feat(tracker): undo entire modelData, not just Song

The modelData is moving towards clear meaning: it's the part of the
GUI state that is undone and also recovered from disk. This changes
the recovery data so that the undo and redo stacks are not undone,
but that is unlikely a good idea anyway, as it grows the recovery
data into unreasonable sizes.

This has also the nice benefit of undoing the cursor position, which
closes #64.

tracker/model.go

@@ -46,15 +46,16 @@ type (
 		InstrEnlarged        bool
 		RecoveryFilePath     string
 		ChangedSinceRecovery bool
-
-		PrevUndoType    string
-		UndoSkipCounter int
-		UndoStack       []sointu.Song
-		RedoStack       []sointu.Song
 	}
 
 	Model struct {
-		d              modelData
+		d modelData
+
+		prevUndoType    string
+		undoSkipCounter int
+		undoStack       []modelData
+		redoStack       []modelData
+
 		PlayerMessages <-chan PlayerMessage
 		modelMessages  chan<- interface{}
 	}
@@ -223,13 +224,15 @@ func (m *Model) SetSong(song sointu.Song) {
 	m.setSongNoUndo(song)
 }
 
+// Returns the current octave for jamming and inputting nodes
+func (m *Model) Octave() int {
+	return m.d.Octave
+}
+
+// Sets the current octave for jamming and inputting nodes and returns true if
+// it changed. The value is clamped to 0..9
 func (m *Model) SetOctave(value int) bool {
-	if value < 0 {
-		value = 0
-	}
-	if value > 9 {
-		value = 9
-	}
+	value = clamp(value, 0, 9)
 	if m.d.Octave == value {
 		return false
 	}
@@ -1025,40 +1028,42 @@ func (m *Model) Undo() {
 	if !m.CanUndo() {
 		return
 	}
-	m.d.RedoStack = append(m.d.RedoStack, m.d.Song.Copy())
-	m.setSongNoUndo(m.d.UndoStack[len(m.d.UndoStack)-1])
-	m.d.UndoStack = m.d.UndoStack[:len(m.d.UndoStack)-1]
+	m.redoStack = append(m.redoStack, m.d.Copy())
+	m.d = m.undoStack[len(m.undoStack)-1]
+	m.undoStack = m.undoStack[:len(m.undoStack)-1]
 	m.limitUndoRedoLengths()
-	m.d.PrevUndoType = ""
+	m.prevUndoType = ""
+	m.send(m.d.Song.Copy())
 }
 
 func (m *Model) CanUndo() bool {
-	return len(m.d.UndoStack) > 0
+	return len(m.undoStack) > 0
 }
 
 func (m *Model) ClearUndoHistory() {
-	if len(m.d.UndoStack) > 0 {
-		m.d.UndoStack = m.d.UndoStack[:0]
+	if len(m.undoStack) > 0 {
+		m.undoStack = m.undoStack[:0]
 	}
-	if len(m.d.RedoStack) > 0 {
-		m.d.RedoStack = m.d.RedoStack[:0]
+	if len(m.redoStack) > 0 {
+		m.redoStack = m.redoStack[:0]
 	}
-	m.d.PrevUndoType = ""
+	m.prevUndoType = ""
 }
 
 func (m *Model) Redo() {
 	if !m.CanRedo() {
 		return
 	}
-	m.d.UndoStack = append(m.d.UndoStack, m.d.Song.Copy())
-	m.setSongNoUndo(m.d.RedoStack[len(m.d.RedoStack)-1])
-	m.d.RedoStack = m.d.RedoStack[:len(m.d.RedoStack)-1]
+	m.undoStack = append(m.undoStack, m.d.Copy())
+	m.d = m.redoStack[len(m.redoStack)-1]
+	m.redoStack = m.redoStack[:len(m.redoStack)-1]
 	m.limitUndoRedoLengths()
-	m.d.PrevUndoType = ""
+	m.prevUndoType = ""
+	m.send(m.d.Song.Copy())
 }
 
 func (m *Model) CanRedo() bool {
-	return len(m.d.RedoStack) > 0
+	return len(m.redoStack) > 0
 }
 
 func (m *Model) SetNoteTracking(value bool) {
@@ -1069,10 +1074,6 @@ func (m *Model) NoteTracking() bool {
 	return m.d.NoteTracking
 }
 
-func (m *Model) Octave() int {
-	return m.d.Octave
-}
-
 func (m *Model) Song() sointu.Song {
 	return m.d.Song
 }
@@ -1128,11 +1129,11 @@ func (m *Model) ParamIndex() int {
 }
 
 func (m *Model) limitUndoRedoLengths() {
-	if len(m.d.UndoStack) >= maxUndo {
-		m.d.UndoStack = m.d.UndoStack[len(m.d.UndoStack)-maxUndo:]
+	if len(m.undoStack) >= maxUndo {
+		m.undoStack = m.undoStack[len(m.undoStack)-maxUndo:]
 	}
-	if len(m.d.RedoStack) >= maxUndo {
-		m.d.RedoStack = m.d.RedoStack[len(m.d.RedoStack)-maxUndo:]
+	if len(m.redoStack) >= maxUndo {
+		m.redoStack = m.redoStack[len(m.redoStack)-maxUndo:]
 	}
 }
 
@@ -1419,14 +1420,14 @@ func (m *Model) send(message interface{}) {
 func (m *Model) saveUndo(undoType string, undoSkipping int) {
 	m.d.ChangedSinceSave = true
 	m.d.ChangedSinceRecovery = true
-	if m.d.PrevUndoType == undoType && m.d.UndoSkipCounter < undoSkipping {
-		m.d.UndoSkipCounter++
+	if m.prevUndoType == undoType && m.undoSkipCounter < undoSkipping {
+		m.undoSkipCounter++
 		return
 	}
-	m.d.PrevUndoType = undoType
-	m.d.UndoSkipCounter = 0
-	m.d.UndoStack = append(m.d.UndoStack, m.d.Song.Copy())
-	m.d.RedoStack = m.d.RedoStack[:0]
+	m.prevUndoType = undoType
+	m.undoSkipCounter = 0
+	m.undoStack = append(m.undoStack, m.d.Copy())
+	m.redoStack = m.redoStack[:0]
 	m.limitUndoRedoLengths()
 }
 
@@ -1492,6 +1493,21 @@ func NoteIDTrack(track int, note byte) NoteID {
 	return NoteID{IsInstr: false, Track: track, Note: note}
 }
 
+func (d *modelData) Copy() modelData {
+	ret := *d
+	ret.Song = d.Song.Copy()
+	ret.PatternUseCount = make([][]int, len(d.PatternUseCount))
+	for i := range ret.PatternUseCount {
+		ret.PatternUseCount[i] = make([]int, len(d.PatternUseCount[i]))
+		copy(ret.PatternUseCount[i], d.PatternUseCount[i])
+	}
+	ret.UsedIDs = make(map[int]bool)
+	for k, v := range d.UsedIDs {
+		ret.UsedIDs[k] = v
+	}
+	return ret
+}
+
 func clamp(a, min, max int) int {
 	if a < min {
 		return min