- returns an error if the terminal or the softkeys
- were not initialized, or the <EM>labnum</EM> parameter is
- outside the range of label counts, or if the for-
- mat parameter is outside the range 0..2, or if
- memory for the labels cannot be allocated.
+ returns an error if the terminal or the softkeys were not ini-
+ tialized, or the <EM>labnum</EM> 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.
+
+
+</PRE><H2><a name="h2-EXTENSIONS">EXTENSIONS</a></H2><PRE>
+ X/Open Curses documents the <EM>opts</EM> 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.
+
+ For functions which modify the color, e.g., <STRONG>slk_attr_set</STRONG>, if <EM>opts</EM> is
+ set it is treated as a pointer to <STRONG>int</STRONG>, and used to set the color
+ pair instead of the <STRONG>short</STRONG> pair parameter.