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/string.go

@@ -0,0 +1,94 @@
+package tracker
+
+type (
+	String struct {
+		StringData
+	}
+
+	StringData interface {
+		Value() string
+		setValue(string)
+		change(kind string) func()
+	}
+
+	FilePath          Model
+	InstrumentName    Model
+	InstrumentComment Model
+	UnitSearch        Model
+)
+
+func (v String) Set(value string) {
+	if v.Value() != value {
+		defer v.change("Set")()
+		v.setValue(value)
+	}
+}
+
+// Model methods
+
+func (m *Model) FilePath() *FilePath                   { return (*FilePath)(m) }
+func (m *Model) InstrumentName() *InstrumentName       { return (*InstrumentName)(m) }
+func (m *Model) InstrumentComment() *InstrumentComment { return (*InstrumentComment)(m) }
+func (m *Model) UnitSearch() *UnitSearch               { return (*UnitSearch)(m) }
+
+// FilePathString
+
+func (v *FilePath) String() String            { return String{v} }
+func (v *FilePath) Value() string             { return v.d.FilePath }
+func (v *FilePath) setValue(value string)     { v.d.FilePath = value }
+func (v *FilePath) change(kind string) func() { return func() {} }
+
+// UnitSearchString
+
+func (v *UnitSearch) String() String            { return String{v} }
+func (v *UnitSearch) Value() string             { return v.d.UnitSearchString }
+func (v *UnitSearch) setValue(value string)     { v.d.UnitSearchString = value }
+func (v *UnitSearch) change(kind string) func() { return func() {} }
+
+// InstrumentNameString
+
+func (v *InstrumentName) String() String {
+	return String{v}
+}
+
+func (v *InstrumentName) Value() string {
+	if v.d.InstrIndex < 0 || v.d.InstrIndex >= len(v.d.Song.Patch) {
+		return ""
+	}
+	return v.d.Song.Patch[v.d.InstrIndex].Name
+}
+
+func (v *InstrumentName) setValue(value string) {
+	if v.d.InstrIndex < 0 || v.d.InstrIndex >= len(v.d.Song.Patch) {
+		return
+	}
+	v.d.Song.Patch[v.d.InstrIndex].Name = value
+}
+
+func (v *InstrumentName) change(kind string) func() {
+	return (*Model)(v).change("InstrumentNameString."+kind, PatchChange, MinorChange)
+}
+
+// InstrumentComment
+
+func (v *InstrumentComment) String() String {
+	return String{v}
+}
+
+func (v *InstrumentComment) Value() string {
+	if v.d.InstrIndex < 0 || v.d.InstrIndex >= len(v.d.Song.Patch) {
+		return ""
+	}
+	return v.d.Song.Patch[v.d.InstrIndex].Comment
+}
+
+func (v *InstrumentComment) setValue(value string) {
+	if v.d.InstrIndex < 0 || v.d.InstrIndex >= len(v.d.Song.Patch) {
+		return
+	}
+	v.d.Song.Patch[v.d.InstrIndex].Comment = value
+}
+
+func (v *InstrumentComment) change(kind string) func() {
+	return (*Model)(v).change("InstrumentComment."+kind, PatchChange, MinorChange)
+}