Open a PopupMenu on the client.
id_return is send in a TEXT_EVENT. id_return should be negative in order to distinguish from
normal widgets.
The Text will be the selected item or ""
Example for text:
menu1,menu2,,menu3
(Two commas means, separator)
Figure 6.27:
Creating a PopupMenu
case RIGHT_MOUSE_EVENT:
pvPopupMenu(p,id_return,"Menu1,Menu2,,Menu3");
break;