David C. Rankin composed on 2019-01-22 00:27 (UTC-0600):

Felix Miata wrote:

...

TCC -> System Administration -> Monitor & Display has nothing enabled. Thus I would expect no attempt from TDE to save power. Is this not the case? After 10 minutes, the screen blanks for several seconds, after which the desktop wallpaper reappears, but not the panel or open Windows. This happens whether the session is started from TDM or with startx. I see nothing in /etc/X11 to account for this, though I'm not sure what I would be looking for other than an Option "DPMS" statement in xorg.conf*. Is this to be expected? Should I file a TDE bug?

Hard to tell, will have to let Slavek and folks chime in, but recall several distros removed default console blanking (which shouldn't be implicated with TDM running, but may), but with startx, you may have DPMS configured. You can check with

$ xset q

I don't know what 18.04 does, but you may poke around and determine just what is set and what isn't. Handy reference:

https://wiki.archlinux.org/index.php/Display_Power_Management_Signaling

Turns out I had a serious brain fart. One cannot expect TDE to exert control over screen power without checking the first box. For years I've been setting power management here to 120 minutes for all three save modes and not having to think about the screen going blank while I'm looking at it while otherwise occupied. I first tried xset q on the PC with the schizoid greeter window, and got:

Screen Saver: prefer blanking: yes allow exposures: no timeout: 0 cycle: 600 DPMS (Energy Star): Standby: 7200 Suspend: 7200 Off: 7200 DPMS is Enabled Monitor is On

Then I tried it on the subject of this thread, and matched the archlinux page:

Screen Saver: prefer blanking: yes allow exposures: yes timeout: 600 cycle: 600 DPMS (Energy Star): Standby: 600 Suspend: 600 Off: 600 DPMS is Enabled Monitor is On

After logging out and back in and puzzling briefly over why only the timeout increased after my KControl change, I realized I must have failed to do the other thing I've been doing for many moons, copying a config file into /etc/X11/xorg.conf.d/ containing:

Option "BlankTime" "120"

I found I did, made the copy, logged out, logged back in, but xset q did not change, which is my new puzzle, because the problem persists. The KControl blank time of 120 is not preventing the several second blanking after 600 seconds, or allowing the panel and open windows to reappear afterward.

(on your last post, TDM should always put your login on Display 1. I've had a 1920x1200 + 1680x1152 setup for years with an ancient nvida card and never had an issue -- setup through nview. ATI should have a similar setup through catalyst control panel. Now on monitor sleep/suspend, depending where the focus is when the monitors go to sleep, I've had kscreensaver put the password prompt on different monitors)

I do all my display other than power save/screen saver via either xrandr startup script, or xorg.conf*. I stick to FOSS, so wouldn't know what NVidia's or AMD's screen controllers look like or can do. When I want the screen to sleep, I turn off the screen power. There's no suspending either, since everything here is multiboot.