This is the default 17.10 session; the GNOME Shell I mentioned in the original post is the culprit. The problem is that there is NO "blank the screen on inactivity" setting. If I want to lock the session and get the lock screen, there is an option for that. What I do not want to do is have to type my password every time the screen-saver-blanking happens, which is a dozen or more times a day.
@[email protected] under settings, I see "power" where I can set a blank screen in 1-15 minutes, then under "privacy" I can turn screen lock off. Now I just have to leave it alone long enough to test.
Yeah, indeed there is a drop-down selector there that pretends to offer the option. It's not hard to find. The actual functionality is what doesn't work.