refactor logic to its own component and handle hit object to string conversion to its ruleset-specific composers

osu.Game.Rulesets.Mania/Edit/ManiaHitObjectComposer.cs

@@ -119,5 +119,8 @@ namespace osu.Game.Rulesets.Mania.Edit
                     beatSnapGrid.SelectionTimeRange = null;
             }
         }
+
+        public override IEnumerable<string> ConvertSelectionToString()
+            => EditorBeatmap.SelectedHitObjects.Cast<ManiaHitObject>().Select(h => $"{h.StartTime}|{h.Column}");
     }
 }

osu.Game.Rulesets.Osu/Edit/OsuHitObjectComposer.cs

@@ -82,6 +82,9 @@ namespace osu.Game.Rulesets.Osu.Edit
         protected override ComposeBlueprintContainer CreateBlueprintContainer()
             => new OsuBlueprintContainer(this);
 
+        public override IEnumerable<string> ConvertSelectionToString()
+            => selectedHitObjects.Cast<OsuHitObject>().Select(h => (h.IndexInCurrentCombo + 1).ToString());
+
         private DistanceSnapGrid distanceSnapGrid;
         private Container distanceSnapGridContainer;
 

osu.Game/Rulesets/Edit/HitObjectComposer.cs

@@ -438,6 +438,8 @@ namespace osu.Game.Rulesets.Edit
         /// </summary>
         public abstract bool CursorInPlacementArea { get; }
 
+        public virtual IEnumerable<string> ConvertSelectionToString() => Array.Empty<string>();
+
         #region IPositionSnapProvider
 
         public abstract SnapResult SnapScreenSpacePositionToValidTime(Vector2 screenSpacePosition);

osu.Game/Screens/Edit/Compose/ComposeScreen.cs

@@ -6,6 +6,8 @@ using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
+using osu.Framework.Input;
+using osu.Framework.Input.Bindings;
 using osu.Game.Beatmaps;
 using osu.Game.Rulesets;
 using osu.Game.Rulesets.Edit;
@@ -14,16 +16,19 @@ using osu.Game.Skinning;
 
 namespace osu.Game.Screens.Edit.Compose
 {
-    public class ComposeScreen : EditorScreenWithTimeline
+    public class ComposeScreen : EditorScreenWithTimeline, IKeyBindingHandler<PlatformAction>
     {
         [Resolved]
         private IBindable<WorkingBeatmap> beatmap { get; set; }
 
         private HitObjectComposer composer;
 
+        private SelectionHelper helper;
+
         public ComposeScreen()
             : base(EditorScreenMode.Compose)
         {
+            Add(helper = new SelectionHelper());
         }
 
         private Ruleset ruleset;
@@ -72,5 +77,21 @@ namespace osu.Game.Screens.Edit.Compose
             // this is intentionally done in two stages to ensure things are in a loaded state before exposing the ruleset to skin sources.
             return beatmapSkinProvider.WithChild(rulesetSkinProvider.WithChild(content));
         }
+
+        public bool OnPressed(PlatformAction action)
+        {
+            switch (action.ActionType)
+            {
+                case PlatformActionType.Copy:
+                    helper.CopySelectionToClipboard();
+                    return false;
+                default:
+                    return false;
+            };
+        }
+
+        public void OnReleased(PlatformAction action)
+        {
+        }
     }
 }

osu.Game/Screens/Edit/SelectionHelper.cs

@@ -0,0 +1,46 @@
+using System.Linq;
+using System.Text;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Platform;
+using osu.Game.Extensions;
+using osu.Game.Rulesets.Edit;
+
+namespace osu.Game.Screens.Edit
+{
+    public class SelectionHelper : Component
+    {
+        [Resolved]
+        private GameHost host { get; set; }
+
+        [Resolved]
+        private EditorClock clock { get; set; }
+
+        [Resolved]
+        private EditorBeatmap editorBeatmap { get; set; }
+
+        [Resolved(CanBeNull = true)]
+        private HitObjectComposer composer { get; set; }
+
+        public void CopySelectionToClipboard()
+        {
+            host.GetClipboard().SetText(formatSelectionAsString());
+        }
+
+        private string formatSelectionAsString()
+        {
+            const string separator = " - ";
+            var builder = new StringBuilder();
+
+            if (!editorBeatmap.SelectedHitObjects.Any())
+            {
+                builder.Append($"{clock.CurrentTime.ToEditorFormattedString()}{separator}");
+                return builder.ToString();
+            };
+
+            builder.Append(editorBeatmap.SelectedHitObjects.First().StartTime.ToEditorFormattedString());
+            builder.Append($" ({string.Join(',', composer.ConvertSelectionToString())}){separator}");
+            return builder.ToString();
+        }
+    }
+}