Allow judging at most one swell tick per frame

osu.Game.Rulesets.Taiko.Tests/Judgements/TestSceneSwellJudgements.cs

@@ -115,6 +115,48 @@ public void TestHitNoneSwell()
             AddAssert("all tick offsets are 0", () => JudgementResults.Where(r => r.HitObject is SwellTick).All(r => r.TimeOffset == 0));
         }
 
+        [Test]
+        public void TestAtMostOneSwellTickJudgedPerFrame()
+        {
+            const double swell_time = 1000;
+
+            Swell swell = new Swell
+            {
+                StartTime = swell_time,
+                Duration = 1000,
+                RequiredHits = 10
+            };
+
+            List<ReplayFrame> frames = new List<ReplayFrame>
+            {
+                new TaikoReplayFrame(1000),
+                new TaikoReplayFrame(1250, TaikoAction.LeftCentre, TaikoAction.LeftRim),
+                new TaikoReplayFrame(1251),
+                new TaikoReplayFrame(1500, TaikoAction.LeftCentre, TaikoAction.LeftRim, TaikoAction.RightCentre, TaikoAction.RightRim),
+                new TaikoReplayFrame(1501),
+                new TaikoReplayFrame(2000),
+            };
+
+            PerformTest(frames, CreateBeatmap(swell));
+
+            AssertJudgementCount(11);
+
+            // this is a charitable interpretation of the inputs.
+            //
+            // for the frame at time 1250, we only count either one of the input actions - simple.
+            //
+            // for the frame at time 1500, we give the user the benefit of the doubt,
+            // and we ignore actions that wouldn't otherwise cause a hit due to not alternating,
+            // but we still count one (just one) of the actions that _would_ normally cause a hit.
+            // this is done as a courtesy to avoid stuff like key chattering after press blocking legitimate inputs.
+            for (int i = 0; i < 2; i++)
+                AssertResult<SwellTick>(i, HitResult.IgnoreHit);
+            for (int i = 2; i < swell.RequiredHits; i++)
+                AssertResult<SwellTick>(i, HitResult.IgnoreMiss);
+
+            AssertResult<Swell>(0, HitResult.IgnoreMiss);
+        }
+
         /// <summary>
         /// Ensure input is correctly sent to subsequent hits if a swell is fully completed.
         /// </summary>

osu.Game.Rulesets.Taiko/Objects/Drawables/DrawableSwell.cs

@@ -17,6 +17,7 @@
 using osu.Framework.Input.Events;
 using osu.Game.Rulesets.Objects;
 using osu.Game.Rulesets.Taiko.Skinning.Default;
+using osu.Game.Screens.Play;
 using osu.Game.Skinning;
 
 namespace osu.Game.Rulesets.Taiko.Objects.Drawables
@@ -38,6 +39,8 @@ public partial class DrawableSwell : DrawableTaikoHitObject<Swell>
         private readonly CircularContainer targetRing;
         private readonly CircularContainer expandingRing;
 
+        private double? lastPressHandleTime;
+
         public override bool DisplayResult => false;
 
         public DrawableSwell()
@@ -140,6 +143,7 @@ protected override void OnFree()
             UnproxyContent();
 
             lastWasCentre = null;
+            lastPressHandleTime = null;
         }
 
         protected override void AddNestedHitObject(DrawableHitObject hitObject)
@@ -266,6 +270,9 @@ protected override void Update()
                 ProxyContent();
             else
                 UnproxyContent();
+
+            if ((Clock as IGameplayClock)?.IsRewinding == true)
+                lastPressHandleTime = null;
         }
 
         private bool? lastWasCentre;
@@ -285,7 +292,14 @@ public override bool OnPressed(KeyBindingPressEvent<TaikoAction> e)
             if (lastWasCentre == isCentre)
                 return false;
 
+            // If we've already successfully judged a tick this frame, do not judge more.
+            // Note that the ordering is important here - this is intentionally placed after the alternating check.
+            // That is done to prevent accidental double inputs blocking simultaneous but legitimate hits from registering.
+            if (lastPressHandleTime == Time.Current)
+                return true;
+
             lastWasCentre = isCentre;
+            lastPressHandleTime = Time.Current;
 
             UpdateResult(true);