feat!: rewrote the GUI and model for better testability

The Model was getting unmaintanable mess. This is an attempt to refactor/rewrite the Model so that data of certain type is exposed in standardized way, offering certain standard manipulations for that data type, and on the GUI side, certain standard widgets to tied to that data.

This rewrite closes #72, #106 and #120.

tracker/bool.go

@@ -0,0 +1,114 @@
+package tracker
+
+type (
+	Bool struct {
+		BoolData
+	}
+
+	BoolData interface {
+		Value() bool
+		Enabled() bool
+		setValue(bool)
+	}
+
+	Panic           Model
+	IsRecording     Model
+	Playing         Model
+	InstrEnlarged   Model
+	Effect          Model
+	CommentExpanded Model
+	NoteTracking    Model
+)
+
+func (v Bool) Toggle() {
+	v.Set(!v.Value())
+}
+
+func (v Bool) Set(value bool) {
+	if v.Enabled() && v.Value() != value {
+		v.setValue(value)
+	}
+}
+
+// Model methods
+
+func (m *Model) Panic() *Panic                     { return (*Panic)(m) }
+func (m *Model) IsRecording() *IsRecording         { return (*IsRecording)(m) }
+func (m *Model) Playing() *Playing                 { return (*Playing)(m) }
+func (m *Model) InstrEnlarged() *InstrEnlarged     { return (*InstrEnlarged)(m) }
+func (m *Model) Effect() *Effect                   { return (*Effect)(m) }
+func (m *Model) CommentExpanded() *CommentExpanded { return (*CommentExpanded)(m) }
+func (m *Model) NoteTracking() *NoteTracking       { return (*NoteTracking)(m) }
+
+// Panic methods
+
+func (m *Panic) Bool() Bool  { return Bool{m} }
+func (m *Panic) Value() bool { return m.panic }
+func (m *Panic) setValue(val bool) {
+	m.panic = val
+	(*Model)(m).send(PanicMsg{val})
+}
+func (m *Panic) Enabled() bool { return true }
+
+// IsRecording methods
+
+func (m *IsRecording) Bool() Bool  { return Bool{m} }
+func (m *IsRecording) Value() bool { return (*Model)(m).recording }
+func (m *IsRecording) setValue(val bool) {
+	m.recording = val
+	m.instrEnlarged = val
+	(*Model)(m).send(RecordingMsg{val})
+}
+func (m *IsRecording) Enabled() bool { return true }
+
+// Playing methods
+
+func (m *Playing) Bool() Bool  { return Bool{m} }
+func (m *Playing) Value() bool { return m.playing }
+func (m *Playing) setValue(val bool) {
+	m.playing = val
+	if m.playing {
+		(*Model)(m).send(StartPlayMsg{m.d.Cursor.SongPos})
+	} else {
+		(*Model)(m).send(IsPlayingMsg{val})
+	}
+}
+func (m *Playing) Enabled() bool { return m.playing || !m.instrEnlarged }
+
+// InstrEnlarged methods
+
+func (m *InstrEnlarged) Bool() Bool        { return Bool{m} }
+func (m *InstrEnlarged) Value() bool       { return m.instrEnlarged }
+func (m *InstrEnlarged) setValue(val bool) { m.instrEnlarged = val }
+func (m *InstrEnlarged) Enabled() bool     { return true }
+
+// CommentExpanded methods
+
+func (m *CommentExpanded) Bool() Bool        { return Bool{m} }
+func (m *CommentExpanded) Value() bool       { return m.commentExpanded }
+func (m *CommentExpanded) setValue(val bool) { m.commentExpanded = val }
+func (m *CommentExpanded) Enabled() bool     { return true }
+
+// NoteTracking methods
+
+func (m *NoteTracking) Bool() Bool        { return Bool{m} }
+func (m *NoteTracking) Value() bool       { return m.playing && m.noteTracking }
+func (m *NoteTracking) setValue(val bool) { m.noteTracking = val }
+func (m *NoteTracking) Enabled() bool     { return m.playing }
+
+// Effect methods
+
+func (m *Effect) Bool() Bool { return Bool{m} }
+func (m *Effect) Value() bool {
+	if m.d.Cursor.Track < 0 || m.d.Cursor.Track >= len(m.d.Song.Score.Tracks) {
+		return false
+	}
+	return m.d.Song.Score.Tracks[m.d.Cursor.Track].Effect
+}
+func (m *Effect) setValue(val bool) {
+	if m.d.Cursor.Track < 0 || m.d.Cursor.Track >= len(m.d.Song.Score.Tracks) {
+		return
+	}
+	m.d.Song.Score.Tracks[m.d.Cursor.Track].Effect = val
+}
+func (m *Effect) Enabled() bool { return true }