Fix menus appearing out of window

I don't know if this is the right way to fix this, but when I updated to the current Flame from v0.2.1, my menus and submenus weren't being constrained to appear within the window any more. _layoutRelativeTo() is called above in this._super(..), but the layout width isn't set at that time.
I can set an explicit width for my menu, causing it to appear, but I don't see how to set an explicit width for submenus. If there's a better way to fix this, please let me know.  Thanks!