Function sioul_colour_said 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn sioul_colour_said(
    state: i32,
    name: *const c_char,
)

What the screen Sioul’s window is on gets: 0 converted (to the profile name, UTF-8, may be null), 1 by the desktop, 2 nothing (no profile), 3 turned off.

Safety

name is null or a C string.