Piano can now play square waves

examples/piano/main.go

@@ -1,5 +1,7 @@
 package main
 
+import "math"
+import "errors"
 import "github.com/faiface/beep"
 import "github.com/faiface/beep/speaker"
 import "github.com/faiface/beep/generators"
@@ -13,7 +15,7 @@ import _ "git.tebibyte.media/sashakoshka/tomo/backends/x"
 const sampleRate = 44100
 const bufferSize = 256
 var   tuning     = music.EqualTemparment { A4: 440 }
-
+var   waveform   = 0
 var playing = map[music.Note] *beep.Ctrl { }
 
 func main () {
@@ -27,8 +29,20 @@ func run () {
 	container := basicElements.NewContainer(basicLayouts.Vertical { true, true })
 	window.Adopt(container)
 
+	controlBar := basicElements.NewContainer(basicLayouts.Horizontal { true, false })
 	label := basicElements.NewLabel("Play a song!", false)
-	container.Adopt(label, false)
+	controlBar.Adopt(label, true)
+	waveformButton := basicElements.NewButton("Sine")
+	waveformButton.OnClick (func () {
+		waveform = (waveform + 1) % 2
+		switch waveform {
+		case 0: waveformButton.SetText("Sine")
+		case 1: waveformButton.SetText("Square")
+		}
+	})
+	controlBar.Adopt(waveformButton, false)
+	container.Adopt(controlBar, false)
+	
 	piano := fun.NewPiano(3, 5)
 	container.Adopt(piano, true)
 	piano.OnPress(playNote)
@@ -48,8 +62,11 @@ func stopNote (note music.Note) {
 }
 
 func playNote (note music.Note) {
-	streamer, err := generators.SinTone(sampleRate, int(tuning.Tune(note)))
-	if err != nil { panic(err.Error()) }
+	var streamer beep.Streamer
+	switch waveform {
+	case 0: streamer, _ = generators.SinTone(sampleRate, int(tuning.Tune(note)))
+	case 1: streamer, _ = SquareTone(sampleRate, int(tuning.Tune(note)))
+	}
 
 	stopNote(note)
 	speaker.Lock()
@@ -57,3 +74,47 @@ func playNote (note music.Note) {
 	speaker.Unlock()
 	speaker.Play(playing[note])
 }
+
+// https://github.com/faiface/beep/blob/v1.1.0/generators/toner.go
+// Adapted to be a square wave instead
+
+type toneStreamer struct {
+	stat  float64
+	delta float64
+}
+
+func SquareTone (sr beep.SampleRate, freq int) (beep.Streamer, error) {
+	if int(sr) / freq < 2 {
+		return nil, errors.New (
+			"square tone generator: samplerate must be at least " +
+			"2 times greater then frequency")
+	}
+	tone := new(toneStreamer)
+	tone.stat = 0.0
+	srf := float64(sr)
+	ff := float64(freq)
+	steps := srf / ff
+	tone.delta = 1.0 / steps
+	return tone, nil
+}
+
+func (tone *toneStreamer) nextSample () (sample float64) {
+	if tone.stat > 0.5 {
+		sample = 1
+	} else {
+		sample = 0
+	}
+	_, tone.stat = math.Modf(tone.stat + tone.delta)
+	return
+}
+
+func (tone *toneStreamer) Stream (buf [][2]float64) (int, bool) {
+	for i := 0; i < len(buf); i++ {
+		s := tone.nextSample()
+		buf[i] = [2]float64{s, s}
+	}
+	return len(buf), true
+}
+func (tone *toneStreamer) Err () error {
+	return nil
+}