# menu_driver

## 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:
    
           •   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).
    
           •   The input is a printable character.  Printable characters
               (which must be positive, less than 256) are checked according
               to the program's locale settings.
    
           •   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:
    
           •   a REQ_SCR_ULINE is generated for a single click,
    
           •   a REQ_SCR_UPAGE is generated for a double-click and
    
           •   a REQ_FIRST_ITEM is generated for a triple-click.
    
           If you click below the display region of the menu:
    
           •   a REQ_SCR_DLINE is generated for a single click,
    
           •   a REQ_SCR_DPAGE is generated for a double-click and
    
           •   a REQ_LAST_ITEM is generated for a triple-click.
    
           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 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.
    
           •   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.
    


## 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 support for mouse
           events is ncurses specific.
    


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