Rebol [Title: "Simple Menu Example"]

view center-face gui: layout/size [

    at 100x100 H3 "You selected:"
    display: field

    ; Here's the menu.  Make sure it goes AFTER other GUI code.
    ; If you put it before other code, the menu will not cover
    ; up other widgets in the GUI.  The menu is basically just
    ; a text-list widget, which is initially hidden off-screen
    ; at position -200x-200.  When an item in the list is 
    ; clicked upon, the action block for the text-list runs
    ; through a conditional switch structure, to decide what to
    ; do for the chosen item.  The code for each option first 
    ; re-hides the menu by repositioning it offscreen (at 
    ; -200x-200 again).  For use in your own programs, you can 
    ; put as many items as you want in the list, and the action 
    ; block for each item can perform any actions you want.
    ; Here, each option just updates the text in the "display"
    ; text entry field, created above.  Change, add to, or 
    ; delete the "item1" "item2" and "quit" elements to suit 
    ; your needs:

    origin 2x2 space 5x5 across
    at -200x-200 file-menu: text-list "item1" "item2" "quit" [
        switch value [
            "item1" [
                face/offset: -200x-200
                show file-menu
                ; PUT YOUR CODE HERE:
                set-face display "File / item1"
            ]
            "item2" [
                face/offset: -200x-200
                show file-menu
                ; PUT YOUR CODE HERE:
                set-face display "File / item2"
            ]
            "quit" [quit]
        ]
    ]

    ; The menu initially just appears as some text choices at 
    ; the top of the GUI.  When the "File" menu is clicked,
    ; the action block of that text widget repositions the 
    ; text-list above, so that it appears directly underneath
    ; the File menu ("face/offset" is the location of the 
    ; currently selected text widget).  It disappears when
    ; clicked again - the code checks to see if the text-list
    ; is positioned beneath the menu.  If so, it repositions
    ; it out of sight.

    at 2x2
    text bold "File" [
        either (face/offset + 0x22) = file-menu/offset [
            file-menu/offset: -200x-200
            show file-menu
        ][
            file-menu/offset: (face/offset + 0x22)
            show file-menu
        ]
    ]

    ; Here's an additional top level menu option.  It provides
    ; just a single choice.  Instead of opening a text-list 
    ; widget with multiple options, it simply ensures that the
    ; other menu is closed (re-hidden), and then runs some code.

    text bold "Help" [
        file-menu/offset: -200x-200
        show file-menu
        ; PUT YOUR CODE HERE:
        set-face display "Help"
    ]
] 400x300