menu_driver(3) | Library calls | menu_driver(3)

# 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(3).
- 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.

# SEE ALSO

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

# 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.

# AUTHORS

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

2023-07-01 | ncurses 6.4