pub fn menu_custom_button<R>(
    ui: &mut Ui,
    button: Button<'_>,
    add_contents: impl FnOnce(&mut Ui) -> R,
) -> InnerResponse<Option<R>>👎Deprecated: Use 
egui::containers::menu insteadExpand description
Construct a top level menu with a custom button in a menu bar.
Responds to primary clicks.
Returns None if the menu is not open.