Add "auto" bank selection during placement

osu.Game/Rulesets/Edit/PlacementBlueprint.cs

@@ -32,6 +32,11 @@ namespace osu.Game.Rulesets.Edit
         /// </summary>
         public PlacementState PlacementActive { get; private set; }
 
+        /// <summary>
+        /// Whether the sample bank should be taken from the previous hit object.
+        /// </summary>
+        public bool AutomaticBankAssignment;
+
         /// <summary>
         /// The <see cref="HitObject"/> that is being placed.
         /// </summary>
@@ -86,11 +91,6 @@ namespace osu.Game.Rulesets.Edit
         /// <param name="commitStart">Whether this call is committing a value for HitObject.StartTime and continuing with further adjustments.</param>
         protected void BeginPlacement(bool commitStart = false)
         {
-            // Take the hitnormal sample of the last hit object
-            var lastHitNormal = getPreviousHitObject()?.Samples?.FirstOrDefault(o => o.Name == HitSampleInfo.HIT_NORMAL);
-            if (lastHitNormal != null)
-                HitObject.Samples[0] = lastHitNormal;
-
             placementHandler.BeginPlacement(HitObject);
             if (commitStart)
                 PlacementActive = PlacementState.Active;
@@ -155,6 +155,14 @@ namespace osu.Game.Rulesets.Edit
                 if (HitObject is IHasComboInformation comboInformation)
                     comboInformation.UpdateComboInformation(getPreviousHitObject() as IHasComboInformation);
             }
+
+            if (AutomaticBankAssignment)
+            {
+                // Take the hitnormal sample of the last hit object
+                var lastHitNormal = getPreviousHitObject()?.Samples?.FirstOrDefault(o => o.Name == HitSampleInfo.HIT_NORMAL);
+                if (lastHitNormal != null)
+                    HitObject.Samples[0] = lastHitNormal;
+            }
         }
 
         /// <summary>

osu.Game/Screens/Edit/Compose/Components/ComposeBlueprintContainer.cs

@@ -201,6 +201,8 @@ namespace osu.Game.Screens.Edit.Compose.Components
         {
             if (CurrentPlacement == null) return;
 
+            if (bankName == EditorSelectionHandler.HIT_BANK_AUTO)
+                CurrentPlacement.AutomaticBankAssignment = state == TernaryState.True;
             if (state == TernaryState.True)
                 CurrentPlacement.HitObject.Samples = CurrentPlacement.HitObject.Samples.Select(s => s.With(newBank: bankName)).ToList();
         }

osu.Game/Screens/Edit/Compose/Components/EditorSelectionHandler.cs

@@ -21,6 +21,12 @@ namespace osu.Game.Screens.Edit.Compose.Components
 {
     public partial class EditorSelectionHandler : SelectionHandler<HitObject>
     {
+        /// <summary>
+        /// A special bank name that is only used in the editor UI.
+        /// When selected and in placement mode, the bank of the last hit object will always be used.
+        /// </summary>
+        public const string HIT_BANK_AUTO = "auto";
+
         [Resolved]
         protected EditorBeatmap EditorBeatmap { get; private set; }
 
@@ -59,7 +65,7 @@ namespace osu.Game.Screens.Edit.Compose.Components
         /// </summary>
         private void createStateBindables()
         {
-            foreach (string bankName in HitSampleInfo.AllBanks)
+            foreach (string bankName in HitSampleInfo.AllBanks.Prepend(HIT_BANK_AUTO))
             {
                 var bindable = new Bindable<TernaryState>
                 {
@@ -100,6 +106,14 @@ namespace osu.Game.Screens.Edit.Compose.Components
                             }
                             else
                             {
+                                // Auto should just not apply if there's a selection already made.
+                                // Maybe we could make it a disabled button in the future, but right now the editor buttons don't support disabled state.
+                                if (bankName == HIT_BANK_AUTO)
+                                {
+                                    bindable.Value = TernaryState.False;
+                                    break;
+                                }
+
                                 AddSampleBank(bankName);
                             }