This is failing because addwch now advances the cursor and line wraps as it should so wprintw fails adding a character to the bottom right corner of the window which, since scrollok is false, is correct.
To make the window fills work scrollok needs to be true then add the bottom line first, scroll the window back down and then add the rest of the lines to get the window full of characters.
-------- Original message --------
From: gson%NetBSD.org@localhost
Date: 25/5/19 11:27 pm (GMT+09:30)
To: blymn%netbsd.org@localhost, lib-bug-people%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost, gnats-admin%netbsd.org@localhost, gson%NetBSD.org@localhost, "(Andreas Gustafsson)" <gson%gson.org@localhost>
Subject: Re: lib/54231 (lib/libcurses/t_curses:copywin test regression)
Synopsis: lib/libcurses/t_curses:copywin test regression