protected override RectangleF ComputeBounds()
RectangleF describing the actual size and position of the whole group in document coordinatesOf course, if Orientation is Horizontal, the width of this group is the sum of the widths of the items, incremented by the Spacing property between the items, and the height is just the maximum height of all of the children. This ignores child objects that are not GoObject.Visible.
When TopIndex is non-negative, this group supports "scrolling". The Bounds is not determined by the size of the child objects, but can be set, possibly resulting in some objects at the start and at the end of the list being made not Visible.