tempo: f32,
-    ) -> Result<(Self, OscController)> {
+impl<const COLS: usize, const ROWS: usize> Osc<COLS, ROWS> {
+    /// Create new OSC server and controller with configurable tempo
+    pub async fn new(socket_path: &str, tempo: f32) -> Result<(Self, OscController)> {
         // Create platform listener (server)
         let listener = osc_server::platform::create_listener(socket_path).await?;
 
@@ -32,7 +27,7 @@ impl Osc {
             receiver,
             listener,
             broadcaster,
-            shadow_state: osc::State::new(columns, rows, tempo),
+            shadow_state: osc::State::new(tempo),
         };
 
         Ok((server, controller))

audio_engine/src/process_handler.rs

@@ -150,7 +150,9 @@ impl<F: ChunkFactory, const COLS: usize, const ROWS: usize> ProcessHandler<F, CO
     }
 }
 
-impl<F: ChunkFactory, const COLS: usize, const ROWS: usize> jack::ProcessHandler for ProcessHandler<F, COLS, ROWS> {
+impl<F: ChunkFactory, const COLS: usize, const ROWS: usize> jack::ProcessHandler
+    for ProcessHandler<F, COLS, ROWS>
+{
     fn process(&mut self, _client: &jack::Client, ps: &jack::ProcessScope) -> jack::Control {
         if let Err(e) = self.process_with_error_handling(ps) {
             log::error!("Error processing audio: {}", e);

gui/src/interpolation.rs

@@ -26,7 +26,11 @@ impl Interpolation {
     }
 
     /// Update interpolation with current state  and return interpolated values
-    pub fn update(&mut self, state: &osc::State, current_time: Instant) -> Interpolated {
+    pub fn update<const COLS: usize, const ROWS: usize>(
+        &mut self,
+        state: &osc::State<COLS, ROWS>,
+        current_time: Instant,
+    ) -> Interpolated {
         // The OSC state is the source of truth for the base position and tempo.
         let base_position = state.metronome_position;
         let base_timestamp = state.metronome_timestamp;
@@ -82,7 +86,7 @@ mod interpolation_without_state_update_tests {
         let mut interpolation = Interpolation::new(start_time);
 
         // Create initial state with 120 BPM
-        let mut state = osc::State::new(5, 5, 120.0);
+        let mut state = osc::State::<5, 5>::new(120.0);
         state.metronome_position = 0.2;
         state.metronome_timestamp = start_time;
 
@@ -111,7 +115,7 @@ mod interpolation_without_state_update_tests {
         let mut interpolation = Interpolation::new(start_time);
 
         // Create initial state with 120 BPM
-        let mut state = osc::State::new(5, 5, 120.0);
+        let mut state = osc::State::<5, 5>::new(120.0);
         state.metronome_position = 0.2;
         state.metronome_timestamp = start_time;
 
@@ -146,7 +150,7 @@ mod interpolation_without_state_update_tests {
         let mut interpolation = Interpolation::new(start_time);
 
         // Create initial state with 120 BPM
-        let mut state = osc::State::new(5, 5, 120.0);
+        let mut state = osc::State::<5, 5>::new(120.0);
         state.metronome_position = 0.2;
         state.metronome_timestamp = start_time;
 
@@ -177,7 +181,7 @@ mod interpolation_without_state_update_tests {
         let mut interpolation = Interpolation::new(start_time);
 
         // Create initial state with 120 BPM, starting near end of beat
-        let mut state = osc::State::new(5, 5, 120.0);
+        let mut state = osc::State::<5, 5>::new(120.0);
         state.metronome_position = 0.8;
         state.metronome_timestamp = start_time;
 
@@ -205,7 +209,7 @@ mod interpolation_without_state_update_tests {
         let mut interpolation = Interpolation::new(start_time);
 
         // Create initial state with 120 BPM, starting near end of beat
-        let mut state = osc::State::new(5, 5, 120.0);
+        let mut state = osc::State::<5, 5>::new(120.0);
         state.metronome_position = 0.8;
         state.metronome_timestamp = start_time;
 
