Function heard_from_system 

pub(crate) fn heard_from_system(system_on: bool) -> bool

A change of this device’s own do-not-disturb, heard as it happened (Android’s receiver, Plasma’s Inhibited, GNOME’s switch), whatever caused it: a press of the switch here when it disagrees with what holds (rules::heard), applied, shown and sent at once; nothing when it agrees, which is what Sioul’s own changes look like when they come back (docs/do-not-disturb.md, “Both ways”). Whether it pressed. Any thread.