Function handle_focus_lost 

pub fn handle_focus_lost(
    window: &Window,
    state: &BlurDismissState,
    hide_on_blur_pref: bool,
)

WindowEvent::Focused(false) handler: hide window when should_hide_on_blur allows it. hide_on_blur_pref is the caller’s product-owned settings value (not this crate’s concern).