Solution for Gnome 3 screen blanking

[Andrew Wood <andrew@perpetualmotion.co.uk>]

After much experimenting and hair pulling I thought Id share my solution 
for disabling the screen blanking on Gnome 3.

There are various solutions on the web but this is the only one Ive 
found which always works every boot and keeps working after upgrades.

Basically it consists of a Python script which is lauched automatically 
at login.

Id like to credit a website here which gave me the key idea but 
unfortunately I can no longer find it.

Basically you need to use DBus to request the screensaver be inhibited, 
BUT,

Catch 1 is, the inhibit only applies as long as the process which 
requested it is still running. Therefore its no good using the dbus 
commands in a shell script as each command runs as a separate process 
and terminates, therefore you need to write your own program which will 
request a DBus inhibit then sleep rather than exiting. Python provides a 
nice easy portable solution akin to a shell script.

Catch 2 is that the screensaver daemon must be running BEFORE you call 
inhibit

Catch 3 is that although the screensaver daemon runs automatically when 
you log in, if you then run your Python script manually from the 
terminal it will work, but if you set your Python script to also run 
automantically at login, then, due to the scheduling order, you cannot 
guarantee it will always request the inhibit until after the daemon has 
started. Therefore you need to make it loop so it periodically requests 
an inhibit, this way if the daemon wasnt running the first time through 
the loop it will be later on. This also makes it robust if the 
screensaver daemon should restart for whatever reason. How long you 
sleep for is a tradeoff - too little and you waste processor cycles, too 
long and the screensaver timer will kick in before youve inhibited it. 
30 seconds is a good value guaranteed to always work as the minimum time 
setting in System Settings is 1 min, but you can adjust this upwards if 
you have the screen saver time set higher in System Settings.

The code for the script follows at the end.

To run it you need to open gnome-session-properties from the terminal 
and add an entry for the Python script and also make sure the Gnome 
screensaver daemon is enabled. If like me, as an earlier attempt at 
disabling the screensaver you disabled the daemon, you MUST re-enable 
it, in order for the inhibit request to work -  the entry is called 
'Screensaver' with the description 'Launch screensaver and locker program'

Ive had this running on a public touchscreen terminal for months 
flawlessly, accross dozens of reboots and it survied the upgrade from 
Gnome 3.2 to 3.4

Hope its of some help to others.

Andrew

===========
Python code
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import dbus
import os
import time


while True:
    time.sleep(30)
    bus = dbus.SessionBus()
    proxy = 
bus.get_object('org.gnome.SessionManager','/org/gnome/SessionManager')
proxy.Inhibit("something",dbus.UInt32(0),"inhibiting",dbus.UInt32(8))
    os.system("xset -dpms")



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