From c60a32a4797db3bd694dca547305ffb6248b6cb5 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Sat, 16 Nov 2019 01:51:32 +0900
Subject: [PATCH] graphics: Avoid all copying pixels

This is a breaking change: ReplacePixels now takes the ownership
of the given pixels.

Fixes #983
---
 image.go                          |  3 +++
 image_test.go                     | 15 ++-------------
 internal/graphicscommand/image.go |  4 +---
 internal/restorable/rect.go       | 11 ++++-------
 4 files changed, 10 insertions(+), 23 deletions(-)

diff --git a/image.go b/image.go
index 42a2f9558..f4e3428e9 100644
--- a/image.go
+++ b/image.go
@@ -432,6 +432,9 @@ func (i *Image) Dispose() error {
 //
 // The given p must represent RGBA pre-multiplied alpha values. len(p) must equal to 4 * (image width) * (image height).
 //
+// ReplacePixels takes the ownership of the given p. This means that p must not be modified after ReplacePixels is
+// called.
+//
 // ReplacePixels may be slow (as for implementation, this calls glTexSubImage2D).
 //
 // When len(p) is not appropriate, ReplacePixels panics.
diff --git a/image_test.go b/image_test.go
index c57cb3c42..a9cefbc33 100644
--- a/image_test.go
+++ b/image_test.go
@@ -354,19 +354,8 @@ func TestImageReplacePixels(t *testing.T) {
 		t.Fatal(err)
 		return
 	}
-	// Even if p is changed after calling ReplacePixel, img0 uses the original values.
-	for i := range p {
-		p[i] = 0
-	}
-	for j := 0; j < img0.Bounds().Size().Y; j++ {
-		for i := 0; i < img0.Bounds().Size().X; i++ {
-			got := img0.At(i, j)
-			want := color.RGBA{0x80, 0x80, 0x80, 0x80}
-			if got != want {
-				t.Errorf("img0 At(%d, %d): got %#v; want %#v", i, j, got, want)
-			}
-		}
-	}
+
+	// p cannot be modified as of 1.11.0-alpha.
 }
 
 func TestImageReplacePixelsNil(t *testing.T) {
diff --git a/internal/graphicscommand/image.go b/internal/graphicscommand/image.go
index 94f29e3c1..ef6f89f55 100644
--- a/internal/graphicscommand/image.go
+++ b/internal/graphicscommand/image.go
@@ -155,15 +155,13 @@ func (i *Image) Pixels() []byte {
 	return c.result
 }
 
-func (i *Image) ReplacePixels(p []byte, x, y, width, height int) {
+func (i *Image) ReplacePixels(pixels []byte, x, y, width, height int) {
 	// ReplacePixels for a part might invalidate the current image that are drawn by DrawTriangles (#593, #738).
 	if i.lastCommand == lastCommandDrawTriangles {
 		if x != 0 || y != 0 || i.width != width || i.height != height {
 			panic("graphicscommand: ReplacePixels for a part after DrawTriangles is forbidden")
 		}
 	}
-	pixels := make([]byte, len(p))
-	copy(pixels, p)
 	c := &replacePixelsCommand{
 		dst:    i,
 		pixels: pixels,
diff --git a/internal/restorable/rect.go b/internal/restorable/rect.go
index 842d43e8c..54088d7c4 100644
--- a/internal/restorable/rect.go
+++ b/internal/restorable/rect.go
@@ -37,16 +37,13 @@ func (rtp *rectToPixels) addOrReplace(pixels []byte, x, y, width, height int) {
 		rtp.m = map[image.Rectangle][]byte{}
 	}
 
-	copied := make([]byte, len(pixels))
-	copy(copied, pixels)
-
 	newr := image.Rect(x, y, x+width, y+height)
 	for r := range rtp.m {
 		if r == newr {
 			// Replace the region.
-			rtp.m[r] = copied
+			rtp.m[r] = pixels
 			if r == rtp.lastR {
-				rtp.lastPix = copied
+				rtp.lastPix = pixels
 			}
 			return
 		}
@@ -56,9 +53,9 @@ func (rtp *rectToPixels) addOrReplace(pixels []byte, x, y, width, height int) {
 	}
 
 	// Add the region.
-	rtp.m[newr] = copied
+	rtp.m[newr] = pixels
 	if newr == rtp.lastR {
-		rtp.lastPix = copied
+		rtp.lastPix = pixels
 	}
 }