SFLROLVAL is not implemented in general. However, some DDS programmers
purposefully set the SFLROLVAL field to 0 or negative so that the Page Up and
Page Down keys can be disabled (an error is issued when they are used), and they
can define their own function keys to control the paging. In this case, they
normally do not show the SFLROLVAL field. We check if the SFLROLVAL is invalid
(0 or negative) and the SFLROLVAL field has display attribute non-display
conditioned on. In this case we do not display the scrollbar.