From 0beddf551976f693de4fc3f00ffec3a000639857 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Wed, 17 Jun 2020 03:19:31 +0900
Subject: [PATCH] buffered: Bug fix: Race condition at checkDealeydCommandsNil

This change also renames checkDealeydCommandsNil to
checkDealeydCommandsFlushed, which makes more sense.

Updates #1195
---
 internal/buffered/command.go | 4 ++--
 internal/buffered/image.go   | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/internal/buffered/command.go b/internal/buffered/command.go
index cf4f39bf5..f74112a76 100644
--- a/internal/buffered/command.go
+++ b/internal/buffered/command.go
@@ -89,8 +89,8 @@ func tryAddDelayedCommandSlow(f func(obj interface{}) error, ondelayed func() in
 	}
 }
 
-func checkDelayedCommandsNil(fname string) {
-	if delayedCommands != nil {
+func checkDelayedCommandsFlushed(fname string) {
+	if atomic.LoadUint32(&delayedCommandsFlushed) == 0 {
 		panic("buffered: the command queue is not available yet at " + fname)
 	}
 }
diff --git a/internal/buffered/image.go b/internal/buffered/image.go
index bb0ec1d37..9eba55329 100644
--- a/internal/buffered/image.go
+++ b/internal/buffered/image.go
@@ -125,7 +125,7 @@ func (i *Image) MarkDisposed() {
 }
 
 func (img *Image) Pixels(x, y, width, height int) (pix []byte, err error) {
-	checkDelayedCommandsNil("Pixels")
+	checkDelayedCommandsFlushed("Pixels")
 
 	if !image.Rect(x, y, x+width, y+height).In(image.Rect(0, 0, img.width, img.height)) {
 		return nil, fmt.Errorf("buffered: out of range")
@@ -160,7 +160,7 @@ func (img *Image) Pixels(x, y, width, height int) (pix []byte, err error) {
 }
 
 func (i *Image) Dump(name string, blackbg bool) error {
-	checkDelayedCommandsNil("Dump")
+	checkDelayedCommandsFlushed("Dump")
 	return i.img.Dump(name, blackbg)
 }