Centralise and share bar line generation code between rulesets

osu.Game/Rulesets/Objects/BarLineGenerator.cs

@@ -0,0 +1,58 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Collections.Generic;
+using System.Linq;
+using osu.Framework.MathUtils;
+using osu.Game.Beatmaps;
+using osu.Game.Beatmaps.ControlPoints;
+using osu.Game.Rulesets.Objects.Types;
+
+namespace osu.Game.Rulesets.Objects
+{
+    public class BarLineGenerator
+    {
+        /// <summary>
+        /// The generated bar lines.
+        /// </summary>
+        public readonly List<BarLine> BarLines = new List<BarLine>();
+
+        /// <summary>
+        /// Constructs and generates bar lines for provided beatmap.
+        /// </summary>
+        /// <param name="beatmap">The beatmap to generate bar lines for.</param>
+        public BarLineGenerator(IBeatmap beatmap)
+        {
+            if (beatmap.HitObjects.Count == 0)
+                return;
+
+            HitObject lastObject = beatmap.HitObjects.Last();
+            double lastHitTime = 1 + ((lastObject as IHasEndTime)?.EndTime ?? lastObject.StartTime);
+
+            var timingPoints = beatmap.ControlPointInfo.TimingPoints;
+
+            if (timingPoints.Count == 0)
+                return;
+
+            for (int i = 0; i < timingPoints.Count; i++)
+            {
+                TimingControlPoint currentTimingPoint = timingPoints[i];
+                int currentBeat = 0;
+
+                // Stop on the beat before the next timing point, or if there is no next timing point stop slightly past the last object
+                double endTime = i < timingPoints.Count - 1 ? timingPoints[i + 1].Time - currentTimingPoint.BeatLength : lastHitTime + currentTimingPoint.BeatLength * (int)currentTimingPoint.TimeSignature;
+
+                double barLength = currentTimingPoint.BeatLength * (int)currentTimingPoint.TimeSignature;
+
+                for (double t = currentTimingPoint.Time; Precision.DefinitelyBigger(endTime, t); t += barLength, currentBeat++)
+                {
+                    BarLines.Add(new BarLine
+                    {
+                        StartTime = t,
+                        Major = currentBeat % (int)currentTimingPoint.TimeSignature == 0
+                    });
+                }
+            }
+        }
+    }
+}