Function show 

pub fn show(
    ctx: &Context,
    state: &mut MenuState,
    home: Pos2,
    views: &[(String, bool)],
    enabled: impl Fn(Command) -> bool,
) -> Option<Command>

Draw the menu and return the command picked this frame, if any. views fills the View submenu as (name, is_current); picking the n-th returns Command::OpenView(n). enabled greys out commands that can’t run now. The menu’s top-left starts at home; after that it stays where it’s dragged.