Actually make arpeggios work

tracker/agb-tracker/src/lib.rs

@@ -31,6 +31,7 @@ pub struct Tracker {
 
     frame: Num<u16, 8>,
     tick: u16,
+    first: bool,
 
     current_row: usize,
     current_pattern: usize,
@@ -38,18 +39,23 @@ pub struct Tracker {
 
 struct TrackerChannel {
     channel_id: Option<ChannelId>,
+    base_speed: Num<u32, 8>,
 }
 
 impl Tracker {
     pub fn new(track: &'static Track<'static>) -> Self {
         let mut channels = Vec::new();
-        channels.resize_with(track.num_channels, || TrackerChannel { channel_id: None });
+        channels.resize_with(track.num_channels, || TrackerChannel {
+            channel_id: None,
+            base_speed: 0.into(),
+        });
 
         Self {
             track,
             channels,
 
             frame: 0.into(),
+            first: true,
             tick: 0,
 
             current_row: 0,
@@ -58,9 +64,8 @@ impl Tracker {
     }
 
     pub fn step(&mut self, mixer: &mut Mixer) {
-        if self.tick != 0 {
-            self.increment_step();
-            return; // TODO: volume / pitch slides
+        if !self.increment_frame() {
+            return;
         }
 
         let pattern_to_play = self.track.patterns_to_play[self.current_pattern];
@@ -72,7 +77,7 @@ impl Tracker {
             &self.track.pattern_data[pattern_data_pos..pattern_data_pos + self.track.num_channels];
 
         for (channel, pattern_slot) in self.channels.iter_mut().zip(pattern_slots) {
-            if pattern_slot.sample != 0 {
+            if pattern_slot.sample != 0 && self.tick == 0 {
                 let sample = &self.track.samples[pattern_slot.sample - 1];
                 channel.play_sound(mixer, sample);
             }
@@ -84,13 +89,17 @@ impl Tracker {
         self.increment_step();
     }
 
-    fn increment_step(&mut self) {
+    fn increment_frame(&mut self) -> bool {
+        if self.first {
+            self.first = false;
+            return true;
+        }
+
         self.frame += 1;
 
         if self.frame >= self.track.frames_per_tick {
             self.tick += 1;
             self.frame -= self.track.frames_per_tick;
-        }
 
             if self.tick == self.track.ticks_per_step {
                 self.current_row += 1;
@@ -108,7 +117,14 @@ impl Tracker {
 
                 self.tick = 0;
             }
+
+            true
+        } else {
+            false
         }
+    }
+
+    fn increment_step(&mut self) {}
 }
 
 impl TrackerChannel {
@@ -143,6 +159,7 @@ impl TrackerChannel {
         {
             if speed != 0.into() {
                 channel.playback(speed);
+                self.base_speed = speed;
             }
 
             match effect {
@@ -150,7 +167,17 @@ impl TrackerChannel {
                 PatternEffect::Stop => {
                     channel.stop();
                 }
-                PatternEffect::Arpeggio(_, _) => todo!(),
+                PatternEffect::Arpeggio(first, second) => {
+                    let first: Num<u32, 8> = first.change_base();
+                    let second: Num<u32, 8> = second.change_base();
+
+                    match tick % 3 {
+                        0 => channel.playback(self.base_speed),
+                        1 => channel.playback(self.base_speed + first),
+                        2 => channel.playback(self.base_speed + second),
+                        _ => unreachable!(),
+                    };
+                }
                 PatternEffect::Panning(panning) => {
                     channel.panning(*panning);
                 }

tracker/agb-xm-core/src/lib.rs

@@ -104,7 +104,11 @@ pub fn parse_module(module: &Module) -> TokenStream {
         let start_pos = pattern_data.len();
 
         for row in pattern.iter() {
-            for slot in row {
+            let mut notes = vec![None; module.get_num_channels()];
+
+            for (i, slot) in row.iter().enumerate() {
+                let channel_number = i % module.get_num_channels();
+
                 let sample = if slot.instrument == 0 {
                     0
                 } else {
@@ -133,7 +137,54 @@ pub fn parse_module(module: &Module) -> TokenStream {
                     _ => PatternEffect::None,
                 };
 
+                if matches!(slot.note, Note::KeyOff) {
+                    effect1 = PatternEffect::Stop;
+                    notes[channel_number] = None;
+                } else {
+                    notes[channel_number] = Some(slot.note);
+                }
+
                 let effect2 = match slot.effect_type {
+                    0x0 => {
+                        if slot.effect_parameter == 0 {
+                            PatternEffect::None
+                        } else if let Some(note) = notes[channel_number] {
+                            let first_arpeggio = slot.effect_parameter >> 4;
+                            let second_arpeggio = slot.effect_parameter & 0xF;
+
+                            let note_speed = note_to_speed(note, 0.0, 0, module.frequency_type);
+
+                            let note = note as u8;
+                            let first_arpeggio: Note = (note + first_arpeggio)
+                                .try_into()
+                                .expect("Note out of bounds");
+                            let second_arpeggio: Note = (note + second_arpeggio)
+                                .try_into()
+                                .expect("Note out of bounds");
+
+                            let first_arpeggio_speed =
+                                note_to_speed(first_arpeggio, 0.0, 0, module.frequency_type);
+                            let second_arpeggio_speed =
+                                note_to_speed(second_arpeggio, 0.0, 0, module.frequency_type);
+
+                            let first_arpeggio_difference = first_arpeggio_speed - note_speed;
+                            let second_arpeggio_difference = second_arpeggio_speed - note_speed;
+
+                            let first_arpeggio_difference = first_arpeggio_difference
+                                .try_change_base()
+                                .expect("Arpeggio difference too large");
+                            let second_arpeggio_difference = second_arpeggio_difference
+                                .try_change_base()
+                                .expect("Arpeggio difference too large");
+
+                            PatternEffect::Arpeggio(
+                                first_arpeggio_difference,
+                                second_arpeggio_difference,
+                            )
+                        } else {
+                            PatternEffect::None
+                        }
+                    }
                     0x8 => {
                         PatternEffect::Panning(Num::new(slot.effect_parameter as i16 - 128) / 128)
                     }
@@ -141,10 +192,6 @@ pub fn parse_module(module: &Module) -> TokenStream {
                     _ => PatternEffect::None,
                 };
 
-                if matches!(slot.note, Note::KeyOff) {
-                    effect1 = PatternEffect::Stop;
-                }
-
                 if sample == 0 {
                     pattern_data.push(agb_tracker_interop::PatternSlot {
                         speed: 0.into(),