# menu_driver 3x 2024-03-16 ncurses 6.5 Library calls

    menu_driver(3x)                  Library calls                 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(3x).

           o   The input is a printable character.   Printable  characters  (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 decoration 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  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 is exactly the purpose of this return value
               to signal 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(3)).

           E_BAD_ARGUMENT
                Routine detected an incorrect or out-of-range argument.

           E_BAD_STATE
                Routine was called from an initialization or termination 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.

## PORTABILITY

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

## AUTHORS

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

## SEE ALSO

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

    ncurses 6.5                       2024-03-16                   menu_driver(3x)