-The XSI Curses standard, Issue 4, describes these functions.
-It changes the
-argument type of the attribute-manipulation functions \fBslk_attron\fR,
-\fBslk_attroff\fR, \fBslk_attrset\fR to be \fBattr_t\fR, and adds \fBconst\fR
-qualifiers.
-The format codes \fB2\fR and \fB3\fR for \fBslk_init()\fR and the
-function \fBslk_attr\fR are specific to ncurses.
+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
+The format codes \fB2\fP and \fB3\fP for \fBslk_init\fP and the
+function \fBslk_attr\fP are specific to ncurses.
+.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 \fBshort\fP parameters,
+allowing applications to use larger color- and pair-numbers.