From caf4e9504f2a247d6af941b451428d1bd904718c Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Sat, 3 Mar 2018 20:35:44 +0900
Subject: [PATCH] graphics: ReplacePixels should work on shared textures

---
 image.go      | 45 ++++++++++++++++++++++++---------------------
 image_test.go |  5 ++++-
 2 files changed, 28 insertions(+), 22 deletions(-)

diff --git a/image.go b/image.go
index 81b30ae51..dc95b8a60 100644
--- a/image.go
+++ b/image.go
@@ -147,16 +147,6 @@ func (i *Image) isDisposed() bool {
 	return i.restorable == nil && i.sharedImagePart == nil
 }
 
-func (i *Image) restorableImage() *restorable.Image {
-	if i.restorable != nil {
-		return i.restorable
-	}
-	if i.sharedImagePart != nil {
-		return i.sharedImagePart.image()
-	}
-	return nil
-}
-
 // DrawImage draws the given image on the image i.
 //
 // DrawImage accepts the options. For details, see the document of DrawImageOptions.
@@ -355,6 +345,27 @@ func (i *Image) Dispose() error {
 	return nil
 }
 
+func (i *Image) region() (x, y, width, height int) {
+	if i.restorable != nil {
+		w, h := i.restorable.Size()
+		return 0, 0, w, h
+	}
+	if i.sharedImagePart != nil {
+		return i.sharedImagePart.region()
+	}
+	panic("not reached")
+}
+
+func (i *Image) restorableImage() *restorable.Image {
+	if i.restorable != nil {
+		return i.restorable
+	}
+	if i.sharedImagePart != nil {
+		return i.sharedImagePart.image()
+	}
+	return nil
+}
+
 // ReplacePixels replaces the pixels of the image with p.
 //
 // The given p must represent RGBA pre-multiplied alpha values. len(p) must equal to 4 * (image width) * (image height).
@@ -368,15 +379,14 @@ func (i *Image) Dispose() error {
 // ReplacePixels always returns nil as of 1.5.0-alpha.
 func (i *Image) ReplacePixels(p []byte) error {
 	i.copyCheck()
-	i.ensureNotShared()
 	if i.isDisposed() {
 		return nil
 	}
-	w, h := i.Size()
+	x, y, w, h := i.region()
 	if l := 4 * w * h; len(p) != l {
 		panic(fmt.Sprintf("ebiten: len(p) was %d but must be %d", len(p), l))
 	}
-	i.restorable.ReplacePixels(p, 0, 0, w, h)
+	i.restorableImage().ReplacePixels(p, x, y, w, h)
 	return nil
 }
 
@@ -515,14 +525,7 @@ func NewImageFromImage(source image.Image, filter Filter) (*Image, error) {
 	for j := 0; j < height; j++ {
 		copy(p[j*width*4:(j+1)*width*4], rgbaImg.Pix[j*rgbaImg.Stride:])
 	}
-
-	if s == nil {
-		_ = i.ReplacePixels(p)
-	} else {
-		x, y, width, height := s.region()
-		s.image().ReplacePixels(p, x, y, width, height)
-	}
-
+	_ = i.ReplacePixels(p)
 	return i, nil
 }
 
diff --git a/image_test.go b/image_test.go
index b32c1ced8..7a579bf9f 100644
--- a/image_test.go
+++ b/image_test.go
@@ -318,6 +318,10 @@ func TestImageDotByDotInversion(t *testing.T) {
 }
 
 func TestReplacePixels(t *testing.T) {
+	// Create a dummy image so that the shared texture is use and origImg's position is shfited.
+	dummyImg, _ := NewImageFromImage(image.NewRGBA(image.Rect(0, 0, 16, 16)), FilterDefault)
+	defer dummyImg.Dispose()
+
 	origImg, err := openImage("testdata/ebiten.png")
 	if err != nil {
 		t.Fatal(err)
@@ -369,7 +373,6 @@ func TestReplacePixels(t *testing.T) {
 			}
 		}
 	}
-
 }
 
 func TestImageDispose(t *testing.T) {