When re-sizing causes a region to become too narrow for its action bar to be displayed on a single line, the height of the client area is reduced. This occurs because the height of the entire region, including its frame attributes, is not automatically increased to account for the extra line(s) required to display the action bar. In this situation, the "ysize" built-in function returns the height of the client area (in the co-ordinate system of the region's parent) as currently displayed, not as originally specified.