Merge pull request #17068 from peppy/fix-hit-distribution-rounding

Fix hit distribution graph midpoint rounding not looking great around zero

osu.Game.Tests/Visual/Ranking/TestSceneHitEventTimingDistributionGraph.cs

@@ -23,6 +23,12 @@ namespace osu.Game.Tests.Visual.Ranking
             createTest(CreateDistributedHitEvents());
         }
 
+        [Test]
+        public void TestManyDistributedEventsOffset()
+        {
+            createTest(CreateDistributedHitEvents(-3.5));
+        }
+
         [Test]
         public void TestAroundCentre()
         {

osu.Game/Screens/Ranking/Statistics/HitEventTimingDistributionGraph.cs

@@ -64,10 +64,22 @@ namespace osu.Game.Screens.Ranking.Statistics
             // Prevent div-by-0 by enforcing a minimum bin size
             binSize = Math.Max(1, binSize);
 
+            bool roundUp = true;
+
             foreach (var e in hitEvents)
             {
-                int binOffset = (int)Math.Round(e.TimeOffset / binSize, MidpointRounding.AwayFromZero);
-                bins[timing_distribution_centre_bin_index + binOffset]++;
+                double binOffset = e.TimeOffset / binSize;
+
+                // .NET's round midpoint handling doesn't provide a behaviour that works amazingly for display
+                // purposes here. We want midpoint rounding to roughly distribute evenly to each adjacent bucket
+                // so the easiest way is to cycle between downwards and upwards rounding as we process events.
+                if (Math.Abs(binOffset - (int)binOffset) == 0.5)
+                {
+                    binOffset = (int)binOffset + Math.Sign(binOffset) * (roundUp ? 1 : 0);
+                    roundUp = !roundUp;
+                }
+
+                bins[timing_distribution_centre_bin_index + (int)Math.Round(binOffset, MidpointRounding.AwayFromZero)]++;
             }
 
             int maxCount = bins.Max();