audio: Bug fix: isPlaying must consider two buffers in JS

internal/audio/audio.go

@@ -50,8 +50,7 @@ func withChannels(f func()) {
 	f()
 }
 
-func channelAt(i int) *channel {
+func emptyChannel() *channel {
-	if i == -1 {
 	for i, _ := range channels {
 		if !isPlaying(i) {
 			return channels[i]
@@ -59,11 +58,6 @@ func channelAt(i int) *channel {
 	}
 	return nil
 }
-	if !isPlaying(i) {
-		return channels[i]
-	}
-	return nil
-}
 
 func Tick() {
 	tick()
@@ -77,7 +71,7 @@ func Queue(data []byte) bool {
 			result = false
 			return
 		}
-		ch := channelAt(-1)
+		ch := emptyChannel()
 		if ch == nil {
 			result = false
 			return

internal/audio/audio_js.go

@@ -20,12 +20,7 @@ import (
 	"github.com/gopherjs/gopherjs/js"
 )
 
-// Keep this as global so as not to be destroyed by GC.
+var context *js.Object
-var (
-	nodes   = []*js.Object{}
-	dummies = []*js.Object{} // Dummy source nodes for iOS.
-	context *js.Object
-)
 
 type audioProcessor struct {
 	channel    int
@@ -63,22 +58,29 @@ func (a *audioProcessor) playChunk(buf []byte) {
 	s := context.Call("createBufferSource")
 	s.Set("buffer", b)
 	s.Call("connect", context.Get("destination"))
-	c := context.Get("currentTime").Float()
+
-	if a.position < c {
-		a.position = c
-	}
 	s.Call("start", a.position)
 	a.position += float64(len(il)) / float64(a.sampleRate)
 }
 
 func isPlaying(channel int) bool {
+	ch := channels[channel]
+	if 0 < len(ch.buffer) {
+		return true
+	}
+	a := audioProcessors[channel]
 	c := context.Get("currentTime").Float()
-	return c < audioProcessors[channel].position
+	return c < a.position
 }
 
 func tick() {
 	const bufferSize = 1024
+	c := context.Get("currentTime").Float()
 	for _, a := range audioProcessors {
+		if a.position < c {
+			a.position = c
+		}
+		// TODO: 4 is a magic number
 		a.playChunk(loadChannelBuffer(a.channel, bufferSize*4))
 	}
 }