Expose scissor mode, use it in UI

Voile/Source/Rendering/RaylibRenderSystem.cs

@@ -139,6 +139,13 @@ namespace Voile.Rendering
             Raylib.EndBlendMode();
         }
 
+        public override void BeginScissored(Vector2 position, Rect rect)
+        {
+            Raylib.BeginScissorMode((int)position.X, (int)position.Y, (int)rect.Width, (int)rect.Height);
+        }
+
+        public override void EndScissored() => Raylib.EndScissorMode();
+
         public override void BeginCamera2d(Vector2 offset, Vector2 target, float rotation, float zoom)
         {
             var camera = new Camera2D(offset, target, rotation, zoom);

Voile/Source/Rendering/RenderSystem.cs

@@ -125,6 +125,9 @@ namespace Voile.Rendering
         public abstract void BeginBlended(BlendMode blendMode);
         public abstract void EndBlended();
 
+        public abstract void BeginScissored(Vector2 position, Rect rect);
+        public abstract void EndScissored();
+
         /// <summary>
         /// Begins drawing using a 2D camera.
         /// </summary>

Voile/Source/Rendering/StandardRenderSystem.cs

@@ -404,6 +404,16 @@ namespace Voile.Rendering
             throw new NotImplementedException();
         }
 
+        public override void BeginScissored(Vector2 position, Rect rect)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override void EndScissored()
+        {
+            throw new NotImplementedException();
+        }
+
         private Vector2 _windowSize = Vector2.Zero;
         private IWindow? _window;
 

Voile/Source/UI/Containers/Container.cs

@@ -161,6 +161,8 @@ public abstract class Container : UIElement, IParentableElement
 
     protected override void OnRender(RenderSystem renderer, Style style)
     {
+        renderer.BeginScissored(GlobalPosition, LayoutSize);
+
         foreach (var child in Children)
         {
             if (child is not IRenderableElement renderable) continue;
@@ -172,6 +174,8 @@ public abstract class Container : UIElement, IParentableElement
 
             renderable.Render(renderer, childStyle);
         }
+
+        renderer.EndScissored();
     }
 
     private List<UIElement> _children = new();

Voile/Source/UI/UIElement.cs

@@ -109,7 +109,9 @@ public abstract class UIElement : IElement, IRenderableElement, IResizeableEleme
     public void Render(RenderSystem renderer, Style style)
     {
         RenderStyleBox(renderer, style);
+        renderer.BeginScissored(GlobalPosition, LayoutSize);
         OnRender(renderer, style);
+        renderer.EndScissored();
     }
 
     public void DrawSize(RenderSystem renderer)