Added nullable annotations for DrawEllipse.

src/Avalonia.Visuals/Media/DrawingContext.cs

@@ -202,7 +202,7 @@ namespace Avalonia.Media
         /// The brush and the pen can both be null. If the brush is null, then no fill is performed.
         /// If the pen is null, then no stoke is performed. If both the pen and the brush are null, then the drawing is not visible.
         /// </remarks>
-        public void DrawEllipse(IBrush brush, IPen pen, Point center, double radiusX, double radiusY)
+        public void DrawEllipse(IBrush? brush, IPen? pen, Point center, double radiusX, double radiusY)
         {
             if (brush == null && !PenIsVisible(pen))
             {

src/Avalonia.Visuals/Platform/IDrawingContextImpl.cs

@@ -81,7 +81,7 @@ namespace Avalonia.Platform
         /// The brush and the pen can both be null. If the brush is null, then no fill is performed.
         /// If the pen is null, then no stoke is performed. If both the pen and the brush are null, then the drawing is not visible.
         /// </remarks>
-        void DrawEllipse(IBrush brush, IPen pen, Rect rect);
+        void DrawEllipse(IBrush? brush, IPen? pen, Rect rect);
 
         /// <summary>
         /// Draws text.

src/Avalonia.Visuals/Rendering/SceneGraph/DeferredDrawingContextImpl.cs

@@ -176,7 +176,7 @@ namespace Avalonia.Rendering.SceneGraph
             }
         }
 
-        public void DrawEllipse(IBrush brush, IPen pen, Rect rect)
+        public void DrawEllipse(IBrush? brush, IPen? pen, Rect rect)
         {
             var next = NextDrawAs<EllipseNode>();
 

src/Avalonia.Visuals/Rendering/SceneGraph/EllipseNode.cs

@@ -14,10 +14,10 @@ namespace Avalonia.Rendering.SceneGraph
     {
         public EllipseNode(
             Matrix transform, 
-            IBrush brush, 
-            IPen pen, 
+            IBrush? brush, 
+            IPen? pen, 
             Rect rect, 
-            IDictionary<IVisual, Scene> childScenes = null) 
+            IDictionary<IVisual, Scene>? childScenes = null) 
             : base(rect.Inflate(pen?.Thickness ?? 0), transform)
         {
             Transform = transform;
@@ -30,12 +30,12 @@ namespace Avalonia.Rendering.SceneGraph
         /// <summary>
         /// Gets the fill brush.
         /// </summary>
-        public IBrush Brush { get; }
+        public IBrush? Brush { get; }
 
         /// <summary>
         /// Gets the stroke pen.
         /// </summary>
-        public ImmutablePen Pen { get; }
+        public ImmutablePen? Pen { get; }
 
         /// <summary>
         /// Gets the transform with which the node will be drawn.
@@ -47,9 +47,9 @@ namespace Avalonia.Rendering.SceneGraph
         /// </summary>
         public Rect Rect { get; }
 
-        public override IDictionary<IVisual, Scene> ChildScenes { get; }
+        public override IDictionary<IVisual, Scene>? ChildScenes { get; }
 
-        public bool Equals(Matrix transform, IBrush brush, IPen pen, Rect rect)
+        public bool Equals(Matrix transform, IBrush? brush, IPen? pen, Rect rect)
         {
             return transform == Transform &&
                    Equals(brush, Brush) &&