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.\" $Id: curs_slk.3,v 1.11 2023/10/17 09:52:08 nicm Exp $
.TH curs_slk 3 2023-07-01 "ncurses 6.4" "Library calls"
.ie \n(.g .ds `` \(lq
.el       .ds `` ``
.ie \n(.g .ds '' \(rq
.el       .ds '' ''
.de bP
.ie n  .IP \(bu 4
.el    .IP \(bu 2
..
.na
.hy 0
.SH NAME
\fBslk_init\fP,
\fBslk_set\fP,
\fBslk_wset\fP,
\fBslk_refresh\fP,
\fBslk_noutrefresh\fP,
\fBslk_label\fP,
\fBslk_clear\fP,
\fBslk_restore\fP,
\fBslk_touch\fP,
\fBslk_attron\fP,
\fBslk_attrset\fP,
\fBslk_attroff\fP,
\fBslk_attr_on\fP,
\fBslk_attr_set\fP,
\fBslk_attr_off\fP,
\fBslk_attr\fP,
\fBslk_color\fP,
\fBextended_slk_color\fP \- \fBcurses\fP soft label routines
.ad
.hy
.SH SYNOPSIS
\fB#include <curses.h>\fP
.sp
\fBint slk_init(int \fIfmt\fB);\fR
.sp
\fBint slk_set(int \fIlabnum\fB, const char *\fIlabel\fB, int \fIfmt\fB);\fR
.br
\fBint slk_wset(int \fIlabnum\fB, const wchar_t *\fIlabel\fB, int \fIfmt\fB);\fR
.sp
\fBchar *slk_label(int \fIlabnum\fB);\fR
.sp
\fBint slk_refresh(void);\fP
.br
\fBint slk_noutrefresh(void);\fP
.br
\fBint slk_clear(void);\fP
.br
\fBint slk_restore(void);\fP
.br
\fBint slk_touch(void);\fP
.sp
\fBint slk_attron(const chtype \fIattrs\fB);\fR
.br
\fBint slk_attroff(const chtype \fIattrs\fB);\fR
.br
\fBint slk_attrset(const chtype \fIattrs\fB);\fR
.br
\fBint slk_attr_on(attr_t \fIattrs\fB, void* \fIopts\fB);\fR
.br
\fBint slk_attr_off(const attr_t \fIattrs\fB, void * \fIopts\fB);\fR
.br
\fBint slk_attr_set(const attr_t \fIattrs\fB, short \fIpair\fB, void* \fIopts\fB);\fR
.br
/* extension */
.br
\fBattr_t slk_attr(void);\fP
.sp
\fBint slk_color(short \fIpair\fB);\fR
.br
/* extension */
.br
\fBint extended_slk_color(int \fIpair\fB);\fR
.SH 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,
\fBcurses\fP takes over the bottom line of \fBstdscr\fP, reducing the size of
\fBstdscr\fP and the variable \fBLINES\fP.
\fBcurses\fP 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.
.SS Initialization
The \fBslk_init\fP routine must be called before \fBinitscr\fP or \fBnewterm\fP
is called.
If \fBinitscr\fP eventually uses a line from \fBstdscr\fP to
emulate the soft labels,
then \fIfmt\fP determines how the labels are arranged on the screen:
.RS 3
.TP 3
.B 0
indicates a 3\-2\-3 arrangement of
the labels.
.TP 3
.B 1
indicates a 4\-4 arrangement
.TP 3
.B 2
indicates the PC-like 4\-4\-4 mode.
.TP 3
.B 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.
.RE
.SS Labels
The \fBslk_set\fP routine
(and the \fBslk_wset\fP routine for the wide-character library)
has three parameters:
.RS 3
.TP 5
.I labnum
is the label number, from \fB1\fP to \fB8\fP
(12 if \fIfmt\fP in \fBslk_init\fP is \fB2\fP or \fB3\fP);
.TP
.I label
is be the string to put on the label,
up to eight
(five if \fIfmt\fP in \fBslk_init\fP is \fB2\fP or \fB3\fP)
characters in length.
A null string or a null pointer sets up a blank label.
.TP
.I fmt
is either
\fB0\fP, \fB1\fP, or \fB2\fP, indicating whether the label is to be
left-justified, centered, or right-justified, respectively, within the
label.
.RE
.PP
The \fBslk_label\fP routine returns the current label for label number
\fIlabnum\fP, with leading and trailing blanks stripped.
.SS Screen updates
The \fBslk_refresh\fP and \fBslk_noutrefresh\fP routines correspond to
the \fBwrefresh\fP and \fBwnoutrefresh\fP routines.
.PP
The \fBslk_clear\fP routine clears the soft labels from the screen.
.PP
The \fBslk_restore\fP routine restores the soft labels to the screen
after a \fBslk_clear\fP has been performed.
.PP
The \fBslk_touch\fP routine forces all the soft labels to be output
the next time a \fBslk_noutrefresh\fP is performed.
.SS Video attributes
The
\fBslk_attron\fP, \fBslk_attrset\fP, \fBslk_attroff\fP and \fBslk_attr\fP
routines correspond to
\fBattron\fP, \fBattrset\fP, \fBattroff\fP and \fBattr_get\fP, 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).
