Function gdk_cursor_new_from_callback 

pub unsafe extern "C" fn gdk_cursor_new_from_callback(
    callback: GdkCursorGetTextureCallback,
    data: gpointer,
    destroy: GDestroyNotify,
    fallback: *mut GdkCursor,
) -> *mut GdkCursor

Available on crate feature v4_16 only.