@@ -227,7 +231,7 @@ mod interpolation_without_state_update_tests {
         let result3 = interpolation.update(&state, slightly_later_time);
 
         assert!(!result3.beat_boundary); // Boundary already detected, don't fire again
-        // Position should advance only slightly: 1ms / 500ms = 0.002
+                                         // Position should advance only slightly: 1ms / 500ms = 0.002
         let expected_position_3 = 0.1 + 0.002;
         assert!((result3.position_in_beat - expected_position_3).abs() < 0.001);
     }
@@ -238,7 +242,7 @@ mod interpolation_without_state_update_tests {
         let mut interpolation = Interpolation::new(start_time);
 
         // Create initial state with 120 BPM, starting near end of beat
-        let mut state = osc::State::new(5, 5, 120.0);
+        let mut state = osc::State::<5, 5>::new(120.0);
         state.metronome_position = 0.8;
         state.metronome_timestamp = start_time;
 
@@ -259,7 +263,8 @@ mod interpolation_without_state_update_tests {
         let result3 = interpolation.update(&state, later_time);
 
         assert!(!result3.beat_boundary); // Boundary already detected, don't fire again
-        assert!((result3.position_in_beat - result2.position_in_beat).abs() < 0.001); // Same position
+        assert!((result3.position_in_beat - result2.position_in_beat).abs() < 0.001);
+        // Same position
     }
 }
 
@@ -274,7 +279,7 @@ mod state_update_tests {
         let mut interpolation = Interpolation::new(start_time);
 
         // Create initial state with 120 BPM
-        let mut state = osc::State::new(5, 5, 120.0);
+        let mut state = osc::State::<5, 5>::new(120.0);
         state.metronome_position = 0.2;
         state.metronome_timestamp = start_time;
 
@@ -321,7 +326,7 @@ mod state_update_tests {
         let mut interpolation = Interpolation::new(start_time);
 
         // Create initial state with 120 BPM
-        let mut state = osc::State::new(5, 5, 120.0);
+        let mut state = osc::State::<5, 5>::new(120.0);
         state.metronome_position = 0.3;
         state.metronome_timestamp = start_time;
 
@@ -367,7 +372,7 @@ mod state_update_tests {
         let mut interpolation = Interpolation::new(start_time);
 
         // Create initial state with 120 BPM, starting near end of beat
-        let mut state = osc::State::new(5, 5, 120.0);
+        let mut state = osc::State::<5, 5>::new(120.0);
         state.metronome_position = 0.9;
         state.metronome_timestamp = start_time;
 
@@ -410,7 +415,7 @@ mod state_update_tests {
         let mut interpolation = Interpolation::new(start_time);
 
         // Create initial state with 120 BPM, starting near end of beat
-        let mut state = osc::State::new(5, 5, 120.0);
+        let mut state = osc::State::<5, 5>::new(120.0);
         state.metronome_position = 0.85;
         state.metronome_timestamp = start_time;
 
@@ -453,7 +458,7 @@ mod state_update_tests {
         let mut interpolation = Interpolation::new(start_time);
 
         // Create initial state with 120 BPM, starting near end of beat
-        let mut state = osc::State::new(5, 5, 120.0);
+        let mut state = osc::State::<5, 5>::new(120.0);
         state.metronome_position = 0.92;
         state.metronome_timestamp = start_time;
 
@@ -488,7 +493,11 @@ mod state_update_tests {
         // Should show current position: OSC 0.98 at 80ms + 20ms interpolation
         // 20ms = 0.02 seconds = 0.02 / 0.5 = 0.04 beat progress
         let expected_position = 0.98 + 0.04; // = 1.02 → wraps to 0.02
-        let wrapped_position = if expected_position >= 1.0 { expected_position - 1.0 } else { expected_position };
+        let wrapped_position = if expected_position >= 1.0 {
+            expected_position - 1.0
+        } else {
+            expected_position
+        };
         assert!((result3.position_in_beat - wrapped_position).abs() < 0.001);
     }
 
@@ -498,7 +507,7 @@ mod state_update_tests {
         let mut interpolation = Interpolation::new(start_time);
 
