public bool FillY { get; set; } = false;
    public double FillYValue { get; set; } = 0;
    public Color FillYAboveColor { get; set; } = Colors.Blue.WithAlpha(.2);
    public Color FillYBelowColor { get; set; } = Colors.Blue.WithAlpha(.2);
    public Color FillYColor { get => FillYAboveColor; set { FillYAboveColor = value; FillYBelowColor = value; } }

    public virtual void Render(RenderPack rp)
    {
        if (Renderer is not IDataStreamerView viewWithSegs)
        {
            Renderer.Render(rp);
            return;
        }

        var segs = viewWithSegs.GetSegments(rp);
        if (segs.Count == 0)
            return;

        if (FillY)
        {
            float yBasePx = Axes.YAxis.GetPixel(FillYValue + Data.OffsetY, rp.DataRect);

            using SKPaint paint = new();
            foreach (Pixel[] seg in segs)
            {
                using SKPath path = new();
                path.MoveTo(seg[0].X, seg[0].Y);
                for (int i = 1; i < seg.Length; i++)
                    path.LineTo(seg[i].X, seg[i].Y);

                PixelRect rect = new(seg);
                using SKPath fill = new(path);
                fill.LineTo(rect.Right, yBasePx);
                fill.LineTo(rect.Left, yBasePx);

                // above
                if (yBasePx > rect.Top)
                {
                    PixelRect clip = new(rp.DataRect.Left, rp.DataRect.Right, rp.DataRect.Top, yBasePx);
                    FillStyle fs = new() { IsVisible = true, Color = FillYAboveColor };
                    rp.CanvasState.Save();
                    rp.CanvasState.Clip(clip);
                    Drawing.FillPath(rp.Canvas, paint, fill, fs, clip);
                    rp.CanvasState.Restore();
                }

                // below
                if (yBasePx < rect.Bottom)
                {
                    PixelRect clip = new(rp.DataRect.Left, rp.DataRect.Right, yBasePx, rp.DataRect.Bottom);
                    FillStyle fs = new() { IsVisible = true, Color = FillYBelowColor };
                    rp.CanvasState.Save();
                    rp.CanvasState.Clip(clip);
                    Drawing.FillPath(rp.Canvas, paint, fill, fs, clip);
                    rp.CanvasState.Restore();
                }
            }
        }

        Renderer.Render(rp);

        Data.CountTotalOnLastRender = Data.CountTotal;
    }

            Streamer1.FillY = true;
            //Streamer1.FillYColor = Streamer1.Color.WithAlpha(.25);   // or set Above/Below separately
            Streamer1.FillYAboveColor = Colors.BlueViolet;
            Streamer1.FillYBelowColor = Colors.DarkOrange;
            Streamer1.FillYValue = -15;                               // baseline
            Streamer1.ViewWipeRight(0.1);