From b901d2acb1df161c6fc39343da4d1661bbe49a29 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Wed, 27 Jul 2016 03:09:56 +0900
Subject: [PATCH] graphics: Avoid ReadPixels when the image is volatile

---
 imageimpl.go | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/imageimpl.go b/imageimpl.go
index 4a366ef61..4a3baf220 100644
--- a/imageimpl.go
+++ b/imageimpl.go
@@ -194,6 +194,9 @@ func (i *imageImpl) ensurePixels(context *opengl.Context) error {
 	if i.disposed {
 		return nil
 	}
+	if i.volatile {
+		return nil
+	}
 	if err := i.pixels.ReadPixelsFromVRAMIfStale(context); err != nil {
 		return err
 	}
@@ -217,7 +220,7 @@ func (i *imageImpl) resetPixelsIfDependingOn(target *imageImpl, context *opengl.
 	if !i.pixels.DependsOn(target.image) {
 		return nil
 	}
-	if context == nil {
+	if context == nil || i.volatile {
 		// context is nil when this is not initialized yet.
 		i.pixels.MakeStale()
 		return nil