         // Create initial state with 120 BPM
-        let mut state = osc::State::new(5, 5, 120.0);
+        let mut state = osc::State::<5, 5>::new(120.0);
         state.metronome_position = 0.2;
         state.metronome_timestamp = start_time;
 
@@ -549,7 +558,7 @@ mod state_update_tests {
         let mut interpolation = Interpolation::new(start_time);
 
         // Create initial state with 120 BPM
-        let mut state = osc::State::new(5, 5, 120.0);
+        let mut state = osc::State::<5, 5>::new(120.0);
         state.metronome_position = 0.2;
         state.metronome_timestamp = start_time;
 
@@ -595,7 +604,7 @@ mod state_update_tests {
         let mut interpolation = Interpolation::new(start_time);
 
         // Create initial state with 120 BPM, starting near end of beat
-        let mut state = osc::State::new(5, 5, 120.0);
+        let mut state = osc::State::<5, 5>::new(120.0);
         state.metronome_position = 0.8;
         state.metronome_timestamp = start_time;
 
@@ -644,7 +653,7 @@ mod state_update_tests {
         let mut interpolation = Interpolation::new(start_time);
 
         // Create initial state with 120 BPM, starting near end of beat
-        let mut state = osc::State::new(5, 5, 120.0);
+        let mut state = osc::State::<5, 5>::new(120.0);
         state.metronome_position = 0.85;
         state.metronome_timestamp = start_time;
 
@@ -701,7 +710,7 @@ mod state_update_tests {
         let mut interpolation = Interpolation::new(start_time);
 
         // Create initial state with 120 BPM, starting near end of beat
-        let mut state = osc::State::new(5, 5, 120.0);
+        let mut state = osc::State::<5, 5>::new(120.0);
         state.metronome_position = 0.9;
         state.metronome_timestamp = start_time;
 

gui/src/main.rs

@@ -6,6 +6,9 @@ mod ui;
 use anyhow::anyhow;
 use anyhow::Result;
 
+const COLUMNS: usize = 5;
+const ROWS: usize = 5;
+
 trait DisplayStr {
     fn display_str(&self) -> &'static str;
 }
@@ -25,18 +28,17 @@ impl DisplayStr for osc::TrackState {
 async fn main() -> Result<()> {
     // Configuration
     let socket_path = "fcb_looper.sock";
-    let columns = 5;
-    let rows = 5;
 
     // Logger
     simple_logger::SimpleLogger::new()
         .with_level(log::LevelFilter::Info)
         .with_module_level("gui::osc_client", log::LevelFilter::Off)
+        .with_module_level("osc", log::LevelFilter::Debug)
         .init()
         .expect("Could not initialize logger");
 
     // Create OSC client
-    let osc_client = osc_client::Client::new(socket_path, columns, rows)?;
+    let osc_client = osc_client::Client::<COLUMNS, ROWS>::new(socket_path)?;
     let state_receiver = osc_client.state_receiver();
 
     // Spawn OSC receiver thread on tokio runtime
@@ -58,7 +60,7 @@ async fn main() -> Result<()> {
     eframe::run_native(
         "FCB Looper",
         options,
-        Box::new(|_cc| Ok(Box::new(ui::App::new(state_receiver)))),
+        Box::new(|_cc| Ok(Box::new(ui::App::<COLUMNS, ROWS>::new(state_receiver)))),
     )
     .map_err(|e| anyhow::anyhow!("Failed to run egui: {}", e))?;
 

gui/src/osc_client.rs

@@ -15,32 +15,33 @@ type PlatformStream = UnixStream;
 #[cfg(windows)]
 type PlatformStream = NamedPipeClient;
 
-pub struct Client {
+pub struct Client<const COLS: usize, const ROWS: usize> {
     socket_path: String,
-    state_sender: watch::Sender<osc::State>,
-    state_receiver: watch::Receiver<osc::State>,
+    state_sender: watch::Sender<osc::State<COLS, ROWS>>,
+    state_receiver: watch::Receiver<osc::State<COLS, ROWS>>,
 }
 
