MENUC(1)

MENUC(1) | General Commands Manual | MENUC(1)

# NAME

`menuc` —
menu compiler

# SYNOPSIS

`menuc` | [`-o` name] file

# DESCRIPTION

This implements a curses based menu system. A source file that describes menus, their options, and how to process the options is given to `menuc` and produces both a .c and a .h file that implement the menu system. The standard base name of the files is menu_defs. The `-o` name can be used to specify a different base name.

# MENU DESCRIPTIONS

The input file defines static menus and options for processing those menus. It also contains comments, initial C code that is required to provide for definitions and other code necessary for the menu system, and an option declaration if dynamic menus are requested.

Comments may appear anywhere in the input file and are like a space in the input. They are like C comments starting with `/*` and ending with `*/`. They are unlike C comments in that they may be nested. A comment does not end until a matching end comment is found.

In many places, C code is included in the definition file. All C code is passed verbatim to the C output file. `menuc` comments do not start in C code and comments in the C code are passed verbatim to the output. The C comments are not recognized by `menuc`. In all cases, C code starts with a left brace (‘`{`’) and ends with the matching right brace (‘`}`’). It is important to recognize that in code segments, any brace will be counted, even if it is in a C comment inside the code.

The file contains an initial (and optional) code block followed by any number of menu definition elements in any order. The initial code block usually contains includes of header files used by code in the menu code blocks later in the file. If `USER_MENU_INIT` preprocessor symbol is defined, then it will be evaluated before the rest of the menu is initialised, if it evaluates to a non-zero value then the initialisation will fail. The file is free format, so the actual formatting of the input file is to the taste of the programmer.

All other C code that will appear in an action. This will be specified as ⟨action⟩ in later text. Such an action will appear as:

`action` ⟨opt_endwin⟩ ⟨code⟩

in the file. The ⟨opt_endwin⟩, is optional ‘`(endwin)`’ and specifies that the curses endwin(3) function should be called before executing the code and then reinstating the current curses window after the code has been run. The ⟨code⟩ is as described above.

There are four kinds of menu definition elements. The first one just declares whether the programmer wants dynamic menus, dynamic messages and argument expansion in menus available. All these option default to off (or static only).

Static menus are the ones defined by the menu definitions and do not change at run time. Dynamic menus provide the programmer with a method to create and modify menus during the running of the program. To include dynamic menus, one needs only add the declaration:

`allow dynamic menus;`

The semicolon is required to terminate this declaration. This declaration may appear anywhere in the file, but usually appears before any menus are defined. See below for a detailed explanation of dynamic menus.

To enable internationalization by loading message files at run time one needs to add the declaration:

`allow dynamic messages;`

To allow argument expansion on static menu strings (see below for a detailed explanation), one needs to add the declaration:

`allow expand;`

The next element is a code block to execute if the curses screen can not be successfully initialized. The declaration

`error` `action` ⟨code⟩`;`

tells the menu system to execute the associated code block if the initialization fails. If no code is provided, a default code block is used that prints “Could not initialize curses.” and exits. This element may appear anywhere in the file but usually appears before any menus are defined.

Each menu is built from a list of options. These options include the location of the upper left corner of the menu, whether there is a “box” drawn around the menu, whether the menu is scrollable, the menu's title, whether shortcut letters are allowed, whether a standard exit option should be included in the menu and text associated with the standard exit option.

The `default` declaration defines default options for menus. The general format is:

`default` ⟨comma separated option list⟩`;`

The supported options are:

`y =` starty
  The row number of the upper left corner of the menu window. If starty is negative then the menu will be placed below any message text, but in at least row -starty.
`x =` startx
  The column number of the upper left corner of the menu window. If startx is -1 the menu will be centered horizontally.
`h =` height
  Specifies the number of menu entries to be displayed. If zero, the height will be based on the number of entries.
`w =` width
  Specifies the width of the menu window. If zero, the width will be that of the longest menu text line.
`title` text
  The specified text will be displayed at the top of the menu window (inside any box).
`box`
  If specified, draw a box around the menu.
`clear`
  If specified, clear the window before performing the action.
`exit`
  If specified, add an additional option to exit the menu.
`exitstring` text
  The menu label for the exit option. If not specified defaults to “Exit”.
`default exit`
  If specified, place the cursor on the exit line of the menu, instead of the top line.
`shortcut`
  If specified, add alphabetic tags to each menu line.
`scrollable`
  If specified, and the menu has more lines than will fit in its window, then only part of the menu will be displayed and the ‘`<`’ and ‘`>`’ keys will scroll the displayed menu lines.
`always scroll`
  If specified, allow for the scroll message line even if the menu doesn't appear to have too many lines. Useful for dynamic menus, when the number of entries isn't known when the menu window is created.
`sub menu`
  If specified, the screen contents that the menu window overwrites are saved and restored when the menu exits.
`continuous title`
  If specified there is no vertical space between the title and the menu content.

