Menu bars
A Progress window can have one and only one menu bar. The label for each of its menu items and its submenus appears in a line at the top of the window. When the user selects a submenu label, a pull-down menu appears showing the submenu’s items. You can nest submenus within other submenus, in which case the nested submenu is shown to the right of its pull-down menu, as shown in Figure 9–2.
Menus, submenus, and their items form a menu hierarchy. Menus are the parents of their menu items and submenus. Each child submenu can in turn be the parent of menu items and/or other submenus. Your application can define multiple levels of submenus for a window.
Each menu has an OWNER attribute that identifies its owning object. For a menu bar, this is the menu’s window. For a pop-up menu, it is the object the pop-up menu is defined for.
You can use the PARENT, FIRST-CHILD, and NEXT-SIBLING attributes of menus and menu items to traverse the menu hierarchy. There’s an example later in this section that shows how to do this.