Understanding ring menus

The MENU instruction implements a set of choices, also known as action handlers.

A MENU dialog defines a list of options that can trigger actions to execute associated program code. Ring menus are implemented with the MENU interactive instruction.

A MENU block lists the possible actions that can be triggered in a given place in the program, with the associated program code to be executed.

MENU "Sample"
    COMMAND "Say hello"
       DISPLAY "Hello, world!"
    COMMAND "Exit"
       EXIT MENU 
END MENU

A ring menu can only define a set of options for a given level of the program. You cannot define all menu options of your program in a single MENU instruction; you must implement nested menus.

The MENU instruction is mainly designed for text mode applications, displaying ring menus at the top of the screen. A typical TUI mode application starts with a global menu, defining general options to access subroutines, which in turn implement specific menus with database record handling options such as 'Append', 'Delete', 'Modify', and 'Search'.

Ring menus can also be used in a GUI application. However, as this instruction does not handle form fields, other parts of the form are disabled during the menu dialog execution. In GUI applications, ring menus are typically used to open a modal window with Yes / No / Cancel options, where options are typically defined with the ON ACTION clauses, to keep the code abstract and define decoration in form or with attributes:

MENU ""
    ON ACTION print ATTRIBUTES(TEXT=%"print",IMAGE="printer")
       CALL print_document()
    ON ACTION save -- Get decoration from form or action defaults 
       CALL save_document()
    ON ACTION close -- Binds to GUI window close button
       EXIT PROGRAM
END MENU