The `box`, `clear`, `exit`, `default exit`, `shortcut`, `scrollable`, `always scroll`, and `sub menu` options can be preceded by `no` in order to negate a default.

The text arguments can be either a quoted text string or a preprocessor symbol defined to something suitable for initialising a const char * field.

The `default` declaration may appear multiple times. Each time, it sets the default values for menu definitions that follow in the file. In each menu definition, any or all of these default definitions may be overridden for that menu.

The `menu` element is the actual static menu definitions. The format and order for a menu definition is:

    menu
     ⟨name

    ⟩
    ⟨options

    ⟩
    ;

     ⟨expand action

    ⟩

     ⟨display action

    ⟩

     ⟨menu items

    ⟩

     ⟨exit action

    ⟩

     ⟨help text

    ⟩

Menu names are unquoted strings of alpha-numeric and underscore characters. They must start with an alpha character. In C source, a menu named “foo” is appears as `MENU_foo`. (Capitalization is important.) This is important, because the menu is displayed and processed by calling the function

`process_menu(MENU_foo, arg);`

The options are a comma separated list of options as in the `default` declaration. These override the options from the most recent default declaration.

The expand action is optional and only available if the global option `allow expand` has been declared (see above). For an example see below.

The display action is optional and provides C code to execute at each and every time the menu is displayed for processing. If it is included, the format is:

`display ⟨action⟩`;``

The bulk of the menu definition is the specification of the menu items. The general format of a menu item is:

`option ⟨string⟩`,` ⟨element_list⟩`;``

The ⟨string⟩ is the text displayed for the menu item, this must be a quoted string or a preprocessor symbol defined to something that will initialise a const char * field. There may be an arbitrary number of these items. (If there are shortcuts in the menu, a practical limit of 51 should be recognized. It produces shortcuts ‘a’ to ‘w’, ‘y’, ‘z’, and ‘A’ to ‘Z’. ‘x’ is the shortcut for the exit item.)

The ⟨element_list⟩ is a comma separated list of what to do when the item is selected. They may appear in any order.

The first element processed when a menu item is selected is the associated action. The next element to be processed is the `sub` or `next menu` option. They are declared as:

`sub menu ⟨name⟩`
and
`next menu ⟨name⟩`

The difference between these two is that a “sub” menu will return to the current menu when exited. The “next” menu will just replace the current menu and when exited, will return to where the current menu would have gone. Only one of `menu` element may be used for each menu item. Finally, after processing both the action and a sub menu, the current menu will be exited if the element

`exit`

is specified. Note: If `exit` is specified, `next menu` will not work because the menu system will exit the current menu, even if current has been set by `next menu`.

After all menu items, the final two menu definition elements may appear. The ⟨exit action⟩ is optional and provides C code to execute in the process of exiting a menu. If it is included, the format is:

`exit ⟨action⟩`;``

The final part of the menu definition is the optional ⟨help string⟩. The format is:

`help ⟨text⟩`;``

This text is displayed in a full page help window if the question mark is typed. The actual help text starts with a left brace (‘`{`’) and ends with the matching right brace (‘`}`’). The braces are not included in the help string, but all other characters between them are included. Newlines in the code translate to newlines in the help text. Alternatively, the name of a const char * variable may be given.

# DYNAMIC MENUS

If requested, `menuc` supports dynamic menus by allowing the user to create new menus. The related definitions for using dynamic menus are:

    struct menudesc;

    typedef
    struct menu_ent {
            const char  *opt_name;
            int         opt_menu;
            int         opt_flags;
            int         (*opt_action)(struct menudesc *, void *);
    } menu_ent ;

    /* For opt_menu */
    #define OPT_NOMENU 0

    /* For opt_flags */
    #define OPT_SUB     1
    #define OPT_ENDWIN  2
    #define OPT_EXIT    4
    #define OPT_IGNORE  8
    #define OPT_NOSHORT 16

    typedef
    struct menudesc {
            const char  *title;
            int         y, x;
            int         h, w;
            int         mopt;
            int         numopts;
            int         cursel;
            int         topline;
            menu_ent    *opts;
            WINDOW      *mw;
            WINDOW      *sv_mw;
            const char  *helpstr;
            const char  *exitstr;
            void       (*post_act)(struct menudesc *, void *);
            void       (*exit_act)(struct menudesc *, void *);
            void       (*draw_line)(struct menudesc *, int, void *);
    } menudesc ;

    /* defines for mopt field. */
    #define MC_NOEXITOPT 1
    #define MC_NOBOX 2
    #define MC_SCROLL 4
    #define MC_NOSHORTCUT 8
    #define MC_NOCLEAR 16
    #define MC_DFLTEXIT 32
    #define MC_ALWAYS_SCROLL 64
    #define MC_SUBMENU 128
    #define MC_CONTINUOUS 256

    int new_menu(const char *title, menu_ent *opts, int numopts,
            int x, int y, int h, int w, int mopt,
            void (*post_act)(struct menudesc *, void *),
            void (*draw_line)(struct menudesc *, int, void *),
            void (*exit_act)(struct menudesc *, void *),
    	const char *help, const char *exitstr);

    void free_menu (int menu_no);

If `allow expand` has been declared, the menudesc structure contains another member, expand_act:

`void (*expand_act)(struct menudesc *, void *);`

This function (if not null) is called once when initializing a menu, before the display action post_act is called.