-impl Client {
-    pub fn new(socket_path: &str, columns: usize, rows: usize) -> Result<Self> {
-        let initial_state = osc::State::new(columns, rows, 120.0);
+impl<const COLS: usize, const ROWS: usize> Client<COLS, ROWS> {
+    pub fn new(socket_path: &str) -> Result<Self> {
+        let initial_state = osc::State::new(120.0);
         // Test data
         let initial_state = {
             let mut initial_state = initial_state;
-            initial_state.selected_column = 2;
-            initial_state.selected_row = 3;
-            initial_state.cells[0][0].state = osc::TrackState::Playing;
-            initial_state.cells[0][0].volume = 0.3;
-            initial_state.cells[0][1].state = osc::TrackState::Idle;
-            initial_state.cells[0][1].volume = 1.0;
-            initial_state.cells[1][0].state = osc::TrackState::Idle;
-            initial_state.cells[1][0].volume = 0.9;
-            initial_state.cells[1][1].state = osc::TrackState::Playing;
-            initial_state.cells[1][1].volume = 0.8;
-            initial_state.cells[2][0].state = osc::TrackState::Idle;
-            initial_state.cells[2][0].volume = 0.7;
-            initial_state.cells[2][3].state = osc::TrackState::Recording;
-            initial_state.cells[2][3].volume = 0.6;
+            initial_state.selected_column = if COLS > 2 { 2 } else { 0 };
+            initial_state.selected_row = if ROWS > 3 { 3 } else { 0 };
+
+            initial_state.columns[0].tracks[0].state = osc::TrackState::Playing;
+            initial_state.columns[0].tracks[0].volume = 0.3;
+            initial_state.columns[0].tracks[1].state = osc::TrackState::Idle;
+            initial_state.columns[0].tracks[1].volume = 1.0;
+            initial_state.columns[1].tracks[0].state = osc::TrackState::Idle;
+            initial_state.columns[1].tracks[0].volume = 0.9;
+            initial_state.columns[1].tracks[1].state = osc::TrackState::Playing;
+            initial_state.columns[1].tracks[1].volume = 0.8;
+            initial_state.columns[2].tracks[0].state = osc::TrackState::Idle;
+            initial_state.columns[2].tracks[0].volume = 0.7;
+            initial_state.columns[2].tracks[3].state = osc::TrackState::Recording;
+            initial_state.columns[2].tracks[3].volume = 0.6;
 
             initial_state
         };
@@ -53,7 +54,7 @@ impl Client {
         })
     }
 
-    pub fn state_receiver(&self) -> watch::Receiver<osc::State> {
+    pub fn state_receiver(&self) -> watch::Receiver<osc::State<COLS, ROWS>> {
         self.state_receiver.clone()
     }
 
@@ -86,12 +87,16 @@ impl Client {
         Ok(())
     }
 
-    async fn handle_osc_data(&self, data: Bytes, current_state: &mut osc::State) -> Result<()> {
+    async fn handle_osc_data(
+        &self,
+        data: Bytes,
+        current_state: &mut osc::State<COLS, ROWS>,
+    ) -> Result<()> {
         let (_, osc_packet) = rosc::decoder::decode_udp(&data)
             .map_err(|e| anyhow!("Failed to decode OSC packet: {}", e))?;
 
         if let Some(update) = osc::Message::from_osc_packet(osc_packet)? {
-            update.apply_to_state(current_state);
+            current_state.update(&update);
 
             // Send updated state through watch channel
             if let Err(_) = self.state_sender.send(current_state.clone()) {

gui/src/ui/app.rs

@@ -1,11 +1,11 @@
-pub struct App {
-    state_receiver: tokio::sync::watch::Receiver<osc::State>,
+pub struct App<const COLS: usize, const ROWS: usize> {
+    state_receiver: tokio::sync::watch::Receiver<osc::State<COLS, ROWS>>,
     interpolation: crate::interpolation::Interpolation,
     pendulum: crate::pendulum::Pendulum,
 }
 
