private void DrawThumpUpper(SKCanvas canvas, float radius)
{
canvas.Save();
_paint.Style = SKPaintStyle.Fill;
_paint.Shader = SKShader.CreateLinearGradient(new SKPoint(radius.Scale(0.37f), 0),
new SKPoint(-radius.Scale(0.37f), radius.Scale(0.37f)),
BackgroundColor.ThumbGradientColor(IsEnabled).Reverse().ToArray(),
new float[] { 0f, 1f },
SKShaderTileMode.Clamp);
canvas.DrawCircle(0, 0, radius.Scale(0.37f), _paint);
DrawStroke(radius);
canvas.Restore();
}