protected override Vector2 MeasureOverride(Vector2 availableSize)
        {
            _vScrollBar.Measure(availableSize);
            availableSize.X -= _vScrollBar.DesiredSize.X;

            var constraint = new Vector2(availableSize.X, float.PositiveInfinity);

            var childSize = Vector2.Zero;

            foreach (var child in Children)
            {
                child.Measure(constraint);
                if (child == _vScrollBar)
                {
                    continue;
                }
                childSize = Vector2.ComponentMax(childSize, child.DesiredSize);
            }

            _totalHeight = childSize.Y * _count + ActualSeparation * (_count - 1);

            return(new Vector2(childSize.X, 0f));
        }