.SS Colors
The \fBslk_color\fP routine corresponds to \fBcolor_set\fP.
It has an effect only
if soft labels are simulated on the bottom line of the screen.
.PP
Because \fBslk_color\fP accepts only \fBshort\fP (signed 16-bit integer) values,
this implementation provides
\fBextended_slk_color\fP which accepts an integer value, e.g., 32-bits.
.
.SH RETURN VALUE
These routines return \fBERR\fP upon failure
and \fBOK\fP (SVr4 specifies only "an integer value other than \fBERR\fP")
upon successful completion.
.PP
X/Open defines no error conditions.
In this implementation
.RS 3
.TP 5
\fBslk_attr\fP
returns the attribute used for the soft keys.
.TP 5
.na
.hy 0
\fBslk_attroff\fP, \fBslk_attron\fP, \fBslk_clear\fP, \fBslk_noutrefresh\fP, \fBslk_refresh\fP, \fBslk_touch\fP
.ad
.hy
return an error
if the terminal or the softkeys were not initialized.
.TP 5
\fBslk_attrset\fP
returns an error
if the terminal or the softkeys were not initialized.
.TP 5
\fBslk_attr_set\fP
returns an error
if the terminal or the softkeys were not initialized, or
the color pair is outside the range 0..COLOR_PAIRS\-1.
.TP 5
\fBslk_color\fP
returns an error
if the terminal or the softkeys were not initialized, or
the color pair is outside the range 0..COLOR_PAIRS\-1.
.TP 5
\fBslk_init\fP
returns an error
if the format parameter is outside the range 0..3.
.TP 5
\fBslk_label\fP
returns \fBNULL\fP on error.
.TP 5
\fBslk_set\fP
returns an error
if the terminal or the softkeys were not initialized, or
the \fIlabnum\fP 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.
.RE
.SH HISTORY
SVr3 introduced these functions:
  slk_clear
  slk_init
  slk_label
  slk_noutrefresh
  slk_refresh
  slk_restore
  slk_set
  slk_touch
.PP
SVr4 added these functions:
  slk_attroff
  slk_attron
  slk_attrset
  slk_start
.PP
X/Open Curses added these:
  slk_attr_off
  slk_attr_on
  slk_attr_set
  slk_color
  slk_wset
.SH EXTENSIONS
X/Open Curses documents the \fIopts\fP 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.
.PP
For  functions  which modify the color, e.g., \fBslk_attr_set\fP,
if \fIopts\fP is set it is treated as a pointer to \fBint\fP,
and used to  set  the  color pair instead of the \fBshort\fP pair parameter.
.SH NOTES
Most applications would use \fBslk_noutrefresh\fP because a
\fBwrefresh\fP is likely to follow soon.
.SH PORTABILITY
The XSI Curses standard, Issue 4, described the soft-key functions,
with some differences from SVr4 curses:
.bP
It added functions like the SVr4
attribute-manipulation functions \fBslk_attron\fP,
\fBslk_attroff\fP, \fBslk_attrset\fP,
but which use \fBattr_t\fP parameters (rather than \fBchtype\fP),
along with a reserved \fIopts\fP parameter.
.IP
Two of these new functions (unlike the SVr4 functions) have no provision
for color: \fBslk_attr_on\fP and \fBslk_attr_off\fP.
.IP
The third function (\fBslk_attr_set\fP) has a color-pair parameter.
.bP
It added \fBconst\fP qualifiers to parameters (unnecessarily), and
.bP
It added \fBslk_color\fP.
.PP
Although \fBslk_start\fP 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):
.bP
\fBslk_start\fP has two parameters:
.RS
.bP
\fIng\fP (number of groups) and
.bP
\fIgp\fP (group pointer).
.RE
.bP
Soft-key groups are an array of \fIng\fP integers.
.bP
In SVr4, \fBslk_init\fP calls \fBslk_start\fP passing a null for \fIgp\fP.
For this case, \fBslk_start\fP uses the number of groups \fIng\fP
(3 for the 3-2-3 layout, 2 for the 4-4 layout) which \fBslk_init\fP provided.
.IP
If \fIng\fP is neither 2 or 3,
\fBslk_start\fP checks the terminfo \fIfln\fP (label_format) capability,
interpreting that as a comma-separated list of numbers,
e.g., \*(``3,2,3\*('' for the 3-2-3 layout.
.IP
Finally, if there is no \fIfln\fP capability, \fBslk_start\fP returns ERR.
.bP
If \fBslk_start\fP is given a non-null \fIgp\fP,
it copies the \fIng\fP elements of the group of soft-keys, up to 16.
.IP
If there are more than 16 elements, \fBslk_start\fP returns an error.
.bP
The format codes \fB2\fP and \fB3\fP for \fBslk_init\fP
were added by ncurses in 1996.
PDCurses 2.4 added this feature in 2001.
.PP
The function \fBslk_attr\fP was added by ncurses in 1996.
.PP
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 \fBshort\fP 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 \fBint\fP parameters,
allowing applications to use larger color- and pair-numbers.
.SH SEE ALSO
\fBcurses\fP(3),
\fBcurs_attr\fP(3),
\fBcurs_initscr\fP(3),
\fBcurs_refresh\fP(3),
\fBcurs_variables\fP(3).