How does it work to draw empty lines to an visible area of a grid as long as there is still place for it.
You can use your own Stylist connected to FlyGrid.Stylist to draw additional lines (use FlyGrid.Rows.DefaultRowHeight, FlyGrid.LineWidth and FlyGrid.LineColor to draw lines) or override FlyGrid.OnPaint procedure.
In other words how could I get informations about the visible area of a grid.
You can use FlyGrid.ActiveRootPort.GetTotalHeight() method to determine total height of the rows displayed + columns headers height and compare with FlyGrid.ActiveRootPort.Bounds.Height