-impl App {
-    pub fn new(state_receiver: tokio::sync::watch::Receiver<osc::State>) -> Self {
+impl<const COLS: usize, const ROWS: usize> App<COLS, ROWS> {
+    pub fn new(state_receiver: tokio::sync::watch::Receiver<osc::State<COLS, ROWS>>) -> Self {
         let interpolation = crate::interpolation::Interpolation::new(std::time::Instant::now());
         let pendulum = crate::pendulum::Pendulum::new();
         Self {
@@ -16,7 +16,7 @@ impl App {
     }
 }
 
-impl eframe::App for App {
+impl<const COLS: usize, const ROWS: usize> eframe::App for App<COLS, ROWS> {
     fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
         let state = self.state_receiver.borrow_and_update().clone();
         let interpolated = self.interpolation.update(&state, std::time::Instant::now());
@@ -31,8 +31,8 @@ impl eframe::App for App {
         egui::CentralPanel::default().show(ctx, |ui| {
             ui.vertical(|ui| {
                 ui.add(super::Metronome::new(pendulum_position));
-                ui.add(super::Matrix::new(
-                    &state.cells,
+                ui.add(super::Matrix::<COLS, ROWS>::new(
+                    &state.columns,
                     state.selected_column,
                     state.selected_row,
                 ));

gui/src/ui/column.rs

@@ -1,22 +1,23 @@
 use super::ui_rows_ext::UiRowsExt;
-pub struct Column<'a> {
-    state: &'a Vec<osc::Track>,
+
+pub struct Column<'a, const ROWS: usize> {
+    tracks: &'a [osc::Track; ROWS],
     selected_row: Option<usize>,
 }
 
-impl<'a> Column<'a> {
-    pub fn new(state: &'a Vec<osc::Track>, selected_row: Option<usize>) -> Self {
+impl<'a, const ROWS: usize> Column<'a, ROWS> {
+    pub fn new(tracks: &'a [osc::Track; ROWS], selected_row: Option<usize>) -> Self {
         Self {
-            state,
+            tracks,
             selected_row,
         }
     }
 }
 
-impl<'a> egui::Widget for Column<'a> {
+impl<'a, const ROWS: usize> egui::Widget for Column<'a, ROWS> {
     fn ui(self, ui: &mut egui::Ui) -> egui::Response {
-        ui.rows(self.state.len(), |ui| {
-            for (i, track) in self.state.iter().enumerate() {
+        ui.rows(self.tracks.len(), |ui| {
+            for (i, track) in self.tracks.iter().enumerate() {
                 ui[i].add(super::Track::new(track, Some(i) == self.selected_row));
             }
         });

gui/src/ui/matrix.rs

@@ -1,33 +1,33 @@
-pub struct Matrix<'a> {
-    cells: &'a Vec<Vec<osc::Track>>,
+pub struct Matrix<'a, const COLS: usize, const ROWS: usize> {
+    columns: &'a [osc::Column<ROWS>; COLS],
     selected_column: usize,
     selected_row: usize,
 }
 
-impl<'a> Matrix<'a> {
+impl<'a, const COLS: usize, const ROWS: usize> Matrix<'a, COLS, ROWS> {
     pub fn new(
-        cells: &'a Vec<Vec<osc::Track>>,
+        columns: &'a [osc::Column<ROWS>; COLS],
         selected_column: usize,
         selected_row: usize,
     ) -> Self {
         Self {
-            cells,
+            columns,
             selected_column,
             selected_row,
         }
     }
 }
 
-impl<'a> egui::Widget for Matrix<'a> {
+impl<'a, const COLS: usize, const ROWS: usize> egui::Widget for Matrix<'a, COLS, ROWS> {
     fn ui(self, ui: &mut egui::Ui) -> egui::Response {
-        ui.columns(self.cells.len(), |ui| {
-            for (i, column) in self.cells.iter().enumerate() {
+        ui.columns(self.columns.len(), |ui| {
+            for (i, column) in self.columns.iter().enumerate() {
                 let selected_row = if i == self.selected_column {
                     Some(self.selected_row)
                 } else {
                     None
                 };
-                ui[i].add(super::Column::new(column, selected_row));
+                ui[i].add(super::Column::new(&column.tracks, selected_row));
             }
         });
         ui.response()

