# curs_slk 3x 2025-01-18 ncurses 6.5 Library calls

    curs_slk(3x)                     Library calls                    curs_slk(3x)

## NAME

           slk_init,  slk_set,  slk_wset, slk_refresh, slk_noutrefresh, slk_label,
           slk_clear,    slk_restore,    slk_touch,    slk_attron,    slk_attrset,
           slk_attroff,   slk_attr_on,   slk_attr_set,   slk_attr_off,   slk_attr,
           slk_color, extended_slk_color - curses soft label key routines

## SYNOPSIS

           #include <curses.h>

           int slk_init(int fmt);

           int slk_set(int labnum, const char *label, int align);
           int slk_wset(int labnum, const wchar_t *label, int align);

           char *slk_label(int labnum);

           int slk_refresh(void);
           int slk_noutrefresh(void);
           int slk_clear(void);
           int slk_restore(void);
           int slk_touch(void);

           int slk_attron(const chtype attrs);
           int slk_attroff(const chtype attrs);
           int slk_attrset(const chtype attrs);
           int slk_attr_on(attr_t attrs, void *opts);
           int slk_attr_off(const attr_t attrs, void *opts);
           int slk_attr_set(const attr_t attrs, short pair, void*opts);
           /* extension */
           attr_t slk_attr(void);

           int slk_color(short pair);
           /* extension */
           int extended_slk_color(int pair);

## DESCRIPTION

           These functions manipulate the  soft  function  key  labels  that  some
           hardware  terminals support.  For those terminals that do not have soft
           labels, curses takes over the  bottom  line  of  stdscr,  reducing  its
           vertical  size  and the value of LINES by one.  By default, curses uses
           eight labels of up to eight characters each.

           ncurses furthermore supports a mode comprising twelve labels of  up  to
           five  characters  each,  following a convention associated with the IBM
           PC/AT keyboard.  ncurses simulates this mode by taking over up  to  two
           lines  at the bottom of the screen; it does not try to use any hardware
           support for this mode.

### Initialization

           slk_init  must  be  called  before  initscr  or  newterm.   If  initscr
           eventually uses a line from stdscr to emulate the soft labels, then fmt
           determines how the labels are arranged on the screen.

           0  indicates a 3-2-3 arrangement of the labels.

           1  indicates a 4-4 arrangement

           2  indicates the PC-like 4-4-4 mode.

           3  is again the PC-like 4-4-4 mode, but in addition an  index  line  is
              generated,  helping  the  user  to  associate  each  label  with its
              numbered function key.  LINES and the vertical size  of  stdscr  are
              further reduced.

### Labels

           Populate  the  labels  with  normal strings (slk_set) or wide-character
           strings (slk_wset).  Each function takes three parameters.

           labnum  is the label number, from 1 to 8 (12 if fmt in slk_init is 2 or
                   3);

           label   is  be the string to put on the label, up to eight (five if fmt
                   in slk_init is 2 or 3) characters in length.  A empty string or
                   a null pointer sets up a blank label.

           align   is  0,  1,  or 2, aligning label to the left, center, or right,
                   respectively, within the 8 (5) character cells housing it.

           slk_label obtains the string assigned to label number labnum, with  any
           leading and trailing blanks stripped.

### Screen Updates

           slk_refresh  and  slk_noutrefresh  affect  the  soft key label lines as
           wrefresh and wnoutrefresh do the curses window.

           The slk_clear routine clears the soft labels from the screen.

           The slk_restore routine restores the soft labels to the screen after  a
           slk_clear has been performed.

           The  slk_touch routine forces all the soft labels to be output the next
           time a slk_noutrefresh is performed.

### Video Attributes

           The  slk_attron,  slk_attrset,  slk_attroff,  and   slk_attr   routines
           correspond  to  attron,  attrset,  attroff, and attr_get, respectively.
           They have an effect only if soft labels are  simulated  on  the  bottom
           line  of  the  screen.   The  default  highlight for soft key labels is
           A_STANDOUT (as in System V curses, which does not document this fact).

### Colors

           The slk_color routine corresponds to color_set.  It has an effect  only
           if soft labels are simulated on the bottom line of the screen.

           Because  slk_color  accepts  only short (signed 16-bit integer) values,
           this implementation provides extended_slk_color, which accepts  an  int
           value of at least 32 bits.

## RETURN VALUE

           Functions  that  return  integers  return  ERR upon failure and OK upon
           success.

