WIP: GridSet, add Vector2.Snapped extension method.

Voile/Source/Extensions/Vector2Extensions.cs

@@ -8,5 +8,31 @@ namespace Voile.Extensions
         {
             return new Vector2((float)MathUtils.Lerp(a.X, b.X, t), (float)MathUtils.Lerp(a.Y, b.Y, t));
         }
+
+        public static Vector2 Snapped(this Vector2 a, Vector2 snap)
+        {
+            var x = a.X % snap.X;
+            var y = a.Y % snap.Y;
+
+            if (x == 0)
+            {
+                x = a.X;
+            }
+            else
+            {
+                x = a.X - x;
+            }
+
+            if (y == 0)
+            {
+                y = a.Y;
+            }
+            else
+            {
+                y = a.Y - y;
+            }
+
+            return new Vector2(x, y);
+        }
     }
 }

Voile/Source/UI/UISystem.cs

@@ -31,7 +31,11 @@ public class UISystem : IUpdatableSystem, IRenderableSystem
         _elements = elements;
     }
 
-    public void AddElement(UIElement element) => _elements.Add(element);
+    public void AddElement(UIElement element)
+    {
+        _elements.Add(element);
+        _inputElementIndices.Add(element.GlobalPosition, _elements.Count - 1);
+    }
     public void RemoveElement(UIElement element) => _elements.Remove(element);
 
     public void Update(double deltaTime)
@@ -167,5 +171,7 @@ public class UISystem : IUpdatableSystem, IRenderableSystem
     private List<UIElement> _elements = new();
     private InputSystem _input;
 
+    private GridSet<int> _inputElementIndices = new();
+
     private Vector2 _lastMousePosition = Vector2.Zero;
 }