feat(tracker): implement alerts that display useful notifications / errors

In particular, we show notification after the user has copied something to clipboard (#34) and when there is a patch compile error (#38).

tracker/alert.go

@@ -0,0 +1,116 @@
+package tracker
+
+import (
+	"image/color"
+	"time"
+
+	"gioui.org/f32"
+	"gioui.org/layout"
+	"gioui.org/op"
+	"gioui.org/op/clip"
+	"gioui.org/op/paint"
+	"gioui.org/unit"
+)
+
+type Alert struct {
+	message       string
+	alertType     AlertType
+	duration      time.Duration
+	showMessage   string
+	showAlertType AlertType
+	showDuration  time.Duration
+	showTime      time.Time
+	pos           float64
+	lastUpdate    time.Time
+}
+
+type AlertType int
+
+const (
+	None AlertType = iota
+	Notify
+	Warning
+	Error
+)
+
+var alertSpeed = 150 * time.Millisecond
+var alertMargin = layout.UniformInset(unit.Dp(6))
+var alertInset = layout.UniformInset(unit.Dp(6))
+
+func (a *Alert) Update(message string, alertType AlertType, duration time.Duration) {
+	if a.alertType < alertType {
+		a.message = message
+		a.alertType = alertType
+		a.duration = duration
+	}
+}
+
+func (a *Alert) Layout(gtx C) D {
+	now := time.Now()
+	if a.alertType != None {
+		a.showMessage = a.message
+		a.showAlertType = a.alertType
+		a.showTime = now
+		a.showDuration = a.duration
+	}
+	a.alertType = None
+	var targetPos float64 = 0.0
+	if now.Sub(a.showTime) <= a.showDuration {
+		targetPos = 1.0
+	}
+	delta := float64(now.Sub(a.lastUpdate)) / float64(alertSpeed)
+	if a.pos < targetPos {
+		a.pos += delta
+		if a.pos > targetPos {
+			a.pos = targetPos
+		} else {
+			op.InvalidateOp{At: now.Add(50 * time.Millisecond)}.Add(gtx.Ops)
+		}
+	} else if a.pos > targetPos {
+		a.pos -= delta
+		if a.pos < targetPos {
+			a.pos = targetPos
+		} else {
+			op.InvalidateOp{At: now.Add(50 * time.Millisecond)}.Add(gtx.Ops)
+		}
+	}
+	a.lastUpdate = now
+	var color, textColor, shadeColor color.NRGBA
+	switch a.showAlertType {
+	case Warning:
+		color = warningColor
+		textColor = black
+	case Error:
+		color = errorColor
+		textColor = black
+	default:
+		color = popupSurfaceColor
+		textColor = white
+		shadeColor = black
+	}
+	bgWidget := func(gtx C) D {
+		paint.FillShape(gtx.Ops, color, clip.Rect{
+			Max: gtx.Constraints.Min,
+		}.Op())
+		return D{Size: gtx.Constraints.Min}
+	}
+	labelStyle := LabelStyle{Text: a.showMessage, Color: textColor, ShadeColor: shadeColor, Font: labelDefaultFont, Alignment: layout.Center, FontSize: unit.Dp(16)}
+	return alertMargin.Layout(gtx, func(gtx C) D {
+		return layout.S.Layout(gtx, func(gtx C) D {
+			defer op.Save(gtx.Ops).Load()
+			gtx.Constraints.Min.X = gtx.Constraints.Max.X
+			recording := op.Record(gtx.Ops)
+			dims := layout.Stack{Alignment: layout.Center}.Layout(gtx,
+				layout.Expanded(bgWidget),
+				layout.Stacked(func(gtx C) D {
+					return alertInset.Layout(gtx, labelStyle.Layout)
+				}),
+			)
+			macro := recording.Stop()
+			totalY := dims.Size.Y + gtx.Px(alertMargin.Bottom)
+			op.Offset(f32.Pt(0, float32((1-a.pos)*float64(totalY)))).Add((gtx.Ops))
+			macro.Add(gtx.Ops)
+			return dims
+		})
+	})
+}

tracker/instruments.go

@@ -1,8 +1,10 @@
 package tracker
 
 import (
+	"fmt"
 	"image"
 	"strconv"
+	"time"
 
 	"gioui.org/io/clipboard"
 	"gioui.org/io/pointer"
@@ -104,6 +106,7 @@ func (t *Tracker) layoutInstrumentHeader(gtx C) D {
 		contents, err := yaml.Marshal(t.song.Patch.Instruments[t.CurrentInstrument])
 		if err == nil {
 			clipboard.WriteOp{Text: string(contents)}.Add(gtx.Ops)
+			t.Alert.Update("Instrument copied to clipboard", Notify, time.Second*3)
 		}
 	}
 	for t.DeleteInstrumentBtn.Clicked() {
@@ -185,19 +188,20 @@ func (t *Tracker) layoutInstrumentEditor(gtx C) D {
 	addUnitBtnStyle.Background = t.Theme.Fg
 	addUnitBtnStyle.Inset = layout.UniformInset(unit.Dp(4))
 
