# menu_driver 3x

    menu_driver(3x)                                         menu_driver(3x)

## NAME

           menu_driver - command-processing loop of the menu system

## SYNOPSIS

           #include <menu.h>
           int menu_driver(MENU *menu, int c);

## DESCRIPTION

           Once a menu has been posted (displayed), you should funnel
           input events to it through menu_driver.  This routine  has
           three major input cases:

           o   The  input  is  a form navigation request.  Navigation
               request codes are constants defined in <form.h>, which
               are   distinct  from  the  key-  and  character  codes
               returned by wgetch.

           o   The input is a printable character.  Printable charac-
               ters  (which  must  be  positive,  less  than 256) are
               checked according to the program's locale settings.

           o   The input is the KEY_MOUSE special key associated with
               an mouse event.

           The menu driver requests are as follows:

           REQ_LEFT_ITEM
                Move left to an item.

           REQ_RIGHT_ITEM
                Move right to an item.

           REQ_UP_ITEM
                Move up to an item.

           REQ_DOWN_ITEM
                Move down to an item.

           REQ_SCR_ULINE
                Scroll up a line.

           REQ_SCR_DLINE
                Scroll down a line.

           REQ_SCR_DPAGE
                Scroll down a page.

           REQ_SCR_UPAGE
                Scroll up a page.

           REQ_FIRST_ITEM
                Move to the first item.

           REQ_LAST_ITEM
                Move to the last item.

           REQ_NEXT_ITEM
                Move to the next item.

           REQ_PREV_ITEM
                Move to the previous item.

           REQ_TOGGLE_ITEM
                Select/deselect an item.

           REQ_CLEAR_PATTERN
                Clear the menu pattern buffer.

           REQ_BACK_PATTERN
                Delete   the  previous  character  from  the  pattern
                buffer.

           REQ_NEXT_MATCH
                Move to the next item matching the pattern match.

           REQ_PREV_MATCH
                Move to the previous item matching the pattern match.

           If  the second argument is a printable character, the code
           appends it to the pattern buffer and attempts to  move  to
           the  next  item  matching the new pattern.  If there is no
           such match, menu_driver returns E_NO_MATCH and deletes the
           appended character from the buffer.

           If  the  second  argument  is one of the above pre-defined
           requests, the corresponding action is performed.

       MOUSE HANDLING
           If the second argument is the KEY_MOUSE special  key,  the
           associated mouse event is translated into one of the above
           pre-defined requests.  Currently only clicks in  the  user
           window  (e.g., inside the menu display area or the decora-
           tion window) are handled.

           If you click above the display region of the menu:

           o   a REQ_SCR_ULINE is generated for a single click,

           o   a REQ_SCR_UPAGE is generated for a double-click and

           o   a REQ_FIRST_ITEM is generated for a triple-click.

           If you click below the display region of the menu:

           o   a REQ_SCR_DLINE is generated for a single click,

           o   a REQ_SCR_DPAGE is generated for a double-click and

           o   a REQ_LAST_ITEM is generated for a triple-click.

           If you click at an item inside the  display  area  of  the
           menu:

           o   the menu cursor is positioned to that item.

           o   If  you double-click an item a REQ_TOGGLE_ITEM is gen-
               erated and E_UNKNOWN_COMMAND is returned.  This return
               value  makes  sense,  because  a  double click usually
               means that an item-specific action should be returned.
               It is exactly the purpose of this return value to sig-
               nal that an application  specific  command  should  be
               executed.

           o   If  a translation into a request was done, menu_driver
               returns the result of this request.

           If you clicked outside the user window or the mouse  event
           could   not   be   translated   into  a  menu  request  an
           E_REQUEST_DENIED is returned.

       APPLICATION-DEFINED COMMANDS
           If the second argument is neither printable nor one of the
           above  pre-defined  menu  requests or KEY_MOUSE, the drive
           assumes it is an application-specific command and  returns
           E_UNKNOWN_COMMAND.  Application-defined commands should be
           defined relative to  MAX_COMMAND,  the  maximum  value  of
           these pre-defined requests.

## RETURN VALUE

           menu_driver return one of the following error codes:

           E_OK The routine succeeded.

           E_SYSTEM_ERROR
                System error occurred (see errno).

           E_BAD_ARGUMENT
                Routine  detected  an incorrect or out-of-range argu-
                ment.

           E_BAD_STATE
                Routine was called from an initialization or termina-
                tion function.

           E_NOT_POSTED
                The menu has not been posted.

           E_UNKNOWN_COMMAND
                The menu driver code saw an unknown request code.

           E_NO_MATCH
                Character failed to match.

           E_REQUEST_DENIED
                The menu driver could not process the request.

## SEE ALSO

           curses(3x), menu(3x), getch(3x).

## NOTES

           The header file <menu.h> automatically includes the header
           files <curses.h>.

## PORTABILITY

           These routines emulate the System V  menu  library.   They
           were  not supported on Version 7 or BSD versions. The sup-
           port for mouse events is ncurses specific.

## AUTHORS

           Juergen Pfeifer.  Manual  pages  and  adaptation  for  new
           curses by Eric S. Raymond.

                                                            menu_driver(3x)