public void InvalidateBound()
{
AbsoluteBound = new Rectangle (SectionSpan.X, SectionSpan.Y, section.Width, section.Height + SectionheaderHeight + SectionGripperHeight);
GripperAbsoluteBound = new Rectangle (SectionSpan.X, SectionSpan.Y + section.Height + SectionheaderHeight, section.Width, SectionGripperHeight);
HeaderAbsoluteBound = new Rectangle (SectionSpan.X, SectionSpan.Y, section.Width, SectionheaderHeight);
AbsoluteDrawingStartPoint = new Cairo.PointD (AbsoluteBound.X, AbsoluteBound.Y + SectionheaderHeight);
}