Function CreateRoundRectRgn 

pub unsafe extern "system" fn CreateRoundRectRgn(
    x1: i32,
    y1: i32,
    x2: i32,
    y2: i32,
    w: i32,
    h: i32,
) -> *mut c_void

#227 CreateRoundRectRgn

allocates storage for the region structure, initializes it to make a roundedcorner rectangular region, and returns a handle to the new region