+X/Open Curses,
+Issue 4 describes these functions.
+It defines no error conditions.
+.PP
+SVr4 specifies only
+\*(``an integer value other than \fBERR\fP\*('' as a successful return
+value.
+.PP
+SVr4 indicates that the optimization of physically scrolling immediately
+if the scroll region is the entire screen \*(``is\*('' performed,
+not \*(``may be\*('' performed.
+.I \%ncurses
+deliberately does not guarantee that this will occur,
+to leave open the possibility of smarter optimization of multiple scroll
+actions on the next update.
+.PP
+Neither SVr4
+.I curses
+nor X/Open Curses specify whether the current attribute or current color
+pair of blanks generated by the scroll function are zeroed.
+.I \%ncurses
+does so.