Function ncplane_pixel_geom 

pub unsafe extern "C" fn ncplane_pixel_geom(
    n: *const ncplane,
    pxy: *mut c_uint,
    pxx: *mut c_uint,
    celldimy: *mut c_uint,
    celldimx: *mut c_uint,
    maxbmapy: *mut c_uint,
    maxbmapx: *mut c_uint,
)

Retrieve pixel geometry for the display region (‘pxy’, ‘pxx’), each cell (‘celldimy’, ‘celldimx’), and the maximum displayable bitmap (‘maxbmapy’, ‘maxbmapx’). If bitmaps are not supported, or if there is no artificial limit on bitmap size, ‘maxbmapy’ and ‘maxbmapx’ will be 0. Any of the geometry arguments may be NULL.