Function charwise_visual_range 

pub fn charwise_visual_range<H: Host>(
    ed: &Editor<View, H>,
    top: (usize, usize),
    bot: (usize, usize),
) -> ((usize, usize), (usize, usize), RangeKind)

The range a charwise Visual selection covers, for a host that runs the Visual operators itself: a selection ending on a line’s NUL takes the line break, as vim’s does. The range a charwise Visual selection top..=bot covers. On an empty line the selection’s one cell is the line break, which vim yanks and changes with it (vy there yanks “\n”); as an exclusive range ending at the next line’s start, reading and cutting agree on that. The buffer’s last line has no break: ropey’s phantom row after a trailing newline is not a line.