From 1a898dd1b9b959433ff25ff3a522131b733c8527 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Thu, 1 Mar 2018 02:49:45 +0900
Subject: [PATCH] Add comments

---
 internal/restorable/copy.go  | 2 ++
 internal/restorable/image.go | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/internal/restorable/copy.go b/internal/restorable/copy.go
index fb4676822..b0df6c42f 100644
--- a/internal/restorable/copy.go
+++ b/internal/restorable/copy.go
@@ -27,6 +27,8 @@ import (
 // If origImg is a paletted image, an optimized copying method is used.
 //
 // CopyImage is used only internally but it is exposed for testing.
+//
+// TODO: CopyImage should return []byte (#521)
 func CopyImage(origImg image.Image) *image.RGBA {
 	size := origImg.Bounds().Size()
 	w, h := size.X, size.Y
diff --git a/internal/restorable/image.go b/internal/restorable/image.go
index e5b7e3175..a7e8ffb54 100644
--- a/internal/restorable/image.go
+++ b/internal/restorable/image.go
@@ -164,7 +164,11 @@ func (i *Image) ReplacePixels(pixels []byte, x, y, width, height int) {
 	if x < 0 || y < 0 || w <= x || h <= y || x+width <= 0 || y+height <= 0 || w < x+width || h < y+height {
 		panic(fmt.Sprintf("restorable: out of range x: %d, y: %d, width: %d, height: %d", x, y, width, height))
 	}
+
+	// TODO: Avoid making other images stale if possible.
+	// For this purpuse, images should remember which part of that is used for DrawImage.
 	theImages.makeStaleIfDependingOn(i)
+
 	i.image.ReplacePixels(pixels, x, y, width, height)
 
 	// Copy the pixels so that this works even p is modified just after ReplacePixels.