From dbb8a5e873e273869cd8b441afcb9f677a9c36c7 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Sat, 7 Sep 2019 01:59:36 +0900
Subject: [PATCH] audio: Block all the players when suspended

This avoid to write 0 bytes when the app is in background. This
should reduce CPU usage.

Updates #931
---
 audio/audio.go | 29 +++++++++--------------------
 1 file changed, 9 insertions(+), 20 deletions(-)

diff --git a/audio/audio.go b/audio/audio.go
index 97621ccd2..d7ec2e79e 100644
--- a/audio/audio.go
+++ b/audio/audio.go
@@ -62,12 +62,12 @@ type Context struct {
 
 	sampleRate int
 	err        error
-	suspended  bool
 	ready      bool
 
 	players map[*playerImpl]struct{}
 
-	m sync.Mutex
+	m         sync.Mutex
+	semaphore chan struct{}
 }
 
 var (
@@ -99,19 +99,16 @@ func NewContext(sampleRate int) (*Context, error) {
 		c:          newContext(sampleRate),
 		players:    map[*playerImpl]struct{}{},
 		inited:     make(chan struct{}),
+		semaphore:  make(chan struct{}, 1),
 	}
 	theContext = c
 
 	h := getHook()
 	h.OnSuspendAudio(func() {
-		c.m.Lock()
-		c.suspended = true
-		c.m.Unlock()
+		c.semaphore <- struct{}{}
 	})
 	h.OnResumeAudio(func() {
-		c.m.Lock()
-		c.suspended = false
-		c.m.Unlock()
+		<-c.semaphore
 	})
 
 	h.AppendHookOnBeforeUpdate(func() error {
@@ -141,13 +138,6 @@ func CurrentContext() *Context {
 	return c
 }
 
-func (c *Context) playable() bool {
-	c.m.Lock()
-	s := c.suspended
-	c.m.Unlock()
-	return !s
-}
-
 func (c *Context) hasError() bool {
 	c.m.Lock()
 	r := c.err != nil
@@ -447,11 +437,10 @@ func (p *playerImpl) read() ([]byte, bool) {
 
 	const bufSize = 2048
 
-	if !p.context.playable() {
-		// Fill zero values, or the driver can block forever as trying to proceed.
-		buf := make([]byte, bufSize)
-		return buf, true
-	}
+	p.context.semaphore <- struct{}{}
+	defer func() {
+		<-p.context.semaphore
+	}()
 
 	newBuf := make([]byte, bufSize-len(p.buf))
 	n, err := p.src.Read(newBuf)