Move combo index processing to BeatmapProcessor

osu.Game/Beatmaps/BeatmapProcessor.cs

@@ -1,7 +1,9 @@
 // Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
+using System.Linq;
 using osu.Game.Rulesets.Objects;
+using osu.Game.Rulesets.Objects.Types;
 
 namespace osu.Game.Beatmaps
 {
@@ -19,6 +21,29 @@ namespace osu.Game.Beatmaps
         /// </para>
         /// </summary>
         /// <param name="beatmap">The Beatmap to process.</param>
-        public virtual void PostProcess(Beatmap<TObject> beatmap) { }
+        public virtual void PostProcess(Beatmap<TObject> beatmap)
+        {
+            IHasComboIndex lastObj = null;
+
+            foreach (var obj in beatmap.HitObjects.OfType<IHasComboIndex>())
+            {
+                if (obj.NewCombo)
+                {
+                    obj.IndexInCurrentCombo = 0;
+                    if (lastObj != null)
+                    {
+                        lastObj.LastInCombo = true;
+                        obj.ComboIndex = lastObj.ComboIndex + 1;
+                    }
+                }
+                else if (lastObj != null)
+                {
+                    obj.IndexInCurrentCombo = lastObj.IndexInCurrentCombo + 1;
+                    obj.ComboIndex = lastObj.ComboIndex;
+                }
+
+                lastObj = obj;
+            }
+        }
     }
 }

osu.Game/Rulesets/Objects/Types/IHasComboIndex.cs

@@ -0,0 +1,26 @@
+// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+namespace osu.Game.Rulesets.Objects.Types
+{
+    /// <summary>
+    /// A HitObject that is part of a combo and has extended information about its position relative to other combo objects.
+    /// </summary>
+    public interface IHasComboIndex : IHasCombo
+    {
+        /// <summary>
+        /// The offset of this hitobject in the current combo.
+        /// </summary>
+        int IndexInCurrentCombo { get; set; }
+
+        /// <summary>
+        /// The offset of this hitobject in the current combo.
+        /// </summary>
+        int ComboIndex { get; set; }
+
+        /// <summary>
+        /// Whether this is the last object in the current combo.
+        /// </summary>
+        bool LastInCombo { get; set; }
+    }
+}

osu.Game/osu.Game.csproj

@@ -374,6 +374,7 @@
     <Compile Include="Overlays\Social\SocialPanel.cs" />
     <Compile Include="Rulesets\Mods\IApplicableToDrawableHitObject.cs" />
     <Compile Include="Rulesets\Objects\HitWindows.cs" />
+    <Compile Include="Rulesets\Objects\Types\IHasComboIndex.cs" />
     <Compile Include="Rulesets\Replays\Legacy\LegacyReplayFrame.cs" />
     <Compile Include="Rulesets\Replays\Legacy\ReplayButtonState.cs" />
     <Compile Include="Rulesets\Replays\ReplayFrame.cs" />