SourceGrid.GridVirtual.GetVisibleRegion C# (CSharp) Method

        private IEnumerable<Range> GetVisibleRegion()
        {
            Range rng;

            rng = RangeAtArea(CellPositionType.FixedTopLeft);
            if (rng.IsEmpty() == false)
                yield return rng;
            rng = RangeAtArea(CellPositionType.FixedTop);
            if (rng.IsEmpty() == false)
                yield return rng;
            rng = RangeAtArea(CellPositionType.FixedLeft);
            if (rng.IsEmpty() == false)
                yield return rng;
            rng = RangeAtArea(CellPositionType.Scrollable);
            if (rng.IsEmpty() == false)
                yield return rng;
        }