Function ncplane_rounded_box_sized 

pub fn ncplane_rounded_box_sized(
    plane: &mut ncplane,
    stylemask: impl Into<u16>,
    channels: impl Into<u64>,
    len_y: u32,
    len_x: u32,
    boxmask: impl Into<u32>,
) -> i32

Like ncplane_box_sized with the rounded box-drawing characters.

Method: NcPlane.rounded_box_sized().