Constant libmpv_sys::mpv_event_id_MPV_EVENT_SHUTDOWN

pub const mpv_event_id_MPV_EVENT_SHUTDOWN: mpv_event_id = 1;

Happens when the player quits. The player enters a state where it tries to disconnect all clients. Most requests to the player will fail, and the client should react to this and quit with mpv_destroy() as soon as possible.