Function act 

fn act(
    action: &str,
    window: Option<(&CxxQtThread<Sioul>, &Arc<Shared>)>,
) -> bool

A button pressed, “pause”, “resume” or “stop”: with the window, as its own buttons (work::focus_pause, work::focus_stop); without, on the session’s file. A button a moment behind (another device paused the session meanwhile) changes nothing: “pause” pauses only what runs, “resume” goes on only with what is paused. Returns whether it changed.