osc/src/lib.rs

@@ -6,6 +6,7 @@ use error::AddressParseResult;
 pub use error::Error;
 pub use error::Result;
 pub use message::Message;
+pub use state::Column;
 pub use state::State;
 pub use state::Track;
 pub use state::TrackState;

osc/src/message.rs

@@ -24,6 +24,14 @@ pub enum Message {
     Tempo {
         bpm: f32,
     },
+    ColumnBeatsChanged {
+        column: usize,
+        beats: usize,
+    },
+    ColumnBeatChanged {
+        column: usize,
+        beat: usize,
+    },
 }
 
 impl Message {
@@ -37,7 +45,10 @@ impl Message {
         }
     }
 
-    pub fn apply_to_state(&self, state: &mut State) {
+    pub fn apply_to_state<const COLS: usize, const ROWS: usize>(
+        &self,
+        state: &mut State<COLS, ROWS>,
+    ) {
         match self {
             Message::TrackStateChanged {
                 column,
@@ -65,6 +76,12 @@ impl Message {
             Message::Tempo { bpm } => {
                 state.set_tempo(*bpm);
             }
+            Message::ColumnBeatsChanged { column, beats } => {
+                state.set_column_beats(*column, *beats);
+            }
+            Message::ColumnBeatChanged { column, beat } => {
+                state.set_column_beat(*column, *beat);
+            }
         }
     }
 
@@ -83,7 +100,7 @@ impl Message {
 
             if let Some(rosc::OscType::String(state_str)) = args.first() {
                 let state = state_str.parse::<TrackState>().unwrap_or(TrackState::Empty);
-                log::trace!("TrackStateChanged: column={column}, row={row}, state={state}");
+                log::debug!("TrackStateChanged: column={column}, row={row}, state={state}");
                 return Ok(Some(Message::TrackStateChanged { column, row, state }));
             }
         } else if addr.starts_with("/looper/cell/") && addr.ends_with("/volume") {
@@ -97,23 +114,53 @@ impl Message {
             let row: usize = parts[4].parse::<usize>().address_part_result("row")? - 1; // Convert to 0-based
 
             if let Some(rosc::OscType::Float(volume)) = args.first() {
-                log::trace!("TrackVolumeChanged: column={column}, row={row}, volume={volume}");
+                log::debug!("TrackVolumeChanged: column={column}, row={row}, volume={volume}");
                 return Ok(Some(Message::TrackVolumeChanged {
                     column,
                     row,
                     volume: *volume,
                 }));
             }
+        } else if addr.starts_with("/looper/column/") && addr.ends_with("/beats") {
+            // Parse: /looper/column/{column}/beats
+            let parts: Vec<&str> = addr.split('/').collect();
+            if parts.len() != 5 {
+                return Err(Error::AddressParseError(addr));
+            }
+
+            let column: usize = parts[3].parse::<usize>().address_part_result("column")? - 1; // Convert to 0-based
+
+            if let Some(rosc::OscType::Int(beats)) = args.first() {
+                log::debug!("ColumnBeatsChanged: column={column}, beats={beats}");
+                return Ok(Some(Message::ColumnBeatsChanged {
+                    column,
+                    beats: *beats as usize,
+                }));
+            }
+        } else if addr.starts_with("/looper/column/") && addr.ends_with("/beat") {
+            // Parse: /looper/column/{column}/beat
+            let parts: Vec<&str> = addr.split('/').collect();
+            if parts.len() != 5 {
+                return Err(Error::AddressParseError(addr));
+            }
+
+            let column: usize = parts[3].parse::<usize>().address_part_result("column")? - 1; // Convert to 0-based
+
+            if let Some(rosc::OscType::Int(beat)) = args.first() {
+                let beat = (*beat as usize).saturating_sub(1); // Convert to 0-based
+                log::debug!("ColumnBeatChanged: column={column}, beat={beat}");
+                return Ok(Some(Message::ColumnBeatChanged { column, beat }));
+            }
         } else if addr == "/looper/selected/column" {
             if let Some(rosc::OscType::Int(column_1based)) = args.first() {
-                log::trace!("SelectedColumnChanged: column={column_1based}");
                 let column = (*column_1based as usize).saturating_sub(1); // Convert to 0-based
+                log::debug!("SelectedColumnChanged: column={column}");
                 return Ok(Some(Message::SelectedColumnChanged { column }));
             }
         } else if addr == "/looper/selected/row" {
             if let Some(rosc::OscType::Int(row_1based)) = args.first() {
-                log::trace!("SelectedRowChanged: row={row_1based}");
                 let row = (*row_1based as usize).saturating_sub(1); // Convert to 0-based
+                log::debug!("SelectedRowChanged: row={row}");
                 return Ok(Some(Message::SelectedRowChanged { row }));
             }
         } else if addr == "/looper/metronome/position" {
@@ -125,7 +172,7 @@ impl Message {
             }
         } else if addr == "/looper/tempo" {
             if let Some(rosc::OscType::Float(bpm)) = args.first() {
-                log::trace!("Tempo: bpm={bpm}");
+                log::debug!("Tempo: bpm={bpm}");
                 return Ok(Some(Message::Tempo { bpm: *bpm }));
             }
         }
@@ -187,6 +234,22 @@ impl Message {
                     args: vec![rosc::OscType::Float(bpm)],
                 })
             }
+            Message::ColumnBeatsChanged { column, beats } => {
+                let address = format!("/looper/column/{}/beats", column + 1); // 1-based indexing
+
+                rosc::OscPacket::Message(rosc::OscMessage {
+                    addr: address,
+                    args: vec![rosc::OscType::Int(beats as i32)],
+                })
+            }
+            Message::ColumnBeatChanged { column, beat } => {
+                let address = format!("/looper/column/{}/beat", column + 1); // 1-based indexing
+
+                rosc::OscPacket::Message(rosc::OscMessage {
+                    addr: address,
+                    args: vec![rosc::OscType::Int((beat + 1) as i32)], // Convert to 1-based
+                })
+            }
         }
     }
 }

