void context::cycle_focus()
{
    handler_list::iterator temp_focused_handler = focused_handler;

    for(++temp_focused_handler; temp_focused_handler != focused_handler; ++temp_focused_handler)
        if(temp_focused_handler == handlers.end()) {
            temp_focused_handler = handlers.begin();
        }

        if(temp_focused_handler->requires_event_focus()) {
            focused_handler = temp_focused_handler;
            break;
        }
    }
}