Because of what apparently is a gtk+2 bug , we
cannot recreate the submenu every time we need to refresh it,
otherwise the application may get frozen with the keyboard and
mouse grabbed if gtk_menu_item_set_submenu is called while
the menu is displayed. Reusing the same menu every time
works around this issue.
Recreating a menu while it being display, for example clicking View -> Displays before the connection actually gets established and leave it open.
Client may freeze.
Do not recreate entirely a Gtk+ menu, but instead repopulate it.
Client doesn't freeze when refreshing display menu.