feat(tracker, gioui): add error message if vuanalyzer detects a NaN

Closes #50

tracker/gioui/run.go

@@ -3,6 +3,7 @@ package gioui
 import (
 	"fmt"
 	"os"
+	"time"
 
 	"gioui.org/app"
 	"gioui.org/io/clipboard"
@@ -29,6 +30,9 @@ func (t *Tracker) Run(w *app.Window) error {
 		case v := <-t.volumeChan:
 			t.lastVolume = v
 			w.Invalidate()
+		case e := <-t.errorChannel:
+			t.Alert.Update(e.Error(), Error, time.Second*5)
+			w.Invalidate()
 		case e := <-w.Events():
 			switch e := e.(type) {
 			case system.DestroyEvent:

tracker/gioui/tracker.go

@@ -69,6 +69,7 @@ type Tracker struct {
 	player       *tracker.Player
 	refresh      chan struct{}
 	playerCloser chan struct{}
+	errorChannel chan error
 	audioContext sointu.AudioContext
 
 	*tracker.Model
@@ -152,10 +153,11 @@ func New(audioContext sointu.AudioContext, synthService sointu.SynthService, syn
 		PatternOrderList:      &layout.List{Axis: layout.Vertical},
 		PatternOrderScrollBar: &ScrollBar{Axis: layout.Vertical},
 		ConfirmInstrDelete:    new(Dialog),
+		errorChannel:          make(chan error, 32),
 	}
 	t.Model = tracker.NewModel()
 	vuBufferObserver := make(chan []float32)
-	go tracker.VuAnalyzer(0.3, 1e-4, 1, -100, 20, vuBufferObserver, t.volumeChan)
+	go tracker.VuAnalyzer(0.3, 1e-4, 1, -100, 20, vuBufferObserver, t.volumeChan, t.errorChannel)
 	t.Theme.Palette.Fg = primaryColor
 	t.Theme.Palette.ContrastFg = black
 	t.SetEditMode(tracker.EditTracks)

tracker/vuanalyzer.go

@@ -1,6 +1,7 @@
 package tracker
 
 import (
+	"errors"
 	"math"
 )
 
@@ -28,7 +29,7 @@ type Volume struct {
 //
 // minVolume is just a hard limit for the vuanalyzer volumes, in decibels, just to
 // prevent negative infinities for volumes
-func VuAnalyzer(tau float64, attack float64, release float64, minVolume float64, maxVolume float64, bc <-chan []float32, vc chan<- Volume) {
+func VuAnalyzer(tau float64, attack float64, release float64, minVolume float64, maxVolume float64, bc <-chan []float32, vc chan<- Volume, ec chan<- error) {
 	v := Volume{Average: [2]float64{minVolume, minVolume}, Peak: [2]float64{minVolume, minVolume}}
 	alpha := 1 - math.Exp(-1.0/(tau*44100)) // from https://en.wikipedia.org/wiki/Exponential_smoothing
 	alphaAttack := 1 - math.Exp(-1.0/(attack*44100))
@@ -38,7 +39,11 @@ func VuAnalyzer(tau float64, attack float64, release float64, minVolume float64,
 			for i := 0; i < len(buffer); i += 2 {
 				sample2 := float64(buffer[i+j] * buffer[i+j])
 				if math.IsNaN(sample2) {
-					sample2 = float64(minVolume)
+					select {
+					case ec <- errors.New("NaN detected in master output"):
+					default:
+					}
+					continue
 				}
 				dB := 10 * math.Log10(float64(sample2))
 				if dB < minVolume || math.IsNaN(dB) {