Function ncplane_double_box 

pub fn ncplane_double_box(
    plane: &mut NcPlane,
    stylemask: impl Into<NcStyle_u16>,
    channels: impl Into<NcChannels_u64>,
    end_y: u32,
    end_x: u32,
    boxmask: impl Into<NcBoxMask_u32>,
) -> NcResult_i32

Like ncplane_box with the double box-drawing characters.

Method: NcPlane.double_box().