Debian :: Where Does Gdm3 Get Its Default DPMS Timeouts

There's a short version at the bottom.

I just installed jessie with gdm3 and use xfce.

I like my monitor to turn off when I'm not at the computer for more than 10 or 20 minutes or so and it wasn't doing that. I haven't used Linux for years and was used to xorg.conf/x11.conf and xinitrc and such.

So I rediscovered xset is responsible for DPMS settings. xset -q revealed DPMS was off. So I used it and put it in ~/.xinitrc. It didn't work. After some canoodling around I found out about xfce's Session and Startup gui thing. I was using that to run ~/.xinitrc.

When I got to my desktop and did a check with xfce4-terminal by running xset -q it would show DPMS enabled but the values were wrong. 600, 0, 900 to be exact.

After some searching I came across the information that xscreensaver will override DPMS settings as it manages DPMS too. So after more canoodling I found out about xfce's Screensaver preferences dialogue and used that to set my values. The values would immediately be set but the problem is that they are not persistent. If I reboot or log out the values will revert to 600, 0, 900. They will only reset to what I want them to be by running xfce's Screensaver preferences dialogue manually.

man gdm3, info gdm3, grep -r DPMS in /etc/gdm3, grep -r dpms in /etc/gdm3 reveal nothing related to DPMS. I've done some searching and nothing useful.

there is an /etc/X11/app-defaults/XScreenSaver-nogl which has some DPMS settings but the times are too large (2 hours); the only thing that matches is the off setting which is specified there.

xscreensaver -no-splash is present in the output of ps so it is xscreensaver and not gnome-screensaver.

The weird thing is that I re-enabled my ~/.xinitrc in xfce's Session and Startup gui thing and it is being run, but the numbers are getting set wrong after it is run. (I put an echo command after xset dpms 900 1200 1500, and the file is appearing in ~)

Where does 600, 0, 900 come from? Mystified on how to proceed from here. I don't remember enough on how to see what's doing what. Is there some sys thing or proc thing I can monitor to find out what's setting these values?

Short version: my xset dpms values are getting reset to 600, 0, 900 every time I logout or reboot. They revert to 600, 0, 900 every time I get to my desktop. I use gdm3 and xfce. Where are these coming from?