From 98141430b0cb6d4b45397eadbf8b537020330af1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bart=C5=82omiej=20Dach?= <dach.bartlomiej@gmail.com>
Date: Mon, 14 Oct 2024 14:48:07 +0200
Subject: [PATCH 1/2] Add failing tests

---
 .../Editor/TestSceneManiaSelectionHandler.cs  | 40 +++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/osu.Game.Rulesets.Mania.Tests/Editor/TestSceneManiaSelectionHandler.cs b/osu.Game.Rulesets.Mania.Tests/Editor/TestSceneManiaSelectionHandler.cs
index 4285ef2029..a70b90789d 100644
--- a/osu.Game.Rulesets.Mania.Tests/Editor/TestSceneManiaSelectionHandler.cs
+++ b/osu.Game.Rulesets.Mania.Tests/Editor/TestSceneManiaSelectionHandler.cs
@@ -118,5 +118,45 @@ public void TestOffScreenObjectsRemainSelectedOnColumnChange()
             AddAssert("all objects in last column", () => EditorBeatmap.HitObjects.All(ho => ((ManiaHitObject)ho).Column == 3));
             AddAssert("all objects remain selected", () => EditorBeatmap.SelectedHitObjects.SequenceEqual(EditorBeatmap.HitObjects));
         }
+
+        [Test]
+        public void TestOffScreenObjectsRemainSelectedOnHorizontalFlip()
+        {
+            AddStep("create objects", () =>
+            {
+                for (int i = 0; i < 20; ++i)
+                    EditorBeatmap.Add(new Note { StartTime = 1000 * i, Column = i % 4 });
+            });
+
+            AddStep("select everything", () => EditorBeatmap.SelectedHitObjects.AddRange(EditorBeatmap.HitObjects));
+            AddStep("flip", () =>
+            {
+                InputManager.PressKey(Key.ControlLeft);
+                InputManager.Key(Key.H);
+                InputManager.ReleaseKey(Key.ControlLeft);
+            });
+
+            AddAssert("all objects remain selected", () => EditorBeatmap.SelectedHitObjects.SequenceEqual(EditorBeatmap.HitObjects));
+        }
+
+        [Test]
+        public void TestOffScreenObjectsRemainSelectedOnVerticalFlip()
+        {
+            AddStep("create objects", () =>
+            {
+                for (int i = 0; i < 20; ++i)
+                    EditorBeatmap.Add(new Note { StartTime = 1000 * i, Column = i % 4 });
+            });
+
+            AddStep("select everything", () => EditorBeatmap.SelectedHitObjects.AddRange(EditorBeatmap.HitObjects));
+            AddStep("flip", () =>
+            {
+                InputManager.PressKey(Key.ControlLeft);
+                InputManager.Key(Key.J);
+                InputManager.ReleaseKey(Key.ControlLeft);
+            });
+
+            AddAssert("all objects remain selected", () => EditorBeatmap.SelectedHitObjects.SequenceEqual(EditorBeatmap.HitObjects.Reverse()));
+        }
     }
 }

From 59655a18307d018968710e0abc9584ef88ab90dc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bart=C5=82omiej=20Dach?= <dach.bartlomiej@gmail.com>
Date: Mon, 14 Oct 2024 14:48:09 +0200
Subject: [PATCH 2/2] Fix flip operations sometimes not preserving selection

Closes https://github.com/ppy/osu/issues/30250.
---
 .../Edit/ManiaSelectionHandler.cs              | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/osu.Game.Rulesets.Mania/Edit/ManiaSelectionHandler.cs b/osu.Game.Rulesets.Mania/Edit/ManiaSelectionHandler.cs
index 7e0991a4d4..74e616ac3f 100644
--- a/osu.Game.Rulesets.Mania/Edit/ManiaSelectionHandler.cs
+++ b/osu.Game.Rulesets.Mania/Edit/ManiaSelectionHandler.cs
@@ -54,9 +54,8 @@ public override bool HandleFlip(Direction direction, bool flipOverOrigin)
                     int firstColumn = flipOverOrigin ? 0 : selectedObjects.Min(ho => ho.Column);
                     int lastColumn = flipOverOrigin ? (int)EditorBeatmap.BeatmapInfo.Difficulty.CircleSize - 1 : selectedObjects.Max(ho => ho.Column);
 
-                    EditorBeatmap.PerformOnSelection(hitObject =>
+                    performOnSelection(maniaObject =>
                     {
-                        var maniaObject = (ManiaHitObject)hitObject;
                         maniaPlayfield.Remove(maniaObject);
                         maniaObject.Column = firstColumn + (lastColumn - maniaObject.Column);
                         maniaPlayfield.Add(maniaObject);
@@ -71,7 +70,7 @@ public override bool HandleFlip(Direction direction, bool flipOverOrigin)
                     double selectionStartTime = selectedObjects.Min(ho => ho.StartTime);
                     double selectionEndTime = selectedObjects.Max(ho => ho.GetEndTime());
 
-                    EditorBeatmap.PerformOnSelection(hitObject =>
+                    performOnSelection(hitObject =>
                     {
                         hitObject.StartTime = selectionStartTime + (selectionEndTime - hitObject.GetEndTime());
                     });
@@ -117,14 +116,21 @@ private void performColumnMovement(int lastColumn, MoveSelectionEvent<HitObject>
 
             columnDelta = Math.Clamp(columnDelta, -minColumn, maniaPlayfield.TotalColumns - 1 - maxColumn);
 
-            EditorBeatmap.PerformOnSelection(h =>
+            performOnSelection(h =>
             {
                 maniaPlayfield.Remove(h);
-                ((ManiaHitObject)h).Column += columnDelta;
+                h.Column += columnDelta;
                 maniaPlayfield.Add(h);
             });
+        }
 
-            // `HitObjectUsageEventBuffer`'s usage transferal flows and the playfield's `SetKeepAlive()` functionality do not combine well with this operation's usage pattern,
+        private void performOnSelection(Action<ManiaHitObject> action)
+        {
+            var selectedObjects = EditorBeatmap.SelectedHitObjects.OfType<ManiaHitObject>().ToArray();
+
+            EditorBeatmap.PerformOnSelection(h => action.Invoke((ManiaHitObject)h));
+
+            // `HitObjectUsageEventBuffer`'s usage transferal flows and the playfield's `SetKeepAlive()` functionality do not combine well with mania's usage patterns,
             // leading to selections being sometimes partially dropped if some of the objects being moved are off screen
             // (check blame for detailed explanation).
             // thus, ensure that selection is preserved manually.