+.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\fR
+returns an error
+if the format parameter is outside the range 0..3.
+.TP 5
+\fBslk_label\fR
+returns \fBNULL\fR 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
+.PP
+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.