Inhibit Screensaver During Video Playback

[Torsten Grote]

Hi,

I am using Qubes 3.2 with XFCE. When playing videos with mplayer or VLC
in an AppVM, the screensaver in dom0 is not inhibited which is pretty
annoying especially during long movies.

Is this supposed to work or just an issue with my setup? If this is not
supposed to work, how can we make it work?

Kind Regards,
Torsten

[Marek Marczykowski-Górecki]

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No, VM have no way to inhibit screenlocker, which may be seen as a
feature.
Simple solution is to disable screensaver manually before playing the
video...
Some more convenient would be to create a qrexec service, which VM could
trigger to disable screensaver. But this will be surely more work.

- --
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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[Torsten Grote]

Hi Marek,

thanks for your quick response!

On 08/08/2016 04:04 PM, Marek Marczykowski-Górecki wrote:
> No, VM have no way to inhibit screenlocker,

That is good to know at least.

> which may be seen as a feature.

Indeed, if people relied on their screen to lock automatically and then
some compromised VM disabled the screen locking while an attacker waited
for the user to be away and then gained physical access to the computer,
this would be quite bad.

However, it would be nice if there would be a way to allow specific VMs
to still do this like it is with fullscreen windows or keyboard input.

> Simple solution is to disable screensaver manually before playing the
> video...

Of course. I was hoping this wouldn't be necessary :(

> Some more convenient would be to create a qrexec service, which VM could
> trigger to disable screensaver. But this will be surely more work.

I guess that would need to hook into whatever inhibition method the
various players are using (heartbeat, fake keys, etc.). Or is it just a
question of passing a call to xdg-screensaver to dom0 via qrexec instead?

Kind Regards,
Torsten

[Marek Marczykowski-Górecki]

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Something like this. But it needs to be done careful, to really allow
only this particular action. Also dom0 sees different window IDs than
VMs (but you can get VM window ID from _QUBES_VMWINDOWID window property
in dom0). Probably it would be good to check also if that window really
belongs to the calling VM.

Another thing is to convenience your video player to actually call this
service - something that will listen for X screen saver suspend/resume
calls and run appropriate qrexec service.

- --
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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[pixel fairy]

why not just make it a simple action, like leave the mouse in the upper left corner or hot key + button in the notification window that could look like [screensaver: disabled]

then theres no worry about the app. a timer could be good here too, like disable for 1hr if thats how long the movie is.

this might be hard, but the thought just came to me. if an app is playing fullscreen and doesnt receive input, the "screensaver" could simply disable input and pop into a password entry when a cat proof input is received (ctrl+alt+del for example) the host windowing system could then be used to verify that this is not a trick or your not just watching that famous scene where someone is using qubes-os!

[pixel fairy]

of course youd have to be carefull that no sensitive data or notifications follow that movie. move vm (or disp vm) only!