Function ncplane_hline_interp 

pub unsafe extern "C" fn ncplane_hline_interp(
    n: *mut ncplane,
    c: *const nccell,
    len: c_uint,
    c1: u64,
    c2: u64,
) -> c_int

Draw horizontal or vertical lines using the specified cell, starting at the current cursor position. The cursor will end at the cell following the last cell output (even, perhaps counter-intuitively, when drawing vertical lines), just as if ncplane_putc() was called at that spot. Return the number of cells drawn on success. On error, return the negative number of cells drawn. A length of 0 is an error, resulting in a return of -1.