void OnCanvasViewPaintSurface(object sender, SKPaintSurfaceEventArgs args)
        {
            SKImageInfo info = args.Info;
            SKSurface surface = args.Surface;
            SKCanvas canvas = surface.Canvas;

            canvas.Clear();

            SKPaint paint = new SKPaint
            {
                Style = SKPaintStyle.Stroke,
                Color = Color.Red.ToSKColor(),
                StrokeWidth = 25
            };
            paint.Style = SKPaintStyle.Fill;
            paint.Color = SKColors.Blue;
            canvas.DrawCircle(args.Info.Width / 2, args.Info.Height / 2, 100, paint);
        }