feat: introduce "cache" for derived model information

tracker/table.go

@@ -1,7 +1,6 @@
 package tracker
 
 import (
-	"iter"
 	"math"
 
 	"github.com/vsariola/sointu"
@@ -367,71 +366,6 @@ func (m *Order) SetValue(p Point, val int) {
 	m.d.Song.Score.Tracks[p.X].Order.Set(p.Y, val)
 }
 
-func (e *Order) Title(x int) (title string) {
-	title = "?"
-	if x < 0 || x >= len(e.d.Song.Score.Tracks) {
-		return
-	}
-	firstIndex, lastIndex, err := e.instrumentListFor(x)
-	if err != nil {
-		return
-	}
-	switch diff := lastIndex - firstIndex; diff {
-	case 0:
-		title = e.d.Song.Patch[firstIndex].Name
-	default:
-		n1 := e.d.Song.Patch[firstIndex].Name
-		n2 := e.d.Song.Patch[firstIndex+1].Name
-		if len(n1) > 0 {
-			n1 = string(n1[0])
-		} else {
-			n1 = "?"
-		}
-		if len(n2) > 0 {
-			n2 = string(n2[0])
-		} else {
-			n2 = "?"
-		}
-		if diff > 1 {
-			title = n1 + "/" + n2 + "..."
-		} else {
-			title = n1 + "/" + n2
-		}
-	}
-	return
-}
-
-func (e *Order) instrumentListFor(trackIndex int) (int, int, error) {
-	track := e.d.Song.Score.Tracks[trackIndex]
-	firstVoice := e.d.Song.Score.FirstVoiceForTrack(trackIndex)
-	lastVoice := firstVoice + track.NumVoices - 1
-	firstIndex, err1 := e.d.Song.Patch.InstrumentForVoice(firstVoice)
-	if err1 != nil {
-		return trackIndex, trackIndex, err1
-	}
-	lastIndex, err2 := e.d.Song.Patch.InstrumentForVoice(lastVoice)
-	if err2 != nil {
-		return trackIndex, trackIndex, err2
-	}
-	return firstIndex, lastIndex, nil
-}
-
-func (e *Order) TrackIndicesForCurrentInstrument() iter.Seq[int] {
-	currentTrack := e.d.Cursor.Track
-	return e.d.Song.AllTracksWithSameInstrument(currentTrack)
-}
-
-func (e *Order) CountNextTracksForCurrentInstrument() int {
-	currentTrack := e.d.Cursor.Track
-	count := 0
-	for t := range e.TrackIndicesForCurrentInstrument() {
-		if t > currentTrack {
-			count++
-		}
-	}
-	return count
-}
-
 // NoteTable
 
 func (v *Notes) Table() Table {