Merge pull request #27401 from bdach/fix-slider-tail-dim

Fix slider tails sometimes not dimming correctly

osu.Game.Rulesets.Osu/Objects/Drawables/DrawableOsuHitObject.cs

@@ -80,11 +80,29 @@ protected override void UpdateInitialTransforms()
             base.UpdateInitialTransforms();
 
             foreach (var piece in DimmablePieces)
+            {
+                // if the specified dimmable piece is a DHO, it is generally not safe to tack transforms onto it directly
+                // as they may be cleared via the `updateState()` DHO flow,
+                // so use `ApplyCustomUpdateState` instead. which does not have this pitfall.
+                if (piece is DrawableHitObject drawableObjectPiece)
+                {
+                    // this method can be called multiple times, and we don't want to subscribe to the event more than once,
+                    // so this is what it is going to have to be...
+                    drawableObjectPiece.ApplyCustomUpdateState -= applyDimToDrawableHitObject;
+                    drawableObjectPiece.ApplyCustomUpdateState += applyDimToDrawableHitObject;
+                }
+                else
+                    applyDim(piece);
+            }
+
+            void applyDim(Drawable piece)
             {
                 piece.FadeColour(new Color4(195, 195, 195, 255));
                 using (piece.BeginDelayedSequence(InitialLifetimeOffset - OsuHitWindows.MISS_WINDOW))
                     piece.FadeColour(Color4.White, 100);
             }
+
+            void applyDimToDrawableHitObject(DrawableHitObject dho, ArmedState _) => applyDim(dho);
         }
 
         protected sealed override double InitialLifetimeOffset => HitObject.TimePreempt;