           menu_driver - command-processing loop of the menu system

## SYNOPSIS

           #include
           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; either the input is a menu navi-
           gation request, it's a printable ASCII character or it  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.
                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 ASCII 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.

           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, a REQ_SCR_ULINE is generated,  if  you
           doubleclick  a  REQ_SCR_UPAGE  is  generated  and  if  you
           tripleclick a REQ_FIRST_ITEM is generated.  If  you  click
           below  the  display region of the menu, a REQ_SCR_DLINE is
           generated, if you doubleclick a REQ_SCR_DPAGE is generated
           and  if  you  tripleclick a REQ_LAST_ITEM is generated. If
           you click at an item inside the display area of the  menu,
           the menu cursor is positioned to that item. If you double-
           click at  an  item  a  REQ_TOGGLE_ITEM  is  generated  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's exactly the pur-
           pose of this return value to signal  that  an  application
           specific command should be executed. 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 couldn't be translated into a menu request  an
           E_REQUEST_DENIED is returned.

           If  the second argument is neither printable ASCII 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.

           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).

## NOTES

           The header file  automatically includes the header
           files .

## 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.