Function ncplane_format 

pub unsafe extern "C" fn ncplane_format(
    n: *mut ncplane,
    y: c_int,
    x: c_int,
    ylen: c_uint,
    xlen: c_uint,
    stylemask: u16,
) -> c_int

Set the given style throughout the specified region, keeping content and channels unchanged. The upper left corner is at ‘y’, ‘x’, and -1 may be specified to indicate the cursor’s position in that dimension. The area is specified by ‘ylen’, ‘xlen’, and 0 may be specified to indicate everything remaining to the right and below, respectively. It is an error for any coordinate to be outside the plane. Returns the number of cells set, or -1 on failure.