From f3b49e6543c4dd6dfe456d2d977a364fa0e28205 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Thu, 9 Mar 2023 22:57:01 +0900
Subject: [PATCH] internal/restorable: reduce more duplicated regions

---
 internal/restorable/image.go     | 10 ++++++++--
 internal/restorable/rect_test.go |  2 --
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/internal/restorable/image.go b/internal/restorable/image.go
index 1cccb8309..557e3c9bf 100644
--- a/internal/restorable/image.go
+++ b/internal/restorable/image.go
@@ -737,13 +737,19 @@ func regionToRectangle(region graphicsdriver.Region) image.Rectangle {
 }
 
 // removeDuplicatedRegions removes duplicated regions and returns a shrunk slice.
-// If a region covers preceding regions, the covered regions are removed.
+// If a region covers other regions, the covered regions are removed.
 func removeDuplicatedRegions(regions []image.Rectangle) []image.Rectangle {
 	for i, r := range regions {
 		if r.Empty() {
 			continue
 		}
-		for j, rr := range regions[:i] {
+		for j, rr := range regions {
+			if i == j {
+				continue
+			}
+			if rr.Empty() {
+				continue
+			}
 			if rr.In(r) {
 				regions[j] = image.Rectangle{}
 			}
diff --git a/internal/restorable/rect_test.go b/internal/restorable/rect_test.go
index 494f59573..143fbcc90 100644
--- a/internal/restorable/rect_test.go
+++ b/internal/restorable/rect_test.go
@@ -59,7 +59,6 @@ func TestRemoveDuplicatedRegions(t *testing.T) {
 			},
 			Out: []image.Rectangle{
 				image.Rect(0, 0, 2, 2),
-				image.Rect(0, 0, 1, 1),
 			},
 		},
 		{
@@ -104,7 +103,6 @@ func TestRemoveDuplicatedRegions(t *testing.T) {
 			},
 			Out: []image.Rectangle{
 				image.Rect(0, 0, 4, 4),
-				image.Rect(1, 1, 2, 2),
 			},
 		},
 		{