           In ncurses,

              slk_attr
                   returns the attribute used for the soft keys.

              slk_attroff, slk_attron,  slk_clear,  slk_noutrefresh,  slk_refresh,
              slk_touch
                   return   ERR   if   the  terminal  or  the  softkeys  were  not
                   initialized.

              slk_attrset
                   returns  ERR  if  the  terminal  or  the  softkeys   were   not
                   initialized.

              slk_attr_set
                   returns   ERR   if  the  terminal  or  the  softkeys  were  not
                   initialized,  or  the  color  pair   is   outside   the   range
                   0..COLOR_PAIRS-1.

              slk_color
                   returns   ERR   if  the  terminal  or  the  softkeys  were  not
                   initialized,  or  the  color  pair   is   outside   the   range
                   0..COLOR_PAIRS-1.

              slk_init
                   returns ERR if the format parameter is outside the range 0..3.

              slk_label
                   returns NULL on error.

              slk_set
                   returns   ERR   if  the  terminal  or  the  softkeys  were  not
                   initialized, or the labnum parameter is outside  the  range  of
                   label  counts,  or if the format parameter is outside the range
                   0..2, or if memory for the labels cannot be allocated.

## NOTES

           Most applications would  use  slk_noutrefresh  because  a  wrefresh  is
           likely to follow soon.

## EXTENSIONS

           X/Open  Curses  documents the opts argument as reserved for future use,
           saying that it must be a null pointer.  The ncurses 6 ABI uses  it  for
           the  functions  that  accept a color pair parameter to support extended
           color pairs.

           For functions which modify the color, e.g., slk_attr_set,  if  opts  is
           set  it  is treated as a pointer to int, and used to set the color pair
           instead of the short pair parameter.

## PORTABILITY

           X/Open Curses Issue 4 describes these functions.  It specifies no error
           conditions for them.

           SVr4  describes  a  successful  return  value only as "an integer value
           other than ERR".

           o   X/Open  added  functions  like  the   SVr4   attribute-manipulation
               functions  slk_attron,  slk_attroff, and slk_attrset, but which use
               attr_t parameters (rather than chtype), along with a reserved  opts
               parameter.

               Two  of  these  new  functions  (unlike the SVr4 functions) have no
               provision for color: slk_attr_on and slk_attr_off.

               The third function (slk_attr_set) has a color pair parameter.

           o   It added const qualifiers to parameters (unnecessarily), and

           o   It added slk_color.

           Although slk_start is declared in the curses header file,  it  was  not
           documented by SVr4 other than its presence in a list of libtermlib.so.1
           symbols.  Reading the source code (i.e., Illumos):

           o   slk_start has two parameters:

               o   ng (number of groups) and

               o   gp (group pointer).

           o   Soft-key groups are an array of ng integers.

           o   In SVr4, slk_init calls slk_start passing a null for gp.  For  this
               case,  slk_start  uses  the  number  of  groups ng (3 for the 3-2-3
               layout, 2 for the 4-4 layout) which slk_init provided.

               If ng is  neither  2  or  3,  slk_start  checks  the  terminfo  fln
               (label_format)  capability,  interpreting that as a comma-separated
               list of numbers, e.g., "3,2,3" for the 3-2-3 layout.

               Finally, if there is no fln capability, slk_start returns ERR.

           o   If slk_start is given a non-null gp, it copies the ng  elements  of
               the group of soft-keys, up to 16.

               If there are more than 16 elements, slk_start returns ERR.

           o   The  format  codes  2  and  3 for slk_init were added by ncurses in
               1996.  PDCurses 2.4 added this feature in 2001.

           The function slk_attr was added by ncurses in 1996.

           X/Open Curses does not specify a limit for the  number  of  colors  and
           color pairs which a terminal can support.  However, in its use of short
           for the parameters, it carries over SVr4's  implementation  detail  for
           the compiled terminfo database, which uses signed 16-bit numbers.  This
           implementation provides extended versions of those functions which  use
           int  parameters,  allowing  applications to use larger color- and pair-
           numbers.

## HISTORY

           SVr3 introduced these functions:
             slk_clear
             slk_init
             slk_label
             slk_noutrefresh
             slk_refresh
             slk_restore
             slk_set
             slk_touch

           SVr4 added these functions:
             slk_attroff
             slk_attron
             slk_attrset
             slk_start

           X/Open Curses added these:
             slk_attr_off
             slk_attr_on
             slk_attr_set
             slk_color
             slk_wset

## SEE ALSO

           curses(3x),    curs_attr(3x),    curs_initscr(3x),    curs_refresh(3x),
           curs_variables(3x)

    ncurses 6.5                       2025-01-18                      curs_slk(3x)