audio: Refactoring: Remove dependency on clock package

audio/audio.go

@@ -42,7 +42,6 @@ import (
 
 	"github.com/hajimehoshi/oto"
 
-	"github.com/hajimehoshi/ebiten/internal/clock"
 	"github.com/hajimehoshi/ebiten/internal/hooks"
 	"github.com/hajimehoshi/ebiten/internal/web"
 )
@@ -67,20 +66,6 @@ var (
 	theContextLock sync.Mutex
 )
 
-func init() {
-	hooks.AppendHookOnBeforeUpdate(func() error {
-		var err error
-		theContextLock.Lock()
-		if theContext != nil {
-			theContext.m.Lock()
-			err = theContext.err
-			theContext.m.Unlock()
-		}
-		theContextLock.Unlock()
-		return err
-	})
-}
-
 // NewContext creates a new audio context with the given sample rate.
 //
 // The sample rate is also used for decoding MP3 with audio/mp3 package
@@ -128,8 +113,6 @@ func newDriver(sampleRate int) (io.WriteCloser, error) {
 }
 
 func (c *Context) loop() {
-	initCh := make(chan struct{})
-
 	suspendCh := make(chan struct{}, 1)
 	resumeCh := make(chan struct{}, 1)
 	hooks.OnSuspendAudio(func() {
@@ -138,8 +121,23 @@ func (c *Context) loop() {
 	hooks.OnResumeAudio(func() {
 		resumeCh <- struct{}{}
 	})
-	clock.OnStart(func() {
-		close(initCh)
+
+	initCh := make(chan struct{})
+	var once sync.Once
+	hooks.AppendHookOnBeforeUpdate(func() error {
+		once.Do(func() {
+			close(initCh)
+		})
+
+		var err error
+		theContextLock.Lock()
+		if theContext != nil {
+			theContext.m.Lock()
+			err = theContext.err
+			theContext.m.Unlock()
+		}
+		theContextLock.Unlock()
+		return err
 	})
 
 	// Initialize oto.Player lazily to enable calling NewContext in an 'init' function.

internal/clock/clock.go

@@ -30,9 +30,6 @@ var (
 	fpsCount    = 0
 	tpsCount    = 0
 
-	onStartCalled bool
-	onStart       func()
-
 	m sync.Mutex
 )
 
@@ -50,12 +47,6 @@ func CurrentTPS() float64 {
 	return v
 }
 
-func OnStart(f func()) {
-	m.Lock()
-	onStart = f
-	m.Unlock()
-}
-
 func calcCountFromTPS(tps int64, now int64) int {
 	if tps == 0 {
 		return 0
@@ -132,13 +123,6 @@ func Update(tps int) int {
 	m.Lock()
 	defer m.Unlock()
 
-	if !onStartCalled {
-		if onStart != nil {
-			onStart()
-			onStartCalled = true
-		}
-	}
-
 	n := now()
 	c := 0
 	if tps == UncappedTPS {