+ X/Open defines no error conditions. In this implementa-
+ tion
+
+ <STRONG>slk_attr</STRONG>
+ returns the attribute used for the soft keys.
+
+ <STRONG>slk_attroff</STRONG>, <STRONG>slk_attron</STRONG>, <STRONG>slk_clear</STRONG>,
+ <STRONG>slk_noutrefresh</STRONG>, <STRONG>slk_refresh</STRONG>, <STRONG>slk_touch</STRONG>
+ return an error if the terminal or the soft-
+ keys were not initialized.
+
+ <STRONG>slk_attrset</STRONG>
+ returns an error if the terminal or the soft-
+ keys were not initialized.
+
+ <STRONG>slk_attr_set</STRONG>
+ returns an error if the terminal or the soft-
+ keys were not initialized, or the color pair
+ is outside the range 0..COLOR_PAIRS-1, or opts
+ is not null.
+
+ <STRONG>slk_color</STRONG>
+ returns an error if the terminal or the soft-
+ keys were not initialized, or the color pair
+ is outside the range 0..COLOR_PAIRS-1.
+
+ <STRONG>slk_init</STRONG>
+ returns an error if the format parameter is
+ outside the range 0..3.
+
+ <STRONG>slk_label</STRONG>
+ returns <STRONG>NULL</STRONG> on error.
+
+ <STRONG>slk_set</STRONG>
+ returns an error if the terminal or the soft-
+ keys were not initialized, or the <EM>labnum</EM> pa-
+ rameter 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.