# curs_slk 3x 2023-10-07 ncurses 6.4 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 fmt);
           int slk_wset(int labnum, const wchar_t *label, int fmt);

           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

           The slk* functions manipulate the set of soft function-key labels  that
           exist  on  many  terminals.   For those terminals that do not have soft
           labels, curses takes over the bottom line of stdscr, reducing the  size
           of  stdscr and the variable LINES.  curses standardizes on eight labels
           of up to eight characters each.   In  addition  to  this,  the  ncurses
           implementation  supports  a  mode where it simulates 12 labels of up to
           five characters each.  This is  useful  for  PC-like  enduser  devices.
           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

           The  slk_init  routine  must  be  called  before  initscr or newterm is
           called.  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 identify the key numbers easily.

### Labels

           The  slk_set  routine  (and the slk_wset routine for the wide-character
           library) has 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 null string  or
                   a null pointer sets up a blank label.

              fmt  is  either  0,  1,  or 2, indicating whether the label is to be
                   left-justified,  centered,  or  right-justified,  respectively,
                   within the label.

           The  slk_label  routine  returns  the  current  label  for label number
           labnum, with leading and trailing blanks stripped.

### Screen updates

           The slk_refresh and slk_noutrefresh routines correspond to the wrefresh
           and wnoutrefresh routines.

           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 keys 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
           integer value, e.g., 32-bits.

## RETURN VALUE

           These routines return ERR upon failure and OK (SVr4 specifies only  "an
           integer value other than ERR") upon successful completion.

           X/Open defines no error conditions.  In this implementation

              slk_attr
                   returns the attribute used for the soft keys.

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

              slk_attrset
                   returns  an  error  if  the  terminal  or the softkeys were not
                   initialized.

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

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

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

              slk_label
                   returns NULL on error.

              slk_set
                   returns  an  error  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.

## 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

## EXTENSIONS

           X/Open curses documents the opts argument as reserved for  future  use,
           saying  that  it must be null.  This implementation uses that parameter
           in ABI 6 for the functions which have 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.

## NOTES

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

## PORTABILITY

           The XSI curses standard, Issue 4,  described  the  soft-key  functions,
           with some differences from SVr4 curses:

           o   It  added  functions like the SVr4 attribute-manipulation functions
               slk_attron,  slk_attroff,  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 an error.

           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.

## SEE ALSO

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

    ncurses 6.4                       2023-10-07                      curs_slk(3x)