osc/src/state.rs

@@ -15,37 +15,41 @@ pub struct Track {
 }
 
 #[derive(Debug, Clone)]
-pub struct State {
-    pub selected_column: usize, // 0-based (converted to 1-based for OSC)
-    pub selected_row: usize,    // 0-based (converted to 1-based for OSC)
-    pub cells: Vec<Vec<Track>>,
-    pub columns: usize,
-    pub rows: usize,
-    pub metronome_position: f32, // 0.0 - 1.0 position within current beat
-    pub metronome_timestamp: std::time::Instant, // When position was last updated
-    pub tempo: f32, // BPM
+pub struct Column<const ROWS: usize> {
+    pub tracks: [Track; ROWS],
+    pub beat_count: usize,   // total beats in column (0 = no beats set)
+    pub current_beat: usize, // current beat position (0-based internally)
 }
 
-impl State {
-    pub fn new(columns: usize, rows: usize, tempo: f32) -> Self {
-        let cells = (0..columns)
-            .map(|_| {
-                vec![
-                    Track {
-                        state: TrackState::Empty,
-                        volume: 1.0
-                    };
-                    rows
-                ]
-            })
-            .collect();
+#[derive(Debug, Clone)]
+pub struct State<const COLS: usize, const ROWS: usize> {
+    pub selected_column: usize, // 0-based (converted to 1-based for OSC)
+    pub selected_row: usize,    // 0-based (converted to 1-based for OSC)
+    pub columns: [Column<ROWS>; COLS],
+    pub metronome_position: f32, // 0.0 - 1.0 position within current beat
+    pub metronome_timestamp: std::time::Instant, // When position was last updated
+    pub tempo: f32,              // BPM
+}
 
