bottomrow= see description
rightcolumn= see description
Clears all non protected cells in an rectangular area with the space character.
This sequence only considers cells protected when in select character protection attribute semantics.
rightcolumn default to their bottom-most/right-most valid values.
rightcolumn this sequence does nothing.
The attributes of the cleared cells are not changed.
If filling the cells splits a multi cell character that character cleared, by replacing it by spaces, keeping its current attributes.
When only some of the lines have set set double width line, the region this sequence acts upon might not look rectangular in to the user on display.