+ X/Open defines no error conditions.
+
+ In this implementation, these functions return an error if
+ the window pointer is null, or if its timeout expires
+ without having any data.
+
+ This implementation provides an extension as well. If a
+ SIGWINCH interrupts the function, it will return <STRONG>KEY_RE-</STRONG>
+ <STRONG>SIZE</STRONG> rather than <STRONG>OK</STRONG> or <STRONG>ERR</STRONG>.
+
+ 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.
+