+ Functions using a window parameter return an error if it
+ is null.
+
+ <STRONG>wgetn_wstr</STRONG>
+ returns an error if the associated call to
+ <STRONG>wget_wch</STRONG> failed.
+
+ Functions with a "mv" prefix first perform a cursor move-
+ ment using <STRONG>wmove</STRONG>, and return an error if the position is
+ outside the window, or if the window pointer is null.
+