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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | EXTENSIONS | PORTABILITY | HISTORY | SEE ALSO | COLOPHON |
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curs_slk(3X) Library calls curs_slk(3X)
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
#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);
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.
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.
Most applications would use slk_noutrefresh because a wrefresh is
likely to follow soon.
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.
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”.
• 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.
• It added const qualifiers to parameters (unnecessarily), and
• 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):
• slk_start has two parameters:
• ng (number of groups) and
• gp (group pointer).
• Soft-key groups are an array of ng integers.
• 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.
• 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.
• 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.
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
curses(3X), curs_attr(3X), curs_initscr(3X), curs_refresh(3X),
curs_variables(3X)
This page is part of the ncurses (new curses) project.
Information about the project can be found at
⟨https://invisible-island.net/ncurses/ncurses.html⟩. If you have a
bug report for this manual page, send it to bug-ncurses@gnu.org.
This page was obtained from the tarball ncurses-6.6.tar.gz fetched
from ⟨https://ftp.gnu.org/gnu/ncurses/⟩ on 2026-01-16. If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for the
page, or you have corrections or improvements to the information
in this COLOPHON (which is not part of the original manual page),
send a mail to man-pages@man7.org
ncurses @NCURSES_MAJOR@.@NCU... 2025-01-18 curs_slk(3X)
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HTML rendering created 2026-01-16 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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