feat(tracker): add ability to loop part of song during playback

Closes #128.

tracker/gioui/keyevent.go

@@ -69,6 +69,11 @@ func (t *Tracker) KeyEvent(e key.Event, o *op.Ops) {
 				t.Model.UnitDisabled().Bool().Toggle()
 				return
 			}
+		case "L":
+			if e.Modifiers.Contain(key.ModShortcut) {
+				t.Model.LoopToggle().Bool().Toggle()
+				return
+			}
 		case "N":
 			if e.Modifiers.Contain(key.ModShortcut) {
 				t.NewSong().Do()

tracker/gioui/note_editor.go

@@ -202,9 +202,13 @@ func (te *NoteEditor) layoutTracks(gtx C, t *Tracker) D {
 		pat := j / rpp
 		row := j % rpp
 		w := pxPatMarkWidth + pxRowMarkWidth
-		paint.ColorOp{Color: rowMarkerPatternTextColor}.Add(gtx.Ops)
 		defer op.Offset(image.Pt(0, -2)).Push(gtx.Ops).Pop()
 		if row == 0 {
+			color := rowMarkerPatternTextColor
+			if l := t.Loop(); pat >= l.Start && pat < l.Start+l.Length {
+				color = loopMarkerColor
+			}
+			paint.ColorOp{Color: color}.Add(gtx.Ops)
 			widget.Label{}.Layout(gtx, t.Theme.Shaper, trackerFont, trackerFontSize, strings.ToUpper(fmt.Sprintf("%02x", pat)), op.CallOp{})
 		}
 		defer op.Offset(image.Pt(pxPatMarkWidth, 0)).Push(gtx.Ops).Pop()

tracker/gioui/order_editor.go

@@ -81,11 +81,15 @@ func (oe *OrderEditor) Layout(gtx C, t *Tracker) D {
 	}
 
 	rowTitle := func(gtx C, j int) D {
+		w := gtx.Dp(unit.Dp(30))
 		if playPos := t.PlayPosition(); t.SongPanel.PlayingBtn.Bool.Value() && j == playPos.OrderRow {
 			paint.FillShape(gtx.Ops, patternPlayColor, clip.Rect{Max: image.Pt(gtx.Constraints.Max.X, patternCellHeight)}.Op())
 		}
-		w := gtx.Dp(unit.Dp(30))
-		paint.ColorOp{Color: rowMarkerPatternTextColor}.Add(gtx.Ops)
+		color := rowMarkerPatternTextColor
+		if l := t.Loop(); j >= l.Start && j < l.Start+l.Length {
+			color = loopMarkerColor
+		}
+		paint.ColorOp{Color: color}.Add(gtx.Ops)
 		defer op.Offset(image.Pt(0, -2)).Push(gtx.Ops).Pop()
 		widget.Label{}.Layout(gtx, t.Theme.Shaper, trackerFont, trackerFontSize, strings.ToUpper(fmt.Sprintf("%02x", j)), op.CallOp{})
 		return D{Size: image.Pt(w, patternCellHeight)}

tracker/gioui/songpanel.go

@@ -26,6 +26,7 @@ type SongPanel struct {
 	RecordBtn    *BoolClickable
 	NoteTracking *BoolClickable
 	PanicBtn     *BoolClickable
+	LoopBtn      *BoolClickable
 
 	// File menu items
 	fileMenuItems  []MenuItem
@@ -50,6 +51,7 @@ func NewSongPanel(model *tracker.Model) *SongPanel {
 		Step:           NewNumberInput(model.Step().Int()),
 		SongLength:     NewNumberInput(model.SongLength().Int()),
 		PanicBtn:       NewBoolClickable(model.Panic().Bool()),
+		LoopBtn:        NewBoolClickable(model.LoopToggle().Bool()),
 		RecordBtn:      NewBoolClickable(model.IsRecording().Bool()),
 		NoteTracking:   NewBoolClickable(model.NoteTracking().Bool()),
 		PlayingBtn:     NewBoolClickable(model.Playing().Bool()),
@@ -106,6 +108,7 @@ func (t *SongPanel) layoutSongOptions(gtx C, tr *Tracker) D {
 	playBtnStyle := ToggleIcon(tr.Theme, t.PlayingBtn, icons.AVPlayArrow, icons.AVStop, "Play (F6 / Space)", "Stop (F6 / Space)")
 	recordBtnStyle := ToggleIcon(tr.Theme, t.RecordBtn, icons.AVFiberManualRecord, icons.AVFiberSmartRecord, "Record (F7)", "Stop (F7)")
 	noteTrackBtnStyle := ToggleIcon(tr.Theme, t.NoteTracking, icons.ActionSpeakerNotesOff, icons.ActionSpeakerNotes, "Follow\nOff\n(F8)", "Follow\nOn\n(F8)")
+	loopBtnStyle := ToggleIcon(tr.Theme, t.LoopBtn, icons.NavigationArrowForward, icons.AVLoop, "Loop\nOff\n(Ctrl+L)", "Loop\nOn\n(Ctrl+L)")
 
 	return layout.Flex{Axis: layout.Vertical}.Layout(gtx,
 		layout.Rigid(func(gtx C) D {
@@ -174,6 +177,7 @@ func (t *SongPanel) layoutSongOptions(gtx C, tr *Tracker) D {
 				layout.Rigid(playBtnStyle.Layout),
 				layout.Rigid(recordBtnStyle.Layout),
 				layout.Rigid(noteTrackBtnStyle.Layout),
+				layout.Rigid(loopBtnStyle.Layout),
 			)
 		}),
 		layout.Rigid(panicBtnStyle.Layout),

tracker/gioui/theme.go

@@ -44,6 +44,7 @@ var twoBeatHighlight = color.NRGBA{R: 31, G: 51, B: 53, A: 255}
 var patternPlayColor = color.NRGBA{R: 55, G: 55, B: 61, A: 255}
 var patternTextColor = primaryColor
 var patternCellColor = color.NRGBA{R: 255, G: 255, B: 255, A: 3}
+var loopMarkerColor = color.NRGBA{R: 252, G: 186, B: 3, A: 255}
 
 var instrumentHoverColor = color.NRGBA{R: 30, G: 31, B: 38, A: 255}
 var instrumentNameColor = color.NRGBA{R: 255, G: 255, B: 255, A: 255}

tracker/gioui/tracker.go

@@ -72,7 +72,7 @@ func NewTracker(model *tracker.Model) *Tracker {
 		OctaveNumberInput: NewNumberInput(model.Octave().Int()),
 		InstrumentVoices:  NewNumberInput(model.InstrumentVoices().Int()),
 
-		TopHorizontalSplit:    &Split{Ratio: -.6},
+		TopHorizontalSplit:    &Split{Ratio: -.5},
 		BottomHorizontalSplit: &Split{Ratio: -.6},
 		VerticalSplit:         &Split{Axis: layout.Vertical},