private void DetermineRange()
{
RectangleD worldRect = Owner.WorldRect;
Rectangle canvasRect = Owner.CanvasRect;
PointF tf = PointD.Truncate(Conversion.ScreenToWorld(new PointD(0.0, 0.0), worldRect, canvasRect));
PointF tf2 = PointD.Ceiling(Conversion.ScreenToWorld(new PointD(AxisRect.Right, 0.0), worldRect, canvasRect));
StartIndex = (int)tf.X;
LastIndex = (int)tf2.X;
}
