windows: bug fix: crash when suspending/resuming when there are no de…

…vices

Updates hajimehoshi/ebiten#2318

api_winmm_windows.go

@@ -29,10 +29,7 @@ var (
 var (
 	procWaveOutOpen            = winmm.NewProc("waveOutOpen")
 	procWaveOutClose           = winmm.NewProc("waveOutClose")
-	procWaveOutPause           = winmm.NewProc("waveOutPause")
 	procWaveOutPrepareHeader   = winmm.NewProc("waveOutPrepareHeader")
-	procWaveOutReset           = winmm.NewProc("waveOutReset")
-	procWaveOutRestart         = winmm.NewProc("waveOutRestart")
 	procWaveOutUnprepareHeader = winmm.NewProc("waveOutUnprepareHeader")
 	procWaveOutWrite           = winmm.NewProc("waveOutWrite")
 )
@@ -140,17 +137,6 @@ func waveOutClose(hwo uintptr) error {
 	return nil
 }
 
-func waveOutPause(hwo uintptr) error {
-	r, _, e := procWaveOutPause.Call(hwo)
-	if _MMRESULT(r) != _MMSYSERR_NOERROR {
-		if e != nil && e != windows.ERROR_SUCCESS {
-			return fmt.Errorf("oto: waveOutPause failed: %w", e)
-		}
-		return fmt.Errorf("oto: waveOutPause failed: %w", _MMRESULT(r))
-	}
-	return nil
-}
-
 func waveOutPrepareHeader(hwo uintptr, pwh *_WAVEHDR) error {
 	r, _, e := procWaveOutPrepareHeader.Call(hwo, uintptr(unsafe.Pointer(pwh)), unsafe.Sizeof(_WAVEHDR{}))
 	runtime.KeepAlive(pwh)
@@ -163,28 +149,6 @@ func waveOutPrepareHeader(hwo uintptr, pwh *_WAVEHDR) error {
 	return nil
 }
 
-func waveOutReset(hwo uintptr) error {
-	r, _, e := procWaveOutReset.Call(hwo)
-	if _MMRESULT(r) != _MMSYSERR_NOERROR {
-		if e != nil && e != windows.ERROR_SUCCESS {
-			return fmt.Errorf("oto: waveOutReset failed: %w", e)
-		}
-		return fmt.Errorf("oto: waveOutReset failed: %w", _MMRESULT(r))
-	}
-	return nil
-}
-
-func waveOutRestart(hwo uintptr) error {
-	r, _, e := procWaveOutRestart.Call(hwo)
-	if _MMRESULT(r) != _MMSYSERR_NOERROR {
-		if e != nil && e != windows.ERROR_SUCCESS {
-			return fmt.Errorf("oto: waveOutRestart failed: %w", e)
-		}
-		return fmt.Errorf("oto: waveOutRestart failed: %w", _MMRESULT(r))
-	}
-	return nil
-}
-
 func waveOutUnprepareHeader(hwo uintptr, pwh *_WAVEHDR) error {
 	r, _, e := procWaveOutUnprepareHeader.Call(hwo, uintptr(unsafe.Pointer(pwh)), unsafe.Sizeof(_WAVEHDR{}))
 	runtime.KeepAlive(pwh)

driver_winmm_windows.go

@@ -83,6 +83,9 @@ type winmmContext struct {
 	loopEndCh chan error
 
 	cond *sync.Cond
+
+	suspended     bool
+	suspendedCond *sync.Cond
 }
 
 var theWinMMContext *winmmContext
@@ -94,6 +97,7 @@ func newWinMMContext(sampleRate, channelCount int, mux *mux.Mux, bufferSizeInByt
 		bufferSizeInBytes: bufferSizeInBytes,
 		mux:               mux,
 		cond:              sync.NewCond(&sync.Mutex{}),
+		suspendedCond:     sync.NewCond(&sync.Mutex{}),
 	}
 	theWinMMContext = c
 
@@ -151,54 +155,20 @@ func (c *winmmContext) start() error {
 }
 
 func (c *winmmContext) Suspend() error {
-	c.cond.L.Lock()
-	defer c.cond.L.Unlock()
+	c.suspendedCond.L.Lock()
+	c.suspended = true
+	c.suspendedCond.L.Unlock()
+	c.suspendedCond.Signal()
 
-	if err := c.err.Load(); err != nil {
-		return err.(error)
-	}
-
-	if err := waveOutPause(c.waveOut); err != nil {
-		return err
-	}
 	return nil
 }
 
 func (c *winmmContext) Resume() (ferr error) {
-	var restart bool
-	defer func() {
-		if ferr != nil {
-			return
-		}
-		if !restart {
-			return
-		}
-		if err := c.stopLoopIfNeeded(); err != nil {
-			ferr = err
-			return
-		}
-		if err := c.start(); err != nil {
-			ferr = err
-			return
-		}
-	}()
-
-	c.cond.L.Lock()
-	defer c.cond.L.Unlock()
-
-	if err := c.err.Load(); err != nil {
-		return err.(error)
-	}
-
-	// TODO: Ensure at least one header is queued?
+	c.suspendedCond.L.Lock()
+	c.suspended = false
+	c.suspendedCond.L.Unlock()
+	c.suspendedCond.Signal()
 
-	if err := waveOutRestart(c.waveOut); err != nil {
-		if errors.Is(err, _MMSYSERR_NODRIVER) {
-			restart = true
-			return nil
-		}
-		return err
-	}
 	return nil
 }
 
@@ -239,36 +209,19 @@ func (c *winmmContext) waitUntilHeaderAvailable() bool {
 	return c.err.Load() == nil && c.loopEndCh == nil
 }
 
-func (c *winmmContext) stopLoopIfNeeded() error {
-	ch := c.stopLoop()
-	if ch == nil {
-		return nil
-	}
-	return <-ch
-}
-
-func (c *winmmContext) stopLoop() chan error {
-	c.cond.L.Lock()
-	defer c.cond.L.Unlock()
-
-	// If the loop is already stopping, do nothing.
-	if c.loopEndCh != nil {
-		return nil
-	}
-
-	ch := make(chan error)
-	c.loopEndCh = ch
-	c.cond.Signal()
-	return ch
-}
-
 func (c *winmmContext) loop() {
 	defer func() {
 		if err := c.closeLoop(); err != nil {
 			c.err.TryStore(err)
 		}
 	}()
 	for {
+		c.suspendedCond.L.Lock()
+		for c.suspended {
+			c.suspendedCond.Wait()
+		}
+		c.suspendedCond.L.Unlock()
+
 		if !c.waitUntilHeaderAvailable() {
 			return
 		}