Add distance snapping to catch editor

osu.Game.Rulesets.Catch/Edit/CatchHitObjectComposer.cs

@@ -2,14 +2,23 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System.Collections.Generic;
+using System.Linq;
+using JetBrains.Annotations;
 using osu.Framework.Allocation;
+using osu.Framework.Bindables;
 using osu.Framework.Graphics;
+using osu.Framework.Graphics.Sprites;
+using osu.Framework.Input;
 using osu.Game.Beatmaps;
+using osu.Game.Graphics.UserInterface;
 using osu.Game.Rulesets.Catch.Objects;
+using osu.Game.Rulesets.Catch.UI;
 using osu.Game.Rulesets.Edit;
 using osu.Game.Rulesets.Edit.Tools;
 using osu.Game.Rulesets.Mods;
+using osu.Game.Rulesets.Objects;
 using osu.Game.Rulesets.UI;
+using osu.Game.Screens.Edit.Components.TernaryButtons;
 using osu.Game.Screens.Edit.Compose.Components;
 using osuTK;
 
@@ -17,6 +26,14 @@ namespace osu.Game.Rulesets.Catch.Edit
 {
     public class CatchHitObjectComposer : HitObjectComposer<CatchHitObject>
     {
+        private const float distance_snap_radius = 50;
+
+        private CatchDistanceSnapGrid distanceSnapGrid;
+
+        private readonly Bindable<TernaryState> distanceSnapToggle = new Bindable<TernaryState>();
+
+        private InputManager inputManager;
+
         public CatchHitObjectComposer(CatchRuleset ruleset)
             : base(ruleset)
         {
@@ -30,6 +47,27 @@ namespace osu.Game.Rulesets.Catch.Edit
                 RelativeSizeAxes = Axes.Both,
                 PlayfieldBorderStyle = { Value = PlayfieldBorderStyle.Corners }
             });
+
+            LayerBelowRuleset.Add(distanceSnapGrid = new CatchDistanceSnapGrid(new[]
+            {
+                0.0,
+                Catcher.BASE_SPEED, -Catcher.BASE_SPEED,
+                Catcher.BASE_SPEED / 2, -Catcher.BASE_SPEED / 2,
+            }));
+        }
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+
+            inputManager = GetContainingInputManager();
+        }
+
+        protected override void Update()
+        {
+            base.Update();
+
+            updateDistanceSnapGrid();
         }
 
         protected override DrawableRuleset<CatchHitObject> CreateDrawableRuleset(Ruleset ruleset, IBeatmap beatmap, IReadOnlyList<Mod> mods = null) =>
@@ -42,14 +80,90 @@ namespace osu.Game.Rulesets.Catch.Edit
             new BananaShowerCompositionTool()
         };
 
+        protected override IEnumerable<TernaryButton> CreateTernaryButtons() => base.CreateTernaryButtons().Concat(new[]
+        {
+            new TernaryButton(distanceSnapToggle, "Distance Snap", () => new SpriteIcon { Icon = FontAwesome.Solid.Ruler })
+        });
+
         public override SnapResult SnapScreenSpacePositionToValidTime(Vector2 screenSpacePosition)
         {
             var result = base.SnapScreenSpacePositionToValidTime(screenSpacePosition);
-            // TODO: implement position snap
             result.ScreenSpacePosition.X = screenSpacePosition.X;
+
+            if (distanceSnapGrid.IsPresent && distanceSnapGrid.GetSnappedPosition(result.ScreenSpacePosition) is SnapResult snapResult &&
+                Vector2.Distance(snapResult.ScreenSpacePosition, result.ScreenSpacePosition) < distance_snap_radius)
+            {
+                result = snapResult;
+            }
+
             return result;
         }
 
         protected override ComposeBlueprintContainer CreateBlueprintContainer() => new CatchBlueprintContainer(this);
+
+        [CanBeNull]
+        private PalpableCatchHitObject getPreviousHitObject(double time)
+        {
+            var hitObject = EditorBeatmap.HitObjects.OfType<CatchHitObject>().LastOrDefault(h => h.GetEndTime() < time && !(h is BananaShower));
+
+            switch (hitObject)
+            {
+                case Fruit fruit:
+                    return fruit;
+
+                case JuiceStream juiceStream:
+                    return juiceStream.NestedHitObjects.OfType<PalpableCatchHitObject>().LastOrDefault(h => !(h is TinyDroplet));
+
+                default:
+                    return null;
+            }
+        }
+
+        [CanBeNull]
+        private PalpableCatchHitObject getDistanceSnapGridSourceHitObject()
+        {
+            switch (BlueprintContainer.CurrentTool)
+            {
+                case SelectTool _:
+                    if (EditorBeatmap.SelectedHitObjects.Count == 0)
+                        return null;
+
+                    double minTime = EditorBeatmap.SelectedHitObjects.Min(hitObject => hitObject.StartTime);
+                    return getPreviousHitObject(minTime);
+
+                case FruitCompositionTool _:
+                case JuiceStreamCompositionTool _:
+                    if (!CursorInPlacementArea)
+                        return null;
+
+                    if (EditorBeatmap.PlacementObject.Value is JuiceStream)
+                    {
+                        // Juice stream path is not subject to snapping.
+                        return null;
+                    }
+
+                    double timeAtCursor = ((CatchPlayfield)Playfield).TimeAtScreenSpacePosition(inputManager.CurrentState.Mouse.Position);
+                    return getPreviousHitObject(timeAtCursor);
+
+                default:
+                    return null;
+            }
+        }
+
+        private void updateDistanceSnapGrid()
+        {
+            var sourceHitObject = getDistanceSnapGridSourceHitObject();
+
+            if (distanceSnapToggle.Value != TernaryState.True || sourceHitObject == null)
+            {
+                distanceSnapGrid.Hide();
+            }
+            else
+            {
+                distanceSnapGrid.Show();
+                distanceSnapGrid.StartTime = sourceHitObject.GetEndTime();
+                distanceSnapGrid.StartX = sourceHitObject.EffectiveX;
+            }
+        }
     }
 }