- The XSI Curses standard, Issue 4, describes these func-
- tions. It changes the argument type of the attribute-ma-
- nipulation functions <STRONG>slk_attron</STRONG>, <STRONG>slk_attroff</STRONG>, <STRONG>slk_attrset</STRONG>
- to be <STRONG>attr_t</STRONG>, and adds <STRONG>const</STRONG> qualifiers. The format codes
- <STRONG>2</STRONG> and <STRONG>3</STRONG> for <STRONG>slk_init</STRONG> and the function <STRONG>slk_attr</STRONG> are specif-
- ic to ncurses.
+ The XSI Curses standard, Issue 4, described the soft-key functions,
+ with some differences from SVr4 curses:
+
+ <STRONG>o</STRONG> It added functions like the SVr4 attribute-manipulation functions
+ <STRONG>slk_attron</STRONG>, <STRONG>slk_attroff</STRONG>, <STRONG>slk_attrset</STRONG>, but which use <STRONG>attr_t</STRONG> parame-
+ ters (rather than <STRONG>chtype</STRONG>), along with a reserved <EM>opts</EM> parameter.
+
+ Two of these new functions (unlike the SVr4 functions) have no pro-
+ vision for color: <STRONG>slk_attr_on</STRONG> and <STRONG>slk_attr_off</STRONG>.
+
+ The third function (<STRONG>slk_attr_set</STRONG>) has a color-pair parameter.
+
+ <STRONG>o</STRONG> It added <STRONG>const</STRONG> qualifiers to parameters (unnecessarily), and
+
+ <STRONG>o</STRONG> It added <STRONG>slk_color</STRONG>.
+
+ The format codes <STRONG>2</STRONG> and <STRONG>3</STRONG> for <STRONG>slk_init</STRONG> and the function <STRONG>slk_attr</STRONG> are
+ specific to ncurses.
+
+ 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 <STRONG>short</STRONG>
+ 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
+ <STRONG>short</STRONG> parameters, allowing applications to use larger color- and pair-
+ numbers.