+.PP
+X/Open defines no error conditions.
+In this implementation
+.RS
+.TP 5
+\fBdelwin\fR
+returns an error if the window pointer is null, or
+if the window is the parent of another window.
+.IP
+This implementation also maintains a list of windows,
+and checks that the pointer passed to \fBdelwin\fP is one that
+it created, returning an error if it was not..
+.TP 5
+\fBmvderwin\fP
+returns an error
+if the window pointer is null, or
+if some part of the window would be placed off-screen.
+.TP 5
+\fBmvwin\fP
+returns an error
+if the window pointer is null, or
+if the window is really a pad, or
+if some part of the window would be placed off-screen.
+.TP 5
+\fBsyncok\fP
+returns an error
+if the window pointer is null.
+.RE