+impl<const ROWS: usize> Column<ROWS> {
+    pub fn new() -> Self {
+        Self {
+            tracks: std::array::from_fn(|_| Track {
+                state: TrackState::Empty,
+                volume: 1.0,
+            }),
+            beat_count: 0,
+            current_beat: 0,
+        }
+    }
+}
+
+impl<const COLS: usize, const ROWS: usize> State<COLS, ROWS> {
+    pub fn new(tempo: f32) -> Self {
         Self {
             selected_column: 0,
             selected_row: 0,
-            cells,
-            columns,
-            rows,
+            columns: std::array::from_fn(|_| Column::new()),
             metronome_position: 0.0,
             metronome_timestamp: std::time::Instant::now(),
             tempo,
@@ -55,8 +59,8 @@ impl State {
     pub fn update(&mut self, message: &Message) {
         match message {
             Message::TrackStateChanged { column, row, state } => {
-                if *column < self.columns && *row < self.rows {
-                    self.cells[*column][*row].state = state.clone();
+                if *column < COLS && *row < ROWS {
+                    self.columns[*column].tracks[*row].state = state.clone();
                 }
             }
             Message::TrackVolumeChanged {
@@ -64,17 +68,17 @@ impl State {
                 row,
                 volume,
             } => {
-                if *column < self.columns && *row < self.rows {
-                    self.cells[*column][*row].volume = *volume;
+                if *column < COLS && *row < ROWS {
+                    self.columns[*column].tracks[*row].volume = *volume;
                 }
             }
             Message::SelectedColumnChanged { column } => {
-                if *column < self.columns {
+                if *column < COLS {
                     self.selected_column = *column;
                 }
             }
             Message::SelectedRowChanged { row } => {
-                if *row < self.rows {
+                if *row < ROWS {
                     self.selected_row = *row;
                 }
             }
@@ -84,6 +88,12 @@ impl State {
             Message::Tempo { bpm } => {
                 self.set_tempo(*bpm);
             }
+            Message::ColumnBeatsChanged { column, beats } => {
+                self.set_column_beats(*column, *beats);
+            }
+            Message::ColumnBeatChanged { column, beat } => {
+                self.set_column_beat(*column, *beat);
+            }
         }
     }
 
@@ -101,9 +111,20 @@ impl State {
             row: self.selected_row,
         });
 
-        // Send all cell states and volumes
-        for (column, column_cells) in self.cells.iter().enumerate() {
-            for (row, track) in column_cells.iter().enumerate() {
+        // Send column beat information and cell states/volumes
+        for (column, column_data) in self.columns.iter().enumerate() {
+            // Send column beat info
+            messages.push(Message::ColumnBeatsChanged {
+                column,
+                beats: column_data.beat_count,
+            });
+            messages.push(Message::ColumnBeatChanged {
+                column,
+                beat: column_data.current_beat,
+            });
+
+            // Send all cell states and volumes for this column
+            for (row, track) in column_data.tracks.iter().enumerate() {
                 messages.push(Message::TrackStateChanged {
                     column,
                     row,
@@ -121,26 +142,26 @@ impl State {
     }
 
     pub fn set_track_state(&mut self, column: usize, row: usize, state: TrackState) {
-        if column < self.columns && row < self.rows {
-            self.cells[column][row].state = state;
+        if column < COLS && row < ROWS {
+            self.columns[column].tracks[row].state = state;
         }
     }
 
     pub fn set_selected_column(&mut self, column: usize) {
-        if column < self.columns {
+        if column < COLS {
             self.selected_column = column;
         }
     }
 
     pub fn set_selected_row(&mut self, row: usize) {
-        if row < self.rows {
+        if row < ROWS {
             self.selected_row = row;
         }
     }
 
     pub fn set_track_volume(&mut self, column: usize, row: usize, volume: f32) {
-        if column < self.columns && row < self.rows {
-            self.cells[column][row].volume = volume;
+        if column < COLS && row < ROWS {
+            self.columns[column].tracks[row].volume = volume;
         }
     }
 
@@ -152,4 +173,16 @@ impl State {
     pub fn set_tempo(&mut self, bpm: f32) {
         self.tempo = bpm;
     }
+
+    pub fn set_column_beats(&mut self, column: usize, beats: usize) {
+        if column < COLS {
+            self.columns[column].beat_count = beats;
+        }
+    }
+
+    pub fn set_column_beat(&mut self, column: usize, beat: usize) {
+        if column < COLS {
+            self.columns[column].current_beat = beat;
+        }
+    }
 }