+.PP
+X/Open does not define any error conditions.
+This implementation returns an error
+if the window pointer is null or
+if the string pointer is null or
+if the corresponding calls to \fBwaddch\fP return an error.
+.PP
+Functions with a "mv" prefix first perform a cursor movement using
+\fBwmove\fP, and return an error if the position is outside the window,
+or if the window pointer is null.