The title is the title displayed at the top of the menu. The opts is an array of menu entry definitions that has numopts elements. The programmer must build this array and fill in all of the fields before processing calling `process_menu`() for the new menu. The fields of the opts may change at any time. For example, opt_name may change as a result of selecting that option. When the menu is redisplayed, the new text is printed. Arguments x, y, h, and w are the same as the options in the menu description. mopt is the boolean options. Note, `box`, `clear`, `exit` and `shortcuts` are enabled by default. You need to add option flags to turn them off or turn on scrollable menus. The options post_act, and exit_act are function pointers to the display action and the exit action. If they are null, no call will be made. draw_line will be called to display the menu line if the corresponding opt_name field is null. help is the text to display in a help screen. A null help pointer will disable the help feature for the menu. And finally, exitstr is the text for the exit line of the menu. If it's null, string “Exit” is used.

# MENU ITEM ACTIONS

When creating dynamic menus, the programer supplies function pointers for the menu items `opt_action` member. This functions return one of three possible values:

0
  process sub menu (if set) and continue with the current (or new) menu as usual.
1
  exit the current menu. This is equivalen to specifying “exit” in a non-dynamic menu specification.
-1
  do not handle the current item any further and restart handling the (same) menu. This return value is used when actions modify the menu definition on the fly, e.g. adding or removing additional menu items. The action may set “cursel” to jump to an arbitrary menu item (in the modified menu).

# MENU ITEM EXPANSION

With the `enable expansion` declaration in effect, static menus may be customized before being displayed. This allows parameter substition or special formatting of the menu item strings without having to resort to a full dynamic menu. Expanded strings are stored in the opt_exp_name member of struct menu_ent. This string is prefered over the non-expanded string opt_name when displaying the menu. The expand action code is responsible for filling this pointers. When leaving the menu, all opt_exp_name pointers that are populated will be automatically freed by calling free(3).

A very simple (and nonsensial) example for an expand option would be:

    expand action {
    	int i;
    	for (i = 0; i < menu->numopts; i++) {
    		const char *s = MSG_XLAT(menu->opts[i].opt_name);
    		if (s == NULL)
    			continue;
    		char *t = strdup(s);
    		t[0] = tolower((unsigned char)t[0]);
    		menu->opts[i].opt_exp_name = t;
    	}
    };

which would force the first character of all menu items to lower case. The free(3) call for the strdup(3) call in above code is automatically handled on menu exit.

# ENVIRONMENT

`MENUDEF`
  Can be set to point to a different set of definition files for `menuc`. The current location defaults to /usr/share/misc.

# FILES

- /usr/share/misc/menu_sys.def

# EXAMPLES

The following is a simple menu definition file. It is complete in that the output of `menuc` may be compiled into a complete program. For example, if the following was in a file called example.mc, an executable program could be produced by the following commands.

    menuc -o example example.mc
    cc -o example example.c -lcurses

A much more complete example is available with the source distribution in a subdirectory called testm.

    /* This is an example menu definition file for menuc. */

    {
    #include <stdio.h>
    #include <unistd.h>

    /* Main program! This is often in a different file. */
    int
    main()
      {
        process_menu (MENU_main, NULL);
        endwin();
        return 0;
      }

    /* Example initialize function! */
    void
    init_main()
      {
      }
    }

    default x=20, y=10, box, scrollable, exit;

    error action {
       fprintf (stderr, "Example Menu: Could not initialize curses.");
       exit(1);
    };

    menu main, title "Main Menu", no exit, no shortcut;
       display action { init_main(); };
       option "Option 1",
          action (endwin) {
            printf ("That was option 1!");
            sleep(3);
          };
       option "Sub Menu", sub menu othermenu;
       option "Next Menu", next menu othermenu;
       option "Quit", exit;
       help {
    This is a simple help screen for an example menu definition file.
    };

    menu othermenu, title "Sub/Next Menu", x=5, y=5, no box;
       option "Do Nothing!", action { };

# SEE ALSO

msgc(1)

# AUTHORS

Philip A. Nelson for Piermont Information Systems Inc. Initial ideas for this were developed and implemented in Pascal at the Leiden University, Netherlands, in the summer of 1980.

# BUGS

Both `menuc` and `msgc` are probably only used by `sysinst`. The features of both have been tailored for `sysinst`, and further changes are likely to occur.

February 25, 2019 | NetBSD 9.4