WIP: UI system, containers and widgets.

Voile/Source/UI/Containers/Container.cs

@@ -0,0 +1,27 @@
+using System.Numerics;
+using Voile.UI.Widgets;
+
+namespace Voile.UI.Containers;
+
+/// <summary>
+/// A base class for all UI containers, used to position and rendering child <see cref="Widget">s.
+/// </summary>
+public abstract class Container : IElement, IParentableElement
+{
+    public IReadOnlyList<IElement> Children => _children;
+    public Vector2 Position { get; set; }
+
+    public Container(List<IElement> children)
+    {
+        _children = children;
+    }
+
+    public abstract void Arrange();
+
+    public void AddChild(IElement child)
+    {
+        _children.Add(child);
+    }
+
+    private List<IElement> _children;
+}