A few days ago, I changed my machine and upgraded to Ubuntu 9.10 (Karmic Koala) and everything went fine, except for the screen-saver that would activate properly but not switch the screen into sleep mode after a while. I found a couple of fixes because despite being a documented bug, there’s not definitive fixes yet.
bash -c "sleep 2 ; xset dpms force off"
Assuming your drivers are working properly—aside from the screen-saver problem, that is—this will wait 2 seconds (so you have time to let go of the mouse) before pushing X into DPMS power save mode, without starting the screen-saver effects. It’s somewhat brutal, but it’s effective. The command instructs Bash that its argument is a series of commands
The second way is, reportedly, to invoke gnome-screensaver-command -a, but that didn’t do anything for me. It does launch the screen-saver, but DPMS never kicks in.
The third way (which seems to fix the problem correctly) is to set the values for the timeouts using gconf-editor. The only key we’re interested in is /apps/gnome-power-manager/timeout/sleep_display_ac. The Koala version of the power policies dialog offers yet again even less configuration options. Instead of a glider, you now find a drop menu where you have choices like 10, never, and that’s about it. If you set your screen saver to launch 10 minutes after the computer became idle and have DPMS to launch also 10 minutes after, only the screensaver launches. Editing the key to read, say, 660 (11 minutes) will (for some reason) make the screensaver launch for a minute, then put the screen into DPMS sleep mode one minute later.
I don’t understand how this fixes my problem, but it did. Maybe both expect the same signal but the screen-saver catches it first? No idea. But, you know, it works now.
If you want to make a custom launcher, I think a moon-themed icon is apropos. Here’s a couple made out of the image at the top of the post (and, accordingly, complies with the GFDL). Just click on them then use ‘save image as’ or whatever it is your browser supports ☺