-	for len(t.StackUse) < len(t.song.Patch.Instruments[t.CurrentInstrument].Units) {
+	units := t.song.Patch.Instruments[t.CurrentInstrument].Units
+	for len(t.StackUse) < len(units) {
 		t.StackUse = append(t.StackUse, 0)
 	}
 
 	stackHeight := 0
-	for i, u := range t.song.Patch.Instruments[t.CurrentInstrument].Units {
+	for i, u := range units {
 		stackHeight += u.StackChange()
 		t.StackUse[i] = stackHeight
 	}
 
 	element := func(gtx C, i int) D {
 		gtx.Constraints = layout.Exact(image.Pt(gtx.Px(unit.Dp(120)), gtx.Px(unit.Dp(20))))
-		u := t.song.Patch.Instruments[t.CurrentInstrument].Units[i]
+		u := units[i]
 		unitNameLabel := LabelStyle{Text: u.Type, ShadeColor: black, Color: white, Font: labelDefaultFont, FontSize: unit.Sp(12)}
 		if unitNameLabel.Text == "" {
 			unitNameLabel.Text = "---"
@@ -210,8 +214,16 @@ func (t *Tracker) layoutInstrumentEditor(gtx C) D {
 			if i > 0 {
 				prevStackUse = t.StackUse[i-1]
 			}
-			if u.StackNeed() > prevStackUse || (i == len(t.StackUse)-1 && t.StackUse[i] != 0) {
+			if stackNeed := u.StackNeed(); stackNeed > prevStackUse {
 				unitNameLabel.Color = errorColor
+				typeString := u.Type
+				if u.Parameters["stereo"] == 1 {
+					typeString += " (stereo)"
+				}
+				t.Alert.Update(fmt.Sprintf("%v needs at least %v input signals, got %v", typeString, stackNeed, prevStackUse), Error, 0)
+			} else if i == len(units)-1 && t.StackUse[i] != 0 {
+				unitNameLabel.Color = warningColor
+				t.Alert.Update(fmt.Sprintf("Instrument leaves %v signal(s) on the stack", t.StackUse[i]), Warning, 0)
 			}
 		}
 		stackLabel := LabelStyle{Text: stackText, ShadeColor: black, Color: mediumEmphasisTextColor, Font: labelDefaultFont, FontSize: unit.Sp(12)}
@@ -224,7 +236,7 @@ func (t *Tracker) layoutInstrumentEditor(gtx C) D {
 		)
 	}
 
-	unitList := FilledDragList(t.Theme, t.UnitDragList, len(t.song.Patch.Instruments[t.CurrentInstrument].Units), element, t.SwapUnits)
+	unitList := FilledDragList(t.Theme, t.UnitDragList, len(units), element, t.SwapUnits)
 
 	if t.EditMode == EditUnits {
 		unitList.SelectedColor = cursorColor

tracker/keyevent.go

@@ -3,6 +3,7 @@ package tracker
 import (
 	"strconv"
 	"strings"
+	"time"
 
 	"gioui.org/app"
 	"gioui.org/io/key"
@@ -88,6 +89,7 @@ func (t *Tracker) KeyEvent(w *app.Window, e key.Event) bool {
 				contents, err := yaml.Marshal(t.song)
 				if err == nil {
 					w.WriteClipboard(string(contents))
+					t.Alert.Update("Song copied to clipboard", Notify, time.Second*3)
 				}
 				return true
 			}

tracker/layout.go

@@ -16,6 +16,7 @@ func (t *Tracker) Layout(gtx layout.Context) {
 	t.VerticalSplit.Layout(gtx,
 		t.layoutTop,
 		t.layoutBottom)
+	t.Alert.Layout(gtx)
 }
 
 func (t *Tracker) layoutBottom(gtx layout.Context) layout.Dimensions {

tracker/songpanel.go

@@ -4,6 +4,7 @@ import (
 	"image"
 	"math"
 	"runtime"
+	"time"
 
 	"gioui.org/f32"
 	"gioui.org/io/clipboard"
@@ -70,6 +71,7 @@ func (t *Tracker) layoutMenuBar(gtx C) D {
 		case 2:
 			if contents, err := yaml.Marshal(t.song); err == nil {
 				clipboard.WriteOp{Text: string(contents)}.Add(gtx.Ops)
+				t.Alert.Update("Song copied to clipboard", Notify, time.Second*3)
 			}
 		case 3:
 			clipboard.ReadOp{Tag: &t.Menus[1]}.Add(gtx.Ops)

tracker/theme.go

@@ -71,3 +71,5 @@ var errorColor = color.NRGBA{R: 207, G: 102, B: 121, A: 255}
 var menuHoverColor = color.NRGBA{R: 30, G: 31, B: 38, A: 255}
 
 var scrollBarColor = color.NRGBA{R: 255, G: 255, B: 255, A: 32}
+
+var warningColor = color.NRGBA{R: 251, G: 192, B: 45, A: 255}

tracker/tracker.go

@@ -83,6 +83,7 @@ type Tracker struct {
 	VerticalSplit         *Split
 	StackUse              []int
 	KeyPlaying            map[string]func()
+	Alert                 Alert
 
 	sequencer    *Sequencer
 	refresh      chan struct{}