Refactor flow of snapping through HitObjectComposer

osu.Game/Rulesets/Edit/HitObjectComposer.cs

@@ -14,6 +14,7 @@ using osu.Framework.Logging;
 using osu.Framework.Threading;
 using osu.Framework.Timing;
 using osu.Game.Beatmaps;
+using osu.Game.Beatmaps.ControlPoints;
 using osu.Game.Rulesets.Configuration;
 using osu.Game.Rulesets.Edit.Tools;
 using osu.Game.Rulesets.Mods;
@@ -39,6 +40,9 @@ namespace osu.Game.Rulesets.Edit
         [Resolved]
         protected IFrameBasedClock EditorClock { get; private set; }
 
+        [Resolved]
+        private BindableBeatDivisor beatDivisor { get; set; }
+
         private IWorkingBeatmap workingBeatmap;
         private Beatmap<TObject> playableBeatmap;
         private IBeatmapProcessor beatmapProcessor;
@@ -246,7 +250,7 @@ namespace osu.Game.Rulesets.Edit
         public void BeginPlacement(HitObject hitObject)
         {
             if (distanceSnapGrid != null)
-                hitObject.StartTime = GetSnappedTime(hitObject.StartTime, distanceSnapGrid.ToLocalSpace(inputManager.CurrentState.Mouse.Position));
+                hitObject.StartTime = GetSnappedPosition(distanceSnapGrid.ToLocalSpace(inputManager.CurrentState.Mouse.Position), hitObject.StartTime).time;
         }
 
         public void EndPlacement(HitObject hitObject)
@@ -257,11 +261,45 @@ namespace osu.Game.Rulesets.Edit
 
         public void Delete(HitObject hitObject) => EditorBeatmap.Remove(hitObject);
 
-        public override Vector2 GetSnappedPosition(Vector2 position) => distanceSnapGrid?.GetSnappedPosition(position) ?? position;
+        public override (Vector2 position, double time) GetSnappedPosition(Vector2 position, double time) => distanceSnapGrid?.GetSnappedPosition(position) ?? (position, time);
 
-        public override double GetSnappedTime(double startTime, Vector2 position) => distanceSnapGrid?.GetSnappedTime(position) ?? startTime;
+        public override float GetBeatSnapDistanceAt(double referenceTime)
+        {
+            DifficultyControlPoint difficultyPoint = EditorBeatmap.ControlPointInfo.DifficultyPointAt(referenceTime);
+            return (float)(100 * EditorBeatmap.BeatmapInfo.BaseDifficulty.SliderMultiplier * difficultyPoint.SpeedMultiplier / beatDivisor.Value);
+        }
 
-        public override float GetSnappedDistance(float distance) => distanceSnapGrid?.GetSnappedDistance(distance) ?? distance;
+        public override float DurationToDistance(double referenceTime, double duration)
+        {
+            double beatLength = EditorBeatmap.ControlPointInfo.TimingPointAt(referenceTime).BeatLength / beatDivisor.Value;
+            return (float)(duration / beatLength * GetBeatSnapDistanceAt(referenceTime));
+        }
+
+        public override double DistanceToDuration(double referenceTime, float distance)
+        {
+            double beatLength = EditorBeatmap.ControlPointInfo.TimingPointAt(referenceTime).BeatLength / beatDivisor.Value;
+            return distance / GetBeatSnapDistanceAt(referenceTime) * beatLength;
+        }
+
+        public override double GetSnappedDurationFromDistance(double referenceTime, float distance)
+            => beatSnap(referenceTime, DistanceToDuration(referenceTime, distance));
+
+        public override float GetSnappedDistanceFromDistance(double referenceTime, float distance)
+            => DurationToDistance(referenceTime, beatSnap(referenceTime, DistanceToDuration(referenceTime, distance)));
+
+        /// <summary>
+        /// Snaps a duration to the closest beat of a timing point applicable at the reference time.
+        /// </summary>
+        /// <param name="referenceTime">The time of the timing point which <paramref name="duration"/> resides in.</param>
+        /// <param name="duration">The duration to snap.</param>
+        /// <returns>A value that represents <paramref name="duration"/> snapped to the closest beat of the timing point.</returns>
+        private double beatSnap(double referenceTime, double duration)
+        {
+            double beatLength = EditorBeatmap.ControlPointInfo.TimingPointAt(referenceTime).BeatLength / beatDivisor.Value;
+
+            // A 1ms offset prevents rounding errors due to minute variations in duration
+            return (int)((duration + 1) / beatLength) * beatLength;
+        }
 
         protected override void Dispose(bool isDisposing)
         {
@@ -312,10 +350,45 @@ namespace osu.Game.Rulesets.Edit
         [CanBeNull]
         protected virtual DistanceSnapGrid CreateDistanceSnapGrid([NotNull] IEnumerable<HitObject> selectedHitObjects) => null;
 
-        public abstract Vector2 GetSnappedPosition(Vector2 position);
+        public abstract (Vector2 position, double time) GetSnappedPosition(Vector2 position, double time);
 
-        public abstract double GetSnappedTime(double startTime, Vector2 screenSpacePosition);
+        /// <summary>
+        /// Retrieves the distance between two points within a timing point that are one beat length apart.
+        /// </summary>
+        /// <param name="referenceTime">The time of the timing point.</param>
+        /// <returns>The distance between two points residing in the timing point that are one beat length apart.</returns>
+        public abstract float GetBeatSnapDistanceAt(double referenceTime);
 
-        public abstract float GetSnappedDistance(float distance);
+        /// <summary>
+        /// Converts a duration to a distance.
+        /// </summary>
+        /// <param name="referenceTime">The time of the timing point which <paramref name="duration"/> resides in.</param>
+        /// <param name="duration">The duration to convert.</param>
+        /// <returns>A value that represents <paramref name="duration"/> as a distance in the timing point.</returns>
+        public abstract float DurationToDistance(double referenceTime, double duration);
+
+        /// <summary>
+        /// Converts a distance to a duration.
+        /// </summary>
+        /// <param name="referenceTime">The time of the timing point which <paramref name="distance"/> resides in.</param>
+        /// <param name="distance">The distance to convert.</param>
+        /// <returns>A value that represents <paramref name="distance"/> as a duration in the timing point.</returns>
+        public abstract double DistanceToDuration(double referenceTime, float distance);
+
+        /// <summary>
+        /// Converts a distance to a snapped duration.
+        /// </summary>
+        /// <param name="referenceTime">The time of the timing point which <paramref name="distance"/> resides in.</param>
+        /// <param name="distance">The distance to convert.</param>
+        /// <returns>A value that represents <paramref name="distance"/> as a duration snapped to the closest beat of the timing point.</returns>
+        public abstract double GetSnappedDurationFromDistance(double referenceTime, float distance);
+
+        /// <summary>
+        /// Converts an unsnapped distance to a snapped distance.
+        /// </summary>
+        /// <param name="referenceTime">The time of the timing point which <paramref name="distance"/> resides in.</param>
+        /// <param name="distance">The distance to convert.</param>
+        /// <returns>A value that represents <paramref name="distance"/> snapped to the closest beat of the timing point.</returns>
+        public abstract float GetSnappedDistanceFromDistance(double referenceTime, float distance);
     }
 }